Effect of Intravenous Phenobarbital on Left Ventricular Myocardial Contractility Determined by Echocardiography in Children

Abstract

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.xIn 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.
Kans J Med 2019;12(2):40-44.