Trends and In-Hospital Mortality for Perioperative Myocardial Infarction After the Introduction of a Diagnostic Code for Type 2 Myocardial Infarction in the United States Between 2016 and 2018

BACKGROUND

The frequency of perioperative myocardial infarction has been declining; however, previous studies have only described type 1 myocardial infarctions. Here, we evaluate the overall frequency of myocardial infarction with the addition of an International Classification of Diseases 10th revision (ICD-10-CM) code for type 2 myocardial infarction and the independent association with in-hospital mortality.

METHODS

A longitudinal cohort study spanning the introduction of the ICD-10-CM diagnostic code for type 2 myocardial infarction using the National Inpatient Sample (NIS) from 2016 to 2018. Hospital discharges that included a primary surgical procedure code for intrathoracic, intraabdominal, or suprainguinal vascular surgery were included. Type 1 and type 2 myocardial infarctions were identified using ICD-10-CM codes. We used segmented logistic regression to estimate change in frequency of myocardial infarctions and multivariable logistic regression to determine the association with in-hospital mortality.

RESULTS

A total of 360,264 unweighted discharges were included, representing 1,801,239 weighted discharges, with median age 59 and 56% female. The overall incidence of myocardial infarction was 0.76% (13,605/1,801,239). Before the introduction of type 2 myocardial infarction code, there was a small baseline decrease in the monthly frequency of perioperative myocardial infarctions (odds ratio [OR], 0.992; 95% confidence interval [CI], 0.984-1.000; P  =   .042), but no change in the trend after the introduction of the diagnostic code (OR, 0.998; 95% CI, 0.991-1.005; P  =   .50). In 2018, where there was an entire year where type 2 myocardial infarction was officially a diagnosis, the distribution of myocardial infarction type 1 was 8.8% (405/4580) ST elevation myocardial infarction (STEMI), 45.6% (2090/4580) non-ST elevation myocardial infarction (NSTEMI), and 45.5% (2085/4580) type 2 myocardial infarction. STEMI and NSTEMI were associated with increased in-hospital mortality (OR, 8.96; 95% CI, 6.20-12.96; P < .001 and OR, 1.59; 95% CI, 1.34-1.89; P < .001). A diagnosis of type 2 myocardial infarction was not associated with increased odds of in-hospital mortality (OR, 1.11; 95% CI, 0.81-1.53; P  =   .50) when accounting for surgical procedure, medical comorbidities, patient demographics, and hospital characteristics.

CONCLUSIONS

The frequency of perioperative myocardial infarctions did not increase after the introduction of a new diagnostic code for type 2 myocardial infarctions. A diagnosis of type 2 myocardial infarction was not associated with increased in-patient mortality; however, few patients received invasive management that may have confirmed the diagnosis. Further research is needed to identify what type of intervention, if any, may improve outcomes in this patient population.

Persistent Brain Connectivity Changes in Healthy Volunteers Following Nitrous Oxide Inhalation

Background

Nitrous oxide holds promise in the treatment of major depressive disorder. Its psychotropic effects and NMDA receptor antagonism have led to comparisons with ketamine. Despite longstanding use, persistent effects of nitrous oxide on the brain have not been characterized.

Methods

Sixteen healthy volunteers were recruited in a double-blind crossover study. In randomized order, individuals underwent a 1-hour inhalation of either 50% nitrous oxide/oxygen or air/oxygen mixtures. At least two 7.5-minute echo-planar resting-state functional magnetic resonance imaging scans were obtained before and at 2 and 24 hours after each inhalation (average 130 min/participant). Using the time series of preprocessed, motion artifact-scrubbed, and nuisance covariate-regressed imaging data, interregional signal correlations were measured and converted to T scores. Hierarchical clustering and linear mixed-effects models were employed.

Results

Nitrous oxide inhalation produced changes in global brain connectivity that persisted in the occipital cortex at 2 and 24 hours postinhalation (p < .05, false discovery rate-corrected). Analysis of resting-state networks demonstrated robust strengthening of connectivity between regions of the visual network and those of the dorsal attention network, across 2 and 24 hours after inhalation (p < .05, false discovery rate-corrected). Weaker changes in connectivity were found between the visual cortex and regions of the frontoparietal and default mode networks. Parallel analyses following air/oxygen inhalation yielded no significant changes in functional connectivity.

Conclusions

Nitrous oxide inhalation in healthy volunteers revealed persistent increases in global connectivity between regions of primary visual cortex and dorsal attention network. These findings suggest that nitrous oxide inhalation induces neurophysiological cortical changes that persist for at least 24 hours.

Rare missense variants in the SH3 domain of PSTPIP1 are associated with hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic, debilitating skin disease for which few treatment options are available. While most HS is sporadic, some rare kindred show a high-penetrance, autosomal-dominant inheritance. We wanted to identify rare variants that could contribute to HS risk in sporadic cases using candidate gene sequencing. We ultimately identified 21 genes for our capture panel. We included genes of the γ-secretase complex (n = 6) because rare variants in these genes sometimes cause familial HS. We added Notch receptor and ligand genes (n = 13) because γ-secretase is critical for processing Notch receptor signaling. Clinically, some people with PAPA (pyogenic arthritis, pyoderma gangrenosum, and acne) syndrome, a rare inflammatory disease, have concurrent HS. Rare variants in PSTPIP1 are known to cause PAPA syndrome, so we included PSTPIP1 and PSTPIP2 in the capture panel. We screened 117 individuals with HS for rare variations and calculated the expected burden using Genome Aggregation Database (gnomAD) allele frequencies. We discovered two pathogenic loss-of-function variants in NCSTN. This class of NCSTN variant can cause familial HS. There was no increased burden of rare variations in any γ-secretase complex gene. We did find that individuals with HS had a significantly increased number of rare missense variants in the SH3 domain of PSTPIP1. This finding, therefore, implicates PSTPIP1 variation in sporadic HS and further supports dysregulated immunity in HS. Our data also suggests that population-scale HS genetic research will yield valuable insights into disease pathology.

Preoperative β-Blocker Therapy and Stroke or Major Adverse Cardiac Events in Major Abdominal Surgery: A Retrospective Cohort Study

BACKGROUND

Perioperative β-blocker therapy has been associated with increased risk of stroke. However, the association between β-blocker initiation before the day of surgery and the risk of stroke is unknown. The authors hypothesized there would be no association between preoperative β-blocker initiation within 60 days of surgery or chronic β-blockade (more than 60 days) and the risk of stroke in patients undergoing major abdominal surgery.

METHODS

Data on elective major abdominal surgery were obtained from the IBM (USA) Truven Health MarketScan 2005 to 2015 Commercial and Medicare Supplemental Databases. Patients were stratified by β-blocker dispensing exposure: (1) β-blocker-naïve, (2) preoperative β-blocker initiation within 60 days of surgery, and (3) chronic β-blocker dispensing (more than 60 days). The authors compared in-hospital stroke and major adverse cardiac events between the different β-blocker therapy exposures.

RESULTS

There were 204,981 patients who underwent major abdominal surgery. β-Blocker exposure was as follows: perioperative initiation within 60 days of surgery for 4,026 (2.0%) patients, chronic β-blocker therapy for 45,424 (22.2%) patients, and β-blocker-naïve for 155,531 (75.9%) patients. The unadjusted frequency of stroke for patients with β-blocker initiation (0.4%, 17 of 4,026) and chronic β-blocker therapy (0.4%, 171 of 45,424) was greater than in β-blocker-naïve patients (0.2%, 235 of 155,531; P < 0.001). After propensity score weighting, patients initiated on a β-blocker within 60 days of surgery (odds ratio, 0.90; 95% CI, 0.31 to 2.04; P = 0.757) or on chronic β-blocker therapy (odds ratio, 0.86; 95% CI, 0.65 to 1.15; P = 0.901) demonstrated similar stroke risk compared to β-blocker-naïve patients. Patients on chronic β-blocker therapy demonstrated lower adjusted risk of major adverse cardiac events compared to β-blocker-naïve patients (odds ratio, 0.81; 95% CI, 0.72 to 0.91; P = 0.007), despite higher unadjusted absolute event rate (2.6% [1,173 of 45,424] vs. 0.6% [872 of 155,531]).

