Angiotensin II for the Treatment of Refractory Shock: A Matched Analysis

OBJECTIVES

To determine if angiotensin II is associated with improved outcomes as measured by 30- and 90-day mortality as well as other secondary outcomes such as organ dysfunction and adverse events.

DESIGN

Retrospective, matched analysis of patients receiving angiotensin II compared with both historical and concurrent controls receiving equivalent doses of nonangiotensin II vasopressors.

SETTING

Multiple ICUs in a large, university-based hospital.

PATIENTS

Eight hundred thirteen adult patients with shock admitted to an ICU and requiring vasopressor support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Angiotensin II use had no association with the primary outcome of 30-day mortality (60% vs 56%; p = 0.292). The secondary outcome of 90-day mortality was also similar (65% vs 63%; p = 0.440) as were changes in Sequential Organ Failure Assessment scores over a 5-day monitoring period after enrollment. Angiotensin II was not associated with increased rates of kidney replacement therapy (odds ratio [OR], 1.39; 95% CI, 0.88-2.19; p = 0.158) or receipt of mechanical ventilation (OR, 1.50; 95% CI, 0.41-5.51; p = 0.539) after enrollment, and the rate of thrombotic events was similar between angiotensin II and control patients (OR, 1.02; 95% CI, 0.71-1.48; p = 0.912).

CONCLUSIONS

In patients with severe shock, angiotensin II was not associated with improved mortality or organ dysfunction and was not associated with an increased rate of adverse events.

Role of cosyntropin in the management of postpartum post-dural puncture headache: a two-center retrospective cohort study

BACKGROUND

Research suggests that postpartum post-dural puncture headache (PDPH) might be prevented or treated by administering intravenous cosyntropin.

METHODS

In this retrospective cohort study, we questioned whether prophylactic (1 mg) and therapeutic (7 µg/kg) intravenous cosyntropin following unintentional dural puncture (UDP) was effective in decreasing the incidence of PDPH and therapeutic epidural blood patch (EBP) after birth. Two tertiary-care American university hospitals collected data from November 1999 to May 2017. Two hundred and fifty-three postpartum patients who experienced an UDP were analyzed. In one institution 32 patients were exposed to and 32 patients were not given prophylactic cosyntropin; in the other institution, once PDPH developed, 36 patients were given and 153 patients were not given therapeutic cosyntropin. The primary outcome for the prophylactic cosyntropin analysis was the incidence of PDPH and for the therapeutic cosyntropin analysis in exposed vs. unexposed patients, the receipt of an EBP. The secondary outcome for the prophylactic cosyntropin groups was the receipt of an EBP.

RESULTS

In the prophylactic cosyntropin analysis no significant difference was found in the risk of PDPH between those exposed to cosyntropin (19/32, 59%) and unexposed patients (17/32, 53%; odds ratio (OR) 1.37, 95% CI 0.48 to 3.98, P = 0.56), or in the incidence of EBP between exposed (12/32, 38%) and unexposed patients (6/32, 19%; OR 2.6, 95% CI 0.83 to 8.13, P = 0.095). In the therapeutic cosyntropin analysis, in patients exposed to cosyntropin the incidence of EBP was significantly higher (20/36, 56% vs. 43/153, 28%; OR 3.20, 95% CI 1.52 to 6.74, P = 0.002).

CONCLUSIONS

Our data show no benefits from the use of cosyntropin for preventing or treating postpartum PDPH.

Differences between patients in whom physicians agree versus disagree about the preoperative diagnosis of heart failure

STUDY OBJECTIVE

To quantify preoperative heart failure (HF) diagnostic agreement and identify characteristics of patients in whom physicians agreed versus disagreed about the diagnosis.

DESIGN

Observational cohort study.

SETTING

Patients undergoing major non-cardiac surgery at an academic center between 2015 and 2019.

PATIENTS

40,659 patients undergoing major non-cardiac surgery, among which a stratified subsample of 1018 patients with and without documented HF was reviewed.

INTERVENTIONS

Via a panel of physicians frequently managing patients with HF (cardiologists, cardiac anesthesiologists, intensivists), detailed chart reviews were performed (two per patient; median review time 32 min per reviewer per patient) to render adjudicated HF diagnoses.

MEASUREMENTS

Adjudicated diagnostic agreement measures (percent agreement, Krippendorf's alpha) and univariate comparisons (standardized differences) between patients in whom physicians agreed versus disagreed about the preoperative HF diagnosis.

MAIN RESULTS

Among patients with documented HF, physicians agreed about the diagnosis in 80.0% of cases (consensus positive), disagreed in 13.8% (disagreement), and refuted the diagnosis in 6.3% (consensus negative). Conversely, among patients without documented HF, physicians agreed about the diagnosis in 88.0% (consensus negative), disagreed in 8.4% (disagreement), and refuted the diagnosis in 3.6% (consensus positive). The estimated agreement for the 40,659 cases was 91.1% (95% CI 88.3%-93.9%); Krippendorff's alpha was 0.77 (0.75-0.80). Compared to patients in whom physicians agreed about a HF diagnosis, patients in whom physicians disagreed exhibited fewer guideline-defined HF diagnostic criteria.

CONCLUSIONS

Physicians usually agree about HF diagnoses adjudicated via chart review, although disagreement is not uncommon and may be partly explained by heterogeneous clinical presentations. Our findings inform preoperative screening processes by identifying patients whose characteristics contribute to physician disagreement via chart review. Clinical Trial Number / Registry URL: Not applicable.

Patient-, Clinician-, and Institution-level Variation in Inotrope Use for Cardiac Surgery: A Multicenter Observational Analysis

BACKGROUND

Conflicting evidence exists regarding the risks and benefits of inotropic therapies during cardiac surgery, and the extent of variation in clinical practice remains understudied. Therefore, the authors sought to quantify patient-, anesthesiologist-, and hospital-related contributions to variation in inotrope use.

METHODS

In this observational study, nonemergent adult cardiac surgeries using cardiopulmonary bypass were reviewed across a multicenter cohort of academic and community hospitals from 2014 to 2019. Patients who were moribund, receiving mechanical circulatory support, or receiving preoperative or home inotropes were excluded. The primary outcome was an inotrope infusion (epinephrine, dobutamine, milrinone, dopamine) administered for greater than 60 consecutive min intraoperatively or ongoing upon transport from the operating room. Institution-, clinician-, and patient-level variance components were studied.

RESULTS

Among 51,085 cases across 611 attending anesthesiologists and 29 hospitals, 27,033 (52.9%) cases received at least one intraoperative inotrope, including 21,796 (42.7%) epinephrine, 6,360 (12.4%) milrinone, 2,000 (3.9%) dobutamine, and 602 (1.2%) dopamine (non-mutually exclusive). Variation in inotrope use was 22.6% attributable to the institution, 6.8% attributable to the primary attending anesthesiologist, and 70.6% attributable to the patient. The adjusted median odds ratio for the same patient receiving inotropes was 1.73 between 2 randomly selected clinicians and 3.55 between 2 randomly selected institutions. Factors most strongly associated with increased likelihood of inotrope use were institutional medical school affiliation (adjusted odds ratio, 6.2; 95% CI, 1.39 to 27.8), heart failure (adjusted odds ratio, 2.60; 95% CI, 2.46 to 2.76), pulmonary circulation disorder (adjusted odds ratio, 1.72; 95% CI, 1.58 to 1.87), loop diuretic home medication (adjusted odds ratio, 1.55; 95% CI, 1.42 to 1.69), Black race (adjusted odds ratio, 1.49; 95% CI, 1.32 to 1.68), and digoxin home medication (adjusted odds ratio, 1.48; 95% CI, 1.18 to 1.86).

CONCLUSIONS

Variation in inotrope use during cardiac surgery is attributable to the institution and to the clinician, in addition to the patient. Variation across institutions and clinicians suggests a need for future quantitative and qualitative research to understand variation in inotrope use affecting outcomes and develop evidence-based, patient-centered inotrope therapies.

EDITOR’S PERSPECTIVE

Preoperative clinical diagnostic accuracy of heart failure among patients undergoing major noncardiac surgery: a single-centre prospective observational analysis

Background

Reliable diagnosis of heart failure during preoperative evaluation is important for perioperative management and long-term care. We aimed to quantify preoperative heart failure diagnostic accuracy and explore characteristics of patients with heart failure misdiagnoses.

