QTc-interval prolongation associated with slow intravenous erythromycin lactobionate infusions in critically ill patients: a prospective evaluation and review of the literature.

Intravenous erythromycin has recently been associated with significant QTc interval prolongation, torsades de pointes, and sudden cardiac death. The prolonged the QTc interval attributed to erythromycin typically is associated with rapid infusion rates in excess of 10 mg/minute. We prospectively assessed the relationship between QTc interval prolongation and erythromycin administration by slow intravenous infusion (mean rate 8.9 +/- 3.5 mg/minute, range 3.9-16.7 mg/minute). Electrocardiographic (ECG) rhythm strips were prospectively obtained in 44 critically ill patients receiving intravenous antibiotics (22 received erythromycin and 22 ceftazidime, cefuroxime, cefotaxime, ceftriaxone, or ampicillin-sulbactam as controls). The ECG recordings were obtained immediately before and within 15 minutes after drug infusions. Only the first available set of ECG strips were evaluated. Two controls had evidence of hepatic dysfunction; no patients receiving erythromycin did. The QTc interval was calculated using Bazett's formula by two blinded investigators. For controls, mean +/- 1 SD (range) QTc intervals were 423 +/- 96 (300-550) msec at baseline and 419 +/- 96 (280-610) msec after infusion (p = 0.712). In contrast, in the erythromycin group, the interval was significantly prolonged from 524 +/- 105 (360-810) msec at baseline to 555 +/- 134 (400-980) msec after infusion (p = 0.034). No patients experienced a dysrhythmia as a consequence of erythromycin infusion. Despite slow rates of infusion, QTc interval prolongation was significant. The clinical importance of this finding remains to be determined.

A retrospective study of sodium nitroprusside use and assessment of the potential risk of cyanide poisoning.

Sodium nitroprusside (SNP) is an effective vasodilator but is potentially dangerous due to its cyanide content. Infusion rates above 2 micrograms/kg/minute may cause cyanide to accumulate to toxic concentrations in critically ill patients. Coadministration of thiosulfate with SNP effectively and safely prevents cyanide toxicity. This study determined if patients at our institution were treated with SNP infusion rates that could cause cyanide toxicity and whether those patients were administered thiosulfate. We reviewed the charts of 36 critically ill patients treated with SNP during the previous 12 months. In 72% of patients the SNP infusion rates were above 2 micrograms/kg/minute. In 47% the rates were greater than 2 micrograms/kg/minute for 6 hours or more, and in 20% they were greater than 5 micrograms/kg/minute for up to 11 hours. None of the patients was administered thiosulfate. In a significant number of patients the infusion rates of SNP potentially exposed them to significant risk of cyanide toxicity including death.