Effects of Intrathecal Dexmedetomidine as an Adjuvant to Low Dose Hyperbaric 0.5% Bupivacaine

After approval of the synopsis and permission from the hospital ethics committee, all patients meeting the inclusion criteria will be included in the study. Patients will be instructed not to consume solid food after midnight before surgery and to take clear liquids up to 2 hours before surgery. Using a computer-generated random number table, patients will be enrolled in one of the two groups: Group I will receive 1.5 ml of 0.5% hyperbaric bupivacaine (7.5 mg). Group II will receive 1.2 mL of 0.5% hyperbaric bupivacaine (6 mg) along with 0.3 mL (5 μg )of dexmedetomidine (total of 1.5 mL). They will be randomly allocated into two groups using the sealed envelope technique by a person blinded to the procedure. The study medication will be prepared by an anaesthesiologist not involved in the study and another anaesthesiologist performing the spinal block will record the intraoperative and postoperative data. On arrival at the Operating Room (OR) monitors like a non-invasive blood pressure monitor (NIBP), peripheral oxygen saturation monitor (SpO2), and electrocardiography monitor (ECG) having lead II will be attached. All the baseline values of blood pressure (SBP, DBP, and MAP), heart rate and rhythm, and SPO2 will be observed and recorded. An intravenous (IV) line will be established with an 18-gauge cannula. The study drug solutions will look identical. For Group I, 7.5 mg(1.5 mL) of 0.5% hyperbaric bupivacaine hydrochloride will be drawn in a 3 mL BD syringe. For Group II, 6mg (1.3 mL) of 0.5% hyperbaric bupivacaine hydrochloride will be drawn in a 3 mL BD syringe. By using an insulin syringe, 0.3 mL (3 μg) of Dexmedetomidine (preservative free) 100 μg/mL will be added to the 6 mg (1.3 mL) of hyperbaric bupivacaine under complete aseptic conditions to bring the total volume to 1.5 mL. The total volume of drug solutions will be 1.5 mL in each group.

Local infiltration of the skin with 2mL of 2% lidocaine will be done to decrease the discomfort caused by the spinal needle. A spinal puncture will be performed at L3-L4 or L4-L5 with a midline approach using a 25-gauge Quincke needle in the sitting position. After verification of clear and free flow of cerebrospinal fluid, the drug will be administered and the patients will be placed in the supine position Vitals will be monitored Heart Rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), respiratory rate (RR), oxygen saturation (SpO2) for every 5 minutes till the end of surgery. If mean arterial pressure (MAP) decreases below 65 mmHg or the Heart rate falls below 65 beats per minute then intravenous vasopressors will be given. The sensory block levels will be checked on the bilateral mid-clavicular line with a pin prick with a blunt needle every 2 min from the time of drug injection until the sensory level achieves up to T10 level.

In contrast, the motor block will be assessed using the modified Bromage scale. The surgeon will be asked to start the surgery when the sensory block has reached the T10 level. After completion of the surgery, the patient will be shifted to the PACU and monitored for 3 hours with continuous ECG monitoring and intermittent non-invasive blood pressure monitoring at 5-minute intervals. All untoward events like shivering, nausea vomiting, sedation, and respiratory depression will be monitored and recorded in the operating room as well as in the recovery room.

All data will be recorded on Performa attached as Annex A after the consultant anesthetist confirms.

Inclusion criteria

• ASA I to ASA II
• Age 50 to 80 years old
• Height between 155cm and 175 cm

Exclusion criteria

• History of spine surgery or the presence of an infectious focus on the back
• Patient's refusal to undergo a spinal anaesthesia
• Hypersensitivity to bupivacaine or dexmedetomidine
• Patients taking drugs of abuse or narcotic analgesics
• Diabetic neuropathy
• History of bleeding disorders
• Oral/intravenous anticoagulant therapy
• History of arrhythmias or labile hypertension
• Unco-operative patients
• Hearing defect
• ASA III and IV
• Central or peripheral nervous system disorders
• Severe hypovolemia