1. Isovolemia, isoosmosis, PCV, ion concentration Flashcards
Serum vs plasma
Serum = plasma - clotting factors
If we add anticoagulant it’s plasma.
What is common anticoagulants for haematology?
- Na2- / K2- / NaK-ethylene-diamine-tetraacetic acid (EDTA) solution
How does EDTA work as anticoagulant?
by irreversibly binding calcium ions in the sample
Are biochemistry parameters usually evaluated in plasma or in serum?
Mostly in serum, without adding any anticoagulant
Tho sometimes also in plasma where coagulation is blocked by heparin
How does heparin work as anticoagulant?
Heparin enhances the binding of coagulation factors to antithrombin 3 -› blocks the conversion of fibrinogen to fibrin
Is heparin produced inside of the body too?
Yes. By mast cells. But in lab d we use synthetic heparin. Also it often has a nectotiying effect on WBCS in vitro
Which anticoagulant is used for testing blood clotting parameters?
Na2-citrate (3.8 solution)
How does Na2-citrate work as an anticoagulant?
- Calcium binding but comparing to EDTA here it’s REVERSIBLE.
- citrate causes the least damage to blood metabolism (=› blood smears, transfusion bags…)
What are clinical signs of volume disturbances?
- change of capillary refill time
- colour of mucous
- strength of pulse, heart rate, blood pressure
- change of skin turgor
- sunken eyes, prolapse of third lid
- changes of body weight
- volume of urine production
Up to how many % of blood loss there will be no change in blood pressure?
5-15%
What happens when blood loss is 15-25%?
• tachycardia
• vasoconstriction
• initially increase in blood pressure
What happens when blood loss is 35-45%?
• severe decrease of blood pressure
• oliguria/anuria
• vasodilation and shock
Packed cell volume (PCV) - ?
= hematocrit
Ratio of whole blood volume to the volume of RBCs
Anticoagulated blood is needed (EDTA, heparin)
What is physiological range for hematocrit?
35-45%
What are the ways to count hematocrit?
- Microcapillary tube method
- Automated cell counter
- HCT meter (also hemoglobin) (uses optical reflection)
How increase and decrease of hematocrit are called?
Decrease - oligocythaemia/anaemia
Increase - Polycythaemia
What can be reasons of physiological polycythaemia (increased hematocrit) ?
- species and breed characteristics (greyhound, whippet, borzoi, hot blooded horses)
- newborn animals
- long-term hypoxia (living in high altitude, regular intensive training)
What can be the reason of false polycythaemia?
long sample storage with EDTA. Corpuscular volume of RBCs increases
What is difference between relative and absolute polycythaemia?
Relative - decreased plasma volume (dehydration - lack of drinking water, vomiting, diarrhea)
Absolute - increased RBCs production
What can be reasons of absolute polycythaemia?
Primary: WITHOUT increase of erythropoetin (EPO) (e.g. bone marrow neoplasia)
Secondary: due to increased EPO
a) long-term hypoxia, physiological or due to chronic respiratory or circulatory diseases (brachycephal syndrome in dogs, RAO - reaccurent airway obstruction in horses, right-left shunt)
b) without hypoxia - autonomous increase of EPO (EPO producing tumor in kidney, liver)
What is erythropoetin and what is its function?
Erythropoietin (EPO) – hormone that stimulates production of erythrocytes in the bone marrow. EPO is produced mainly in kidneys but also in liver. Stimulates transformation of immature cells (proerythroblasts) to mature RBCs.
If O2 delivery is decreased, production of EPO by kidneys is increased
Chronic kidney disease -› low EPO -› anemia
What is the condition of physiological oligocythaemia (anemia) ?
Increased plasma volume in 3d trimester of pregnancy (relative anemia)
What is relative oligocythaemia (anemia)?
- due to increase of plasma volume
- pathological: overdose in fluid therapy, terminal chronic kidney insufficiency
Conditions of absolute oligocythaemia
- several hours after bleeding (plasma is replaced much faster)
-
decreased RBCs production
1. suppression of the bone marrow - heavy metal poisoning, mycotoxins, drugs side effect, viral infections
2. lack of materials needed for erythropoiesis - iron, copper, B6, B12, folic acid - decreased life-span of RBCs (immune-mediated haemolytic anemia (IHA), parasites
- sequestration of RBCs in the spleen due to hypersplenismus
What is color of plasma physiologically?
