CRS 6 Flashcards
1
Q
Discuss the uses and limitations of the laboratory techniques available for demonstrating the parasite
A
- Heartworm and MFF antigen tests: antigen test takes 7 months do give positive result. Only means infection has occured at some point
- Thoracic radiological examination: can predict stage of infection and find thromboembolism, can see infiltration of vessels by worms
- Echocardiogram may show rigth ventricular dilation and wall hypertrophy, parallel linear echodensities produced by worms may be detected in right ventricle, right atrium and pulmonary artery
- ECG usually unremarkable
- ELISA: positive means must be a recent infection
- Tracheal washes show parasites up the parasites themselves
2
Q
Discuss the approaches to treatment and prophylaxis of Dirofilaria immits
A
- Kill both adult worms and MFF
- Prevent transfer to adult dogs
- To kill adult worm immiticide and caparsolate useful
- Dead worms may induce significant immune reaction
- Surgical removal may be necessary (caval syndrome)
- MFF can be killed using ivermectin, milbemycin
- Both can be used as prophylactics
- Ivermectin as heart guard and milbemycin as interceptor
3
Q
Explain the clinical relevance of vascular parasites
A
- Catastrophic effects
- Rapid decline and death
- Immune inflammatory response that can cause more damage than parasite itself
- May also be opportunity for parasite to reach brain and reduce blood flow to the area
4
Q
List important epidemiological factors in lungworm disease of dogs
A
- Poorly understood
- Sligs and snails appear to be vectors for parasite when ingested by dog
- Transmission also associated with kennels and travelling
- Can be transferred dog to dog (Angiostrongylus vasorum)
5
Q
List importnat epidemiological facotrs of lungworm disease of cattle
A
- Dictyocaulus viviparus
- Calves and yealings turned out to pasture fist time
- Later half of first grazing season
- Cattle on permament pastures used for seasonal grazing in EU affected
- Develop immunity following infection
- Must be mainteined by exposure each year
- Hypobiosis of late larval stage has been demonstrated in adult cattle
- L3 larvae may overwinter on pasture in enough numbers to cause disease following spring
6
Q
List important epidemiological factors of lungowrm in horses
A
- Dictyocaulus arnfieldi
- Mainly when pastures shared with donkeys
- When field previosuly used for donkeys
- Not persistent infection in horses
- Patency lower than that in horses
7
Q
Suggest relevant diagnositc tests for lungworm
A
- Clinical signs
- Faecal egg count
- Bronchoalveolar lavage
- Tracheal wash
- Endoscopy
- Post mortem
- Biopsy
8
Q
Compare the immune response to Angiostrongylus in dogs and Dictyocaulus in cattle
A
- Eosinophils, neutrophils, mast cells and basophils
- Immune responses different due to genetic variation between species of parasite and host
- Immune response to an occult infection also different to an adult infection
9
Q
Explain the variation in immune response reflecting in clinical signs of angiostrongylosis in dogs
A
- Clinical signs include coughing, dyspnoea, haemorrhage, pulmonary hypertension, lethargy, exercise intolerance, collapse, neurological signs, ocular signs, lumbar pain or no clinical signs
- Adult antigen causes type III hypersensitivity, dissemination of immune complexes, complement activation and immune infiltrate in the lungs and other tissues
- Egg deposition or L1 can cause pulmonary inflammatory/granuloma and pulmonary arteriolar vasoconstriction
10
Q
Outline ways in which parasitic diseases may be transmitted
A
- Vectors
- Ingestion
- From individual to another individual
- From parasite laying eggs in animal
11
Q
List some importnat taxonomic features which enable parasite identification
A
- Gross morphological structure of adults and eggs
- Plugs?
- Smooth or rough shell
- Thin or thick shell
- Parasite visible in egg?
- Colour?
- Size?
- Where found?
