SHIVERING DURING CAESAREAN DELIVERY UNDER SPINAL ANAESTHESIA: THE ROLE OF PETHIDINE ADDED TO INTRATHECAL BUPIVACAINE
Shivering is a common and quite distressing complication of spinal anaesthesia. It does interfere with patient monitoring and markedly increases the metabolic rate. Traditionally, shivering has been aborted with intravenous pethidine. Recently, the addition of pethidine to the local anaesthetic intrathecal injectate has been shown to reduce the incidence and severity of post spinal shivering without modifying the characteristics of the block but may increase opioid related side effects.
RATIONALE AND HYPOTHESIS:
The determinations of the dose of intrathecal opioids that will prevent shivering without showing opioid related side effects will improve patient’s safety. The efficacy of 0.1mg/kg of pethidine added to intrathecal bupivacaine injectate in ameliorating post spinal shivering was evaluated.
This is a prospective randomized double blind placebo controlled trial. Approval was sought and received from UBTH Research and Ethics Committee. A prehoc power analysis indicated the recruitment of 42 patients in each group to detect a 30% reduction in the incidence of shivering (α = 0.05, β = 0.2). A 5% attrition level was assumed and eighty-eight subjects were drawn from ASA 1 or 2 patients scheduled for elective caesarean delivery in UBTH, Benin City. Exclusion criteria included height <152cm or >183cm, weight >110kg, use of opioid analgesics in the past 24hours and presence of intercurrent illness.
Following informed consent, they were randomized to receive a standardized spinal anaesthesia using 2.2mls of 0.5% bupivacaine to which was added either 0.1mg/kg of pethidine (Group P) or an equivalent volume of normal saline (Group S). The presence of shivering and its severity, core temperature and patients cold score, highest sensory dermatomal level of block and opioid related side effects and perioperative complications were recorded. The data obtained were analysed using Statistical Programme for Social Sciences (SPSS) 16.0 software (Chicago Illinois, USA). Demographic data was compared using Fisher’s exact test. Proportions of women that shivered was compared using Fisher’s exact test while the maximal intensity of shivering recorded for each patient is studied with Mann Whitney U-test. The relationship between minimal temperature and shivering, and cold scores and shivering were determined with Spearman Correlation coefficient. The level of significance was set at a probability of 5%. All tests were two tailed.
Eigthy-eight women were randomized to the pethidine group and saline group. There was no significant difference in the sociodemographic characteristics and the intraoperative clinical variables between the groups. There was a significant reduction in the incidence of shivering in the pethidine group [33% versus 71%; (p < 0.0009) Fisher’s exact test], the maximal intensity recorded for each patient [(p < 0.004) Mann Whitney U test]. There was no significant difference in the incidence of opioid related side effects and perioperative complications (p > 0.49).
This study showed that addition of 0.1mg/kg of pethidine to the intrathecal bupivacaine reduces the incidence and severity of shivering significantly with a minimal side effect profile.
This study provided data that suggest 0.1mg/kg of pethidine added to the local anaesthetic spinal injectate significantly reduces the incidence and severity of post spinal shivering. This is important as patients will thus be spared the obnoxious effects of shivering and opioid related side effects. The present practice of aborting shivering when it has already occurred is obviously inferior.