U1 O3 - Emergency diagnostics Flashcards
What is the normal PCV for cats and dogs?
Normal dogs have a PCV of 37-55% and cats 30-45%.
What are reticulocytes?
Reticulocytes are immature, non-nucleated red blood cells that are found in the circulation in increased numbers in regenerative responses.
What is the mean cell volume (MCV) in haematology?
➢ Mean cell (corpuscular) volume (MCV) The mean cell volume provides information about the average size of red blood cells. Cells may be: • macrocytic (bigger than normal), • normocytic (normal size) • microcytic (smaller than normal).
Why would a patient have large circulating erythrocytes?
RBCs become smaller as they develop in the bone marrow- so if immature are released early into the bloodstream e.g. following haemorrhage, they will be relatively large. In regenerative anaemia, immature cells are often released into the circulation and are relatively larger than mature erythrocytes.
Why would a patient have small circulating erythrocytes?
If a patient, has iron deficiency anaemia, the circulating red blood cells are smaller than normal as they have spent longer developing in the bone marrow, due to the lack of iron.
What us the mean cell haemoglobin concentration (MCHC) in haemoatology?
➢ Mean cell (corpuscular) haemoglobin concentration (MCHC)
This is a measurement of the average haemoglobin concentration per red blood cell. Depending on the haemoglobin levels in RBCs, they will be
• normochromic (normal colour = normal haemoglobin concentration)
• hypochromic (paler than normal = reduced haemoglobin).
Immature RBCs contain less haemoglobin- thus regenerative anaemia will usually be hypochromic; whereas non-regenerative anaemia will be normochromic.
What is a white blood cell count made up of?
The white blood cell count is made up of neutrophils, lymphocytes, eosinophils and basophils.
What can a leucogram assist with identifying?
The character of the leucogram (i.e. what combination of white cells is present) can assist in identifying an underlying cause e.g. stress leucogram, inflammatory leucogram etc.
What is an increase in neutrophils usually associated with?
Explain what a left shift is and what a degenerative left shift is?
Neutrophils: an increase in the number of neutrophils is most commonly associated with infection or inflammation. Immature neutrophils are called band cells - an increase in the number of immature neutrophils in the circulation is known as ‘a left shift’. This is seen where neutrophils are involved in an active inflammatory or infectious process; or where there is abnormal neutrophil production. In a normal regenerative response, the number of mature neutrophils will outnumber the band neutrophils- indicating that the immune response is working well. However, if band neutrophils outnumber the mature neutrophils, this indicates that the mature neutrophils are being consumed/destroyed- the immune response is not working as well as we would like or is being overwhelmed. This is called a degenerative left shift.
What is lymphopaenia? and what is it associated with?
Lymphopaenia (decreased circulating lymphocyte numbers) can be seen in association with acute infection or chronic stress e.g. chronic disease or corticosteroid therapy etc. Lymphocytosis (increased numbers of circulating lymphocytes) can be seen with hypoadrenocorticism, leukaemia or prolonged antigenic stimulation. It may also be seen with an acute stress response.
What are lymphocytes T and B associated with?
Lymphocytes (T and B lymphocytes) are associated with the immune response.
What are eosinophils associated with?
Eosinophils are present in relatively small numbers. They are associated with allergic disease and parasitism. Increased numbers may also be seen with specific conditions such as pulmonary infiltration with eosinophilia (PIE) or neoplasia. Eosinopaenia may be a stress response or secondary to corticosteroid treatment.
How common are basophil abnormalities?
Basophils abnormalities in basophil numbers are rarely identified.
What do monocytes develop in to? and what are large number associated with?
Monocytes these large cells are only present in blood for a short time before leaving and developing into macrophages. Increased numbers can be associated with chronic, intracellular infections or a stress response
What is haemostasis?
Haemostasis is the process of stopping bleeding
How can haemostasis occur?
- vasoconstriction
- primary haemostasis - formation of an initial platelet plug
- secondary haemostasis/ clot formation - the platelet plug is stabilised by cross-linked fibrin- clot
- thrombolysis- clot break-down.
What can happen to platelets when a patient is thrombocytopaenic?
thrombocytopaenia can arise due to:
• Increased platelet destruction e.g. immune-mediated thrombocytopaenia (IMHA)
• Increased platelet ‘consumption’: platelets have been used up secondary to haemorrhage or inflammation.
What is primary haemostasis?
Primary Haemostasis
Platelets are required for primary haemostasis (the start of clot formation). Alterations in the platelet numbers occur for many reasons and with various diseases.
What is the monolayer segment of a smear and what is it composed of?
Oil immersion fields are examined in the monolayer segment of the smear. The monolayer segment lies between the feathered edge of the smear and the main body of the smear - it is composed of a single layer of cells.
How many platelets should be seen per field on average on a normal blood smear? What would be considered as dangerously low level of platelets?
Each one platelet, seen in an oil immersion (x100) field, is roughly equivalent to 15x109 platelets/l. Therefore, a normal blood smear should have 11-15 platelets per field on average. Dangerously low levels of platelets would be indicated by less than 3 platelets per oil immersion field (equivalent to 0-45x109/l). A patient with a platelet count of <5 per field should be closely monitored for evidence of bleeding.
What equipment would you need to carry out a true platelet count?
A true platelet count may be done, manually, using a haemocytometer, commercial diluting fluid and a microscope
How do you carry out a true platelet count?
A commercial ammonium oxalate diluent pipette system should be used (e.g. ‘Unopette Micro-collection System for WBC and Platelet Determination’ produced by Becton-Dickinson, Oxford UK). This is filled as directed and lyses the red cells after ~ 10 minutes. A Neubauer modified haemocytometer is then filled with the mixture and left in a humid environment (a small covered dish with a layer of wet filter paper in the bottom) for 5-10 minutes, to allow the platelets to settle to the floor of the haemocytometer.
A platelet count is then performed by examining the haemocytometer microscopically. Platelets can be differentiated from white cells by their smaller size and refractile nature. The total number of platelets, in the central major square on each side of the haemocytometer, is counted. This square is divided into 25 smaller squares, each of which contains 16 further squares. The average of the two major square counts is then the total platelet count in 109/l. Normal values for dogs are 200-700x109/l and for cats are 300-800 x109/l.
Clinically what is the best way to perform platelet function assessment?
Platelet function can be assessed in a laboratory using specific analysers. Clinically, however, the best way is to perform a buccal mucosal bleeding time (BMBT).
How do you carry out a Buccal mucosal bleeding time test?
Buccal mucosal bleeding time - The BMBT requires the use of a commercial device that produces two standardised cuts to the buccal mucosa of the upper lip - 5mm long and 1mm deep. The patient is placed in lateral recumbency, the upper lip is reflected to expose the mucosal surface and held in place by a gauze tape lightly applied around the maxilla, enough to partially block venous return (Oakley, 2007). The BMBT device is then placed on the mucosa and activated. The incisions are then left alone until bleeding stops- the time taken should be recorded. This is assessed by using a swab or filter paper placed near to the incisions (3-4 mm below), but not touching them. Bleeding is judged to have stopped when blood stops being taken up by the clean edge of the swab/filter paper. The BMBT is taken as the mean bleeding time of the two incisions and should normally be less than 4 minutes. The BMBT evaluates primary haemostasis by assessing platelet and vascular aspects of haemostasis.
In what case would you see an increased Buccal mucosal bleeding time?
What are the contraindications?
Instances where BMBT may be increased include:
• thrombocytopaenia
• von Willebrand’s disease
• drug therapy e.g. aspirin.
A BMBT should NOT be performed on dogs that are already known to be thrombocytopaenic- thrombocytopaenia should be confirmed initially on a blood smear, as previously discussed. Thrombocytopaenic animals will have a prolonged BMBT so confirmation with the test is unnecessary.
What is secondary haemostasis?
Secondary Haemostasis
Secondary haemostasis is the process of clot formation using coagulation factors - it follows the formation of an initial platelet plug (Cornell University College of Veterinary Medicine, 2013). It can therefore be affected by deficiency in any clotting factor. These deficiencies may arise from a lack of production (e.g. vitamin K deficiency or haemophiliacs); or consumption of the coagulation factors (e.g. sepsis or trauma).
What is activated partial thromboplastin time (aPTT)?
Activated partial thromboplastin time (aPTT)
This assesses the function of both the intrinsic and common pathways. Activated partial thromboplastin time (aPTT) is measured from blood collected into a citrated plasma tube. The tube MUST be accurately filled as the results will be inaccurate otherwise.
What is prothrombin time (PT)?
Prothrombin time (PT) This identifies deficiencies in the extrinsic (factor VII) and common pathways (fibrinogen, II, V and X). It measures the time for fibrin to be produced after activation of factor VII, then factors X, V and II (prothrombin). Tissue factor and calcium are added to a citrated plasma tube, containing a blood sample, to activate. The tube MUST be accurately filled as an inaccurate result will be obtained otherwise. Fibrin formation, from fibrinogen, is the end point of the assay - this can also be measured using optical or mechanical means.
What percentage of deficiency does aPTT require to produce prolongation of the PT?
As with aPTT, deficiencies of less than 30% are required to produce prolongation of the PT. Factor VII has the shortest half-life of the clotting factors, so PT maybe increased before aPTT in a patient with a coagulopathy.
What effects will rodenticide poisoning have on coagulation factors?
Acquired vitamin K deficiency (rodenticide poisoning) is an example of a condition that can prolong PT. Whilst eventually both PT and APTT will increase, PT will become elevated first-normally within 48-72hrs of ingestion of the rodenticide.
How is activated clotting time measured?
Activated clotting time.
Activated clotting time is measured by taking a blood sample, then discarding the first 0.25-0.5 ml of it. This removes the tissue factor which could otherwise complicate the test. 2ml of the blood sample is put into a tube containing diatomaceous earth (produced by Becton-Dickinson, Oxford). After mixing, the tube is incubated at 37°C for 60 seconds in the dog; and 45 seconds in the cat. After thisthe tube is gently tilted, at 10 second intervals, to determine if a clot has formed. Normal ACT for dogs is 60-110 seconds and for cats is 50-75 seconds.
An in-house test-kit is also available for measuring activated clotting time (ACT).
Sampling technique is important when considering coagulation profiles. Samples should be from a “clean stick”, with minimal dwell time in the vessel and they should be non-haemolysed. Other patient specific factors considerations need to be considered (e.g. a patient with a coagulopathy should not have jugular blood samples taken)
How do you carry out a slide agglutination test?
Slide Agglutination (also called saline dispersion test) A saline dispersion test should be performed to determine if there is true agglutination in a blood sample. N.B. Agglutination can arise with immune-mediated haemolytic anaemia when antibody covered RBCs stick together. In this test, a drop of blood from an EDTA blood tube or capillary tube is put onto a slide- it is assessed for the presence of agglutination (development of obvious flecks within the drop of blood). If agglutination appears to be present, three drops of saline are added to the blood on the slide. This will cause dispersal of RBCs if rouleaux (stacking of RBCS) rather than agglutination was present- the flecks will disappear with rouleaux. If true autoagglutination has occurred, the flecks will still be seen as the RBCs remain stuck together. Autoagglutination is caused by cross-linking of antibodies which are bound to the erythrocyte membranes - this is diagnostic for an immune-mediated component to the haemolysis. It is important to remember that the saline does not induce the agglutination – it merely confirms that it is true agglutination.