CONCLUSIONS

Among patients undergoing elective major abdominal surgery, the authors observed no association between preoperative β-blocker initiation within 60 days of surgery or chronic β-blocker therapy and stroke.

EDITOR’S PERSPECTIVE

Nitrous Oxide, a Rapid Antidepressant, Has Ketamine-like Effects on Excitatory Transmission in the Adult Hippocampus

BACKGROUND

Nitrous oxide (N2O) is a noncompetitive inhibitor of NMDA receptors that appears to have ketamine-like rapid antidepressant effects in patients with treatment-resistant major depression. In preclinical studies, ketamine enhances glutamate-mediated synaptic transmission in the hippocampus and prefrontal cortex. In this study, we examined the effects of N2O on glutamate transmission in the hippocampus and compared its effects to those of ketamine.

METHODS

Glutamate-mediated synaptic transmission was studied in the CA1 region of hippocampal slices from adult albino rats using standard extracellular recording methods. Effects of N2O and ketamine at subanesthetic concentrations were evaluated by acute administration.

RESULTS

Akin to 1 μM ketamine, 30% N2O administered for 15-20 minutes resulted in persistent enhancement of synaptic responses mediated by both AMPA receptors and NMDA receptors. Synaptic enhancement by both N2O and ketamine was blocked by co-administration of a competitive NMDA receptor antagonist at saturating concentration, but only ketamine was blocked by an AMPA receptor antagonist. Synaptic enhancement by both agents involved TrkB (tropomyosin receptor kinase B), mTOR (mechanistic target of rapamycin), and NOS (nitric oxide synthase) with some differences between N2O and ketamine. N2O potentiation occluded enhancement by ketamine, and in vivo N2O exposure occluded further potentiation by both N2O and ketamine.

CONCLUSIONS

These results indicate that N2O has ketamine-like effects on hippocampal synaptic function at a subanesthetic, but therapeutically relevant concentration. These 2 rapid antidepressants have similar, but not identical mechanisms that result in persisting synaptic enhancement, possibly contributing to psychotropic actions.

Normalized Subendocardial Myocardial Attenuation on Coronary Computed Tomography Angiography Predicts Postoperative Adverse Cardiovascular Events: Coronary CTA VISION Substudy

BACKGROUND

Abnormalities in computed tomography myocardial perfusion has been associated with coronary artery disease and major adverse cardiovascular events (MACE). We sought to investigate if subendocardial attenuation using coronary computed tomography angiography predicts MACE 30 days postelective noncardiac surgery.

METHODS

Using a 17-segment model, coronary computed tomography angiography images were analyzed for subendocardial and transmural attenuation and the corresponding blood pool. The segment with the lowest subendocardial attenuation and transmural attenuation were normalized to the segment with the highest subendocardial and transmural attenuation, respectively (SUB_normalized, and TRANS_normalized, respectively). We evaluated the independent and incremental value of myocardial attenuation to predict the composite of cardiovascular death or nonfatal myocardial infarction.

RESULTS

Of a total of 995 coronary CTA VISION (Coronary Computed Tomographic Angiography and Vascular Events in Noncardiac Surgery Patients Cohort Evaluation Study) patients, 735 had available images and complete data for these analyses. Among these patients, 60 had MACE. Based on Revised Cardiovascular Risk Index, 257, 302, 138, and 38 patients had scores of 0, 1, 2, and ≥3, respectively. On coronary computed tomography angiography, 75 patients had normal coronary arteries, 297 patients had nonobstructive coronary artery disease, 264 patients had obstructive disease, and 99 patients had extensive obstructive coronary artery disease. SUB_normalized was an independent and incremental predictor of events in the model that included Revised Cardiovascular Risk Index and coronary artery disease severity. Compared with patients in the highest tertile of SUB_normalized, patients in the second and first tertiles had an increased hazards ratio for events (2.23 [95% CI, 1.091-4.551] and 2.36 [95% CI, 1.16-4.81], respectively). TRANS_normalized, as a continuous variable, was also found to be a predictor of MACE (P=0.027).

CONCLUSIONS

Our study demonstrates that SUB_normalized and TRANS_normalized are independent and incremental predictors of MACE 30 days after elective noncardiac surgery. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01635309.

Preoperative Assessment of Anxiety and Depression Using Computerized Adaptive Screening Tools: A Pilot Prospective Cohort Study

BACKGROUND

Serious mental health conditions (eg, anxiety and depression) are common in surgical patients, yet likely underassessed due to the time-consuming and cumbersome traditional screening process. A recently developed computerized adaptive mental health assessment tool (computerized adaptive test-mental health [CAT-MH]) allows rapid, precise, and accurate assessment of numerous mental health disorders, including anxiety and depression, without the need for a trained interviewer. The goal of this investigation was to determine the feasibility of administering CAT-MH for anxiety and depression in the preoperative setting and to obtain preliminary evidence of the prevalence of anxiety and depression in preoperative patients.

METHODS

In this prospective cohort study, 100 adult patients scheduled for elective surgery were enrolled and asked to complete the CAT-MH in the preoperative clinic. Urgent and emergency surgeries were excluded as were pregnant patients. Primary feasibility outcomes were completion rate and time to completion. Secondary outcomes were prevalence estimates of anxiety and depression.

RESULTS

All 100 enrolled patients completed the study. All patients were able to complete the mental health assessment (mean time: 3.6 ± 1.8 minutes standard deviation). Sixteen patients (16%) screened positive for anxiety (severity: mild, n = 7 [7%]; moderate, n = 7 [7%]); severe, n = 2 [2%]); 12 of 16 (75%) did not have a previous diagnosis of anxiety disorder. Twenty-eight (28%) patients screened positive for depression (severity: mild, n = 26 [26%]; moderate and severe, n = 1 each [1%]); 23 of 28 (82%) had no previous diagnosis of depressive disorder. Nineteen patients (19%) met the screening criteria for major depressive disorder; 14 of 19 (74%) of which had no previous diagnosis of major depressive disorder.

CONCLUSIONS

The results of this pilot study support the feasibility of using CAT-MH in a preoperative evaluation and indicate that there is a substantial prevalence of undiagnosed anxiety and depression in surgical patients.

U.S. trends in elective and emergent major abdominal surgical procedures from 2002 to 2014 in older adults

BACKGROUND

The U.S. population is aging and projected to undergo an increasing number of general surgical procedures. However, recent trends in the frequency of major abdominal procedures in older adults are currently unknown as improvements in non-operative interventions may obviate the need for major surgery. Thus, we evaluated the trends of major abdominal surgical procedures in older adults in the United States.

METHODS

We performed a retrospective cohort study using the National Inpatient Sample from 2002 to 2014 with trend analysis using National Cancer Institute's Joinpoint Trend Analysis Software. We identified the average annual percent change (AAPC) in the yearly frequency of major abdominal surgical procedures in older adults (≥50 years of age).

RESULTS

Our cohort included a total of 3,951,947 survey-weighted discharges that included a major abdominal surgery in adults ≥50 years of age between 2002 and 2014. Of these discharges, 2,529,507 (64.0%) were for elective abdominal surgeries, 2,062,835 (52.0%) were for female patients, and mean (SD) age was 61.4 (15.9) years. The frequency of major abdominal procedures (elective and emergent) decreased for adults aged 65-74 (AAPC: -1.43, -1.75, -1.11, p < 0.0001), 75-84 (AAPC: -2.75, -3.33, -2.16, p < 0.001), and ≥85 (AAPC: -4.07, -4.67, -3.47, p < 0.0001). The AAPC for elective procedures decreased for older adults aged 75-84 (AAPC = -1.65; -2.44, -0.85: p = 0.0001) and >85 (AAPC = -3.53; -4.57, -2.48: p < 0.0001). All age groups showed decreases in emergent procedures in 50-64 (AAPC = -1.76, -2.00, -1.52, p < 0.0001), 65-74 (AAPC = -3.59, -4.03, -3.14, p < 0.0001), 75-84 (AAPC = -3.90, -4.34, -3.46, p < 0.0001), ≥85 (AAPC = -4.58, -4.98, -4.17, p < 0.0001) age groups.

