Dexmedetomidine versus low molecular weight dextran as adjuvant to Ropivacaine in ultrasound guided erector spinae plane block for postoperative analgesia in Total Abdominal Hysterectomy

The present study will be conducted in the Department of Anaesthesiology, Himalayan Institute of Medical Sciences, Swami Ram Nagar, Dehradun over a period of 12 months after obtaining an informed written consent from the patients and ethical clearance from the institutional ethics committee. Patients undergoing Total Abdominal Hysterectomy under general anaesthesia in the Obstetrics and Gynaecology department at Himalayan Institute of Medical Sciences, Swami Ram Nagar, Dehradun will be included in the study.

Sample Size: In Uttarakhand, the proportion of women who had hysterectomy is 2.1% based on the data of NFHS-4 (16). Sample size is calculated using the formula

n = Z2(1- α /2) P(1-P)

L2

where,

n = required sample size

z= 1.96 at 0.05 level of significance

p=proportion of hysterectomy which has been taken as 0.021

L= 5% of absolute precision

n=1.96x1.96x0.021x0.98/(0.05)2

n=32 in each group

32 patients each will be included in 3 groups and hence total 96 patients will be included in the study.

All selected patients will undergo routine pre anaesthetic checkup which includes complete history, physical examination and routine laboratory investigations.

●        Patients will be divided into 3 groups (32 patients each)

1.     Group A (Control group): 40ml 0.25% Ropivacaine(20ml on each side) in Normal Saline (in 1:1 ratio)

2.     Group B: 40ml 0.25% Ropivacaine(20ml on each side)+ Dexmedetomidine 0.75μg/kg

3.     Group C: 40ml 0.25% Ropivacaine(20ml on each side)+ low-molecular weight dextran in (1:1 ratio)

Upon completion of surgery,

Erector spinae plane block will be performed under USG guidance using a high frequency linear probe/transducer in lateral position. The transducer will be placed in a parasagittal orientation 3cm lateral to T9 spinous process.

●       Patient Controlled analgesia (PCA) pump with morphine will be used as analgesic supplement so that patient can herself administer morphine when required. PCA pump will be started with concentration of 1mg/ml of morphine, demand dose of morphine through PCA pump will be 1.5 ml with lockout interval of 15 minutes, maximum limit in 4 hrs will be 20 mg. Along with it, paracetamol 1 gm i.v. will be given every 8 hourly.

●       The time duration of the first rescue analgesic request from the time patient was shifted to PACU, PCA pump press number, number of times drug is delivered and total morphine consumption in 24 h postoperatively will be recorded in all three groups. However if pain persists even after administration of morphine and PCM, diclofenac 75 mg i.v. will be used as a rescue analgesic.

QoR 40 questionnaire will be used postoperatively to measure the quality of recovery after anaesthesia on the third post-operative day .

●       Adverse effects if any will be noted, including nausea and/or vomiting and if present treated with ondansetron 0.1 mg/kg i.v.Hypotension (mean arterial pressure <20% of baseline or <60 mmHg) treated with an infusion of normal saline and if necessary an i.v. injection of ephedrine 5–10 mg incremental doses will be administrated. Bradycardia (heart rate <60 beats/min) will be treated with i.v atropine 0.01mg/kg bolus.

●       In statistical analysis the primary outcome will be the total amount of opioid consumption in first 24 hours

●       The secondary outcome variable will be:

1.     Time of first rescue analgesic request( time from PACU shifting to first requested rescue analgesic)

2.     Total amount of prescribed analgesic in PACU

3.     Any opioid related side effects like respiratory depression, pruritis within the first 24 hours.