Application of machine learning models to biomedical and information system signals from critically ill adults

BACKGROUND

Machine learning derived notifications for impending episodes of hemodynamic instability (HD) and respiratory failure (RF) events are interesting because they can alert clinicians in time to intervene before these complications occur.

STUDY QUESTION

Do machine learning alerts, telemedicine system generated alerts or biomedical monitors have superior performance for predicting episodes of intubation or administration of vasopressors?

STUDY DESIGN AND METHODS

A machine learning (ML) algorithm was trained to predict intubation and vasopressor initiation events among critically ill adults. Its performance was compared to biomedical monitor alarms and telemedicine system alerts.

RESULTS

Machine learning (ML) notifications were substantially more accurate, precise, with 50-fold lower alarm burden than telemedicine system (TS) alerts for predicting vasopressor initiation and intubation events. ML notifications of internal validation cohorts demonstrated similar performance for independent academic medical center external validation and COVID-19 cohorts. Characteristics were also measured for a control group of recent patients that validated event detection methods and compared TS alert and (BM) biomedical monitor alarm performance. The TS test characteristics were substantially better, with 10-fold less alarm burden, than BM alarms. The accuracy of ML alerts (0.87-0.94) was in the range of other clinically actionable tests; the accuracy of TS (0.28-0.53) and BM (0.019-0.028) alerts were not. Overall test performance (F-scores) for ML notifications were more than 5-fold higher than for TS alerts which were higher than those of BM alarms.

INTERPRETATION

Machine learning derived notifications for clinically actioned HD and RF events represent an advance because the magnitude of the differences of accuracy, precision, misclassification rate, and pre-event lead time are large enough to allow more proactive care and have markedly lower frequency and interruption of bedside clinician work flows.

Impact of a switch to immediate release on the patient viewing of diagnostic test results in an online portal at an academic medical center

Patient portals allow patients to access their personal health information. The 21st Century Cures Act in the United States sought to eliminate 'information blocking', requiring timely release upon request of electronic health information including diagnostic test results. Some health systems, including the one in the present study, chose a systematic switch to immediate release of all or nearly all diagnostic test results to patient portals as part of compliance with the Cures Act. Our primary objective was to study changes in the time to view test results by patients before and after implementation of Cures Act-related changes. This retrospective pre-post study included data from two 10-month time periods before and after implementation of Cures Act-related changes at an academic medical center. The study included all patients (adult and pediatric) with diagnostic testing (laboratory and imaging) performed in the outpatient, inpatient, or emergency department settings. Between February 9, 2020 and December 9, 2021, there was a total of 3 809 397 diagnostic tests from 204 605 unique patients (3 320 423 tests for adult patients; 488 974 for pediatric patients). Overall, 56.5% (115 627) of patients were female, 84.1% (172 048) white, and 96.5% (197 517) preferred English as primary language. The odds of viewing test results within 1 and 30 days after portal release increased monthly throughout both time periods before and after the Cures Act for all patients. The rate of increase was significantly higher after implementation only in the subgroup of tests belonging to adult patients with active MyChart accounts. Immediate release shifted a higher proportion of result/report release to weekends (3.2% pre-Cures vs 15.3% post-Cures), although patient viewing patterns by day of week and time of day were similar before and after immediate release changes. The switch to immediate release of diagnostic test results to the patient portal resulted in a higher fraction of results viewed within 1 day across outpatient, inpatient, and emergency department settings.

eARDS: A multi-center validation of an interpretable machine learning algorithm of early onset Acute Respiratory Distress Syndrome (ARDS) among critically ill adults with COVID-19

We present an interpretable machine learning algorithm called ‘eARDS’ for predicting ARDS in an ICU population comprising COVID-19 patients, up to 12-hours before satisfying the Berlin clinical criteria. The analysis was conducted on data collected from the Intensive care units (ICU) at Emory Healthcare, Atlanta, GA and University of Tennessee Health Science Center, Memphis, TN and the Cerner^® Health Facts Deidentified Database, a multi-site COVID-19 EMR database. The participants in the analysis consisted of adults over 18 years of age. Clinical data from 35,804 patients who developed ARDS and controls were used to generate predictive models that identify risk for ARDS onset up to 12-hours before satisfying the Berlin criteria. We identified salient features from the electronic medical record that predicted respiratory failure among this population. The machine learning algorithm which provided the best performance exhibited AUROC of 0.89 (95% CI = 0.88–0.90), sensitivity of 0.77 (95% CI = 0.75–0.78), specificity 0.85 (95% CI = 085–0.86). Validation performance across two separate health systems (comprising 899 COVID-19 patients) exhibited AUROC of 0.82 (0.81–0.83) and 0.89 (0.87, 0.90). Important features for prediction of ARDS included minimum oxygen saturation (SpO₂), standard deviation of the systolic blood pressure (SBP), O₂ flow, and maximum respiratory rate over an observational window of 16-hours. Analyzing the performance of the model across various cohorts indicates that the model performed best among a younger age group (18–40) (AUROC = 0.93 [0.92–0.94]), compared to an older age group (80+) (AUROC = 0.81 [0.81–0.82]). The model performance was comparable on both male and female groups, but performed significantly better on the severe ARDS group compared to the mild and moderate groups. The eARDS system demonstrated robust performance for predicting COVID19 patients who developed ARDS at least 12-hours before the Berlin clinical criteria, across two independent health systems.

Characteristics and Risk Factors of Hospitalized and Nonhospitalized COVID-19 Patients, Atlanta, Georgia, USA, March-April 2020

We compared the characteristics of hospitalized and nonhospitalized patients who had coronavirus disease in Atlanta, Georgia, USA. We found that risk for hospitalization increased with a patient’s age and number of concurrent conditions. We also found a potential association between hospitalization and high hemoglobin A1c levels in persons with diabetes.

COVID-19 Clinical Phenotypes: Presentation and Temporal Progression of Disease in a Cohort of Hospitalized Adults in Georgia, United States

BACKGROUND

The epidemiological features and outcomes of hospitalized adults with coronavirus disease 2019 (COVID-19) have been described; however, the temporal progression and medical complications of disease among hospitalized patients require further study. Detailed descriptions of the natural history of COVID-19 among hospitalized patients are paramount to optimize health care resource utilization, and the detection of different clinical phenotypes may allow tailored clinical management strategies.