What is a coombs test?
Coombs Test
A Direct Antiglobulin Test looking for the auto-immune antibodies that are directed against the red cells (Coombs) can be used to confirm immune mediated haemolytic anaemia. Because the end (positive) result of this test is agglutination, the Coombs test need not be run if the patient is already auto-agglutinating. Blood should be taken for this assay prior to transfusion.
What is a POCUS?
Point of Care Ultrasound
What is the abbreviation FAST?
Focused assessment sonogram for trauma
What is a TFAST?
Thoracic Focused Assessment with Sonography for Trauma
What is an AFAST?
Abdominal Focused Assessment with Sonography for
Trauma
What is the abbreviation COP?
Colloid osmotic pressure
What does an emergency database test include?
• the minimum database
1.3.3.1 Minimum Database
A minimum database consists of the following:
• Packed cell volume (PCV)
• Refractometric total solids (TS) or total protein (TP) **
• Blood glucose (BG)
• Blood urea (BUN)
- blood smear
- electrolytes
- blood gases
- urine specific gravity.
What does a minimum database include?
1.3.3.1 Minimum Database
A minimum database consists of the following:
• Packed cell volume (PCV)
• Refractometric total solids (TS) or total protein (TP) **
• Blood glucose (BG)
• Blood urea (BUN)
• Blood smear
How much blood is required for a minimum database?
The volume of blood required for this database is small (~ 0.2ml depending on
equipment used) and can be collected from the hub of an intravenous catheter at the
time of placement (if the catheter was not flushed with heparinised saline prior to
placement)
Why is it best to get a small amount of blood from the hub of the catheter initially in an emergency situation?
Separate venepuncture to collect blood for a MDB should not be
necessary- merely adding to the patient morbidity. During catheter placement blood
can also be collected for additional laboratory tests such as electrolytes/ venous
blood gases (N.B. arterial blood gas analysis would require placement of an arterial
catheter)
What is the difference between total solids and total protein?
Total solids (TS) versus total protein (TP) - these terms are often used interchangeably but are not quite the same. Total solids (TS) refer to everything
dissolved in plasma (plasma proteins, urea, triglycerides, cholesterol and glucose),
while total protein literally refers to the main plasma proteins (primarily albumin and
globulins).
What does the term total solids refer to?
Total solids (TS) refer to everything dissolved in plasma (plasma proteins, urea, triglycerides, cholesterol and glucose),
What does the term total protein refer to?
total protein literally refers to the main plasma proteins (primarily albumin and
globulins).
Is a refractometer calibrated to give a total protein or total solids measurement?
The value for TP should therefore be slightly lower than TS. Most refractometers have been calibrated to give a TP measurement which is, in fact, the
TS minus a small factor.
What breed and age specifics may cause a variation in PCV?
There are some breed and age specifics where PCV will be higher or lower
(greyhounds/ sighthounds/paediatric patients)
What does a refractometric total solids estimate?
Refractometric TS allows estimation of serum proteins and a rough estimation
of colloid osmotic pressure (COP)
what does a PCV determine?
PCV is used to determine if a patient is anaemic or polycythaemic.
What is an increase in both PCV and TP consistent with?
An increase in both PCV and TS is consistent with dehydration- although this
may only be apparent with severe dehydration. A normal PCV/ TS could be
present in a slightly dehydrated patient
What may an increase in PCV and normal TP be consistent with?
An increase in PCV alone could be normal for the breed e.g. greyhound. It
could be due to polycythaemia, but it could also be stress-induced
(adrenaline/ epinephrine) splenic contraction
What might a decreased PCV and TP be consistent with?
Decreased PCV and TS will often arise following haemorrhage or after aggressive fluid therapy
Why might a PCV/TP be normal in an acute haemorrhage?
A decrease in both PCV and TS is not usually seen during/immediately following haemorrhage. During acute, active haemorrhage, whilst the total blood volume will be decreased, the PCV and TS may be normal because there has
not yet been any fluid shift from the interstitial space to intravascular space (blood vessels). Soon there will be fluid movement from the interstitial space
to the intravascular space causing dilution of the TS; the PCV is likely to be maintained near normal, initially, due to splenic contraction which releases
more erythrocytes to improve oxygen delivering capacity. Therefore, if an animal is presented in shock with a low TS yet normal PCV, haemorrhage is the likely condition needing to be ruled-out. If the haemorrhage continues, both the PCV and TS are likely to decrease.
What might a low TP and normal PCV be consistent with?
Low TS may also arise with a normal PCV if there has been protein loss/decreased production: (Hypoalbinaemia) primarily albumin (Mackin, 2010). This loss may be through the kidneys, GI tract or from the vasculature into a body cavity (thirdspacing) secondary to inflammation (e.g. peritonitis). Failure to produce can be associated with chronic liver disease or malnutrition.
What might a low TP and low PCV be consistent with?
Normal TS with a low PCV is consistent with enhanced erythrocyte destruction or a non-regenerative anaemia (Haemorrage, anaemia and hypoproteinamia)
What might a normal PCV and increased PCV be consistent with?
Hyperglobinaemia
artifactual
What might a low PCV and normal TP be consistent with?
(Chronic anaemia and haemolytic anaemia)
What may be the common cause of hypoglycaemia in an emergency patient?
Pediatric patients Septic patients insulin secreting tumour Hypoadrenocorticism exercise induce (working dogs)
What may be the common cause of hyperglycaemia in an emergency patient?
diabetes mellitus
stress reponse (cats)
In dogs, hyperglycaemia can be associated with head trauma and seizures- it
is a poor prognostic indicator
Patients with severe hypovolaemia or hypoxaemia may have hyperglycaemia
due to the sympatho-adrenal response. However, depending on the individual
patient it is possible they could be hypoglycaemic e.g., severe liver disease
preventing gluconeogenesis
What is azotaemia?
Azotaemia is when there are increased nitrogenous compounds in the
blood stream e.g. urea and creatinine
What is a BUN test used to screen?
Blood urea nitrogen (BUN) can be used as a screening test to identify azotaemic
animals
What should you do if you get a very high BUN reading on a dipstick?
A low BUN result on a dipstick is considered
accurate, but a high value should be supported with additional laboratory tests.
What secondary causes may cause an increase in BUN?
BUN
may be elevated secondary to a pre-renal, renal or post-renal cause e.g.,
dehydration, renal disease or urethral obstruction
What information does a blood smear provide?
A blood smear provides vital information on the number and morphology of cells within blood. A blood smear should always be performed (and interpreted) if a haemotology profile is performed.
What cells can be evaluated on a blood smear?
Erythrocytes, leukocytes and platelets should be evaluated - with attention
paid to both the number and the cell morphology.
Where can cellular morphology be viewed on a blood smear?
Cellular morphology should be viewed in the monolayer.
What might the presence of immature neutrophils indicate on a blood smear?
The presence of immature neutrophils (band cells) should be noted- this can
indicate a severe inflammatory or infectious condition
What changes in leukocytes may be seen on a blood smear if a patient has SIRS or sepsis?
In a patient with SIRS (septic or non-septic), leucocytosis may be present typically with a left shift (immature/ band neutrophils) and toxic changes to the neutrophils (eClinpath, 2013). Leucocytosis and mature neutrophilia can be part of a stress leukogram
Septic patients may also be leucopaenic because of sequestration of white
blood cells at the site of the infection (e.g. pyometra). Leucopaenia can also
be present with viral infections e.g. parvovirus
What toxic changes may be seen in neutrophils on a blood smear?
Toxic changes that can be seen include-
➢ blue granules/ foamy appearance of the cytoplasm
➢ swelling of the nucleus
➢ Dohle bodies (light blue-grey, oval, inclusions in the peripheral cytoplasm)
How do toxic neutrophils occur?
Toxic neutrophils occur when the condition intensely stimulates neutrophil
production, with decreased maturation time in the bone marrow.
What cases might you see a moderately decreased number of platelets?
The platelet count may be moderately decreased in bleeding or septic
patients, secondary to consumption; or severely decreased and the actual
cause of hypovolaemic (haemorrhagic) shock in a patient with blood loss.
What does reducing levels of platelets on a blood smear indicate in a critically ill patient?
Reducing levels of platelets in a critically ill patient can indicate that they are developing disseminated intra-vascular coagulation (DIC). Thrombocytopaenia is one of the earliest indicators of DIC.
How many platelets should be seen per high power field in the monolayer?
• In healthy patients, under oil immersion (x100) microscopic examination, there
should be 11-15 platelets per high power field (h.p.f.) in the monolayer. This
is equivalent to a platelet count of ~ 165 - 225 x109platelets/l. Each platelet
viewed, per h.p.f., equates to 15 x 109
/ l in the bloodstream.
What number of platelets per high power field would be a cause for concern and should be monitored for evidence of bleeding?
A patient with a platelet count of <5 per high power field should be closely
monitored for evidence of bleeding
What number of platelets per high power field would be a cause for concern and intervention would be indicated?
Less than 3 platelets per high power field (equivalent to equivalent to 0-
45x109
/L) is a dangerously low levels of platelets. Intervention would be
indicated.
How can you detect reticulocytes on a blood smear?
If the blood smear is stained with new methylene blue, then reticulocytes
are demonstrated- they have a fine trabecular structure within the cells
(made up of nuclear material and cellular organelles). In cats,
reticulocytes may appear with punctuate dots/ clusters and lines of
condensed organelles. These start out as the aggregate form (clusters
and lines) and mature to the punctuate dots. Therefore, large numbers of
the aggregate form of reticulocyte in cats demonstrates active
regeneration
When might nucleated red cells be seen on a blood smear?
Nucleated red cell may be seen with a strongly regenerative response
Nucleated RBCs may also be seen in cases of splenic disease,
myelodysplastic conditions and lead intoxication
What will be seen on a blood smear from a dog with immune-mediated haemolytic anaemia?
In dogs with immune-mediated haemolytic anaemia, there may be -
Spherocytes- produced when macrophages remove part of the red cell
wall.
Strongly regenerative response
Auto-agglutination
What are schistocytes?
Fragments of red cells (schistocytes)
What might schistocytes on a blood smear be secondary to?
Fragments of red cells (schistocytes) may be secondary to haemangiosarcoma or disseminated intravascular coagulation
What are heinz bodies a result of?
Heinz bodies are the result of oxidative damage
to haemoglobin in red cells- they appear as refractile, poorly staining bodies,
located beneath or protruding from the red cell membrane
What may the presence of heinz bodies on a blood smear suggest?
In cats, the presence of Heinz bodies may suggest intoxication e.g. paracetamol or onion. Heinz bodies may also develop in cats with prolonged
or repeated use of propofol.
