Dexmedetomidine as an Adjuvant to Bupivacaine in Scalp Block vs Bupivacaine Alone for Hemodynamics Stability in Craniotomy

1. Preoperative settings:

Complete history taking and full physical examination. Routine preoperative investigations was done to all patients including laboratory investigations (complete blood picture, liver function tests, prothrombin time and partial thromboplastin time) and other as needed by the patient condition.

Written informed consent was obtained from all participants prior to the study. Patients was educated visual analogue score for pain (VAS), which consisted of 10c.m line, with two end points (where 0=no pain and 10=worst pain).

1. Intraoperative settings:

Electrocardiogram (ECG), non-invasive blood pressure (NIBP), pulse oximeter (SpO2) will be applied, and baseline readings were taken before induction, no sedation was given.

Anesthesia was induced after a period of preoxygenation with 100% oxygen for 2-3 minutes with intravenous injection of fentanyl 2 µg/kg .propofol 2 mg/kg ) and a muscle relaxant (Atracurium) 0.5 mg/kg after loss of patient consciousness.

After endotracheal intubation, intubation was confirmed by ETCO2 and bilateral auscultation of the chest.

Anesthesia was maintained with 60% oxygen mixed with air and isoflurane 1-2%. Lungs were ventilated using volume-controlled ventilation with tidal volumes and respiratory rate adjusted to maintain end tidal CO2 at 35-40 mmHg.

Following anesthesia induction, a continuous invasive blood pressure monitoring was initiated through radial 20-gauge arterial catheterization, as well as urine output through bladder catheterization.

Sampling method:

The patients were randomly divided into two equal groups using a computerized generated list (closed opaque sealed envelope).

Group SB (n =18 patient) received scalp block with Bupivacaine alone. Group SD (n =18 patient) received scalp block with Dexmedetomidine as an adjuvant to Bupivacaine.

In both group:

Scalp nerve block was done by anesthesiologist who is blind to the drug being injected and under complete septic condition where local infiltration of local anesthetic (LA) was done guided by bony superficial landmarks to block the supraorbital, supratrochlear, auriculotemporal, occipital, and post auricular branches of the greater auricular nerves as follow :

The patient lied supine on the table while the performing operator usually stands at the head end facing the feet.

The supraorbital and supratrochlear nerves were blocked with 2 mL of solution as they emerge from the orbit with needle introduced above the eyebrow perpendicular to the skin. The supraorbital notch was located by palpation, and the needle was introduced perpendicularly 1 cm medial to the notch.

The auriculotemporal nerves was performed with the patient's head turned to one side so that the side to be blocked faces upward with 3 mL of solution injected 1.5 cm anterior to the ear at the level of the tragus; the needle was introduced perpendicular to the skin and infiltration made deep to the fascia and superficially as the needle withdrawn. The superficial temporal artery should be palpated to avoid intra-arterial injection. Negative aspiration is a must for this block.

The post auricular branches of the greater auricular nerves were blocked with 2 mL of solution between skin and bone, 1.5 cm posterior to the ear at the level of the tragus The needle was inserted at 90 degrees till bony contact is made, upon which it is withdrawn, and subcutaneous injection was performed.

The greater, lesser, and third occipital nerves were blocked with 3 mL of solution with infiltration along the superior nuchal line, approximately halfway between the occipital protuberance and the mastoid process.

In Group SB: (LA) was done by 20ml of Bupivacaine 0.25%.

While Group SD:

local infiltration of total volume 20ml which include (Bupivacaine 0.25%. + Dexmedetomidine 1mcg/kg) was done.

In both group maximal dose of Bupivacaine didn't not exceed (2.5 mg/kg) . Dexmedetomidine preparation was done by 2ml (200 mcg) diluted by 18 ml normal saline in 20 ml syringe as 1ml was contain 10 mcg and used.

Mayfield placement in all patients was done 15 minutes after scalp block was given.

*Both blocks was done \& or supervised by an expert all through. At the end of the surgery, the residual neuromuscular block was be reversed with intravenous injection of neostigmine (0.05 mg/kg) with atropine (0.01 mg/kg), Endotracheal tube extubation was done and then the patient was transferred to Postoperative anesthesia care unit (PACU).