METHODS

This was a retrospective cohort study of 305 adult patients hospitalized with COVID-19 in 8 academic and community hospitals. Patient characteristics included demographics, comorbidities, medication use, medical complications, intensive care utilization, and longitudinal vital sign and laboratory test values. We examined laboratory and vital sign trends by mortality status and length of stay. To identify clinical phenotypes, we calculated Gower's dissimilarity matrix between each patient's clinical characteristics and clustered similar patients using the partitioning around medoids algorithm.

RESULTS

One phenotype of 6 identified was characterized by high mortality (49%), older age, male sex, elevated inflammatory markers, high prevalence of cardiovascular disease, and shock. Patients with this severe phenotype had significantly elevated peak C-reactive protein creatinine, D-dimer, and white blood cell count and lower minimum lymphocyte count compared with other phenotypes (P < .01, all comparisons).

CONCLUSIONS

Among a cohort of hospitalized adults, we identified a severe phenotype of COVID-19 based on the characteristics of its clinical course and poor prognosis. These findings need to be validated in other cohorts, as improved understanding of clinical phenotypes and risk factors for their development could help inform prognosis and tailored clinical management for COVID-19.

Timing of Intubation and Mortality Among Critically Ill Coronavirus Disease 2019 Patients: A Single-Center Cohort Study

OBJECTIVES

Increasing time to mechanical ventilation and high-flow nasal cannula use may be associated with mortality in coronavirus disease 2019. We examined the impact of time to intubation and use of high-flow nasal cannula on clinical outcomes in patients with coronavirus disease 2019.

DESIGN

Retrospective cohort study.

SETTING

Six coronavirus disease 2019-specific ICUs across four university-affiliated hospitals in Atlanta, Georgia.

PATIENTS

Adults with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection who received high-flow nasal cannula or mechanical ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among 231 patients admitted to the ICU, 109 (47.2%) were treated with high-flow nasal cannula and 97 (42.0%) were intubated without preceding high-flow nasal cannula use. Of those managed with high-flow nasal cannula, 78 (71.6%) ultimately received mechanical ventilation. In total, 175 patients received mechanical ventilation; 44.6% were female, 66.3% were Black, and the median age was 66 years (interquartile range, 56-75 yr). Seventy-six patients (43.4%) were intubated within 8 hours of ICU admission, 57 (32.6%) between 8 and 24 hours of admission, and 42 (24.0%) greater than or equal to 24 hours after admission. Patients intubated within 8 hours were more likely to have diabetes, chronic comorbidities, and higher admission Sequential Organ Failure Assessment scores. Mortality did not differ by time to intubation (≤ 8 hr: 38.2%; 8-24 hr: 31.6%; ≥ 24 hr: 38.1%; p = 0.7), and there was no association between time to intubation and mortality in adjusted analysis. Similarly, there was no difference in initial static compliance, duration of mechanical ventilation, or ICU length of stay by timing of intubation. High-flow nasal cannula use prior to intubation was not associated with mortality.

CONCLUSIONS

In this cohort of critically ill patients with coronavirus disease 2019, neither time from ICU admission to intubation nor high-flow nasal cannula use were associated with increased mortality. This study provides evidence that coronavirus disease 2019 respiratory failure can be managed similarly to hypoxic respiratory failure of other etiologies.

Predictors at admission of mechanical ventilation and death in an observational cohort of adults hospitalized with COVID-19

Background

Coronavirus disease (COVID-19) can cause severe illness and death. Predictors of poor outcome collected on hospital admission may inform clinical and public health decisions.

Methods

We conducted a retrospective observational cohort investigation of 297 adults admitted to eight academic and community hospitals in Georgia, United States, during March 2020. Using standardized medical record abstraction, we collected data on predictors including admission demographics, underlying medical conditions, outpatient antihypertensive medications, recorded symptoms, vital signs, radiographic findings, and laboratory values. We used random forest models to calculate adjusted odds ratios (aORs) and 95% confidence intervals (CI) for predictors of invasive mechanical ventilation (IMV) and death.

Results

Compared with age <45 years, ages 65–74 years and ≥75 years were predictors of IMV (aOR 3.12, CI 1.47–6.60; aOR 2.79, CI 1.23–6.33) and the strongest predictors for death (aOR 12.92, CI 3.26–51.25; aOR 18.06, CI 4.43–73.63). Comorbidities associated with death (aORs from 2.4 to 3.8, p <0.05) included end-stage renal disease, coronary artery disease, and neurologic disorders, but not pulmonary disease, immunocompromise, or hypertension. Pre-hospital use vs. non-use of angiotensin receptor blockers (aOR 2.02, CI 1.03–3.96) and dihydropyridine calcium channel blockers (aOR 1.91, CI 1.03–3.55) were associated with death.

Conclusions

After adjustment for patient and clinical characteristics, older age was the strongest predictor of death, exceeding comorbidities, abnormal vital signs, and laboratory test abnormalities. That coronary artery disease, but not chronic lung disease, was associated with death among hospitalized patients warrants further investigation, as do associations between certain antihypertensive medications and death.

ICU and Ventilator Mortality Among Critically Ill Adults With Coronavirus Disease 2019

OBJECTIVES

To determine mortality rates among adults with critical illness from coronavirus disease 2019.

DESIGN

Observational cohort study of patients admitted from March 6, 2020, to April 17, 2020.

SETTING

Six coronavirus disease 2019 designated ICUs at three hospitals within an academic health center network in Atlanta, Georgia, United States.

PATIENTS

Adults greater than or equal to 18 years old with confirmed severe acute respiratory syndrome-CoV-2 disease who were admitted to an ICU during the study period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among 217 critically ill patients, mortality for those who required mechanical ventilation was 35.7% (59/165), with 4.8% of patients (8/165) still on the ventilator at the time of this report. Overall mortality to date in this critically ill cohort is 30.9% (67/217) and 60.4% (131/217) patients have survived to hospital discharge. Mortality was significantly associated with older age, lower body mass index, chronic renal disease, higher Sequential Organ Failure Assessment score, lower PaO2/FIO2 ratio, higher D-dimer, higher C-reactive protein, and receipt of mechanical ventilation, vasopressors, renal replacement therapy, or vasodilator therapy.

CONCLUSIONS

Despite multiple reports of mortality rates exceeding 50% among critically ill adults with coronavirus disease 2019, particularly among those requiring mechanical ventilation, our early experience indicates that many patients survive their critical illness.

