Lab 1 Homeostasis Flashcards
What anticoagulant is generally used for hematology and how does it work?
EDTA
Irreversibly chelates Ca2+
How are most blood biochemistry parameters evaluated?
In serum (blood is clotted) or heparinized plasma
How does heparin work on plasma?
Enhanced the binding of coagulation factors to antithrombin III which blocks the conversion of fibrinogen to fibrin
What type of heparin is used for electrolyte measurements?
Lyophilized, calcium equilibrated heparin
Which anticoagulant is used for the testing of blood clotting parameters and how does it work?
Na2-Citrate 3.8%
Reversibly chelates Ca2+
Also suitable for blood smear (low damage in blood cell metabolism)
Give the three water compartments in the body
Extracellular
Intracellular
Transcellular
What is the fluid in the water compartments influenced by?
Lungs, kidneys, skin, GI tract
Give total water content of the body
600-650 ml/BWkg
What two kinds of volume disturbances can be distinguished?
Perfusion and hydration disorders
How can you measure the water volume of each compartment in the body?
Not possible, but can be estimated based on some measurable parameters
What does a decrease of tissue perfusion mean?
Volume deficit in intravascular space
5 clinical signs to evaluate perfusion:
circulatory problems
Capillary refill time (CRT) Mucous membrane color Strength of pulse Heart rate Blood pressure (central venous pressure)
7 clinical signs to evaluate hydration
interstitial/intracellular water supply
Skin turgor (elasticity)
Mucous membranes
Sunken eyes, prolapse of third eyelid (cats
Eye turgor
Skin around oral cavity or anus
Body weight changes
Urine production, specific gravity of urine
What blood parameters can be used to evaluate volume disturbances?
PCV, Ht
Hb concentration
TP or Alb conc
Change in MCV of RBC (osmotic)
What happens at 5-15% loss of total blood volume?
No change in blood pressure
What happens at 15-25% loss of total blood volume?
Tachycardia, peripheral vasoconstriction, increased BP
What happens at 35-45% loss of total blood volume?
Severe BP decrease, oliguria and peripheral vasodilation - shock
What happens at 50% loss of total blood volume?
Death
What does Packed Cell Volume give information about?
The ratio of whole blood volume to the volume of red blood cells
What can be detected by PCV
Fluid volume changes and quantitative changes of RBCs
Give three methods to measure PCV
Microhematokrit/microcapillary method
Automated cell counter
Handheld HCT meter
Microhematokrit/microcapillary method
Blood into microcapillary, centrifuge, read result on Ht scale
Automated cell counter
ACC measure MCV and the number of RBCs
The machine automatically calculates the PCV
Handheld HCT meter
Measures Ht and total Hgb in whole blood
Species chip and test strip inserted into meter
Uses optical reflectance
Physiological Ht range for most species
0.35-0.45 l/l or 35-45%
Interpretation of PCV results
Decrease: oligocythaemia or anaemia
Increase: polycythaemia
Physiological polycythaemia
Congenital
Newborn
Physiological long-term hypoxia
Relative polycythaemia
Dehydration
Absolute polycythaemia
Primary/Secondary
Increased RBC production
Primary:
no increase in EPO
Bone marrow neoplasia, polycyt. absoluta vera
Secondary: because of increased EPO True: long term hypoxia (BOAS dogs, RAO, right-left shunt of heart) Not true: no hypoxia EPO producing tumour of kidney/liver
Complex polycythaemia
Hypervolaemic polycythaemia
Life threathening acute stress or extreme physical exercise - constriction of blood vessels and spleen
False polycythaemia
Long sample storage with EDTA
False oligocythaemia
Microcytosis
Physiological oligocythaemia
Increased plasma volume in the 3rd trimester
Relative oligocythaemia
Pathological increase in plasma volume (hyperhydration)
Iatrogen, terminal phase of chronic kidney insufficiency
Absolute oligocythaemia
After acute bleeding
