The space blanket and shivering during extradural analgesia in labour

The incidence of shivering in women during epidural analgesia in labour is up to 33%, and may be highly distressing. Its mechanism is unclear, but the most widely held theory is that it is thermogenic. Pharmacological suppression may adversely effect the foetus or induce maternal hypothermia, and although physical remedies such as direct heat application are effective, they are also expensive and cumbersome. We recently found that the space blanket, a simple aluminised metallic foil, used pre-emptively, reduces shivering after general anaesthesia. We investigated the effect of the space blanket on the incidence and intensity of shivering, axilliary skin temperature, and subjective perception of cold during epidural analgesia for labour in 50 women over a four-hour time frame. Patients were randomised into group 1, who were wrapped in a space blanket immediately after commencement of epidural analgesia with bupivacaine, and group 2 (matched controls). Shivering was defined as visible tremor of the head, neck, trunk or limbs as observed by the attending midwives. Twenty-nine percent of group 1 and 35% of group 2 shivered (not significant), but a reduction in shivering intensity was observed in group 1 (P < 0.05). There was no significant difference in skin temperatures in either group, and no significant temperature change within the groups. Both groups had similar thermal comfort scores throughout the study, which correlated poorly with the presence of shivering. We conclude that there is no benefit in application of the space blanket to reduce epidural-analgesia related shivering in labour, which may indicate a non-thermogenic mechanism for this phenomenon.