The document discusses principles of acid-base balance in veterinary practice. It covers topics like water balance, electrolytes, acid-base balance, renal functions, fluid compartments, fluid therapy, dehydration assessment and treatment, electrolyte imbalances, and commercially available fluids. Key points include the importance of water and electrolytes for life, roles of kidneys and blood in acid-base balance maintenance, classification and assessment of dehydration severity, and fluid therapy considerations like cause, degree of dehydration, and patient condition.

1. PRINCIPLES OF ACID BASE BALANCE in
veterinary practice.
Presented by
Dr. SINDHU .K,
MVSc Scholar,
Dept of VPT, COVAS.

2. Water balance
• Next to oxygen, water is most important for life.
• Water & solutes (electrolytes & non-ionized organic molecules)
constitutes body fluids, which are essential various physiological
processes and maintenance of homeostasis.
• Under normal steady state conditions, the fluid intake is carefully
matched by equal output from the body to prevent body fluids
volumes from increasing or decreasing.
• Approximately 60% of a normal animal`s body weight is composed of
water, with variations between and within species.

3. `• Electrolytes are compounds which exists as charged particles in
aqueous solution and conduct a current in electricity.
• The positively charged particles = Cations
• The negatively charged particles = Anions
• ECF contains mainly Na+, Cl-, HCO3- & HPO4`2-
• ICF contains mainly K+, HCO3-, PO4`3-, SO4`2- & citrate.
• These electrolytes dissolve in body fluids fulfil vital roles in virtually all
of life process like nerve conduction, muscle contraction, metabolic
reactions.
• The balance between acidity & alkalinity in animal body is referred as
acid base balance. & it is important homeostatic mechanism
determined mainly by H+ ion concentration in various body fluids
• Kidneys (excretory system) & circulating blood plays an important role
in maintenance

4. `• Obese & older animals tends to have a smaller percentage of water,
whereas neonates can have as much as 80% of their body weight as
water.
• Of 60% water, approximately 40% is with in the cells called ICF- Intra
Cellular Fluids, and remaining 20% is outside the cells referred to as ECF-
Extra Cellular Fluids.
• The ECF may be further divided into intravascular fluids (blood plasma),
extravascular fluids (interstitial fluid, lymph), inaccessible bone
fluid(water trapped in deep layers of bone not readily exchangeable) &
transcellular fluids(secretions of glandular tissues, GIT fluids, respiratory
fluids, aqueous humour, peritoneal fluid, cerebrospinal fluid, etc)
• Although ECF & ICF differ markedly in electrolyte composition, they are
in osmotic equilibrium and water is freely diffusible between them.

5. Renal functions
 main function is excretion of waste products – urea, uric acid &
creatinine
 acid-base balance
 regulation of salt & electrolyte content & volume of extracellular fluid
 production and release of hormones, autacoids, enzymes by kidney
play a vital role in control of systemic blood pressure & RBC production

7. .Glomerular filtration – process by
which water & small solutes are passed from
the lumen of glomerular capillary to the space
of Bowman`s capsule.
 force for glomerular filtration = hydrostatic
pressure (60% of arterial pressure)
 99% of glomerular filtrate is reabsorbed
from tubular portion of Nephron. This mainly
occurs to Reabsorb certain essential
constituents like water, electrolytes &
nutrients present in the glomerular filtrate,
which have to be conserved.
The Renin-Angiotensin-Aldosterone-System
controls GFR & renal blood flow.

9. Tubular mechanism of renal epithelial transport
 simple diffusion
Channel mediated diffusion (Na+, K+,Cl- solutes diffuses passively through ion
channels/pores)
Solvent drag/ convection solute flow (through aqueous pores by bulk flow)
Facilitated transport/ uniport (solute binds to carrier protein & transported
down electrochemical gradient without utilization of energy)
Active transport/ primary active transport (carrier mediated process in which
solute is transported against electrochemical gradient with ATP hydrolysis
providing driving force)
Secondary active transport – symport/ co-transport
(Na+ -glucose, Na+ - Pi, Na+ - AA`s)
-- antiport / counter-transport
(Na+ -H+ counter transport)

11. Tubular transport
Tubular cells perform the active secretory & resorptive functions,
allowing passive diffusion of solute in direction appropriate to its
electrochemical gradient.
 most important tubular mechanisms of electrolyte transport are
= reabsorption of Na+, Cl-
= secretion of H+, K+
 separate mechanism for the transport of Ca++, Mg++, phosphate,
Sulphate & organic acids and bases.

