Survey of administration of intravenous ketamine for perioperative pain management in Australia and New Zealand.

Ketamine is an N-methyl-d-aspartate receptor antagonist approved for use in anaesthesia, with analgesic properties. Despite publication of numerous trials and expert guidelines on its use for pain management, administration of ketamine as part of multimodal perioperative analgesia remains 'off-label'. We conducted an online, prospective survey of ANZCA Fellows, exploring current prescribing practices of intravenous ketamine for perioperative analgesia. We surveyed 2000 Fellows and received 806 responses. The factors mostly likely to influence their administration of perioperative ketamine included pre-existing chronic pain, and heavy or multiple opioid use by patients preoperatively. Amongst respondents, less senior anaesthetists and those working in public hospitals were more likely to administer intraoperative ketamine. The surgical procedures most likely to result in ketamine administration intraoperatively were open pelvic/abdominal, thoracic and major spinal surgery, where ketamine administration was likely practice for the majority of respondents, with typical loading doses that ranged widely. The commonest choices of intraoperative loading dose were between 0.2 mg kg and 0.6 mg kg. The commonest choice of intraoperative and postoperative infusion rate was in the range of 0.1-0.2 mg kg h. Postoperative ketamine infusion was most commonly prescribed as third-line or rescue analgesia. The majority of respondents thought it either 'likely' or 'very likely' ketamine would reduce postoperative chronic pain after thoracic surgery, but not in other surgical categories. Our findings suggest that off-label perioperative administration of ketamine at analgesic dose ranges is routine or common practice in major surgery for a majority of specialist anaesthetists in Australia and New Zealand.