Methods

We performed an observational cohort study of adults undergoing major noncardiac surgery at an academic hospital between 2015 and 2019. A preoperative clinical diagnosis of heart failure was defined using keywords from the history and clinical examination or administrative documentation. Across stratified subsamples of cases with and without clinically diagnosed heart failure, health records were intensively reviewed by an expert panel to develop an adjudicated heart failure reference standard using diagnostic criteria congruent with consensus guidelines. We calculated agreement among experts, and analysed performance of clinically diagnosed heart failure compared with the adjudicated reference standard.

Results

Across 40 555 major noncardiac procedures, a stratified subsample of 511 patients was reviewed by the expert panel. The prevalence of heart failure was 9.1% based on clinically diagnosed compared with 13.3% (95% confidence interval [CI], 10.3-16.2%) estimated by the expert panel. Overall agreement and inter-rater reliability (kappa) among heart failure experts were 95% and 0.79, respectively. Based upon expert adjudication, heart failure was clinically diagnosed with an accuracy of 92.8% (90.6-95.1%), sensitivity 57.4% (53.1-61.7%), specificity 98.3% (97.1-99.4%), positive predictive value 83.5% (80.3-86.8%), and negative predictive value 93.8% (91.7-95.9%).

Conclusions

Limitations exist to the preoperative clinical diagnosis of heart failure, with nearly half of cases undiagnosed preoperatively. Considering the risks of undiagnosed heart failure, efforts to improve preoperative heart failure diagnoses are warranted.

Prediction of Postoperative Deterioration in Cardiac Surgery Patients Using Electronic Health Record and Physiologic Waveform Data

BACKGROUND

Postoperative hemodynamic deterioration among cardiac surgical patients can indicate or lead to adverse outcomes. Whereas prediction models for such events using electronic health records or physiologic waveform data are previously described, their combined value remains incompletely defined. The authors hypothesized that models incorporating electronic health record and processed waveform signal data (electrocardiogram lead II, pulse plethysmography, arterial catheter tracing) would yield improved performance versus either modality alone.

METHODS

Intensive care unit data were reviewed after elective adult cardiac surgical procedures at an academic center between 2013 and 2020. Model features included electronic health record features and physiologic waveforms. Tensor decomposition was used for waveform feature reduction. Machine learning-based prediction models included a 2013 to 2017 training set and a 2017 to 2020 temporal holdout test set. The primary outcome was a postoperative deterioration event, defined as a composite of low cardiac index of less than 2.0 ml min-1 m-2, mean arterial pressure of less than 55 mmHg sustained for 120 min or longer, new or escalated inotrope/vasopressor infusion, epinephrine bolus of 1 mg or more, or intensive care unit mortality. Prediction models analyzed data 8 h before events.

RESULTS

Among 1,555 cases, 185 (12%) experienced 276 deterioration events, most commonly including low cardiac index (7.0% of patients), new inotrope (1.9%), and sustained hypotension (1.4%). The best performing model on the 2013 to 2017 training set yielded a C-statistic of 0.803 (95% CI, 0.799 to 0.807), although performance was substantially lower in the 2017 to 2020 test set (0.709, 0.705 to 0.712). Test set performance of the combined model was greater than corresponding models limited to solely electronic health record features (0.641; 95% CI, 0.637 to 0.646) or waveform features (0.697; 95% CI, 0.693 to 0.701).

CONCLUSIONS

Clinical deterioration prediction models combining electronic health record data and waveform data were superior to either modality alone, and performance of combined models was primarily driven by waveform data. Decreased performance of prediction models during temporal validation may be explained by data set shift, a core challenge of healthcare prediction modeling.

EDITOR’S PERSPECTIVE

Identification of intraoperative management strategies that have a differential effect on patients with reduced left ventricular ejection fraction: a retrospective cohort study

Background

There are few data to guide the intraoperative management of patients with reduced left ventricular ejection fraction (LVEF). This study aimed to describe how patients with reduced LVEF are managed differently and to identify and treatments had a different risk profile in this population.

Methods

We performed a retrospective cohort study of adult patients who underwent general anesthesia for non-cardiac surgery. The effect of anesthesia medications and fluid balance was compared between those with and without a reduced preoperative LVEF. The primary outcome was a composite of acute kidney injury, myocardial injury, pulmonary complications, and 30-day mortality. Multivariable logistic regression was used to adjust for confounders. Treatments that affected patients with reduced LVEF differently were defined as those associated with the primary outcome that also had a significant interaction with LVEF.

Results

A total of 9420 patients were included. Patients with reduced LVEF tended to have a less positive fluid balance. Etomidate, calcium, and phenylephrine were use more frequently, while propofol and remifentanil were used less frequently. Remifentanil affected patients with reduced LVEF differently than those without (interaction term OR 2.71, 95% CI 1.30–5.68, p = 0.008). While the use of remifentanil was associated with fewer complications in patients with normal systolic function (OR 0.54, 95% CI 0.42–0.68, p < 0.001), it was associated with an increase in complications in patients with reduced LVEF (OR = 3.13, 95% CI 3.06–5.98, p = 0.026).

Conclusions

Patients with a reduced preoperative LVEF are treated differently than those with a normal LVEF when undergoing non-cardiac surgery. An association was found between the use of remifentanil and an increase in postoperative adverse events that was unique to this population. Future research is needed to determine if this relationship is secondary to the medication itself or reflects a difference in how remifentanil is used in patients with reduced LVEF.

Intraoperative risk factors of acute kidney injury after liver transplantation

Acute kidney injury (AKI) is one of the most common complications of liver transplantation (LT). We examined the impact of intraoperative management on risk for AKI following LT. In this retrospective observational study, we linked data from the electronic health record with standardized transplant outcomes. Our primary outcome was stage 2 or 3 AKI as defined by Kidney Disease Improving Global Outcomes guidelines within the first 7 days of LT. We used logistic regression models to test the hypothesis that the addition of intraoperative variables, including inotropic/vasopressor administration, transfusion requirements, and hemodynamic markers improves our ability to predict AKI following LT. We also examined the impact of postoperative AKI on mortality. Of the 598 adult primary LT recipients included in our study, 43% (n = 255) were diagnosed with AKI within the first 7 postoperative days. Several preoperative and intraoperative variables including (1) electrolyte/acid-base balance disorder (International Classification of Diseases, Ninth Revision codes 253.6 or 276.x and International Classification of Diseases, Tenth Revision codes E22.2 or E87.x, where x is any digit; adjusted odds ratio [aOR], 1.917, 95% confidence interval [CI], 1.280-2.869; p = 0.002); (2) preoperative anemia (aOR, 2.612; 95% CI, 1.405-4.854; p = 0.002); (3) low serum albumin (aOR, 0.576; 95% CI, 0.410-0.808; p = 0.001), increased potassium value during reperfusion (aOR, 1.513; 95% CI, 1.103-2.077; p = 0.01), and lactate during reperfusion (aOR, 1.081; 95% CI, 1.003-1.166; p = 0.04) were associated with posttransplant AKI. New dialysis requirement within the first 7 days postoperatively predicted the posttransplant mortality. Our study identified significant association between several potentially modifiable variables with posttransplant AKI. The addition of intraoperative data did not improve overall model discrimination.

Transfusion and its association with mortality in patients receiving veno-arterial extracorporeal membrane oxygenation

PURPOSE

Patients receiving veno-arterial Extracorporeal Membrane Oxygenation (V-A ECMO) may require transfusion due to bleeding risk and desire to optimize oxygen delivery. The purposes of this study were to determine the transfusion requirements in patients receiving V-A ECMO and to determine if transfusion was associated with hospital mortality or complications.

MATERIAL AND METHODS

Retrospective chart review of adult patients at University of Michigan between 1/1/2000-6/1/2017. Survivors and decedents were compared. Logistic regression was used to determine factors independently associated with mortality, hemorrhage, and ischemic events.

