Perioperative effectiveness research using large databases

Anesthesia Techniques for Vitreoretinal Surgery in the United States: A Report from the Multicenter Perioperative Outcomes Group Research Consortium

PURPOSE

To explore the patterns of anesthesia use and their determinants during vitreoretinal (VR) surgeries in academic and community hospitals across the US, using data from the Multicenter Perioperative Outcomes Group (MPOG).

DESIGN

A retrospective, multicenter, cohort study.

METHODS

We queried the MPOG database of 107,066 patients undergoing VR surgeries. Patients (≥18 years) undergoing VR surgery with monitored anesthesia care (MAC) or general anesthesia (GA) from January 1, 2015 to December 31, 2021 were included. Patient-level, case-based, and institutional-level covariates were collected. We performed multivariable mixed-effects models to determine predictors of anesthesia type use. The primary outcome was the type of anesthesia (MAC or GA) used during VR surgeries. As a secondary outcome, MAC cases were further classified based on the additional use of sedation into MAC with or without sedation.

RESULTS

We found that 67.45% of VR surgery cases received MAC, and 73.63% of institutions administered MAC to more than half of cases. Random effect modeling revealed that 47.76% of the variation in MAC use was attributed to institutions. A trend toward increased use of MAC with increasing age was observed. Patients diagnosed with chronic pulmonary disease, liver disease, or a history of drug abuse were less likely to receive MAC. Conversely, we found that patients with reported alcohol abuse disorder, diabetes with complications, and those with American Society of Anesthesiologists (ASA) physical status of 4 (vs. 1, 2, or 3) were more likely to use MAC. Compared to non-complex VR surgeries, there was a notably decreased likelihood of MAC use in complex PPV (P = .004), PPV + scleral buckle (SB) for retinal detachment (P < .0001), and primary SB surgery (P < .0001).

CONCLUSIONS

Approximately 2/3 of VR anesthesia is under MAC, but GA is still preferred for SBs, complex vitrectomy, and younger patients. We show that large interinstitutional variation for using MAC in practice exists.

Does Anesthesia Quality Improvement Participation Lead to Incremental Savings in a Surgical Quality Collaborative Population? A Retrospective Observational Study

BACKGROUND

The Anesthesiology Performance Improvement and Reporting Exchange (ASPIRE) Collaborative Quality Initiative (CQI) was launched as a partnership among hospitals to measure quality, review evidence-based practices, and improve anesthesia-related outcomes. Cost savings and improved patient outcomes have been associated with surgical CQI participation, but the impact of an anesthesia CQI on health care cost has not been thoroughly assessed. In this study, we evaluated whether participation in an anesthesia CQI led to health care savings. We hypothesized that ASPIRE participation is associated with reduced total episode payments for payers and major, high-volume procedures included in the Michigan Value Collaborative (MVC) registry.

METHODS

In this retrospective observational study, we compared MVC episode payment data from Group 1 ASPIRE hospitals, the first cluster of 8 Michigan hospitals to join ASPIRE in January 2015, to non-ASPIRE matched control hospitals. MVC computes price-standardized, risk-adjusted payments for patients insured by Blue Cross Blue Shield of Michigan Preferred Provider Organization, Blue Care Network Health Maintenance Organization, and Medicare Fee-for-Service plans. Episodes from 2014 comprised the pre-ASPIRE time period, and episodes from June 2016 to July 2017 constituted the post-ASPIRE time period. We performed a difference-in-differences analysis to evaluate whether ASPIRE implementation was associated with greater reduction in total episode payments compared to the change in the control hospitals during the same time periods.

RESULTS

We found a statistically significant reduction in total episode (-$719; 95% CI [-$1340 to -$97]; P = .023) payments at the 8 ASPIRE hospitals (N = 17,852 cases) compared to the change observed in 8 matched non-ASPIRE hospitals (N = 12,987 cases) for major, high-volume surgeries, including colectomy, colorectal cancer resection, gastrectomy, esophagectomy, pancreatectomy, hysterectomy, joint replacement (knee and hip), and hip fracture repair. In secondary analyses, 30-day postdischarge (-$354; 95% CI [-$582 to -$126]; P = .002) payments were also significantly reduced in ASPIRE hospitals compared to non-ASPIRE controls. Subgroup analyses revealed a significant reduction in total episode payments for joint replacements (-$860; 95% CI [-$1222 to -$499]; P < .001) at ASPIRE-participating hospitals. Sensitivity analyses including patient-level covariates also showed consistent results.

CONCLUSIONS

Participation in an anesthesiology CQI, ASPIRE, is associated with lower total episode payments for selected major, high-volume procedures. This analysis supports that participation in an anesthesia CQI can lead to reduced health care payments.

A Narrative Review of Multiinstitutional Data Registries of Pediatric Congenital Heart Disease in Pediatric Cardiac Anesthesia and Critical Care Medicine

Congenital heart disease (CHD) is one of the most common birth anomalies. While the care of children with CHD has improved over recent decades, children with CHD who undergo general anesthesia remain at increased risk for morbidity and mortality. Electronic health record systems have enabled institutions to combine data on the management and outcomes of children with CHD in multicenter registries. The application of descriptive analytics methods to these data can improve clinicians' understanding and care of children with CHD. This narrative review covers efforts to leverage multicenter data registries relevant to pediatric cardiac anesthesia and critical care to improve the care of children with CHD.

Routinely collected data and patient-centred research in anaesthesia and peri-operative care: a narrative review

Randomised controlled trials are the gold standard in clinical research, but remain rare due to their expense and a perceived lack of 'real-world' applicability. At the same time, there has been an exponential increase in routinely collected data which presents opportunities for audit, quality improvement, adverse event reporting and more efficient clinical research. Registry-based research benefits from reduced cost, large sample size and real-world applicability, with methodological developments, particularly registry-based randomised controlled trials and causal inference techniques, showing promise. Limitations include data quality and validity, the need for data linkage, the restrictions of fixed data fields, regulatory barriers, and privacy and security concerns. However, the principal factor hampering current efforts is a lack of anaesthesia-specific datasets in the UK and the fact that most surgical registries do not collect any anaesthetic data. This presents an opportunity for anaesthetists, through enhanced engagement and collaboration, to influence and improve the design of these datasets and increase the value and volume of data collected. Better datasets, coupled with a growing appreciation of new analysis methodologies, would allow significant progress towards realising the potential of routinely collected data for patient benefit. At the same time, work should begin on the development of a minimum dataset for anaesthesia to underpin new data sharing networks and, ideally, a national registry of anaesthesia.

Neural Machine Translation-Based Automated Current Procedural Terminology Classification System Using Procedure Text: Development and Validation Study

BACKGROUND

Administrative costs for billing and insurance-related activities in the United States are substantial. One critical cause of the high overhead of administrative costs is medical billing errors. With advanced deep learning techniques, developing advanced models to predict hospital and professional billing codes has become feasible. These models can be used for administrative cost reduction and billing process improvements.

OBJECTIVE

In this study, we aim to develop an automated anesthesiology current procedural terminology (CPT) prediction system that translates manually entered surgical procedure text into standard forms using neural machine translation (NMT) techniques. The standard forms are calculated using similarity scores to predict the most appropriate CPT codes. Although this system aims to enhance medical billing coding accuracy to reduce administrative costs, we compare its performance with that of previously developed machine learning algorithms.

METHODS

We collected and analyzed all operative procedures performed at Michigan Medicine between January 2017 and June 2019 (2.5 years). The first 2 years of data were used to train and validate the existing models and compare the results from the NMT-based model. Data from 2019 (6-month follow-up period) were then used to measure the accuracy of the CPT code prediction. Three experimental settings were designed with different data types to evaluate the models. Experiment 1 used the surgical procedure text entered manually in the electronic health record. Experiment 2 used preprocessing of the procedure text. Experiment 3 used preprocessing of the combined procedure text and preoperative diagnoses. The NMT-based model was compared with the support vector machine (SVM) and long short-term memory (LSTM) models.