13. Approximate volumes of selected fluid compartments in DOGS
COMPARTMENT % BODY WEIGHT METHOD
Total Body Water TBW 60 Indicator substance
Extra Cellular Fluid ECF 20-27 Indicator substance
Red Blood Cells RBC 3 Counted + calculations
Plasma Volume PV 5 Indicator substance
Total blood volume BV 5.7-10 RBC volume + PV
Interstitial lymph fluid 15 ECF – BV
Transcellular fluid 1-6 Estimated
Bone & dense connective tissue 5 Estimated
ICF 33-40 TBW - ECF

15. Fluid therapy serves to correct –
1.Dehydration.
2.Acidosis and alkalosis.
3.Electrolyte deficiencies.
4.Nutrition and calorie.

16. Approximate values for blood volumes of various animals expressed as
percentages of body weight
SPECIES TOTAL BLOOD VOLUME PLASMA VOLUME RBC VOLUME
Dogs 8.5 4.5 4.0
Cats 6.7 4.7 2.0
Chickens 6.5 4.5 2.0
Cattle 5.7 3.8 1.9
Goats 7.0 5.4 1.6
Horses
Draft
Through bred
Saddle
7.0
10
7.5
4.0
6.0
5.2
3.0
4.0
2.5
Pigs 7.5 4.8 2.7
Sheep 6.5 4.5 2.0

17. WATER, SODIUM, & CHLORIDE.
HOMEOSTASIS: Daily intake of water, nutrients, & minerals is
normally balanced by daily excretion of these substances.
 water-turnover: term used to describe input/output of
body water over a given period of time
Value for water turnover in various domestic animals resting in
cages /stalls range from about 40-132 mL/kg/day.
Maintenance fluid needs: the volume of fluid required daily to
maintain an animal in zero fluid balance, i.e., no net gain / loss of
water.
Normal water intake : occurs in response to thirst, which is
stimulated by plasma hypertonicity &/ contracted ECF

18. Degrees of severity of dehydration and guidelines for
assessment
Body weight
loss (%)
Sunken eyes
Shrunken face
Skin fold test
persists for
(sec.)
PCV (%) Fluid required
to replace
volume deficit
(ml/kg bw)
4-6 Barely
detectable
-- 40-45 20-25
6-8 + + 2-4 50 30-50
8-10 + + + 6-10 55 50-80
10-12 + + + + 20-45 60 80-120

19. Dehydration : classification
• Isotonic - mild dehydration with sodium loss.
Observed in simple enteritis, copious sweating and nephrosis.
• Hypertonic - mild dehydration without sodium loss.
Observed in simple deprivation of water.
• Hypotonic - severe dehydration with sodium loss.
Observed in colibacillosis and salmonellosis.

20. Assessment of dehydration
Mild Moderate Severe
Skin Good elasticity Decreased
elasticity
No elasticity
Eyes Slightly Sunken
Bright
Sunken Slightly
Duller
Sunken Deeply
Dry Cornea
Mouth Moist, Warm Sticky or Dry Dry , Cold
Cyanotic
Body weight
decrease
4-6% 8% 10%

21. ,

22. Parameters to be monitored during fluid
therapy
• For the desired maximal response to occur with therapy the veterinarian must be familiar
with following –
1. Cause and pathogenesis of dehydration.
2. Mechanism of fluid and electrolyte balance.
3. Composition and dosage of electrolyte solutions for treatment.
4. Blood parameters viz PCV & total proteins
5. Hemodynamics - Mean Arterial Pressure, Central Venous Pressure, Mean Pulmonary
Arterial Pressure, Pulmonary Capillary Wedge Pressure
6. Urinary output.
7. Arterial pH & Arterial pCO2
8. Normal bronchovesicular lung sounds on auscultation

23. balanced electrolyte solutions are indicated
for dehydration in large animals
1. Lactated Ringer ….. Commercially available.
2. Acidosis solution ….. NaCl – 21 g
NaHCo3 – 18 g For 4 liters.
KCL – 3 g
3. Ringer’s solution ….. NaCl – 3.4 g
KCl – 1.2 g For 4 liters.
CaCl2 – 1.3 g
4. Alkalosis solution ….. NaCl – 34 g
KCL – 3 g
MgSo4 – 1 g For 4 liters.
Calcium gluconate – 4 g