12
Q
Describe the life cycle of some respiratory parasites in exotic species
A
- Snake lung worm (Pentasmid) migrate as larvae from intestinal tract and then as adult to lungs
- Common intermediate hosts include insects and rodents
- Ivermectin common treatment but cannot be used for turtle
13
Q
Discuss some methods used to diagnose respiratory parasites of exotic species
A
- Clinical signs and history
- What kind of feed
- Contact with other animals
- Faecal egg count
- Identification of eggs under microscope
- Post mortem
- ELISA
- Biochemical tests
- Complete blood count
- Blood smear
14
Q
Define an acid
A
A proton donor (increases H+ concentration in a solution)
15
Q
Define a base
A
A proton donor and decreases H+ concentration in solution
16
Q
Define the term pKa
A
- Negative log of Ka
- pKa = pH at which 50% of molecules are ionised
- Greater pKa = lower dissociation and weaker acid
17
Q
Define Ka
A
- Dissociation constant
- Ka = [H+][A-]/[HA]
- Stronger acid has a higher Ka
- Strong acid gives Ka>1, pKa
18
Q
Define the term buffer solution
A
- Buffer solution is one that resists a change in pH by accepting or donating protons
19
Q
Define pH
A
pH = -log10[H+]
20
Q
State the Henderson-Hasselbach equation and use it to calculate the pH, pKa or [base]:[acid] ratio in a budder solution when given appropriate information
A
- pH = pKa + log ([A-]/[HA])
- Many drugs are weak acids or bases
- Un-ionised drugs cross membranes and enter blood stream more easily
- Environment will impact upon ratio of ionised to un-ionised
- Drugs work bes aroun 1pH of their pKa
21
Q
Explain the need for biological buffer systems
A
- Need to balance daily input/output of H+ in order to maintain steady state
- Metabolism of fat and carbohydrates produces H+ ions
- CO2 combines with water to form carbonic acid
- Buffers present damage occuring through produciton of waste products
22
Q
List the different types of acid in the body and give examples for each
A
- Volatile acid: an acid that can leave solution and enter the atmosphere e.g. carbonic acid in the lung, broken down to CO2 and H2O
- Fixed acids: cannot leave solution and must be eliminated by the kidney e.g. phosphoric acid
- Organic acids: by-products or participants in aerobic metabolism e.g. lactic acid
23
Q
Outline the mechanism of action of a buffer
A
- Able to accept or donate protons
- Weka acids or bases exist at equilibrium with the conjugate
- Resist changes from a stronger solution when added
- Compounds with pKa values in range of 6.4 - 8.4 most useful
- Curve is sigmoidal
- At pH associated with mid range has greatest buffering capacity
- For each buffer, best capacity extends 1pH unit either side of pKa
- Can act as open or closed systems
- Buffers can be proteins, phosphate, carbonic acid, hydrogen, carbon
- Can also be grouped by location - intracellular (proteins and phosphates) or extracellular (bicarbonate and Hb)
24
Q
List locations of biologially important buffers and give the components
A
- ISF: bicarbonate, phosphate, protein
- Blood: bicarbonate, haemoglobin, plasma protein
- ICF: proteins, phosphate
- Urine: phosphate, ammonia
- Bone: Ca carbonate
25
Q
Describe protein buffers
A
- Action depends on ability of amino acids to respond to pH change by accepting or releasing H+
- Increase in pH, carboxyl group (-COOH) releases H+, acting as a weak acid
- Becomes carboxylate ion (-COO-)
- At normal pH, proteins negatively charged and H+ already lost
- Histidine and cysteine are important donors
- R groups contain an imidazole ring, can donate H+ if pH climbs too high
- Albumin contains more histidine residues than globulin
- Histidine can be donor or acceptor at physiological pH
- pH decreases, carboxylate ion and amino group act as weak bases and accept
- Forms amino ion and carboxyl group
- Only free amino acids have free carboxylate ions and amino groups
- All amino acids have at least 2 titrable protons therefore 2 pKa values
26
Q
Indicate the major buffering systems present in mammalian blood and understand the role played by CO2 and haemoglobin
A
- Haemoglobin, bicarbonate, plasma protein
- Hb is main one, intracellular
- RBCs tighlty packed with Hb, cytoplasm contains carbonic anhydrase
- Hb rich in histidine residues
- Deoxygenated blood better buffer than oxygenated
- Imidazole group dissociates less when Hb oxygenated
- Hb allows exposed or free amino groups and as a resul, Hb can combine with H+ ions
- Reduces concentration of free H+ ions = buffer
- Hb plays secondary role supporting the carbonic acid - bicarbonate system in the plasma
- Increase H+ leads to lower affinity of Hb for oxygen
- Hb will unload oxygen more readily in capillaries of metabolically active tissues liberating H+ ions and CO2
- Contribute to more acidic pH environment
27
Q
Describe the bicarbonate buffer system in the ECF
A
- Most important
- Open system
- pKa is 6.1, poor buffering at normal blood pH of 7.4
- As is open system, still very effective
- CO2 dissolves in water, catalysed by carbonic anhydrase
- CO2 +H2O H2CO3 (H+) + HCO3-
- If CO2 levels increase, level of bicarbonate stays stable so pH drops significantly
- CO2 can be breathed off in open system
28
Q
Explain and compare methods for the evaluation of ventilation and lung function including arterial blood gas analysis and capnography
A
- Ventilation assessed using capnography, observation of the thorax, observation of bag movement (GA), using a ventilometer of respirometer
- Blood oxygen can be assessed byestimation from mucous membranes, pulse oximetry or blood gas analysis (pressure exerted on blood by oxygen in the plasma)
- Oesophageal manometry can also be used to assess pleural function
29
Q
Explain the purpose of capnography and how it can be used
A
- Shows ventilation, amount of CO2 produced, crude estimmate for cardiac output, metabolism and integrity of other equipment
- Goot alternative to blood gas analysis - measure CO2 breathed out
- Straight from systemic circulation so is accurate and non-invasive
- Normal circumstances, metabolic rate doesnt alter much
- Ventilation determines arterial CO2
- CO2 very soluble so Co2 in alveolar space good approximation of arterial CO2
30
Q
Describe how pulse oximetry works
A
- Beams of lgiht shone through capillary beds at 2 different wavelengths
- Oxyhaemoglobin and reduved haemoglobin absorb light at different rates
- Makes it possible to work out percentage saturation of oxygen
31
Q
What are the advantages and disadvantages of pulse oximetry?
