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Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, yusc1@hotmail.com Department of Anesthesia, United Christian Hospital, Kwun Tong, Hong Kong
To the Editor:
Roy et al. (1) recently reported that addition of intrathecal meperidine during spinal anesthesia for cesarean delivery is effective in reducing the incidence and severity of shivering without increasing side effects. We believe that their findings should be interpreted with caution in the light of other published papers on the use of intrathecal meperidine in obstetric anesthesia (2,3).
The authors criticized the use of IV meperidine for treatment of shivering because it could be associated with side effects. However, we believe that the same consideration should apply equally to the use of intrathecal meperidine. They reported that 0.2 mg/kg meperidine—a relatively large dose—was not associated with an increase in nausea and vomiting. However, they did not provide supporting data. Their finding is contrary to those of other studies that have shown that intrathecal meperidine causes nausea and vomiting when given to parturients (2,3). Previously, we found that addition of 10 mg intrathecal meperidine to bupivacaine at cesarean delivery was associated with nausea and vomiting in 11 of 20 (55%) patients compared with 3 of 20 (15%) patients who received saline placebo (3).
Roy et al. (1) reported a frequent incidence of shivering in patients who received saline placebo (17 of 20 patients). However, they classified patients as having shivering if they scored 1 or greater on a scale of 0 to 4. According to this scale, which was originally devised to assess patients recovering from general anesthesia (4), patients were graded "1" when there was "piloerection or peripheral vasoconstriction but no visible shivering." During spinal anesthesia, peripheral vasoconstriction in the upper body is a normal compensatory physiological response to vasodilatation in the lower body and does not necessarily reflect a clinically important shivering response. Roy et al. (1) stated that shivering is uncomfortable for patients and may interfere with monitoring. However, if there is no visible shivering, these problems are unlikely. Arguably, patients graded "2" (muscular activity in only one muscle group) could also be considered to have only a mild disturbance. Therefore, the actual clinical problem is unlikely to be as great as the authors suggest, which is supported by our own clinical experience. This should be taken into account when considering the risk:benefit ratio of giving prophylactic intrathecal meperidine. Interestingly, in our study, we also assessed shivering; however, we classified patients as having shivering only when this was visible to the investigators and found that the reduction in incidence in patients who received meperidine was not statistically significant (3 of 20 patients versus 8 of 20 patients).
We agree that further evaluations of intrathecal meperidine using smaller doses and larger sample sizes are required. Meanwhile, readers should continue to be mindful of potential side effects when contemplating use of intrathecal meperidine in obstetrics.
References
Département d’Anesthésiologie, Hôpital Maisonneuve-Rosemont, Montréal, Canada, michel.girard.2@umontreal.ca
In Response:
We thank Yu et al. for their interest in our article. In our study, no difference in the incidence of nausea was noted, as reflected by the similar doses of metoclopramide used in each group. It is always difficult to compare results from different studies; populations differ, surgical technique may differ, and the extent of abdominal exploration may differ in each study. However, in each of our studies (1,2), nausea and vomiting were secondary outcomes, thus larger groups of patients will be necessary for a definitive answer on this issue. In the study by Booth et al. (3), doses of 15–25 mg of meperidine were used and patients were in labor, which increases the incidence of nausea and vomiting.
Shivering was graded with a scale described by Crossley and Mahajan (4). Most of our patient were graded 2 ("muscular activity in only one muscular group") and above. This is enough to make patients uncomfortable, and therefore reduction of this shivering is an advantage.
Although we understand the reticence of Yu et al. in giving prophylactic intrathecal meperidine, we believe that under proper conditions, this provides the parturient with excellent anesthetic and analgesic conditions with few side effects, while providing the added comfort of preventing shivering.
References
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