OPIoid sparing Anesthesia Technique for supratentorial craniotomy in geriatric patients [OPIATE]: a randomized open labelled study

Opioids have been an integral part of anesthesia practice and are not without side effects. Geriatric population have more pronounced opioid side effects during perioperative period which include, sedation, respiratory depression, shivering, nausea and vomiting, dizziness, constipation, pruritus and ileus. Specifically in geriatric patient undergoing neurosurgical procedures, increased sensitivity towards opioids, disturbed cerebral autoregulation in the postoperative period, coupled with opioid induced hypotension, respiratory depression and carbon dioxide retention leading to an undesirable rise in intracranial pressure and further sedation caused by these drugs may lead to a delayed emergence. In these patients time to emergence from anesthesia is important for rapid neurological examination. A depressed level of consciousness usually indicates residual anesthesia, most commonly due to an opioid overdose (bilaterally constricted pupils), but may be also be due to other causes, such as an intracranial hematoma, cerebral edema, nonconvulsive status epilepticus, hypoglycemia, electrolyte disturbances, hypothermia, pneumocephalus, vascular occlusion, and ischemia. Supratentorial tumors are the most common intracranial neoplasms in geriatric patients patients (>65 years). Important eloquent areas involved in speech, sensorimotor functions, white matter tracts and primary visual cortex, all are in supratentorial region. Resection of tumor that involve or are in close proximity to these areas are associated with a high risk of poor postoperative neurocognitive recovery, language dysfunction and motor weakness. While mild cognitive impairment and lethargy is not uncommon in geriatric patients in the immediate postoperative period, failure to awaken within 5- 10 minutes of cessation of anesthetic drugs should prompt a search for other potential causes of a delayed emergence. The practice of opioid sparing anesthesia [OSA] has the potential to innovate and transform the practice of neuroanesthesia and enhance the postoperative recovery profile, especially in geriatric patients. The OSA technique in the form of scalp block and combination of drugs such as dexmedetomidine, ketamine, lignocaine, magnesium etc can be used to preclude the use of opioids.  With regard to postoperative recovery, presently there are no trials that have studied the effect of OSA in terms of time to emergence from cessation of anesthesia in geriatric patients undergoing supratentorial craniotomy surgery. The hypothesis of our study is that an OSA technique would be a better alternative to the conventional anesthetic technique using opioid throughout the surgery in geriatric neurosurgical patients undergoing craniotomy for supratentorial tumor surgery.