Acetaminophen Does Not Reduce Postoperative Opiate Consumption in Patients Undergoing Craniotomy for Cerebral Revascularization: A Randomized Control Trial

Machine learning approach to predict postoperative opioid requirements in ambulatory surgery patients

Opioids play a critical role in acute postoperative pain management. Our objective was to develop machine learning models to predict postoperative opioid requirements in patients undergoing ambulatory surgery. To develop the models, we used a perioperative dataset of 13,700 patients (≥ 18 years) undergoing ambulatory surgery between the years 2016–2018. The data, comprising of patient, procedure and provider factors that could influence postoperative pain and opioid requirements, was randomly split into training (80%) and validation (20%) datasets. Machine learning models of different classes were developed to predict categorized levels of postoperative opioid requirements using the training dataset and then evaluated on the validation dataset. Prediction accuracy was used to differentiate model performances. The five types of models that were developed returned the following accuracies at two different stages of surgery: 1) Prior to surgery—Multinomial Logistic Regression: 71%, Naïve Bayes: 67%, Neural Network: 30%, Random Forest: 72%, Extreme Gradient Boost: 71% and 2) End of surgery—Multinomial Logistic Regression: 71%, Naïve Bayes: 63%, Neural Network: 32%, Random Forest: 72%, Extreme Gradient Boost: 70%. Analyzing the sensitivities of the best performing Random Forest model showed that the lower opioid requirements are predicted with better accuracy (89%) as compared with higher opioid requirements (43%). Feature importance (% relative importance) of model predictions showed that the type of procedure (15.4%), medical history (12.9%) and procedure duration (12.0%) were the top three features contributing to model predictions. Overall, the contribution of patient and procedure features towards model predictions were 65% and 35% respectively. Machine learning models could be used to predict postoperative opioid requirements in ambulatory surgery patients and could potentially assist in better management of their postoperative acute pain.

Effect of Intravenous Acetaminophen on Postoperative Hypoxemia After Abdominal Surgery: The FACTOR Randomized Clinical Trial

IMPORTANCE

Opioid-induced ventilatory depression and hypoxemia is common, severe, and often unrecognized in postoperative patients. To the extent that nonopioid analgesics reduce opioid consumption, they may decrease postoperative hypoxemia.

OBJECTIVE

To test the hypothesis that duration of hypoxemia is less in patients given intravenous acetaminophen than those given placebo.

DESIGN, SETTING, AND PARTICIPANTS

Randomized, placebo-controlled, double-blind trial conducted at 2 US academic hospitals among 570 patients who were undergoing abdominal surgery, enrolled from February 2015 through October 2018 and followed up until February 2019.

INTERVENTIONS

Participants were randomized to receive either intravenous acetaminophen, 1 g (n = 289), or normal saline placebo (n = 291) starting at the beginning of surgery and repeated every 6 hours until 48 postoperative hours or hospital discharge, whichever occurred first.

MAIN OUTCOMES AND MEASURES

The primary outcome was the total duration of hypoxemia (hemoglobin oxygen saturation [Spo2] <90%) per hour, with oxygen saturation measured continuously for 48 postoperative hours. Secondary outcomes were postoperative opioid consumption, pain (0- 10-point scale; 0: no pain; 10: the most pain imaginable), nausea and vomiting, sedation, minimal alveolar concentration of volatile anesthetic, fatigue, active time, and respiratory function.

RESULTS

Among 580 patients randomized (mean age, 49 years; 48% women), 570 (98%) completed the trial. The primary outcome, median duration with Spo2 of less than 90%, was 0.7 (interquartile range [IQR], 0.1-5.1) minutes per hour among patients in the acetaminophen group and 1.1 (IQR, 0.1-6.6) minutes per hour among patients in the placebo group (P = .29), with an estimated median difference of -0.04 (95% CI,-0.18 to 0.11) minutes per hour. None of the 8 secondary end points differed significantly between the acetaminophen and placebo groups. Mean pain scores within initial 48 postoperative hours were 4.2 (SD, 1.8) in the acetaminophen group and 4.4 (SD, 1.8) in the placebo group (difference, -0.28; 95% CI, -0.71 to 0.15); median opioid use in morphine equivalents was 50 mg (IQR, 18-122 mg) and 58 mg (IQR, 24-151 mg) , respectively, with a ratio of geometric means of 0.86 (95% CI, 0.61-1.21).