RESULTS

The NMT model yielded the highest top-1 accuracy in experiments 1 and 2 at 81.64% and 81.71% compared with the SVM model (81.19% and 81.27%, respectively) and the LSTM model (80.96% and 81.07%, respectively). The SVM model yielded the highest top-1 accuracy of 84.30% in experiment 3, followed by the LSTM model (83.70%) and the NMT model (82.80%). In experiment 3, the addition of preoperative diagnoses showed 3.7%, 3.2%, and 1.3% increases in the SVM, LSTM, and NMT models in top-1 accuracy over those in experiment 2, respectively. For top-3 accuracy, the SVM, LSTM, and NMT models achieved 95.64%, 95.72%, and 95.60% for experiment 1, 95.75%, 95.67%, and 95.69% for experiment 2, and 95.88%, 95.93%, and 95.06% for experiment 3, respectively.

CONCLUSIONS

This study demonstrates the feasibility of creating an automated anesthesiology CPT classification system based on NMT techniques using surgical procedure text and preoperative diagnosis. Our results show that the performance of the NMT-based CPT prediction system is equivalent to that of the SVM and LSTM prediction models. Importantly, we found that including preoperative diagnoses improved the accuracy of using the procedure text alone.

Overview and Limitations of Database Research in Anesthesiology: A Narrative Review

The utilization of large-scale databases for research in medical fields, including anesthesiology, has increased in popularity over the last decade, likely due to their structured content and relative ease of access. These databases have been used in a variety of perioperative studies, including analyses of risk stratification, preoperative testing, complications, and cost. While these databases contain a wealth of information that allows for an abundance of research opportunities, there are unique limitations to their use. A comprehensive understanding will afford the anesthesiology researcher the knowledge and tools to not only better interpret studies that utilized these databases, but also to conduct analyses of their own. This review details the content and composition of these databases, highlights the advantages of and limitations to their use, and offers information about their access and cost.

Identifying Risks and Opportunities in Outpatient Surgical Patient Safety: A Qualitative Analysis of Veterans Health Administration Staff Perceptions

OBJECTIVES

Little is known about patient safety risks in outpatient surgery. Inpatient surgical adverse events (AEs) risk factors include patient- (e.g., advanced age), process- (e.g., inadequate preoperative assessment), or structure-related characteristics (e.g., low surgical volume); however, these factors may differ from outpatient care where surgeries are often elective and in younger/healthier patients. We undertook an exploratory qualitative research project to identify risk factors for AEs in outpatient surgery.

METHODS

We developed a conceptual framework of patient, process, and structure factors associated with surgical AEs on the basis of a literature review. This framework informed our semistructured interview guide with (1) open-ended questions about a specific outpatient AE that the participant experienced and (2) outpatient surgical patient safety risk factors in general. We interviewed nationwide Veterans Health Administration surgical staff. Results were coded on the basis of categories in the conceptual framework, and additional themes were identified using content analysis.

RESULTS

Fourteen providers representing diverse surgical roles participated. Ten reported witnessing an AE, and everyone provided input on risk factors in our conceptual framework. We did not find evidence that patient race/age, surgical technique, or surgical volume affected patient safety. Emerging factors included patient compliance, postoperative patient assessments/instruction, operating room equipment needs, and safety culture.

CONCLUSIONS

Surgical staff are familiar with AEs and patient safety problems in outpatient surgery. Our results show that processes of care undertaken by surgical providers, as opposed to immutable patient characteristics, may affect the occurrence of AEs. The factors we identified may facilitate more targeted research on outpatient surgical AEs.

Optimal Hemodynamic Parameters for Brain-injured Patients in the Clinical Setting: A Narrative Review of the Evidence

Defining optimal hemodynamic targets for brain-injured patients is a challenging undertaking. The physiological interference observed in various intracranial pathologies can have varying effects on cerebral physiology at different time points. This narrative review provides an overview of cerebral autoregulatory physiology and common misconceptions, and examines the physiological considerations and clinical evidence for determining optimal hemodynamic parameters in acutely brain-injured patients with relevance to modern neuroanesthesia and neurocritical care practice.

Improving Identification of Patients at Low Risk for Major Cardiac Events After Noncardiac Surgery Using Intraoperative Data

BACKGROUND/OBJECTIVE

Risk-stratification tools for cardiac complications after noncardiac surgery based on preoperative risk factors are used to inform postoperative management. However, there is limited evidence on whether risk stratification can be improved by incorporating data collected intraoperatively, particularly for low-risk patients.

METHODS

We conducted a retrospective cohort study of adults who underwent noncardiac surgery between 2014 and 2018 at four hospitals in the United States. Logistic regression with elastic net selection was used to classify in-hospital major adverse cardiovascular events (MACE) using preoperative and intraoperative data ("perioperative model"). We compared model performance to standard risk stratification tools and professional society guidelines that do not use intraoperative data.

RESULTS

Of 72,909 patients, 558 (0.77%) experienced MACE. Those with MACE were older and less likely to be female. The perioperative model demonstrated an area under the receiver operating characteristic curve (AUC) of 0.88 (95% CI, 0.85-0.92). This was higher than the Lee Revised Cardiac Risk Index (RCRI) AUC of 0.79 (95% CI, 0.74-0.84; P < .001 for AUC comparison). There were more MACE complications in the top decile (n = 1,465) of the perioperative model's predicted risk compared with that of the RCRI model (n = 58 vs 43). Additionally, the perioperative model identified 2,341 of 7,597 (31%) patients as low risk who did not experience MACE but were recommended to receive postoperative biomarker testing by a risk factor-based guideline algorithm.

CONCLUSIONS

Addition of intraoperative data to preoperative data improved prediction of cardiovascular complication outcomes after noncardiac surgery and could potentially help reduce unnecessary postoperative testing.

Classification of Current Procedural Terminology Codes from Electronic Health Record Data Using Machine Learning

BACKGROUND

Accurate anesthesiology procedure code data are essential to quality improvement, research, and reimbursement tasks within anesthesiology practices. Advanced data science techniques, including machine learning and natural language processing, offer opportunities to develop classification tools for Current Procedural Terminology codes across anesthesia procedures.

METHODS

Models were created using a Train/Test dataset including 1,164,343 procedures from 16 academic and private hospitals. Five supervised machine learning models were created to classify anesthesiology Current Procedural Terminology codes, with accuracy defined as first choice classification matching the institutional-assigned code existing in the perioperative database. The two best performing models were further refined and tested on a Holdout dataset from a single institution distinct from Train/Test. A tunable confidence parameter was created to identify cases for which models were highly accurate, with the goal of at least 95% accuracy, above the reported 2018 Centers for Medicare and Medicaid Services (Baltimore, Maryland) fee-for-service accuracy. Actual submitted claim data from billing specialists were used as a reference standard.

RESULTS

Support vector machine and neural network label-embedding attentive models were the best performing models, respectively, demonstrating overall accuracies of 87.9% and 84.2% (single best code), and 96.8% and 94.0% (within top three). Classification accuracy was 96.4% in 47.0% of cases using support vector machine and 94.4% in 62.2% of cases using label-embedding attentive model within the Train/Test dataset. In the Holdout dataset, respective classification accuracies were 93.1% in 58.0% of cases and 95.0% among 62.0%. The most important feature in model training was procedure text.