24. Routes of administration
Oral route : Always prefer isotonic fluid
Intravenous route : 1. Always prefer isotonic solutions
2. Prefer in severe disturbances of fluid and electrolytes.
3. Do not use hypotonic solutions.
Subcutaneous route: 1. only isotonic solutions are used.
2. If periphery is not cold, then fluid will be absorbed
into the system in about 5-6 hours.
3. Contraindicated during oedematous conditions.
Intraperitoneal route : 1. Asepsis is more important
2. Large quantities of fluid can be given.
3. Safest route for administration

25. Clinical observation during fluid therapy
Until urine flow restored rate will be parallel to severity of dehydration, first
rapidly then slowly.
 First hour ; 15 ml – 20 ml / kg body weight / hour.
 Second hour ; 10ml/kg body weight /hour continuously.
 If no urine is voided within 1 hour reduce to rate of fluid approximately half the
quantity.
• Clinical observation is very important during the administration of fluids.

26. Factors considered for fluid therapy
1.Types of illness and severity of conditions
2.Degree of dehydration
3.Conditions of patient
4.Organic functions of patient
5. Type of electrolyte imbalance

27. Drug contraindications
Do not mix sulpha drugs with calcium and
dextrose solutions.
Do not mix oxytetracycline with calcium
solutions.
Try to avoid mixing of too many drugs in
fluids.
Do not mix chloramphenicol with vitamin B
complex to the solutions.

28. Commercially available fluids
1. ELECTROLYTE SOLUTIONS: (ISOLYTE, PREMOLYTE, DEXTROSELYTE) designed
for daily water and electrolyte maintenance and also for the replacement of
loses.
2. DEXTROSE SOLUTIONS: It is used in prophylaxis and treatment of ketosis in
starvation, diarrhea, vomiting or high fever.
3. PLASMA VOLUME EXPANDER: (DEXTRAN in 0.9% SODIUM CHLORIDE) . It is
indicated in shock due to decreased effective blood volume, severe
dehydration and surgical procedures and anesthesia.
:

29. Clinical conditions
I. Hyponatraemia: ( serum conc of Na+ < 140mEq/L in dogs)
II. Hypernatraemia: ( dogs Na+ > 155mEq/L & cats > 160mEq/L )
III. Hypochloremia: ( excessive loss/sequestration of fluids)
IV. Hyperchloremia: (hypernatremic animals due to loss of free H2O)
V. Hypokalemia: ( serum K+ conc < 3.5mEq/L )
VI. Hyperkalemia: ( serum K+ conc > 6 mEq/L )
VII. Hypocalcemia: ( total serum Ca+ < 10-11mg/dL dogs )
VIII.Hypophosphatemia: ( post-parturient Haemoglobinuria )
IX. Hypomagnesaemia: (plasma level of Mg++ < 1.5-2.5 mEq/L )

30. Hyponatraemia
• Etiology:
• acute diarrhea in horses and calves, bladder rupture in new born foals, chronic wasting disease,
intrinsic kidney disease and diuresis, gastrointestinal fistula, severe haemorrhage and excessive
sweating.
• In small animal’s hypoadrenocorticism, post obstructive diuresis, diuretic treatment, congestive heart
failure, severe liver disease and nephritic syndrome.
• Treatment:
• 1) 5% sodium bicarbonate
• 2) Lactated Ringers solution (precursor of bicarbonate).
• 3) Normal saline
• 4) 5% saline (avoided if acidosis is present)
• Calcualtion Na+ requirement for replacement therapy in mEq
•
• = 140 – measured plasma sodium X weight in Kgs
• 3
•

31. Hypernatraemia
Etiology:
In large animals - prolonged exposure to dry heat, respiratory loss with fever, low
intake of water, excessive salt intake with adequate water.
In small animals - pure water loss, diabetes insipidus, hypertonic NaHCO3
administration, cardiac arrest, feline urethral obstruction, acute renal failure.
Types – hypervolaemic, hypovolaemic, isovolaemic
Treatment :
1) Intake of fresh water in sufficient quantities.
2) 5% dextrose or maintenance fluid intravenously.
3) Salt poisoning – loop diurectics.