A
- Advantages: non-invasive, fast result
- Disadvantages: oxygen carrying capacity cannot be determined, not accurate with assisteed oxygenation and smoke inhalation, affected by tongue colour and drugs administered e.g. vasoconstrictive drugs
32
Q
Describe methods for assessment of direct arterial blood pressure
A
- Doppler blood flow probe: hear blood flow, ultrasound bounces off moving structures, reflected frequency made audible, done over clipped artery
- Doppler sphymomanometry: detects presence of flow in distal artery, cuff inflated proximal to flow detector to pressure whcih exceeds systolic arterial pressure. Flow stops. Gradually decrease pressure within the csss and pressure at which flow first returns to heart is systolic presure
33
Q
Describe methods for the assessment of venous pressure
A
- Pressure of blood returning to the right side of teh heart
- Usually reflects volume of blood returning
- Long cannular insterted through jugular into vena cava
- Can be connected to a transducer and oscillometer to get automated trace
- Manometer should be zeroed to right side of heart
- Extension tube filled with fluid so changes in pressure are visible
- Can see if heart is functioning properly and can cope with blood returning to heart
- Can show if there is adequate circulating volume
- In hypovolaemic animal, movement of water in extension tube will be below 0cm
34
Q
Describe the methods for assessment of cardiac output
A
- Mostly in horses under anaesthesia
- Inject very cold water and measure change in temperature as it travels across the heart
- Lithium and dyes can also be used to measure the amount of blood that has passed through the heart
- ECG can also show if there is normal rate and rhythm but not cardiac output (but abnormal rate and rhythm will affect cardiac output)
35
Q
Discuss advantages and disadvantages of monitoring cardiorespiratory function late in the chain
A
- Later measurement, reflects things that happen earlier
- Oxygenation of arterial blood in tissue reflects blood pressure, heart function, lung function and breathing
- Advantage: can be sure whole system is working
- Disadvantage: if something is wrong do not know where
- Measure oxygen delivery by tissue perfusion or blood oxygen content
36
Q
Explain why it is importnat to measure teh mean arterial pressure and outline how this can be done
A
- MAP drives tissue eprfusion
- Low MAP = low perfusion
- If tissues themselves are constricted then increasing pressure will have no effect
- Measure MAP by feeling pulse (not very accurate but if can feel a strong pulse then usually adequate)
- Invasive measurement (cannula in artery)
- Non-invasive e.g. pressure cuff
37
Q
Describe the causes of hypoxia
A
- Problems in uptake of oxygen in arterial blood
- Impaired ability to carry oxygen in blood
- Impaired ability of blood to get to tissues
- Impaired ability of oxygen to get off Hb
- Uptake hypoxia can be caused by things that reduce normal oxygen transfer to arterial blood, low inspired oxygen and high alveolar carbon dioxide
38
Q
Describe the causes of hypercapnia
A
- Can occur when ventilation is not same as respiratory effort or breathing rate
- Negative pCO2 indicates something is wrong, lowers pH, promotes dysrhythmias and is ultimtely fatal
- Hypercapnia leads to hypoxia
39
Q
What is the normal pH of blood
A
7.4
40
Q
What is the normal pCO2
A
40mmHg
