Renal Physiology

Question 1

What are the conventional treatment principals of acute renal failure (ARF) therapy?

Answer 1

• Reversal of inciting or underlying cause.
• Judicious administration of IV fluids.
• Correction of electrolyte and acid-base abnormalities.

Ref: JVIM 2013; 27: 308-316.

Question 2

When should renal replacement therapy (RRT) be instituted in cases of ARF?

Answer 2

• If ARF remains refractory to conventional treatment.
• Renal indications: reduced GFR –> solute imbalance; oliguria –> ECF overload.
• Non-renal indications: facilitating clearance of drugs, toxins, toxic metabolites or inflammatory cytokines.

Ref: JVIM 2013; 27: 308-316.

Question 3

Describe the way in which continuous renal replacement therapy (CRRT) purifies the blood.

Answer 3

Blood is passed through thousands of semipermeable membranes and blood is purified via diffusion, convection (solvent drag) and adsorption (adhesion).

Ref: JVIM 2013; 27: 308-316.

Question 4

List the advantages of CRRT over haemodialysis.

Answer 4

• Slow, continual process allows for better control of blood pressure, electrolyte and acid-base balance.
• Convective process allows for more effective removal of larger molecules with limited diffusibility.
• Ability to use pre-packaged sterile fluids vs pure dialysate.

Ref: JVIM 2013; 27: 308-316.

Question 5

Describe the reported procedure for CRRT in the horse.

Answer 5

1. Sedation: initial bolus followed by CRI of detomidine.
2. Anti-coagulation: initial bolus followed by CRI of heparin.
3. Fluids: double lumen dialysis catheter in jugular vein; CRRT extracorporeal circuit with 1.5m2 filter was connected to the horse for 6h removing 250ml/min blood and dialysate rate set at 3000ml/h; dialysate and replacement fluid = Plasmalyte.
4. Free choice access to feed and water throughout.

Ref: JVIM 2013; 27: 308-316.

Question 6

Outline the reported side effects of CRRT in horses.

Answer 6

• Hypothermia: progressive decrease in rectal temperature over 6h; due to cool IV fluids and/or detomidine CRI.
• Mild dec in HR/RR.
• Occasional transient arrhythmias: proposed due to detomidine CRI not CRRT.
• Thrombocytopaenia: due to heparin admin.
• Haematoma formation at catheter sites: due to heparin admin.
• Hyperphosphataemia: mechanism unknown.

Ref: JVIM 2013; 27: 308-316.

Question 7

Compare the creatinine clearance rate achieved in CRRT with that achieved by peritoneal dialysis and that of the healthy horse.

Answer 7

• CRRT: 0.127mg/kg/min.
• Peritoneal dialysis: 0.0322 mL/kg/min (intermittent) to 0.1054 mL/kg/min (continuous).
• Normal horse: 1.7-2.7ml/kg/min.

Ref: JVIM 2013; 27: 308-316.