Lab 1 - HOMEOSTASIS - CHANGES OF ISOVOLAEMIA, ISOIONIA AND ISOOSMOSIS

Question 1

How can we use clinical signs to evaluate the perfusion(volume-disturbances), and what problems cause this

Answer 1

Problem: intravascular deficit or circulation problems

capillary refill time (CRT) (hypovolaemia, hypervolaemia)

colour of mucous membranes (e.g. pale, livid)

strength of pulse

(No proper heart function, no perfusion -> dehydration)

• heart rate (will increase in case of both hyper- and dehydration! To incr bp or resistsnce))
• blood pressure (central venous pressure)

Question 2

How can we use clinical signs to evaluate the hydration(volume-disturbances), and what problems cause this

Answer 2

Problem: interstitial or intracellular water supply

• skin turgor (elasticity) – pulling up to form a wrinkle
• mucous membranes – e.g. shiny, wet or dry
• sunken eyes (enophthalmos), prolapse of the third eyelid
  especially in cats
• turgor (elasticity) of the eye
• skin around the oral cavity or anus – signs of water loss changes of body weight (can be measured in hospital setting)
• volume of urine production, specific gravity of urine

Question 3

Name the 5 ways of evaluating the volume-disturbances

Answer 3

1. Based on clinical signs:
2. Based on packed cell volume (PCV, haematocrit - Ht)
3. Based on haemoglobin (Hb) concentration
4. Based on plasma total protein (TP) or albumin (Alb) concentration
5. Based on change in Mean Corpuscular Volume of the RBCs (MCV), influenced by osmotic state

Question 4

Laboratory signs of hyperhydration - general change

Answer 4

You will only see symptoms when the hyperhydration is very severe!

Question 5

(PQ)Difference between laboratory and clinical signs in case of dehydration and hyperhydration

Answer 5

Clinical: skin tent, mucous membrane, capillary refill time

Laboratory: pack cell volume, TPc, MCV

Question 6

Pcv

Answer 6

Packed cell volume - ratio of whole blood Volume/RBC Volume

-volemia and -cythemia

Question 7

Causes of normal PCV - normocythaemia

Answer 7

1️⃣ normocythemia + normovolemia: normal
2️⃣ normocythemia, hypovolemia: acute blood loss,
3️⃣ normocythemia + polycythemia: overdosing of full blood transfusion, chronic stress (usually with high blood pressure)

Question 8

Causes of increased PCV (polycytaemia):

Answer 8

1️⃣ False: long sample storage with EDTA (first clump together, later the rbc swell(macrocytosis)
2️⃣ physiological: (normovolemic polycythemia)
o Congenital: species and breed characteristics: lama, yak, greyhound, whippet, borzoi dogs, hot blooded horses
o Changes related to age: new borne animals
o Physiological long-term hypoxia: living in high altitude, regular intensive long
training or work e.g. sled dogs (normovolaemic polycythaemia)
3️⃣ Relative polycytaemia: decreased plasma volume (dehydration – hypovolaemic polycythaemia) e.g. lack of drinking water, vomiting, diarrhoea
4️⃣ Absolute polycythaemia (normovolaemic): increased RBC production
• Primary: without increased erythropoietin (EPO) (bone marrow neoplasia -
polycythaemia absoluta vera i.e. chronic leukaemia of RBCs)
• Secondary: due to increased EPO
a. true: caused by long term hypoxia (can be physiological - see above: low atmospheric O2, training) due to chronic respiratory or circulatory disorders e.g. brachycephal syndrome in dogs, ROA – recurrent airway obstruction in horses, right-left shunt in the heart (shunt: a hole or a small passage which moves, or allows movement of, fluid from one part of the body to another)
b. not true: without hypoxia: autonomous increase of EPO (EPO producing tumour of the kidney, liver)
5️⃣ Complex problem: hypervolaemic polycythaemia – life threatening acute stress or extreme physical exercise (concurrent constriction of blood vessels and the spleen)

Question 9

Causes of decreased PCV (oligocythaemia = anaemia):

Answer 9

1️⃣􏰀 False: microcytosis (decreased RBC volume), inappropriate sample mixing, red blood cells (RBCs) may leak out during centrifuging, Microcytosis
􏰀2️⃣Physiological: incr. plasma volume in the 3rd trimester of pregnancy (this is also relative hypervolaemic oligocythaemia!)
􏰀3️⃣Relative: pathological increase in plasma volume (hyperhydration – hypervolaemic oligocythaemia) i.e. overdose of fluid therapy, terminal (oliguric/anuric) phase of chronic kidney insufficiency
􏰀4️⃣Absolute: these are normovolaemic oligocythaemias
• several hours after acute bleeding (replacement of plasma is much quicker than
replacement of cells)
• decreased red blood cell production
a. suppression of the bone marrow e.g. heavy metal poisoning, mycotoxins, drug side effect (e.g. chemotherapeutic agents), viral infections (e.g. parvovirus)
b. lack of some nutrients e.g. iron, copper, B6, B12 vitamins, folic acid
• decreased life-span in circulation e.g. immune-mediated haemolytic anaemia
(IHA)
• sequestration of RBCs in the spleen due to hypersplenismus
􏰀5️⃣Complex problem: the absolute oligocythaemias listed above frequently cause refusal of water, vomiting or diarrhoea leading to hypovolaemic oligocythaemia

