Association between intra-operative fentanyl dosing and postoperative nausea/vomiting and pain: A prospective cohort study.

BACKGROUND

Postoperative nausea and/or vomiting (PONV) is one of the anaesthesia-related effects most dreaded by patients and may delay hospital discharge. Although scores and risk factors are established, many were developed before contemporary anaesthesia regimens and without focussing on modifiable anaesthesia-related variables.

OBJECTIVE

To examine whether, in association with a contemporary anaesthesia regimen, there is an association between intra-operative fentanyl dose and PONV, and, second, postoperative pain within the first 24 h.

DESIGN

Prospective, observational cohort.

SETTING

Single-centre university hospital.

PATIENTS

Inclusion criteria were opioid-naive patients without chronic pain and with a simplified Apfel score at least 2 undergoing abdominal, gynaecological or otorhinolaryngological inpatient surgery.

INTERVENTION

None.

MAIN OUTCOME MEASURE

With logistic regression, we examined three models of increasing complexity exploring the relationship between PONV and fentanyl dosing: Model 1, simplified Apfel score + intra-operative fentanyl; Model 2, Model 1 + pre-emptive antiemetic prophylaxis; Model 3, Model 2 + postoperative morphine. Model 1 was the primary analysis. Second, we explored whether or not postoperative pain scores were associated with intra-operative fentanyl dosing.

RESULTS

From the 363 patients, 163 (45%) experienced PONV, despite the use of total intravenous anaesthesia with propofol in more than 80% of the cohort, and some 66% of patients receiving additional antiemetic agents. After adjusting for the simplified Apfel score, higher intra-operative fentanyl dose was associated with PONV: odds ratio per μg h, 1.006 [95% confidence interval (CI) 1.002 to 1.010]. Including intra-operative fentanyl in the simplified Apfel score also increased the area under the receiver operator characteristics curve [0.601 (95% CI 0.555 to 0.662) vs. 0.651 (95% CI 0.594 to 0.707); P = 0.016]. Finally, a higher intra-operative fentanyl dose was associated with higher 24 h pain scores (P = 0.001) and a trend towards higher 24 h morphine requirements (P = 0.055).

CONCLUSION

Even when using propofol and antiemetic agents, PONV within the first 24 h remained higher than expected. Intra-operative fentanyl, a modifiable risk factor, is associated with the incidence of PONV and postoperative pain.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03201315.