CONCLUSIONS

Through application of machine learning and natural language processing techniques, highly accurate real-time models were created for anesthesiology Current Procedural Terminology code classification. The increased processing speed and a priori targeted accuracy of this classification approach may provide performance optimization and cost reduction for quality improvement, research, and reimbursement tasks reliant on anesthesiology procedure codes.

Multicenter Perioperative Outcomes Group Enhanced Observation Study Postoperative Pain Profiles, Analgesic Use, and Transition to Chronic Pain and Excessive and Prolonged Opioid Use Patterns Methodology

To study the impact of anesthesia opioid-related outcomes and acute and chronic postsurgical pain, we organized a multicenter study that comprehensively combined detailed perioperative data elements from multiple institutions. By combining pre- and postoperative patient-reported outcomes with automatically extracted high-resolution intraoperative data obtained through the Multicenter Perioperative Outcomes Group (MPOG), the authors sought to describe the impact of patient characteristics, preoperative psychological factors, surgical procedure, anesthetic course, postoperative pain management, and postdischarge pain management on postdischarge pain profiles and opioid consumption patterns. This study is unique in that it utilized multicenter prospective data collection using a digital case report form integrated with the MPOG framework and database. Therefore, the study serves as a model for future studies using this innovative method. Full results will be reported in future articles; the purpose of this article is to describe the methods of this study.

Preoperative Risk and the Association between Hypotension and Postoperative Acute Kidney Injury

BACKGROUND

Despite the significant healthcare impact of acute kidney injury, little is known regarding prevention. Single-center data have implicated hypotension in developing postoperative acute kidney injury. The generalizability of this finding and the interaction between hypotension and baseline patient disease burden remain unknown. The authors sought to determine whether the association between intraoperative hypotension and acute kidney injury varies by preoperative risk.

METHODS

Major noncardiac surgical procedures performed on adult patients across eight hospitals between 2008 and 2015 were reviewed. Derivation and validation cohorts were used, and cases were stratified into preoperative risk quartiles based upon comorbidities and surgical procedure. After preoperative risk stratification, associations between intraoperative hypotension and acute kidney injury were analyzed. Hypotension was defined as the lowest mean arterial pressure range achieved for more than 10 min; ranges were defined as absolute (mmHg) or relative (percentage of decrease from baseline).

RESULTS

Among 138,021 cases reviewed, 12,431 (9.0%) developed postoperative acute kidney injury. Major risk factors included anemia, estimated glomerular filtration rate, surgery type, American Society of Anesthesiologists Physical Status, and expected anesthesia duration. Using such factors and others for risk stratification, patients with low baseline risk demonstrated no associations between intraoperative hypotension and acute kidney injury. Patients with medium risk demonstrated associations between severe-range intraoperative hypotension (mean arterial pressure less than 50 mmHg) and acute kidney injury (adjusted odds ratio, 2.62; 95% CI, 1.65 to 4.16 in validation cohort). In patients with the highest risk, mild hypotension ranges (mean arterial pressure 55 to 59 mmHg) were associated with acute kidney injury (adjusted odds ratio, 1.34; 95% CI, 1.16 to 1.56). Compared with absolute hypotension, relative hypotension demonstrated weak associations with acute kidney injury not replicable in the validation cohort.

CONCLUSIONS

Adult patients undergoing noncardiac surgery demonstrate varying associations with distinct levels of hypotension when stratified by preoperative risk factors. Specific levels of absolute hypotension, but not relative hypotension, are an important independent risk factor for acute kidney injury.

Sugammadex versus Neostigmine for Reversal of Neuromuscular Blockade and Postoperative Pulmonary Complications (STRONGER): A Multicenter Matched Cohort Analysis

BACKGROUND

Five percent of adult patients undergoing noncardiac inpatient surgery experience a major pulmonary complication. The authors hypothesized that the choice of neuromuscular blockade reversal (neostigmine vs. sugammadex) may be associated with a lower incidence of major pulmonary complications.

METHODS

Twelve U.S. Multicenter Perioperative Outcomes Group hospitals were included in a multicenter observational matched-cohort study of surgical cases between January 2014 and August 2018. Adult patients undergoing elective inpatient noncardiac surgical procedures with general anesthesia and endotracheal intubation receiving a nondepolarizing neuromuscular blockade agent and reversal were included. Exact matching criteria included institution, sex, age, comorbidities, obesity, surgical procedure type, and neuromuscular blockade agent (rocuronium vs. vecuronium). Other preoperative and intraoperative factors were compared and adjusted in the case of residual imbalance. The composite primary outcome was major postoperative pulmonary complications, defined as pneumonia, respiratory failure, or other pulmonary complications (including pneumonitis; pulmonary congestion; iatrogenic pulmonary embolism, infarction, or pneumothorax). Secondary outcomes focused on the components of pneumonia and respiratory failure.

RESULTS

Of 30,026 patients receiving sugammadex, 22,856 were matched to 22,856 patients receiving neostigmine. Out of 45,712 patients studied, 1,892 (4.1%) were diagnosed with the composite primary outcome (3.5% sugammadex vs. 4.8% neostigmine). A total of 796 (1.7%) patients had pneumonia (1.3% vs. 2.2%), and 582 (1.3%) respiratory failure (0.8% vs. 1.7%). In multivariable analysis, sugammadex administration was associated with a 30% reduced risk of pulmonary complications (adjusted odds ratio, 0.70; 95% CI, 0.63 to 0.77), 47% reduced risk of pneumonia (adjusted odds ratio, 0.53; 95% CI, 0.44 to 0.62), and 55% reduced risk of respiratory failure (adjusted odds ratio, 0.45; 95% CI, 0.37 to 0.56), compared to neostigmine.

CONCLUSIONS

Among a generalizable cohort of adult patients undergoing inpatient surgery at U.S. hospitals, the use of sugammadex was associated with a clinically and statistically significant lower incidence of major pulmonary complications.

Risk Stratification for Postoperative Acute Kidney Injury in Major Noncardiac Surgery Using Preoperative and Intraoperative Data

IMPORTANCE

Acute kidney injury (AKI) is one of the most common complications after noncardiac surgery. Yet current postoperative AKI risk stratification models have substantial limitations, such as limited use of perioperative data.

OBJECTIVE

To examine whether adding preoperative and intraoperative data is associated with improved prediction of noncardiac postoperative AKI.

DESIGN, SETTING, AND PARTICIPANTS

A prognostic study using logistic regression with elastic net selection, gradient boosting machine (GBM), and random forest approaches was conducted at 4 tertiary academic hospitals in the United States. A total of 42 615 hospitalized adults with serum creatinine measurements who underwent major noncardiac surgery between January 1, 2014, and April 30, 2018, were included in the study. Serum creatinine measurements from 365 days before and 7 days after surgery were used in this study.

MAIN OUTCOMES AND MEASURES

Postoperative AKI (defined by the Kidney Disease Improving Global Outcomes within 7 days after surgery) was the primary outcome. The area under the receiver operating characteristic curve (AUC) was used to assess discrimination.

RESULTS

Among 42 615 patients who underwent noncardiac surgery, the mean (SD) age was 57.9 (15.7) years, 23 943 (56.2%) were women, 27 857 (65.4%) were white, and the most frequent surgery types were orthopedic (15 718 [36.9%]), general (8808 [20.7%]), and neurologic (6564 [15.4%]). The rate of postoperative AKI was 10.1% (n = 4318). The progressive addition of clinical data improved model performance across all modeling approaches, with GBM providing the highest discrimination by AUC. In GBM models, the AUC increased from 0.712 (95% CI, 0.694-0.731) using prehospitalization variables to 0.804 (95% CI, 0.788-0.819) using preoperative variables (inclusive of prehospitalization variables) (P < .001 for AUC comparison). The AUC further increased to 0.817 (95% CI, 0.802-0.832) when adding intraoperative variables (P < .001 for comparison vs model using preoperative variables). However, the statistically significant improvements in discrimination did not appear to be clinically significant. In particular, the AKI rate among patients classified as high risk improved from 29.1% to 30.0%, a net of 15 patients were appropriately reclassified as high risk, and an additional 15 patients were appropriately reclassified as low risk.

