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Background Perioperative hyperoxia has been recommended by the World Health Organization and the Centers for Disease Control and Prevention for the prevention of surgical site infections. Based on animal studies and physiological concerns, the kidneys and heart may be at risk from hyperoxia. We therefore conducted 2 unplanned subanalyses of a previous alternating cohort trial in which patients having colorectal surgery were assigned to either 30% or 80% inspired intraoperative oxygen. Specifically, we tested 2 coprimary hypotheses: (1) hyperoxia increases the incidence of acute kidney injury (AKI) within 7 postoperative days (PODs); and (2) hyperoxia worsens a composite of myocardial injury, in-hospital cardiac arrest, and 30-day mortality. Methods The underlying controlled trial included 5749 colorectal surgeries in 4481 patients, with the exposure alternating between 30% and 80% fraction of inspired oxygen (FIO2) during general anesthesia at 2-week intervals over a period of 39 months. AKI was defined as a 1.5-fold increase in creatinine from the preoperative level to the highest value measured during the initial 7 PODs. Myocardial injury was defined by fourth-generation troponin-T level >0.03 ng/mL. We assessed the effect of 80% vs 30% oxygen on the outcomes using generalized estimating equation (GEE) logistic models that adjusted for the possible within-patient correlation across multiple potential operations for a patient on different visits. Results For the AKI outcome, 2522 surgeries were allocated to 80% oxygen and 2552 to 30% oxygen. Hyperoxia had no effect on the primary outcome of postoperative AKI, with an incidence of 7.7% in the 80% oxygen group and 7.7% in the 30% oxygen group (relative risk = 0.99; 95% confidence interval [CI], 0.82-1.2; P = .95). One thousand six hundred forty-seven surgeries (all with scheduled troponin monitoring) were analyzed for the composite cardiovascular outcome. Hyperoxia had no effect on the collapsed composite of myocardial injury, cardiac arrest, and 30-day mortality, nor on any of its components (estimated relative risk = 0.71; 95% CI, 0.44-1.16; P = .17). Conclusions We found no evidence that intraoperative hyperoxia causes AKI or cardiovascular complications in adults undergoing colorectal surgery. Consequently, we suggest that clinicians select intraoperative inspired oxygen fraction based on other considerations.

Myocardial injury after noncardiac surgery (MINS) differs from myocardial infarction in being defined by troponin elevation apparently from cardiac ischemia with or without signs and symptoms. Such myocardial injury is common, silent, and strongly associated with mortality. MINS is usually asymptomatic and only detected by routine troponin monitoring. There is currently no known safe and effective prophylaxis for perioperative myocardial injury. However, appropriate preoperative screening may help guide proactive postoperative preventative actions. Intraoperative hypotension is associated with myocardial injury, acute kidney injury, and death. Hypotension is common and largely undetected in the postoperative general care floor setting, and independently associated with myocardial injury and mortality. Critical care patients are especially sensitive to hypotension, and the risk appears to be present at blood pressures previously regarded as normal. Tachycardia appears to be less important. Available information suggests that clinicians would be prudent to avoid perioperative hypotension.

BACKGROUND Neuraxial anesthesia improves components of the Virchow's triad (hypercoagulability, venous stasis, and endothelial injury) which are key pathogenic contributors to venous thrombosis in surgical patients. However, whether neuraxial anesthesia reduces the incidence of venous thromboembolism (VTE) remain unclear. We therefore tested the primary hypothesis that neuraxial anesthesia reduces the incidence of 30-day VTE in adults recovering from orthopedic surgery. Secondarily, we tested the hypotheses that neuraxial anesthesia reduces 30-day readmission, 30-day mortality, and the duration of postoperative hospitalization. METHODS Inpatient orthopedic surgeries from American College of Surgeons National Surgical Quality Improvement Program database (2011-2015) in adults lasting more than 1 hour with either neuraxial or general anesthesia were included. Groups were matched 1:1 by propensity score matching for appropriate confounders. Logistic regression model was used to assess the effect of neuraxial anesthesia on 30-day VTE, 30-day mortality, and readmission, while Cox proportional hazard regression model was used to assess its effect on length of stay. RESULTS Neuraxial anesthesia decreased odds of 30-day VTE (odds ratio 0.85, 95% confidence interval, 0.78-0.95; P = .002) corresponding to number-needed-to-treat of 500. Although there was no difference in 30-day mortality, neuraxial anesthesia reduced 30-day readmission (odds ratio 0.90, 98.3% confidence interval, 0.85-0.95; P < .001) corresponding to number-needed-to-treat of 250 and had a shortened hospitalization (2.87 vs 3.11; P < .001). CONCLUSIONS Neuraxial anesthesia appears to provide only weak VTE prophylaxis, but can be offered as an adjuvant to current thromboprophylaxis in high-risk patients.

