EFFECTS OF A LOW DOSE INTRATHECAL NEOSTIGMINE COMBINED WITH BUPIVACAINE-FENTANYL IN MALE ADULTS FOR ELECTIVE LOWER ABDOMINAL (UROLOGIC, ORTHOPAEDIC AND GENERAL) SURGERY
Abstract
BACKGROUND: The spinal route of analgesia has consolidated its place as a major
modality in the management of acute and chronic pain. The search for ideal additives to
local anaesthetic agents to prolong the analgesic effects poses a challenge to the
anaesthetists. Neostigmine, an anticholinesterase, presents a novel approach to providing
analgesia. Neostigmine, when administered intrathecally, inhibits breakdown of an
endogenous spinal neurotransmitter, acetylcholine, thereby inducing analgesia.
OBJECTIVE: This study was designed to determine the duration of analgesia and
haemodynamic changes provided by intrathecal administration of a low-dose neostigmine
added to 0.5% hyperbaric bupivacaine and fentanyl combination in male patients who
had orthopaedic, urologic and general surgical procedures.
PATIENTS AND METHODS: After the UI/UCH Ethics Committee and the NPMCN
approval, consent was obtained from each patient. Sixty male patients belonging to ASA
physical classes status I and II requiring lower abdominal (orthopaedic, urologic and
general) surgery under subarachnoid blocks were studied. The patients were randomized
into two groups. The study group, Bupivacaine-Fentanyl-Neostigmine (BFN) received low
dose preservative-free neostigmine 25micrograms added to 0.5% hyperbaric bupivacaine
15mg and fentanyl 25micrograms intrathecally. The control group, Bupivacaine-Fentanyl
Saline(BFS) received 0.5% hyperbaric bupivacaine 15mg, fentanyl 25micrograms and
0.5mls normal saline intrathecally. The intrathecal drugs were made to the same volume
of 4mls. Subarachnoid block was done in sitting position using 25G or 26G Whitacre
needle. All patients were preloaded with crystalloids at 15mls/kg body weight 20 minutes
before establishing the subarachnoid block. Intraoperatively, fluid maintenance was at
125mls/hr. All patients were adequately monitored intraoperatively with non-invasive
arterial blood pressure, pulse oximeter and ECG.
RESULTS: There were no significant differences in the demographic characteristics
between the two groups. The mean (±SD) duration of effective analgesia (time from
intrathecal injection of study drugs to first dose of analgesic i. e pain score ≥5) was
significantly longer in the study group, 485.6 (±37.6) minutes compared with the control
group, 316.0 (±49.15) minutes. The difference in the duration of effective analgesia was
statistically significant ( p < 0.001). Analgesic consumption 12 hours postintrathecal
injection was also less in the study group, p <0.001.
Haemodynamically, patients in the study group had a relatively stable systolic, diastolic
and mean arterial pressure in the first 15-45 minutes postinjection of the study drugs. In
contrast, the control group had a sharp decline in above variables during same period.
Hypotension occurred in 4 patients (13.8%) in the control and 2 patients (6.7%) in the study
group, this was not statistically significant (p = 0.671). Three patients each in both groups
had bradycardia (HR <55min).
Six patients (20.7%) in the control and 2 patients (6.7%) in the study group shivered
intraoperatively. One patient (3.5%) had nausea while 2 patients (6.9%) vomited in the
control group. None of the patients in the study group had nausea but 1 patient (3.3%)
vomited. Sedation occurred in 2(6.9%) patients in the control (BFS) and none in the study
(BFN) group. One (3.3%) patient in the study group developed pruritus while no patient
itched in the control group.
CONCLUSION: It was found from this study that addition of a low dose 25µg of
preservative- free neostigmine to 15mg of 0.5% hyperbaric bupivacaine and fentanyl 25µg
significantly prolonged the analgesic effects of spinal anaesthesia in male patients who
had lower abdominal surgery. It also appears to offer a more stable haemodynamic profile.