CONCLUSIONS AND RELEVANCE

Among patients who underwent abdominal surgery, use of postoperative intravenous acetaminophen, compared with placebo, did not significantly reduce the duration of postoperative hypoxemia over 48 hours. The study findings do not support the use of intravenous acetaminophen for this purpose.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02156154.

Pharmacological interventions for the prevention of acute postoperative pain in adults following brain surgery

BACKGROUND

Pain following brain surgery can compromise recovery. Several pharmacological interventions have been used to prevent pain after craniotomy; however, there is currently a lack of evidence regarding which interventions are most effective.

OBJECTIVES

The objectives are to assess the effectiveness of pharmacological interventions for prevention of acute postoperative pain in adults undergoing brain surgery; compare them in terms of additional analgesic requirements, incidence of chronic headache, sedative effects, length of hospital stay and adverse events; and determine whether these characteristics are different for certain subgroups.

SEARCH METHODS

We searched MEDLINE, Embase, CINAHL, CENTRAL, Web of Science and two trial registries together with reference checking and citation searching on 28th of November 2018.

SELECTION CRITERIA

We included blinded and non-blinded, randomized controlled trials evaluating pharmacological interventions for the prevention of acute postoperative pain in adults undergoing neurosurgery, which had at least one validated pain score outcome measure.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. We calculated mean differences for the primary outcome of pain intensity; any pain scores reported on a 0 to 100 scale were converted to a 0 to 10 scale.

