Ondansetron versus Ephedrine for prophylaxis of subarachnoid Block-Induced Hypotension in Pregnant women.
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Date
2025
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Publisher
Zambia Medical Association.
Abstract
Background: Hypotension is the most frequent
adverse effect of subarachnoid block (SAB) in
patients undergoing elective caesarean section
(C/S), presenting a significant challenge to both
maternal and foetal safety. It is believed that the
Bezold-Jarisch reflex (BJR), triggered by serotoninmediated
stimulation of 5-hydroxy-triptamine-3 (5-
HT3) receptors in cardiac chambers, could be a
contributor to the mechanism of SAB-induced
hypotension. Therefore, the use of ondansetron, a 5-
HT3 receptor antagonist, holds promise in
mitigating this type of hypotension.
Objective: The aim of this study was to compare the
efficacy of prophylactic intravenous 4 mg
ondansetron versus intravenous 15 mg ephedrine in
reducing the incidence of SAB-induced hypotension
in patients scheduled for elective caesarean section
at the University of Ilorin Teaching Hospital.
Methodology: This randomised controlled trial
included 80 ASA 2 patients, between 18 and 40
years, who were scheduled for elective C/S under
SAB. Participants were allocated to 2 groups of 40:
Group OS received 4 mg intravenous ondansetron
10 minutes before SAB, and Group ES received 15
mg intravenous ephedrine immediately after SAB.
The primary outcome measure was the incidence of
hypotension while secondary outcome measures
were quantity of phenylephrine and atropine
consumption, incidence of post-spinal spinal
shivering, and study drug side effects: hiccups, skin
flushing, and headaches.
Data Analysis: Statistical analysis was conducted
using the Statistical Product and Service Solutions
SPSS Statistic 20 (IBM Corp., Armonk, NY, USA),
employing Chi-square test/ Fisher's exact test) or
independent student's t-test as appropriate. P <0.05
was considered statistically significant.
Results: The demographic characteristics and
baseline haemodynamic parameters were similar
across both groups. Although the incidence of
hypotension recorded in the ephedrine group was
12.5% lower than that recorded in the ondansetron
group, this was not statistically significant (60% in
OS vs 47.5% in ES, 95% confidence interval [CI] = -
0.03 - 0.28, P = 0.37). Notably, the mean systolic
blood pressure (SBP) was significantly higher in the ephedrine group (P< 0.05) at six critical time points.
The mean DBP values were similar in both groups.
Apart from the 4th minute, where the mean arterial
blood pressure (MAP) value was significantly
higher in the ephedrine group (82.73 ± 14.37 in ES
vs 74.65 ± 15.17 in OS, 95% CI = -14.65 - -1.49, p =
0.02), the values were comparable at other times.
The mean heart rate (HR) values were significantly
elevated (P< 0.05) in the ephedrine group at nearly
all-time intervals, barring the second minute. One
patient in the ondansetron group experienced
bradycardia, which was treated with 0.6 mg
atropine, whereas none in the ephedrine had
bradycardia. The mean consumption of
phenylephrine (in μg) was lower in the ES group by
25 μg (77.50 ± 96.71 in group ES versus 102.50 ±
110.33 in group OS, 95% CI = -21.18 - 71.18, P =
0.28) but was not statistically significant.
Interestingly, the percentage of participants in group
OS who experienced shivering was 17.5% lower
compared to the percentage in the ephedrine group
(5% in group OS vs 22.5% in group ES, 95% CI =
0.03 - 0.32, P= 0.023). No significant differences in
the incidences of study drug side effects were noted
between the groups.
Conclusion: Our findings suggest that prophylactic
use of 4 mg intravenous ondansetron has a
comparable efficacy to 15 mg intravenous
ephedrine in preventing SAB-induced hypotension
in pregnant women. However, patients pretreated
with ondansetron before SAB had a significantly
lower incidence of post-spinal shivering, indicating
its potential value in enhancing maternal comfort
and safety during caesarean sections.
Description
Keywords
Bradycardia, ephedrine, hypotension, ondansetron, pethidine, phenylephrine, shivering, subarachnoid block