After obtaining permission from the institutional ethical committee and informed consent from the patient, patients will be included in this prospective randomized double blind comparative study.

Pre anesthetic examination and preparation: Patients will undergo routine pre anesthetic examination before considering surgery. We will enroll patients who fulfill inclusion criteria for the study. We will obtain a written informed consent from the patient. Patients will be kept nil-per-oral for 8 hours and pre-medicated with oral pantoprazole 40 mg on the previous night of surgery.

On the day of surgery, we will re-assess the patients in the preoperative room. Secure intravenous access with a wide bore 18G cannula and record the baseline vital data like Pulse rate (PR), Blood pressure (BP) and SpO2.

METHODOLOGY

After shifting to the operation theater (OT), IV drip set is connected, all American society of Anaesthesiologists (ASA) monitors will be attached and initial readings are noted. Patient will receive IV Ringer’s lactate solution, according to the weight.

A syringe of 50 cc will be prepared with either normal saline or dexmedetomidine diluted with 2 μg/ml. Patients allocated to group D received through the intravenous infusion pump, a dose of 0.5 μg/kg/hr till the end of surgery. Group S received the same calculated volume of normal saline.

Five minutes before administering SAB Dexmedetomidine infusion will be started. In the lateral position and under aseptic precautions, local skin infiltration using 2 ml of 2% lignocaine at L2-L3 or L3 -L4 space, in the midline. Using 25 G Quinke’s spinal needle SAB will be done and 15mg (3ml) of 0.5% hyperbaric Levobupivacaine will be injected & the patient will be brought to the supine position.

In case of failure with the two above-mentioned attempts; the procedure will be abandoned, general anesthesia administered and those patients will be excluded from the study.

Another investigator, who will not know which infusion drug is administered to the respective groups will assess the sensory level at the midline for each patient by a pin prick test using a blunt 23-gauge needle.

The times required to reach loss of sensation at T10-T12 dermatome (onset time) and the maximum dermatome level, at which sensation is lost, will be recorded.

    

 The sensory blockade is assessed every minute until the T10-T12

     dermatome level is achieved, then 5,10,15,20 and 30 minutes after intrathecal injection of Bupivacaine, then every 15 minutes thereafter.

The duration of sensory blockade will be assessed by time for two- dermatome sensory regression (TDR) and recovery of L2 dermatome sensation (duration of spinal anesthesia, DSA). The duration of motor blockade (DMB) will be assessed at 15 min intervals after the immediate end of surgery, by determining the time required to recover knee flexion 10 cm above the surface of the bed.(Bromage 3)

Vital signs will be measured every 2.5 minutes for the first 10 minutes after Dexmedetomidine infusion of the study drug and then every 5 minutes during surgery.

The level of sedation is evaluated intra- operatively and post-operatively every 15 min using Ramsey Level of Sedation Scale (RSS):

1. Patient anxious, agitated, or restless.

2. Patient cooperative, oriented, and tranquil alert.

3. Patient responds to commands.

4. Asleep, but with brisk response to light glabellar tap or loud auditory stimulus.

5. Asleep, sluggish response to light glabellar tap or loud auditory stimulus. 6. Asleep, no response.

All sedation scores were recorded considering the time of start infusion as time zero.

Hypotension will be defined as mean arterial pressure MAP<60 mm hg or less than 80% of baseline, and is treated with incremental doses of intravenous ephedrine 5-10mg. Heart rate < 50 beats/min will be as treatment needed Bradycardia and treated with 0.6 mg intravenous atropine.

Hypotension, treatment-needed bradycardia, oxygen desaturation and excessive sedation (Ramsey scale < 3) will be recorded.