Fluid Therapy (Key points only)

Question 1

Why fluid therapy?

Answer 1

1. Increase cardiac output
2. Increases and maintain pre-load
3. Maintain or increase oxygen delivery to tissues
4. Correct acid-base imbalances

Question 2

3 phases of fluid resuscitation

Answer 2

1. Correct hypovolemia (resuscitation)
2. Treat dehydration (rehydration phase)
3. Ongoing losses

Question 3

Major components of ECF?

Answer 3

• Na, Cl

Question 4

Major component of ICF?

Answer 4

• Potassium!

Question 5

Why do horses need calcium?

Answer 5

• Normal neuromuscular function

- Cardiac rhythm and contractility

Question 6

Where do horses get their calcium?

Answer 6

• In their feed

Question 7

Anion gap formula

Answer 7

[Na+ + K+] - [Cl- + HCO3-]

Question 8

What does a high anion gap mean?

Answer 8

• Metabolic acidosis

Question 9

What does a deficit of the extravascular fluid compartment mean clinically?

Answer 9

• Interstitial, intracellular

- Dehydration!

Question 10

Clinical signs of dehydration?

Answer 10

• Sunken eyes
• Dull cornea
• Dry mucous membranes

Question 11

Meaning of a high PCV and relatively low TP?

Answer 11

• Means that there is a lot of loss

Question 12

Clinical signs of hypovolemia

Answer 12

• Tachycardia
• Cold extremities
• Tachypnea
• Decreased pulse pressures
• Reduced jugular fill

Question 13

Maintenance fluid requirements

Answer 13

• 60mL/kg/day in adult horses
• Neonates - 100-120 mL/kg/day up to about 3 weeks

Foal - 90 mL/kg/day

Question 14

Estimate of dehydration

Answer 14

% dehydration * body weight in kg

e.g. 10% dehydrated 500 kg horse = 0.1 *500 = 50L deficit

Question 15

Monitoring for fluid resuscitation

Answer 15

• Monitor HR, PCV/TP, CR to see if keeping up with loss

Question 16

How would you plan fluids for a 500kg horse that is 10% dehydrated?

Answer 16

• 0.1 *500kg = 50mL deficit
• Give 50% in the first 1-2 hours and remainder over the next 24 hours (i.e. 20-25 liters over 2 hours)
• Calculate maintenance (60 mL/kg/day * 500kg = 30 L)
• Make an estimate of ongoing losses
• Total fluids needed over next 24 hours = (remainder of resuscitation volume) + maintenance + ongoing losses

Question 17

Clinical parameters to determine if you are keeping up with fluids?

Answer 17

• Heart rate
• Mentation
• Extremity temperature
• Mucous membrane color
• CRT
• Pulse quality
• Urine output
• CBC (PCV, plasma protein)
• Serum biochemistry (BUN/creatinine; TP, albumin, electrolytes)
• Lactate
• Venous or arterial blood gas

Question 18

Transport of dehydrated horse

Answer 18

• If hospital is 2 hour drive or longer

- Consider bolus of hypertonic saline (7.2%)

Question 19

Contraindications for hypertonic saline

Answer 19

• Exhaustion
• Uncontrolled hemorrhage
• Salt intoxication
• Heat stroke,
• Hyperosmotic states
• Exhaustion and electrolyte loss in sweat
• Acute kidney injury

Question 20

Crystalloids examples

Answer 20

• Normal saline
• LRS
• 5% Dextrose in water
• Plasmalyte
• Most are high sodium, low potassium
• Often need to supplement potassium in horses off feed

Question 21

What electrolytes are commonly decreased with diarrhea?

Answer 21

• sodium, potassium, chloride, and bicarbonate

Question 22

Potassium supplementation

Answer 22

• If animals are off feed for a prolonged period

- Don’t exceed 0.5mEq/kg/hr (20mEq/L of KCl)

Question 23

Ways to reduce hyperkalemia?

Answer 23

• Volume replace with K+ free fluids
• DO NOT try to add NaHCO3
• Calcium gluconate can stabilize
• Dextrose
• Oral karo syrup

Question 24

Electrolytes to supplement in critical horses that are off feed?

Answer 24

• Mg, K, Ca2+

Question 25

Causes of metabolic acidosis

Answer 25

• Lactic acidosis
• GI loss of bicarbonate (secretional metabolic acidosis)
• Renal loss of bicarbonate (secretional metabolic acidosis)

Question 26

When to add bicarbonate?

Answer 26

• Only when bicarbonate level is below 15mEq/L and rehydration hasn’t worked or pH <7.2
• Base deficit x kg x 0.3

Question 27

What is the most effective way to rehydrate luminal material?

Answer 27

• IMPACTIONS!

- If IV, won’t go to the site of impaction

Question 28

oral replacement therapy

Answer 28

• Pass an NG tube
• Secure in place
• 4 L every 1-2 hours