Fluid Therapy

Question 1

What percentage of BW does water constitute?

Answer 1

60%

Question 2

What is the normal osmolality range of body water?

Answer 2

290-310Osm/L

Question 3

What percentage of body water is within the extracellular component and intracellular component?

Answer 3

• 1/3 extracellular (25% intravascular, 75%interstitial)
• 2/3 intracellular

Question 4

What is the major cation and anion in intracellular fluid?

Answer 4

• Major cation K+ (Mg++, Na+)
• Major anion PO4– and proteins

Question 5

What is the major cation and anion of extracellular fluid?

Answer 5

• Cation - Na+
• Anions Cl- and HCO3-

Question 6

What determines oncotic pressure and hydrostatic pressure?

Answer 6

• Oncotic - Albumin, globulins, fibrinogen
• Hydrostatic - intravascular blood pressure and vascular resistance

Question 7

What are maximum rates of recommended Na increased and decrease in the blood

Answer 7

• Increase by no more than 0.5mEq/h
• Decrease by no more than 1mEq/h

Question 8

What is hypotensive resuscitation?

Answer 8

In situations of uncontrolled bleeding, judicious resuscitation may be beneficial (aim for MAP 60mmHg or SAP 90mmHg) so as to not disrupt clots and cause worsening of haemorrhage

Question 9

Name 4 choices for isotonic crystalloid fluids? Which of these does not contain a buffer and is therefore acidifying?

Answer 9

• 0.9%NaCl (acidifying)
• LRS
• Plasmalyte 148
• Normosol-R

Question 10

What percentage of IV isotonic crystalloids remain in the IV space? How long does it take for equilibrium?

Answer 10

Only 25% remains in the IV space, takes 20-30min to reach equilibrium

Question 11

What is the most appropriate isotonic crystalloid for the following conditions?
- Surgical patients with head trauma
- Periop patients with severe hypoNa or hyperNa
- Surgical patients with hypoCl metabolic alkalosis
- Surgical patints with severe metabolic acidosis, not due to lactate

Answer 11

• Head trauma –> 0.9%NaCl. Has the highest Na conc and therefore is least likely to cause a drop in osmolality and cerebral oedema
• Hypo/hyperNa –> Choose the fluid which most closely matches their Na. Too rapid a drop can cause cerebral oedema. To rapid an increase can cause central pontine myelinolysis
• HypoCl met alkalosis –> 0.9%NaCl as it is the highest in Cl and will help normalise the pH
• Metabolic acidosis –> Crystallois with a buffer (lactate, acetate, gluconate). NOT NaCl

Question 12

List options for hypotonic fluids

Answer 12

• 0.45% NaCl
• 0.45%NaCl with 2.5% dextrose
• Plastalyte 56
• Plasmalyte M with 5% dextrose
• Normosol M with 5% dextrose
• 5% Dextrose in water (D5W)

Dextrose is rapidly metabolised to H2O and CO2 (good source of free water)

Question 13

What additional beneficial effects can hypertonic saline cause? Risk of fast administration?

Answer 13

• Reduces endothelial swelling, increase cardiac contractility, mild peripheral vasodilation, modulate inflammation, decrease intracranial pressure
• Admin over 1ml/kg/min can cause stim of pulm C fibres and subsequest hypotension, bradycardia and bronchoconstriction

Question 14

What are potential side effects of colloids?

Answer 14

• Disruption of normal coagulation (depletion of VIII and vWB), impaired platelet function, interference of stability of fibrin clots
• Anaphylaxis
• Volume Overload
• Renal impariment

Question 15

What is the recommended dose of colloids for hypovolaemia and for acute hypoproteinaemia?

Answer 15

• Hypovolaemia –> 5-20ml/kg in dog, 2.5-10ml/kg cat
• Hypoprot –> 0.5-2ml/kg/day CRI

Question 16

How much blood loss requires a transfusion?

Answer 16

Can usually tolerate 10-15% blood loss but 20% often requires transfusion