CONCLUSIONS AND RELEVANCE

In this cohort of older adults, the frequency of emergent and elective major abdominal procedures in adults ≥65 years of age decreased with significant variation among individual procedure types. Future studies are needed to identify the generalizability of our findings to other surgical procedures.

NT-proBNP in young healthy adults undergoing non-cardiac surgery

OBJECTIVES

N-terminal pro-brain natriuretic peptide (NT-proBNP), a standard marker for diagnosis and treatment guidance of heart failure, has previously been investigated in high-risk patients undergoing cardiac and non-cardiac surgery. However, the kinetics of NT-proBNP in healthy patients undergoing non-cardiac surgery are unknown.

DESIGN & METHODS

A secondary analysis of a prospective cohort study was conducted. NT-proBNP plasma concentrations were measured preoperatively, 2-6 h, and 18-30 h after surgery in 120 patients, 18-35 years, undergoing elective non-cardiac surgery. Reasons for non-inclusion: history or symptoms of cardiac disease, kidney disease, pulmonary embolism, thrombosis, stroke, diabetes, head or chest trauma, pregnancy, incomplete panel of perioperative NT-proBNP plasma samples. Absolute and relative change of NT-proBNP plasma concentration were calculated. Changes between preoperative, 2-6 h, and 18-30 h (POD 1) NT-proBNP values, and of within-patient change in NT-proBNP were analyzed.

RESULTS

In 95 patients, NT-proBNP plasma concentrations (median [IQR]) were 8 [5-26] pg/mL at baseline, 17 [5-53] pg/mL 2-6 h, and 42 [11-86] pg/mL 18-30 h after surgery. Absolute and relative NT-proBNP increase after surgery was 32 [5-74] pg/mL and 196% [61 - 592%] compared to baseline. NT-proBNP elevation above the age- and sex-specific reference range was observed in 6/95 (6%) patients prior to surgery and in 39/95 (41%) patients after surgery.

CONCLUSIONS

Even after uncomplicated surgery and postoperative period, NT-proBNP concentrations markedly increase in otherwise healthy adult patients. The aetiology of postoperative NT-proBNP increase is currently unknown and may be multifactorial.

A phase 2 trial of inhaled nitrous oxide for treatment-resistant major depression

Nitrous oxide at 50% inhaled concentration has been shown to improve depressive symptoms in patients with treatment-resistant major depression (TRMD). Whether a lower concentration of 25% nitrous oxide provides similar efficacy and persistence of antidepressant effects while reducing the risk of adverse side effects is unknown. In this phase 2 clinical trial (NCT03283670), 24 patients with severe TRMD were randomly assigned in a crossover fashion to three treatments consisting of a single 1-hour inhalation with (i) 50% nitrous oxide, (ii) 25% nitrous oxide, or (iii) placebo (air/oxygen). The primary outcome was the change on the Hamilton Depression Rating Scale (HDRS-21). Whereas nitrous oxide significantly improved depressive symptoms versus placebo (P = 0.01), there was no difference between 25 and 50% nitrous oxide (P = 0.58). The estimated differences between 25% and placebo were -0.75 points on the HDRS-21 at 2 hours (P = 0.73), -1.41 points at 24 hours (P = 0.52), -4.35 points at week 1 (P = 0.05), and -5.19 points at week 2 (P = 0.02), and the estimated differences between 50% and placebo were -0.87 points at 2 hours (P = 0.69), -1.93 points at 24 hours (P = 0.37), -2.44 points at week 1 (P = 0.25), and -7.00 points at week 2 (P = 0.001). Adverse events declined substantially with dose (P < 0.001). These results suggest that 25% nitrous oxide has comparable efficacy to 50% nitrous oxide in improving TRMD but with a markedly lower rate of adverse effects.

Expert consensus on peri-operative myocardial injury screening in noncardiac surgery: A literature review

Peri-operative myocardial injury, detected by dynamic and elevated cardiac troponin (cTn) concentrations, is a common complication of noncardiac surgery that is strongly associated with 30-day mortality. Although active screening for peri-operative myocardial injury has been suggested in recent guidelines, clinical implementation remains tentative due to a lack of examples on how to tackle such an interdisciplinary project at a local level. Moreover, consensus on which assay and cTn cut-off values should be used has not yet been reached, and guidance on whom to screen is lacking. In this article, we aim to summarise local examples of successfully implemented cTn screening practices and review the current literature in order to provide information and suggestions for patient selection, organisation of a screening programme, caveats and a potential management pathway.

Systematic review and consensus definitions for the Standardized Endpoints in Perioperative Medicine (StEP) initiative: cardiovascular outcomes

BACKGROUND

Adverse cardiovascular events are a leading cause of perioperative morbidity and mortality. The definitions of perioperative cardiovascular adverse events are heterogeneous. As part of the international Standardized Endpoints in Perioperative Medicine initiative, this study aimed to find consensus amongst clinical trialists on a set of standardised and valid cardiovascular outcomes for use in future perioperative clinical trials.

METHODS

We identified currently used perioperative cardiovascular outcomes by a systematic review of the anaesthesia and perioperative medicine literature (PubMed/Ovid, Embase, and Cochrane Library). We performed a three-stage Delphi consensus-gaining process that involved 55 clinician researchers worldwide. Cardiovascular outcomes were first shortlisted and the most suitable definitions determined. These cardiovascular outcomes were then assessed for validity, reliability, feasibility, and clarity.

RESULTS

We identified 18 cardiovascular outcomes. Participation in the three Delphi rounds was 100% (n=19), 71% (n=55), and 89% (n=17), respectively. A final list of nine cardiovascular outcomes was elicited from the consensus: myocardial infarction, myocardial injury, cardiovascular death, non-fatal cardiac arrest, coronary revascularisation, major adverse cardiac events, pulmonary embolism, deep vein thrombosis, and atrial fibrillation. These nine cardiovascular outcomes were rated by the majority of experts as valid, reliable, feasible, and clearly defined.

CONCLUSIONS

These nine consensus cardiovascular outcomes can be confidently used as endpoints in clinical trials designed to evaluate perioperative interventions with the goal of improving perioperative outcomes.

Morbidity and Mortality After Acute Myocardial Infarction After Elective Major Noncardiac Surgery

OBJECTIVES

To develop parsimonious models of in-hospital mortality and morbidity risk after perioperative acute myocardial infarction (AMI).

DESIGN

Retrospective data analysis.

SETTING

National Inpatient Sample (2008-2013), a 20% sample of all non-federal in-patient hospitalizations in the United States.

PARTICIPANTS

Patients 45 years or older who experienced perioperative AMI during elective admission for noncardiac surgery.

INTERVENTIONS

The study used a mixed principal components analysis and multivariate logistic regression to identify risk factors for in-hospital mortality after perioperative AMI. A model incorporating only preoperative risk factors, defined by the Revised Cardiac Risk Index (RCRI), was compared with a "full risk factor" model, incorporating a large set of preoperative AMI risk factors. The risk of post-AMI disposition to an intermediate care or skilled nursing facility, a marker of functional impairment, then was evaluated.

