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The effect of intraoperative Lasix on sodium excretion following cardiac surgery


To determine the effect of intra-operative Lasix on sodium excretion (NaEx) in children following cardiac surgery after cardiopulmonary bypass (CPB).


Thirty-six children (median age 5.9 months, range 0.06–182 months) underwent corrective cardiac surgery for congenital heart disease (CHD). The patients were divided into two groups. Group A (n = 12) received 1 mg/kg of intravenous Lasix at the end of the surgical operation, Group B did not receive Lasix and acted as the control group. Urine samples were collected over the 1st (t = 0) and 16th (t = 16) postoperative hour and sent with paired blood samples for electrolyte measurements. Sodium excretion (NaEx) and urine volume (ml/kg/h) was compared between the two groups at t = 0 and t = 16 using the Mann-Whitney test. NaEx was calculated by multiplying urine volume by urine Na concentration and expressed as mmoles/kg/h.


There were no significant differences in age, weight, pre-operative renal function, CPB times or underlying heart disease (cyanotic vs acynotic) between the two groups.

NaEx and urine volume were significantly greater at t = 0 in the group that received Lasix (P = 0.013 and P = 0.001 respectively). These differences were no longer present at the 16th postoperative hour (P = 0.67 and P = 0.38 respectively). In both groups sodium excretion correlated with urine volume (r = 0.98).


Although intraoperative Lasix transiently increases sodium excretion and therefore urine volumes in the immediate post operative period it does not appear to offer any advantage by the 16th postoperative hour, a time when renal water and sodium conservation is maximal.

figure 1

NaEx plotted against urine volume at t = 0 and t = 16. Blocks indicate median values, whiskers indicate 95%CI.

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Durward, A., Haq, S., Anderson, D. et al. The effect of intraoperative Lasix on sodium excretion following cardiac surgery. Crit Care 3 (Suppl 1), P210 (2000).

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