Question 10

Serum Osmolality: what is it, normal value, how is it measured

Answer 10

expresses the ion balance of the serum(osmotic pressure)
➢ Physiological value is 270-300 mOsm/kg
➢ It is measure via ion-selective electrodes, an osmometer or
calculated [(2Na +K) + urea + glucose].

Question 11

Osmolar gap

Answer 11

is the difference between measure and

calculated osmolality. Safe range is +/-10.

Question 12

Interpretation of osmolality:

Answer 12

Changes can cause the swelling or shrinking of cells.
Rapid changes can have serious consequences e.g. in advanced Diabetes mellitus, trying to decrease the blood glucose too quickly can lead to hypophosphatemia, hypokalemia and cellular oedema.

Question 13

Osmotic changes in Dehydration

Answer 13

Isotonic:
➢ Blood/plasma loss
➢ Vomiting, diarrhoea
Hypertonic:
➢ Diarrhea, hyperventilation
➢ Fever, ADH function loss 
Hypotonic: 
➢ enhanced sweating in horses ➢ hypoadrenocorticism

Question 14

Osmotic changes in Hyperhydration

Answer 14

Isotonic:
➢ Enhanced water and salt intake
Hypertonic: 
➢ Salt poisoning
➢ hyperaldosteronism 
Hypotonic:
➢ water poisoning
➢ increased ADH function

Question 15

Goal of ionogram measurement

Answer 15

measure the electrolites and CO2

Differ btw fluid types - different processes need different osmotic environments for eg. Enzymes to work etc.

Question 16

Why can we not use ca-heparin, na-edta or k-edta in ion measurements? And in which way does the correct sample type have to be treated?

Answer 16

• ca-heparin incr the ca conc
• Na or K EDTA incr the conc of Na and K, but lowe the conc of Ca to sero

non electrolite equilibrated Na or Li heparinsed syringe decrease the ca concentration, so the correct sample type is Ca2+ equilibrated Na or Li heparinated syringe

Question 17

List the methods used to examine ion concentration

Answer 17

Ion selective electrodes(blood-gas analyser) for serum or plasma(ionized not total!!) Na, K, Cl, Ca and Mg - CO2

spectophotometry is used to measure the total concentration! Not just ionised
- Dietary, enteral, hormonal, paraneoplastic effects and excretion via the kidney can influence the concentration of both forms of calcium in the bloodstream. For this reason mostly the measurement of tCa is recommended

Question 18

What is Plasma K+ concentration is influenced by

Answer 18

1. Intake
2. excretion
3. transport mechanisms :
   - between the EC and IC space (Na+/K+ and H+/K+ ion pumps)

Narrow range as it is needed for the conduction of neural stimuli.

Question 19

Hyperkalaemia causes and consequenses

Answer 19

Causes:
➢ Increased intake
➢ Overdoes of K+ containing fluids
➢ Acute kidney failure, rupture of urinary bladder
➢ Hypoaldosteronism (aldosterone incr renal K exretion),
hypoadrenocorticism(aldosterone synth), acidosis(K+ goes out of cells in exchangr for H+)

Consequences:
➢ Muscle weakness and spasm (K conc EC should be low during mm contractions to incr the outside positive charge- na/k pump!)

Question 20

Hypokalaemia causes

Answer 20

Causes:
➢ Decreased intake
➢ Chronic kidney insufficiency, polyuria(incr urine prod)
➢ Loop diuretic drugs(incr na and water retentiin, incr K excretion in return)
➢ Enteral K+ loss – diarrhea, bleeding: (Loss of potassium depletes intracellular stores, leading to transfer of sodium from the extracellular to the intracellular fluid and generating hyponatremia coupled with hypokalemia.)
➢ Hyperaldosteronism (lead to lowered levels of potassium in the blood (hypokalemia see last!) and increased hydrogen ion excretion (alkalosis)
➢ Insulinoma, insulin overdose, incr insulin conc in plasma stim sodium reabs)

