The Incremental Risk of Intraoperative Fentanyl on PONV: A Modifiable Risk Without Drawbacks?

The primary aims of this quality control study are:

1. to determine whether there is an independent association between the intraoperative administration of fentanyl (both as a continuous and categorical variable) and PONV within 24 postoperative hours
2. determine whether or not the intraoperative fentanyl amount can be used to successfully restratify patients for PONV beyond the simplified Apfel score for PONV

All required data is collected in regular daily practice. The following variables will be assessed by univariable models:

Preoperative variables (e.g. patient characteristics) Surgical/Anesthesia variables (e.g. type/length of surgery, antiemetics) Outcome variables (PONV, worst pain as delineated in the outcomes section), Intraoperative fentanyl measured 1) as a continuous variable and 2) by predefined limits of 0 to 0.2mg, >0.2-0.5mg, >0.5 to 0.8mg, and >8mg.

Finally for the multivariable model, the investigators will adjust for confounders, specifically for sex (m/f), history (Hx) of PONV (y/n), Hx of motion sickness (y/n), current smoker (y/n), age (years), expected duration of surgery (min; >60 min), postoperative opioids (y/n), the use of preemptive PONV Therapy (0,1,2 medications), propofol vs. inhalative agents (y/n), and surgery type (3 kinds) from the patient's electronic record. In the event that insufficient event rates are observed, we will collapse the variables into the simplified Apfel score to assess the independent value of fentanyl in predicting PONV.