Decreased RBC production:
Bone marrow suppression
(Heavy metal poisoning, mycotoxins, viral infections)
Deficiencies: Fe, Cu, pyridoxal, cobalamine, folic acid
Decreased lifespan in circulation: immune-med hemolytic anemia
Sequestration of RBCs in spleen (splenomegaly)
Complex oligocythaemia
Hypovolaemic oligocythaemia
Absolute oligocythaemia with vomiting/diarrhea
Additional information by examining blood in Ht tubes after centrifuging
Colour change of plasma
Buffy coat
Microfilaria larvae
Mention 4 color changes of plasma
- Reddish tint: hemolysis
- White/opaque: alimentary hyperlipidaemia
- Yellow: hyperbilirubinaemia (horse physiological, cattle b-carotene)
- Chocolate brown: methaemoglobinaemia
Buffy coat in Ht tube
WBCs
1-2 mm
Increase/decrease can be seen
Mild dehydration
<5% hardly detectable
5-6% skin turgor
6-8% enophtalmos, dry mucosa
Moderate dehydration
8-10% longer CRT, dry mucosa, enophtalmos, tachycardia, severe skin turgor
Advanced dehydration
10-12% signs of shock, disturbed consciousness
weak pulse, tachycardia, low BP, cold extremities
12-15% shock, life threathening
Common PCV lab errors
Improper mixing
Leak of RBC during centrifuging
Anticoagulant effect (clumping or swelling)
Serum osmolality
Osmotic pressure of body fluids expressed in kg
Depends on concentration of osmotically active substances: Na/K/Cl and urea, glucose and ketone bodies
What sample is used to measure serum osmolality
Heparinised plasma or serum
Methods to measure serum osmolality
Mathematical
Osmometer
Mathematical measurement of serum osmolality
2 (Na+K) + urea + glucose
Advantage: no additional equipment needed
Osmometer
Measures freezing point of sample compared to freezing point of water (0C)
Osmolar gap
Difference between calculated and measured osmolarity
Gives information about toxins
Hyperosmolarity
> 310 mOsm/kg
Concentrated EC fluids
Hypoosmolarity
<270 mOsm/kg
Diluted EC space
What can happen if we try to decrease blood glucose in advanced DM patients too quickly with exogenous insulin administration?
Rapid change in osmolarity
Hypophosphataemia, hypokalaemia
Cellular oedema in brain or lungs
What can increase osmolar gap?
Ethanol, ethylene-glycol, methyl-alcohol or isopropyl-alcohol in the blood
Electrolyte concentration
Sample
Ionogram
Heparinised whole blood
Ca2+: calcium ion-equilibrated Na- or Li- heparinate
Why not use Na/K EDTA for ionogram analysis?
Increases conc of Na/K and decreases Ca to zero
Na+
Reference range
What does it do
Conc depends on
140-150 mmol/l
Maintains plasma osmolarity: cannot move freely through biological membranes
Depends on intake, per os and IV Excretion: prox tubules: 60% reabsorbed Aldosterone effect Distal tubules Excretion of other osmotically active substances Sweating (horses)
Causes of hypernatraemia
1. Dehydration Decreased intake Polyuria (diabetes insipidus) Vomiting, diarrhea Hyperthermia, panting
- Na+ retention in kidneys
Primary/secondary hyperaldosteronism - Other
Hypertonic saline solution overdose
Salt poisoning
Causes of hyponatraemia
1. Water poisoning Per os (ru) Overdose of IV hypotonic fluid
- Retention of water
Cardiac insufficiency
Renal or hepatic insufficiency
3. Na+ loss Diarrhea Renal loss, hypoadrenocorticism Sweating Body cavity sequestration
- Water efflux from IC to EC
K+
Reference range
Conc depends on
3.5-5.5 mmol/l
Intake
Excretion (90% reabs)
increases in presence of aldosterone effect
Depends on pH
Insulin: cotransport of K+ with glucose into cells
7 causes of hypokalaemia
Decreased intake Long term polyuria Administration of loop-diuretic drugs Enteral potassium loss Primary/Secondary hyperaldosteronism Alkalosis Insulin
causes of hyperkalaemia
Increased intake Acute kidney failure Urinary bladder rupture Hypoaldosteronism (also hyperadrenocorticism) Acidosis
Pseudohyperkalaemia
Damage of tissue cells or RBS (necrosis, hemolysis)
ø Dogs
Why is the normal range of K+ narrow?