Question 21

Consequences of Hypokalaemia

Answer 21

➢ Muscle weakness (need k for mm contraction) paresis(weakness or voluntary movement)
➢ Decreased neuromuscular irritability(na/k pump)
➢ Glucose intolerance, decreased insulin secretion - see above
➢ Polyuria, polydipsia(incr thirst)
➢ Na+ retention as k conc goes down
➢ Bradycardia (decr heartrate)

Question 22

Hypernatreamia causes (and Cl-)

Answer 22

➢ Increased water loss or decreased water intake (dehydration) (if sodium in excess its excreted and water follows)
• decreased intake (lack of thirst or no drinking water available)
• polyuria e.g. diabetes insipidus (loss of water via the kidneys)
• vomiting or acute diarrhoea (water loss via the GI system)
• hyperthermia / enhanced panting (water loss via the resp. system)
➢ increased Na+ retention in the kidneys
➢ primary hyperaldosteronizmus (Conn’s
syndrome)
➢ secondary hyperaldosteronism
(Physiological activation of the renin-angiotensin-aldosterone system: glucocorticosteroid therapy(glucose), liver disease(glucose), neoplasm in liver eg.)

➢ overdose of hypertonic salt solution
➢ increased intake of salt (“salt poisoning”)

Question 23

Hypernatreamia consequenses (and Cl-)

Answer 23

➢ diabetes insipidus
➢ salt poisoning
➢ thirst

Question 24

Hyponatreamia causes (and Cl-)

Answer 24

➢ excessive fluid intake - “water poisoning”
- per os possible in ruminants
- overdose of hypotonic fluid e.g. iv
➢ Retention of water
- cardiac insufficiency: weak heart pumps less blood to your kidneys and causes fluid and water retention
- advanced renal or hepatic insufficiency
➢ Enhanced Na+ loss
- gastrointestinal (diarrhoea)
- renal loss – also hypoadrenocorticism
(Addison’s disease)
- sweating (in horses mainly)
- sequestration in body cavities (e.g.
ascites)
➢ Water outflux from the IC to the EC space
- Hyperosmolality

Question 25

Hyponatreamia consequenses (and Cl-)

Answer 25

➢ water poisoning

Question 26

What is Plasma K+ concentration is influenced by

Answer 26

Na+ is the main ion of the EC space.
Plays an important role in maintaining plasma osmolality, because water molecules move freely through biological membranes, but sodium ions can only be transported from the IC to the EC space only through Na+/K+ ion pumps. Water follows sodium.

Question 27

Chloride is an important anion of the plasma, give the causes and consquenses for Hyperchloraemia

Answer 27

Causes:
➢ Excessive salt intake
➢ IV overdose fluid therapy
➢ Decreased excretion (hyperaldosteronism) ➢ Hypernatraemia links
Consequences: ➢ Thirst

Question 28

Chloride is an important anion of the plasma, give the causes and consquenses for Hypochloraemia

Answer 28

Causes:
➢ Abomasal displacement caused by filling up with gas etc, leading to hypochloremia
➢ Vomiting, diarrhea, sweating
➢ Hyponatreamia links as they are casued by similar things eg dehydration

Consequences:
- None?

Question 29

Role of calcium

Answer 29

role in the maintenance of neuromuscular irritability, initiation of muscle contraction, regulation of cell membrane permeability and irritability, in blood clotting processes (e.g. IV. factor) and the building and stabilizing of bones and teeth (calcium is also stored in bones).

Question 30

Hypercalemia:
Causes:

Answer 30

➢ excessive Ca2+ or vit D intake(vit D incr serum calcium)
➢ hyper A vitaminosis in cats: incr bone building (ca reabs)
➢ hyperparathyroidism - PTH release calcium from bone
➢ different cancers (primary hyperparathyroidismus, aka a paraneoplastic syndrome. caused by ectopic parathormone activity or production of parathormone-like substances by neoplastic cells)

Question 31

Consequences of Hypercalemia

Answer 31

➢ lethargy: weakness (bind troponin),

➢ vomiting, constipation: Dehydration makes it hard for the kidneys to remove calcium from the blood.

Question 32

Hypocalemia:
Causes:

Answer 32

➢ insufficient Ca2+ or vit D intake 
➢ hypoparathyroidism (due to eg Mg def.)
➢ lactating animals: milk prod
➢ chronic kidney insufficiency
➢ alkalosis: ca decreases due to tp proteins of blood are ionised into anions during incr pH, so ca will be bound to albumin

Question 33

Consequences of Hypocalemia

Answer 33

➢ restlessness, muscle tremor, seizures (decrease of the ionized fraction cause decr muscular irritability)
➢ incorrect bone and teeth formation
➢ bone fractures

Question 34

What does the blood parameter of calcium show us

Answer 34

The mesured ca in blood at any point is the cumulative result of many regulatory processes.