In addition, parasites e.g. Mycoplasma haemofelis or Babesia sp. may be present. Mycoplasma haemofelis may be seen as chains, discs or rods on the surface
of erythrocytes. The PCV can decrease rapidly in cats with this condition.
What is the term for too much acid in the body?
Acidosis
What is Acidaemia?
Blood pH < 7.35
What is the term for too much alkali in the body?
Alkalosis
What is Alkalaemia?
Blood pH > 7.45
What can be used to relate the pH
of blood to the bicarbonate buffer system?
Henderson- Hasselbach Equation -
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
What are the main gases in the blood?
The main gases that are present in blood are oxygen (O2) and carbon dioxide (CO2).
What does the partial pressure of oxygen and carbon dioxide represent?
The partial pressure of oxygen and carbon dioxide (PO2 and PCO2) represent the
amount of the gas that is dissolved in blood.
What body systems does blood gas analysis give essential information on?
Blood gas analysis can give essential information on the respiratory and metabolic
status of a patient. It is important to note when considering respiratory status that
arterial blood gases will be more accurate
What part of a blood gas analysis evaluates the acid/base status?
Firstly, the acid/base status can be evaluated by assaying pH, PCO2 and
bicarbonate
What part of a blood gas analysis evaluates the lung function?
Secondly lung function can be assessed by measuring the amount of oxygen
(PaO2) and carbon dioxide (PaCO2) in arterial blood. (N.B. a = arterial; v =
venous)
What type of blood sample is needed for blood gas analysis?
Arterial blood gas analysis (ABG) is preferred when assessing respiratory
status but venous blood gas analysis (VBG) will still yield useful information
regarding metabolic status.
Why is it important to determine the metabolic status of a patient?
Determining the metabolic status of the patient will therefore provide vital clues to aid in the diagnosis of a condition, as well as help in the management/treatment of it.
➢ The presence of acidosis and alkalosis will also determine the type of fluid
and replacement therapies indicated
Why is it important to determine the resiratoy status of a patient?
Analysis of the respiratory component of the blood gas will help in the identification of a specific respiratory condition: as well as guiding therapy/intervention and prognosis. For example, deciding on when to provide
supplemental oxygen. The use of arterial blood gases can help guide oxygen therapy protocols. Whilst oxygen is widely considered to be a benign therapy
there is a risk of hyperoxia and associated complications. Monitoring of the PaO2 allows us to identify when we can reduce FiO2 for individual patients.
N.B. Some figures are measured (e.g. pH) and some are calculated (e.g. BE).
Animals with respiratory fatigue may need ventilation
How is the PH or acidity of the body maintained?
The pH or acidity of the body is maintained within a relatively, narrow range (7.35–
7.45) through expiration of CO2 from the lungs; and the excretion of hydrogen ions
through the kidneys. There are also a series of other buffers such as bicarbonate
which act to keep the pH within narrow limits
What effects can alteration in PH have?
Alterations to pH mean that cells and
metabolic processes are unable to function leading to organ dysfunction, failure and
ultimately death.
What compensatory changes can a variation in PH have?
Any variation in the pH outside of this range will result in compensatory changes such as an increase/decrease in respiratory rate that will
attempt to correct the pH:
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
However, these compensatory changes, whilst maintaining pH, can result in
increased energy and oxygen consumption for the patient.
What component is important for the bodys buffering system?
Bicarbonate is very important
for the body’s ‘buffering’ system.
What is respiratory acidosis?
Plasma CO2 levels increase in animals that are hypoventilating- this is RESPIRATORY ACIDOSIS
↑CO2 + H2O → ↑H2CO3 → ↑H+ + ↑HCO3-
Why would a patient with metabolic acidosis be tachypnoeic?
If a patient has METABOLIC ACIDOSIS e.g. diabetic ketoacidosis or lactic acidosis secondary to anaerobic metabolism, caused by hypovolaemia, it will often be
tachypnoeic (rapid, shallow breathing). The tachypnoea is a compensatory response from the respiratory system to try and rid the body of acid (CO2) to maintain pH. This response results in more CO2 being expired and so more H+ ions binding with
HCO3- to maintain equilibrium. With less H+ in circulation, this compensatory
mechanism should assist the blood pH return to neutral.
↓CO2 + H2O → ↓H2CO3 → ↓H+ + ↓HCO3-
How can a patient develop metabolic alkalosis?
If a patient loses excess acid (hydrogen ions H+) through gastric vomiting or has excess bicarbonate, it will develop a METABOLIC ALKALOSIS - which results in the blood becoming more alkaline.
How can a patient develop respiratory alkalosis?
If a patient hyperventilates and expires too much carbon dioxide, it will develop a RESPIRATORY ALKALOSIS. This can also occur in anaesthetised patients undergoing IPPV or those receiving mechanical ventilation.
What organs are involved in maintaining the correct PH?
The kidneys assist in maintaining the correct pH but their response is not as immediate as that obtained by altered ventilation (Lungs)
Why is important to optimise renal function when a patient is acidaemic?
The kidneys assist in maintaining the correct pH but their response is not as
immediate as that obtained by altered ventilation. The kidney function is also
commonly reduced in emergency patients, especially those that are hypotensive or
hypovolaemic on presentation. As such supportive measures may need to be
considered to optimise renal function.
What are assessed when analysing blood gases?
When performing ABG the following are assessed: • pH • PCO2 • Bicarbonate (HCO3 - and ‘base-excess’)
What does a PaCO2 and PvCO2 assess?
If this an arterial blood sample (preferred) PaCO2, is
assessed; if this is a venous blood sample PvCO2, is assessed. carbon dioxide in blood
What is a respiratory acidosis?
Increased CO2 (PCO2) levels in the blood stream decrease the pH
of blood e.g. it becomes more acidic- acidaemia. As discussed
previously, the cause is ineffective ventilation (hypoventilation). The
animal therefore has a respiratory acidosis.
How does respiratory alkalosis occur?
Decreased CO2 (PCO2) levels in the blood stream increase the pH of blood - alkalaemia e.g. it becomes more alkaline- the cause is hyperventilation. The animal therefore has a respiratory alkalosis.
Is bicarbonate in the body high or low in metabolic alkalosis?
metabolic alkalosis, bicarbonate will be increased.
Is bicarbonate high or low in metabolic acidosis?
In metabolic acidosis, bicarbonate will be decreased (less to mop up H+/
hydrogen ions);
What are the causes for altered bicarbonate levels?
Reasons for altered bicarbonate levels are -
o Metabolic causes e.g. lost in diarrhoea, anorexia
o Respiratory causes e.g. hypoventilation
What type of acid-base abnormality does the concept of the base excess identify?
Because bicarbonate levels can be affected by respiration, the concept of
the base excess (BE) was developed to identify metabolic rather than
respiratory causes of acid-base disorders (
What is the base excess?
The base excess (BE) is a calculated figure which estimates the metabolic (rather than respiratory) component of the acid-base balance
Whilst we commonly evaluate pH, PCO2 and HCO3 to
measure acidosis or alkalosis in the blood we can also evaluate BE to differentiate between the metabolic and respiratory components.
It measures the amount of excessive base (alkali) or acid in blood and so gives information on the metabolic aspect of the acid-base balance.
What does the base excess measure?
It measures the amount of excessive base (alkali) or acid in blood and so gives information on the metabolic aspect of the acid-base balance.
It calculates the amount of strong acid (or alkali - base deficit (BD)) that would theoretically have to be added to blood to neutralise it. The normal
range is - 2→ +2
e.g. if a patient’s blood were alkaline for metabolic reasons, it would have too much base (e.g. increased HCO3). To neutralise the blood, strong acid
would in theory be needed. The more alkaline the blood is the more acid would be required. The amount that is required is the base excess and it
is an indication of how alkaline the blood is e.g. + 4 is less alkaline than +8.
What is a base deficit? What would need to be done to correct this?
If the number is more negative than it should be (e.g. -9) the patient has a base deficit. There is an excess of acid/ or lack of ‘base’/alkali in the bloodstream. This means more alkali/base would have to be added to neutralise blood. This shows that the patient’s blood too acidic= metabolic acidosis (more common)
What is a base excess? What can be done to correct this?
If the number is more positive than it should be (e.g. +12) the patient has a base excess- there is an excess of ‘base’ (alkali)/ or lack of acid in the blood stream meaning more acid would have to be added to neutralise blood. This shows that the patient’s blood is
too alkaline = metabolic alkalosis (less common)
How do the kidneys and lungs assist with the body buffering system and what is the onset of action?
As the body buffering system diagram demonstrates, blood CO2 levels (pCO2) can be altered quickly by altering ventilation (almost instantly). The kidneys are also involved in buffering, but this is a slower mechanism (2-3 days).
What is the anion gap calculation used to determine?
The anion gap calculation is used to determine whether metabolic acidosis is due to:
o An increase in the level of acid in the system e.g. diabetic ketoacidosis, uraemic acids, toxins or lactate;
o A loss of alkali (bicarbonate) e.g., from the kidneys.
What are anions?
Anions are negatively charged particles e.g. Cl- + HCO3 - present in extracellular fluid
(ECF) (remember plasma is also part of the ECF);
What are cations?
cations are positively charged particles present in ECF e.g. Na+ + K+
What is the formula to calculate the anion gap?
Anion gap = (Na+ + K+) – (Cl- + HCO3-
What is the normal anion gap for dogs?
The normal value for the anion gap for dogs is 8-25, i.e. normally
dogs have 8-25 more positive ions than negative ions.
What is the normal anion gap for cats?
The normal value for the anion gap for cats 10-27 i.e. normally cats have 10-27 more positive ions than negative ions.
What does an increase in anion gap in cases of acidosis tell you?
An increase in the anion gap (e.g. 40) in cases of acidosis, tells us that there are more anions (e.g. lactate, ketones. present than normal e.g. diabetic ketoacidosis.
What does a normal anion gap in cases of acidosis tell you?
However, a normal anion gap in a case of acidosis (identified from the BE calculation) tells us that the acidosis is due to a loss of bicarbonate (alkali) rather
than increased acid e.g. diarrhoea
What is a blood lactate an indicator of?
Blood lactate is considered a global indicator of tissue perfusion.
What does blood lactate help to assess?
It can be used to assess tissue oxygenation; response to therapy and as a prognostic indicator.
When is lactic acid generated? What is this secondary to?
Lactic acid is generated during anaerobic metabolism. This is most commonly secondary to decreased tissue perfusion, severe hypoxaemia; or a combination of these.
What is the most common cause of metabolic acidosis in veterinary medicine?
Lactic acidosis is the most common
cause of metabolic acidosis in veterinary medicine.
What is the normal serum lactate concentrations in dogs and what would be considered clinically significant?
Normal serum lactate concentrations in dogs should be < 2.5 mmol/L (range 0.3 – 2.5 mmol/L). Concentrations greater than 2.5 mmol/L are considered clinically significant.
What would be considered an intermediate blood lactate and what level would be considered a high?