Transparent, colorless-yellowish
In horses plasma is yellowish due to high level of bilirubin.
In ruminants plasma can be yellowish if there is high carotenoid content in the feedstuff
What white, opaque plasma means?
Hyperlipidaemia or other lipid-metabolic disorders (DM, pancreatitis)
At what % of dehydration decrease of skin turgor is visible?
5-6%
Osmolality vs osmolarity
Osmolality - osmotic pressure per kg
osmolarity - osmotic pressure per liter
How can osmolarity be measured?
- mathematically ( = 2*(Na + K) + urea + glucose)
- using osmometr
What is mechanism of work of osmometer?
it measures freezing point of the sample and compares it to freezing point of water
What is osmolar gap and what can cause it?
difference between calculated and measured osmolarity.
—
can be caused by ethanol, ethylene-glycol, methyl-alcohol or isopropyl-alcohol in the blood
Main causes of hypernatremia
- water loss: decreased water intake, polyuria (e.g. diabetes insipidus), vomiting or acute diarrhea, panting
- increased Na retention in kidneys (primary hyperaldosteronism - Conn’s syndrome, secondary hyperaldosteronism - GCC therapy, liver desease, neoplasm)
- overdose of hypertonic solution, increased salt intake
Main causes of hyponatremia
- Na loss (GIT - diarrhea, renal loss - hypoaldosteronism (Addison’s desease), sweating (horses), sequestring in body cavities (ascites)
- excessive fluid intake, retention of water
How aldosterone affects K⁺ concentration ?
Excretion of K⁺ increases under aldosterone effect in the epithelial cells of the distal tubules via regulation of Na⁺/K⁺/-ATPase -› decrease of plasma K⁺ conc
How does insulin affect K concentration?
Insulin -> increased work of Na+/H+ anti porter -> increase of IC Na+ -> increased work of
Na+/K+/ ATPase -> increase of IC K+ = decrease of plasma K+
Insulin shifts potassium into cells by stimulating the activity of Na+-H+ antiporter on cell membrane, promoting the entry of sodium into cells, which leads to activation of the Na+-K+ ATPase, causing an electrogenic influx of potassium. IV insulin leads to a dose-dependent decline in serum potassium levels
Main causes of hypokalemia
- decreased intake (anorexia)
- long term polyuria, loop-diuretic drugs (furosemide)
- diarrhoea, enteral bleeding
- hyperaldosteronism (primary or secondary)
- alkalosis
- insulin (it induces cotransport with glucose into the cells)
Main causes of HYPERkalemia
- increased per os intake, overdose of potassium containing fluids
- acute kidney failure
- rupture of urinary bladder
- hypoaldosteronism (Addison’s disease)
- acidosis
- cell injury
When pseudohyperkalemia may occur?
In case of damage of tissue cells or RBCs (IC conc of potassium is high)
Alsosterone, its function and its effect on plasma electrolyte concentration
Aldosterone – steroid hormone produced by zona glomerulosa of adrenal gland and it acts on distal consulates tubule and collecting duct, stimulating expression of Na⁺/K⁺/-ATPase on the basolateral surface of the cells (pumping Na⁺ to the blood and K⁺ to the lumen) -› increased water reabsorption -› increased blood pressure, decrease of plasma K⁺ and increase of plasma Na⁺
Consequence of change in plasma potassium concentration
- change in either direction influences the conduction of neural stimuli. Muscle weakness
- muscle spasm can occur in case of hyperkalemia due to secondary hypocalcaemia
- hypokalaemia -> decreased neuromuscular irritability, paresis, glucose intolerance, decreased insulin secretion, decreased conductance of electrical stimuli in the heart, bradycardia, polyuria, polydipsia, sodium retention, alkalosis
What is reference range for plasma chloride?
