A Comparison of Phenylephrine Administration between Intravenous Bolus and Slow Injection in Treatment of Spinal Anesthesia-Induced Hypotension on Bradycardia and Other Side Effects in Patients Undergoing Cesarean Section: A Randomized, Single-Blind Study
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Abstract
Background: Phenylephrine is currently recommended
for the management of spinal anesthesia-induced
hypotension due to fetal acid-base status improvement.
However, it induced bradycardia, which was a surrogate
outcome of cardiac output.
Objectives: To compare the incidence of bradycardia and
the other side effects between Intravenous (IV) bolus and
a slow injection of phenylephrine administration
Methods: One hundred and eighty-six parturients
undergoing elective cesarean section who had hypotension
following spinal anesthesia were randomized into two
groups. Group B received IV bolus injection of phenylephrine
100 mcg in 10 ml. Group S received continuous IV slow
injection of phenylephrine 100 mcg in 10 ml within 30
seconds with opening three ways of 3-way stopcock to
imitate the function of a syringe pump. Bradycardia was
treated with atropine 0.6 mg. The other side effects were
recorded.Results: The incidence of bradycardia was significantly
higher in group B than group S (9, 9.7% vs 1, 1.1%; P = 0.009).
All bradycardia in Group B had heart rate 46-60 bpm with
hypotension and no associated with pressing on the
fundus to assist in the birth (uterine compression). But,
one case in Group S had heart rate < 45 bpm, which
related to uterine compression. There was no statistically
significant difference in the total dose of phenylephrine
administration, reactive hypertension, cardiac arrhythmia,
neonatal Apgar score at 1 and 5 minutes, and birth weight
between two groups.
Conclusions: Slow injection of phenylephrine within
30 seconds to imitate the function of a syringe pump can
significantly lower the incidence of phenylephrine-induced
bradycardia than bolus injection in the treatment of spinal
anesthesia-induced hypotension.
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