The investigators hypothesize that magnesium sulphate owing to its analgesic and sedative properties is not inferior to fentanyl in providing conscious sedation as adjuvants to propofol and local injection of lidocaine in patients undergoing surgery for evacuation of subdural haematoma. Consequently, the investigators are testing this hypothesis by comparing the sedative and analgesic effects of magnesium sulphate versus fentanyl as adjuvants to propofol lidocaine admixture for conscious sedation in patients undergoing burr hole surgery for evacuation of subdural haematoma.

Following institutional ethical committee approval, 34 patients undergoing burr-hole surgery for chronic subdural hemorrhage were included in this prospective, randomized, double-blind study.

Written informed consent were obtained from all subjects before enrollment in the study.

During the preanesthetic checkup,the operative procedure and anesthetic techniques were explained to all patients.

Upon arrival to operating theater, standard monitoring were applied to all patients and bispectral index was applied before starting the drug infusions and was used for maintenance of sedation during operation.

Subjects were randomized into 2 groups. Magnesium (M) group received Magnesium sulphate 50mg/kg IV over 15 minutes Followed by continuous infusion at 15 mg/kg/h Fentanyl (F) group received fentanyl 1 μg /kg IV bolus over 15 minutes Followed by continuous infusion starting at 0.5 μg /kg/h Loading and infusion doses of magnesium sulphate and loading doses of fentanyl were chosen from previous studies.

In both groups fentanyl and magnesium sulphate were accompanied by IV propofol at a dose of 50- 150 μg /kg/min bolus over 10 minutes to achieve target sedation level, that is, Ramsay sedation scale (RSS) 3, if RSS afterwards does not reach 3, a supplementary bolus dose of 0.2 mg/kg propofol were given to the patients, followed by ( 20-40 μg /kg/ min) to maintain Intraoperative level of sedation by bispectral index (BIS ) reading by 60-80 After achieving predefined target sedation level (RSS of 3), surgeons infiltrated the sites of the burrholes with 20 mL of a local anesthetic solution containing 10 mL of 0.5% bupivacaine and 10 mL of 2% lidocaine with adrenaline infiltrated locally at least 5 minutes before surgical incision. After burr-hole craniotomy followed by the hematoma evacuation is accomplished, the Infusion of sedatives were discontinued just after placement of the final skin suture.

Intraoperative patient's movement is defined as those likely to interfere with surgical procedure such as bending of hand and/or leg and movement of head were recorded. The first intervention is to attempt patient reassurance for 30 seconds. If movement continues then the bolus dose of propofol of 0.5 mg/kg was given and infusion dose was increased in the previously described manner till the maximum dose to regain BIS sedation score between 60-80.

If the patient starts to move again the same sequence was repeated. Induction of general anesthesia was deemed the final intervention in case satisfactory condition was not achieved within the rescue propofol.

All patients were transferred to the post-anesthesia care unit (PACU) after surgery.

The data collected are:

1. Total amount of Propofol consumption.
2. Total number of patient movements
3. The intraoperative and postoperative hemodynamic data
4. VAS (Visual analogue scale for pain) score
5. Time to first rescue analgesic
6. Adverse events
7. Surgeon satisfaction score was recorded.

Statistical analysis:

Data was analyzed using SPSS © Statistics version 23 (IBM© Corp., Armonk, NY, USA). Chi-square test (Fisher's exact test) was used to examine the relation between qualitative variables. For quantitative data, comparison between the two groups was done using independent sample t-test or Mann-Whitney test as appropriate. All tests were two-tailed. A p-value < 0.05 was considered significant.

Sample Size calculation:

A previous study reported that pre-procedure magnesium sulphate reduced the total propofol requirements to 130±19.09 mg compared to 172.8±29.09 mg with pre-procedure fentanyl. Based on these results, a sample size of 15 cases in each group was satisfactory to elicit the difference at an alpha level of 0.05 and a power of the test of 95%. The sample size was increased to 17 per group to compensate for possible dropouts.

Inclusion Criteria:

• age > 50 years
• ASA (American Society of Anesthesiologists physical status) grade I to II
• Glasgow coma scale 14-15
• Unilateral chronic subdural hematoma

Exclusion Criteria:

• Hypertension (diastolic blood pressure > 160 mmHg)
• Bradycardia (<50 bpm)
• Ischemic heart disease (<6 months)
• Second- or third-degree heart block
• Long-term abuse of or addiction to alcohol, tobacco, opioids, and sedative-hypnotic drugs (>6 months)
• Allergy to study drugs
• Neuropsychiatric diseases
• Predicted difficult airway according to Ganzouri score >4.
• Patients with deviation in the surgical technique or with inadequacy of local anesthesia were excluded from the study.