100-125 mmol/l
Main reasons of hyperchloremia
- “salt poisoning”
- overdose in fluid therapy
- decreased excretion (hypoaldosteronism = Conn’s syndrome)
Main reasons of hypochloremia
- vomiting, diarrhoea
- sweating (horse)
- abomasal displacement
Role of calcium in the body
- maintenance of neuromuscular irritability
- initiation of muscle contraction
- regulation of cell permeability and irritability
- blood clotting process (factor 4)
- building and stabilising of bones and teeth
In what form Calcium is present in the body?
- bound to proteins (albumin)
- 45-50% free ionised form (Ca⁺⁺)
- chelated with organic acids
Reference range for calcium
2,1 - 3,0 mmol/l (Ca⁺⁺ is 45-50% of this).
In poultry laying eggs tCa (total Ca) can be even double (~5,8 mmol/l) but ionised fraction will be decreased
Main reasons of hypocalcaemia
- insuff. intake or absorption (vit D deficiency or its decreased activation can cause decreased absorption)
- hypofunction of parathyroid gland
- lactation
- toxicosis of calcium binding substances (citrate, oxalate, ethylene-glycol)
- alkalosis (Ca⁺⁺ decreases due to increased binding to albumin)
Main causes of hypercalcemia
- excessive Ca or vit D intake
- hyper A vitaminosis in cats
- hyperfunction of parathormone (also can be due to inflam. or neoplastic processes)
Role of magnesium in the body
- ATP metabolism (ATP is bound to Mg⁺⁺ within cells forming a complex)
- actin-myosin activator - maintains neuromuscular irritability
- catalysator for more than 300 enzymes
- facilitates synthesis and breakdown of acetylcholine
- antagonises acetylcholine receptors at the neuromuscular junction and blocks the sarcomere
Indications to check magnesium
- hypocalcemia of unknown origin (deficiency of Mg blocks PTH production and activity)
- hypokalemia which is resistant to supplementation
- DKA (diabetic keto-acidosis)
- muscle weakness of unknown origin
- tremor, seizure, arrhythmia
Reference range for magnesium
0,8 - 1,5 mmol/l
Main causes of hypomagnesemia
- decreased intake (grass tetany in cattle and sheep)
- lactation
- absorption disturbances or increased excretion
Role of inorganic phosphate in the body
- participant of many reactions (ATP, synthesis of sugar phosphates, freeing glucose from glucose-6-phosphate, phosphorolytic processes)
- buffer-system
Parathyroid hormone and its effect on concentration of electrolytes
Increased Ca⁺⁺ plasma level and decreased phosphate plasma level
1. Increased mobilisation of Ca⁺⁺ and Pi from bones
2. Increased Pi excretion (PCT, Na⁺/phosphate cotransporter) and Ca⁺⁺ reabsorption (DCT, principal cells, Na⁺/Ca⁺⁺) from kidneys
3. Helps to convert Cholecalciferol (precursors of vit D) to its active form vit D (Calcitriol) -› calcitriol acts on digestive system increasing Ca⁺⁺ absorption
Calcitonin and its effect of electrolytes plasma concentration
Calcitonin is hormone produced by parafollicular cells (C-cells) of thyroid hormone. Calcitonin decreases blood calcium in 2 ways
1. Inhibits octeoclasts -› decrease of plasma calcium concentration
2. Decrease of calcium and phosphate reabsorption by the principal cells in DCT (Na⁺/Ca⁺⁺ channels) -› increased phosphate and calcium excretion
decreased Ca⁺⁺ and phosphate plasma conc
Possible reasons for HYPOvolemic NORMOcythaemia?
Blood loss
Possible reasons for HYPERvolemic NORMOcythaemia
- chronic stress
- overdose on a full blood transfusion
How blood pH influences concentration of K+?
- more acidic pH increases potassium reabsorption as H+ ions get pumped out to antagonise the acidosis. higher the ph, higher K+ conc
- in alkaline environment hypokalemia may occur
How much of K+ is reabsorbed in kidneys usually?
90%
How much of Na+ is reabsorbed in kidneys usually?
60%
Grass tetany is related to deficiency of which ion?
Magnesium
Reasons of decreased blood phosphate concentration
- liver dysfunction
- hyperparathyroidism (PTH causes Ca absorption and phosphate excretion)
- calcitonin
- low pH (phosphate decreases, calcium increases)
