Perioperative pain management for craniotomy patients may be challenging because the commonly used agents such as opioids, gabapentin, and dexmedetomidine also cause sedation, which can confound the neurological exam and can lead to respiratory depression and increased intracranial pressure. Preoperative intravenous magnesium boluses and infusions have previously been established as an effective, nonsedating analgesic that can reduce opioid consumption 25-30% up to 48 hours postoperatively.

However, intravenous magnesium has not seen widespread use in craniotomy patients due to concerns for interference with the neurological monitoring that commonly occurs in these cases. Intravenous magnesium given as a bolus preoperatively or as a constant infusion may avoid these problems and has never been investigated.

The goal of this study is to compare intravenous magnesium given preoperatively and intraoperatively to placebo in adult elective craniotomy patients to improve quality of recovery postoperatively, and evaluate safety and tolerability. Secondary endpoints will include evaluating for pain, sedation, agitation, blood pressure, and opioid consumption postoperatively.

The study is a prospective, randomized, controlled, and double-blinded clinical trial comparing clinical outcomes of craniotomy patients who a magnesium infusion of 15mg/kg/hr to a placebo group of patients who will receive a saline bolus and infusion of equivalent volume starting at surgical closure and continuing for 15 hours. The sample size calculations are based on an effect size 24 point increase in Quality of Recovery-40 Questionnaire scores from a previous randomized control trial featuring the same bolus and infusion regimen as this trial. Investigators, patients, and providers will be blinded. Patients over the age of 18 undergoing elective craniotomy surgery will be enrolled.

The study population will consist of patients undergoing elective craniotomy surgery. The inclusion criteria consists of patient age 18-85, ASA (American Society of Anesthesiologists) Physical Status Classification 1-3, with Glasgow Coma Scale (GCS) of 15 with adequate english comprehension. Exclusion criteria includes pregnant or nursing patients, patients with known allergies to any of the study drugs, patient's refusal, patients with a history of cirrhosis, chronic kidney disease stage 3 or higher, known history of substance abuse, neuromuscular disease or heart block.

Inclusion Criteria:

• patient age 18-85
• ASA (American Society of Anesthesiologists) Physical Status Classification 1-3
• Glasgow Coma Scale (GCS) of 15
• Adequate english comprehension

Exclusion Criteria:

• pregnant or nursing patients
• patients with known allergies to any of the study drugs
• patient's refusal
• patients with a history of cirrhosis
• chronic kidney disease stage 3 or higher
• known history of substance abuse
• history of neuromuscular disease
• history of heart block