COMPARISON OF INTRATHECAL BUPIVACAINE VERSUS COMBINATION OF BUPIVACAINE AND KETAMINE FOR LOWER LIMB SURGERIES

Abstract

This study was conducted on sixty patients to compare the effects of intrathecal
hyperbaric bupivacaine and a combination of intrathecal hyperbaric bupivacaine
and ketamine for lower limb surgeries.
The patients classified as American Society of Anaesthesiologists (ASA) Health
Status classification I and II aged between 18-60 years and scheduled for elective
lower limb surgeries were studied.
They were randomly allocated by blind balloting to one of the two groups. Spinal
anaesthesia was achieved in the sitting position with 15mg of 0.5% hyperbaric
bupivacaine with or without 0.3mg kg-1 preservative free ketamine. The final
volume of drug administered was made up to 3.5ml by adding normal saline in both
groups. Group B received intrathecal bupivacaine while group BK received a
combination of bupivacaine and ketamine.
The parameters assessed were: Onset and duration of sensory and motor blockade,
maximum sensory level achieved, the numerical rating scale, time to first analgesic
request and the total analgesic consumption were recorded. The arterial blood
pressure, heart rate as well as the adverse effects were also recorded.

Most of the findings were comparable in both groups with an earlier onset of
sensory and motor blockade in the ketamine-bupivacaine group when compared
to the bupivacaine only group.
None of the patients complained of pain in the intraoperative period. It was
observed that prior to 120 min postoperative period, there was no significant
difference in number of patients who had NRS value of 4 or above between the 2
groups (p>0.05). At 120 minutes post operatively, a significant number of patients
in the ketamine-bupivacaine group compared to the bupivacaine only group had a
NRS of 4 or above, p=0.02. The mean duration of first analgesic requirement (time
from spinal injection of drug to when the first analgesic dose was administered)
was insignificant, p=0.99. The mean total analgesic consumption (mg) in 24 hours
was significantly higher in the ketamine-bupivacaine group compared to the
bupivacaine only group, p=0.00.
A comparable decrease from the baseline of the mean arterial blood pressure,
mean systolic blood pressure, mean diastolic blood pressure and the mean pulse
rate was observed in the ketamine-bupivacaine group and the bupivacaine only
group following subarachnoid block. A significant difference between the groups in
the mean arterial blood pressure was observed at 50 minutes (p-0.02), 70 minutes
(p-0.03) and 150 minutes (0.01) respectively. This may be attributed to
haemodynamic instability resulting either from inadequate fluid administration or
ongoing blood loss intraoperatively.
Intrathecal ketamine with bupivacaine produced a quicker onset of sensory
blockade and motor blockade with adequate anaesthesia. In addition unlike the
group administered bupivacaine only, ketamine ensured a stable cardiovascular
status with no vasopressor drug administered which may be an advantage in
emergency operations with haemodynamic instability.