Because substantial change in either direction influences the conduction of neural stimuli
Muscle weakness
Cl-
Reference range
100-125 mmol/l
Most important anion of plasma (With HCO3)
Hyperchloraemia
Salt poisoning Decreased secretion (hyperaldosteronism) and other processes with hypernatraemia
Hypochloraemia
Abomasal displacement, vomiting, diarrhea, sweating and other processes with hyponatraemia
Major cations and anions
Cations: Na+, K+
Anions: Cl-, HCO3-
Anion gap
Other anions
Proteinate, phosphate, sulphate, lactate, oxalate, salicylate
Calcium
Role
Presence in blood plasma
Ionized: Ca2+, Total: tCa Neuromuscular irritability maintenance Muscle contraction initiation Cell membrane permeability regulation Blood clotting processes Bones and teeth
47% bound to albumins
40% free ionized form
13% chelated form (organic acids)
Calcium reference range
Egg-laying poultry
2.1-3 mmol/l (Ca2+ half)
Can be doubled (%decrease of ionized fraction)
tCa preferred sample
Ca2+ preferred sample
tCa: Serum
Ca2+: heparinized plasma
Ca2+ measurement
Ion-selective electrodes
tCa measurement
Spectrophotometry
Calcium forms violet complex in high pH with orthocresolphtalein
Neuromuscular irritability symptom, calcium test
Test for Ca2+ instead of tCa
Calcium binding substances getting into blood stream and bind ionized Ca2+
Hypocalcaemia
Insufficient intake or absorption (vit D)
Parathyroid gland hypofunction (Mg deficiency)
Lactating animals
Calcium binding substance toxicosis
Usually both low but:
Low Ca2+: caused by alkalosis (bound to albumin)
Hypercalcaemia
Excessive Ca/vit D intake
Hyper a vitaminosis (cats)
Parathormone hyperfunction
Causes damage to bones and soft tissue calcification
tCa can be influenced by
Plasma proteins
Chronic kidney insufficiency compensation
Constant calcium loss: hypocalcaemia
Compensation by PTH excretion
Secondary renal hyperparathyroidism and hypercalcaemia
Magnesium forms
Role
Reference range
tMg, Mg2+ ATP metabolism (bound to Mg IC) Actin-myosin activator Catalysator for more than 300 enzymes Facilitates synthesis and breakdown of ACh
0.8-1.5 mmol/l
Preferred samples:
tMg
Mg2+
tMg: serum or heparinized plasma
Mg2+ heparinised plasma
Mg Measurement
Mg2+: ion-selective electrodes (ISE) 70% of total Mg
tMg: Spectrophotometry with xylidine-blue reagent (purple complex)
Hypomagnesaemia
Grass tetany
Early spring grass, especially lactating
Muscle spasms, respiratory distress, death
Absorption disturbance
Increased excretion (renal/enteral)
Hyperthyroidism (also inc IC Mg storage)
Hypermagnesaemia
Increased intake Decreased excretion: chronic insufficiency milk fever hypothyreosis Hyperadrenocorticism Dehydration
Inorganic phosphate
What does it do
Reference range
Product, reaction partner and a source of several synthetic, transitional and breakdown processes (ATP, sugar phosphate, glucose-6-P) Plasma buffer systems Eq/Ca: 0.8-1.8 mmol/l Fe/Bo/Ov: 1-2.4 mmol/l Su/Cap: 1-3 mmol/l
Pi sample and measurement method
Sample: Serum/heparinised plasma
Spectrophotometry
Acidic: phosphorus reacts with ammonium-molybdate and forms yellow complex
PTH effect
Induces phosphate and calcium mobilization from the bones and increased Pi-excretion and Ca-reabsorption through kidneys. Net effect: decreased Pi and increased Ca in plasma
Calcitonin effect
Increases calcium and phosphate absorption from intestines and their incorporation into the bones. Net effect is decreased Pi and Ca conc in the blood.
Decrease of plasma Ph causes a decrease in Pi-conc and an increase in Ca2+ level (tCa no change)