Background Laboratory testing is a common component of preanesthesia evaluation and is designed to identify medical abnormalities that might otherwise remain undetected. While blood testing might optimally be performed shortly before surgery, it is often done earlier for practical reasons. We tested the hypothesis that longer periods between preoperative laboratory testing and surgery are associated with increased odds of having a composite of 30-day morbidity and mortality. Methods We obtained preoperative data from 2,320,920 patients in the American College of Surgeons National Surgical Quality Improvement Program who were treated between 2005 and 2012. Our analysis was restricted to relatively healthy patients with American Society of Anesthesiology physical status I-II who had elective surgery and normal blood test results (n = 235,010). The primary relationship of interest was the odds of 30-day morbidity and mortality as a function of delay between preoperative testing and surgery. A multivariable logistic regression model was used for the 10 pairwise comparisons among the 5 laboratory timing groups (laboratory blood tests within 1 week of surgery; 1-2 weeks; 2-4 weeks; 1-2 months; and 2-3 months) on 30-day morbidity, adjusting for any imbalanced baseline covariables and type of surgery. Results A total of 4082 patients (1.74%) had at least one of the component morbidities or died within 30-days after surgery. The observed incidence (unadjusted) was 1.7% when the most recent laboratory blood tests measured within 1 week of surgery, 1.7% when it was within 1-2 weeks, 1.8% when it was within 2-4 weeks, 1.7% when it was between 1 and 2 months, and 2.0% for patients with most recent laboratory blood tests measured 2-3 months before surgery. None of the values within 2 months differed significantly: estimated odds ratios for patients within blood tested within 1 week were 1.00 (99.5% confidence interval, 0.89-1.12) as compared to 1-2 weeks, 0.88 (0.77-1.00) for 2-4 weeks, and 0.95 (0.79-1.14) for 1-2 months, respectively. The estimated odds ratio comparing 1-2 weeks to each of 2-4 weeks and 1-2 months were 0.88 (0.76-1.03) and 0.95 (0.78-1.16), respectively. Blood testing 2-3 months before surgery was associated with increased odds of outcome compared to patients whose most recent test was within 1 week (P = .002) and 1-2 weeks of the date of surgery. Conclusions In American Society of Anesthesiologists physical status I and II patients, risk of 30-day morbidity and mortality was not different with blood testing up to 2 months before surgery, suggesting that it is unnecessary to retest patients shortly before surgery.

As noted in part 1 of this series, periprocedural cardiac arrest (PPCA) can differ greatly in etiology and treatment from what is described by the American Heart Association advanced cardiac life support algorithms, which were largely developed for use in out-of-hospital cardiac arrest and in-hospital cardiac arrest outside of the perioperative space. Specifically, there are several life-threatening causes of PPCA of which the management should be within the skill set of all anesthesiologists. However, previous research has demonstrated that continued review and training in the management of these scenarios is greatly needed and is also associated with improved delivery of care and outcomes during PPCA. There is a growing body of literature describing the incidence, causes, treatment, and outcomes of common causes of PPCA (eg, malignant hyperthermia, massive trauma, and local anesthetic systemic toxicity) and the need for a better awareness of these topics within the anesthesiology community at large. As noted in part 1 of this series, these events are always witnessed by a member of the perioperative team, frequently anticipated, and involve rescuer-providers with knowledge of the patient and the procedure they are undergoing or have had. Formulation of an appropriate differential diagnosis and rapid application of targeted interventions are critical for good patient outcome. Resuscitation algorithms that include the evaluation and management of common causes leading to cardiac in the perioperative setting are presented. Practicing anesthesiologists need a working knowledge of these algorithms to maximize good outcomes.

Cardiac arrest in the operating room and procedural areas has a different spectrum of causes (ie, hypovolemia, gas embolism, and hyperkalemia), and rapid and appropriate evaluation and management of these causes require modification of traditional cardiac arrest algorithms. There is a small but growing body of literature describing the incidence, causes, treatments, and outcomes of circulatory crisis and perioperative cardiac arrest. These events are almost always witnessed, frequently known, and involve rescuer providers with knowledge of the patient and their procedure. In this setting, there can be formulation of a differential diagnosis and a directed intervention that treats the likely underlying cause(s) of the crisis while concurrently managing the crisis itself. Management of cardiac arrest of the perioperative patient is predicated on expert opinion, physiologic rationale, and an understanding of the context in which these events occur. Resuscitation algorithms should consider the evaluation and management of these causes of crisis in the perioperative setting.

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One small study suggests that gargling with licorice before induction of anesthesia reduces the risk of postoperative sore throat. Double-lumen tubes are large and thus especially likely to provoke sore throats. We therefore tested the hypothesis that preoperative gargling with licorice solution prevents postoperative sore throat and postextubation coughing in patients intubated with double-lumen tubes.We enrolled 236 patients having elective thoracic surgery who required intubation with a double-lumen endotracheal tube. Patients were randomly assigned to gargle 5 minutes before induction of anesthesia for 1 minute with: (1) Extractum Liquiritiae Fluidum (licorice 0.5 g); or (2) Sirupus Simplex (sugar 5 g); each diluted in 30 mL water. Sore throat and postextubation coughing were evaluated 30 minutes, 90 minutes, and 4 hours after arrival in the postanesthesia care unit, and the first postoperative morning using an 11-point Likert scale by an investigator blinded to treatment.The incidence of postoperative sore throat was significantly reduced in patients who gargled with licorice rather than sugar-water: 19% and 36% at 30 minutes, 10% and 35% at 1.5 hours, and 21% and 45% at 4 hours, respectively. The corresponding estimated treatment effects (relative risks) were 0.54 (95% CI, 0.30-0.99, licorice versus sugar-water; P = 0.005), 0.31 (0.14-0.68) (P0.001), and 0.48 (0.28-0.83) (P0.001).Licorice gargling halved the incidence of sore throat. Preinduction gargling with licorice appears to be a simple way to prevent a common and bothersome complication.