Characteristics Associated with Hospitalization Among Patients with COVID-19 - Metropolitan Atlanta, Georgia, March-April 2020

The first reported U.S. case of coronavirus disease 2019 (COVID-19) was detected in January 2020 (1). As of June 15, 2020, approximately 2 million cases and 115,000 COVID-19-associated deaths have been reported in the United States.* Reports of U.S. patients hospitalized with SARS-CoV-2 infection (the virus that causes COVID-19) describe high proportions of older, male, and black persons (2-4). Similarly, when comparing hospitalized patients with catchment area populations or nonhospitalized COVID-19 patients, high proportions have underlying conditions, including diabetes mellitus, hypertension, obesity, cardiovascular disease, chronic kidney disease, or chronic respiratory disease (3,4). For this report, data were abstracted from the medical records of 220 hospitalized and 311 nonhospitalized patients aged ≥18 years with laboratory-confirmed COVID-19 from six acute care hospitals and associated outpatient clinics in metropolitan Atlanta, Georgia. Multivariable analyses were performed to identify patient characteristics associated with hospitalization. The following characteristics were independently associated with hospitalization: age ≥65 years (adjusted odds ratio [aOR] = 3.4), black race (aOR = 3.2), having diabetes mellitus (aOR = 3.1), lack of insurance (aOR = 2.8), male sex (aOR = 2.4), smoking (aOR = 2.3), and obesity (aOR = 1.9). Infection with SARS-CoV-2 can lead to severe outcomes, including death, and measures to protect persons from infection, such as staying at home, social distancing (5), and awareness and management of underlying conditions should be emphasized for those at highest risk for hospitalization with COVID-19. Measures that prevent the spread of infection to others, such as wearing cloth face coverings (6), should be used whenever possible to protect groups at high risk. Potential barriers to the ability to adhere to these measures need to be addressed.

ICU and ventilator mortality among critically ill adults with COVID-19

We report preliminary data from a cohort of adults admitted to COVID-designated intensive care units from March 6 through April 17, 2020 across an academic healthcare system. Among 217 critically ill patients, mortality for those who required mechanical ventilation was 29.7% (49/165), with 8.5% (14/165) of patients still on the ventilator at the time of this report. Overall mortality to date in this critically ill cohort is 25.8% (56/217), and 40.1% (87/217) patients have survived to hospital discharge. Despite multiple reports of mortality rates exceeding 50% among critically ill adults with COVID-19, particularly among those requiring mechanical ventilation, our early experience indicates that many patients survive their critical illness.

Utilized or Underutilized: A Qualitative Analysis of Building Coherence During Early Implementation of a Tele-Intensive Care Unit

Background: Generating, reading, or interpreting data is a component of Telemedicine-Intensive Care Unit (Tele-ICU) utilization that has not been explored in the literature. Introduction: Using the idea of "coherence," a construct of Normalization Process Theory, we describe how intensive care unit (ICU) and Tele-ICU staff made sense of their shared work and how they made use of Tele-ICU together. Materials and Methods: We interviewed ICU and Tele-ICU staff involved in the implementation of Tele-ICU during site visits to a Tele-ICU hub and 3 ICUs, at preimplementation (43 interviews with 65 participants) and 6 months postimplementation (44 interviews with 67 participants). Data were analyzed using deductive coding techniques and lexical searches. Results: In the early implementation of Tele-ICU, ICU and Tele-ICU staff lacked consensus about how to share information and consequently how to make use of innovations in data tracking and interpretation offered by the Tele-ICU (e.g., acuity systems). Attempts to collaborate and create opportunities for utilization were supported by quality improvement (QI) initiatives. Discussion: Characterizing Tele-ICU utilization as an element of a QI process limited how ICU staff understood Tele-ICU as an innovation. It also did not promote an understanding of how the Tele-ICU used data and may therefore attenuate the larger promise of Tele-ICU as a potential tool for leveraging big data in critical care. Conclusions: Shared data practices lay the foundation for Tele-ICU program utilization but raise new questions about how the promise of big data can be operationalized for bedside ICU staff.

The effect of timing of initiation of renal replacement therapy on mortality: A retrospective case-control study

Purpose

To determine if earlier initiation of renal replacement therapy (RRT) is associated with improved survival in patients with severe acute kidney injury.

Methods

We performed a retrospective case-control study of propensity-matched groups with multivariable logistic regression using Akaike Information Criteria to adjust for non-matched variables in a surgical ICU in a tertiary care hospital.

Results

We matched 169 of 205 (82%) patients with new initiation of RRT (EARLY group) to 169 similar patients who did not initiate RRT on that day (DEFERRED group). Eighteen (11%) of DEFERRED eventually received RRT before discharge. By univariate analysis, ICU mortality was higher in EARLY (n = 60 (36%) vs. n = 23 (14%), p < 0.001) as was hospital mortality (n = 73 (43%) vs. n = 44 (26%), p = 0.001). Of the 18 RRT patients in DEFERRED, 12 (67%) died in ICU and 13 (72%) in hospital. After propensity matching and logistic regression, we found that EARLY initiation of RRT was associated with a more than doubling of ICU mortality (aOR = 2.310, 95% confidence interval = 1.254-4.257, p = 0.007). However, after similar adjustment, there was no difference in hospital mortality (aOR = 1.283, 95% CI = 0.753-2.186, p = 0.360).

Conclusions

While ICU mortality was increased in the EARLY group, there was no difference in hospital mortality between EARLY and DEFERRED groups.

Sepsis information-seeking behaviors via Wikipedia between 2015 and 2018: A mixed methods retrospective observational study

Raising public awareness of sepsis, a potentially life-threatening dysregulated host response to infection, to hasten its recognition has become a major focus of physicians, investigators, and both non-governmental and governmental agencies. While the internet is a common means by which to seek out healthcare information, little is understood about patterns and drivers of these behaviors. We sought to examine traffic to Wikipedia, a popular and publicly available online encyclopedia, to better understand how, when, and why users access information about sepsis. Utilizing pageview traffic data for all available language localizations of the sepsis and septic shock pages between July 1, 2015 and June 30, 2018, significantly outlying daily pageview totals were identified using a seasonal hybrid extreme studentized deviate approach. Consecutive outlying days were aggregated, and a qualitative analysis was undertaken of print and online news media coverage to identify potential correlates. Traffic patterns were further characterized using paired referrer to resource (i.e. clickstream) data, which were available for a temporal subset of the pageviews. Of the 20,557,055 pageviews across 65 linguistic localizations, 47 of the 1,096 total daily pageview counts were identified as upward outliers. After aggregating sequential outlying days, 25 epochs were examined. Qualitative analysis identified at least one major news media correlate for each, which were typically related to high-profile deaths from sepsis and, less commonly, awareness promotion efforts. Clickstream analysis suggests that most sepsis and septic shock Wikipedia pageviews originate from external referrals, namely search engines. Owing to its granular and publicly available traffic data, Wikipedia holds promise as a means by which to better understand global drivers of online sepsis information seeking. Further characterization of user engagement with this information may help to elucidate means by which to optimize the visibility, content, and delivery of awareness promotion efforts.