Lactate levels of 2.5 – 4 mmol/L are intermediate; lactate levels > 4 mmol/L are considered high.
How can blood lactate help to determine prognosis?
Correlations have been made between lactate levels and likely patient mortality/prognosis (Young, 2012). Generally, the higher the lactate level, the poorer the prognosis. It is, however, more important to
monitor trends in lactate levels - a significant decline in lactate would improve the prognosis whereas increasing lactate levels, in a patient, receiving
treatment would give more cause for concern.
What can increase serum lactate concentration even in animals with adequate perfusion?
Prolonged vessel occlusion, excessive restraint, patient struggling, excessive panting, twitching and tremoring and delays in sample analysis will increase the serum lactate concentration, even in animals with adequate perfusion.
What is the most useful monitoring tool for gauging response to resuscitation in patient with shock?
Lactate is most useful as a monitoring tool for gauging response to resuscitation in patients with shock.
How can lactate levels aid the decision in transfusing an anaemic patient?
Severe anaemia will result in a decreased oxygen delivery to tissues with the generation of lactic acid secondary to anaerobic metabolism. The presence of hyperlactataemia may therefore be utilised to aid in the decision to
transfuse anaemic patients.
What will lactate and glucose levels be on abdominal effusion analysis in a septic patient?
Lactate can also be used to analyse effusions from the abdominal cavity. In septic patients lactate levels will be increased in the effusion and glucose will
be decreased due to anaerobic cellular metabolism taking place.
What is the main role of sodium in the body?
Sodium is the main extracellular cation (Na+) in the body. In addition to being involved in blood pressure control, muscle and nerve function, it is important in maintaining intracellular fluid (ICF) and extracellular fluid (ECF) water distribution and balance
What is the concentration of sodium reflect?
The concentration of sodium reflects water balance; abnormalities in sodium are generally a result of gain or loss of water or sodium
Why does sodium change osmotic gradients?
Sodium can change osmotic gradients within the body leading to shifts of water into or out of cells e.g.
cerebral oedema.
What diseases can hyponatraemia occur in?
Hyponatraemia can occur in disease conditions such as intestinal obstruction (sodium is lost with the vomit), hypoadrenocorticism (sodium is lost from the kidneys) or a gain in free water (e.g. inappropriate use of hypotonic fluids).
How can a animal with an intestinal obstruction become hyponatraemic?
(sodium is lost with the vomit
Why can a patient with hypoadrenocorticism become hyponatraemic?
sodium is lost in the kidneys
What cases is hypernatraemia usually seen?
Hypernatraemia can be seen in salt toxicity (gain in salt); a lack of free water (e.g. cat that has been accidentally locked in a shed for multiple days with no access to water) or because of iatrogenic administration of high sodium substances.
Hypernatraemia can also be seen in disease processes e.g. hyperaldosteronism
How does hypernatraemia affect cells?
causes cell dehydration
How does hyponatraemia affect cells?
hyponatraemia results in cell oedema
What signs can animals with hyper and hyponatraemia develop?
Both conditions can affect neuron function potentially causing serious neurological signs. Whilst sodium is only one of the many electrolytes monitored, it is arguably one of the more important -plasma sodium concentration is the major determinant of
plasma osmolality. Extremely high or low sodium levels must be carefully corrected to avoid neurological signs developing and avoid patient mortality.
What is the main role of chloride in the body?
Chloride (Cl -) is an extracellular anion which, along with sodium, is involved in water balance. Along with bicarbonate, it also has an important
role in acid-base balance
When might hypochloraemia be seen?
hypochloraemia will occur secondary to a high gastrointestinal obstruction (because of loss of hydrochloric acid in vomit). Hypochloraemia is usually associated with metabolic alkalosis. Replacement of the chloride is essential to correct the metabolic
derangement.
When might hyperchloraemia be seen?
Hyperchloraemia may occur in a patient with diarrhoea- as the kidneys retain chloride ion when bicarbonate is lost, there may be metabolic acidosis. Iatrogenic hyperchloraemia may be caused by administration of saline fluids e.g. 0.9% NaCL
(Rahilly, 2012). Chloride concentration may be artefactually increased in patients receiving potassium bromide as an anti-seizure medication
Why does potassium within serum/plasma not accurately reflect the total amount of potassium in the body?
Potassium (K+) is the main intracellular cation. Because most potassium is located
within cells, plasma / serum assessment does not necessarily accurately reflect the
total amount of potassium in the body
What role does potassium play in the body?
Along with sodium, potassium plays an important role in nerve and muscle function
What are plasma levels of potassium dependent on ?
Plasma levels of potassium are dependent on diet, renal function, pH, insulin levels and cell integrity.Most of the body potassium is ingested
What does insulin do to potassium?
Insulin drives potassium into cells
When is hypokalaemia commonly seen?
Hypokalaemia, therefore, can be seen with anorexia,
malnutrition, chronic vomiting or diarrhoea. It can also arise with renal disease due to increased diuresis, following insulin administration or secondary to drug therapy e.g.furosemide.
How can renal function affect potassium level?
Potassium is excreted via the kidneys so decreased renal excretion can cause
hyperkalaemia.
Why is hyperkalaemia an emergency?
High levels of potassium lead to an atrial standstill which can lead to sudden and fatal arrhythmias
What are the most common causes of hyperkalemia?
urethral obstruction, acute renal failure and typical hypoadrenocorticism can all result in
hyperkalaemia.
What can low levcels of potassium lead to?
Low levels of potassium can lead to
severe neurological dysfunction including intractable seizures
Where is most of the calcium held within the body?
most of the body’s calcium is within mineralised bone -
What percentage of calcium is within extracellular fluid?
~ 1% is in the ECF
In what form are calcium ions in blood plasma?
The calcium ions (Ca 2+) in plasma can be:
• free
• bound to other substances e.g. albumin or phosphate (PO4 3−
).
Where is calcium in the body biologically active (involved in heart and muscle contraction)?
Only ‘free’ calcium (in blood plasma) is biologically active
What is ionised calcium?
Only ‘free’ calcium is biologically active (involved in heart and muscle contraction)- this is often referred to as ‘ionised’ calcium.
What is the total level of calcium affected by?
The total level of calcium is affected by pH, vitamin D level, albumin level and diet.
What type of diet are unbalanced in phosphorus and calcium?
There may be issues
with the relative levels of calcium and phosphorus in unbalanced, home-made ‘all
meat’ and ‘raw’ diets
What can blood calcium levels be affected by?
Blood calcium levels can be affected by nutrition, endocrine disease, renal disease
and neoplasia amongst other conditions
What is the most common causes of hypercalcemia? what can this lead to?
Hypercalcaemia can lead to cardiac
dysrhythmias and acute renal failure - the most common cause is neoplasia
. Hypercalcaemia can also be associated with renal failure,
hyperparathyroidism, hypoadrenocorticism and vitamin D toxicity
What is the most common causes of hypocalcemia? what can this lead to?
Causes of hypocalcaemia include eclampsia, pancreatitis, ethylene glycol toxicity and diabetic
ketoacidosis. Hypocalcaemia can result in muscle tremors, tachycardia, seizures and
tetany.
Where is most phosphate in the body found?
Like calcium most phosphate (PO4 3−) in the body is found in mineralised bone
Where is the rest of the phosphate stored in the body that is not in bone?
The unbound, free remainder is involved in several physiological processes e.g. maintenance of cell membrane, acid-base balance and cell energy production. Phosphate is a main intracellular ion
What age animals tend to have higher levels of phosphate?
Phosphate levels are higher in young, growing animals than in mature animals.
Why is Hyperphosphataemia often seen in animals with renal failure?
Hyperphosphataemia is often seen in animals with renal failure due to decreased excretion
What condition can hypophosphatemia develop?
Hypophosphataemia, can develop with metabolic conditions such as diabetic ketoacidosis - this can cause haemolysis.
Where is most of the magnesium in the body found?
This is a main intracellular cation – magnesium (Mg 2+) has a similar distribution to calcium and phosphorus in the body. Most is found in muscle or bone.
What is free magnesium? What is its main role?
As with plasma calcium, free/ ‘ionised’ magnesium is biologically active. (involved in heart and muscle contraction) Magnesium is involved in cell energy production and heart and muscle function
What conditions commonly present with hypomagnesia, what signs may be seen with this?
Hypomagnesia can be present in critical patients, especially if there are other
electrolyte abnormalities. It is most seen in diabetic patients that are also hypokalemic. In the presence of refractory hypokalaemia, magnesium should be
measured and supplemented as indicated. It can cause neuromuscular weakness, cardiac arrhythmias and anaemia.
What is osmolality?
Osmolality is a measure of the number of dissolved particles per unit of water e.g.
how concentrated the fluid is.
What is plasma osmolality? what does this indicate?
Plasma osmolality is a measure of the number of dissolved particles per unit of water
in plasma: ‘tonicity’. It indicates how concentrated the plasma is and is a good
indicator of water-balance
What is meant by hypertonic fluids?
As many critical patients have water imbalances, it is
useful to be able to measure the osmolality of fluids e.g. plasma/serum.
With water loss, there are relatively more dissolved particles per unit of water. The
fluid is more concentrated e.g. hypertonic
lots of particles in fluids
What is hypotonic?
With water gain, there are less dissolved particles per unit of water. The fluid is hypotonic.
A few particles in fluids - dilute
What is isotonic?
If the osmolality of two fluids is the same, this is called isotonic
same number of particles in another fluid
What is the calculation for serum/plasma osmolality?
Serum/plasma osmolality = 2(Na++K+) + BUN (blood urea nitrogen) + BG (Blood glucose)
What is often used as an indicator of urine osmolality?
Urine specific gravity (SG) measurement is often used as an indicator of urine osmolality.
What effect does sepsis have on bilirubin?
Hyperbilirubinaemia is common in animals with
sepsis (especially cats). In dogs it is thought to result from an endotoxin-induced defect in hepatocellular transportation of conjugated bile resulting in intrahepatic cholestasis; whereas in cats it is likely a result of haemolysis.
What is blood biochemistry?
Clinical/blood biochemistry is the chemical analysis of blood (serum/plasma).
What does an emergency biochemistry panel include?
ALT ALKP BUN CREA BILE ACIDS TP ALBUMIN GLOBULIN
What is the abbreviation ALT?
alanine aminotransferase
What would increase levels of ALT indicate?
This is specific for liver cell damage - significantly increased levels are associated with hepato-cellular necrosis. The levels are frequently raised following trauma, hepato-toxicity and hypovolaemic shock.
What biochemistry slide is specific for liver cell damage?
ALT
What is the abbreviation ALKP?
alkaline phosphatase
What parts of the body does the biochemistry slide ALKP provide information about?
Although this is found in several different tissues in the body, ALKP/AP is generally considered to provide information about bone and the liver- especially liver cell damage and biliary stasis.
What is increased levels of ALKP associated with?
