Continuous intravenous furosemide in haemodynamically unstable children after cardiac surgery

OBJECTIVE

The commonly used continuous intravenous (i.v.) furosemide dosing schedule after cardiac surgery in children is largely empirical and may not be optimal. This may even be more marked in children after cardiac surgery who are haemodynamically unstable, and in whom transient renal insufficiency may occur. A study was performed to obtain an impression regarding which clinically applicable measures may be used to design a rational scheme for continuous i.v. furosemide therapy in children after cardiac surgery.

SUBJECTS AND METHODS

Twelve paediatric patients (5F/7 M, age 0-33 weeks) post-cardiac surgery, who were to receive 3 days of continuous i.v. furosemide treatment, were included in an open study. Blood and urine samples were taken for furosemide, creatinine, and electrolyte levels, and fractionated urinary output was measured. Furosemide in blood and urine was measured using high performance liquid chromatography (HPLC).

RESULTS

The mean starting dose of continuous i.v. furosemide was 0.093 (+/- 0.016) mg/kg per hour. The mean dose was increased to 0.175 (+/- 0.045) mg/kg per hour per hour on day 2, and changed to 0.150 (+/- 0.052) mg/kg per hour on day 3. Infusion rates were increased from day 1 to day 2 in ten cases, and decreased from day 2 to day 3 in three cases. Serum furosemide levels never exceeded ototoxic levels. The urinary furosemide excretion rate was inversely related to serum creatinine levels.

CONCLUSIONS

This study extends the observation of the beneficial effects of continuous i.v. furosemide also to those children who are haemodynamically unstable after cardiac surgery. However, as the effects of furosemide are dependent on renal function, it can be hypothesised that the dosing schedule may be optimised. Contrary to the currently used dosage schedule in which the dose of furosemide is gradually increased over time, it may be more rational to start with a higher dose and adapt this dose (downward) guided by the observed effect (urine output). Because the infusion rate was increased to 0.2 mg/kg per hour in nine out of 12 patients on day 2 and was never increased further, this suggests that a starting rate of 0.2 mg/kg per hour may be optimal.

[Clinical drug research in children: current international guidelines. Committee for Proprietary Medicinal Products]

Drugs research in children entails a number of problems: medical-ethical, pharmacological (owing to the immaturity of the organs and the growth and development of the child) and financial (because children do not use many drugs). Consequently, children are exposed to insufficiently tested drugs and new therapeutic possibilities are withheld from them. Currently, little clinical drugs research in children is being carried out, but this is about to change. By now, European guidelines have been drawn up for the performance of clinical drugs trials according the 'good clinical practice' standards in children. In the Netherlands, a cooperative body has been set up (the Pediatric Pharmacology Network), which is to promote and coordinate paediatric pharmacological research in according with these guidelines.

Clinical outcome of small for gestational age preterm infants

Data from 55 preterm SGA infants and 55 preterm AGA infants matched for gestational age and sex were reviewed retrospectively. An increased incidence of perinatal hypoxia (30 vs. 18), gastrointestinal problems, minor infections (27 vs. 9), hematological problems and increased mortality (21.8% vs. 7.2%) was observed in the SGA infants. The incidence of HMD was higher in the AGA group (not significant), but the HMD was much more severe in the SGA group. Mortality as a result of HMD was significantly higher in the SGA group. The percentage of handicapped children is 19% in the SGA group and 9% in the AGA group. The percentages of severely handicapped children are 4.8% and 2.3% respectively. The combination of prematurity and severe intrauterine growth retardation in the SGA group caused a higher mortality and morbidity than was seen in their AGA controls. This clinical performance of SGA preterm infants is important especially for those who have to decide at what moment such a child should be delivered by caesarean section.