Per-operative Low-Dose Ketamine For Postoperative Pain Relief In Patients Undergoing Bariatric Surgery: A Randomised Study

The surgical interventions for treating morbid obesity, i.e. bypass procedure and sleeve gastrectomy are collectively covered under the term 'bariatric surgery'. The growth of bariatric surgery has seen consonant development of anaesthesia techniques so as to ensure patient safety and facilitate post-surgery outcome. Conventionally, balanced general anaesthesia techniques routinely use opioids peri-operatively for intra-operative haemodynamic homeostasis and postoperative pain relief. However, since the morbidly obese patients have high prevalence of obstructive sleep apnea(OSA) and other co-morbidities the same technique when employed in the morbidly obese patients hampers early and intermediate postoperative recovery due to the occurrence of side effects, such as, sedation, PONV, respiratory depression, depressed GI-mobility. The above stated side effects, have lead to increased propensity for postoperative cardiac and pulmonary complications. Obese patients are more vulnerable and sensitive to the narcotics and sedatives, these drugs need to be employed judiciously in these patients. On the other hand, the reduction in opioid use may result in acute post-operative pain that may limit post-surgery rehabilitation. Therefore, we need to minimise opioid use and employ some other drugs which besides having analgesia, has a opioid-sparing effect also.

Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has analgesic properties in sub-anaesthetic doses. When used in low dose (0.2mg/kg), it is an analgesic, anti-hyperalgesic, and prevents development of opioid tolerance. On a conceptual basis, a key advantage of ketamine is that it can reduces post-operative pain and use of opioid when used per-operatively. Therefore, a regimen which avoid or minimise use of opioid is likely to decrease opioid-related postoperative morbidity in these patients undergoing bariatric surgery.In view of the above, a clinical research is highly desirable to study techniques to decrease the use of opioids in obese surgical patients.This prospective randomised two-arm study aims to assess the effect of low-dose ketamine on postoperative pain relief and opioid-sparing ability in obese patients undergoing bariatric surgery.