CONCLUSIONS AND RELEVANCE

The findings of the study suggest that electronic health record data may be used to accurately stratify patients at risk of perioperative AKI, but the modest improvements from adding intraoperative data should be weighed against challenges in using intraoperative data.

Intraoperative Mechanical Ventilation and Postoperative Pulmonary Complications after Cardiac Surgery

BACKGROUND

Compared with historic ventilation strategies, modern lung-protective ventilation includes lower tidal volumes (VT), lower driving pressures, and application of positive end-expiratory pressure (PEEP). The contributions of each component to an overall intraoperative protective ventilation strategy aimed at reducing postoperative pulmonary complications have neither been adequately resolved, nor comprehensively evaluated within an adult cardiac surgical population. The authors hypothesized that a bundled intraoperative protective ventilation strategy was independently associated with decreased odds of pulmonary complications after cardiac surgery.

METHODS

In this observational cohort study, the authors reviewed nonemergent cardiac surgical procedures using cardiopulmonary bypass at a tertiary care academic medical center from 2006 to 2017. The authors tested associations between bundled or component intraoperative protective ventilation strategies (VT below 8 ml/kg ideal body weight, modified driving pressure [peak inspiratory pressure - PEEP] below 16 cm H2O, and PEEP greater than or equal to 5 cm H2O) and postoperative outcomes, adjusting for previously identified risk factors. The primary outcome was a composite pulmonary complication; secondary outcomes included individual pulmonary complications, postoperative mortality, as well as durations of mechanical ventilation, intensive care unit stay, and hospital stay.

RESULTS

Among 4,694 cases reviewed, 513 (10.9%) experienced pulmonary complications. After adjustment, an intraoperative lung-protective ventilation bundle was associated with decreased pulmonary complications (adjusted odds ratio, 0.56; 95% CI, 0.42-0.75). Via a sensitivity analysis, modified driving pressure below 16 cm H2O was independently associated with decreased pulmonary complications (adjusted odds ratio, 0.51; 95% CI, 0.39-0.66), but VT below 8 ml/kg and PEEP greater than or equal to 5 cm H2O were not.

CONCLUSIONS

The authors identified an intraoperative lung-protective ventilation bundle as independently associated with pulmonary complications after cardiac surgery. The findings offer insight into components of protective ventilation associated with adverse outcomes and may serve as targets for future prospective interventional studies investigating the impact of specific protective ventilation strategies on postoperative outcomes after cardiac surgery.

Dissecting genetic factors affecting phenylephrine infusion rates during anesthesia: a genome-wide association study employing EHR data

BACKGROUND

The alpha-adrenergic agonist phenylephrine is often used to treat hypotension during anesthesia. In clinical situations, low blood pressure may require prompt intervention by intravenous bolus or infusion. Differences in responsiveness to phenylephrine treatment are commonly observed in clinical practice. Candidate gene studies indicate genetic variants may contribute to this variable response.

METHODS

Pharmacological and physiological data were retrospectively extracted from routine clinical anesthetic records. Response to phenylephrine boluses could not be reliably assessed, so infusion rates were used for analysis. Unsupervised k-means clustering was conducted on clean data containing 4130 patients based on phenylephrine infusion rate and blood pressure parameters, to identify potential phenotypic subtypes. Genome-wide association studies (GWAS) were performed against average infusion rates in two cohorts: phase I (n = 1205) and phase II (n = 329). Top genetic variants identified from the meta-analysis were further examined to see if they could differentiate subgroups identified by k-means clustering.

RESULTS

Three subgroups of patients with different response to phenylephrine were clustered and characterized: resistant (high infusion rate yet low mean systolic blood pressure (SBP)), intermediate (low infusion rate and low SBP), and sensitive (low infusion rate with high SBP). Differences among clusters were tabulated to assess for possible confounding influences. Comorbidity hierarchical clustering showed the resistant group had a higher prevalence of confounding factors than the intermediate and sensitive groups although overall prevalence is below 6%. Three loci with P < 1 × 10^-6 were associated with phenylephrine infusion rate. Only rs11572377 with P = 6.09 × 10^-7, a 3'UTR variant of EDN2, encoding a secretory vasoconstricting peptide, could significantly differentiate resistant from sensitive groups (P = 0.015 and 0.018 for phase I and phase II) or resistant from pooled sensitive and intermediate groups (P = 0.047 and 0.018).

CONCLUSIONS

Retrospective analysis of electronic anesthetic records data coupled with the genetic data identified genetic variants contributing to variable sensitivity to phenylephrine infusion during anesthesia. Although the identified top gene, EDN2, has robust biological relevance to vasoconstriction by binding to endothelin type A (ET_A) receptors on arterial smooth muscle cells, further functional as well as replication studies are necessary to confirm this association.

A retrospective analysis of 62,571 cases of perioperative adverse events in thoracic surgery at a tertiary care teaching hospital in a developing country

Objectives

Despite a long history of concerns regarding patient safety during clinical care, some patients undergoing thoracic surgery continue to experience adverse events (AEs). AEs are a major significant source of perioperative morbidity and mortality following thoracic surgery. This study analysed the causes, treatment and prognosis of perioperative AEs to provide a reference for further surgical safety.

Methods

The authors collected a total of 62,571 thoracic surgery anaesthesia records via the Anaesthesia Information Management System (AIMS) from 14 August 2006 to 14 August 2017 and obtained 150 cases of perioperative serious AEs from the “adverse events registration” subsystem. The related hospitalization data of the 150 patients were analysed, including anaesthesia, recovery room time, ICU records and follow-up outcomes. The causes of these AEs were classified as follows: events related to the patients’ pathogenic conditions(P); surgery-related factors(S); anaesthesia-related factors(A); and interactions between pathogenic, surgical and anaesthesia factors (P&S&A). We then analysed the main clinical manifestations, causes and treatment of these events.

Results

The overall rate of perioperative AEs in thoracic surgery (n = 62,571) was 0.2%. Of these, 10.7% were.

caused by P and 23.3% by A; neither cause led to patient death. S and P&S&A accounted for 55.3 and 10.7% of AEs, respectively; together, they accounted for 66%. Twelve patients with postoperative AEs caused by S or P&S&A died within 3 days (8% of 150 cases). A total of 33%(50/150) of patients experienced sudden cardiac arrest (SCA) and recovered successfully. Surgical massive haemorrhage (22%, 33/150) was reported as a predominant mortality-related outcome in this group, and 8 of the 12 deaths were caused by massive haemorrhage.

Conclusions

The rate of perioperative AEs after thoracic surgery was 0.2%. AEs must be identified and treated immediately. An important factor in anaesthesia-related events was respiratory management. Two major clinical manifestations of surgery-related events were cardiac arrest and massive haemorrhage. Cardiac arrest was the major factor contributing to AEs, but its adverse consequences could be avoided with timely discovery and proper treatment. Massive haemorrhage is a significant cause of mortality that can be prevented with a surgeon’s early diagnosis and appropriate interventions.

Effectiveness of intravenous acetaminophen for postoperative pain management in hip and knee arthroplasties: a population-based study

BACKGROUND AND OBJECTIVES

The significance of intravenous over oral acetaminophen (APAP) as part of multimodal analgesic protocols is contested, particularly when considering its relatively high price and use in a surgical cohort such as total hip or knee arthroplasty (THA/TKA), which generally tolerates oral medications. This study aims to elucidate APAP's effectiveness in a large, population-based patient sample.