RESULTS

One hundred eighty-seven patients received V-A ECMO. Median number of red cells transfused was 9 units (interquartile range 3.5-20), platelets 4 (1-11) packs, plasma 2 (0-6) units, cryoprecipitate 0 (0,0) units. Only 69 (37%) patients survived to hospital discharge. Hemorrhage occurred in 108 (58%) patients and 27 (14%) suffered ischemic complications. Renal replacement therapy (OR 2.94, 95% confidence interval: 1.51-5.68, p < 0.001) and ECMO duration (OR 1.01, 95% confidence interval: 1.00-1.01, p = 0.005) but not transfusion, were associated with increased odds of death.

CONCLUSION

Most patients receiving V-A ECMO are transfused multiple units of blood products. Receipt of transfusion or having a bleeding or ischemic complication was not associated with increased mortality.

Risk and Safety Perceptions Contribute to Transfusion Decisions in Coronary Artery Bypass Grafting

Variability persists in intraoperative red blood cell (RBC) transfusion rates, despite evidence supporting associated adverse sequelae. We evaluated whether beliefs concerning transfusion risk and safety are independently associated with the inclination to transfuse. We surveyed intraoperative transfusion decision-makers from 33 cardiac surgery programs in Michigan. The primary outcome was a provider's reported inclination to transfuse (via a six-point Likert Scale) averaged across 10 clinical vignettes based on Class IIA or IIB blood management guideline recommendations. Survey questions assessed hematocrit threshold for transfusion ("hematocrit trigger"), demographic and practice characteristics, years and case-volume of practice, knowledge of transfusion guidelines, and provider attitude regarding perceived risk and safety of blood transfusions. Linear regression models were used to estimate the effect of these variables on transfusion inclination. Mixed effect models were used to quantify the variation attributed to provider specialties and hematocrit triggers. The mean inclination to transfuse was 3.2 (might NOT transfuse) on the survey Likert scale (SD: .86) across vignettes among 202/413 (48.9%) returned surveys. Hematocrit triggers ranged from 15% to 30% (average: 20.4%; SE: .18%). The inclination to transfuse in situations with weak-to-moderate evidence for supporting transfusion was associated with a provider's hematocrit trigger (p < .01) and specialty. Providers believing in the safety of transfusions were significantly more likely to transfuse. Provider specialty and belief in transfusion safety were significantly associated with a provider's hematocrit trigger and likelihood for transfusion. Our findings suggest that blood management interventions should target these previously unaccounted for blood transfusion determinants.

Difficulty in Advancing Flexible Epidural Catheters When Establishing Labor Analgesia: An Observational Open-Label Randomized Trial

BACKGROUND

While flexible epidural catheters reduce the risk of paresthesia and intravascular cannulation, they may be more challenging to advance beyond the tip of a Tuohy needle. This may increase placement time, number of attempts, and possibly complications when establishing labor analgesia. This study investigated the ability to advance flexible epidural catheters through different epidural needles from 2 commonly used, commercially available, epidural kits.

METHODS

We hypothesized that the multiorifice wire-reinforced polyamide nylon blend epidural catheters will have a higher rate of successful first attempt insertion than the single-end hole wire-reinforced polyurethane catheters for the establishment of labor analgesia. The primary outcome was a difference in proportions of failure to advance the epidural catheter between the 2 epidural kits and was tested by a χ2 test. Two-hundred forty epidural kits were collected (n = 120/group) for 240 laboring patients requesting epidural analgesia in this open-label clinical trial from November 2018 to September 2019. Two-week time intervals were randomized for the exclusive use of 1 of the 2 kits in this study, where all patients received labor analgesia through either the flexible epidural catheter "A" or the flexible epidural catheter "B." Engineering properties of the equipment used were then determined.

RESULTS

Flexible epidural catheter "A," the single-end hole wire-reinforced polyurethane catheter, did not advance at the first attempt in 15% (n = 18 of 120) of the parturients compared to 0.8% (n = 1 of 120) of the catheter "B," the multiorifice wire-reinforced polyamide nylon blend epidural catheter (P < .0001). Twenty-five additional epidural needle manipulations were recorded in the laboring patients who received catheter "A," while 1 epidural needle manipulation was recorded in the parturients who received catheter "B" (P < .0001). Bending stiffness of the epidural catheters used from kit "B" was twice the bending stiffness of the catheters used from kit "A" (bending stiffness catheters "A" 0.64 ± 0.04 N·mm2 versus bending stiffness catheters "B" 1.28 ± 0.20 N·mm2, P = .0038), and the angle formed by the needle and the epidural catheter from kit "A" was less acute than the angle formed from kit "B" (kit "A" 14.17 ± 1.72° versus kit "B" 21.83 ± 1.33°, P = .0036), with a mean difference of 7.66° between the 2 kits' angles.

CONCLUSIONS

The incidence of an inability to advance single-end hole wire-reinforced polyurethane catheter was higher compared to the use of multiorifice wire-reinforced polyamide nylon blend epidural catheter. Variation of morphological features of epidural needles and catheters may play a critical role in determining the successful establishment of labor epidural analgesia.

Volume of packed red blood cells and fresh frozen plasma is associated with intraoperative hypocalcaemia during large volume intraoperative transfusion

BACKGROUND

Severe hypocalcaemia is associated with increased transfusion in the trauma population. Furthermore, trauma patients developing severe hypocalcaemia have higher mortality and coagulopathy. Electrolyte abnormalities associated with massive transfusion have been less studied in the surgical population. Here, we tested the primary hypothesis that volume of packed red blood cells and fresh frozen plasma transfused intraoperatively is associated with lower nadir ionised calcium in the surgical population receiving massive resuscitation.

METHODS

We performed a retrospective observational study at an academic quaternary care centre to characterise hypocalcaemia following large volume (4 or more units packed red blood cells) intraoperative transfusion. We used multivariable linear regression to assess if volume of transfusion with packed red blood cells and fresh frozen plasma were independently associated with a lower ionised calcium. We then used multivariable logistic regressions to assess the association between ionised calcium and transfusion with: (i) mortality, (ii) acute kidney injury, and (iii) postoperative coagulopathy.

RESULTS

Hypocalcaemia following large volume resuscitation in the operating room is a very frequent occurrence (70% of cases). After controlling for demographic variables and intraoperative variables, the volume transfused intraoperative was independently associated with hypocalcaemia on multivariable linear regression. Hypocalcaemia, intraoperative transfusion of packed red blood cells, and intraoperative transfusion of fresh frozen plasma were not shown to be associated with clinical outcomes.

CONCLUSIONS

Hypocalcaemia was associated with increased transfusion volume in this single-centre study. Unlike the trauma population, hypocalcaemia was not associated with increased mortality during surgical care. Our findings suggest that despite improved practice patterns of calcium supplementation, intraoperative hypocalcaemia occurs with relatively high frequency following large volume intraoperative transfusion.

Reduced Echocardiographic Inotropy Index after Cardiopulmonary Bypass Is Associated With Complications After Cardiac Surgery: An Institutional Outcomes Study

OBJECTIVE

Despite advances in echocardiography and hemodynamic monitoring, limited progress has been made to effectively quantify left ventricular function during cardiac surgery. Traditional measures, including left ventricular ejection fraction (LVEF) and cardiac index, remain dependent on loading conditions; more complex measures remain impractical in a dynamic surgical setting. However, the Smith-Madigan Inotropy Index (SMII) and potential-to-kinetic energy ratio (PKR) offer promise as measures calculable during cardiac surgery and potentially predictive of outcomes. Using echocardiographic and hemodynamic monitoring data, the authors aimed to calculate SMII and PKR values after cardiopulmonary bypass and understand associations with postoperative outcomes, adjusting for previously identified risk factors.

DESIGN

Observational cohort study.

SETTING

Tertiary care academic hospital.

PATIENTS

The study comprised 189 elective adult cardiac surgical procedures from 2015-2016.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was postoperative mortality or organ system complication (stroke, prolonged ventilation, reintubation, cardiac arrest, acute kidney injury, new-onset atrial fibrillation). After adjustment, SMII <0.83 W/m² independently predicted the primary outcome (adjusted odds ratio 2.19, 95% confidence interval 1.08-4.42); whereas PKR, LVEF, and cardiac index demonstrated no associations. When SMII and PKR were incorporated into a EuroSCORE II risk model, predictive performance improved (net reclassification index improvement 0.457; p = 0.001); whereas a model incorporating LVEF and cardiac index demonstrated no improvement (0.130; p = 0.318).

