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Effect of Intravenous Phenobarbital on Left Ventricular Myocardial Contractility Determined by Echocardiography in
Arpan R Doshi1,2, Monesha Gupta Malhotra3, Duraisamy Balaguru4
1Children's Mercy Hospital & Clinics, Wichita, KS.
Insights
Intravenous phenobarbital loading can temporarily decrease heart function in children. This effect on ejection fraction (EF) was transient, returning to baseline within 24 hours in most cases.
Area of Science:
- Pediatric Cardiology
- Pharmacology
- Critical Care Medicine
Background:
- Limited data exists on the cardiac effects of intravenous phenobarbital in children.
- Animal and rare human studies suggest barbiturates may negatively impact cardiac function.
- Intravenous phenobarbital is commonly used in pediatric clinical practice.
Purpose of the Study:
- To evaluate the effect of intravenous phenobarbital loading on myocardial systolic function in children.
- To assess changes in left ventricular ejection fraction (EF) following phenobarbital administration.
Main Methods:
- Prospective pilot study involving children under 18 receiving IV phenobarbital loading (≥20 mg/kg).
- Echocardiograms measured ejection fraction (EF) before, 30 minutes after, and before the maintenance dose of phenobarbital.
- Linear mixed modeling analyzed EF changes over time; significant blood pressure drop defined as ≥20 mmHg systolic.
Main Results:
- Ten children (70% female, age 2 days to 8.2 years) were enrolled.
- Three children experienced hypotension (systolic BP drop >20 mmHg).
- Left ventricular EF showed a statistically significant, transient decrease post-phenobarbital, returning to baseline.
Conclusions:
- Intravenous phenobarbital has a direct, transient depressant effect on myocardial systolic function in about one-third of pediatric patients.
- The observed depression in EF was temporary, with recovery to baseline within 24 hours.
- Close monitoring for decreased cardiac function is recommended during IV phenobarbital use in children.
Introduction:
Animal studies and rare human studies have suggested a negative effect of barbiturates on cardiac function. Although intravenous (IV) phenobarbital is used routinely in children in the clinical setting, studies in children are lacking. We performed a study to evaluate effect of IV phenobarbital loading on myocardial systolic function of children.
Methods:
In a prospective pilot study in children without congenital heart defects, the effect of IV phenobarbital was evaluated on the left ventricular systolic function measured by ejection fraction (EF) by Simpson's method via an echocardiogram. Any child less than 18 years of age who received IV loading dose of at least 20 mg/kg of phenobarbital given as an infusion over 20 - 30 minutes for various medical indications was eligible to take part in the study. Three measurements of EF by an echocardiogram were made: before loading dose, 30 minutes after completion of the loading dose, and prior to the first maintenance dose. Relevant clinical data were recorded, including vital signs, immediately prior to each echocardiogram. Change of function as measured by EF over time was analyzed using linear mixed modeling methods. For this study, significant change in blood pressure was defined as a drop of at least 20 mmHg in systolic blood pressure.
Results:
Ten children (70% female, age range two days to 8.2 years) were enrolled. Three had hypotension with a drop of systolic blood pressure greater than 20 mmHg from baseline. On examining the trajectory of EF on each individual graphically, the left ventricular EF tended to fall immediately following phenobarbital therapy and return to baseline on re-evaluation. These trajectories were statistically significant for EF.
Conclusions:
Phenobarbital had a direct and transient depressant effect on systolic function of the myocardium in one third of the cases. The depression in EF appeared to be transient with return to baseline in less than 24 hours. We recommend close monitoring with anticipation of decreased function in children when using IV phenobarbital.
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