Dexmedetomidine versus Dexamethasone as an adjuvant to Ropivacaine in USG- guided Rectus Sheath Block for post-op analgesia in patients undergoing exploratory laparotomy.

This study will be performed on adult patients, between the age group of 18-60 years) who will undergo exploratory laparotomy after obtaining the approval from the local ethical committee and scientific institutional review board. Patients will be assessed based on a multitude of factors : history ,physical examination , available investigations and as per the inclusion and exclusion criteria, they will be randomly allocated to receive either a mixture of Ropivacaine and dexamethasone (group A) or a mixture of Ropivacaine and dexmedetomidine (group B) or just Ropivacaine. (Group C).Informed written consent will be signed by each patient.

All eligible patients will be kept fasting for 6 hours for solid food and 2 hours for clear fluids prior to surgery. All the patients will be given tablet alprazolam 0.25 mg and tablet ranitidine 150 mg night before and 2 hours prior to surgery, respectively.

During this visit, all the patients will be explained the procedure and will also be taught to interpret the Visual Analogue Scale and how to use  PCA pump.

In the operating room (OR), intravenous cannulation will be established and after attaching ASA standard monitors such as Electrocardiograph (ECG), non-invasive blood pressure  and Pulse Oximetry  (SPO2) all baseline parameters like ECG, Systolic Blood Pressure, Diastolic Blood Pressure, Mean Blood Pressure , Heart Rate, SpO2  will be recorded. before enrollment and randomization into the study.

In the OT, all patients will be given Inj Midazolam 1mg i.v. After preoxygenating  the patient with 100% Oxygen for three minutes , induction will be carried out with Inj Fentanyl 2mg/kg , Inj Propofol 2mg/kg and Inj. Atracurium 0.5mg/kg which will be followed by tracheal intubation after a complete muscle relaxation. Patient will be put on IPPV after conforming the intratracheal position of the endotracheal tube.

Anaesthesia will be maintained with Sevoflurane in 50% Oxygen in Air. Target MAC will be between 0.8-1.2. Inj Paracetamol 1g IV will be administered. IV fluids will be given as per Holiday-Segar formula.

At the end of the procedure, after skin closure, all patients will be given bilateral Rectus Sheath Block under ultrasound guidance and then, will be injected with the study drugs as per the group allocated.

For patients randomized to Group A,(dexamethasone group) 8 mg will be administered on both sides. Dexamethasone sodium phosphate is supplied in 4mg/ml ampule. For patients randomized to Group B(dexmedetomidine) 1mcg/kg body weight will be administered.

Neuromuscular blockade will be antagonized with Inj. Glycopyrrolate 0.01mg/kg and Inj. Neostigmine  0.05mg/kg which will be followed by extubation in standard manner.

Rectus sheath block will be performed under ultrasound guidance using a high frequency linear ultrasound probe. A 23 gauge spinal needle will be inserted in medial to lateral orientation, through the subcutaneous tissue, to pierce through the anterior rectus sheath after identification of the sheath and lateral edge of the rectus muscle. The needle will be advanced further through  the body of the muscle until the tip rest on the posterior rectus sheath. After negative aspiration, 10 ml of local anesthetic will be injected along with the study drug. Same procedure will be repeated on the other side.

Patients will, then, be transferred to the post-anesthesia care unit and observed postoperatively. Parameters like heart rate, blood pressure( Systolic, Diastolic, Mean), and oxygen saturation will be monitored. The intensity of pain will be assessed using VAS score system at 0mins, 10mins, 20 mins and 30mins, and then, at 4th hour, 8th hour, 12th hour, 16th hour, 20th hour and 24th hours by the anesthesiologist (independent observer).

VAS score is a 10-point horizontal pain scale with 0 representing “no pain” and 10 representing “worst pain imaginable”.

In PACU, patient will be attached to intravenous PCA pump loaded with Tramadol . Bolus of 20 mg with  lock out time of 10 mins will be 10 set.

Further, Sedation score (Ramsay Sedation Score), side effects like–

 nausea, vomiting, and pruritus (categorical scale) will also be noted.

At the end of 24h, patients will be asked to rate their analgesic satisfaction using VAS.

In statistical analysis, the primary outcome will be measured as the time of first rescue analgesic used which will be the time duration of analgesia produced by the block.

The secondary outcome variable will be

1.    Total opioid consumption over 24 hours.

2.    Rates of side effect (nausea, vomiting, pruritis) if any within the first  24 hours.

3.    Patient satisfaction utilizing a Likert scale questionnaire on a post-operative day –

4.    Adverse drug reaction caused by drugs used if any.