MEASUREMENTS AND MAIN RESULTS

In the present study, 15,574 cases of AMI after elective noncardiac surgery were identified (0.42%, corresponding with 78,122 cases nationally), with a 12.4% in-hospital mortality rate. The "RCRI-only" model was the best-fit model of post-AMI in-hospital mortality risk, without loss of predictive accuracy compared with the "full risk factor" model (area under the receiver operator characteristic curve 0.80, 95% confidence interval [CI] [0.77-0.82] v area under the receiver operator characteristic curve 0.81, 95% CI [0.77-0.83], respectively). Post-AMI mortality risk was the highest for perioperative complications, including sepsis (odds ratio 4.95, 95% CI [4.32-5.67]). Conversely, functional impairment was best predicted by the "full-risk factor" model and depended strongly on chronic preoperative comorbidities.

CONCLUSIONS

The RCRI provides a simple but adequate model of preoperative risk factors for in-hospital mortality after perioperative AMI.

Frequency and Outcomes of Preoperative Stress Testing in Total Hip and Knee Arthroplasty from 2004 to 2017

Importance

Cardiac stress testing is often performed prior to noncardiac surgery, although trends in use of preoperative stress testing and the effect of testing on cardiovascular outcomes are currently unknown.

Objective

To describe temporal trends and outcomes of preoperative cardiac stress testing from 2004 to 2017.

Design, Setting, and Participants

Cross-sectional study of patients undergoing elective total hip or total knee arthroplasty from 2004 to 2017. Trend analysis was conducted using Joinpoint and generalized estimating equation regression. The study searched IBM MarketScan Research Databases inpatient and outpatient health care claims for private insurers including supplemental Medicare coverage and included patients with a claim indicating an elective total hip or total knee arthroplasty from January 1, 2004, to December 31, 2017.

Exposures

Elective total hip or knee arthroplasty.

Main Outcomes and Measures

Trend in yearly frequency of preoperative cardiac stress testing.

Results

The study cohort consisted of 801 396 elective total hip (27.9%; n = 246 168 of 801 396) and total knee (72.1%; 555 228 of 801 396) arthroplasty procedures, with a median age of 62 years (interquartile range, 57-70 years) and 58.1% women (n = 465 545 of 801 396). The overall rate of stress testing during the study period was 10.4% (n = 83 307 of 801 396). The rate of stress tests increased 0.65% (95% CI, 0.09-1.21; P = .03) annually from quarter (Q) 1 of 2004 until Q2 of 2006. A joinpoint was identified at Q3 of 2006 (95% CI, 2005 Q4 to 2007 Q4) when preoperative stress test use decreased by -0.71% (95% CI, -0.79% to 0.63%; P < .001) annually. A second joinpoint was identified at the Q4 of 2013 (95% CI, 2011 Q3 to 2015 Q3), when the decline in stress testing rates slowed to -0.40% (95% CI, -0.57% to -0.24%; P < .001) annually. The overall rate of myocardial infarction and cardiac arrest was 0.24% (n = 1677 of 686 067). Rates of myocardial infraction and cardiac arrest were not different in patients with at least 1 Revised Cardiac Risk Index condition who received a preoperative stress test and those who did not (0.60%; n = 221 of 36 554 vs 0.57%; n = 694 of 122 466; P = .51).

Conclusions and Relevance

The frequency of preoperative stress testing declined annually from 2006 through 2017. Among patients with at least 1 Revised Cardiac Risk Index condition, no difference was observed in cardiovascular outcomes between patients who did and did not undergo preoperative testing.

Generalisability of randomised trials evaluating perioperative β-blocker therapy in noncardiac surgery

BACKGROUND

The limited applicability of evidence from RCTs in real-word practice is considered a potential bottleneck for evidence-based practice but rarely systematically assessed. Using our failure to recruit patients into a perioperative beta-blocker trial, we set out to analyse the restrictiveness and generalisability of trial eligibility criteria in a real-world cohort.

METHODS

We prospectively included adult patients (≥18 yr) scheduled for elective noncardiac surgery at an academic tertiary care facility who were screened for inclusion in a planned perioperative beta-blocker RCT, which was terminated owing to recruitment failure. The primary outcome was the proportion of screened patients who matched the eligibility criteria of 36 published RCTs included in a large Cochrane meta-analysis on perioperative beta-blocker therapy. The pragmatic/explanatory level of each RCT was assessed using the PRagmatic-Explanatory Continuum Indicator Summary 2 (PRECIS-2) score, which ranges from 9 points (indicating a very explanatory study) to 45 points (indicating a very pragmatic study).

RESULTS

A total of 2241 patients (54% female, n=1215; 52 [standard deviation, 20] yr) were included for the assessment of trial eligibility between October 2015 and January 2016. Only a small proportion of patients matched the inclusion and exclusion criteria for each of the 36 RCTs, ranging from 53% to 0%. The average proportion of patients who did match the eligibility criteria of all 36 RCTs was 6.5% (n=145; 95% confidence interval, 6.3-6.6). A higher PRECIS-2 score was associated with a higher proportion of matching patients (P<0.001).

CONCLUSIONS

Trial eligibility criteria in perioperative beta-blocker therapy trials are overly restrictive and not generalisable to a real-world surgical population.

CLINICAL TRIAL REGISTRATION

EudraCT#: 2015-002366-23.

High-Sensitivity Cardiac Troponin After Cardiac Stress Test: A Systematic Review and Meta-Analysis

Background The recent introduction of high-sensitivity cardiac troponin (hs-cTn) assays has allowed clinicians to measure hs-cTn before and after cardiac stress testing, but the hs-cTn release pattern and potential utility in identifying inducible myocardial ischemia are unclear. We thus conducted a systematic review and meta-analysis to improve our understanding of hs-cTn release associated with exercise and pharmacological stress testing. Methods and Results Studies published between January 2008 and July 2016 that reported hs-cTn change values (high-sensitivity cardiac troponin T [hs-cTnT] or high-sensitivity cardiac troponin I [hs-cTnI]) in relation to cardiac stress testing were searched and reviewed by 2 independent screeners. Primary outcomes were pooled estimates of absolute and relative hs-cTn changes after cardiac stress test, stratified by the presence of inducible myocardial ischemia. This meta-analysis included 11 studies (n=2432 patients). After exercise stress testing, hs-cTnT increased by 0.5 ng/L or 11% (6 studies, n=406) and hs-cTnI by 2.4 ng/L or 41% (4 studies, n=365) in patients with inducible myocardial ischemia versus hs-cTnT by 1.1 ng/L or 18% (8 studies, n=629; P=0.29) and hs-cTnI by 1.8 ng/L or 72% (4 studies, n=831; P=0.61) in patients who did not develop inducible myocardial ischemia. After pharmacological stress test, hs-cTnT changed by -0.1 ng/L or -0.4% (6 studies, n=251) and hs-cTnI by 2.4 ng/L or 32% (2 studies, n=108) in patients with inducible myocardial ischemia versus hs-cTnT by 0.7 ng/L or 11% (5 studies, n=443, P=0.44) and hs-cTnI by 1.7 ng/L or 38% (2 studies, n=116; P=0.62) in patients who did not develop inducible myocardial ischemia. Conclusions hs-cTn rising patterns after exercise and pharmacological stress testing appear inconsistent and comparably small, and do not appear to be correlated with inducible myocardial ischemia.

Ketamine and nitrous oxide: The evolution of NMDA receptor antagonists as antidepressant agents

N-methyl-d-aspartate receptor (NMDAR) antagonists, including ketamine and nitrous oxide, are currently intensely studied as rapid-acting antidepressant agents. Interestingly, both of these compounds are also drugs of abuse. Intravenous ketamine, a dissociative anesthetic that induces complex downstream effects via NMDARs, rapidly reduces depressive and suicidal symptoms in treatment-resistant depression (TRD), as demonstrated by several trials. Recently, the United States Food and Drug Administration (FDA) approved an intranasal version of ketamine (esketamine) for TRD. The United States Drug Enforcement Agency (DEA) lists ketamine as a Class III scheduled drug (moderate-low potential for physical and psychological abuse). The FDA has established a Risk Evaluation and Management Strategy (REMS) program to ensure proper drug storage, handling, dispensing, and monitoring intranasal esketamine to minimize misuse/abuse opportunities. Nitrous Oxide is a colorless, odorless, gas that has been in medical use for over 150 years. The mechanisms of action of nitrous oxide are not fully understood; however, it is known to act as a non-competitive inhibitor of NMDA-type glutamate receptors. Currently, nitrous oxide is used for inhalational general anesthesia and analgesia for short procedures. Inhaled nitrous oxide is also used recreationally, primarily by teens and young adults, but is not believed to have strong addiction potential. In contrast to ketamine, nitrous oxide is not a controlled substance and can be legally purchased without a prescription. A recent double-blind, prospective, cross-over study demonstrated that nitrous oxide reduced depressive symptoms in a group of severely ill TRD patients. Though this is a promising initial study, further investigation is needed.

