RESUMO
BACKGROUND: The transversus abdominis plane block has become popular since it has been combined with ultrasound-guided techniques. In abdominal surgery, and especially in subumbilical surgery, it improves postoperative analgesia and reduces morphine consumption. Although it has been shown to be an effective technique, there are wide variations in reported doses and volumes of local anaesthetic used. OBJECTIVE: The primary objective was to assess the median effective analgesic dose (ED50 = effective dose in 50% of patients) of ropivacaine in TAP blocks for patients undergoing reversal of ileostomy. DESIGN: A double-blind up-down dose-finding study. SETTING: French Teaching Hospital. PATIENTS: Twenty-six colorectal patients were included. INTERVENTIONS: After standardised general anaesthesia, a unilateral ultrasound-guided TAP block was performed on patients undergoing elective reversal of ileostomy using 20 ml of ropivacaine. Doses were predefined according to the up-and-down method. The first patient received a dose of 1.6 mg kg(-1). The dose adjustment interval was 0.2 ml kg(-1). The potentially toxic dose of 3 mg kg(-1) was never exceeded. MAIN OUTCOME MEASURE: The primary endpoint was pain (defined as 3 or higher on a numerical pain scale of 0 to 10) at rest 6 h after TAP block. RESULTS: Out of the twenty-six patients who were included in the study, the ED50 of ropivacaine in TAP block for patients undergoing reversal of ileostomy was 2.70 mg kg(-1) [95% confidence interval (95% CI) 2.37 to 3.03 mg kg(-1)]. CONCLUSION: The ED50 of ropivacaine in TAP blocks in reversal of ileostomy is close to the toxic threshold. Anaesthesiologists should always be aware of the systemic toxicity risk and use weight-based doses when performing a TAP block.