CONCLUSION

The present study demonstrated that SMII, but not PKR, as a measure of cardiac function was associated with major complications. The study's data may guide investigations of more suitable perioperative goal-directed therapies to reduce complications after cardiac surgery.

Association of Both High and Low Left Ventricular Ejection Fraction With Increased Risk After Coronary Artery Bypass Grafting

BACKGROUND

While reduced left ventricular ejection fraction (LVEF) is a known risk factor for complications after coronary artery bypass grafting (CABG), the relevance of higher LVEF values has not been established. Currently, most risk stratification tools consider LVEF values above a certain point as normal. However, since this does not account for insufficient ventricular filling or increased adrenergic tone, higher values may have clinical significance. To improve our understanding of this situation, we investigated the relationship of preoperative LVEF values with short- and long-term outcomes after CABG using a strategy that allowed for the identification of nonlinear relationships. We hypothesised that both higher and lower values are independently associated with increased postoperative complications and death in this population.

METHODS

We performed a single-centre retrospective cohort study of patients undergoing isolated CABG surgery. All patients had a preoperative measurement of their LVEF. Surgery involving mitral valve repair was excluded in order to eliminate the impact of mitral regurgitation. The primary outcome was long-term mortality; secondary outcomes included atrial fibrillation, operative mortality, and a composite outcome including any postoperative adverse event. Fractional polynomial equations were used to model the relationship between LVEF and outcomes so we could account for nonlinear relationships if present. Adjustments for confounders were made using multivariable logistic regression and Cox models.

RESULTS

A total of 7,932 subjects were included in the study. After adjusting for patient and surgical characteristics, LVEF remained associated with the primary outcome as well as the composite outcome of any postoperative adverse event. Both these relationships were best described by a J-shaped curve given that higher LVEF values were associated with increased risk, albeit not as high has lower values. Regarding long-term mortality, individuals with a preoperative LVEF of 60% demonstrated the longest survival. A statistically significant relationship was not found between LVEF and operative mortality or atrial fibrillation after adjustment for confounders.

CONCLUSIONS

Higher preoperative LVEF values may be associated with increased risk for patients undergoing CABG surgery. Future studies are needed to better characterise this phenotype.

Use of the Change in Weaning Parameters as a Predictor of Successful Re-Extubation

OBJECTIVE

Weaning parameters are well studied in patients undergoing first time extubation. Fewer data exists to guide re-extubation of patients who failed their first extubation attempt. It is reasonable to postulate that improved weaning parameters between the first and second extubation attempt would lead to improved rates of re-extubation success. To investigate, we studied a cohort of patients who failed their first extubation attempt and underwent a second attempt at extubation. We hypothesized that improvement in weaning parameters between the first and the second extubation attempt is associated with successful reextubation.

INTERVENTIONS

Rapid shallow breathing index (RSBI), maximum inspiratory pressure (MIP), vital capacity (VC), and the blood partial pressure of CO2 (PaCO2) were measured and recorded in the medical record prior to extubation along with demographic information. We examined the relationship between the change in extubation and re-extubation weaning parameters and re-extubation success.

MEASUREMENTS AND MAIN RESULTS

A total of 1283 adult patients were included. All weaning parameters obtained prior to re-extubation differed between those who were successful and those who required a second reintubation. Those with reextubation success had slightly lower PaCO2 values (39.5 ± 7.4 mmHg vs. 41.6 ± 9.1 mmHg, p = 0.0045) and about 13% higher vital capacity volumes (1021 ± 410 mL vs. 907 ± 396 mL, p = 0.0093). Lower values for RSBI (53 ± 32 breaths/min/L vs. 69 ± 42 breaths/min/L, p < 0.001) and MIP (-41 ± 12 cmH2O vs. -38 ± 13 cm H2O), p = 0.0225) were seen in those with re-extubation success. Multivariable logistical regression demonstrates lack of independent associated between the change in parameters between the 2 attempts and re-extubation success.

CONCLUSIONS

The relationship between the changes in extubation parameters through successive attempts is driven primarily by the value obtained immediately prior to re-extubation. These findings do not support waiting for an improvement in extubation parameters to extubate patients who failed a first attempt at extubation if extubation parameters are compatible with success.

The Attributable Mortality of Postoperative Bleeding Exceeds the Attributable Mortality of Postoperative Venous Thromboembolism

BACKGROUND

Bleeding and venous thromboembolic disease are considered important sources of postoperative morbidity and mortality. Clinically, treatment of these 2 disorders is often competing. We sought to better understand the relative contributions of bleeding and venous thromboembolic disease to postoperative attributable mortality in a national cohort.

METHODS

A retrospective analysis of the 2006-2017 American College of Surgeons' National Surgical Quality Improvement Program (ACS-NSQIP) database was performed to assess the adjusted odds ratio and attributable mortality for postoperative bleeding and venous thromboembolism, adjusted by year.

RESULTS

After adjustment for confounding variables, bleeding exhibited a high postoperative attributable mortality in every year studied. Venous thromboembolism appeared to contribute minimal attributable mortality.

CONCLUSIONS

Bleeding complications are a consistent source of attributable mortality in surgical patients, while the contribution of venous thromboembolic disease appears to be minimal in this analysis. Further studies are warranted to better understand the etiology of this disparity.

Early Detection of Heart Failure With Reduced Ejection Fraction Using Perioperative Data Among Noncardiac Surgical Patients: A Machine-Learning Approach

BACKGROUND

Heart failure with reduced ejection fraction (HFrEF) is a condition imposing significant health care burden. Given its syndromic nature and often insidious onset, the diagnosis may not be made until clinical manifestations prompt further evaluation. Detecting HFrEF in precursor stages could allow for early initiation of treatments to modify disease progression. Granular data collected during the perioperative period may represent an underutilized method for improving the diagnosis of HFrEF. We hypothesized that patients ultimately diagnosed with HFrEF following surgery can be identified via machine-learning approaches using pre- and intraoperative data.

METHODS

Perioperative data were reviewed from adult patients undergoing general anesthesia for major surgical procedures at an academic quaternary care center between 2010 and 2016. Patients with known HFrEF, heart failure with preserved ejection fraction, preoperative critical illness, or undergoing cardiac, cardiology, or electrophysiologic procedures were excluded. Patients were classified as healthy controls or undiagnosed HFrEF. Undiagnosed HFrEF was defined as lacking a HFrEF diagnosis preoperatively but establishing a diagnosis within 730 days postoperatively. Undiagnosed HFrEF patients were adjudicated by expert clinician review, excluding cases for which HFrEF was secondary to a perioperative triggering event, or any event not associated with HFrEF natural disease progression. Machine-learning models, including L1 regularized logistic regression, random forest, and extreme gradient boosting were developed to detect undiagnosed HFrEF, using perioperative data including 628 preoperative and 1195 intraoperative features. Training/validation and test datasets were used with parameter tuning. Test set model performance was evaluated using area under the receiver operating characteristic curve (AUROC), positive predictive value, and other standard metrics.

RESULTS

Among 67,697 cases analyzed, 279 (0.41%) patients had undiagnosed HFrEF. The AUROC for the logistic regression model was 0.869 (95% confidence interval, 0.829-0.911), 0.872 (0.836-0.909) for the random forest model, and 0.873 (0.833-0.913) for the extreme gradient boosting model. The corresponding positive predictive values were 1.69% (1.06%-2.32%), 1.42% (0.85%-1.98%), and 1.78% (1.15%-2.40%), respectively.

CONCLUSIONS

Machine-learning models leveraging perioperative data can detect undiagnosed HFrEF with good performance. However, the low prevalence of the disease results in a low positive predictive value, and for clinically meaningful sensitivity thresholds to be actionable, confirmatory testing with high specificity (eg, echocardiography or cardiac biomarkers) would be required following model detection. Future studies are necessary to externally validate algorithm performance at additional centers and explore the feasibility of embedding algorithms into the perioperative electronic health record for clinician use in real time.

Association of Intraoperative Ventilator Management With Postoperative Oxygenation, Pulmonary Complications, and Mortality

BACKGROUND

"Lung-protective ventilation" describes a ventilation strategy involving low tidal volumes (VTs) and/or low driving pressure/plateau pressure and has been associated with improved outcomes after mechanical ventilation. We evaluated the association between intraoperative ventilation parameters (including positive end-expiratory pressure [PEEP], driving pressure, and VT) and 3 postoperative outcomes: (1) PaO2/fractional inspired oxygen tension (FIO2), (2) postoperative pulmonary complications, and (3) 30-day mortality.

