Comparison of low doses of intrathecal morphine for postoperative analgesia A prospective randomized double blinded comparative study

This is a prospective randomised double blinded study, with computer generated randomisation. The patient will be allotted into group A or B representing 2mcg/kg and 5mcg/kg morphine dose.

PREOPERATIVE:

·      Routine clinical practice will be followed in all surgical cases as per institutional protocol. Data will be collected including patient characteristics- age, sex, height, weight, medical registration number etcetera, medical history- ASA physical status and comorbidities. Surgery- procedure and whether elective or emergency and coagulation profile also be noted. Patients will be recruited for the study only after obtaining written and verbal consent from the parents

INTRAOPERATIVE:

·      Baseline vitals will be noted. Routine induction will be done with IV Fentanyl 2 mcg/kg, IV Propofol 2-3 mg/kg and paralyzed with IV Rocuronium 0.5 mg/kg to facilitate endotracheal intubation. Anesthesia will be maintained with sevoflurane with air and oxygen mixture on low flow anesthesia. Patient will be positioned left lateral for intrathecal morphine injection. Under aseptic precautions, intrathecal morphine will be injected at L2-L3 space using 25G pencil point needle. Morphine will be diluted in 2 ml normal saline and injected once free flow of CSF is seen.

·      Observation: Post intrathecal morphine vitals will be documented every 5 mins in the first 30 mins and every 15 mins thereafter. A 20% or more increase in heart rate will be considered as “response to surgical stimulus”.

·      Analgesia: IV Paracetamol 15mg/kg and Diclofenac suppository 1mg/kg will be given to all patients as per institutional protocol. Intraoperatively IV Fentanyl may be increased further as rescue analgesia and it will be documented.

 POSTOPERATIVE:

·      After extubation patient will be observed in the Post Anaesthesia Care Unit (PACU) until the patient is fully awake and tolerating oral feed.

·      Vitals will be monitored and recorded every 15 mins in the first hour and every 30 mins in the second hour in the PACU.

·      IV Fentanyl 1mcg/kg will be given as rescue analgesia in the PACU. Paracetamol 15  mg/kg TID IV or oral will be prescribed to the patient after being discharged from the PACU. The nursing staff will monitor pain score every 3rd hourly. A FLACC score of >1 or Wong Baker faces scale of >2 or Numerical Pain score (NRS) >2 will be an indication for rescue analgesia. Tramadol 1 mg/kg oral or IV will be given as rescue analgesia in the ward.

·      Patient will be followed up for 24 hours in the post operative period. Nurse’s notes will be checked for vitals, pain score, nausea, and vomiting, pruritis of every hourly recorded by nursing staff. The primary investigator will follow up at 6, 12, 18, 24 hrs from the time of intrathecal morphine by calling up the respective ward. Time of rescue analgesia will also be noted.

·      The following questions will be asked to the nursing staff during the follow up:

1.     FLACC / Wong Baker faces pain score

2.     NRS pain score

3.     Nausea and vomiting

4.     Pruritis

5.     Urinary retention

6.     Saturation

7.     Any other event

Definition of Post Operative Nausea and Vomiting (PONV):

 Nausea is a nonobservable phenomenon of an unpleasant sensation experienced in the back of the throat and the epigastrium that may or may not culminate in vomiting.

Retching is an attempt to vomit without bringing anything up.

Vomiting is a forceful expulsion of gastric contents orally or nasally. PONV describes as nausea, vomiting, retching that can occur starting the PACU and continuing through 24 hours after surgery.

Patient will be observed for the following:

·      No retching, no vomiting

·      Retching but no vomiting

·      Vomiting

Treatment: to be given to patients with retching / vomiting.

First line: IV Ondansetron 0.1 mg/kg

Second line: IV Dexamethasone 0.1 mg/kg

 Definition of urinary retention:

 Post operative Urinary Retention (POUR) is the inability to void urine for >12 hours in the presence of palpable urinary bladder. Patients may complain of suprapubic pain or discomfort, visible abdominal distention maybe present due to overdistended bladder.

Treatment: Catheterisation

 Definition of pruritis:

Itching is an unpleasant sensation that leads to the desire to scratch. It is a subjective feeling and the objective measurement of it could be a challenge. Numerical Rating Scale (NRS)  for pruritis is the most commonly used assessment for pruritis.

 Treatment:

Mild to moderate pruritis - local application of Lactocalamine lotion

If not resolved, Tab. Cetirizine 5mg will be prescribed

Severe pruritis- IV. Naloxone 0.1 mg/kg/dose, this will be diluted in 10 cc syringe and aliquots of 10 mcg or 1 ml of Naloxone will be given every 2-3 mins until itching is resolved Definition of Respiratory depression:

 Respiratory rate of <10 per minute or saturation <93% or both will be considered as respiratory depression.

Treatment: administration of oxygen via face mask or nasal prongs.

If respiratory rate <10 per minute breaths will be assisted with IPPV with bag and mask, painful stimulus and Inj Naloxone 0.1 mg/kg/dose, this will be diluted in 10 cc syringe and aliquots of 10 mcg or 1ml of Naloxone will be given every 2-3 mins until respiratory depression is resolved.