32. hypochloremia
• occurs as a result of an increase in the net loss of electrolyte in the intestinal tract in
acute intestinal obstruction, dilatation and impaction and torsion of the abomasum &
enteritis.
• Clinical findings include anorexia, weight loss, lethargy, mild polydipsia and polyurea. A
marked metabolic alkalosis occurs with hypokalemia, hyponatremia, azotemia &
death.
• Meq of “chloride” required = body weight(kgs) X Plasma chloride deficit
• 3
•
• Litres of 0.9 % saline required = Meq of chloride required
• 154

33. hypokalaemia
• occurs as a result of decreased dietary intake, increased renal
excretion, abomasal stasis, intestinal obstruction and enteritis, the
prolonged use of potassium-free solutions in fluid therapy for
diarrhoeic animals may result in excessive renal excretion of
potassium.
• Treatment :
1.Potassium chloride intravenously or orally potassium bicarbonate
2.potassium citrate orally
• Meq of Kcl = Extra celluar deficit X Total body weight

34. hyperkalemia
• occurs most commonly following severe metabolic acidosis.
• In small animals rapid infusion of potassium salts, high dose of potassium,
penicillin G, oliguric acute renal failure, Terminal stages of chronic renal
failure, urethral obstruction, lower urinary tract rupture, metabolic acidosis
and hypoadrenocorticism.
• Hyperkalemia has a profound effect on cardiac function. There is usually
marked bradycardia and arrhythmia and sudden cardiac arrest.
• Treatment : 1) Administration of NaHCO3 intravenously to correct acidosis and
shift K+ to the intracellular component.
• 2) Administration of dextrose 0.5 gms per kg bw.t and Insulin 0.1 unit per kg
B.wt to take up potassium for glycogen synthesis.
• 3. Administration of calcium gluconate to temporarily allevate the effects of
hyperkalemia on heart

35. hypocalcaemia
• occurs immediately after parturition, hypoprotenemia,
hypoparathyroid condition and in acute or chronic renal failure,
puerperal tetany, ethylene glycol intoxication & inappropriate
administration of a hypertonic phosphate enema.
• Treatment:
1. Cattle 40% calcium borogluconate intravenously
2. calcium chloride / calcium gluconate iv
3. Maintainence dose = 10ml of 10% Ca gluconate added to 500ml of
isotonic normal saline 0.9% Nacl solution.

36. Hypophosphatemia
• occurs in cattle under conditions similar to those of hypocalcaemia, a
decrease in feed intake or alimentary tract stasis will result in a
decrease in serum inorganic phosphate.
• Treatment:
1.sodium acid phosphate intravenously
2.parentral injection of phosphorous preparation
3.Dietary suppliments of phosphorus along with calcium in the ratio
1.5-2 parts Calcium : 1 part phosphrous.

37. Hypomagnesaemia
• occurs due to inadequate energy intake while grazing lush pasture
low in magnesium, starvation, anorexia, low dietary content of
magnesium, diarrhea and hypothyroidism.
• Treatment :
1.magnesium sulphate 10% intravenously. Usually concurrent
administration of calcium is advisable.
2.Magnesium salts may be administered as a 20% solution in 5%
dextrose.

38. Acid-base imbalance
• Is abnormality in which the normal equilibrium between the acids & bases in
body is disturbed and plasma pH is deviated out of the normal range (7.35-
7.45)
• pH of arterial blood < 7.4 = acidosis
• pH of arterial blood > 7.4= alkalosis
• These changes are mainly the result of either respiratory or metabolic
abnormalities, which disturb the normal ratio 20:1 HCO3- : H2CO3 ratio
Respiratory acidosis/alkalosis=pH imbalance due to CO2 levels
Metabolic acidosis/alkalosis=pH imbalance due to HCO3- level
• In these abnormal conditions the body attempts to compensate for a pH
imbalance by adjusting the activities of lungs/kidneys.

39. Horses
• In case of severe diarrhea, shock & intestinal obstruction =
predisposes to severe metabolic acidosis.
• respiratory acidosis is very common sequel to closed circuit
inhalation anesthesia in the horses.
• Severe hypokalemia with blood K+ values < 2.5-3mEq/l.
• Acidosis in foals = even dangerous than adults with blood K+ values
>7mEq/L
• Treatment: Prompt correction of the acidosis

41. Cattle
• Abomasal disease coupled with an obvious fluid balance disorder,
hypochloremia, hypokalemia, alkalosis.
• Confirmed by appropriate lab tests for proper treatment.
• Grain overloading = severe dehydration & metabolic acidosis.
• Calf diarrhea = severe dehydration, metabolic acidosis with dangerous
hyperkalemia
• Treatment should focus on specific conditions & electrolyte balance.

43. Thank - you