METHODS

We retrospectively analyzed adult patients who underwent major noncardiac surgery and remained intubated postoperatively from 2006 to 2015 at a single US center. Using multivariable regressions, we studied associations between intraoperative ventilator settings and lowest postoperative PaO2/FIO2 while intubated, pulmonary complications identified from discharge diagnoses, and in-hospital 30-day mortality.

RESULTS

Among a cohort of 2096 cases, the median PEEP was 5 cm H2O (interquartile range = 4-6), median delivered VT was 520 mL (interquartile range = 460-580), and median driving pressure was 15 cm H2O (13-19). After multivariable adjustment, intraoperative median PEEP (linear regression estimate [B] = -6.04; 95% CI, -8.22 to -3.87; P < .001), median FIO2 (B = -0.30; 95% CI, -0.50 to -0.10; P = .003), and hours with driving pressure >16 cm H2O (B = -5.40; 95% CI, -7.2 to -4.2; P < .001) were associated with decreased postoperative PaO2/FIO2. Higher postoperative PaO2/FIO2 ratios were associated with a decreased risk of pulmonary complications (adjusted odds ratio for each 100 mm Hg = 0.495; 95% CI, 0.331-0.740; P = .001, model C-statistic of 0.852) and mortality (adjusted odds ratio = 0.495; 95% CI, 0.366-0.606; P < .001, model C-statistic of 0.820). Intraoperative time with VT >500 mL was also associated with an increased likelihood of developing a postoperative pulmonary complication (adjusted odds ratio = 1.06/hour; 95% CI, 1.00-1.20; P = .042).

CONCLUSIONS

In patients requiring postoperative intubation after noncardiac surgery, increased median FIO2, increased median PEEP, and increased time duration with elevated driving pressure predict lower postoperative PaO2/FIO2. Intraoperative duration of VT >500 mL was independently associated with increased postoperative pulmonary complications. Lower postoperative PaO2/FIO2 ratios were independently associated with pulmonary complications and mortality. Our findings suggest that postoperative PaO2/FIO2 may be a potential target for future prospective trials investigating the impact of specific ventilation strategies for reducing ventilator-induced pulmonary injury.

Impact of the pre-illness lipid profile on sepsis mortality

PURPOSE

To determine if baseline lipid levels contribute to the relationship between lipid levels during sepsis and outcomes.

MATERIALS AND METHODS

We conducted a retrospective cohort study at a tertiary-care academic medical center. Multivariable logistic regression models were used to adjust for confounders. Both Systemic Inflammatory Response Syndrome (SIRS) and Sequential Organ Failure Assessment (SOFA) score-based definitions of sepsis were analyzed.

MEASUREMENTS AND MAIN RESULTS

After adjusting for patient characteristics and severity of illness, baseline values for both low density lipoprotein (LDL) cholesterol and triglycerides were associated with mortality (LDL cholesterol odds ratio [OR] 0.44, 95% confidence interval [CI] 0.23-0.84, p = .013; triglyceride OR 0.54, 95% CI 0.37-0.78, p = .001) using a SIRS based definition of sepsis. An interaction existed between these two variables, which resulted in increased mortality with higher baseline low density lipoprotein (LDL) cholesterol values for individuals with triglycerides below 208 mg/dL and the opposite direction of association above this level (interaction OR 1.48, 95% CI 1.02-2.16, p = .039). When using a SOFA score-based definition, only triglycerides remained associated with the mortality (OR 0.55, 95% CI 0.35-0.86, p = .008).

CONCLUSIONS

Baseline lipid values, particularly triglyceride concentrations, are associated with hospital mortality in septic patients.

The effect of completeness of revascularization during CABG with single versus multiple arterial grafts

INTRODUCTION

Incomplete coronary revascularization is associated with suboptimal outcomes. We investigated the long-term effects of Incomplete, Complete, and Supra-complete revascularization and whether these effects differed in the setting of single-arterial and multi-arterial coronary artery bypass graft (CABG).

METHODS

We analyzed 15-year mortality in 7157 CABG patients (64.1 ± 10.5 years; 30% women). All patients received a left internal thoracic artery to left anterior descending coronary artery graft with additional venous grafts only (single-arterial) or with at least one additional arterial graft (multi-arterial) and were grouped based on a completeness of revascularization index (CRI = number of grafts minus the number of diseased principal coronary arteries): Incomplete (CRI ≤ -1 [N = 320;4.5%]); Complete (CRI = 0 [N = 2882;40.3%]; reference group); and two Supra-complete categories (CRI = +1[N = 3050; 42.6%]; CRI ≥ + 2 [N = 905; 12.6%]). Risk-adjusted mortality hazard ratios (AHR) were calculated using comprehensive propensity score adjustment by Cox regression.

RESULTS

Incomplete revascularization was rare (4.5%) but associated with increased mortality in all patients (AHR [95% confidence interval] = 1.53 [1.29-1.80]), those undergoing single-arterial CABG (AHR = 1.27 [1.04-1.54]) and multi-arterial CABG (AHR = 2.18 [1.60-2.99]), as well as in patients with 3-Vessel (AHR = 1.37 [1.16-1.62]) and, to a lesser degree, with 2-Vessel (AHR = 1.67 [0.53-5.23]) coronary disease. Supra-complete revascularization was generally associated with incrementally decreased mortality in all patients (AHR [CRI = +1] = 0.94 [0.87-1.03]); AHR [CRI ≥ +2] = 0.74 [0.64-0.85]), and was driven by a significantly decreased mortality risk in single-arterial CABG (AHR [CRI = +1] = 0.90 [0.81-0.99]; AHR [CRI ≥ +2] = 0.64 [0.53-0.78]); and 3-Vessel disease patients (AHR [CRI = +1] = 0.94 [0.86-1.04]; and AHR [CRI ≥ +2] = 0.75 [0.63-0.88]) with no impact in multi-arterial CABG (AHR [CRI = +1] = 1.07 [0.91-1.26]; AHR [CRI ≥ +2] = 0.93 [0.73-1.17]).

CONCLUSIONS

Incomplete revascularization is associated with decreased late survival, irrespective of grafting strategy. Alternatively, supra-complete revascularization is associated with improved survival in patients with 3-Vessel CAD, and in single-arterial but not multi-arterial CABG.

Associations of the plasma lipidome with mortality in the acute respiratory distress syndrome: a longitudinal cohort study

Background

It is unknown if the plasma lipidome is a useful tool for improving our understanding of the acute respiratory distress syndrome (ARDS). Therefore, we measured the plasma lipidome of individuals with ARDS at two time-points to determine if changes in the plasma lipidome distinguished survivors from non-survivors. We hypothesized that both the absolute concentration and change in concentration over time of plasma lipids are associated with 28-day mortality in this population.

Methods

Samples for this longitudinal observational cohort study were collected at multiple tertiary-care academic medical centers as part of a previous multicenter clinical trial. A mass spectrometry shot-gun lipidomic assay was used to quantify the lipidome in plasma samples from 30 individuals. Samples from two different days were analyzed for each subject. After removing lipids with a coefficient of variation > 30%, differences between cohorts were identified using repeated measures analysis of variance. The false discovery rate was used to adjust for multiple comparisons. Relationships between significant compounds were explored using hierarchical clustering of the Pearson correlation coefficients and the magnitude of these relationships was described using receiver operating characteristic curves.

Results

The mass spectrometry assay reliably measured 359 lipids. After adjusting for multiple comparisons, 90 compounds differed between survivors and non-survivors. Survivors had higher levels for each of these lipids except for five membrane lipids. Glycerolipids, particularly those containing polyunsaturated fatty acid side-chains, represented many of the lipids with higher concentrations in survivors. The change in lipid concentration over time did not differ between survivors and non-survivors.

Conclusions

The concentration of multiple plasma lipids is associated with mortality in this group of critically ill patients with ARDS. Absolute lipid levels provided more information than the change in concentration over time. These findings support future research aimed at integrating lipidomics into critical care medicine.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0758-3) contains supplementary material, which is available to authorized users.