Highly visible sepsis publications from 2012 to 2017: Analysis and comparison of altmetrics and bibliometrics

PURPOSE

We sought to delineate highly visible publications related to sepsis. Within these subsets, elements of altmetrics performance, including mentions on Twitter, and the correlation between altmetrics and conventional citation counts were ascertained.

MATERIALS AND METHODS

Three subsets of sepsis publications from 2012 to 2017 were synthesized by the overall Altmetric.com attention score, number of mentions by unique Twitter users, and conventional citation counts. For these subsets, geolocated Twitter activity was plotted on a choropleth, the lag between publication date and altmetrics mentions was characterized, and correlations were examined between altmetrics performance and normalized conventional citation counts.

RESULTS

Of 57,152 PubMed query results, Altmetric.com data was available for 28,344 (49.6%). The top 50 publications by Altmetric.com attention score and Twitter attention represented a mix of original research and other types of work, garnering attention from Twitter users in 143 countries that was highly contemporaneous with publication. Altmetrics performance and conventional citation counts were poorly correlated.

CONCLUSIONS

While unreliable to gauge impact or future citation potential, altmetrics may be valuable for parties who wish to detect and drive public awareness of research findings and may enable researchers to dynamically explore the reach of their work in novel dimensions.

Modes of mechanical ventilation vary between hospitals and intensive care units within a university healthcare system: a retrospective observational study

Objective

As evidence-based guidance to aid clinicians with mechanical ventilation mode selection is scant, we sought to characterize the epidemiology thereof within a university healthcare system and hypothesized that nonconforming approaches could be readily identified. We conducted an exploratory retrospective observational database study of routinely recorded mechanical ventilation parameters between January 1, 2010 and December 31, 2016 from 12 intensive care units. Mode epoch count proportions were examined using Chi squared and Fisher exact tests as appropriate on an inter-unit basis with outlier detection for two test cases via post hoc pairwise analyses of a binomial regression model.

Results

Final analysis included 559,734 mode epoch values. Significant heterogeneity was demonstrated between individual units (P < 0.05 for all comparisons). One unit demonstrated heightened utilization of high-frequency oscillatory ventilation, and three units demonstrated frequent synchronized intermittent mandatory ventilation utilization. Assist control ventilation was the most commonly recorded mode (51%), followed by adaptive support ventilation (23.1%). Volume-controlled modes were about twice as common as pressure-controlled modes (64.4% versus 35.6%). Our methodology provides a means by which to characterize the epidemiology of mechanical ventilation approaches and identify nonconforming practices. The observed variability warrants further clinical study about contributors and the impact on relevant outcomes.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3534-z) contains supplementary material, which is available to authorized users.

Global trends in the awareness of sepsis: insights from search engine data between 2012 and 2017

BACKGROUND

Sepsis is an established global health priority with high mortality that can be curtailed through early recognition and intervention; as such, efforts to raise awareness are potentially impactful and increasingly common. We sought to characterize trends in the awareness of sepsis by examining temporal, geographic, and other changes in search engine utilization for sepsis information-seeking online.

METHODS

Using time series analyses and mixed descriptive methods, we retrospectively analyzed publicly available global usage data reported by Google Trends (Google, Palo Alto, CA, USA) concerning web searches for the topic of sepsis between 24 June 2012 and 24 June 2017. Google Trends reports aggregated and de-identified usage data for its search products, including interest over time, interest by region, and details concerning the popularity of related queries where applicable. Outlying epochs of search activity were identified using autoregressive integrated moving average modeling with transfer functions. We then identified awareness campaigns and news media coverage that correlated with epochs of significantly heightened search activity.

RESULTS

A second-order autoregressive model with transfer functions was specified following preliminary outlier analysis. Nineteen significant outlying epochs above the modeled baseline were identified in the final analysis that correlated with 14 awareness and news media events. Our model demonstrated that the baseline level of search activity increased in a nonlinear fashion. A recurrent cyclic increase in search volume beginning in 2012 was observed that correlates with World Sepsis Day. Numerous other awareness and media events were correlated with outlying epochs. The average worldwide search volume for sepsis was less than that of influenza, myocardial infarction, and stroke.

CONCLUSIONS

Analyzing aggregate search engine utilization data has promise as a mechanism to measure the impact of awareness efforts. Heightened information-seeking about sepsis occurs in close proximity to awareness events and relevant news media coverage. Future work should focus on validating this approach in other contexts and comparing its results to traditional methods of awareness campaign evaluation.

Influence of non-invasive blood pressure measurement intervals on the occurrence of intra-operative hypotension

The American Society of Anesthesiologists Standards for Basic Monitoring recommends blood pressure (BP) measurement every 5 min. Research has shown distractions or technical factors can cause prolonged measurement intervals exceeding 5 min. We investigated the relationship between prolonged non-invasive BP (NIBP) measurement interval and the incidence of hypotension, detected post-interval. Our secondary outcome was to determine independent predictors of these prolonged NIBP measurement intervals. Retrospective data were analyzed from 139,509 general anesthesia cases from our institution's Anesthesia Information Management System (AIMS). Absolute hypotension (AH) was defined a priori as a systolic BP < 80 mmHg and relative hypotension (RH) was defined as a 40% decrease in systolic BP from the preoperative baseline. Odds ratios (OR) with 95% confidence intervals and Pearson's Chi square Test reported the association of prolonged NIBP measurement intervals on hypotension detected post-NIBP measurement interval. Logistic regression models were developed to determine independent predictors of NIBP measurement intervals. The analysis revealed that NIBP measurement intervals greater than 6 and 10 min are associated with an approximately four times higher incidence of a patient transitioning into hypotension (AH/RH > 6 min OR 4.0 / 3.6; AH/RH > 10 min OR 4.3 / 3.9; p < 0.001). A key finding was that the "> 10-minute AH model" indicated that age 41-80, increased co-morbidity profile, obesity and turning (repositioning) of the operative room table were significant predictors of prolonged NIBP measurement intervals (p < 0.001). While we do not suggest NIBP measurement intervals cause hypotension, intervals greater than 6 and 10 min are associated with a fourfold increase in the propensity of an undetected transition into both RH or AH. These data support current monitoring guidelines.