Effect of Nitrous Oxide as a Treatment for Subjective, Idiopathic, Nonpulsatile Bothersome Tinnitus: A Randomized Clinical Trial

Importance

The tinnitus research literature suggests that N-methyl-d-aspartate (NMDA) receptor antagonists may be useful in reducing tinnitus. Nitrous oxide, a member of the NMDA receptor antagonist class, is a widely used general anesthetic and sedative with a proven safety record.

Objective

To investigate whether nitrous oxide can reduce bothersome tinnitus.

Design, Setting, and Participants

Randomized, placebo-controlled crossover trial conducted between October 15, 2016, and June 22, 2017. Participants attended 2 interventional sessions separated by at least 14 days and were randomized to receive either placebo first or nitrous oxide first. Participants were followed up through completion of the second arm of the study. The setting was a clinical research unit at an academic medical center. Adults aged 18 to 65 years with subjective, idiopathic, nonpulsatile bothersome tinnitus of 6 months' duration or longer were recruited from 2 clinical research databases. Seventy-one individuals were screened, of whom 40 were enrolled. Of those enrolled, 37 participants completed all components of the study.

Interventions

The placebo session consisted of 50% nitrogen and 50% oxygen inhaled for 40 minutes, and the treatment session consisted of 50% nitrous oxide and 50% oxygen inhaled for 40 minutes.

Main Outcomes and Measures

Tinnitus was assessed before and after intervention, with the change in the Tinnitus Functional Index (TFI) as the primary outcome measure. Secondary outcome measures included the Patients' Global Impression of Change score and the change in the Global Bothersome Scale score.

Results

Among 40 participants in this intent-to-treat randomized clinical trial with 20 participants randomly assigned to each group, the mean (SD) age of participants was 52.9 (11.1) years, with equal numbers of male and female participants. The TFI after intervention was a mean (SD) of 1.8 (8.8) points lower than before intervention in the placebo arm and a mean (SD) of 2.5 (11.0) points lower than before intervention in the nitrous oxide arm. The within-participant mean difference in the change in the TFI of the placebo arm compared with the nitrous oxide arm was -1.1 points (95% CI, -5.6 to 3.4 points). The difference between the placebo and nitrous oxide arms was neither clinically meaningful nor statistically significant.

Conclusions and Relevance

Nitrous oxide was no more effective than placebo for the treatment of subjective, idiopathic tinnitus.

Trial Registration

ClinicalTrials.gov identifier: NCT03365011.

European Society of Anaesthesiology Task Force on Nitrous Oxide: a narrative review of its role in clinical practice

Nitrous oxide (N₂O) is one of the oldest drugs still in use in medicine. Despite its superior pharmacokinetic properties, controversy remains over its continued use in clinical practice, reflecting in part significant improvements in the pharmacology of other anaesthetic agents and developing awareness of its shortcomings. This narrative review describes current knowledge regarding the clinical use of N₂O based on a systematic and critical analysis of the available scientific literature. The pharmacological properties of N₂O are reviewed in detail along with current evidence for the indications and contraindications of this drug in specific settings, both in perioperative care and in procedural sedation. Novel potential applications for N₂O for the prevention or treatment of chronic pain and depression are also discussed. In view of the available evidence, we recommend that the supply of N₂O in hospitals be maintained while encouraging its economic delivery using modern low flow delivery systems. Future research into its potential novel applications in prevention or treatment of chronic conditions should be pursued to better identify its role place in the developing era of precision medicine.

Etiology of Acute Coronary Syndrome after Noncardiac Surgery

BACKGROUND

The objective of this investigation was to determine the etiology of perioperative acute coronary syndrome with a particular emphasis on thrombosis versus demand ischemia.

METHODS

In this retrospective cohort study, adult patients were identified who underwent coronary angiography for acute coronary syndrome within 30 days of noncardiac surgery at a major tertiary hospital between January 2008 and July 2015. Angiograms were independently reviewed by two interventional cardiologists who were blinded to clinical data and outcomes. Acute coronary syndrome was classified as ST-elevation myocardial infarction, non-ST-elevation myocardial infarction, or unstable angina; myocardial infarctions were adjudicated as type 1 (plaque rupture), type 2 (demand ischemia), or type 4b (stent thrombosis).

RESULTS

Among 215,077 patients screened, 146 patients were identified who developed acute coronary syndrome: 117 were classified as non-ST-elevation myocardial infarction (80.1%); 21 (14.4%) were classified as ST-elevation myocardial infarction, and 8 (5.5%) were classified as unstable angina. After coronary angiography, most events were adjudicated as demand ischemia (type 2 myocardial infarction, n = 106, 72.6%) compared to acute coronary thrombosis (type 1 myocardial infarction, n = 37, 25.3%) and stent thrombosis (type 4B, n = 3, 2.1%). Absent or only mild, nonobstructive coronary artery disease was found in 39 patients (26.7%). In 14 patients (9.6%), acute coronary syndrome was likely due to stress-induced cardiomyopathy. Aggregate 30-day and 1-yr mortality rates were 7 and 14%, respectively.

CONCLUSIONS

The dominant mechanism of perioperative acute coronary syndrome in our cohort was demand ischemia. A subset of patients had no evidence of obstructive coronary artery disease, but findings were consistent with stress-induced cardiomyopathy.

High-sensitivity cardiac troponin T in young, healthy adults undergoing non-cardiac surgery

BACKGROUND

It is unclear if isolated postoperative cardiac-troponin elevation, often referred to as myocardial injury, represents a pathological event, as control studies in otherwise healthy adults are lacking.

METHODS

In this single-centre prospective observational cohort study, serial high-sensitivity cardiac troponin T (hscTnT) plasma concentrations were obtained from young, healthy adults undergoing elective orthopaedic surgery at three time points: before operation, 2-6 h, and 18-30 h after surgery. End points were hscTnT increases after surgery: ≥20% (exceeding analytical variability), ≥50% (exceeding short-term biological variability), and ≥85% (exceeding long-term biological variability). The secondary end point was myocardial injury, defined as new postoperative hscTnT elevation >99th % upper reference limit (URL) (women >10 ng litre^-1; men >15 ng litre^-1).

RESULTS

Amongst the study population (n=95), no hscTnT increase ≥20% was detected in 68 patients (73%). A hscTnT increase between 20% and 49% was observed in 17 patients (18%), 50-84% in seven patients (7%), and ≥85% in three patients (3%). Twenty patients (21%) had an absolute ΔhscTnT between 0 and 2 ng litre^-1, 12 patients (13%) between 2 and 4 ng litre^-1, three patients between 4 and 6 ng litre^-1, and one patient (1%) between 6 and 8 ng litre^-1. Myocardial injury (new hscTnT elevation >99th%) was diagnosed in one patient (1%). The median hscTnT concentrations did not increase after operation, and were 4 (3.9-5, inter-quartile range) ng litre^-1 at baseline, 4 (3.9-5) ng litre^-1 at 2-6 h after surgery, and 4 (3.9-5) ng litre^-1 on postoperative day 1.

CONCLUSIONS

One in four young adult patients without known cardiovascular disease developed a postoperative hscTnT increase, but without exceeding the 99th% URL and without evidence of myocardial ischaemia. These results may have important ramifications for the concept of postoperative myocardial injury, as they suggest that, in some patients, postoperative cardiac-troponin increases may be the result of a normal physiological process in the surgical setting.

