Emergency Caesarean section – best practice

We were interested to read the review article by Dr Levy describing ‘best practice’ for emergency Caesarean section [1]. We feel, for the most part, it is a useful summary of the current issues and practices surrounding category 1 or 2 (‘emergency’) sections. It will, no doubt, be an aid to all obstetric anaesthetists, and more especially to those of us who only cover obstetrics whilst ‘on-call’. However, we feel the review falls somewhat short of hitting its ‘best practice’ target in two areas. Firstly, when considering ‘topping-up’ a labour epidural for an emergency Caesarean section Dr Levy dismisses the role of a lidocaine : epinephrine mixture (with or without bicarbonate) and states his preferred choice of local anaesthetic to be levobupivacaine due to it being ‘less cardiotoxic than racemic bupivacaine in the event of accidental intravascular injection’. As Dr Levy states, the issue of whether the demonstrable benefits outweigh the risks of adding bicarbonate and/or epinephrine to a sole local anaesthetic or mixture of local anaesthetics has been explored recently [2]. This study demonstrated that the preparation time for plain bupivacaine is shorter than for the lidocaine mixture (1.25 min vs 3 min), but this was counteracted by the shorter time for the lidocaine mixture to achieve surgical anaesthesia (13.8 min vs 17.5 min). Whilst this suggests no significant advantage in the use of the lidocaine mixture over plain bupivacaine in terms of speed of onset of anaesthesia, the conclusion of the article that the ‘lidocaine solution is cheaper and less toxic (in the event of accidental intravascular injection) than the alternatives’ weakens the argument for Dr Levy's preference for levobupivacaine on the grounds of safety. The choice of an epinephrine-containing local anaesthetic solution may also permit earlier identification of an intravenously placed epidural catheter at the time of a test dose (though the induced tachycardia may be difficult to identify in a labouring woman) – further enhancing the safety profile of lidocaine : epinephrine mixtures over plain bupivacaine. Further, epidural lidocaine solutions have been shown to produce a more profound motor block than bupivacaine [3], producing operative conditions closer to that provided by spinal anaesthesia. The use of a lidocaine solution (the agent of choice of our institution) does introduce the risk of drug errors and infection, though to our knowledge no work has been completed to elucidate these. The antimicrobial properties of local anaesthetic solutions have, however, been documented for more than 25 years. In vitro studies [4] have demonstrated a dose-dependent inhibition of bacterial growth by lidocaine (with or without epinephrine) for a variety of nosocomial infections, including MRSA and vancomycin-resistant enterococci. The clinical significance of this to obstetric practice, however, remains undetermined. The risks have been reduced to a minimum in our hospital by our use of a laminated, printed formula for the lidocaine mixture (17 ml lidocaine 2%, 2 ml bicarbonate 8.4%, and 1 ml epinephrine 1 in 10 000) attached to the cupboard where all three drugs are stored, and by drawing up the solution only when it is required. The use of plain bupivacaine could prevent these problems but this must be tempered by the higher failure rates (23–43%) when using plain bupivacaine ‘top ups’[5, 6]. Second, we feel the recommended intrathecal diamorphine dose of 0.25 mg, which was advocated on the basis of the ease of preparation, is unduly conservative. The NICE Caesarean section guideline recommends an intrathecal dose of 0.3–0.4 mg diamorphine as this reduces the need for supplemental analgesia peri-operatively [7]. Saravanan et al. found that the ED95 of diamorphine to prevent intra-operative supplementation of anaesthesia was 0.4 mg [8], and increasing the dose to 0.5 mg gave modest additional benefit, accompanied by a small increase in nausea, vomiting and pruritus. Other dose-finding studies have examined up to 0.3 mg [9], 0.375 mg [10] and 1 mg [11] intrathecal diamorphine and found increasing analgesia with increasing dosage. An empty 1-ml syringe in the sterile pack allows 0.6 or 0.8 ml of the 0.5 mg.ml−1 diamorphine solution (described by Dr Levy) to be measured accurately, providing 0.3 and 0.4 mg of diamorphine, respectively. Alternatively, 1-ml syringes containing a set dose of diamorphine solution can be prepared by pharmacy in sterile packs and handed to the anaesthetist, negating the need for drawing-up this solution.