Remote cannulation and extracorporeal membrane oxygenation transport is safe in a newly established program

Extracorporeal membrane oxygenation (ECMO) has become an increasingly utilized modality for the support of patients with severe cardiac or pulmonary dysfunction. Unfortunately, the costs and expertise required to maintain a formal ECMO program preclude the vast majority of hospitals from employing such technology routinely. These barriers to implementation of an effective ECMO program highlight the importance of the safe transport of patients in need of extracorporeal support. While many centers with extensive expertise in the management of patients on extracorporeal support have demonstrated their ability to transport those same patients, the ability of new ECMO programs to provide such transportation remains poorly studied. We established an ECMO program at our institution and immediately provided equipment and personnel to transport patients in need of or receiving extracorporeal support to our institution. Overall, we found that 13 out of 28 patients transported to our institution on ECMO or for consideration of ECMO support during the first 15 months of the program survived to hospital discharge. During that period, four incidents associated with patient transport occurred but none were related to ECMO support or adversely affected patient outcome. These observations demonstrate that new ECMO programs can safely and reliably transport patients on or in need of extracorporeal support.

Clinical and billing review of extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a temporary technique for providing life support for cardiac dysfunction, pulmonary dysfunction, or both. The two forms of ECMO, veno-arterial (VA) and veno-venous (VV), are used to support cardiopulmonary and pulmonary dysfunction, respectively. Historically, ECMO was predominantly used in the neonatal and pediatric populations, as early adult studies failed to improve outcomes. ECMO has become far more common in the adult population because of positive results in published case series and clinical trials during the 2009 influenza A(H1N1) pandemic in 2009 to 2010. Advances in technology that make the technique much easier to implement likely fueled the renewed interest. Although exact criteria for ECMO are not available, patients who are good candidates are generally considered to be relatively young and suffering from acute illness that is believed to be reversible or organ dysfunction that is otherwise treatable. With the increase in the use in the adult population, a number of different codes have been generated to better identify the method of support with distinctly different relative value units assigned to each code from a very simple prior coding scheme. To effectively be reimbursed for use of the technique, it is imperative that the clinician understands the new coding scheme and works with payers to determine what is incorporated into each specific code.

Temporal trends and current practice patterns for intraoperative ventilation at U.S. academic medical centers: a retrospective study

Background

Lung protective ventilation strategies utilizing lower tidal volumes per predicted body weight (PBW) and positive end-expiratory pressure (PEEP) have been suggested to be beneficial in a variety of surgical populations. Recent clinical studies have used control groups ventilated with high tidal volumes without PEEP based on the assumption that this reflects current clinical practice. We hypothesized that ventilation strategies have changed over time, that most anesthetics in U.S. academic medical centers are currently performed with lower tidal volumes, and that most receive PEEP.

Methods

Intraoperative data were pooled for adults undergoing general anesthesia with tracheal intubation. Median tidal volumes per kilogram of PBW were categorized as > 10, 8–10 and < 8 mL per kg of PBW. The percentages of cases in 2013 that were performed with median tidal volumes < 8 mL per kg of PBW and PEEP were determined. As a secondary analysis, a proportional odds model using institution, year, height, weight and gender determined the relative associations of these factors using categorical and interquartile odds ratios.

Results

295,540 cases were analyzed from 5 institutions over a period of 10 years. In 2013, 59.3% of cases used median tidal volumes < 8 mL per kg of PBW, 83.3% used PEEP, and 51.0% used both. Of those cases with PEEP, 60.9% used a median pressure of ≥ 5 cmH₂O. Predictors of lower categories of tidal volumes included height (odds ratio (OR) 10.83, 95% confidence interval [10.50, 11.16]), institution (lowest OR 0.98 [0.96, 1.00], highest OR 9.63 [9.41, 9.86]), year (lowest OR 1.32 [1.21, 1.44], highest OR 6.31 [5.84, 6.82]), male gender (OR 1.10 [1.07, 1.12]), and weight (OR 0.30 [0.29, 0.31]).

Conclusion

Most general anesthetics with tracheal intubation at the institutions surveyed are currently performed with a median tidal volume < 8 mL per kg of PBW, most are managed with PEEP of ≥ 5 cmH₂O and approximately half utilize both. Given the diversity of the institutions included, this is likely reflective of practice in U.S. academic medical centers. The utilization of higher tidal volumes without PEEP in control groups for clinical research studies should be reconsidered.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-015-0010-3) contains supplementary material, which is available to authorized users.

Replacement of anesthesia machines improves intraoperative ventilation parameters associated with the development of acute respiratory distress syndrome

Background

The impact of anesthetic equipment on clinical practice parameters associated with development of acute respiratory distress syndrome (ARDS) has not been extensively studied. We hypothesized a change in anesthesia machines would be associated with parameters associated with lower rates of ARDS.

Methods

We performed a retrospective cohort study on a subset of data used to evaluate intraoperative ventilation. Patients included adults receiving a non-cardiac, non-thoracic, non-transplant, non-trauma, general anesthetic between 2/1/05, and 3/31/09 at the University of Michigan. Existing anesthesia machines (Narkomed IIb, Drager) were exchanged for new equipment (Aisys, General Electric). The initial subset compared the characteristics of patients anesthetized between 12/1/06 and 1/31/07 (pre) with those between 4/1/07 and 5/30/07 (post). An extended subset examined cases two years pre and post exchange. Using the standard predicted body weight (PBW), we calculated and compared the tidal volume (total Vt and mL/kg PBW) as well as positive end-expiratory pressure (PEEP), peak inspiratory pressure (PIP), Delta P (PIP-PEEP), and FiO2.

Results

A total of 1,414 patients were included in the 2-month pre group and 1,635 patients included in the post group. Comparison of ventilation characteristics found statistically significant differences in median (pre v post): PIP (26 ± 6 v 21 ± 6 cmH2O,p < .001), Delta P (24 ± 6 v 19 ± 6 cmH2O, p < .001), Vt (588 ± 139 v 562 ± 121 ml, p < 0.001; 9.3 ± 2.2 v 9.0 ± 1.9 ml/kg predicted body weight, p < .001), FiO2 (0.57 ± 0.17 v 0.52 ± 0.18, p < .001). Groups did not differ in age, ASA category, PBW, or BMI. The two year subgroup had similar parameters. Risk adjustment resulted in minimal differences in the analysis. New anesthesia machines were associated with a non-statistically significant reduction in postoperative ARDS.

