Evaluation of optimal dose of epidural background infusion of Ropivacaine in the management of post-operative pain.

Despite well-designed concept of perioperative pain management, recent studies have revealed that a large number of patients still suffer from unacceptable pain after surgery. So, for all types of surgery, it has been seen that Continuous Epidural Analgesia (CEA) provide superior analgesia over Patient Controlled Epidural Analgesia (PCEA) for overall pain. However patients receiving CEA had significantly higher incidence of nausea-vomiting and motor block. So, presently the efficacy of Patient Controllrd Epidural Analgesia (PCEA) compared with Continuous Epidural Analgesia (CEA) is not clear. The addition of a continuous background infusion to PCEA following gastrectomy resulted in better dynamic pain scores. So,we designed a prospective, randomised study to evaluate the optimal dose of epidural proportion of epidural demand dose and background infusion in the management of post-operative pain in patients undergoing abdominal sugery.

Patients who met the inclusion criteria during the pre-anaesthetic check up will be randomly assigned into two equal groups of 40 each with the help of a computer generated table of random numbers; each group will receive intra operative epidural catheter placement followed by administration of epidural bolus of (0.1% Ropivacaine + 1mcg/ml Fentanyl combination) and the volume of the bolus shall be 0.1 ml/kg, prior to commencement of surgery; which would be followed by epidural infusion of the same combination @ 0.1ml/kg/hr. In the post - operative period all the patients will receive epidural infusion of the same combinaton @ 0.2ml/kg. The patients will be randomized into one of the following groups:

Group 1: 50% of the hourly epidural dose will be in the form of background infusion (remaining 50% as demand dose).

Group 2:  25% of the hourly epidural infusion dose will be in the form of background infusion (remaining 75% as demand dose).

The proportion of background and continuous infusion will be as per the group  allocation. Bolus dose will be 2ml and lock out time interval will be 10 min. Maximum number of boluses will depend upon the total amount of the drug to be administered as bolus depending upon group allocation.

An 18G thoracic epidural catheter would be placed at T8-9 or T9-10 intervertebral space in the operation theatre by an anaesthesiology resident not otherwise involved in the study; the epidural infusion will be started after induction of anaesthesia; standard anaesthesia technique will be used in all patients. Patient’s induction will be done by fentanyl 2-3 mg kg-1 and propofol 1.5-2.5 mg kg-1; orotracheal intubation will be facilitated by vecuronium 0.1 mg kg-1. Anaesthesia will be maintained with propofol, sevoflurane and oxygen air mixture. Hypotension was treated by infusion of isotonic sodium chloride or mephentramine 5 mg intravenously in incremental doses when systolic blood pressure was below 90 mm Hg. At the end of surgery residual neuromuscular paralysis would be antagonized with neostigmine 0.04 mg.kg-1 and glycopyrrolate 0.01 mg.kg1. Following satisfactory recovery, the patients will be extubated and shifted to the post-anaesthesia care unit.