METHODS

1 039 647 THA/TKA procedures were sampled from the Premier Healthcare claims database 2011-2016. APAP use was categorized by intravenous/oral and use on the day of surgery, postoperative day 1 and thereafter. Outcomes were opioid utilization (in oral morphine equivalents), length and cost of hospitalization, and opioid-related adverse effects (respiratory, gastrointestinal, and naloxone use as a proxy). Mixed-effects models measured the associations between intravenous/oral APAP use and outcomes. Percent (%) change and 95% CIs are reported.

RESULTS

Overall, 23.6% (n=245 454) of patients received intravenous APAP; of these, 56.3% (n=138 180) received just one dose on the day of surgery. After adjustment for relevant covariates, particularly use of >1 dose of intravenous APAP (compared with no use) on postoperative day 1 was associated with -6.0% (CI -7.2% to -4.7%) reduced opioid utilization; this was -10.7% (CI -11.4% to -9.9%) for use of > 1 dose oral APAP on postoperative day 1. Further comparisons regarding other outcomes also favored oral (over intravenous) APAP.

CONCLUSIONS

These results do not support the routine use of intravenous APAP in patients undergoing lower joint arthroplasty, especially since oral APAP shows more beneficial outcome patterns.

What we can learn from Big Data about factors influencing perioperative outcome

PURPOSE OF REVIEW

This narrative review will discuss what value Big Data has to offer anesthesiology and aims to highlight recently published articles of large databases exploring factors influencing perioperative outcome. Additionally, the future perspectives of Big Data and its major pitfalls will be discussed.

RECENT FINDINGS

The potential of Big Data has given an incentive to create nationwide and anesthesia-initiated registries like the MPOG and NACOR. These large databases have contributed in elucidating some of the rare perioperative complications, such as declined cognition after exposure to general anesthesia and epidural hematomas in parturients. Additionally, they are useful in finding patterns such as similar outcome in subtypes of beta-blockers and lower incidence of pneumonia in preoperative influenza vaccinations in the elderly.

SUMMARY

Big Data is becoming increasingly popular with the collaborative collection of registries offering anesthesia a way to explore rare perioperative complications and outcome to encourage further hypotheses testing. Although Big Data has its flaws in security, lack of expertise and methodological concerns, the future potential of analytics combined with genomics, machine learning and real-time decision support looks promising.

Succinylcholine Use and Dantrolene Availability for Malignant Hyperthermia Treatment: Database Analyses and Systematic Review

BACKGROUND

Although dantrolene effectively treats malignant hyperthermia (MH), discrepant recommendations exist concerning dantrolene availability. Whereas Malignant Hyperthermia Association of the United States guidelines state dantrolene must be available within 10 min of the decision to treat MH wherever volatile anesthetics or succinylcholine are administered, a Society for Ambulatory Anesthesia protocol permits Class B ambulatory facilities to stock succinylcholine for airway rescue without dantrolene. The authors investigated (1) succinylcholine use rates, including for airway rescue, in anesthetizing/sedating locations; (2) whether succinylcholine without volatile anesthetics triggers MH warranting dantrolene; and (3) the relationship between dantrolene administration and MH morbidity/mortality.

METHODS

The authors performed focused analyses of the Multicenter Perioperative Outcomes Group (2005 through 2016), North American MH Registry (2013 through 2016), and Anesthesia Closed Claims Project (1970 through 2014) databases, as well as a systematic literature review (1987 through 2017). The authors used difficult mask ventilation (grades III and IV) as a surrogate for airway rescue. MH experts judged dantrolene treatment. For MH morbidity/mortality analyses, the authors included U.S. and Canadian cases that were fulminant or scored 20 or higher on the clinical grading scale and in which volatile anesthetics or succinylcholine were given.

RESULTS

Among 6,368,356 queried outcomes cases, 246,904 (3.9%) received succinylcholine without volatile agents. Succinylcholine was used in 46% (n = 710) of grade IV mask ventilation cases (median dose, 100 mg, 1.2 mg/kg). Succinylcholine without volatile anesthetics triggered 24 MH cases, 13 requiring dantrolene. Among 310 anesthetic-triggered MH cases, morbidity was 20 to 37%. Treatment delay increased complications every 10 min, reaching 100% with a 50-min delay. Overall mortality was 1 to 10%; 15 U.S. patients died, including 4 after anesthetics in freestanding facilities.

CONCLUSIONS

Providers use succinylcholine commonly, including during difficult mask ventilation. Succinylcholine administered without volatile anesthetics may trigger MH events requiring dantrolene. Delayed dantrolene treatment increases the likelihood of MH complications. The data reported herein support stocking dantrolene wherever succinylcholine or volatile anesthetics may be used.

Management of 1-Lung Ventilation-Variation and Trends in Clinical Practice: A Report From the Multicenter Perioperative Outcomes Group

BACKGROUND

Lung-protective ventilation (LPV) has been demonstrated to improve clinical outcomes in surgical patients. There are very limited data on the current use of LPV for patients undergoing 1-lung ventilation (1LV) despite evidence that 1LV may be a particularly important setting for its use. In this multicenter study, we report trends in ventilation practice for patients undergoing 1LV.

METHODS

The Multicenter Perioperative Outcomes Group database was used to identify patients undergoing 1LV. We retrieved and calculated median initial and overall tidal volume (VT) for the cohort and for high-risk subgroups (female sex, obesity [body mass index >30 kg/m], and short stature), percentage of patients receiving positive end-expiratory pressure (PEEP) ≥5 cm H2O, LPV during 1LV (VT ≤ 6 mL/kg predicted body weight [PBW] and PEEP ≥5 cm H2O), and ventilator driving pressure (ΔP; plateau airway pressure - PEEP).

RESULTS

Data from 5609 patients across 4 institutions were included in the analysis. Median VT was calculated for each case and since the data were normally distributed, the mean is reported for the entire cohort and subgroups. Mean of median VT during 1LV for the cohort was 6.49 ± 1.82 mL/kg PBW. VT (mL/kg PBW) for high-risk subgroups was significantly higher; 6.86 ± 1.97 for body mass index ≥30 kg/m, 7.05 ± 1.92 for female patients, and 7.33 ± 2.01 for short stature patients. Mean of the median VT declined significantly over the study period (from 6.88 to 5.72; P < .001), and the proportion of patients receiving LPV increased significantly over the study period (from 9.1% to 54.6%; P < .001). These changes coincided with a significant decrease in ΔP during the study period, from 19.4 cm H2O during period 1 to 17.3 cm H2O in period 12 (P = .003).

CONCLUSIONS

Despite a growing awareness of the importance of protective ventilation, a large proportion of patients undergoing 1LV continue to receive VT PEEP levels outside of recommended thresholds. Moreover, VT remains higher and LPV less common in high-risk subgroups, potentially placing them at elevated risk for iatrogenic lung injury.

An observational study of end-tidal carbon dioxide trends in general anesthesia

PURPOSE

Despite growing evidence supporting the potential benefits of higher end-tidal carbon dioxide (ETCO₂) levels in surgical patients, there is still insufficient data to formulate guidelines for ideal intraoperative ETCO₂ targets. As it is unclear which intraoperative ETCO₂ levels are currently used and whether these levels have changed over time, we investigated the practice pattern using the Multicenter Perioperative Outcomes Group database.