Conclusions

In this study, a change in ventilator management was associated with an anesthesia machine exchange. The smaller Vt and lower PIP noted in the post group may imply a lower risk of volutrauma and barotrauma, which may be significant in at-risk populations. However, there was not a statistically significant reduction in the incidence of post-operative ARDS.

Contemporary ventilator management in patients with and at risk of ALI/ARDS

BACKGROUND

Ventilator practices in patients at risk for acute lung injury (ALI) and ARDS are unclear. We examined factors associated with choice of set tidal volumes (VT), and whether VT < 8 mL/kg predicted body weight (PBW) relates to the development of ALI/ARDS.

METHODS

We performed a secondary analysis of a multicenter cohort of adult subjects at risk of lung injury with and without ALI/ARDS at onset of invasive ventilation. Descriptive statistics were used to describe ventilator practices in specific settings and ALI/ARDS risk groups. Logistic regression analysis was used to determine the factors associated with the use of VT < 8 mL/kg PBW and the relationship of VT to ALI/ARDS development and outcome.

RESULTS

Of 829 mechanically ventilated patients, 107 met the criteria for ALI/ARDS at time of intubation, and 161 developed ALI/ARDS after intubation (post-intubation ALI/ARDS). There was significant intercenter variability in initial ventilator settings, and in the incidence of ALI/ARDS and post-intubation ALI/ARDS. The median VT was 7.96 (IQR 7.14-8.94) mL/kg PBW in ALI/ARDS subjects, and 8.45 (IQR 7.50-9.55) mL/kg PBW in subjects without ALI/ARDS (P = .004). VT decreased from 8.40 (IQR 7.38-9.37) mL/kg PBW to 7.97 (IQR 6.90-9.23) mL/kg PBW (P < .001) in those developing post-intubation ALI/ARDS. Among subjects without ALI/ARDS, VT ≥ 8 mL/kg PBW was associated with shorter height and higher body mass index, while subjects with pneumonia were less likely to get ≥ 8 mL/kg PBW. Initial VT ≥ 8 mL/kg PBW was not associated with the post-intubation ALI/ARDS (adjusted odds ratio 1.30, 95% CI 0.74-2.29) or worse outcomes. Post-intubation ALI/ARDS subjects had mortality similar to subjects intubated with ALI/ARDS.

CONCLUSIONS

Clinicians seem to respond to ALI/ARDS with lower initial VT. Initial VT, however, was not associated with the development of post-intubation ALI/ARDS or other outcomes.

United States Critical Illness and Injury Trials Group

The United States Critical Illness and Injury Trials (USCIIT) Group is an inclusive, grassroots "network of networks" with the dual missions of fostering investigator-initiated hypothesis testing and developing recommendations for strategic plans at a national level. The USCIIT Group's transformational approach enlists multidisciplinary investigative teams across institutions, critical illness and injury professional organizations, federal agencies that fund clinical and translational research, and industry partners. The USCIIT Group is endorsed by all major critical illness and injury professional organizations spanning the specialties of anesthesiology, emergency medicine, internal medicine, neurology, nursing, pediatrics, pharmacy and nutrition, surgery and trauma, and respiratory and physical therapy. Recent successes provide the opportunity to significantly increase the dialogue necessary to advance clinical and translational research on behalf of our community. More than 200 investigators are now involved across > 30 academic and community hospitals. Collectively, USCIIT Group investigators have enrolled > 10,000 patients from academic and community hospitals in studies during the last 3 years. To keep our readership "ahead of the curve," this article provides a vision for critical illness and injury research based on (1) programmatic organization of large-scale, multicentered collaborative studies and (2) annual strategic planning at a national scale across disciplines and stakeholders.

A bibliometric search of citation classics in anesthesiology

BACKGROUND

Articles cited counts are catalogued and help identify landmark papers. This study provides a citation classics of anesthesiology literature using the framework of subspecialties to provide a review of well-developed areas of research in anesthesiology.

METHODS

A comprehensive list of the most-cited articles in anesthesia was compiled using a bibliometric database and general search terms such as "anesthesia" as well as subspecialty-specific search terms. Queries were reviewed for relevance to anesthesiology practice, categorized by subspecialty, and ranked according to their citation counts.

RESULTS

The database resulted in 2519 articles published between 1945 and 2008. The specialty areas most represented were chronic pain medicine (11%), pharmacology (9%), and pain sciences (9%).

CONCLUSIONS

This citations classic allows for advances in anesthesiology and its subspecialties to be highlighted as well to provide useful manuscripts to guide patient care, direct future research, and serve as sources for future academic pursuit.

A case of malignant hyperthermia captured by an anesthesia information management system

Many cases of malignant hyperthermia triggered by volatile anesthetic agents have been described. However, to our knowledge, there has not been a report describing the precise changes in physiologic data of a human suffering from this process. Here we describe a case of malignant hyperthermia in which monitoring information was frequently and accurately captured by an anesthesia information management system.

Evaluation of a novel supplement to reduce blood glucose through the use of a modified oral glucose tolerance test

Elevated blood glucose is a major component in metabolic syndrome and pre-diabetes, sometimes leading to type 2 diabetes mellitus (DM II). Additionally, it may lead to adipose deposits when left elevated for long periods. The epidemiology of DM II clearly shows that uncontrolled blood glucose levels leads to many adverse conditions including heart disease, retinal damage, renal failure, erectile dysfunction, and other significant medical conditions. Here we conducted a single-center, prospective, randomized, double-blinded, placebo-controlled, parallel-group- clinical trial of a nutraceutical supplement vs. placebo to measure its glucose lowering effect in generally healthy adults before and after a simple sugars meal. Subjects reported to the test clinic on multiple days to receive placebo or treatment, a simple sugars meal, as well as pre-and postprandial blood glucose measurement (modified oral glucose tolerance test). Each subject served as his or her own control and thirty-one subjects completed the trial with at least one oral glucose tolerance test (OGTT) with the nutraceutical supplement and placebo. Statistical analysis revealed the nutraceutical supplement significantly lowered postprandial glucose levels by 36% and 59% at 45 and 60 minutes, respectively (***P<.001). The study was limited by its composition of primarily overweight females. Future studies will be required over longer periods in more heterogeneous and larger groups to determine the long-term effect of this supplement on blood glucose levels in terms of prophylaxis or treatment for DM II.

