Comparison between continuous versus bolus furosemide administration in oliguric postoperative paediatric cardiac patients

Objective

To compare the efficacy of continuous versus bolus furosemide administration on urinary output, sodium and furosemide excretion following paediatric cardiac surgery.

Design

Prospective, double-blinded, randomised crossover study.

Patients

Fifteen infants with postoperative oliguria (urine volume < 1 ml/kg per hour) unresponsive to 10 ml/kg 0.9% saline bolus were enrolled in the study. Time of enrolment was between 16 and 24 hours post-PICU admission, which is the period of least ADH-mediated antidiuresis. Diagnostic groups included Tetralogy of Fallots (n = 7), Norwood Stage 1 (n = 2), VSD and arch repair (n = 2), and other (n = 4).

Interventions

Patients were randomly assigned to receive an equivalent dose of furosemide either as a single bolus dose (1 mg/kg) with a placebo saline infusion or a continuous furosemide infusion (0.2 mg/kg bolus followed by 0.125 mg/kg per hour) and studied over a 6 hour period. After a 2 hour 'washout' period, the patients were crossed over and the study repeated with the alternative administration method. Urine was collected every 2 hours for electrolytes and urinary furosemide concentration (measured by high-performance liquid chromatography) [1].

Measurements and results

The median age (IQ) was 4.1 months (0.1–7.6), weight 6.3 kg (3.5–7.1) and duration of cardiopulmonary bypass (n = 13) was 99 min (74–112).

Cumulative urine output (Fig. 1) and Na excretion were similar between both groups (ANOVA, P = 0.3) over the 6 hour study period. However, cumulative tubular furosemide excretion (Fig. 2) was significantly greater following furosemide bolus (ANOVA group effect, P < 0.02). Additionally, cumulative K excretion was similar between both treatment methods (ANOVA, P = 0.3). No differences were observed between treatment groups for the following haemodynamic parameters; heart rate (ANOVA, P = 0.9), mean BP (ANOVA, P = 0.9) or CVP (ANOVA, P = 0.8).

Figure 1

Cumulative urine output over time. Bolus therapy (closed circles), and continuous infusion (open circles). Mean/SEM.

Figure 2

Cumulative furosemide excretion over time. Bolus therapy (closed circles), and continuous infusion (open circles). Mean/SEM.

Conclusion

Furosemide administration by continuous infusion is effective as bolus therapy in its diuretic and natriuretic effects in oliguric infants following cardiac surgery. The continuous furosemide infusion produces a greater diuresis per urinary tubular furosemide concentration.