Cumulative fluid intake minus output is not associated with ventilator weaning duration or extubation outcomes in children*

Abstract

The effect of fluid balance on respiratory outcomes for critically ill children has not been evaluated. The only indicator of fluid balance routinely recorded across our intensive care units was estimated fluid intake and output. We sought to determine whether cumulative intake minus output (I-O) at the start of weaning predicted weaning duration and whether cumulative I-O at extubation predicted extubation failure. Prospective observational study. Ten pediatric intensive care units. Cumulative I-O was recorded daily for 301 mechanically ventilated children (<18 yrs of age) from November 1999 through April 2001. Cumulative I-O was recorded during a study of weaning strategies and extubation failure in which mechanical ventilation of the majority of patients during weaning and extubation was managed according to a protocol that did not include fluid balance indicators. Outcomes were the time to successful removal of ventilatory support and the rate of initial extubation failure. Relationships between cumulative I-O and outcomes were assessed by means of proportional hazards and logistic regression. The mean cumulative I-O per kilogram of ideal body weight at the start of weaning was 101 mL (sd, 180). Cumulative I-O at the time weaning was initiated did not predict duration of mechanical ventilator weaning. The mean cumulative I-O per kilogram of ideal body weight at extubation was 136 mL (sd, 237). Cumulative I-O at extubation did not predict extubation outcome. There was an association between cumulative I-O at extubation and the duration of weaning in cases not managed by a protocol. Although routinely recorded, cumulative fluid I-O does not appear to have clinical utility in cases managed according to a mechanical ventilator protocol in which tidal volume and oxygenation on minimal levels of ventilator support are systematically tested.