Pulse oximetry saturation to fraction inspired oxygen ratio as a measure of hypoxia under general anesthesia and the influence of positive end-expiratory pressure

PURPOSE

In ICU patients with acute lung injury, the pulse oximetry saturation (Spo(2)) to fraction of inspired oxygen (Fio(2)) (S/F) ratio is a reliable surrogate measure for the P/F (Pao(2)/Fio(2)) ratio. Our goal was to determine the correlation of the S/F to the P/F in a large sample of patients undergoing general anesthesia and the influence of positive end-expiratory pressure (PEEP) on this measure.

METHODS

We studied adult general anesthetics performed with arterial blood gas analysis. Intraoperative data were collected from an anesthesia information system. The S/F ratios corresponding to P/F ratios of 300 were determined.

RESULTS

A total of 4439 values were collected. Linear correlation between S/F and P/F was identified (r = 0.46; P < .01) with a P/F of 300 corresponding to an S/F of 206. The correlation was stronger in patients with 5 to 9 cm PEEP (r = 0.52; P < .01), more than 9 cm H(2)O PEEP (r = 0.68; P < .01), and a P/F ratio of 300 or less (r = 0.61; P < .01).

CONCLUSION

The S/F correlates with the P/F in our cohort of patients undergoing general anesthesia, especially those ventilated with PEEP more than 9 cm H(2)O and/or with P/F less than 300. It has use as a noninvasive measure to screen for increased pulmonary dysfunction and to trend oxygenation during a general anesthetic.

A description of intraoperative ventilator management and ventilation strategies in hypoxic patients

BACKGROUND

Hypoxia is a common finding in the anesthetized patient. Although there are a variety of methods to address hypoxia, it is not well documented what strategies are used by anesthesiologists when faced with a hypoxic patient. Studies have identified that lung protective ventilation strategies have beneficial effects in both oxygenation and mortality in acute respiratory distress syndrome. We sought to describe the ventilation strategies in anesthetized patients with varying degrees of hypoxemia as defined by the Pao(2) to fraction of inspired oxygen (Fio(2)) (P/F) ratio.

METHODS

We conducted a review of all operations performed between January 1, 2005, and July 31, 2009, using a general anesthetic, excluding cardiac and thoracic procedures, to assess the ventilation settings that were used in patients with different P/F ratios. Patients older than 18 years who received a general anesthetic were included. Four cohorts of arterial blood gases (ABGs) were identified with P/F >300, 300 > or = P/F > 200, 200 > or = P/F > 100, 100 > or = P/F. Using the standard predicted body weight (PBW) equation, we calculated the milliliters per kilogram (mL/kg PBW) with which the patient's lungs were being ventilated. Positive end-expiratory pressure (PEEP), peak inspiratory pressures (PIPs), Fio(2), oxygen saturation (Sao(2)), and tidal volume in mL/kg PBW were compared.

RESULTS

A total of 28,706 ABGs from 11,445 operative cases met criteria for inclusion. There were 19,679 ABGs from the P/F >300 group, 5364 ABGs from the 300 > or = P/F > 200 group, 3101 ABGs from the 200 > or = P/F > 100 group, and 562 ABGs from the 100 > or = P/F group identified. A comparison of ventilation strategies found statistical significance but clinically irrelevant differences. Tidal volumes ranged between 8.64 and 9.16 and the average PEEP varied from 2.5 to 5.5 cm H(2)O. There were substantial differences in the average Fio(2) and PIP among the groups, 59% to 91% and 22 to 29 cm H(2)O, respectively.

CONCLUSION

Similar ventilation strategies in mL/kg PBW and PEEP were used among patients regardless of P/F ratio. The results of this study suggest that anesthesiologists, in general, are treating hypoxemia with higher Fio(2) and PIP. The average Fio(2) and PIP were significantly escalated depending on the P/F ratio.

Supplements of 20 microg/d cholecalciferol optimized serum 25-hydroxyvitamin D concentrations in 80% of premenopausal women in winter

The serum 25-hydroxyvitamin D [25(OH)D] response to daily supplementation with 20 microg cholecalciferol (D3) during winter in predominantly white premenopausal women living in Maine was measured and the effects of body composition and hormonal contraceptive use on baseline serum 25(OH)D concentrations and the response to supplementation were examined. A total of 112 women (22.2 +/- 3.7 y old) received placebo from March 2005 until September 2005 when they were randomized to receive either placebo or 20 microg/d D3 through February 2006. Eighty-six women completed the study. Actual mean D3 content of the supplements was 22 microg per capsule. In February 2005 the serum 25(OH)D concentration was 62.0 +/- 23.4 nmol/L (mean +/- SD). Serum 25(OH)D concentrations increased by 35.3 +/- 23.2 nmol/L from February 2005 to February 2006 in the treatment group, significantly more than the 10.9 +/- 16.9 nmol/L increase in the placebo group. Treatment group, magnitude of summer increase in 25(OH)D, estrogen dose, and baseline serum 25(OH)D concentrations, but not body fat, were significant predictors of the 1-y change in 25(OH)D concentrations used to assess the magnitude of the response to supplementation. Daily supplementation with 20 microg D3 during winter achieved optimal 25(OH)D concentrations (> or = 75 nmol/L) in 80% of participants, indicating that this dose is adequate to optimize vitamin D status in most young women in Maine.

Electronic Reminders Improve Procedure Documentation Compliance and Professional Fee Reimbursement

BACKGROUND

Medicolegal, clinical, and reimbursement needs warrant complete and accurate documentation. We sought to identify and improve our compliance rate for the documentation of arterial catheterization in the perioperative setting.

METHODS

We first reviewed 12 mo of electronic anesthesia records to establish a baseline compliance rate for arterial catheter documentation. Residents and Certified Registered Nurse Anesthetists were randomly assigned to a control group and experimental group. When surgical incision and anesthesia end were documented in the electronic record keeper, a reminder routine checked for an invasive arterial blood pressure tracing. If a case used an arterial catheter, but no procedure note was observed, the resident or Certified Registered Nurse Anesthetist assigned to the case was sent an automated alphanumeric pager and e-mail reminder. Providers in the control group received no pager or e-mail message. After 2 mo, all staff received the reminders.

RESULTS

A baseline compliance rate of 80% was observed (1963 of 2459 catheters documented). During the 2-mo study period, providers in the control group documented 152 of 202 (75%) arterial catheters, and the experimental group documented 177 of 201 (88%) arterial lines (P < 0.001). After all staff began receiving reminders, 309 of 314 arterial lines were documented in a subsequent 2 mo period (98%). Extrapolating this compliance rate to 12 mo of expected arterial catheter placement would result in an annual incremental $40,500 of professional fee reimbursement.