CLINICAL TRIAL REGISTRATION

NCT 02394288.

High-Sensitivity Cardiac Troponin T Improves the Diagnosis of Perioperative MI

BACKGROUND

The diagnosis of myocardial infarction (MI) after noncardiac surgery has traditionally relied on using relatively insensitive contemporary cardiac troponin (cTn) assays. We hypothesized that using a recently introduced novel high-sensitivity cTnT (hscTnT) assay would increase the detection rate of perioperative MI.

METHODS

In this ancillary study of the Vitamins in Nitrous Oxide trial, readjudicated incidence rates of myocardial injury (new isolated cTn elevation) and MI were compared when diagnosed by contemporary cTnI versus hscTnT. We probed various relative (eg, >50%) or absolute (eg, +5 ng/L) hscTnT change metrics. Inclusion criteria for this ancillary study were the presence of a baseline and at least 1 postoperative hscTnT value.

RESULTS

Among 605 patients, 70 patients (12%) had electrocardiogram changes consistent with myocardial ischemia; 82 patients (14%) had myocardial injury diagnosed by contemporary cTnI, 31 (5.1%) of which had an adjudicated MI. After readjudication, 67 patients (11%) were diagnosed with MI when using hscTnT, a 2-fold increase. Incidence rates of postoperative myocardial injury ranged from 12% (n = 73) to 65% (n = 393) depending on the hscTnT metric used. Incidence rates of MI using various hscTnT change metrics and the presence of ischemic electrocardiogram changes, but without event adjudication, ranged from 3.6% (n = 22) to 12% (n = 74), a >3-fold difference. New postoperative hscTnT elevation, either by absolute or relative hscTnT change metric, was associated with an up to 5-fold increase in 6-month mortality.

CONCLUSIONS

The use of hscTnT compared to contemporary cTnI increases the detection rate of perioperative MI by a factor of 2. Using different absolute or relative hscTnT change metrics may lead to under- or overdiagnosis of perioperative MI.

Improving Prediction of Postoperative Myocardial Infarction With High-Sensitivity Cardiac Troponin T and NT-proBNP

BACKGROUND

This study sought to determine whether preoperatively measured high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) improve cardiac risk prediction in patients undergoing major noncardiac surgery compared with the standard risk indices.

METHODS

In this ancillary study to the Vitamins in Nitrous Oxide trial, patients were included who had preoperative hs-cTnT and NT-proBNP measured (n = 572). Study outcome was the incidence of postoperative myocardial infarction (MI) within the first 3 postoperative days. hs-cTnT was considered elevated if >14 ng/L and NT-proBNP if >300 ng/L. Additional cutoff values were investigated on the basis of receiver operating characteristic statistics. Biomarker risk prediction was compared with Lee's Revised Cardiac Risk Index (RCRI) with the use of standard methods and net reclassification index.

RESULTS

The addition of hs-cTnT (>14 ng/L) and NT-proBNP (>300 ng/L) to RCRI significantly improved the prediction of postoperative MI (event rate 30/572 [5.2%], Area under the receiver operating characteristic curve increased from 0.590 to 0.716 with a 0.66 net reclassification index [95% confidence interval 0.32-0.99], P < .001). The use of 108 ng/L as a cutoff for NT-proBNP improved sensitivity compared with 300 ng/L (0.87 vs 0.53). Sensitivity, specificity, positive, and negative predictive value for hs-cTnT were 0.70, 0.60, 0.09, and 0.97 and for NT-proBNP were 0.53, 0.68, 0.08, and 0.96.

CONCLUSIONS

The addition of cardiac biomarkers hs-cTnT and NT-proBNP to RCRI improves the prediction of adverse cardiac events in the immediate postoperative period after major noncardiac surgery. The high negative predictive value of preoperative hs-cTnT and NT-proBNP suggest usefulness as a "rule-out" test to confirm low risk of postoperative MI.

The hematological effects of nitrous oxide anesthesia in pediatric patients

BACKGROUND

Prolonged administration of nitrous oxide causes an increase in plasma homocysteine in children via vitamin B12 inactivation. However, it is unclear whether nitrous oxide doses used in clinical practice cause adverse hematological effects in pediatric patients.

METHODS

This retrospective study included 54 pediatric patients undergoing elective spinal surgery: 41 received nitrous oxide throughout anesthesia (maintenance group), 9 received nitrous oxide for induction and/or emergence (induction/emergence group), and 4 did not receive nitrous oxide (nitrous oxide-free group). Complete blood counts obtained before and up to 4 days after surgery were assessed for anemia, macrocytosis/microcytosis, anisocytosis, hyperchromatosis/hypochromatosis, thrombocytopenia, and leukopenia. The change (Δ) from preoperative to the highest postoperative value was calculated for mean corpuscular volume (MCV) and red cell distribution width (RDW).

RESULTS

No pancytopenia was present in any patient after surgery. All patients had postoperative anemia, and none had macrocytosis. Postoperative MCV (mean [99% confidence interval]) peaked at 86 fL (85-88 fL), 85 fL (81-89 fL), and 88 fL (80-96 fL) and postoperative RDW at 13.2% (12.8-13.5%), 13.3% (12.7-13.8%), and 13.0% (11.4-14.6%) for the maintenance group, the induction/emergence group, and the nitrous oxide-free group. Two patients in the maintenance group (5%) developed anisocytosis (RDW >14.6%), but none in the induction/emergence group or in the nitrous oxide-free group (P = 0.43). Both ΔMCV (P = 0.52) and ΔRDW (P = 0.16) were similar across all groups.

CONCLUSIONS

Nitrous oxide exposure for up to 8 hours is not associated with megaloblastic anemia in pediatric patients undergoing major spinal surgery.

Nitrous Oxide for Treatment-Resistant Major Depression: A Proof-of-Concept Trial

BACKGROUND

N-methyl-D-aspartate receptor antagonists, such as ketamine, have rapid antidepressant effects in patients with treatment-resistant depression (TRD). We hypothesized that nitrous oxide, an inhalational general anesthetic and N-methyl-D-aspartate receptor antagonist, may also be a rapidly acting treatment for TRD.

METHODS

In this blinded, placebo-controlled crossover trial, 20 patients with TRD were randomly assigned to 1-hour inhalation of 50% nitrous oxide/50% oxygen or 50% nitrogen/50% oxygen (placebo control). The primary endpoint was the change on the 21-item Hamilton Depression Rating Scale (HDRS-21) 24 hours after treatment.

RESULTS

Mean duration of nitrous oxide treatment was 55.6 ± 2.5 (SD) min at a median inspiratory concentration of 44% (interquartile range, 37%-45%). In two patients, nitrous oxide treatment was briefly interrupted, and the treatment was discontinued in three patients. Depressive symptoms improved significantly at 2 hours and 24 hours after receiving nitrous oxide compared with placebo (mean HDRS-21 difference at 2 hours, -4.8 points, 95% confidence interval [CI], -1.8 to -7.8 points, p = .002; at 24 hours, -5.5 points, 95% CI, -2.5 to -8.5 points, p < .001; comparison between nitrous oxide and placebo, p < .001). Four patients (20%) had treatment response (reduction ≥50% on HDRS-21) and three patients (15%) had a full remission (HDRS-21 ≤ 7 points) after nitrous oxide compared with one patient (5%) and none after placebo (odds ratio for response, 4.0, 95% CI, .45-35.79; OR for remission, 3.0, 95% CI, .31-28.8). No serious adverse events occurred; all adverse events were brief and of mild to moderate severity.

CONCLUSIONS

This proof-of-concept trial demonstrated that nitrous oxide has rapid and marked antidepressant effects in patients with TRD.

