Cortical and autonomic responses to noxious stimulation during anesthesia in cardiac surgery patients are moderated by preanesthetic blood pressure levels

Evidence has revealed that elevated blood pressure is associated with reduced sensitivity to noxious stimulation. The current study investigated the association between resting blood pressure and nociception during anesthesia in 32 patients undergoing cardiac surgery. Pain-related middle latency cortical somatosensory evoked potentials (MLCEPs) elicited by noxious 50 mA median nerve stimulation were used to assess intraoperative nociception and algesia. Noxious stimulation elicited MLCEPs in 18 (56%) patients. Resting blood pressure was significantly higher in patients without MLCEP than those with MLCEP. Moreover, systolic blood pressure responses to intraoperative electrical stimulation of median nerve were blunted in the group without MLCEP compared to those with MLCEP. The current findings extend the hypertensive hypoalgesia phenomenon to the operating theatre.