• if ca loss on kidney it will show in the blood parameters!
• also the compensatory processes eg. Renal exretion/absorption, intestinal reabsorption, ca from bone etc. will be reflected in blood parameters

Question 35

Calcium binding substances

Answer 35

proteins that participate in calcium cell signalling pathways by binding to Ca2+

• muscle function, homeostasis, learning, memory etc. All aspects of cell function!
• these proteins may get into the blood and bind calcium incr eg. The muscular irritability!

Question 36

Corrected tCa

Answer 36

Some Ca is bound to plasma proteins eg. Albumin so the change in eg slbumin conc will influence the tCa while Ca2+ remains stable so there is no hyper or hypocalcemia even though the tCa is changed. Here we need to correct the tCa

Question 37

Processes influencing ca conc of plasma how

Answer 37

Depending on which compensatory process is currently most active the measured plasma calcium may show hypo-, normo- or hypercalcaemia.

Question 38

Hypermagnesia: Causes:

Answer 38

➢ Increased intake – iatrogenic
➢ Increased absorption – after laxatives
➢ Decreased excretion – milk fever,
hypothyroidism (Milk Fever. Milk fever is a metabolic disorder caused by insufficient calcium, Magnesium is required for the production of hormones that are important for the absorption of calcium (Ca)from the gut and the mobilisation of Ca from bones)
➢ Dehydration

Question 39

Hypermagnesia: Consequences:

Answer 39

➢ Muscular weakness, paralysis (Mg - Ca)

➢ milk fever

Question 40

Hypomagnesia: Causes:

Answer 40

➢ Decreased intake – grass tetany(wrong feed)
➢ Lactating animals: loss of Mg in milk
➢ Absorption disturbances
➢ Increased excretion – diarrhoea,
hyperthyroidism: metabolic disorders

Question 41

Hypomagnesia Consequences

Answer 41

➢ hyperexcitability, tetany(nerve transmission and mm contration)
➢ spasms, collapse, convulsions
➢ respiratory distress
➢ death

Assists in many essential cellular reactions!!

Question 42

Role Mg

Answer 42

Role in ATP metabolism: ATP is bound to Mg2+ within the cells forming a complex

actin-myosin activation: maintains neuromuscular irritability

catalysator of many enzymes

It also facilitates the synthesis and breakdown of acetylcholine.

Question 43

Why do we measure Mg

Answer 43

hypocalcaemia of unknown origin (deficiency of Mg2+ blocks PTH production and activity)

hypokalaemia (which is resistant to supplementation)

DKA (diabetic keto-acidosis), muscle weakness of unknown origin, tremor, seizure, dysphagia, dyspnea and arrhythmia.

Question 44

Pi content of plasma is influenced by

Answer 44

• intake, increases when meat or grains are fed.
• rate of absorption is important – increases under vitamin D effect and decreases in vt D deficiancy
• Metabolic utilisation: young animals, pregnancy, egg prod - growth!
• liver function (vit D function is dep on liver)
• kidney function: excretion
• incr renal excretion of PTH: primary and secondary hyperparathyroidism
• hyperthyroidism the PTH excretion is decreased so Pi excretion also decreases
• bone Pin mobilisation eg bone tumors incr plasma Pin (osteolysis)

Question 46

Alterations of PCV can be caused by

Answer 46

Lab errors:

1. improper mixing of the blood sample before filling the microcapillary tube(ht higher at bottom)
2. Rbc leak during centrifugation, low ht
3. Anticoagulant effect: EDTA initially may clump RBCs thus lowering the PCV, later after 12-24 hours they may swell increasing the PCV.
4. oligocythaemia the swelling of the RBCs (􏰅 MCV) may falsely produce normal PCV, on the other hand normal count of small size RBCs can produce low Ht

Question 46

Additional information gained by examining blood on Ht tubes after centrifuging:

Answer 46

1. Colour change of plasma: physiologically is transparent and depending on species can be yellowish or colourless like water.
2. Buffy coat. On the top of the RBC layer the white blood cells (WBCs) form a white(ish)
3. Microfilaria larvae (Dirofilaria immitis or repens). On the top of the buffy coat layer microfilaria larvae sometimes can be visible as delicate filaments

Question 47

Pathological color changes of plasma

Answer 47

➢ Reddish tint is seen in haemolysis. This can be intravascular haemolysis or due to error in sampling or sample handling/storage.
➢ White, opaque colour indicates alimentary hyperlipidaemia or other lipid-metabolic disorder (e.g. diabetes mellitus, pancreatitis.
➢ Strong or dark yellow colour is a sign of hyperbilirubinaemia (>30 μmol/l). In horses normal plasma is yellowish, since physiological blood bilirubin level is high (about 45
μmol/l). In ruminants yellowish plasma is seen if there is high carotenoid (especially