Serum tobramycin levels during selective decontamination of the digestive tract in ICU patients on renal replacement therapy

Introduction

Selective decontamination of the digestive tract (SDD) is an infection prophylaxis regimen that may improve survival in ICU patients [1]. Antibiotics for SDD are nonabsorbable, are given enterally and are therefore considered safe to use. The aim of our study was to determine whether enteral administration of tobramycin as part of a SDD regimen may lead to detectable and potentially toxic serum tobramycin concentrations in patients with renal failure.

Methods

A prospective, observational study in ICU patients given SDD treatment for at least 3 days. All patients were on continuous venovenous hemofiltration with a filtration rate of 35 ml/kg/hour. Tobramycin serum concentrations were measured every 3 days.

Results

Serum samples were taken a median 6 days after the start of SDD (IQR 3–9 days). Detectable tobramycin levels were found in 12 of 19 patients (63%) and in 15 of 26 serum samples (58%). In four patients tobramycin concentrations were ≥ 1 mg/l, and in one of these patients a toxic concentration of 3 mg/l was found. All patients with tobramycin levels >1 mg/l had ischemic bowel disease. In contrast, no patients with lower concentrations had intestinal ischemia.

Conclusion

In patients with renal failure treated with continuous venovenous hemofiltration, administration of SDD can lead to detectable and potentially toxic tobramycin serum concentrations. The risk of increased enteral absorption of tobramycin may be particularly high in patients with intestinal ischemia. We advise monitoring plasma tobramycin concentrations in patients with renal failure on prolonged treatment with SDD.