Safe dose of local anaesthetic for transversus abdominis plane block

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I read with interest the letter by Nash et al. [1] describing a novel modification to the transversus abdominis plane (TAP) block for breast reconstruction utilising abdominal wall tissue. The description of their technique involves the administration of 40 ml racemic bupivacaine 0.5% to 10 patients without reference to individual patient characteristics such as body weight. The adverse consequences of high plasma local anaesthetic concentrations are well described, as is the safety profile of racemic bupivacaine compared with other local anaesthetic agents. Local anaesthetic toxicity has been described following injudicious quantities of local anaesthetic used for TAP block [2] and Griffiths et al. have recently demonstrated plasma concentrations of ropivacaine, following TAP block with 3 mg.kg−1, as potentially neurotoxic [3]. Guidance from the American Society of Regional Anesthesia advises that a regional technique should be ‘tailored to the minimum mass of local anesthetic molecules necessary to achieve the desired clinical effect’ [4]. The studies referred to by Nash et al., that demonstrate a reduction in postoperative opioid requirement and/or pain scores following TAP block with bupivacaine, do so using significantly less local anaesthetic than in their report [5]. The TAP block is a regional technique with significant clinical utility as demonstrated by Nash et al. However, its benefits can be realised using smaller quantities of agents that are considered to be less toxic.