Opioid Free VS Opioid Anesthesia for Craniotomies

Anesthesia for craniotomies can be very challenging because of the presence of periods of noxious stimuli that interposes with periods of little stimulation which makes hemodynamic control a little bit more complicated. Intraoperative episodes of hypertension during periods of intense stimulations and early postoperative hypertension may lead to serious complications as post craniotomy intracranial hemorrhage and vasogenic brain edema. Anesthetic techniques based on usage of high doses of potent opioid analgesics such as fentanyl and remifentanil have been widely popular among anesthesiologists. However, the intra operative use of large bolus doses or continuous infusions of potent opioids may be associated with postoperative hyperalgesia and increased analgesic consumption.

More recently, concerns have arisen about impaired healing,immunosuppression,and worsening of oncologic outcomes with systemic opioids. Another technique that started gaining its popularity is opioid free anesthesia (OFA) technique whose corner stone is depending on multiple anesthetic adjuvants that have analgesic effects, , therefore when given together in small doses they result in good anesthesia with less side effects and faster recovery compared with opioids. This technique has been successfully used in anesthesia for bariatric surgeries combining multiple drugs as dexmedetomidine, lidocaine, ketamine, ketorolac and magnesium.

Dexmedetomidine is a highly selective α2-adrenoceptor agonist with sedative, anxiolytic and analgesic properties that has minimal effects on respiratory drive. Although preoperative intravenous dexmedetomidine administration is associated with a reduction in postoperative pain intensity, analgesic consumption and nausea, the analgesic property of dexmedetomidine is less effective compared with opioids. Intravenous lidocaine has been described as having analgesic, anti-hyperalgesic, and anti-inflammatory properties. Intravenous lidocaine infusion in the perioperative period is safe and has clear advantages, such as decreased intra operative anesthetic requirements, lower pain scores, reduced postoperative analgesic requirements, as well as faster recovery. In addition to ketamine magnesium is also reported to enhance analgesia by blocking NMDA receptor, also magnesium has the properties of a sympatholytic and has been introduced as a safe component of balanced anesthesia.

This comparative study between Opioid free anesthesia (OFA) and Opioid anesthesia (OA) aims to compare the effect of both techniques on intra operative hemodynamics, intracranial tension and recovery in cranial surgeries for supratentorial tumors.

After obtaining an informed written consent from the patients or their responsible relative, patients will be divided into 2 groups randomly using computer software (research randomizer.org); Opioid free Anesthesia group (OFA) and Opioid Anesthesia group (OA). To assure blindness, numbers will be concealed by closed envelope, analgesic infusions will prepared by a clinical pharmacist not included in data collection and the attending anesthetist will be blinded to the type of analgesic solution injected.

Over 10 minutes prior to induction of analgesia patients in the OFA group will receive small doses of demedetomidine, ketamine, lidocaine and magnesium along with ketorlac and acetaminophen. an infusion afterwards will be administered through the operation containing dexmedetomidine, ketamine and lidocaine. In the OA group, over 10 minutes, patients will receive a loading dose of fentanyl followed by fentanyl infusion through the operation. General anesthesia will be induced using the same drugs and the same parameters in both groups after the completion of the initial analgesic infusions The primary outcome parameter will be the percentage of patients experiencing hemodynamic instability at Burr Hole (defined as recording an increase or decrease of the mean arterial blood pressure by 25 % of the baseline reading) Assuming the rate of hemodynamic instability (defined as increase or decrease of the mean blood pressure by 25 % of the baseline reading) would be 40 % in the control arm, a clinically meaningful reduction of the rate of hemodynamic instability to 10 % in the investigational arm with a statistical power of 80 % and an alpha error of less than 0.05 would require recruiting 29 patients in each group (a total of 58 patients).

Continuous data will be presented as mean + (SD). Categorical variables will be represented as frequencies and percentages. According to the type of data Comparison between the two groups will be performed using either Chi square test or Fisher's exact test. Hemodynamic variables will be compared to baseline using repeated measures analysis of variance (ANOVA) with post hoc scheffe's test for positive data. P values less than 0.05 will be considered statistically significant.