MAIN RESULTS

We included 42 completed studies (3548 participants) and identified one ongoing study. Nonsteroidal anti-inflammatories (NSAIDs) Nonsteroidal anti-inflammatories (NSAIDs) reduce pain up to 24 hours (0 to 6 hours, MD -1.16, 95% CI -1.57 to -0.76; 12 hours, MD -0.62, 95% CI -1.11 to -0.14; 24 hours, MD -0.66, 95% CI -1.18 to -0.13; 6 studies, 742 participants; all high-quality evidence). Results for other outcomes were imprecise (additional analgesic requirements: MD 1.29 mg, 95% CI -5.0 to 2.46, 4 studies, 265 participants; nausea and vomiting RR 1.34, 95% CI 0.30 to 5.94, 2 studies, 345 participants; both low-quality evidence). Dexmedetomidine reduces pain up to 12 hours (0 to 6 hours, MD -0.89, 95% CI -1.27 to -0.51, moderate-quality evidence; 12 hours, MD -0.81, 95% CI -1.21 to -0.42, low-quality evidence). It did not show efficacy at 24 hours (MD -0.08, 95% CI -0.32 to 0.16; 2 studies, 128 participants; low-quality evidence). Dexmedetomidine may decrease additional analgesic requirements (MD -21.36 mg, 95% CI -34.63 to -8.1 mg, 2 studies, 128 participants, low-quality evidence). Results for other outcomes were imprecise (nausea and vomiting RR -0.43, 95% CI 0.06 to 3.08, 3 studies, 261 participants; hypotension RR 0.5, 95% CI 0.05 to 5.28, 3 studies, 184 participants; both low-quality evidence). Scalp blocks may reduce pain up to 48 hours (0 to 6 hours, MD -0.98, 95% CI -1.66 to -0.3, 10 studies, 414 participants; 12 hours, MD -0.95, 95% CI -1.53 to -0.37, 8 studies, 294 participants; 24 hours, MD -0.78, 95% CI -1.52 to -0.05, 9 studies, 433 participants, all low-quality evidence; 48 hours, MD -1.34, 95% CI -2.57 to -0.11, 4 studies, 135 participants, very low-quality evidence. When studies with high risk of bias were excluded, significance remained at 12 hours only. Scalp blocks may decrease additional analgesia requirements (SMD -1.11, 95% CI -1.97 to -0.25, 7 studies, 314 participants). Results for other outcomes were imprecise (nausea and vomiting RR 0.66, 95% CI 0.33 to 1.32, 4 studies, 165 participants, very low-quality evidence). Scalp Infiltration may reduce pain postoperatively but efficacy was inconsistent, with a significant effect at 12 and 48 hours only (12 hours, MD -0.71, 95% CI -1.34 to -0.08, 7 studies, 309 participants, low-quality evidence; 48 hours, MD - 1.09, 95% CI -2.13 to - 0.06, 3 studies, 128 participants, moderate-quality evidence). No benefit was observed at other times (0 to 6 hours, MD -0.64, 95% CI -1.28 to -0.00, 9 studies, 475 participants, moderate-quality evidence; 24 hours, MD -0.39, 95% CI -1.06 to 0.27,6 studies, 260 participants, low-quality evidence. Scalp infiltration may reduce additional analgesia requirements MD -9.56 mg, 95% CI -15.64 to -3.49, 6 studies, 345 participants, very low-quality evidence). When studies with high risk of bias were excluded, scalp infiltration lost the pain benefit at 12 hours and effects on additional analgesia requirements, but retained the pain-reducing benefit at 48 hours (MD -0.56, 95% CI -1.20 to -0.32, 2 studies, 100 participants, very low-quality evidence). Results for other outcomes were imprecise (nausea and vomiting, RR 0.74, 95% CI 0.48 to 1.41, 4 studies, 318 participants, low-quality evidence). Pregabalin or gabapentin may reduce pain up to 6 hours (2 studies, 202 participants), MD -1.15,95% CI -1.66 to -0.6, 2 studies, 202 participants, low-quality evidence). One study examined analgesic efficacy at 12 hours showing significant benefit. No analgesia efficacy was shown at later times (24 hours, MD -0.29, 95% CI -0.78 to -0.19; 48 hours, MD - 0.06, 95% CI -0.86 to 0.77, 2 studies, 202 participants, low-quality evidence). Additional analgesia requirements were not significantly less (MD -0.37 (95% CI -1.10 to 0.35, 3 studies, 234 participants, low-quality evidence). Risk of nausea and vomiting was significantly reduced (RR 0.51, 95% CI 0.29 to 0.89, 3 studies, 273 participants, low-quality evidence). Results for other outcomes were imprecise (additional analgesia requirements: MD -0.37, 95% CI -1.10 to 0.35, 3 studies, 234 participants, low-quality evidence). Acetaminophen did not show analgesic benefit (0 to 6 hours, MD -0.35, 95% CI -1.00 to 0.30; 12 hours, MD -0.51, 95% CI -1.04 to 0.03, 3 studies, 332 participants, moderate-quality evidence; 24 hours, MD -0.34, 95% CI -1.20 to 0.52, 4 studies, 439 participants, high-quality evidence). Results for other outcomes remained imprecise (additional analgesia requirements, MD 0.07, 95% CI -0.86 to 0.99, 4 studies, 459 participants, high-quality evidence; length of hospitalizations, MD -3.71, 95% CI -14.12 to 6.7, 2 studies, 335 participants, moderate-quality evidence).

AUTHORS' CONCLUSIONS

There is high-quality evidence that NSAIDs reduce pain up to 24 hours postoperatively. The evidence for reductions in pain with dexmedetomidine, pregabalin or gabapentin, scalp blocks, and scalp infiltration is less certain and of very low to moderate quality. There is low-quality evidence that scalp blocks and dexmedetomidine may reduce additional analgesics requirements. There is low-quality evidence that gabapentin or pregabalin may decrease nausea and vomiting, with the caveat that the total number of events for this comparison was low.