Olischar 2014.

Study characteristics
Methods	RCT, parallel groups
Participants	71 infants admitted to a primary newborn surgical unit in Australia Inclusion criteria: Neonates born ≥ 32 weeks postmenstrual who were requiring major thoracoabdominal surgery likely to require postoperative ventilation [e.g. thoracotomy for tracheoesophageal fistula repair, laparotomy for gastrointestinal surgery, or congenital diaphragmatic hernia repair] were recruited. Exclusion criteria: Patients requiring minor surgery (e.g. inguinal hernia), cardiac surgery, and those < 32 weeks corrected postmenstrual age were excluded, the latter two due to post‐surgical requirement or lung disease which confound the need for mechanical ventilation. Infants with hyperbilirubinemia requiring exchange transfusion were also excluded due to the impact on hepatic processing of acetaminophen and possibly tramadol.
Interventions	Tramadol: 2 mg/kg, infused intravenously over 15 minutes, 6‐hourly for 5 days or until extubation Placebo (saline solution)
Outcomes	Primary: time to extubation (hours) Secondary: analgesic and sedative medications (morphine, midazolam) received during the five days measured as duration of administration, number of boluses, total mg/kg; hourly pain scores; adverse events
Notes	Authors had nothing to declare regarding the performance of the study. Funding source: Murdoch Childrens Research Institute
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "An independent statistician performed computer‐generated (STATA 10; 2007, Stata Statistical Software, StataCorp, TX, USA) block randomization with variable block sizes, stratified by PMA: 32–36 weeks and > 36 weeks."
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "An independent pharmacist prepared study drug in 5‐mL Terumo [Philippines] syringes labeled with a study number. Each syringe contained 5 mL volume of either 50 mg tramadol in saline or saline alone (placebo) [the two being indistinguishable]".
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome assessment seemed to be blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All data appeared to be reported.
Selective reporting (reporting bias)	Unclear risk	Protocol not available
Other bias	Low risk	None

CRIES: Crying; Requires increased oxygen administration; Increased vital signs; Expression; Sleeplessness
ECG: electrocardiogram
FLACC: Face, Legs, Activity, Cry, Consolability
IV: intravenous
NFCS: Neonatal Facial Coding System
NRS‐11: numeric rating scale‐11
PMA: post‐menstrual age
RCT: randomized controlled trial