CONCLUSIONS

The complexity of the tertiary care process results in documentation deficiencies. Inexpensive automated reminders can drastically improve compliance without the need for complicated negative or positive feedback.

A comparison of anesthesiology resident and faculty electronic evaluations before and after implementation of automated electronic reminders

STUDY OBJECTIVE

To develop an automated e-mail reminder system to contact residents and faculty regarding incomplete evaluations. DESIGN, SETTING, INTERVENTION, AND MEASUREMENTS: In the retrospective study, two 9-month periods were evaluated representing pre- and post-introduction of the automated e-mail reminder system. Data collected contained the number of evaluations completed and the rating of residents and faculty at the University of Michigan Health System in 5 different categories on a 5-point scale.

MAIN RESULTS

The use of electronic reminders resulted in a nearly 4-fold increase in the number of resident evaluations by faculty from 1050 to 3761. Faculty completing evaluations increased from 40 (61%) to 66 (100%). The mean evaluation scores showed statistically significant but clinically negligible change for resident judgement, interpersonal skills, and intraoperative management. Resident preoperative evaluation and knowledge did not show statistically significant changes. Residents completing evaluations of faculty increased from 244 to 1798, and the number of residents completing evaluations rose from 40 (56%) to 87 (100%). There were no statistically significant changes in the evaluation of faculty except in the category of feedback.

CONCLUSION

An automated e-mail reminder system implemented to contact residents and faculty regarding incomplete evaluations for residents and faculty dramatically enhanced participation in the evaluation process.

An open system for development of derived physiologic alarms

Data from existing physiologic monitor alarms is frequently artifact. Hence, automated physiologic alarms are frequently ignored. Proprietary systems have shown that alarm sensitivity and specificity can be distinctly improved using advanced data processing techniques. We have developed an easily implemented, open system to research improved alarm systems. The technical implementation of this system is straightforward and could provide a framework for network of researchers to develop alarm algorithms.

Off-pump coronary artery bypass grafting: initial experience at one community hospital

BACKGROUND

This study reports one cardiac surgical center's experience with off-pump coronary artery bypass (OPCAB) and compares clinical risk factors and outcomes with a group of patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass at the same institution.

METHODS

Data on preoperative risk factors, intraoperative clinical markers, and postoperative outcomes were collected prospectively on all patients undergoing cardiac surgical procedures at our institution. From January 1, 1999, through October 7, 1999, 332 patients underwent OPCAB procedures at our institution. This group was compared with 445 consecutive patients undergoing CABG at the same institution during the period of January 1, 1998, through November 30, 1998.

RESULTS

The two groups were similar with respect to preoperative clinical risk factors. Intraoperative data showed OPCAB patients tended to have fewer grafts performed and had a lower frequency of multiple grafts to obtuse marginal vessels. Outcomes showed no differences in the incidence of perioperative stroke, mediastinitis, reexploration for bleeding, pulmonary complications, new renal failure, postoperative atrial fibrillation, or transfusion of blood products. Patients in the OPCAB group had fewer perioperative myocardial infarctions and lower incidence of postoperative low cardiac output syndrome. A higher percentage of OPCAB patients had surgical lengths of stay of 5 days or less. The OPCAB group tended to have a lower in-hospital mortality rate but this difference did not reach statistical significance.

CONCLUSIONS

Off-pump coronary artery bypass grafting with revascularization of all coronary artery segments is a safe and effective procedure that can be performed with equal or improved outcomes and shorter surgical lengths of stay compared with CABG with cardiopulmonary bypass.

Cytomegaloviral acalculous cholecystitis in acquired immunodeficiency syndrome patients

Abdominal pain and fever in patients with the acquired immunodeficiency syndrome (AIDS) may indicate cytomegaloviral (CMV) acalculous cholecystitis. We reviewed clinical, laboratory, and outcome data from 12 patients with CMV cholecystitis. Ten of 12 patients were homosexual males. Six patients had markedly low CD4: CD8 lymphocyte count ratios. Total leukocyte counts were normal or decreased, serum liver function tests normal or cholestatic, and only one patient had hyperbilirubinemia. Sonographic transmural gallbladder edema is typically more severe than expected for the presenting illness. Five of six patients investigated with HIDA scintigraphy had a nonvisualizing gallbladder. Open cholecystectomy had a 9.1 per cent operative morbidity and a 0 per cent mortality. Cholecystectomy is a safe and curative intervention, regardless of the immunocompromised condition of the host. Intraoperative cholangiography will identify papillary stenosis or sclerotic bile ducts as a potential cause of recurrent symptoms following surgery. A search for other sites of tissue invasion by CMV should follow cholecystectomy.

Stratification of morbidity and mortality outcome by preoperative risk factors in coronary artery bypass patients. A clinical severity score

OBJECTIVE

To relate morbidity and mortality risk to preoperative severity of illness in patients undergoing coronary artery bypass grafting.

DESIGN

Retrospective analysis of 5051 patients using univariate and logistic regression to identify risk factors associated with perioperative morbidity and mortality. Prospective application of models to a subsequent 2-year validation cohort (n = 4069).

SETTING

Cleveland Clinic Foundation.

PATIENTS

All adult patients undergoing coronary artery bypass graft surgery between July 1, 1986, and June 30, 1988 (reference group), and July 1, 1988, and June 30, 1990 (validation group).

MAIN OUTCOME MEASURES

Mortality and morbidity (myocardial infarction and use of intra-aortic balloon pump, mechanical ventilation for 3 or more days, neurological deficit, oliguric or anuric renal failure, or serious infection).

MAIN RESULTS

Emergency procedure, preoperative serum creatinine levels of greater than 168 mumol/L, severe left ventricular dysfunction, preoperative hematocrit of 0.34, increasing age, chronic pulmonary disease, prior vascular surgery, reoperation, and mitral valve insufficiency were found to be predictive of mortality. In addition to these factors, diabetes mellitus, body weight of 65 kg or less [corrected], aortic stenosis, and cerebrovascular disease were predictive of morbidity. Logistic regression equations were developed, and a simple additive score for clinical use was designed by allocating each of these risk-factor values of 1 to 6 points. Both methods predict mortality. Increased morbidity was demonstrated with increases in score.

CONCLUSIONS

The logistic or clinical models developed are superior to the currently available methods for comparing mortality outcome and provide previously unavailable information on morbidity based on preoperative status. The clinical scoring system is useful for preoperative estimates of morbidity and mortality risks.