Increased levels of ALKP/AP can be associated with hepatocellular disease, hepatobiliary pancreatitis, biliary obstruction, administration of steroids or high levels of endogenous steroid. It will be elevated in the juvenile patient due to increased osteoblast activity in bone
Why would ALKP levels be increased in juvenile animals?
It will be elevated in the juvenile patient due to increased osteoblast activity in bone
What information does assessment of bile acids provide?
An assessment of bile acid levels provides information about hepatic function
Where are bile acids normally excreted in to? What organ reabsorbs it?
Bile acids are normally excreted into the gall bladder then into the gastrointestinal tract. 90% of bile acids are then reabsorbed from the intestine and transported back to the liver.
What conditions are alterations in bile acid levels usually seen?
Alterations in bile acid levels may be seen in
association with a decrease in hepatic function such as portosystemic shunts.
When is a blood sample usually collected for a bile acid test?
An assessment of bile acid levels is usually made before and 1-2 hours after food (‘fasted’ and ‘post-prandial’)
What is creatinine a breakdown product of?
Creatinine is formed at a regular rate by the breakdown of protein - it is then excreted by the kidneys
What are increased levels of creatinine usually associated with?
decreased renal excretion
What is albumin and what organ produces it?
Albumin
Albumin is the main plasma protein and is produced by the liver
What does creatinine provide information about?
Creatinine provides information about the functional capacity of the kidneys, in particular glomerular filtration rate.
What is azotaemia?
Azotaemia is an increase in
nitrogenous blood products - creatinine and urea.
What are the three main causes for elevated creatinine?
Elevated creatinine can be pre-renal
(decreased kidney perfusion); renal (typically intrinsic/intrarenal causes) or postrenal (bladder rupture, urethral obstruction)
What is the cause of a pre renal elevation in creatinine ?
decreased kidney perfusion);
What is the cause of a renal elevation in creatinine ?
(typically intrinsic/intrarenal causes
What is the cause of a post renal elevation in creatinine ?
bladder rupture, urethral obstruction)
What is total protein the sum of ?
Total protein
This is the sum of albumin and globulins
What important role does albumin have?
It is a large protein which has an important role in maintaining the intravascular colloid oncotic pressure
i.e. it is very important in osmosis and intravascular
fluid balance.
Which component of total protein is likely to be the cause of an alteration?
Total protein levels are mostly likely to be affected by altered levels of
albumin
What can a decreased albumin level be due to?
Decreased plasma albumin levels can be due to decreased production or
increased loss
What disease processes can a decreased albumin level be?
A decrease in albumin can be seen with gastrointestinal disease/protein-losing enteropathy (PLE), protein losing nephropathy, malnutrition, dilution (e.g. IVFT) and liver disease.
What can a decreased albumin be secondary to?
It can also occur secondary to serious inflammation
with or without infection (e.g. pancreatitis/ sepsis) where vasculitis leads to leaking of
albumin from the blood vessels (redistribution).
What are the three classes of Globulins?
Globulin
There are three classes- alpha, beta and gamma.
Where are alpha and beta globulins produced and what are their main functions?
Alpha and beta globulins are
produced in the liver and are involved in enzyme and cell transport functions
What produces gamma globulins and what is their main function?
Gamma (immuno) globulins are produced by plasma cells and are involved in the
immune response
What are the different classes of immunoglobulins?
There are different classes of immunoglobulins (Ig) e.g. IgG, IgA, IgM and IgD
How are globulin levels calculated?
Globulin levels are calculated by subtracting the albumin level from the total protein.
What are increased levels of immunoglobulins often seen with?
Increased levels are often seen with infection and
inflammation, due to increased production of gamma globulins
How can liver disease affect urea levels?
Liver disease: ammonia is converted to urea in the liver, so urea levels can be decreased with chronic liver disease (cirrhosis); or if the liver is bypassed e.g.
portosystemic shunt.
How can renal disease affect urea levels?
Renal disease. Urea is excreted by the kidneys, so levels will be elevated by renal disease. As with creatinine, however, elevated urea levels could be prerenal (e.g. hypovolaemia/dehydration), renal or post-renal (urethral obstruction). Serum creatinine is a more reliable indicator of renal function.
How can Gastrointestinal haemorrhage or high protein diet affect urea levels?
Gastrointestinal haemorrhage (or very high protein diet)- the increased protein digestion will result in elevated urea levels, but creatinine will be normal.
What is a packed cell volume also known as?
The packed cell volume (PCV) is often also known as the haematocrit.
What is a packed cell volume a measurement of?
This is a measurement of the percentage of the blood volume represented by the red blood
cells - it provides an indication of the oxygen carrying capacity of the blood.
What two ways is a PCV measured?
The PCV and haematocrit are measured in different ways:
• The PCV is measured manually using centrifuged blood and a microhaematocrit reader.
• The haematocrit is calculated using an automatic analyser (
What is the normal PCV for a dog
37-55%
What is the normal PCV for a dog?
30-45%
What are reticulocytes?
➢ Reticulocytes
Reticulocytes are immature, non-nucleated red blood cells that are found in the circulation in increased numbers in regenerative responses.
What type of response are increased number of reticulocytes seen?
➢ Reticulocytes
Reticulocytes are immature, non-nucleated red blood cells that are found in the
circulation in increased numbers in regenerative responses.
What does the mean cell volume provide information about?
The mean cell volume provides information about the average size of red blood cells
What can the 3 different sized cells be described as ?
Cells may be:
• macrocytic (bigger than normal),
• normocytic (normal size)
• microcytic (smaller than normal).
What is macrocytic?
Relates to cells size - bigger than normal
What is normocytic?
Relates to cell size normal size
What is microcytic?
relates to cell size - smaller than normal
Why would erythrocytes be macrocytic following haemorrhage?
RBCs become smaller as they develop in the bone marrow- so if immature are
released early into the bloodstream e.g. following haemorrhage, they will be
relatively large. In regenerative anaemia, immature cells are often released into the
circulation and are relatively larger than mature erythrocytes
Why are erythrocytes smaller with iron deficiency?
If a patient, has iron
deficiency anaemia, the circulating red blood cells are smaller than normal as they
have spent longer developing in the bone marrow, due to the lack of iron.
What is mean cell corpuscular haemoglobin concentration?
Mean cell (corpuscular) haemoglobin concentration (MCHC) This is a measurement of the average haemoglobin concentration per red blood cell
What are the two different values of mean cell haemoglobin concentration MCHC?
Depending on the haemoglobin levels in RBCs, they will be
• normochromic (normal colour = normal haemoglobin concentration)
• hypochromic (paler than normal = reduced haemoglobin).
What is meant by the term normochromic with mean cell haemoglobin concentration?
normochromic (normal colour = normal haemoglobin concentration)
What is meant by the term hypochromic with mean cell haemoglobin concentration?
hypochromic (paler than normal = reduced haemoglobin).
What will the mean cell haemoglobin concentration be if the patient has had a recent haemorrhage? Why?
Immature RBCs contain less haemoglobin- thus regenerative anaemia will usually be
hypochromic; whereas non-regenerative anaemia will be normochromic.
What is a large number of neutrophils commonly associated with?
Neutrophils: an increase in the number of neutrophils is most commonly associated with infection or inflammation.
What cell is a white blood cell count made up of?
The white blood cell count is made up of neutrophils, lymphocytes, eosinophil, monocytes basophils.
What are immature neutrophils known as?
band cells
What is a left shift on a blood smear?
an increase in the number of immature neutrophils in the circulation is known as ‘a left shift’
Why is a left shift usually seen on a blood smear?
This is seen where neutrophils are
involved in an active inflammatory or infectious process; or where there is abnormal neutrophil production.
In a normal neutrophil regenerative response what will give the indication that the immune response is working well?
In a normal regenerative response, the
number of mature neutrophils will outnumber the band neutrophils indicating that the immune response is working well
What is a degenerative left shift on a blood smear? What does this indicate?
However, if band neutrophils outnumber the mature neutrophils, this indicates that the mature neutrophils are being consumed/destroyed- the immune response
is not working as well as we would like or is being overwhelmed. This is called a degenerative left shift
What is lymphopaenia?
Lymphopaenia (decreased circulating lymphocyte numbers)
What is the presence of lymphocytes on a blood smear associated with?
Lymphocytes (T and B lymphocytes) are associated with the immune response
What can lymphopaenia be seen in association with?
Lymphopaenia (decreased circulating lymphocyte numbers) can be seen in association with acute infection or chronic stress e.g. chronic disease or corticosteroid therapy etc.
What is lymphocytosis?
Lymphocytosis (increased numbers of circulating lymphocytes)
What can lymphocytosis be seen in association with?
Lymphocytosis (increased numbers
of circulating lymphocytes) can be seen with hypoadrenocorticism,
leukaemia or prolonged antigenic stimulation. It may also be seen with an
acute stress response.
What may an increased number of eosinophils on a blood smear be associated with?
Eosinophils are present in relatively small numbers. They are associated
with allergic disease and parasitism. Increased numbers may also be seen
with specific conditions such as pulmonary infiltration with eosinophilia
(PIE) or neoplasia. Eosinopaenia may be a stress response or secondary
to corticosteroid treatment
Abnormalities in basophil numbers are very common
True or False?
FALSE - Basophils abnormalities in basophil numbers are rarely identified.
Why are monocytes only present in blood for a short time?
Monocytes these large cells are only present in blood for a short time before leaving and developing into macrophages.
What can increased numbers of monocytes be associated with?
Increased numbers can be associated with chronic, intracellular infections or a stress response
What is haemostasis?
Haemostasis is the process of stopping bleeding by vasoconstriction and clot
formation/ coagulation
What are the 4 steps to Haemostasis?
vasoconstriction
• primary haemostasis - formation of an initial platelet plug
• secondary haemostasis/ clot formation - the platelet plug is stabilised by cross-linked fibrin- clot
• thrombolysis- clot break-down.
What is primary haemostasis?
Formation of an initial platelet plug
What is secondary haemostasis?
The platelet plug is stabilised by cross linked fibrin
Why can platelet numbers affect primary haemostasis?
Primary Haemostasis
Platelets are required for primary haemostasis (the start of clot formation).
Alterations in the platelet numbers occur for many reasons and with various
diseases.
What t can thrombocytopaenia arise due to?
For example, thrombocytopaenia can arise due to:
• Increased platelet destruction e.g. immune-mediated thrombocytopaenia
(IMHA)
• Increased platelet ‘consumption’: platelets have been used up secondary to
haemorrhage or inflammation.
Where does the monolayer segment lie on a blood smear?
The monolayer segment lies between the feathered edge of the smear and the main body of the smear - it is composed of a single layer of cells.
What microscopic field is required to examine the monolayer?
Oil immersion fields are examined in the monolayer segment of the smear.
How many platelets on a blood smear should be seen per field on average?
Therefore, a normal blood smear should have 11-15
platelets per field on average. Each one platelet, seen in an oil immersion (x100) field, is roughly equivalent
to 15x109 platelets/l.
What would be considered a dangerously low level of platelets on a power field?
