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Continuous intravenous furosemide in haemodynamically unstable children after cardiac surgery
M M van der Vorst1, I Ruys-Dudok van Heel, J E Kist-van Holthe
1Department of Paediatrics, Leiden University Medical Centre, PO Box 9600, 2300 Leiden, The Netherlands. M.M.J.van_der_Vorst@lumc.nl
Insights
Continuous intravenous furosemide dosing in pediatric cardiac surgery patients may be optimized. A higher starting dose, guided by urine output, may be more rational than gradual increases, potentially improving outcomes in unstable children.
Area of Science:
- Pediatric Cardiology
- Pharmacology
- Nephrology
Background:
- Continuous intravenous furosemide dosing after pediatric cardiac surgery is often empirical.
- Hemodynamically unstable children with transient renal insufficiency may require optimized dosing.
- Current dosing schedules may not be ideal for this vulnerable population.
Purpose of the Study:
- To investigate clinically applicable measures for rationalizing continuous intravenous furosemide therapy in pediatric cardiac surgery patients.
- To evaluate the impact of different dosing strategies on outcomes.
- To inform the development of evidence-based dosing protocols.
Main Methods:
- Open study involving twelve pediatric patients (0-33 weeks) post-cardiac surgery receiving 3 days of continuous intravenous furosemide.
- Collection of blood and urine samples for furosemide, creatinine, and electrolyte levels.
- Measurement of fractionated urinary output and furosemide levels using high-performance liquid chromatography (HPLC).
Main Results:
- Mean starting dose was 0.093 mg/kg/hr, increased to 0.175 mg/kg/hr on day 2, and 0.150 mg/kg/hr on day 3.
- Infusion rates increased from day 1 to day 2 in ten patients; decreased from day 2 to day 3 in three.
- Serum furosemide levels remained below ototoxic levels; urinary excretion correlated inversely with serum creatinine.
Conclusions:
- Continuous intravenous furosemide is beneficial for hemodynamically unstable pediatric cardiac surgery patients.
- Furosemide's efficacy is renal function-dependent, suggesting optimization is possible.
- A higher starting dose (e.g., 0.2 mg/kg/hr) adapted downward based on urine output may be more rational than gradual increases.
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.