Genetic variants and acute kidney injury: A review of the literature

PURPOSE

Limited data exists on potential genetic contributors to acute kidney injury. This review examines current knowledge of AKI genomics.

MATERIALS AND METHODS

32 studies were selected from PubMed and GWAS Catalog queries for original data studies of human AKI genetics. Hand search of references identified 3 additional manuscripts.

RESULTS

33 of 35 studies were hypothesis-driven investigations of candidate polymorphisms that either did not consistently replicate statistically significant findings, or obtained significant results only in few small-scale studies. Vote-counting meta-analysis of 9 variants examined in >1 candidate gene study showed ≥50% non-significant studies, with larger studies generally finding non-significant results. The remaining 2 studies were large-scale unbiased investigations: One examining 2,100 genes linked with cardiovascular, metabolic, and inflammatory syndromes identified BCL2, SERPINA4, and SIK3 variants, while a genome-wide association study (GWAS) identified variants in BBS9 and the GRM7|LMCD1-AS1 intergenic region. All studies had relatively small sample sizes (<2300 subjects). Study heterogeneity precluded candidate gene and GWA meta-analysis.

CONCLUSIONS

Most studies of AKI genetics involve hypothesis-driven (rather than hypothesis-generating) candidate gene investigations that have failed to identify contributory variants consistently. A limited number of unbiased, larger-scale studies have been carried out, but there remains a pressing need for additional GWA studies.

Worldwide Trends in Multi-arterial Coronary Artery Bypass Grafting Surgery 2004-2014: A Tale of 2 Continents

Recent evidence shows that multi-arterial coronary artery bypass grafting (MABG) based on bilateral internal thoracic (BITA) or left internal thoracic (LITA) and radial artery (RA) improves long-term outcomes compared with single arterial coronary artery bypass grafting (SABG) (LITA + saphenous vein graft). How this evidence affected the worldwide use of MABG, if at all, is not well defined. Accordingly, we report 10-year temporal trends of MABG utilization from 2 continents. A study population of 1,683,434 non-emergent, primary, isolated LITA-based coronary artery bypass grafting (CABG) (≥2 grafts) patients was derived from the Society of Thoracic Surgeons (STS) (1,307,528 (79.5%) of 1,644,388 isolated CABG; total 1179 centers) and the Australia New Zealand Cardiothoracic (ANZ) Databases (34,213 (87%) of 39,046 isolated CABG; 24 centers) between 2004 and 2014. Patients were excluded based on the following: (1) no LITA, (2) if arterial grafts were other than RA or ITA, or (3) if grafting data were missing. The 3 MABG groups were LITA + RA, BITA, and BITA + RA, each with or without supplemental vein grafts. Grafting trends and their associated patient demographics were analyzed. SABG (89.3% STS, 51.4% ANZ) was the most common grafting strategy. MABG was most frequently accomplished by LITA + RA: (STS: 6.1%; ANZ: 42.6%), followed by BITA: (STS: 4.1%; ANZ: 4.3%), while ≥3 (BITA + RA) was rare in the STS (0.5%), but more common in ANZ (5.9%). In the STS, between 2004 and 2014, SABG rates systematically increased from 85.2% to 91.7%, BITA grafting was essentially unchanged from 3.6% to 4.3%, while RA use decreased systematically from 10.5% to 3.7%. In the ANZ, SABG rates increased from 17.3% to 51.4%, BITA grafting decreased from 6.3% to 3.6%, while RA grafting decreased from 65.8% to 39.0%. Compared with SABG patients, BITA patients were younger (STS: median age 59 vs 66, P < 0.001; ANZ: mean age 62 vs 68, P < 0.001), predominately male (STS: 84% vs 73%, P < 0.001; ANZ: 86% vs 79%, P < 0.001), less obese (body mass index >30 kg/m²) in STS (37% vs 42%, P < 0.001), more obese in ANZ (33% vs 32%, P = 0.001), and less diabetic (STS: 26% vs 43%, P < 0.001; ANZ: 25% vs 37%, P < 0.001), whereas RA patients were intermediate in age (STS: 61; ANZ: 65), in male sex (STS: 82%; ANZ: 81%), in the prevalence of diabetes (STS: 40%; ANZ: 34%), and were most obese (STS: 47%; ANZ: 34%). A decade-long analysis of STS data reveals a counterintuitive decline in the use (driven by decreasing RA use) of MABG: a potentially superior grafting strategy compared with SABG. In contra distinction, the smaller but growing ANZ data document a distinctly different CABG practice pattern, with a higher MABG utilization rate, but a similarly declining RA use. The reasons for these practice patterns and declining MABG are likely diverse and require further assessment.

Abstract 144: Perceived Risks and Safety of Transfusions Influence a Provider’s Inclination to Transfuse

Background: Small transfusions (1-2 units) of red blood cells (RBCs) have been associated with significantly increased odds of morbidity and mortality in the setting of cardiac surgery. Despite the development of blood management guidelines, provider-level variability persists in RBC transfusion practice. We hypothesize that a provider’s beliefs concerning the risk and safety of transfusions may influence his/her threshold for transfusing a patient.

Study Design and Methods: We surveyed operating room transfusion decision-makers (anesthesiologists, perfusionists, surgeons) across all 33 non-federal cardiac surgery programs in the state of Michigan. Survey questions assessed a respondent’s hematocrit threshold (“trigger”), as well as belief concerning the perceived risk and safety of transfusions (on a 5-point Likert Scale). Linear regression models were used to estimate the independent effect of a provider’s beliefs on the inclination to transfuse.

Results: One hundred and eighty-six of 413 submitted surveys were returned (45% response rate). Differences existed across providers in their belief concerning: (1) the risk of anemia ( p < 0.01, table 1), and (2) transfusion safety ( p = 0.02, table 1). Higher transfusion triggers were associated with a respondent’s: (1) concern for the risk of anemia (difference: 0.61, p < 0.01), and (2) belief in the safety of transfusions (difference: 0.41, p = 0.04). Perceived risks of complications (e.g., transfusion reactions, acute kidney injury) associated with transfusions differed across provider types (all p < 0.01).

Conclusion: A provider’s belief in the safety of transfusions and concern for the risk of anemia was significantly associated with a greater likelihood of blood utilization. Our findings suggest that future blood management interventions should address a provider’s beliefs concerning blood transfusions.

Abstract 035: A Clinician’s Transfusion Trigger Predicts Variation in Red Blood Cell Transfusions During Cardiac Surgery

Introduction: Variation in red blood cell (RBC) transfusions persists across providers, and is thought, in part, to be attributed to a lack of consensus regarding thresholds to support transfusion decision-making. We developed standardized clinical vignettes to assess differences in inclinations to transfuse RBCs among surgeons, anesthesiologists and perfusionists in the setting of coronary artery bypass grafting (CABG) surgery.

Methods: We surveyed operating room transfusion decision-makers across all 33 non-federal cardiac surgery programs in the state of Michigan. Respondents were asked for their transfusion threshold (hematocrit “trigger”). Ten clinical vignettes were developed to elicit a provider’s inclination to transfuse (on a 6-point Likert Scale) in situations having moderate (Class IIa) or weak (Class IIb) evidence to support a transfusion. Hierarchical generalized linear models were used to estimate the effect of provider type and hematocrit trigger on the inclination to transfuse across clinical vignettes.

Results: There was a 45% (186 of 413) response rate. Of the respondents, 75.3% (140 of 186) reported having a hematocrit trigger, with a mean of 20.4 (SD 2.2). For every 1-unit increase in a hematocrit trigger, the inclination to transfuse increased by 0.19 points on the Likert scale (p<0.001). Inclination to transfuse differed by provider type: anesthesiologists vs. perfusionists (difference: 0.71, p<0.001); surgeons vs. perfusionists (difference: -0.11, p=0.51). After accounting for a provider’s transfusion trigger, the magnitude and significance of the effect diminished for anesthesiologists (difference: 0.30, p=0.06), while strengthening for surgeons (difference: -0.29, p=0.05) ( Figure ). Twenty-seven percent of the variation in a provider’s inclination to transfuse was accounted for by the transfusion trigger, while 15% of the variation was explained by the provider type.

