Refractory Response to Regional Anaesthesia: A Case of Failed Spinal and Peripheral Nerve Blocks with Negative Genetic Evaluation

Failure of regional anaesthesia is often associated with technical or pharmacological errors. Only a few cases of resistance to local anaesthetics have been published in the literature, and there is no consensus on the best approach in the event of clinical suspicion. We report a case of failed regional anaesthesia in which high suspicion of resistance to local anaesthetics drugs prompted us to perform a detailed etiological investigation. We present a case of 57-year-old female who presented with difficulty in breathing, high grade fever, leg pain and swelling for two days. Patient was diagnosed with right lower leg cellulitis. Patient underwent minor dental procedure under local anaesthesia and previous caesarean section under spinal anaesthesia in past. Regional anaesthesia failed on both occasions and was converted to general anaesthesia. The patient was administered spinal anaesthesia with hyperbaric bupivacaine to undergo wound debridement but failed completely. Patient was administered combined femoral sciatic nerve block using 0.375% Ropivacaine which also failed completely. Since the patient had multiple failed regional anaesthesia attempts, we considered diagnosis of local anaesthesia resistance and proceeded with general anaesthesia. Clinical exome sequencing was conducted to identify a possible genetic basis to resistance to local anaesthetic, but no pathogenic variants were detected. This case highlights the complexity of anaesthetic resistance, the limitations of current genomic testing in explaining such phenomena, and the need for further exploration into alternative aetiology