Ketamine as part of multi-modal analgesia may reduce opioid requirements following cardiac surgery: a retrospective observational cohort study

Abstract

Background: Postoperative pain control in cardiac surgery is often managed with opioid medications. Insufficient analgesia can result in complications including splinting, pneumonia, and delay of appropriate rehabilitation. Surgeries involving the highly innervated thoracic wall, such as cardiac surgery, make pain control particularly challenging. Given the risk for addiction and the many adverse effect of opioids in the postoperative patient including sedation, respiratory depression, delirium, and decrease gastrointestinal motility, multimodal non-opioid pain regimens are the preferential treatment regimen. Recently, there is increasing evidence that low dose Ketamine, an N-methyl-D-Aspartate (NMDA) receptor antagonist, is a safe and effective for analgesia in postoperative patients. Methods: This study is a single center, retrospective, observational, cohort study involving adult patients admitted for cardiac surgery at a single center during a one year period comparing those who received a single dose of ketamine, 0.3 mg/kg over 30 minutes with those who did not. A total of 120 patient charts were reviewed, of which 96 met inclusion criteria. 32 patients had received ketamine and 64 had not. Charts were reviewed for opioid and other pain medication requirements as well as secondary outcomes including hospital length of stay, ICU length of stay, in-hospital and 30-day mortality, 30-day readmission, and rates of delirium, emergence reactions, and need for additional respiratory support. Results: The group who received ketamine required d 28.8 MME less opioid during admission (90.1 mg vs 118.9 mg, p = 0.167), and was prescribed an average of 15.8 MME less on discharge (p < 0.001). The groups differed in respect to operation type and controlling for this failed to achieve significance in needs during admission (p = 0.215), but remained significant on discharge (p = 0.02). The ketamine group also required less acetaminophen but more gabapentin. There was no difference in hospital or ICU length of stay, mortality, or readmission. 15 instances of respiratory escalation occurred, all included in the ketamine group, but all of these patients received ketamine following this decompensation, none preceding it. Conclusions: Ketamine may be a reasonable choice for postoperative cardiac surgery analgesia and may reduce the need for opioids on discharge, and possibly during admission.