From the Research
Dose adjustment during continuous renal replacement therapy (CRRT) is essential for medications that are primarily eliminated by the kidneys, and the most recent evidence suggests that the delivered CRRT effluent dose for critically ill patients with AKI should be 20-25 ml/kg/h on average 1. For most drugs, start with the normal dose and then adjust based on the specific CRRT modality (CVVH, CVVHD, CVVHDF) and flow rates. The key factors to consider when adjusting doses include:
- The drug's molecular weight
- Protein binding
- Volume of distribution
- The CRRT settings, including effluent rate Antibiotics often require higher doses during CRRT compared to standard hemodialysis due to continuous clearance. For example, vancomycin typically needs 15-20 mg/kg loading dose followed by 10-15 mg/kg every 24 hours with therapeutic drug monitoring to maintain trough levels of 15-20 mg/L. Meropenem should be dosed at 1 gram every 8-12 hours rather than the extended interval used in anuric patients. Medications with narrow therapeutic windows like phenytoin, digoxin, and aminoglycosides require close monitoring with serum level measurements. Sedatives and analgesics (propofol, fentanyl, midazolam) often need dose reductions of 20-30% from normal doses. Higher effluent rates (>25 mL/kg/hr) increase drug clearance and may require higher or more frequent dosing, as supported by the study published in 2021 1. Regular reassessment of medication dosing is necessary as the patient's clinical condition changes, especially when transitioning between different renal replacement modalities or when CRRT is discontinued, and the time to dose adjustment is crucial, with a median time of 13 hours reported in a recent study 2.
Some key considerations for dose adjustment during CRRT include:
- The type of CRRT modality used
- The flow rates and effluent rates
- The patient's residual renal function
- The presence of other organ dysfunction
- The potential for drug interactions The study published in 2006 3 highlights the importance of considering the pharmacokinetic principles during CRRT, including the impact of protein binding, volume of distribution, and total body clearance on drug removal. Additionally, the study published in 2024 2 emphasizes the need for timely dose adjustment during CRRT, with a focus on antimicrobial therapy. Overall, dose adjustment during CRRT requires careful consideration of multiple factors and regular monitoring to ensure optimal patient outcomes.