METHODS

This retrospective, observational, multicentre study included 317,445 adult patients who received general anesthesia for non-cardiothoracic procedures between January 2008 and September 2016. The primary outcome was a time-weighted average area-under-the-curve (TWA-AUC) for four ETCO₂ thresholds (< 28, < 35, < 45, and > 45 mmHg). Additionally, a median ETCO₂ was studied. A Kruskal-Wallis test was used to analyse differences between years. Random-effect multivariable logistic regression models were constructed to study variability.

RESULTS

Both TWA-AUC and median ETCO₂ showed a minimal increase in ETCO₂ over time, with a median [interquartile range] ETCO₂ of 33 [31.0-35.0] mmHg in 2008 and 35 [33.0-38.0] mmHg in 2016 (P <0.001). A large inter-hospital and inter-provider variability in ETCO₂ were observed after adjustment for patient characteristics, ventilation parameters, and intraoperative blood pressure (intraclass correlation coefficient 0.36; 95% confidence interval, 0.18 to 0.58).

CONCLUSIONS

Between 2008 and 2016, intraoperative ETCO₂ values did not change in a clinically important manner. Interestingly, we found a large inter-hospital and inter-provider variability in ETCO₂ throughout the study period, possibly indicating a broad range of tolerance for ETCO₂, or a lack of evidence to support a specific targeted range. Clinical outcomes were not assessed in this study and they should be the focus of future research.

Factors Associated with Hospital Admission after Outpatient Surgery in the Veterans Health Administration

OBJECTIVE

To examine factors associated with 0- to 7-day admission after outpatient surgery in high-volume specialties: general surgery, orthopedics, urology, ear/nose/throat, and podiatry.

STUDY DESIGN

We calculated rates and assessed diagnosis codes for 0- to 7-day admission after outpatient surgery for Centers for Medicare and Medicaid Services (CMS) and Veterans Health Administration (VA) dually enrolled patients age 65 and older. We also estimated separate multilevel logistic regression models to compare patient, procedure, and facility characteristics associated with postoperative admission.

DATA COLLECTION

2011-2013 surgical encounter data from the VA Corporate Data Warehouse; geographic data from the Area Health Resources File; CMS enrollment and hospital admission data.

PRINCIPAL FINDINGS

Among 63,585 outpatient surgeries in 124 facilities, 0- to 7-day admission rates ranged from 5 percent (podiatry) to 28 percent (urology); nearly 66 percent of the admissions occurred on the day of surgery. Only 97 admissions were detected in the CMS data (1 percent). Surgical complications were diagnosed in 4 percent of admissions. Procedure complexity, measured by relative value units or anesthesia risk score, was associated with admission across all specialties.

CONCLUSION

As many as 20 percent of VA outpatient surgeries result in an admission. Complex procedures are more likely to be followed by admission, but more evidence is required to determine how many of these reflect potential safety or quality problems.

Perioperative Information Systems: Opportunities to Improve Delivery of Care and Clinical Outcomes in Cardiac and Vascular Surgery

A variety of existing perioperative informatics tools offer clinicians and researchers the opportunity to improve the delivery of care and clinical outcomes for patients undergoing cardiac and vascular surgery. Many of these tools can be used to improve the reliability of the care delivery process through the application of clinical decision support tools and/or quality improvement methodologies at a number of junctures. In this review, the authors will offer a concise overview of the existing perioperative informatics literature, with a focus on tools considered to be of utility in confronting the unique challenges inherent to cardiac and vascular surgery. The authors also highlight areas that they believe are of interest for future targeted inquiry.

Risk of Epidural Hematoma after Neuraxial Techniques in Thrombocytopenic Parturients: A Report from the Multicenter Perioperative Outcomes Group

BACKGROUND

Thrombocytopenia has been considered a relative or even absolute contraindication to neuraxial techniques due to the risk of epidural hematoma. There is limited literature to estimate the risk of epidural hematoma in thrombocytopenic parturients. The authors reviewed a large perioperative database and performed a systematic review to further define the risk of epidural hematoma requiring surgical decompression in this population.

METHODS

The authors performed a retrospective cohort study using the Multicenter Perioperative Outcomes Group database to identify thrombocytopenic parturients who received a neuraxial technique and to estimate the risk of epidural hematoma. Patients were stratified by platelet count, and those requiring surgical decompression were identified. A systematic review was performed, and risk estimates were combined with those from the existing literature.

RESULTS

A total of 573 parturients with a platelet count less than 100,000 mm who received a neuraxial technique across 14 institutions were identified in the Multicenter Perioperative Outcomes Group database, and a total of 1,524 parturients were identified after combining the data from the systematic review. No cases of epidural hematoma requiring surgical decompression were observed. The upper bound of the 95% CI for the risk of epidural hematoma for a platelet count of 0 to 49,000 mm is 11%, for 50,000 to 69,000 mm is 3%, and for 70,000 to 100,000 mm is 0.2%.

CONCLUSIONS

The number of thrombocytopenic parturients in the literature who received neuraxial techniques without complication has been significantly increased. The risk of epidural hematoma associated with neuraxial techniques in parturients at a platelet count less than 70,000 mm remains poorly defined due to limited observations.

Arterial Pressure Variation in Elective Noncardiac Surgery: Identifying Reference Distributions and Modifying Factors

BACKGROUND

Assessment of need for intravascular volume resuscitation remains challenging for anesthesiologists. Dynamic waveform indices, including systolic and pulse pressure variation, are demonstrated as reliable measures of fluid responsiveness for mechanically ventilated patients. Despite widespread use, real-world reference distributions for systolic and pulse pressure variation values have not been established for euvolemic intraoperative patients. The authors sought to establish systolic and pulse pressure variation reference distributions and assess the impact of modifying factors.

METHODS

The authors evaluated adult patients undergoing general anesthetics for elective noncardiac surgery. Median systolic and pulse pressure variations during a 50-min postinduction period were noted for each case. Modifying factors including body mass index, age, ventilator settings, positioning, and hemodynamic management were studied via univariate and multivariable analyses. For systolic pressure variation values, effects of data entry method (manually entered vs. automated recorded) were similarly studied.

RESULTS

Among 1,791 cases, per-case median systolic and pulse pressure variation values formed nonparametric distributions. For each distribution, median values, interquartile ranges, and reference intervals (2.5th to 97.5th percentile) were, respectively, noted: these included manually entered systolic pressure variation (6.0, 5.0 to 7.0, and 3.0 to 11.0 mmHg), automated systolic pressure variation (4.7, 3.9 to 6.0, and 2.2 to 10.4 mmHg), and automated pulse pressure variation (7.0, 5.0 to 9.0, and 2.0 to 16.0%). Nonsupine positioning and preoperative β blocker were independently associated with altered systolic and pulse pressure variations, whereas ventilator tidal volume more than 8 ml/kg ideal body weight and peak inspiratory pressure more than 16 cm H2O demonstrated independent associations for systolic pressure variation only.

CONCLUSIONS

This study establishes real-world systolic and pulse pressure variation reference distributions absent in the current literature. Through a consideration of reference distributions and modifying factors, the authors' study provides further evidence for assessing intraoperative volume status and fluid management therapies.

Complications, Risk Factors, and Staffing Patterns for Noncardiac Surgery in Patients with Left Ventricular Assist Devices

BACKGROUND

Patients with left ventricular assist devices presenting for noncardiac surgery are increasingly commonplace; however, little is known about their outcomes. Accordingly, the authors sought to determine the frequency of complications, risk factors, and staffing patterns.

METHODS

The authors performed a retrospective study at their academic tertiary care center, investigating all adult left ventricular assist device patients undergoing noncardiac surgery from 2006 to 2015. The authors described perioperative profiles of noncardiac surgery cases, including patient, left ventricular assist device, surgical case, and anesthetic characteristics, as well as staffing by cardiac/noncardiac anesthesiologists. Through univariate and multivariable analyses, the authors studied acute kidney injury as a primary outcome; secondary outcomes included elevated serum lactate dehydrogenase suggestive of left ventricular assist device thrombosis, intraoperative bleeding complication, and intraoperative hypotension. The authors additionally studied major perioperative complications and mortality.

