Accelerated Recovery Following Opioid-free Anaesthesia in Supratentorial Craniotomy

Anaesthesia for craniotomy surgery focuses on maintaining cerebral perfusion, avoiding factors that may lead to increased intracranial pressure and aim for early postoperative neurological recovery. In recent decades, opioids have always been a mainstay for perioperative pain management and play an important role as the standard of care - opioid-based anaesthesia (OBA). However, opioid use poses a significant number of adverse effects such as respiratory depression, prolonged sedation, postoperative nausea and vomiting (PONV), pruritus, ileus, urinary retention, and hyperalgesia. This should be avoided in patients who undergo craniotomy as they can lead to an inaccurate neurological examination because of excessive sedation and have the potential to mask early signs of intracranial complications. Besides, opioid-induced respiratory depressions cause hypercapnia which increases cerebral blood flow and may lead to cerebral oedema. Opioid-induced PONV leads to a spike in intracranial pressure which can be detrimental for post-craniotomy patients. Despite this, adequate pain management is vital as suboptimal pain control drives sympathetic efflux, promoting hypertension that may increase morbidity and mortality through intracranial haemorrhage. In view of this, recent studies on anaesthesia for craniotomy has noted a paradigm shift towards opioid-sparing or opioid-free anaesthesia (OFA) to prevent opioid-related adverse effects which might prolong patients' recovery post-craniotomy. Multi-modal analgesia is also incorporated in many practices nowadays to achieve optimal intraoperative and post-craniotomy pain control. In order to guide anaesthesiologists' dosing of hypnotics and analgesics to provide appropriate depth of anaesthesia and adequate pain control, as well as to prevent under or overdosing, CONOX monitor might be used intraoperatively to measure hypnotic effect (qCon) and probability of response to noxious stimulus (qNox).

This prospective randomised controlled trial clinical study will take place in neurosurgical operation theatres and neurosurgical intensive care unit (ICU) of University of Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia to compare intraoperative and postoperative outcomes of patients who undergo elective supratentorial craniotomy with opioid-free anaesthesia (OFA) and those with opioid-based anaesthesia (OBA).

Inclusion criteria

• Adult patients who have supratentorial lesions going for elective craniotomies (age group- 18-65 years old)
• Patients with Glasgow Coma Scale of 15 (E4V5M6)
• Patients who are fit to give consent
• Power of elbow flexion of patient's dominant hand score 5 with Medical Research Council (MRC) Muscle scale
• American Society of Anaesthesiologists (ASA) Physical Status Classification I - III patients

Exclusion criteria

• Patients who refused or not fit to consent for participation
• Patients with Glasgow Coma Scale less than 15
• Patients who have known allergy to the drugs used in this study
• Patients on chronic opioid use (Chronic opioid use is defined as having any number of opioid prescriptions or dosing for at least 90 days continuously)
• Patients going for emergency craniotomies for supratentorial lesions
• Patients who are not fit for extubation postoperatively
• Patients with chronic kidney disease Stage 3A and above (eGFR less than 60 ml/min/1.73m2)
• Patients with known case of liver cirrhosis