Prognostic capabilities of coronary computed tomographic angiography before non-cardiac surgery: prospective cohort study

OBJECTIVES

To determine if coronary computed tomographic angiography enhances prediction of perioperative risk in patients before non-cardiac surgery and to assess the preoperative coronary anatomy in patients who experience a myocardial infarction after non-cardiac surgery.

DESIGN

Prospective cohort study.

SETTING

12 centers in eight countries.

PARTICIPANTS

955 patients with, or at risk of, atherosclerotic disease who underwent non-cardiac surgery.

INTERVENTIONS

Coronary computed tomographic angiography was performed preoperatively; clinicians were blinded to the results unless left main disease was suspected. Results were classified as normal, non-obstructive (<50% stenosis), obstructive (one or two vessels with ≥ 50% stenosis), or extensive obstructive (≥ 50% stenosis in two vessels including the proximal left anterior descending artery, three vessels, or left main).

MAIN OUTCOME MEASURE

Composite of cardiovascular death and non-fatal myocardial infarction within 30 days after surgery (primary outcome). This was the dependent variable in Cox regression. The independent variables were scores on the revised cardiac risk index and findings on coronary computed tomographic angiography.

RESULTS

The primary outcome occurred in 74 patients (8%). The model that included both scores on the revised cardiac risk index and findings on coronary computed tomographic angiography showed that coronary computed tomographic angiography provided independent prognostic information (P=0.014; C index=0.66). The adjusted hazard ratios were 1.51 (95% confidence interval 0.45 to 5.10) for non-obstructive disease; 2.05 (0.62 to 6.74) for obstructive disease; and 3.76 (1.12 to 12.62) for extensive obstructive disease. For the model with coronary computed tomographic angiography compared with the model based on the revised cardiac risk index alone, with 30 day risk categories of <5%, 5-15%, and >15% for the primary outcome, the results of risk reclassification indicate that in a sample of 1000 patients that coronary computed tomographic angiography would have resulted appropriately in 17 net patients receiving a higher risk estimation among the 77 patients who would have experienced the primary outcome (P<0.001). Coronary computed tomographic angiography, however, would have resulted inappropriately in 98 net patients receiving a higher risk estimation, among the 923 patients who would not have experienced the primary outcome (P<0.001). Among patients who had a perioperative myocardial infarction, preoperative coronary anatomy showed extensive obstructive disease in 31% (22/71), obstructive disease in 41% (29/71), non-obstructive disease in 24% (17/71), and normal findings in 4% (3/71).

CONCLUSIONS

Though findings on coronary computed tomographic angiography can improve estimation of risk for patients who will experience perioperative cardiovascular death or myocardial infarction, findings are more than five times as likely to lead to an inappropriate overestimation of risk among patients who will not experience these outcomes. Perioperative myocardial infarction occurs across the spectrum of coronary artery disease, suggesting that there could be several pathophysiologic mechanisms.

Treatment-Resistant Major Depression: Rationale for NMDA Receptors as Targets and Nitrous Oxide as Therapy

Major depressive disorder (MDD) remains a huge personal and societal encumbrance. Particularly burdensome is a virulent subtype of MDD, treatment resistant major depression (TMRD), which afflicts 15-30% of MDD patients. There has been recent interest in N-methyl-d-aspartate receptors (NMDARs) as targets for treatment of MDD and perhaps TMRD. To date, most pre-clinical and clinical studies have focused on ketamine, although psychotomimetic and other side effects may limit ketamine's utility. These considerations prompted a recent promising pilot clinical trial of nitrous oxide, an NMDAR antagonist that acts through a mechanism distinct from that of ketamine, in patients with severe TRMD. In this paper, we review the clinical picture of TRMD as a subtype of MDD, the evolution of ketamine as a fast-acting antidepressant, and clinical and basic science studies supporting the possible use of nitrous oxide as a rapid antidepressant.

The potential impact of wrong TBSA estimations on fluid resuscitation in patients suffering from burns: things to keep in mind

INTRODUCTION

Accurate estimation of burn size is of critical importance, as it is incorporated in every resuscitation formula. The aim of this study was to investigate total burn surface area (TBSA) accuracy among burn specialists, evaluate the potential impact of incorrect evaluation on variations of resultant fluid resuscitation volumes and to discuss future possibilities to estimate or measure TBSA more precisely.

METHODS

In a poll during two international burn meetings in 2010 and 2011 demonstrating three pictures of patients with different burn wound patterns and sizes we asked participants to estimate the total surface area burned in percentages. We then calculated resultant fluid volume differences based on established resuscitation formulas.

RESULTS

In the polled 80 participants, the estimations for three patients demonstrated the following differences (DIF=MAX-MIN): for patient 1, 2 and 3 they were 22.5 (25-2.5), 16.5 (20-3.5) and 31.5 (40-8.5) %TBSA, respectively. Based on these differences we calculated the volume differences for patients 1,2 and 3, which were 1080ml (Cincinnati Formula), 5280ml (Parkland Formula) and 2016ml (Cincinnati Formula), respectively.

CONCLUSIONS

The analysis showed high deviations of total body surface area among participants, also resulting in large variations of initial fluid resuscitation volumes. One option to address estimation variances is to perform more accurate assessments; also incorporating new technologies aiding to improve the quality of body surface estimations and related decisions.

High-sensitivity cardiac troponin T in prediction and diagnosis of myocardial infarction and long-term mortality after noncardiac surgery

BACKGROUND

Perioperative myocardial infarction (MI) is a serious complication after noncardiac surgery. We hypothesized that preoperative cardiac troponin T detected with a novel high-sensitivity (hs-cTnT) assay will identify patients at risk for acute MI and long-term mortality after major noncardiac surgery.

METHODS

This was a prospective cohort study within the VINO trial (n = 608). Patients had been diagnosed with or had multiple risk factors for coronary artery disease and underwent major noncardiac surgery. Cardiac troponin I (contemporary assay) and troponin T (high-sensitivity assay) and 12-lead electrocardiograms were obtained before and immediately after surgery and on postoperative days 1, 2, and 3.

RESULTS

At baseline before surgery, 599 patients (98.5%) had a detectable hs-cTnT concentration, and 247 (41%) were >14 ng/L (99th percentile). After surgery, 497 patients (82%) had a rise in hs-cTnT (median change in hs-cTnT +2.7 ng/L [interquartile range 0.7-6.8]). During the first 3 postoperative days, there were 9 patients (2.5%) with a preoperative hs-cTnT <14 ng/L with acute MI, compared with 21 patients (8.6%) with a preoperative hs-cTnT >14 ng/L (odds ratio 3.67, 95% CI 1.65-8.15). During long-term follow-up, 80 deaths occurred. The 3-year mortality rate was 11% in patients with a preoperative hs-cTnT concentration <14 ng/L compared with 25% in patients with a preoperative hs-cTnT >14 ng/L (adjusted hazard ratio 2.17, 95% CI 1.19-3.96).

CONCLUSIONS

In this cohort of high-risk patients, preoperative hs-cTnT concentrations were significantly associated with postoperative MI and long-term mortality after noncardiac surgery.

Perioperative torsade de pointes: a systematic review of published case reports

BACKGROUND

Torsade de pointes is a rare but potentially fatal arrhythmia. More than 40 cases of perioperative torsade de pointes have been reported in the literature; however, the current evidence regarding this complication is very limited. To improve our understanding, we performed a systematic review and meta-analysis of all published case reports of perioperative torsade de pointes.

METHODS

MEDLINE was systematically searched for cases of perioperative torsade de pointes. We included patients of all age groups and cases that occurred from the immediate preoperative period to the third postoperative day. Patient and case characteristics as well as QT interval data were extracted.