Conclusion: In our statewide survey of intra-operative transfusion decision-makers, a provider’s hematocrit trigger was the strongest predictor of variation in blood transfusions. Reducing variation in provider hematocrit triggers may serve as an effective

blood management target, especially in clinical situations less well supported by evidence.

Intraoperative medications associated with hemodynamically significant anaphylaxis

STUDY OBJECTIVE

To facilitate the identification of drugs and patient factors associated with hemodynamically significant anaphylaxis.

DESIGN

Using an existing database containing complete perioperative records, instances of hemodynamically significant anaphylaxis were identified using a physiologic and treatment-based screening algorithm. All cases were manually reviewed by 2 clinicians, with a third adjudicating disagreements, and confirmed cases were matched 3:1 with control cases. Intraoperative medications given in instances of hemodynamically significant anaphylaxis and patient risk factors were compared with control cases.

SETTING

University of Michigan Hospital, a large, tertiary care hospital.

PATIENTS

All adult patients undergoing surgery between January 1, 2004, and January 5, 2015.

INTERVENTIONS

None.

MEASUREMENTS

Incidence of hemodynamically significant anaphylaxis during anesthesia. Patient risk factors and intraoperative medications associated with hemodynamically significant anaphylaxis.

MAIN RESULTS

Hemodynamically significant anaphylaxis occurred in 55 of 461 986 cases (1 in 8400). Hemodynamically significant anaphylaxis occurred in 52 patients, with 1 patient experiencing 3 instances and another patient 2 instances. Only 1 drug was associated with an increased risk of hemodynamically significant anaphylaxis: protamine (odds ratio, 11.78; 95% confidence interval, 1.40-99.26; P=.0233). No category of drugs was associated with increased risk. Of patient risk factors, only personal history of anaphylaxis was associated with an increased risk (odds ratio, 77.1; 95% confidence interval, 10.46-567.69; P=<.0001). Postoperative follow-up and evaluation of patients were low at our institution. A serum tryptase level was sent in only 49% of cases, and 41% of levels were positive, an overall positive rate of 20% of cases. Following instances of hemodynamically significant anaphylaxis, only 29% of patients were seen and evaluated by an allergist at our institution.

CONCLUSIONS

Hemodynamically significant anaphylaxis is a rare complication of anesthesia, with an incidence consistent with the existing literature. Contrary to most existing literature, only protamine was associated with increased risk. A personal history of anaphylaxis appears to best predict risk of hemodynamically significant anaphylaxis.

Outcome After Tracheostomy for Respiratory Failure in the Elderly

The purpose of this study was to determine hospital and postdischarge survival and functional status at follow-up in elderly patients receiving tracheostomy for respiratory failure and to determine if these outcomes differed between the younger elderly (65-74 years) and the older elderly (= 75 years). This was a retrospective chart review with prospective administration of the SF-36 conducted in 228 patients aged 65 years or older who had undergone tracheostomy to facilitate mechanical ventilation for respiratory failure at a tertiary care, university-affiliated, urban medical center. Demographics, comorbidities, hospital survival, liberation from mechanical ventilation, long-term survival, and functional status were determined. Combined hospital and hospice mortality did not differ by age, being 34% and 26% in the 65- to 74-year and = 75-year groups, respectively ( P> .05). However, older patients (= 75 years old) were more likely to be discharged still requiring mechanical ventilation (62% vs 45%, P< .05). Only one half of hospital survivors survived for 1 additional year. Those discharged ventilator-dependent were more likely to die. Of the 20 participants in the SF-36 portion of the study, most had fair to good emotional and social functioning but were extremely limited physically.

Variability of Automated Intraoperative ST Segment Values Predicts Postoperative Troponin Elevation

BACKGROUND

Intraoperative electrocardiographic monitoring is considered a standard of care. However, there are no evidence-based algorithms for using intraoperative ST segment data to identify patients at high risk for adverse perioperative cardiac events. Therefore, we performed an exploratory study of statistical measures summarizing intraoperative ST segment values determine whether the variability of these measurements was associated with adverse postoperative events. We hypothesized that elevation, depression, and variability of ST segments captured in an anesthesia information management system are associated with postoperative serum troponin elevation.

METHODS

We conducted a single-institution, retrospective study of intraoperative automated ST segment measurements from leads I, II, and III, which were recorded in the electronic anesthesia record of adult patients undergoing noncardiac surgery. The maximum, minimum, mean, and SD of ST segment values were entered into logistic regression models to find independent associations with myocardial injury, defined as an elevated serum troponin concentration during the 7 days after surgery. Performance of these models was assessed by measuring the area under the receiver operator characteristic curve. The net reclassification improvement was calculated to quantify the amount of information that the ST segment values analysis added regarding the ability to predict postoperative troponin elevation.

RESULTS

Of 81,011 subjects, 4504 (5.6%) had postoperative myocardial injury. After adjusting for patient characteristics, the ST segment maximal depression (e.g., lead I: odds ratio [OR], 1.66; 95% confidence interval [CI], 1.26-2.19; P = 0.0004), maximal elevation (e.g., lead I: OR, 1.70; 95% CI, 1.34-2.17; P < 0.0001), and SD (e.g., lead I: OR, 0.16; 95% CI, 0.06-0.42; P = 0.0002) were found to have statistically significant associations with myocardial injury. Increased SD was associated with decreased risk when accounting for the maximal amount of ST segment depression and elevation and for patient characteristics. The ST segment summary statistics model had fair discrimination, with an area under the receiver operator characteristic curve of 0.71 (95% CI, 0.68-0.73). Addition of ST segment data produced a net reclassification improvement of 0.0345 (95% CI, 0.00016-0.0591; P = 0.0474).

CONCLUSIONS

Analysis of automated ST segment values obtained during anesthesia may be useful for improving the prediction of postoperative troponin elevation.

Effect of salt intake on beat-to-beat blood pressure nonlinear dynamics and entropy in salt-sensitive versus salt-protected rats

Blood pressure exhibits substantial short- and long-term variability (BPV). We assessed the hypothesis that the complexity of beat-to-beat BPV will be differentially altered in salt-sensitive hypertensive Dahl rats (SS) versus rats protected from salt-induced hypertension (SSBN13) maintained on high-salt versus low-salt diet. Beat-to-beat systolic and diastolic BP series from nine SS and six SSBN13 rats (http://www.physionet.org) were analyzed following 9 weeks on low salt and repeated after 2 weeks on high salt. BP complexity was quantified by detrended fluctuation analysis (DFA), short- and long-range scaling exponents (αS and αL), sample entropy (SampEn), and traditional standard deviation (SD) and coefficient of variation (CV(%)). Mean systolic and diastolic BP increased on high-salt diet (P < 0.01) particularly for SS rats. SD and CV(%) were similar across groups irrespective of diet. Salt-sensitive and -protected rats exhibited similar complexity indices on low-salt diet. On high salt, (1) SS rats showed increased scaling exponents or smoother, systolic (P = 0.007 [αL]) and diastolic (P = 0.008 [αL]) BP series; (2) salt-protected rats showed lower SampEn (less complex) systolic and diastolic BP (P = 0.046); and (3) compared to protected SSBN13 rats, SS showed higher αL for systolic (P = 0.01) and diastolic (P = 0.005) BP Hypertensive SS rats are more susceptible to high salt with a greater rise in mean BP and reduced complexity. Comparable mean pressures in sensitive and protective rats when on low-salt diet coupled with similar BPV dynamics suggest a protective role of low-salt intake in hypertensive rats. This effect likely reflects better coupling of biologic oscillators.

Multi Versus Single Arterial Coronary Bypass Graft Surgery Across the Ejection Fraction Spectrum

BACKGROUND

Left internal thoracic artery (LITA) and radial artery (RA) multi-arterial CABG (MABG) is generally associated with improved long-term survival compared with traditional LITA and saphenous vein single arterial CABG (SABG). We examined the hypothesis that this multi-arterial survival advantage persists irrespective of left ventricular ejection fraction (LVEF).

