Comparative evaluation of different doses of intrathecal morphine in reducing the requirement of postoperative epidural analgesia in patients undergoing major abdominal surgery: A randomized controlled trial

Written informed consent will be obtained from all patients before considering them for this study. All patients meeting the inclusion criteria who give the consent will be included in the study.

After establishing intravenous (IV) access and standard hemodynamic monitoring (i.e., ECG, non-invasive blood pressure, and Spo2) will be applied to all patients.

Patients would be randomized into 3 groups (based on the regional analgesic technique used before the start of surgery) for the study based on computer generated randomization sequence:

Group A: Receiving only epidural analgesia with 10 mL of 0.20% Ropivacaine.

Group B: Receiving Intrathecal analgesia with 5 mcg/kg up to a maximum dose of 500 mcg of Morphine + Epidural analgesia with 10mL of 0.20% Ropivacaine.

Group C: Receiving Intrathecal analgesia with 10 mcg/kg up to a maximum dose of 1mg of Morphine + Epidural analgesia with 10mL of 0.20% Ropivacaine.

Under all aseptic precautions intrathecal and epidural analgesia will be administered to all patients depending upon their group allocation, in the sitting position using a 25- or 27-gauge Quincke needle and 18 G Tuohy needle and epidural catheter at the T8-T9 or T9-T10 interspace.

Anaesthesia will be induced with injection fentanyl (2 mcg / kg), propofol (1.5 -2 mg/ kg), followed by vecuronium (0.1 mg/ kg) to facilitate endotracheal intubation. End tidal CO2, temperature, BIS and urine output monitoring will be done intraoperatively. Further monitoring i.e., invasive arterial blood pressure and central venous pressure, will be based on the discretion of anaesthesiologist managing the patient. Blood pressure (BP) and Heart rate (HR) are to be measured every minute for 5 minutes after propofol administration.

After preintubation measurements for 5 minutes, the trachea will be intubated with appropriate endotracheal tube size. The infusion rate of crystalloid to be fixed at approximately 10ml/hour per actual body weight during the study period. Maintenance of anaesthesia will be done with O2: Air in ratio of 40:60, intermittent vecuronium, fentanyl and sevoflurane (MAC 0.8-1).

Ventilation will be controlled to maintain ETCO2 between 31-40 mmHg.

The dose and frequency of administration of epidural analgesia would be recorded intraoperatively.

Patients would be monitored intra-operatively for any hemodynamic instability. Systolic blood pressure less than or equal to 80 mmHg or greater than 30% decrease from baseline before intubation will be defined as significant hypotension. Mephentermine (6mg) will be given if systolic blood pressure (SBP) falls to 80mmHg or less.

At the end of surgery, the muscle relaxation will be reversed with injection neostigmine (0.04- 0 08 mg/kg) and glycopyrrolate (0.005-0 01 mg/kg) and patient extubated.

Postoperatively, all the patients will be monitored for 24 hours post operatively either in ICU or surgical HDU. (to monitor for any side effects of intrathecal morphine)

In the post-operative period, the patients will be provided analgesia by patient-controlled analgesia (PCA) pump:

1). Continuous epidural infusion of 0.25% ropivacaine + 4.0 mcg/ml Fentanyl @ 2mL/hour.

2). Bolus dose of 2mL of Fentanyl 4.0 mcg/ml + 0.25 % Ropivacaine with a lock out interval of 30 minutes.

The post-operative vitals i.e., heart rate, blood pressure, spo2 and pain score (based on NRS scale) will be recorded in all patients immediately after the surgery, every 30 minutes till first 2 hours, one hourly from 2 to 6 hours, 2 hourly till 12 hours, 4 hourly till 24 hours. The total requirement of epidural infusion will be calculated over first 24 hours in all 3 groups. Also, the QoR-15 score will be assessed for post-operative recovery in all the three groups at 24 hours and at the time of discharge. Mean length of hospital-stay will be compared in all three groups.

Any incidence of excessive sedation (-3 on Richmond agitation and sedation scale) respiratory depression (defined as fall in SpO2 below 90%, rise in PCO2 to more than 50 mm of Hg or by more than 20 mm of Hg from baseline value (immediate extubation), or higher or respiratory rate of <10/minute), nausea, vomiting, pruritis will be noted. In case of respiratory depression, supplemental oxygen with oxygen mask will be given to the patient. If patient still doesn’t respond endotracheal intubation with elective ventilation will be done and the incidence of same will be noted.