Difference in postoperative opioid consumption after spinal versus general anaesthesia for ankle fracture surgery—A retrospective cohort study

Surgical treatment of ankle fracture is associated with significant pain and high postoperative opioid consumption. The anaesthesia method may affect early postoperative pain. The main objective of the study was to compare postoperative opioid consumption after ankle‐fracture surgery between patients treated with spinal anaesthesia and general anaesthesia.

Pre-and intra-operative data were collected from the digital medical records and anaesthesia charts to characterize the study population (Table 1)  The information about the anaesthesia technique was collected from the digital anaesthesia charts. Due to the retrospective design of the study, the anaesthesia method was not preplanned. The anaesthesia was given according to the hospital's anaesthesia guideline for lower limb surgical procedures. The final decision between SA and GA and on postoperative analgesia was made by the attending anaesthesiologist based on possible contraindications and clinical assessment. When GA was selected, the induction was performed using an intravenous bolus of fentanyl and propofol, and maintenance of anaesthesia with sevoflurane. Fentanyl boluses were used for pain management during anaesthesia. A supraglottic airway device was used to secure the airway. If tracheal intubation was needed, rocuronium was used to facilitate the intubation in addition to fentanyl and propofol. Intrathecal or epidural analgesia were not used during GA. Intraoperative PNBs were not used. Bupivacaine was used for SA and intrathecal fentanyl was used to enhance the analgesic effect. Intrathecal morphine was not used in SA. The dosage of anaesthetics were adjusted individually by the attending anaesthesiologist.
In the PACU, pain was treated individually, mainly with oxycodone, acetaminophen, and ketoprofen. PNBs were used only if conservative pain management was insufficient. Acetaminophen was prescribed for almost every patient. NSAIDs (oral ibuprofen or intravenous ketoprofen) were not prescribed routinely but were administered for more intense pain. Opioids were given (intravenously and orally) whenever needed to reach the numeric rating scale (NRS) score ≤4. NRS was recorded when the patient arrived at the PACU, before and after the administration of analgesics and before the patient was discharged to the ward. An NRS score ≤4 was considered acceptable for discharge to the ward. According to our PACU guidelines, the anaesthetic effect (motor and sensory block) of SA must wear off before the patient can be discharged to the ward. In the ward, acetaminophen and NSAIDs were given routinely round the

Editorial Comment
The impact of spinal vs. general anesthesia for postoperative opioid consumption for ankle fractures was assessed retrospectively, with matching of cases between treatment groups. Findings showed less opioid consumption in the spinal anesthesia group over the hospitalization period, and predominantly in the post-anesthesia care unit. In the same (spinal anesthesia) group though, more opioid consumption was observed on the general ward, possibly a sign of rebound pain after regional anesthesia.
clock if there were no contraindications. Long-acting oxycodone was added to the medication if the pain was moderate to severe and/or persistent. The patient were given short-acting oxycodone perorally when needed.

| Primary outcome
The primary outcome was the total opioid consumption during the first 48 postoperative hours. Postoperatively administered opioids were converted into the intravenous equianalgesic dose of oxycodone in milligrams. Based on the recommendations in the product characteristics of intravenous oxycodone 13 and considering the variance in oral bioavailability found in different studies, [14][15][16][17] we applied a conversion ratio of 1:2 between intravenous and oral oxycodone.
The amount of oral codeine was converted into intravenous equianalgesic oxycodone in a relation of 20:1. 18 Intravenous fentanyl was converted into intravenous equianalgesic oxycodone in a relation of 1:75. 17,18 Opioid consumption during the surgical procedure, including intrathecal administration of fentanyl, was recorded but was not included in the analysis of postoperative opioid consumption.

| Secondary outcomes
Postoperative opioid consumption during the first 48 h was subdivided for secondary analysis to the PACU stay and time periods in the ward after surgery (the first 12 h, 12-24 h, 24-48 h). The subdivision was made to investigate the course of opioid consumption between GA and SA as the immediate postoperative hours are clinically interesting time periods. 6 The highest pain score reported by the patient during the PACU stay was used in the analysis. Clinically significant pain was reported and defined as NRS >5 because it has been noticed to be the cut-off point for preferred additional analgesic dose, 19 and we wanted to clearly differentiate patients with significant pain. Information on postoperative nausea and vomiting Abbreviations: ASA, American Society of Anaesthesiologists -classification score; BMI, body mass index.

| RE SULTS
The patient characteristics are shown in Table 1. A total of 662 patients were identified and 586 patients were included in the analysis, of whom 179 received SA and 407 had GA. Patients who received SA were older, had a higher ASA classification, and more commonly had diabetes than patients in the GA group. For the PSM population, 354 patients were paired, with 177 patients each in the SA and GA groups.
The primary outcomes are shown in Table 2  The secondary outcomes during the PACU stay are shown in

| D ISCUSS I ON
In the present study in patients undergoing ankle fracture fixation, the total opioid consumption was significantly higher in the GA group than in the SA group during the first 48 postoperative hours.
However, the difference resulted from the PACU period where the

| CON CLUS ION
Our results suggest that GA, compared with SA, is associated with an increase in total opioid consumption in the first 48 h after surgical ankle fracture fixation, mainly due to a higher opioid consumption in the PACU. Randomized controlled studies are needed to evaluate the effects of different anaesthesia and analgesia modalities on pain sensation and opioid consumption more comprehensively after ankle fracture surgery.

CO N FLI C T O F I NTE R E S T S
The authors have no conflict of interest. Timo I. Kaakinen https://orcid.org/0000-0001-5125-245X