METHODS

We retrospectively analyzed the primary, non-salvage multi-graft CABG experience (n = 11,261; 64.4 ± 10.4 years, 70.4% men) from 2 institutions (1995 to 2011). Risk-adjusted 15-year survival was pairwise compared for the MABG versus SABG grafting approaches within 3 LVEF subcohorts (>0.50, n = 4,833 [44% MABG]; 0.36 to 0.50, n = 4,465 [39% MABG]; and ≤ 0.35, n = 1,963 [35% MABG]) using propensity-matched and covariate adjusted Cox regression (all patients) comparisons.

RESULTS

Propensity matching yielded 1,317 (LVEF > 0.50), 1,179 (LVEF, 0.36 to 0.50), and 470 (LVEF ≤ 0.35) well-matched grafting method pairs. Acute perioperative mortality was equivalent between MABG and SABG within each LVEF group, but increased with decreasing LVEF. MABG was uniformly associated with better 15-year survival compared with SABG for all LVEF categories. The associated matched-adjusted hazard ratios (95% confidence intervals) were consistent across EF groups at 0.79 (0.68 to 0.93), 0.80 (0.69 to 0.93), and 0.82 (0.66 to 1.0), respectively. Covariate adjusted HR in all patients concurred with matched results.

CONCLUSIONS

MABG results in significantly enhanced long-term survival compared with LITA/SVG SABG regardless of the degree of LV dysfunction. These results favor MABG as the therapy of choice in patients with LV dysfunction.

Impact of prior intracoronary stenting on late outcomes of coronary artery bypass surgery in diabetics with triple-vessel disease

OBJECTIVE

Recent studies have indicated that coronary artery bypass grafting (CABG) outcomes in patients with prior stents are suboptimal. We aimed to study the impact of prior percutaneous coronary intervention (PCI) with stenting (PCI-S) on late CABG mortality in diabetic patients with triple-vessel disease.

METHODS

We reviewed the primary nonemergency CABG experience from a single U.S. institution (n = 7005; 1996-2007, Toledo, Ohio). Diabetics with triple-vessel disease (n = 1583) were identified and divided into 2 groups: (1) prior PCI-S (n = 202); and (2) no prior PCI (No-PCI [n = 1381]). Hierarchic Cox proportional hazards models were used to assess the effect of prior PCI-S on 5-year mortality after CABG. A propensity score for PCI-S and No-PCI patients was derived using a nonparsimonious logistic regression and used to generate a 1:1 (PCI-S to No-PCI) matched cohort.

RESULTS

In model 1, after adjusting for preoperative clinical characteristics, medications, off-pump surgery, and isolated CABG surgery status, prior PCI-S was associated with a 39% increased risk of mortality (hazard ratio [HR] = 1.39, with 95% confidence interval [CI; 1.02, 1.90]; P = .04). Further adjustment for date of surgery (model 2) (HR = 1.39, with 95% CI [1.02, 1.91]; P = .04) or operative parameters (model 3) (HR = 1.38, with 95% CI [1.01, 1.88]; P = .046) did not alter the association. The 1:1 matched-cohort analysis confirmed the increased risk associated with PCI-S (HR = 1.61, with 95% CI [1.03, 2.51]; P = .037).

CONCLUSIONS

Patients who have both diabetes and triple-vessel disease, and have undergone prior PCI-S, have poorer long-term outcomes after CABG compared with those who have had no prior PCI-S.

Association of sleep and fatigue with decision regret among critical care nurses

BACKGROUND

The effects of inadequate sleep on clinical decisions may be important for patients in critical care units, who are often more vulnerable than patients in other units. Fatigued nurses are more likely than well-rested nurses to make faulty decisions that lead to decision regret, a negative cognitive emotion that occurs when the actual outcome differs from the desired or expected outcome.

OBJECTIVES

To examine the association between selected sleep variables, impairment due to fatigue, and clinical-decision self-efficacy and regret among critical care nurses. Decision regret was the primary outcome variable. Methods A nonexperimental, descriptive design and extant measures were used to obtain data from a random sample of full-time nurses. Binary logistic regression models were used to examine the association between sleep variables, fatigue, and clinical-decision self-efficacy and regret. The discrimination of the models was compared with the C statistic, the area under the receiver operating characteristic curve.

RESULTS

A total of 605 nurses returned the questionnaires (17% response rate). Among these, decision regret was reported by 157 of 546 (29%). Nurses with decision regret reported more fatigue, more daytime sleepiness, less intershift recovery, and worse sleep quality than did nurses without decision regret. Being male, working a 12-hour shift, and clinical-decision satisfaction were significantly associated with decision regret (C statistic, 0.719; SE, 0.024).

CONCLUSION

Nurses who experience impairments due to fatigue, loss of sleep, and inability to recover between shifts are more likely than unimpaired nurses to report decision regret.

The association of elevated creatine kinase-myocardial band on mortality after coronary artery bypass grafting surgery is time and magnitude limited

OBJECTIVE

The joint European Society of Cardiology and American College of Cardiology consensus statement on myocardial necrosis after revascularization stated that any amount of myocardial necrosis as detected by cardiac enzymes should be labeled a myocardial infarct. However, it also stated that more data collection is necessary to better interpret the elevation of cardiac enzymes after coronary artery bypass grafting. We sought to determine if a single postoperative value of creatine kinase-myocardial band could be used as a risk factor to help predict mortality after coronary artery bypass surgery.

METHODS

A retrospective analysis of prospectively collected data on 1161 patients undergoing first-time, isolated coronary artery bypass surgery utilizing normothermic cardiopulmonary bypass was conducted. Creatine kinase-myocardial band was measured the morning after surgery. Binary logistic regression, Cox proportional hazard models, and overlapping quintiles were used to illuminate the association between creatine kinase-myocardial band elevation and mortality after coronary artery bypass surgery.

RESULTS

We found a threshold value of creatine kinase-myocardial band, 40 ng/mL, above which elevations were associated with increased death rates. This association held after adjustment for other factors known to contribute to postoperative mortality. However, after 1 year, there was no longer a statistically significant higher mortality associated with elevated creatinine kinase-myocardial band > 40 ng/mL.

CONCLUSION

Elevation of creatine kinase-myocardial band the morning after surgery above a threshold 40 ng/mL is associated with an increased risk of mortality.

Effect of blood transfusion on long-term survival after cardiac operation

BACKGROUND

Blood transfusions have been linked to increased morbidity and mortality. Bleeding during and after cardiac operations and the hemodilution effects of cardiopulmonary bypass commonly result in blood transfusions. Because we could not find any studies evaluating the effects of transfusion on long-term survival after cardiac operation, we sought to determine these effects.

METHODS

We studied 1,915 patients who underwent first-time isolated coronary artery bypass operations between July 6, 1994 and December 31, 1997 at our institution. Patients with transfusions were compared with those who had not been transfused. Long-term survival data were obtained from the United States Social Security Death Index. Groups were compared by Cox proportional hazard models, Kaplan-Meier survival plots, and hazard functions.

RESULTS

Six hundred forty-nine of 1,915 study patients (34%) received a transfusion during their hospitalization. Transfused patients were older, smaller, and more likely to be female, and had more comorbidity. Transfused patients also had twice the 5-year mortality (15% vs 7%) of nontransfused patients. After correction for comorbidities and other factors, transfusion was still associated with a 70% increase in mortality (risk ratio = 1.7; 95% confidence interval = 1.4 to 2.0; p = 0.001). By multivariate analysis, transfusion, peripheral vascular disease, chronic obstructive pulmonary disease, New York Heart Association functional class IV, and age were significant predictors of long-term mortality.

CONCLUSIONS

We found that blood transfusions during or after coronary artery bypass operations were associated with increased long-term mortality.

Negative-pressure pulmonary edema with a patent airway

Negative pressure is a rarely occurring cause of pulmonary edema. It has previously been reported only in the presence of a closed glottis or obstructed airway. A 64-year-old man with 74% body surface burn without any inhalation injury experienced acute pulmonary edema on hospital day 11 associated with high-minute volume and negative inspiratory pressures at the ventilator. The edema cleared after sedation and paralysis. Workup disclosed pulmonary emboli and normal cardiac-filling pressures. A mechanical model, simulating his breathing, measured intrathoracic pressure of -37 +/- 12 mm Hg, which is sufficiently negative to cause pulmonary edema despite a patent airway. Pulmonary emboli increased his respiratory drive to amounts greater than what the ventilator could deliver, thus leading to the large negative intrathoracic pressure and pulmonary edema.