Dangerously low levels of platelets would be
indicated by less than 3 platelets per oil immersion field (equivalent to 0-45x109/l)
What can be used to carry out a manual true platelet count?
A true platelet count may be done, manually, using a haemocytometer, commercial diluting fluid and a microscope
What is the technique for carrying out a manual true platelet count on a haemocytometer?
A commercial ammonium oxalate diluent pipette system should be used (e.g. ‘Unopette Micro-collection
System for WBC and Platelet Determination’ produced by Becton-Dickinson, Oxford UK). This is filled as directed and lyses the red cells after ~ 10 minutes. A Neubauer modified haemocytometer is then filled with the mixture and left in a humid
environment (a small covered dish with a layer of wet filter paper in the bottom) for 5-10 minutes, to allow the platelets to settle to the floor of the haemocytometer. A platelet count is then performed by examining the haemocytometer microscopically.
Platelets can be differentiated from white cells by their smaller size and refractile nature. The total number of platelets, in the central major square on each side of the haemocytometer, is counted. This square is divided into 25 smaller squares, each of which contains 16 further squares. The average of the two major square counts is then the total platelet count in 109 /l. Normal values for dogs are 200-700x109 /l and for cats are 300-800 x109/l.
What is the best way to clinically assess platelet function?
Platelet function can be assessed in a laboratory using specific analysers. Clinically, however, the best way is to perform a buccal mucosal bleeding time
How can a Buccal mucosal bleeding time test be carried out?
Buccal mucosal bleeding time - The BMBT requires the use of a commercial device that produces two standardised cuts to the buccal mucosa of the upper lip - 5mm long and 1mm deep. The patient is placed in lateral recumbency, the upper lip is
reflected to expose the mucosal surface and held in place by a gauze tape lightly applied around the maxilla, enough to partially block venous return (Oakley, 2007).
The BMBT device is then placed on the mucosa and activated. The incisions are then left alone until bleeding stops- the time taken should be recorded. This is assessed by using a swab or filter paper placed near to the incisions (3-4 mm below), but not touching them. Bleeding is judged to have stopped when blood stops being taken up by the clean edge of the swab/filter paper. The BMBT is taken as the mean bleeding time of the two incisions and should normally be less than 4 minutes. The BMBT evaluates primary haemostasis by assessing platelet and vascular
aspects of haemostasis
When might you see an increase in buccal mucosal bleeding time?
Instances where BMBT may be increased include:
• thrombocytopaenia
• von Willebrand’s disease
• drug therapy e.g. aspirin.
What test should be carried out prior to a buccal mucosal bleeding time test and why?
A BMBT should NOT be performed on dogs that are already known to be thrombocytopaenic- thrombocytopaenia should be confirmed initially on a blood smear, as previously discussed. Thrombocytopaenic animals will have a prolonged
BMBT so confirmation with the test is unnecessary
What can secondary haemostasis be affected by?
It can be affected by deficiency in any clotting factor. These deficiencies may arise from a lack of production (e.g. vitamin K deficiency or haemophiliacs); or consumption of the coagulation factors (e.g. sepsis or trauma).
What is secondary haemostasis?
Secondary haemostasis is the process of clot formation using coagulation factors - it
follows the formation of an initial platelet plug
What does activated partial throboplastic time assess?
Activated partial thromboplastin time (aPTT)
This assesses the function of both the intrinsic and common pathways. Activated partial thromboplastin time (aPTT) is measured from blood collected into a citrated plasma tube. The tube MUST be accurately filled as the results will be inaccurate
otherwise.
Calcium and brain tissue thromboplastin (or a similar source of lipoprotein) are added to the citrated tube- this activates the clotting process leading to fibrin formation. The intrinsic and common pathway factors are activated in this process (factors XII, XI, IX, VIII, X, V, and II). Final fibrin formation can be monitored by optical or mechanical means. This is not a very sensitive test, as factors must be reduced to less than 30% of their normal values before the aPTT is prolonged. A dog with bleeding caused by haemophilia A (lack of factor VIII) or von Willebrand’s disease, may have a prolonged aPTT - it is, however, possible that aPTT could still be within the normal reference range.
What does prothrombin time identify deficiencies in?
Prothrombin time (PT) This identifies deficiencies in the extrinsic (factor VII) and common pathways (fibrinogen, II, V and X). It measures the time for fibrin to be produced after activation of factor VII, then factors X, V and II (prothrombin). Tissue factor and calcium are added to a citrated plasma tube, containing a blood sample, to activate. The tube MUST be accurately filled as an inaccurate result will be obtained otherwise. Fibrin formation, from fibrinogen, is the end point of the assay - this can also be measured using optical or mechanical means. As with aPTT, deficiencies of less than 30% are required to produce prolongation of the PT. Factor VII has the shortest half-life of the clotting factors, so PT maybe increased before aPTT in a patient with a coagulopathy.
Will APTT or PT increase first with rodenticide poisoning?
Acquired vitamin K deficiency (rodenticide poisoning) is an example of a condition that can prolong PT. Whilst eventually both PT and APTT will increase, PT will become elevated first-normally within 48-72hrs of ingestion of the rodenticide.
How is an activated clotting time test performed?
Activated clotting time.
Activated clotting time is measured by taking a blood sample, then discarding the first 0.25-0.5 ml of it. This removes the tissue factor which could otherwise
complicate the test. 2ml of the blood sample is put into a tube containing diatomaceous earth (produced by Becton-Dickinson, Oxford). After mixing, the tube
is incubated at 37°C for 60 seconds in the dog; and 45 seconds in the cat. After this the tube is gently tilted, at 10 second intervals, to determine if a clot has formed.
Normal ACT for dogs is 60-110 seconds and for cats is 50-75 seconds.
An in-house test-kit is also available for measuring activated clotting time (ACT).
Sampling technique is important when considering coagulation profiles. Samples
should be from a “clean stick”, with minimal dwell time in the vessel and they should be non-haemolysed. Other patient specific factors considerations need to be considered (e.g. a patient with a coagulopathy should not have jugular blood
samples taken)
How can a saline agglutination test be performed?
Additional laboratory tests
Slide Agglutination (also called saline dispersion test)
A saline dispersion test should be performed to determine if there is true agglutination in a blood sample. N.B. Agglutination can arise with immune-mediated haemolytic anaemia when antibody covered RBCs stick together.
In this test, a drop of blood from an EDTA blood tube or capillary tube is put onto a slide- it is assessed for the presence of agglutination (development of obvious flecks within the drop of blood). If agglutination appears to be present, three drops of saline are added to the blood on the slide. This will cause dispersal of RBCs if rouleaux (stacking of RBCS) rather than agglutination was present- the flecks will disappear with rouleaux. If true autoagglutination has occurred, the flecks will still be seen as the RBCs remain stuck together. Autoagglutination is caused by cross-linking of antibodies which are bound to the erythrocyte membranes - this is diagnostic for an
immune-mediated component to the haemolysis. It is important to remember that the saline does not induce the agglutination – it merely confirms that it is true
agglutination.
What does a saline agglutination test help to diagnose?
If true autoagglutination has occurred, the flecks will still be seen as
the RBCs remain stuck together. Autoagglutination is caused by cross-linking of
antibodies which are bound to the erythrocyte membranes - this is diagnostic for an
immune-mediated component to the haemolysis
What is a coombs test and what does it help to confirm?
Coombs Test
A Direct Antiglobulin Test looking for the auto-immune antibodies that are directed against the red cells (Coombs) can be used to confirm immune mediated haemolytic anaemia. Because the end (positive) result of this test is agglutination, the Coombs
test need not be run if the patient is already auto-agglutinating. Blood should be taken for this assay prior to transfusion.
What are the pros and cons of using radiography over ultrasound or vice versa?
Radiography uses ionising radiation, which is potentially harmful, but provides a wide viewing area e.g. the whole thorax may be seen. It provides clear
images of bones and other organs.
Ultrasound is non-invasive and provides ‘realtime’ (current) images that are constantly being updated. This can give information about the movement or function of some organs. It is very good at detecting ‘free
fluid’.
What position with an animal be in for a dorso-ventral radiograph?
Dorso-ventral The X-ray beam travels from dorsal to ventral (the patient
is in sternal recumbency)
What position will the animal be in for a ventro-dorsal x-ray?
Ventro-dorsal The X-ray beam travels from ventral to dorsal (with the patient in dorsal recumbency) NEVER IF PATIENT DYSPNOEIC
What radiographic views are not suitable for dyspnoiec patients?
Ventro-dorsal
The X-ray beam travels from ventral to dorsal (with the patient in dorsal recumbency) NEVER IF PATIENT DYSPNOEIC
Right lateral
The animal is lying on its side with the right side closest to the cassette
Left lateral
The animal is lying on its side with the left side closest to the cassette N.B. lateral views are also not safe for a dyspnoeic patient
What is a rostrocaudal radiographic view?
Rostrocaudal The X-ray beam passes through the skull in a rostral to caudal direction. The patient is positioned in dorsal recumbency. As this view requires general anaesthesia it is not likely to beperformed in the emergency presentation.
What is an oblique radiographic view?
Oblique The X-ray beam passes through the area of interest at an oblique angle. This provides more information about the area under investigation by preventing superimposition.
What is the KV on an xray machine?
Kilovoltage- penetrating power of the X-ray beam
What is mAs on an xray machine?
milliampere seconds- number of X-rays
What is the FFD o nan xray machine?
Focal (spot) Film Distance. This is also known as the
Film Focal Distance. It is the distance between the focal spot and the X-ray table
What is positive contrast?
Radiodense/opaque material which is introduced into a
patient. Appears white on the radiograph
What is negative contrast?
Radiolucent gas which is introduced into a patient.
Appears black on the radiograph
What is double contrast?
Both positive and negative contrast are introduced into the patient
to provide maximum detail of the area being examined
What is Mhz on an ultrasound machine?
Megahertz- measurement of the sound wave frequency
What is echogenic?
Ability of a structure to produce echoes
What is anechogenic?
No echoes produced- appears black on ultrasound e.g fluid
What is hypoechoic?
Less echoes produced than adjacent tissues. Appears grey on ultrasound e.g. soft tissue
What is hyperechoic?
Very echogenic. More echoes produced than adjacent tissues.
Appears whiter on ultrasound e.g. relative more dense soft tissue, bladder calculus, bone
What is isoechoic?
The same echogenicity as neighbouring tissue
If a patient presents with signs of a pleural effusion would you radiograph to confirm this?
Example- pleural effusion as the cause of respiratory distress in a dyspnoeic patient is likely to be apparent from the clinical examination.
Therefore, rather than performing radiography at this stage, which will only confirm what was already apparent, and could cause the patient’s condition to worsen, the veterinary surgeon is likely to perform
emergency thoracocentesis (removal of the pleural effusion), following a period of oxygenation. Not only will this be diagnostic, but it will help to improve the patient’s condition.
Following this, with the fluid removed and the patient’s condition improved, radiography might be appropriate- it should be safer and the underlying cause of the effusion may be apparent e.g. liver lobe
incarcerated in the thorax secondary to diaphragmatic rupture.