RESULTS

Two hundred and forty-six patients underwent 702 procedures. Of 607 index cases, 110 (18%) experienced postoperative acute kidney injury, and 16 (2.6%) had elevated lactate dehydrogenase. Of cases with complete blood pressure data, 176 (27%) experienced intraoperative hypotension. Bleeding complications occurred in 45 cases (6.4%). Thirteen (5.3%) patients died within 30 days of surgery. Independent risk factors associated with acute kidney injury included major surgical procedures (adjusted odds ratio, 4.4; 95% CI, 1.1 to 17.3; P = 0.03) and cases prompting invasive arterial line monitoring (adjusted odds ratio, 3.6; 95% CI, 1.3 to 10.3; P = 0.02) or preoperative fresh frozen plasma transfusion (adjusted odds ratio, 1.7; 95% CI, 1.1 to 2.8; P = 0.02).

CONCLUSIONS

Intraoperative hypotension and acute kidney injury were the most common complications in left ventricular assist device patients presenting for noncardiac surgery; perioperative management remains a challenge.

An analysis of perioperative adverse neurological events associated with anesthetic management at a Tertiary Care Center of a developing country

BACKGROUND AND AIMS

Existing literature on neurological complications related to anesthesia is reported from affluent countries but the trends may vary in less affluent countries.

MATERIAL AND METHODS

The objective was to find the associated factors contributing to neurological adverse events occurring within 48 h of anesthesia and surgery. The existing departmental morbidity and mortality database was reviewed from 1992 to 2012 for major adverse neurological events. A standardized methodology was used in reviewing and classifying the data. All adverse events were predefined and categorized before filling the form into the following headers; meningitis, cord/plexus/peripheral nerve injury, stroke, paraparesis/paraplegia/quadriparesis/or quadriplegia, new onset postoperative seizures, postoperative vocal cord injury, and a miscellaneous group.

RESULTS

During this period, 195,031 patients underwent anesthesia and twenty-nine patients had major neurological morbidity within 48 h (1:6700). There were three cases of meningitis/meningism, eight cases of cord, plexus or peripheral nerve injury, seven of stroke, four had new onset seizures, one had quadriparesis, five had vocal cord, and one had cranial nerve palsy. Forty-one percent cases received regional anesthesia alone or in combination with the general. In six cases, anesthesia was considered solely responsible. Human error contributed to 93% of these events.

CONCLUSION

This data has helped in identifying areas of concern and can serve as a reference for further audits in the region.

Success of Intubation Rescue Techniques after Failed Direct Laryngoscopy in Adults

Background

Multiple attempts at tracheal intubation are associated with mortality, and successful rescue requires a structured plan. However, there remains a paucity of data to guide the choice of intubation rescue technique after failed initial direct laryngoscopy. The authors studied a large perioperative database to determine success rates for commonly used intubation rescue techniques.

Methods

Using a retrospective, observational, comparative design, the authors analyzed records from seven academic centers within the Multicenter Perioperative Outcomes Group between 2004 and 2013. The primary outcome was the comparative success rate for five commonly used techniques to achieve successful tracheal intubation after failed direct laryngoscopy: (1) video laryngoscopy, (2) flexible fiberoptic intubation, (3) supraglottic airway as part of an exchange technique, (4) optical stylet, and (5) lighted stylet.

Results

A total of 346,861 cases were identified that involved attempted tracheal intubation. A total of 1,009 anesthesia providers managed 1,427 cases of failed direct laryngoscopy followed by subsequent intubation attempts (n = 1,619) that employed one of the five studied intubation rescue techniques. The use of video laryngoscopy resulted in a significantly higher success rate (92%; 95% CI, 90 to 93) than other techniques: supraglottic airway conduit (78%; 95% CI, 68 to 86), flexible bronchoscopic intubation (78%; 95% CI, 71 to 83), lighted stylet (77%; 95% CI, 69 to 83), and optical stylet (67%; 95% CI, 35 to 88). Providers most frequently choose video laryngoscopy (predominantly GlideScope® [Verathon, USA]) to rescue failed direct laryngoscopy (1,122/1,619; 69%), and its use has increased during the study period.

Conclusions

Video laryngoscopy is associated with a high rescue intubation success rate and is more commonly used than other rescue techniques.

Intraoperative Lung-Protective Ventilation Trends and Practice Patterns: A Report from the Multicenter Perioperative Outcomes Group

BACKGROUND

The use of an intraoperative lung-protective ventilation strategy through tidal volume (TV) size reduction and positive end-expiratory pressure (PEEP) has been increasingly investigated. In this article, we describe the current intraoperative lung-protective ventilation practice patterns and trends.

METHODS

By using the Multicenter Perioperative Outcomes Group database, we identified all general endotracheal anesthetics from January 2008 through December 2013 at 10 institutions. The following data were calculated: (1) percentage of patients receiving TV > 10 mL/kg predicted body weight (PBW); (2) median initial and overall TV in mL/kg PBW and; (3) percentage of patients receiving PEEP ≥ 5 cm H2O. The data were analyzed at 3-month intervals. Interinstitutional variability was assessed.

RESULTS

A total of 330,823 patients met our inclusion criteria for this study. During the study period, the percentage of patients receiving TV > 10 mL/kg PBW was reduced for all patients (26% to 14%) and in the subpopulations of obese (41% to 25%), short stature (52% to 36%), and females (39% to 24%; all P values <0.001). There was a significant reduction in TV size (8.90-8.20 mL/kg PBW, P < 0.001). There was also a statistically significant but clinically irrelevant difference between initial and overall TV size (8.65 vs 8.63 mL/kg PBW, P < 0.001). Use of PEEP ≥ 5 cm H2O increased during the study period (25%-45%, P < 0.001). TV usage showed significant interinstitutional variability (P < 0.001).

CONCLUSIONS

Although decreasing, a significant percentage of patients are ventilated with TV > 10 mL/kg PBW, especially if they are female, obese, or of short stature. The use of PEEP ≥ 5 cm H2O has increased significantly. Creating awareness of contemporary practice patterns and demonstrating the efficacy of lung-protective ventilation are still needed to optimize intraoperative ventilation.

Association between Intraoperative Hypotension and Hypertension and 30-day Postoperative Mortality in Noncardiac Surgery

BACKGROUND

Although deviations in intraoperative blood pressure are assumed to be associated with postoperative mortality, critical blood pressure thresholds remain undefined. Therefore, the authors estimated the intraoperative thresholds of systolic blood pressure (SBP), mean blood pressure (MAP), and diastolic blood pressure (DBP) associated with increased risk-adjusted 30-day mortality.

METHODS

This retrospective cohort study combined intraoperative blood pressure data from six Veterans Affairs medical centers with 30-day outcomes to determine the risk-adjusted associations between intraoperative blood pressure and 30-day mortality. Deviations in blood pressure were assessed using three methods: (1) population thresholds (individual patient sum of area under threshold [AUT] or area over threshold 2 SDs from the mean of the population intraoperative blood pressure values), (2). absolute thresholds, and (3) percent change from baseline blood pressure.

