Impact of Opioid Free Anesthesia on the Complications After DIEPflap Surgery: A Retrospective Observational Cohort Study.

The investigators included all patients in the hospital database.belgium who underwent DIEPflap surgery between Jan 2014 and April 2019. All patients entering the hospital provided consent to allow retrospective data analysis without patient identification.

Because patient assignment to an operating day was determined without knowing who would perform the anesthesia on a few exceptions, the choice of opioid free anesthesia (OFA) or opioid anesthesia (OA) in most cases was random. Patients were classified as receiving OFA when no opioids were given pre- or intra- operatively until wound closure. Opioids given after wound closure were counted as post-operative opioids. Patients who received a lower dose of intra-operative opioids by using additives were still classified as OA. Post-operative opioid free analgesia was classified as receiving no opioids after wound closure until discharge from hospital in patients not receiving medium- or long-acting opioids, pre- or intra-operatively.

The method of reaching OFA remained stable since 2014. Dexmedetomidine was given in a first loading dose of 0.3 mcg/kg 15 minutes before induction, a second loading dose of 0.1 mcg/kg at induction followed by an infusion of 0.1 mcg/kg/h for maintenance. Lidocaine is given as a loading dose of 1 mg/kg at induction followed by 1 mg/kg/h for maintenance. A Ketamine loading dose of 0.1 mg/kg is given at induction with an extra bolus of 0.7 mg/kg (or max 50 mg) before incision followed by an infusion of 0.1mg/kg/h.

Post-operative analgesia was further improved by continuing very low doses of dexmedetomidine (0.05 mcg/kg/h), ketamine (0.05 mg/kg/h), and lidocaine (0.5 mg/kg/h) for the first hours (maximum 5 hours) with the possibility of giving a bolus of 10 mg lidocaine, 1 mg ketamine and 1 mcg dexmedetomidine every 15 minutes.

OA was induced with sufentanil (0.1 - 0.3 mcg/kg) and continued with extra boli (0.1 - 0.2 mcg/kg) or a continuous infusion of remifentanil (0.20 - 0.35 mcg/kg/h). Since 2014 more and more additives like clonidine, dexmedetomidine, ketamine and lidocaine were given as a single additive at the induction to reduce the total dose of intraoperative opioid use. Nevertheless these patients were still counted as OA.