RESULTS

Forty-six cases of perioperative torsade de pointes were identified; 29 occurred in women (67%), and 2 episodes were fatal (case fatality rate: 4%). Craniotomies and cardiac surgery accounted for 40% of all cases. Preceding events identified by the authors were hypokalemia (12/46, 26%; 99% confidence interval [CI], 9%-43%) and bradycardia (7/46, 15%; 99% CI, 2%-28%). Drugs were implicated in approximately one third of the events (14/46, 30%; 99% CI, 13%-48%). The mean corrected QT (QTc) at baseline was 457 ± 67 milliseconds (minimum 320 milliseconds; maximum 647 milliseconds; data available in 27/46 patients). At the time of the event, the mean QTc increased to 575 ± 77 milliseconds (minimum 413 milliseconds; maximum 766 milliseconds; data available in 33/46 patients). On average, QTc increased by +118 milliseconds (99% CI, 70-166 milliseconds; P < 0.001) between baseline and after the torsade de pointes event. All patients, except for 2, had a substantial prolongation of their QTc interval at the time of the event.

CONCLUSIONS

This systematic review identified several common risk factors for perioperative torsade de pointes. Given the nearly uniform presence of a substantial QTc interval prolongation at the time of a torsade de pointes episode, increased vigilance for perioperative QTc interval prolongation may be warranted.

A meta-analysis of CYP2D6 metabolizer phenotype and metoprolol pharmacokinetics

Metoprolol, a commonly prescribed beta-blocker, is primarily metabolized by cytochrome P450 2D6 (CYP2D6), an enzyme with substantial genetic heterogeneity. Several smaller studies have shown that metoprolol pharmacokinetics is influenced by CYP2D6 genotype and metabolizer phenotype. To increase robustness of metoprolol pharmacokinetic estimates, a systematic review and meta-analysis of pharmacokinetic studies that administered a single oral dose of immediate release metoprolol was performed. Pooled analysis (n= 264) demonstrated differences in peak plasma metoprolol concentration, area under the concentration-time curve, elimination half-life, and apparent oral clearance that were 2.3-, 4.9-, 2.3-, and 5.9-fold between extensive and poor metabolizers, respectively, and 5.3-, 13-, 2.6-, and 15-fold between ultra-rapid and poor metabolizers (all p<0.001). Enantiomer-specific analysis revealed genotype-dependent enantio-selective metabolism, with nearly 40% greater R- vs S-metoprolol metabolism in ultra-rapid and extensive metabolizers. This study demonstrates a marked effect of CYP2D6 metabolizer phenotype on metoprolol pharmacokinetics and confirms enantiomer specific metabolism of metoprolol.

Pediatric trauma in the Austrian Alps: the epidemiology of sport-related injuries in helicopter emergency medical service

BACKGROUND/PURPOSE

We aimed to examine the epidemiological characteristics and injury patterns of pediatric trauma in helicopter emergency medical service (HEMS) caused by sports/outdoor activities in alpine environment.

METHODS

This retrospective cohort study analyzed 912 primary HEMS missions for pediatric trauma (0-14 years of age) in Austrian Alps between 1 January 2006 and 30 June 2007. Children were stratified by age into toddlers (3-5 years), children in early (6-9 years), and late school age (10-14 years).

RESULTS

The majority of pediatric sports-related trauma in alpine environment was caused by skiing (82.1%; n=749). Pediatric patients were predominately in late school age and boys (72.8%, n=664 and 61.0%, n=556, respectively) and a minority (16.0%, n=146) was severely injured. Overall, fracture (47.0%, n=429), contusion (17.9%, n=163), and traumatic brain injury (17.0%, n=155) were the most common prehospital diagnoses. The most frequent pattern of injury was related to the head/face and spine (36.3%, n=331).

CONCLUSIONS

The knowledge about epidemiological characteristics of HEMS use for injured children in alpine environment may be essential for training requirements of HEMS crews and operational considerations of HEMS providers. The incidence of head and spinal injuries requires support for initiatives to promote helmet wear and appropriate risk behavior amongst skiers and snowboarders.

The epidemiology of amputation injuries in the Austrian helicopter emergency medical service: a retrospective, nationwide cohort study

PURPOSE

Data on the epidemiological characteristics of traumatic amputations in prehospital emergency care, especially in the context of air rescue, are scarce. Therefore, we aimed to describe the epidemiology of total and subtotal amputation injuries encountered by the OEAMTC helicopter emergency medical service (HEMS) in Austria, based on an almost nationwide sample.

METHODS

We retrospectively reviewed all HEMS rescue missions flown for amputation injuries in 2009. Only primary missions were analyzed.

RESULTS

In total, 149 out of 16,100 (0.9 %) primary HEMS rescue missions were for patients suffering from amputation injuries. Among these, HEMS physicians diagnosed 63.3 % (n = 94) total and 36.9 % (n = 55) subtotal amputations, with both groups showing a predominance of male victims (male:female ratios were 8:1 and 6:1, respectively).The highest rate occurred among adults between 45 and 64 years of age (35.6 %, n = 53). The most common causes were working with a circular saw (28.9 %, n = 43) and processing wood (16.8 %, n = 25). The majority of the cases included digital amputation injuries (77.2 %, n = 115) that were mainly related to the index finger (36.2 %, n = 54). One hundred forty patients (94.0 %) showed a total GCS of more than 12. Amputations were most prevalent in rural areas (84.6 %, n = 126) and between Thursday and Saturday (55.0 %, n = 82). The replantation rate after primary air transport was low (28 %).

CONCLUSIONS

In the HEMS, amputation injuries are infrequent and mostly not life-threatening. However, HEMS crews need to maintain their focus on providing sufficient and fast primary care while facilitating rapid transport to a specialized hospital. The knowledge of the epidemiological characteristics of amputation injuries encountered in the HEMS gained in this study may be useful for educational and operational purposes.

Association between postoperative troponin levels and 30-day mortality among patients undergoing noncardiac surgery

CONTEXT

Of the 200 million adults worldwide who undergo noncardiac surgery each year, more than 1 million will die within 30 days.

OBJECTIVE

To determine the relationship between the peak fourth-generation troponin T (TnT) measurement in the first 3 days after noncardiac surgery and 30-day mortality.

DESIGN, SETTING, AND PARTICIPANTS

A prospective, international cohort study that enrolled patients from August 6, 2007, to January 11, 2011. Eligible patients were aged 45 years and older and required at least an overnight hospital admission after having noncardiac surgery.

MAIN OUTCOME MEASURES

Patients' TnT levels were measured 6 to 12 hours after surgery and on days 1, 2, and 3 after surgery. We undertook Cox regression analysis in which the dependent variable was mortality until 30 days after surgery, and the independent variables included 24 preoperative variables. We repeated this analysis, adding the peak TnT measurement during the first 3 postoperative days as an independent variable and used a minimum P value approach to determine if there were TnT thresholds that independently altered patients' risk of death.

RESULTS

A total of 15,133 patients were included in this study. The 30-day mortality rate was 1.9% (95% CI, 1.7%-2.1%). Multivariable analysis demonstrated that peak TnT values of at least 0.02 ng/mL, occurring in 11.6% of patients, were associated with higher 30-day mortality compared with the reference group (peak TnT ≤ 0.01 ng/mL): peak TnT of 0.02 ng/mL (adjusted hazard ratio [aHR], 2.41; 95% CI, 1.33-3.77); 0.03 to 0.29 ng/mL (aHR, 5.00; 95% CI, 3.72-6.76); and 0.30 ng/mL or greater (aHR, 10.48; 95% CI, 6.25-16.62). Patients with a peak TnT value of 0.01 ng/mL or less, 0.02, 0.03-0.29, and 0.30 or greater had 30-day mortality rates of 1.0%, 4.0%, 9.3%, and 16.9%, respectively. Peak TnT measurement added incremental prognostic value to discriminate those likely to die within 30 days for the model with peak TnT measurement vs without (C index = 0.85 vs 0.81; difference, 0.4; 95% CI, 0.2-0.5; P < .001 for difference between C index values). The net reclassification improvement with TnT was 25.0% (P < .001).

CONCLUSION

Among patients undergoing noncardiac surgery, the peak postoperative TnT measurement during the first 3 days after surgery was significantly associated with 30-day mortality.