1 Nottingham, UK 2 Durham, NC, USA
EditorIn the case reported by Olufolabi and colleagues1 of Caesarean section in a woman with complex arrhythmias and an implantable cardioverter defibrillator, I was surprised that anaesthesia comprised of a conventional thiopental/succinylcholine induction and nitrous oxide/isoflurane maintenance. The authors acknowledged that regional anaesthesia avoids the arrhythmogenic and cardiac depressant effects of volatile agents, but omitted to mention that an opioid-based general anaesthetic regimen with remifentanil,2 3 can reduce or eliminate the need for vapour without risking the sympathetic blockade associated with a regional block. The fetal effects of anaesthetic and analgesic agents are innocuous and reversible.4 There is no need to restrict doses for women with cardiac or cerebrovascular disease requiring Caesarean section on account of fetal concerns. Fetal well-being depends on maintenance of haemodynamic stability and avoidance of aortocaval compression, hypoxaemia and hypercarbia. As all babies born to high-risk mothers will be delivered into the hands of a neonatal paediatrician for ventilatory support, any opioid-induced respiratory depression should be of little or no consequence.
Two final points: it was suggested that epidural anaesthesia might be preferable to a spinal block because a more controlled onset of effect is possible. Incremental spinal anaesthesia via an intrathecal catheter might confer a better quality of anaesthesia with a similar degree of haemodynamic control but no risk of local anaesthetic toxicity.5 Lastly, the authors stated that routine anti-reflux prophylaxis was administered. Antacid therapy is routine in UK obstetric practice, but anti-reflux therapy is not. What did the patient receive?
D. M. Levy
Nottingham, UK
EditorWe thank Dr Levy for his response and are grateful for the opportunity to reply. Opioid-based anaesthesia is a valid alternative and indeed, the effects of opioid-type drugs on the fetus are well known and reversible. It is, however, not practical to entirely eliminate the need for vapour because of the risk of awareness, as one of his referenced articles, in which nitrous oxide and isoflurane were used, confirmed.3 Furthermore, the induction of anaesthesia to delivery time period for Caesarean section can be significantly shortened in experienced surgical hands, after which opioids can be promptly introduced, and the concentration of the volatile agent reduced. The short interval reduces the likelihood of high blood concentrations of isoflurane, should one be particularly concerned.
Remifentanil has been extensively used by the first author (AJO).68 Despite its unique pharmacokinetic profile, it may not be the ideal opioid for Caesarean section, because of the problem of inadequate pain control in the postoperative period.9 10 At the time of this case, it was not available to us in our institution. We agree with Dr Levy that continuous spinal anaesthesia is an option. We refer him to the case report referenced in our article.11
Finally, the patient received ranitidine 150 mg the night before and early on the morning of surgery, with 30 ml sodium citrate before induction. Clearly, this is antacid medication although one is aiming to prevent reflux of hazardous stomach contents.
A. J. Olufolabi
G. A. Charlton
Durham, NC, USA
References
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