What is the CVVHDF (Continuous Veno-Venous Hemodiafiltration) prescription for an 85kg acute liver patient with severe coagulopathy, including prepump, post-pump, dialysate, and blood flow rates?

CVVHDF Prescription for 85kg Acute Liver Patient with Severe Coagulopathy

For an 85kg acute liver patient with severe coagulopathy requiring CVVHDF, use blood flow 100-150 mL/min, dialysate flow 1-2 L/hour (approximately 20-25 mL/kg/hour), replacement fluid 1-2 L/hour with pre-dilution mode, and avoid anticoagulation or use regional citrate if absolutely necessary. 1, 2

Blood Flow Rate

• Set blood flow at 100-150 mL/min to minimize hemolysis and maintain circuit patency while accounting for severe coagulopathy 3
• Blood flow rates of 100 mL/min or more can be maintained regardless of systemic blood pressure in critically ill patients 3
• Lower blood flow rates (closer to 100 mL/min) are preferable in acute liver failure patients to reduce shear stress and potential bleeding complications 4, 5

Dialysate Flow

• Prescribe dialysate flow at 1-2 L/hour (approximately 12-24 mL/kg/hour for this 85kg patient) 1, 2
• For enhanced ammonia clearance in acute liver failure, CVVHD mode with dialysate flow is superior to pure convection 2
• Maintain Qd/Qb ratio >1.5 for optimal solute clearance 1
• Use bicarbonate-based dialysate rather than lactate-based solutions given the liver failure and risk of lactate accumulation 1
• Warmed dialysate should be used to maintain hemodynamic stability 1, 2

Replacement Fluid (Post-Dilution and Pre-Dilution)

• Use pre-dilution mode exclusively with replacement fluid at 1-2 L/hour to minimize filter clotting risk in the coagulopathic patient 1
• Pre-dilution administration improves ultrafiltration rates and reduces circuit clotting, which is critical given the inability to use standard anticoagulation 1
• Total effluent volume (dialysate + ultrafiltrate) should target 20-25 mL/kg/hour (1.7-2.1 L/hour for 85kg) for adequate solute clearance 1, 2

Ultrafiltration Rate

• Set net ultrafiltration at 100-200 mL/hour for fluid removal, adjustable based on hemodynamic status and volume overload 3
• Avoid aggressive fluid removal given the hemodynamic instability common in acute liver failure 6
• The closed dialysate circuit allows accurate ultrafiltration control adaptable to patient needs 3

Anticoagulation Strategy

• Avoid systemic anticoagulation entirely given severe coagulopathy in acute liver failure 6, 4
• The coagulopathy of acute liver failure does not protect against circuit clotting, but systemic anticoagulation carries prohibitive bleeding risk 4, 5
• If circuit clotting becomes problematic despite pre-dilution mode, consider regional citrate anticoagulation only after careful risk-benefit assessment 2
• Do not use heparin, LMWH, or other systemic anticoagulants as bleeding risk far outweighs benefits 6
• Frequent saline flushes (every 30-60 minutes) may help maintain circuit patency without anticoagulation 3

Fluid Composition Considerations

• Use physiologic electrolyte concentrations in dialysate and replacement fluid 1
• Avoid supraphysiologic glucose concentrations which cause hyperglycemia 1
• Bicarbonate buffer is mandatory over lactate given hepatic dysfunction and inability to metabolize lactate 1
• Monitor and replace calcium carefully if using citrate anticoagulation 2

Monitoring Parameters

• Monitor transmembrane pressure, filter function, and circuit patency hourly 1
• Check coagulation parameters (PT/INR, fibrinogen) every 6-12 hours but do not routinely correct unless active bleeding occurs 6, 4
• The INR is unreliable for assessing bleeding risk in liver disease and should not guide prophylactic correction 6
• Monitor ammonia levels given the hyperammonemia common in acute liver failure 2

Critical Pitfalls to Avoid

• Do not prophylactically transfuse FFP, platelets, or other blood products to "correct" laboratory values in the absence of bleeding 6
• FFP infusion increases portal pressure and volume overload without proven benefit for bleeding prevention 6
• Avoid subclavian vein access due to thrombosis and stenosis risk; use femoral or internal jugular access 1, 2
• Do not use prothrombin complex concentrates (PCCs) routinely as they carry thrombotic risk in cirrhotic patients 6
• Recognize that patients with acute liver failure have a rebalanced but fragile hemostatic system that can tip toward either bleeding or thrombosis 6, 4, 5