Vancomycin and tobramycin clearance in an infant during continuous hemofiltration

Area of Science:

• Pharmacokinetics and pharmacodynamics in pediatric critical care.
• Renal replacement therapy and drug disposition.
• Antibiotic management in critically ill infants.

Background:

• Continuous veno-venous hemofiltration (CVVH) is used in critically ill infants for fluid management and toxin removal.
• The impact of CVVH on the clearance of renally cleared antibiotics like vancomycin and tobramycin requires careful evaluation.
• Accurate calculation of drug clearance during CVVH is crucial for optimizing therapeutic efficacy and preventing toxicity.

Observation:

• A case report detailing vancomycin and tobramycin clearance in a four-month-old infant undergoing CVVH.
• Two methods (Method A and Method B) were employed to calculate hemofiltration clearance (ClHF).
• Method A involved 24-hour ultrafiltrate collection and serum sampling, while Method B used pre- and postfilter samples with the Fick principle.

Findings:

• CVVH significantly increased the clearance of both vancomycin and tobramycin in the infant.
• Method A yielded ClHF values for vancomycin (0.27–0.80 mL/min) and tobramycin (0.32–0.91 mL/min).
• Method B showed higher and more variable ClHF for vancomycin (0–2.08 mL/min) and tobramycin (0–1.6 mL/min), suggesting potential overestimation.

Implications:

• Dosage modifications for vancomycin and tobramycin are essential during CVVH in infants.
• Method A is considered more reliable for ClHF calculation due to its ability to average fluctuations in ultrafiltrate flow rates.
• Regular monitoring of serum drug concentrations is recommended to guide vancomycin and tobramycin dosing in infants receiving CVVH.