What radiographic view should be the only one considered in a dyspnoiec patient?
A dorsoventral view is the only projection that should be considered if the animal has
breathing difficulties.
What view is preferred when assessing the heart and lungs?
Although dorsoventral thorax is the usual orthogonal view especially for imaging the heart and the caudal lung lobes, occasionally a ventrodorsal radiograph of the thorax should be obtained as well. The ventrodorsal view is preferred where the main area of interest includes the cranial mediastinum, caudal vena cava or accessory lung lobe.
On a lateral radiograph, what is the width of the heart usually in dogs and cats?
On the lateral radiograph the width of the heart is normally 2.5-3.5 intercostal spaces
in dogs; and 2 intercostal spaces in cats. T
On a lateral radiograph, what is the height of the heart usually in dogs and cats?
The height of the heart is roughly two thirds
of the height of the thoracic cavity in both dogs and cats, although there are breed variations
On a dorsoventral radiograph how wide is the heart usually in the thoracic cavity?
On the dorsoventral view the heart is roughly two thirds of the width of the thoracic cavity
On the lateral radiograph where should the apex of the heart sit?
On a lateral view of the thorax, the apex of the heart should sit just above the sternum. If elevated it might indicate the presence of air or fluid
Explain what the vertebral heart score is?
The vertebral heart score technique can be used to assess cardiac size. There is
some variation of vertebral heart score between different breeds. On a lateral view
of the thorax the long axis of the heart (from carina to the apex of the heart) and the
short axis (widest part of the heart in a line at right angles to the long axis) are measured. These lengths are then compared to the number of vertebrae from the cranial edge of T4. This will then give a length for each axis in whole/part thoracic vertebrae. Adding these two scores together gives the vertebral heart score (IMV,
2011).
Suggested normal values for dogs are 8.5–10.7; the normal value for a cat should be
< 8.
How can an enlargement of the heart be detected on a radiograph?
Enlargement of the heart will present as a change in the cardiac silhouette and alterations in the position of neighbouring structures e.g. elevation of the trachea.
Alterations in the lung patterns such as air bronchograms or increased lung density
may also be present if the patient has pulmonary oedema.
What conditions might cardiomegaly be associated with?
Cardiomegaly can be
associated with a variety of conditions including vascular disease, congenital cardiac
disease (e.g. patent ductus arteriosus) and cardiomyopathies.
How can left sided heart failure be detected on a radiograph in dogs and cats?
In left-sided congestive heart failure
the pulmonary veins will be enlarged compared to the arteries, and there may be
peri-hilar alveolar/interstitial pattern in the dog; or diffuse/patchy interstitial/alveolar
pattern in the cat.
What is a cardiac shadow? and when might it be seen?
Enlargement of the cardiac shadow could also be due to pericardial disease rather than enlargement of the heart itself as soft tissue and fluid have the same radiographic opacity. Pericardial effusion is quite common in the emergency patient – it can be idiopathic, haemorrhagic (e.g. coagulopathy), neoplastic or infectious.
The cardiac shadow is usually very rounded and enlarged on a thoracic radiograph of a patient with a pericardial effusion- however ultrasound is more sensitive for diagnosing this condition as it can differentiate between fluid and soft tissue unlike
radiography
What main lung patterns can be seen with lung disease?
vascular pattern
bronchial pattern
alveolar pattern
interstitial pattern
What would a vascular pattern look like on a radiograph in a patient that has lung disease - What may be causing this?
• Vascular pattern
o Increased or decreased width of pulmonary vessels due to congestion or hypovolaemia.
What would a bronchial pattern look like on a radiograph in a patient that has lung disease - What may be causing this?
Bronchial pattern
o Thickening of the bronchi associated with inflammation (e.g.
feline ‘asthma’)
What would an alveolar pattern look like on a radiograph in a patient that has lung disease - What may be causing this?
Alveolar pattern
o The presence of fluid in the alveoli results in a fluffy appearance
of the lung fields. This could be caused by oedema (heart failure, drowning), haemorrhage or pneumonia (e.g. aspiration).
There may be air bronchograms
What would an interstitial pattern look like on a radiograph in a patient that has lung disease - What may be causing this?
• Interstitial pattern- increased opacity of the interstitial tissue which can
be nodular or unstructured
o e.g. oedema, pneumonia, haemorrhage, neoplasia, abscess.
What assessment should be made of the bony structures on a thoracic radiograph?
Assessment of the bony structures of the thorax should be made
• Fractured ribs / sternum
o May be associated with pulmonary contusion
o There may be a flail chest
o There may be fractured ribs close to the vertebrae in a cat with
feline asthma syndrome
What signs are indicative of a pneumothorax on radiographs?
If radiography is performed, changes indicative of pneumothorax include retraction of the lung from the chest wall (loss of vascular markings in this space), consolidation of lung lobes; and, on the lateral radiograph, the appearance of the heart “floating” on a cushion of air. The latter radiographic finding is due to the heart ‘falling’ to the side of the atelectatic (collapsed
or airless) “down” lung. N.B. If a patient is dyspnoeic, as is likely with significant pleural space disease, a lateral view should NOT be attempted.
What signs are indicative of a pleural effusion on radiographs?
Retraction of lung lobes will be present. Interlobar fissures may
also be more prominent due to the surrounding fluid; and it will
probably be difficult to see the cardiac shadow.
What signs are indicative of a diaphragmatic rupture on radiographs?
The final image will depend on the amount and type of tissue that has passed from the abdomen into the thorax. The presence of a pleural effusion may obscure other findings. Part or all the lung fields may be obscured; intestinal gas shadows may be present in the thorax. Diaphragmatic rupture can cause unilateral or bilateral radiographic changes - the normal
diaphragmatic outline will not be visible.
What signs are indicative of a pneumomediastinum on radiographs?
On the lateral view, air within the mediastinum will
increase contrast in this area; resulting in structures, such as the aorta, which are not normally visible in this area being seen.
What signs are indicative of mediastinal fluid on radiographs?
Fluid within the mediastinal space will make the
mediastinum more obvious on dorsoventral view- it will
appear wider
What signs are indicative of a mediastinal mass on radiographs?
These may be obvious as soft tissue density or may
displace the surrounding tissues such as the heart and trachea.
What pleural space disease may be seen radiographically?
o Pericardio-peritoneal diaphragmatic hernia o Megaoesophagus may be visualised o Tracheal collapse mediastinal mass mediastinal fluid pneumomediastinum pneumothorax pleural effusion diaphragmatic rupture`
What emergency situations is radiography of the abdomen indicated?
• Acute abdomen o Vomiting o Abdominal pain • Following a road traffic accident • Vomiting • Suspected gastro-intestinal foreign body • Gastric dilatation +/- volvulus • Bladder rupture • Blocked urethra • Pyometra • Ascites (although radiographically there will be poor abdominal contrast if there is free fluid) • Confirmation of whether Caesarean is required
When is a grid required on an x-ray?
use a grid for larger animals (> 10-15 cm tissue
depth).
What is an ultrasound most useful at observing?
In the emergency patient, ultrasound can be used for identification of free fluid or to obtain more information on specific organ(s) e.g. an enlarged uterine outline, as
indicated by radiography, can be shown to be distended and fluid filled in a patient with pyometra (VetGirl, 2018) if ultrasound is performed.
The urinary bladder, gall bladder, uterus, prostate, spleen and pancreas can all be assessed relatively easily during emergency ultrasound. In addition, foetal heart beats can be visualised. This allows for monitoring of the pregnant patient and
foetuses. Ultrasonic evidence of foetal distress (e.g. heart rate < 160-190/ bpm) could be an indication for proceeding to Caesarean section
What is the aim of an ultrasound in an emergency situation?
The aim of the ultrasound examination is prompt detection of free fluid
How many areas should be examined on a pocus and where are they?
Four areas are examined in two planes
Subxiphoid or diaphragmatico-hepatic (DH) site
▪ Left paralumbar or spleno-renal (SR) site
▪ Off midline over the bladder or cysto-colic (CC) site
▪ Right paralumbar or hepato-renal (HR) site
What are the two different type of abdominocentesis?
Abdominocentesis can be performed using either an open or closed
technique.
What does a closed technique for an abdominocentesis involve? What are the disadvantages of this?
The closed technique involves attachment of a syringe to the needle prior to insertion, with fluid being collected by aspiration of the syringe. This prevents air from entering the abdomen: this would be apparent as a pneumoperitoneum on radiographs. The disadvantage of this technique is
the potential occlusion of the needle bevel by omentum
What does a closed technique for an abdominocentesis involve? What are the disadvantages of this?
An open technique relies on passive gravitational flow of fluid from the abdomen rather than syringe aspiration. A needle or catheter is inserted in
the most gravity-dependent portion of the abdomen and fluid allowed to flow by gravity. With an open technique, there is a risk of air entering the abdomen causing a pneumoperitoneum. This may be visualized radiographically and complicate their interpretation.
How do you perform an abdominocentesis and what equipment is needed?
Using an aseptic technique, a 21 gauge (g) 1 to 1.5-inch hypodermic needle (dog) or 23 g ¾ inch needle (cat) is introduced into the abdomen, possibly under ultrasound guidance. To avoid splenic injury, abdominocentesis is usually performed with the patient in sternal or left lateral recumbency –
although if free fluid has been identified following ultrasound examination,
the position of the patient for abdominocentesis will be dictated by where
the fluid is located.
▪ Fluid may be collected into plain and EDTA tubes for analysis (PCV, TS,
cytology, chemical analysis +/- culture and sensitivity); a slide should ideally
be prepared for in house microscopic examination.
What should be noted after taking an abdominal x-ray?
The size, shape and opacity of the abdominal structures should be assessed. a slide should ideally be prepared for in house microscopic examination. The position of the following should also be noted: • Stomach • Duodenum • Small intestine • Large intestine • Liver • Pancreas • Spleen • Bladder • Female/male reproductive tract • Kidneys (retro-peritoneal)
When would be a reasonable period of time to repeat radiographs on a patient that has a suspected foreign body but is in a stable condition?
If a patient is suspected of having e.g. an intestinal foreign body, if its condition is stable, it is acceptable to wait a few hours (~4-6hrs) to re-Xray, for consistent signs of an obstruction, rather than e.g. every hour. It is imperative that diagnostic radiographs are produced even in an emergency.
What are some of the emergency conditions that could demonstrate radiographic abnormalities?
Due to the large number of abdominal organs, numerous radiographic abnormalities could be identified. Emergency conditions that could demonstrate radiographic abnormalities (contrast may be required in some cases) include: • GDV • Abdominal/ peritoneal effusion • Foreign bodies • Intussusception • Free gas (pneumoperitoneum) • Hepatomegaly • Distended/ ruptured bladder • Renoliths/ ureteroliths/ uroliths/ uretholiths • Dystocia/pyometra • Hernia/ body wall rupture • Splenic tumour • Prostatomegaly
What xray position is needed to diagnose a gastric dilation or GDV? What position is contraindicated?