RESULTS

Thirty-day mortality was associated with (1) population threshold: systolic AUT (odds ratio, 3.3; 95% CI, 2.2 to 4.8), mean AUT (2.8; 1.9 to 4.3), and diastolic AUT (2.4; 1.6 to 3.8). Approximate conversions of AUT into its separate components of pressure and time were SBP < 67 mmHg for more than 8.2 min, MAP < 49 mmHg for more than 3.9 min, DBP < 33 mmHg for more than 4.4 min. (2) Absolute threshold: SBP < 70 mmHg for more than or equal to 5 min (odds ratio, 2.9; 95% CI, 1.7 to 4.9), MAP < 49 mmHg for more than or equal to 5 min (2.4; 1.3 to 4.6), and DBP < 30 mmHg for more than or equal to 5 min (3.2; 1.8 to 5.5). (3) Percent change: MAP decreases to more than 50% from baseline for more than or equal to 5 min (2.7; 1.5 to 5.0). Intraoperative hypertension was not associated with 30-day mortality with any of these techniques.

CONCLUSION

Intraoperative hypotension, but not hypertension, is associated with increased 30-day operative mortality.

Perioperative research fellowship: planning, implementation, experience

Perioperative outcomes research has gained widespread interest and is viewed as increasingly important among different specialties, including anesthesiology. Outcomes research studies serve to help in the adjustment of risk, allocation of resources, and formulation of hypotheses to guide future research. Pursuing high-quality research projects requires familiarity with a wide range of research methods, and concepts are ideally learned in a dedicated setting. Skills associated with the use of these methods as well as with scientific publishing in general, however, are increasingly challenging to acquire. This article was intended to describe the curriculum and implementation of the Perioperative Medicine and Regional Anesthesia Research Fellowship at the Hospital for Special Surgery. We also proposed a method to evaluate the success of a research fellowship curriculum.

Effectiveness of preoperative beta-blockade on intra-operative heart rate in vascular surgery cases conducted under regional or local anesthesia

BACKGROUND

Preoperative β-blockade has been posited to result in better outcomes for vascular surgery patients by attenuating acute hemodynamic changes associated with stress. However, the incremental effectiveness, if any, of β-blocker usage in blunting heart rate responsiveness for vascular surgery patients who avoid general anesthesia remains unknown.

METHODS

We reviewed an existing database and identified 213 consecutive vascular surgery cases from 2005-2011 conducted without general anesthesia (i.e., under monitored anesthesia care or regional anesthesia) at a tertiary care Veterans Administration medical center and categorized patients based on presence or absence of preoperative β-blocker prescription. For this series of patients, with the primary outcome of maximum heart rate during the interval between operating room entry to surgical incision, we examined the association of maximal heart rate and preoperative β-blocker usage by performing crude and multivariate linear regression, adjusting for relevant patient factors.

RESULTS

Of 213 eligible cases, 137 were prescribed preoperative β-blockers, and 76 were not. The two groups were comparable across baseline patient factors and intraoperative medication doses. The β-blocker group experienced lower maximal heart rates during the period of evaluation compared to the non-β-blocker group (85 ± 22 bpm vs. 98 ± 36 bpm, respectively; p = 0.002). Adjusted linear regression confirmed a statistically-significant association between lower maximal heart rate and the use of β-blockers (Beta = -11.5; 95% CI [-3.7, -19.3] p = 0.004).

CONCLUSIONS

The addition of preoperative β-blockers, even when general anesthesia is avoided, may be beneficial in further attenuating stress-induced hemodynamic changes for vascular surgery patients.

Incidence, predictors, and outcome of difficult mask ventilation combined with difficult laryngoscopy: a report from the multicenter perioperative outcomes group

BACKGROUND

Research regarding difficult mask ventilation (DMV) combined with difficult laryngoscopy (DL) is extremely limited even though each technique serves as a rescue for one another.

METHODS

Four tertiary care centers participating in the Multicenter Perioperative Outcomes Group used a consistent structured patient history and airway examination and airway outcome definition. DMV was defined as grade 3 or 4 mask ventilation, and DL was defined as grade 3 or 4 laryngoscopic view or four or more intubation attempts. The primary outcome was DMV combined with DL. Patients with the primary outcome were compared to those without the primary outcome to identify predictors of DMV combined with DL using a non-parsimonious logistic regression.

RESULTS

Of 492,239 cases performed at four institutions among adult patients, 176,679 included a documented face mask ventilation and laryngoscopy attempt. Six hundred ninety-eight patients experienced the primary outcome, an overall incidence of 0.40%. One patient required an emergent cricothyrotomy, 177 were intubated using direct laryngoscopy, 284 using direct laryngoscopy with bougie introducer, 163 using videolaryngoscopy, and 73 using other techniques. Independent predictors of the primary outcome included age 46 yr or more, body mass index 30 or more, male sex, Mallampati III or IV, neck mass or radiation, limited thyromental distance, sleep apnea, presence of teeth, beard, thick neck, limited cervical spine mobility, and limited jaw protrusion (c-statistic 0.84 [95% CI, 0.82-0.87]).

CONCLUSION

DMV combined with DL is an infrequent but not rare phenomenon. Most patients can be managed with the use of direct or videolaryngoscopy. An easy to use unweighted risk scale has robust discriminating capacity.

Challenges in research related to perioperative cancer care and cancer outcomes

Surgery is one of the most commonly used treatments to attempt cure of early-stage and some late-stage solid tumours. Paradoxically, surgery itself and some of the medical interventions involved in the perioperative care of cancer patients may be associated with an increased chance of metastasis. Researchers and perioperative clinicians have studied the phenomenon of surgery-induced immunosuppression and postoperative cancer recurrence for several decades. Unfortunately, the translation of basic science research into human studies is not clear. Moreover, a recent proliferation of retrospective studies with conflicting results and significant limitations has not shed light on the understanding of whether regional anaesthesia, anti-inflammatory interventions or blockade of the sympathetic response improve survival after cancer surgery. Ultimately, randomised controlled trials are required to answer some of the questions raised by preclinical and retrospective studies; however, investigators face many challenges in conducting these trials. Unless sufficient funding is obtained and cooperative research is developed in the near future, clinicians will not know whether anticancer perioperative interventions are useful to improve cancer-related survivals.

The surgical Apgar score is strongly associated with intensive care unit admission after high-risk intraabdominal surgery

BACKGROUND

Understanding intensive care unit (ICU) triage decisions for high-risk surgical patients may ultimately facilitate resource allocation and improve outcomes. The surgical Apgar score (SAS) is a simple score that uses intraoperative information on hemodynamics and blood loss to predict postoperative morbidity and mortality, with lower scores associated with worse outcomes. We hypothesized that the SAS would be associated with the decision to admit a patient to the ICU postoperatively.

METHODS

We performed a retrospective cohort study of adults undergoing major intraabdominal surgery from 2003 to 2010 at an academic medical center. We calculated the SAS (0-10) for each patient based on intraoperative heart rate, mean arterial blood pressure, and estimated blood loss. Using logistic regression, we assessed the association of the SAS with the decision to admit a patient directly to the ICU after surgery.

RESULTS

The cohort consisted of 8501 patients, with 72.7% having an SAS of 7 to 10 and <5% an SAS of 0 to 4. A total of 8.7% of patients were transferred immediately to the ICU postoperatively. After multivariate adjustment, there was a strong association between the SAS and the decision to admit a patient to the ICU (adjusted odds ratio 14.41 [95% confidence interval {CI}, 6.88-30.19, P < 0.001] for SAS 0-2, 4.42 [95% CI, 3.19-6.13, P < 0.001] for SAS 3-4, and 2.60 [95% CI, 2.08-3.24, P < 0.001] for SAS 5-6 compared with SAS 7-8).

CONCLUSIONS

The SAS is strongly associated with clinical decisions regarding immediate ICU admission after high-risk intraabdominal surgery. These results provide an initial step toward understanding whether intraoperative hemodynamics and blood loss influence ICU triage for postsurgical patients.