COMPARATIVE STUDY OF THE EFFICACY OF ONDANSETRON VERSUS TRAMADOL IN THE PREVENTION OF POSTANAESTHESIA SHIVERING FOLLOWING ELECTIVE CAESAREAN SECTION UNDER SPINAL ANAESTHESIA

Abstract

Background:
One of the common complications of regional technique is shivering with an incidence of
around 20-60%. Although shivering may have beneficial thermoregulatory effects, it places the
patient under increased physiological stress. While patients find postanaesthesia shivering very
uncomfortable, it causes artifacts in monitors and increases oxygen consumption, metabolic
rate, heart rate, cardiac output and postoperative pain. This may lead to myocardial ischaemia,
hypoxaemia, hypercarbia and lactic acidosis that could complicate recovery from anaesthesia.
Preventing postanaesthesia shivering may reduce morbidity and improve patient’s satisfaction.
Aim and Objectives:
This study compared the efficacy of ondansetron versus tramadol in the prevention of
postanaesthesia shivering following elective Caesarean section under spinal anaesthesia.
Patients and Method:
This was a prospective, double-blind, randomized controlled trial of prophylactic intravenous
ondansetron versus tramadol for the prevention of postanaesthesia shivering. ASA physical
status 1 or 2 eligible patients, with singleton pregnancies, aged between 18 and 45 years who
were scheduled for elective Caesarean section, were randomly allocated to 3 groups.
Each patient was premedicated with 10mg metoclopramide and 150mg ranitidine orally. In the
theater, the patients were preloaded with 15ml/kg of normal saline at room temperature. Spinal
anaesthesia was induced in the sitting position with 2.5ml of 0.5% hyperbaric bupivacaine.
Two minutes after spinal block and prior to surgical incision, the study drugs were administered
to the patients. Group A received 4mg ondansetron, group B received 0.5mg/kg tramadol, while
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the group C (control group) received normal saline. All study drugs were made up to 5ml and
given intravenously. Intraoperatively, the heart rate, blood pressure, respiratory rate, ECG, core
and skin temperatures were monitored and recorded for each.
The primary outcome variable which was the incidence of postanaesthesia shivering was
observed from institution of SAB to discharge from the recovery room. Secondary outcome
variables such as neonatal Apgar scores at 1min and 5min, hypotension, sedation, PONV, pain,
PDPH, and backache were also evaluated.
Results:
Ninety patients participated in the study. The incidence of shivering was 20.0% in the
ondansetron group, 16.7% in the tramadol group and 53.3% in the saline group (p = 0.003).
This gives an overall incidence of shivering of 30%. The relative risk of developing shivering
with saline compared to ondansetron is 2.65, with saline compared to tramadol is 3.12 and with
ondansetron compared to tramadol is 1.18. The number needed to treat (NNT) is 2.9 for
ondansetron and 2.7 for tramadol.
Eight parturient in the saline group had severe shivering compared to one in the ondansetron
group and none in the tramadol group (p = 0.007). The core temperatures at 90min were
significantly lower compared to baseline for ondansetron group (35.97 ± 0.41oC vs. 37.01 ±
0.25; p = 0.0001), for the tramadol group (36.28 ± 0.35oC vs. 37.13 ± 0.24oC, p = 0.0001) and
for the saline group (36.12 ± 0.37oC vs. 37.00 ± 0.27oC, p = 0.0001).
Seven patients in the tramadol group had significant PONV compared to 1 patient in the
ondansetron and 2 patients in the saline groups (p = 0.031). Time to first analgesic requirement
was significantly longer in the ondansetron (87.83 ± 26.45min) and the tramadol groups (94.38
± 21.94min) compared to the saline group (62.44 ± 11.50min); p = 0.009. About 76.7% of the
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patients in the ondansetron group were very satisfied with the prophylaxis of PAS compared
to 70% of the patients in the tramadol group and 26.7% of the patients in the saline group (p =
0.001).
Conclusion:
The prophylactic use of i.v ondansetron 4mg was comparable to i.v tramadol 0.5mg/kg in
protecting parturients against spinal anaesthesia-induced perioperative shivering than placebo.
Furthermore, ondansetron is superior to tramadol in protecting against PONV in parturients.
Ondansetron resulted in no side effects either to the parturient or to the neonate. It is suggested
that ondansetron at a dose of 4mg may be considered for prophylaxis against PAS particularly
in parturients undergoing Caesarean section under subarachnoid block.

COMPARATIVE STUDY OF THE EFFICACY OF ONDANSETRON VERSUS TRAMADOL IN THE PREVENTION OF POSTANAESTHESIA SHIVERING FOLLOWING ELECTIVE CAESAREAN SECTION UNDER SPINAL ANAESTHESIA