Radiography can differentiate gastric dilation from GDV. A right lateral (and possibly
a dorsoventral view) should be obtained. N.B. a ventrodorsal view would be
contraindicated in this situation due to the patient having impaired ventilation and
blood flow.
How will a gastric dilation and GDV appear on an x-ray?
The stomach appears as a large, distended, gas-filled structure- the pylorus is in an abnormal position if volvulus has occurred. It is located dorsally and slightly cranial to the fundus. There is usually compartmentalisation/ reverse “C” sign - a band of
soft-tissue between the pylorus and fundus due to the ‘twist’.
What can a decreased abdominal detail/contrast on an x-ray be caused by?
Decreased abdominal detail/ contrast (ground-glass appearance) can be caused by -
• abdominal effusion
• absence of abdominal fat (e.g. in a puppy or emaciated animal)
• pancreatitis (localised).
Which area of the intestine is most affected by intussusception?
Although an intussusception can affect any part of the intestine, the most affected area is the ileocaecocolic junction
What diagnostics need to performed to diagnose an intussusception?
This can be confirmed with ultrasound or a
barium sulphate study (enema). As barium fills the space between the two layers of the intussusception, it takes on the appearance of a coiled spring. N.B. As with all contrast studies, barium sulphate should not be administered if there is suspicion of gastro-intestinal rupture/ perforation due to the risks associated with barium leaking into the abdomen
What is Barium sulphate?
Barium sulphate is a positive contrast agent that is used exclusively in the alimentary tract
What can barium sulphate be used to examine?
Barium sulphate suspension (liquid) or barium impregnated polyethylene spheres (BIPS) can be used to examine the gastrointestinal tract, for identification of intestinal obstructions, strictures etc. A barium meal
(barium sulphate mixed with food) can be used to confirm megaoesophagus
What are the contraindications of using barium sulphate?
Barium sulphate should NOT be given if there is any concern about an
alimentary tract rupture e.g. oesophageal perforation. If administered orally,
great care must be taken to avoid aspiration especially in a patient suspected
of having megaoesophagus
What can intravenous urography be used to examine?
Intravenous urography can be used to examine the structure, and function, of the urinary tract (especially the upper urinary tract - kidneys and ureters).
What must be done prior to performing intravenous urography?
The patient must be well-hydrated and non-azotaemic before performing this
procedure so pre-procedure stabilisation will be indicated.
Why is it important not to inflate the bladder too much during a urography?
To be diagnostic, the bladder requires to be fully inflated BUT if too much contrast is introduced, there is a risk of bladder rupture especially in patients with chronic ongoing inflammation.
How do you perform a urinary contrast study?
The procedure must be performed aseptically. The
patient should have a urinary catheter placed and urine is first drained from the bladder, using a three-way tap and syringe. Contrast is then gradually
introduced into the bladder. During the procedure, the bladder should be carefully palpated to assess its size. If it feels ‘full’ via the abdomen or if there is resistance to introduction of contrast, no more should be introduced, and a check radiograph of the caudal abdomen should be obtained. If the bladder is
not fully inflated, more contrast can be introduced. The AVERAGE amount of contrast that can be introduced into the bladder is 5-10ml/ kg but there is
much individual variation depending on the underlying condition. If a bladder is chronically inflamed e.g. feline lower urinary tract disease, 1-2 ml/kg may be
the maximum amount that could be safely introduced. At the end of the contrast study the contrast should always be drained from the bladder.
What is a pneumocystography?
Pneumocystography is used to examine the bladder. Room air is generally used - although pure gases e.g. carbon dioxide and nitrous oxide from a
cylinder will produce better contrast and are also safer, as more soluble in blood (Zlot and Webster, 2011). The contrast produced with this technique is
less good than with double contrast cystography.
What is the main risk involved with a pneumocystography?
There is a risk of air embolism when gas is introduced into the bladder - it is advised that the
patient should be positioned in left lateral recumbency to avoid this. Because carbon dioxide (CO2) and nitrous oxide (N2O) are highly soluble there is less
risk of air embolism if they are used rather than room air or oxygen. N.B. If it is likely that the patient’s mucosa is very inflamed, air should be avoided due to
the increased risk of air embolism. It is also essential to avoid overdistension of the bladder.
What detail does a double contract cystography provide?
Double contrast cystography is used to provide optimum detail of the
bladder mucosa and the lumen e.g. masses or radiolucent calculi can be
seen.
How do you perform a double contrast cystography?
A small volume of iodinated, water soluble contrast material is introduced into the bladder. The patient is rolled carefully to encourage the
contrast to coat the mucosa. The bladder is then fully inflated with air, CO2 or N2O as for pneumocystography. A double contrast cystogram may also be obtained after positive contrast cystography. Most of the positive contrast is
removed from the bladder and replaced with air
What is positive contrast cystography used to identify?
Positive contrast cystography can be used to identify bladder rupture and
large filling defects e.g. tumour. The technique is the same as for
pneumocystography but using iodinated positive contrast media instead. The
large volume of contrast could obscure some small filling defects.
Ionic, hyperosmolar products can be used for bladder studies e.g. Urografin®
(meglumine amidotrizoate / sodium amidotrizoate) but non-ionic, hypoosmolar
products may be as cost-effective and less irritant.
What is a myelogram?
A contrast study maybe performed to provide more information about the spinal cord
e.g. is there spinal cord compression that will require surgery and if so where is it?
Due to the risks associated with movement, the patient must be anaesthetised for this procedure. The contrast medium used must be non-ionic and hypoosmolar (or third generation if available).
For cervical/cisternal myelography, a calculated volume of warmed contrast is injected into the subarachnoid space via the atlanto-occipital space. This is generally better for imaging the cervical/thoracic spine
How do you perform myelography?
The area must be surgically prepared as sterility is of the utmost importance and we must avoid introduction of bacteria into the cerebrospinal fluid (CSF). With the patient in lateral or ventral recumbency the skin from the occipital process of the skull, out to the wings of the atlas and
caudally to the third cervical vertebra is clipped and surgically prepped. If the patient is in lateral recumbency care needs to be taken to ensure that the endotracheal tube does not kink when the head is flexed to allow injection of the contrast. Cerebrospinal fluid can be collected for analysis, prior to injection of contrast media. Removing an equivalent volume of CSF to the amount of contrast to be introduced
means there is less risk of increasing the pressure in the subarachnoid space- this is important as increased pressure could cause seizures. Following administration of contrast, the patient must be positioned with its head elevated to prevent contrast
entering the ventricles. This can be achieved with sandbags or elevated platforms in beds. As a chemical agent has been introduced into the subarachnoid space and is mixed with CSF, it is important to be aware of the potential for side-effects
What post-operative care should a patient receive that has had a myelogram?
The patient should be monitored constantly until fully recovered from the anaesthetic; and following myelography the patient animal should be supported in sternal/ventral recumbency, with its the head elevated, to prevent contrast entering the ventricles of the brain. The patient must be closely monitored for seizures during recovery form myelography, especially if cisternal myelography is performed.
Which biochemical parameter is most likely to increase in response to persistent hyperglycaemia in a cat?
Select one:
a. Bile acids
b. Fructosamine
c. Urea
d. Creatinine
Fructosamine
Which statement is false?
Hypoglycaemia could be caused by
Select one:
a. insulinoma
b. stress
c. hypoadrenocorticism
d. sepsis
Stress
Which two radiographic views of the abdomen should ideally be obtained in the initial investigation of an animal with clinical signs of abdominal disease?
Select one:
a. Ventrodorsal only
b. Dorsoventral and lateral
c. Ventrodorsal and lateral
d. Lateral only
Ventrodorsal and lateral
Good abdominal detail is most likely to be present on the radiograph of which of the following animals?
Select one:
a. A Tonkinese cat with ‘wet’ feline infectious peritonitis
b. A 6 month old, emaciated Greyhound
c. A Cavalier King Charles Spaniel with ascites
d. An obese 12 year old Labrador Retriever
An obese 12 year old Labrador Retriever
Following administration of oral barium sulphate suspension, a ‘coiled spring’ appearance can be seen on an abdominal radiograph. Which condition could cause this?
Select one:
a. Ileus
b. Intestinal foreign body
c. Intussusception
d. Gastric dilatation and volvulus
Intussusception
Which of the following is not a benefit of FAST/POCUS in an ECC patient?
Select one:
a. It can confirm tempero- mandibular luxation
b. It can confirm the presence of free abdominal fluid
c. It can be performed at the patient’s kennel
d. The patient is not likely to require sedation
It can confirm tempero- mandibular luxation
Which contrast media would be the most appropriate for a patient with a possible gastro-intestinal tract perforation?
Select one:
a. Non-ionic, hypoosmolar iodine based
b. Air
c. Barium impregnated polyethylene spheres (BIPS)
d. Barium sulphate suspension
The correct answer is: Non-ionic, hypoosmolar iodine based
Reticulocytes are
Select one:
a. dying red blood cells
b. toxic neutrophils
c. immature red blood cells
d. active monocytes
The correct answer is: immature red blood cells
Which of the following assesses platelet function?
Select one:
a. Prothrombin time
b. Buccal mucosal bleeding time
c. Activated clotting time
d. Activated partial thromboplastin time
The correct answer is: Buccal mucosal bleeding time
Which of the following appears mainly anechoic on ultrasound examination?
Select one:
a. Bone
b. Liver
c. Bladder
d. Spleen
The correct answer is: Bladder
Which is the most accurate method of confirming hypoxaemia?
Select one:
a. Venous blood gas analysis
b. Pulse oximetry
c. Arterial blood gas analysis
d. Capnography
The correct answer is: Arterial blood gas analysis
Which statement is true?
Select one:
a. SpO2 should be < 90%. This equates to PaO2 < 60 mmHg
b. PaO2 should be > 94-95%. This equates to SpO2 > 80 mmHg
c. SpO2 should be > 94-95%. This equates to PaO2 > 80 mmHg
d. PaO2 should be < 90%. This equates to SpO2 > 80 mmHg
SpO2 should be > 94-95%. This equates to PaO2 > 80 mmHg
Which statement about a patient with hypovolaemia, secondary to splenic rupture, is true?
Select one:
a. An aural thermometer can be used to accurately measure core body temperature
b. It is at high risk of developing sinus arrhythmia
c. The PCV and total protein (TP) will be increased
d. Serum lactate levels are likely to be increased due to cell anaerobic respiration
Serum lactate levels are likely to be increased due to cell anaerobic respiration
Which statement is true?
Blood gas analysis, on a patient with metabolic acidosis, is likely to show …….
Select one: increased PaCO2 decreased HCO3- decreased lactate blood pH > 7.5
The correct answer is: decreased HCO3-
In which condition is the ‘double bubble’ a significant radiographic finding?
Select one:
a. Pneumothorax
b. Warfarin toxicity
c. Gastric dilation & volvulus
d. Hypertrophic cardiomyopathy
The correct answer is: Gastric dilation & volvulus
