Comparative study of Analgesic Efficacy of Fentantyl and Dexmedetomidine as adjuvant to Intrathecal Hyperbaric Ropivicaine 0.75% for Lower Abdominal Surgeries - A Prospective Double Blinded Randomised Controlled Study

Spinal anaesthesia is the most commonly performed anaesthetic technique for lower abdominal and lower limb surgery. . Many adjuncts like fentanyl, alpha 2 agonists , neostigmine, magnesium sulphate, vasoconstrictors and midazolam have been used successfully to prolong the duration of spinal anaesthesia.

Ropivicaine, an amide local anaesthetic, with similar properties like bupivacaine, with less cardiovascular toxicity. Intrathecal isobaric ropivicaine alone produces a sensory block with variable duration of analgesia. By making ropivacaine hyperbaric and addition of adjuvants have been tried to improve the quality of intraoperative anaesthesia and postoperative analgesia.

Dexmedetomidine, a highly selective alpha 2 adrenergic agonist with antinociceptive action for both somatic and visceral pain, has been used as adjuvants to Intrathecal local anaesthetics.

Fentanyl, is a potent lipophilic synthetic opiod with a rapid onset of action and lesser incidence of respiratory depression. It has been shown to prolong the duration of analgesia in the early postoperative period.

There are limited studies on intrathecal hyperbaric ropivacaine in combination with Fentanyl or Dexmedetomidine for postoperative analgesia following lower abdominal surgeries.

This study is undertaken to compare the safety, quality and efficacy of intrathecal of Dexmedetomidine 10 mcg with hyperbaric 0.75% Ropivacaine 3ml, with that of Intrathecal Fentanyl 25 mcg with hyperbaric 0.75% Ropivacaine 3ml.

After obtaining the Institutions Ethical committee approval a comparative study  and a written  informed consent will be taken.

Visual analogue scale for pain assessment will be explained to the patients. It’s a scale in which “0” indicates no pain and “10” indicates severe pain.

Randomization will be done by computer generated data.

All patients will receive Alprazolam tablet at a dose of 0.5 milligrams, and Pantaprazole tablet at a dose of 40 milligrams in the night before surgery. Patients will be kept nil oral for a period of 8 hours preoperatively.

On reaching the operation theatre, and confirming the fasting status, an 18 gauge cannula will be secured to the non-dominant hand. Routine monitors will be connected.  Patient will be preloaded with Lactated Ringers solution at the rate of 10ml/kg.

Under proper aseptic conditions, spinal anaesthesia will be performed at the level of L3-L4 or L4-L5 interspace in sitting position using a midline approach by a 25G Quincke spinal needle.

Group D: patients will receive intrathecal ropivacaine 0.75% heavy 3ml with dexmedetomidine 10mcg. Total volume made 3.5ml by addition of sterile normal saline.

Group F: patients will receive intrathecal ropivacaine 0.75% heavy 3ml with fentanyl 25mcg. Total volume 3.5ml.

The study drug will be injected slowly over 10-15 seconds with the bevel of the needle pointing upwards and the patients will be made supine immediately. Anaesthesiologist involved in preparation and administration of drug will not be involved in assessment. Assessment will be done by another anaesthesiologist who will be blinded to the group allocation.

After completion of intrathecal administration, sensory levels are assessed by loss of sensation to pin prick using 23G hypodermic needle on each dermatome for every one minute. Onset of analgesia is defined as the time taken for the block to reach T10 dermatomal level and noted. After that analgesia will be checked every 2 mins till the highest level stabilizes for 4 consecutive tests. Onset of motor blockade is defined as the time taken for the block to attain modified bromage scale grade

1. Time taken for the block to achieve modified bromage grade 3 will also be noted.

Patients will be monitored   for heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), oxygen saturation, Ramsay sedation scale, at intermittent intervals of 2 minutes for the first 6 minutes, 5 minutes for the next 15 minutes, 30 minutes for the next 90 minutes and half hourly henceforth .  Any adverse events like Hypotension , Bradycardia, nausea, vomiting, respiratory depression, shivering, pruritis also will be noted.

Patient will also be assessed for regression of the block by 2 dermatomal segments, and time will noted.

After the surgery, patient will be shifted to post anaesthesia care unit, where they remain till complete recovery of sensory and motor blockade. Pain will be assessed according to VAS at 2nd,4th,6th,8th,12th,24th hrs postoperatively. Time of request for rescue analgesia in the postoperative period will be noted. Duration of analgesia is defined as the time from completion of injection of study drug to the time of first request of rescue analgesia. Patients with VAS score more than 5 will receive inj Tramadol 1mg/kg body weight. If pain persists after 10 minutes of tramadol, patients will receive inj Dicolfenac 1 mg/kg body weight. Total analgesic consumption in 24 hrs will be noted. Motor recovery will also be assessed half hourly until modified bromage grade 0 is achieved. . Time to void urine will also be noted.