Critical Care and Fluid Therapy (Ch 44) Flashcards
What is the Total Body Water, Extracellular Fluid Volume, Plasma Volume, and Intracellular Fluid Volume of adult horses (in L/kg)?
TBW: 0.6 L/kg (0.623 to 0.677)
ECFV: 0.25 L/kg (0.214 to 0.253)
Plasma Volume: 0.05 L/kg
ICFV: 0.4 L/kg (0.356 to 0.458)
What is the Total Body Water, Extracellular Fluid Volume, Plasma Volume, and Intracellular Fluid Volume of neonatal horses (in L/kg)?
TBW: 0.74 L/kg
ECFV: 0.4 L/kg (0.38 to 0.4)
Plasma Volume: 0.09 L/kg
ICFV: 0.4 L/kg (0.38)
What determines the flow between plasma and interstitial volume?
Starling Forces!
Net Capillary Filtration = Kf ( [Pcap - Pif] - σ [πp - πif] )
Kf = Capillary filtration coefficient
πp = colloid osmotic pressure within the capillary
πif = COP within the interstitium
Pcap = hydrostatic pressure within the capillary
Pif = hydrostatic pressure within the interstitium
σ = capillary reflection coefficient for proteins
What are the 3 main determinants of net movement of fluid between the ECFV and ICFV?
1) Tonicity (effective osmolality) of the ECFV
-Primarily determined by Sodium & Chloride
-Regulated by Vasopressin (ADH)
EO = (2 x Na) + (Glucose/18)
2) Tonicity of the ICFV
- Primarily determined by Potassium
3) Cellular Membrane Permeability
- damage during disease states can result in significant fluid shifts
What is central venous pressure and how is it useful in fluid therapy?
CVP = pressure within the (cranial) vena cava
Measured with a 20 to 30 cm central venous catheter in foals
High central venous pressure (>12cm H2O in foals and > 15 in adults) indicates fluid overload
How should horses in liver failure be managed in regards to fluid therapy?
- No lactate - metabolized by liver
- Use Norm-R, Plasma-lyte which uses acetate –>bicarb
- Provide dextrose to decr gluconeogenesis demands
- Provide B & C vitamins
- Avoid hypokalemia (leads to metabolic alkalosis and worse hepatic encephalopathy)
- Higher than maint. rates to dilute ammonium, bilirubin, and other toxins metabolized by the liver
- Watch for hypoproteinemia (use colloids when necessary), hyponatremia, coagulopathies, and high lactate
What are fluid therapy considerations for horses with diarrhea or colitis?
- A combo of cyrstalloids and colloids may have many benefits
- Collids are indicated when concurrent hypoproteinemia and hypovolemia are present
- Potassium, calcium, and magnesium should be supplemented as necessary
- Hypertonic saline has several potential benefits including volume expansion, immunomodulatory effects, anti-edema effects, and positive inotropic effects
What are fluid therapy considerations for horses with sepsis?
- Cyrstalloids are the mainstay therapy
- Combo of cyrstalloids and colloids may have advantages when hypoproteinemia is present
- Fluid challenge of 10-20ml/kg boluses
- Monitor fluid therapy safety points
- Metabolic acidosis is common
What are fluid therapy considerations for horses with Acute Renal Failure?
- Polyuric horses - tx w/crystalloids for diuresis (2x maint)
- Freq assessment of fluid status and adjust rate
- 0.9% saline is midly acidifying d/t hyperchloremia and should be avoided in ARF d/t reduced renal blood flow
- Anuric or oliguric - tx promptly. If fluid loading doesn’t work, can use furosemide, mannitol, or dopamine. Then can try hemodialysis or peritoneal dialysis
- Avoid synthetic colloids! (can cause renal injury)
What are fluid therapy considerations for horses with acute hemorrhage?
If hemorrhage is controlled
- hypertonic saline (anti-inflammatory –> follow up with cyrstalloids
- LRS may be proinflammatory and should be avoided
- replace 3-4x estimated blood lost in isotonic fluids
Uncontrolled hemorrhage
- hypotensive resuscitation (60 mmHg MAP)
- small volumes of fluids to maintain organ perfusion
What are fluid therapy considerations for horses with Acute Neurologic Injury?
- Clinical outcome improved with prompt tx of CNS hypoperfusion
- Isotonic crystalloids - most appropriate
- Follow with hyperosmolar therapy with mannitol or hypertonic saline if evidence of cerebral edema is present
- Monitor perfusion, osmolarity, and [e+]
What are fluid therapy considerations for horses with Rhabdomyolysis?
- Acute myopathies often have hypochloremia and concurrent hyponatremia, hyperkalemia, hyperphosphatemia
- LRS is preferred
- Horses with acute myopathies should be given fluids greater than maint. rate for dilution and diuresis of myoglobin
What are fluid therapy considerations for horses with acute HYPP episode?
- 4 to 20 ml of 0.9% saline per kg (depending on severity/duration)
- 2% to 5% dextrose
- 0.2 to 0.5 mEq/kg of calcium (0.2 to 0.5 ml/kg of 23% CaGluconate total diluted in fluids) to protect against arrhythmias (no more than 50 ml/L)
- 0.5 to 1 mEq/kg of bicarb in normal saline with dextrose
- If refractory - insulin CRI of 0.005 to 0.1 units/kg/hr)
What are fluid therapy considerations for horses with burns?
- Hypertonic saline for resuscitation followed by isotonic crytalloids
- Isotonic crystalloids needed for high sodium loss thorugh wounds
- Plasma may be needed due to protein loss
- Excessive volumes of fluids should be avoided to avoid edema
What are fluid therapy considerations for horses with Acute Respiratory Distress Syndrome?
- Ideal fluid for ARDs is unknown
- Crystalloids > colloids (leak into lungs)
- Hypovolemia and dehydration should be corrected but not to excess - be conservative
- Fluid balance/pressures should be assessed frequently
