Temporary Mechanical Circulatory Support after Cardiac Surgery.

Postcardiotomy shock in the cardiac surgical patient is a highly morbid condition characterized by profound myocardial impairment and decreased systemic perfusion inadequate to meet end-organ metabolic demand. Postcardiotomy shock is associated with significant morbidity and mortality. Poor outcomes motivate the increased use of mechanical circulatory support (MCS) to restore perfusion in an effort to prevent multiorgan injury and improve patient survival. Despite growing acceptance and adoption of MCS for postcardiotomy shock, criteria for initiation, clinical management, and future areas of clinical investigation remain a topic of ongoing debate. This article seeks to (1) define critical cardiac dysfunction in the patient after cardiotomy, (2) provide an overview of commonly used MCS devices, and (3) summarize the relevant clinical experience for various MCS devices available in the literature, with additional recognition for the role of MCS as a part of a modified approach to the cardiac arrest algorithm in the cardiac surgical patient.

Characteristics and Outcomes of Prolonged Venoarterial Extracorporeal Membrane Oxygenation After Cardiac Surgery: The Post-Cardiotomy Extracorporeal Life Support (PELS-1) Cohort Study.

OBJECTIVES: Most post-cardiotomy (PC) extracorporeal membrane oxygenation (ECMO) runs last less than 7 days. Studies on the outcomes of longer runs have provided conflicting results. This study investigates patient characteristics and short- and long-term outcomes in relation to PC ECMO duration, with a focus on prolonged (> 7 d) ECMO. DESIGN: Retrospective observational cohort study. SETTING: Thirty-four centers from 16 countries between January 2000 and December 2020. PATIENTS: Adults requiring post PC ECMO between 2000 and 2020. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Characteristics, in-hospital, and post-discharge outcomes were compared among patients categorized by ECMO duration. Survivors and nonsurvivors were compared in the subgroup of patients with ECMO duration greater than 7 days. The primary outcome was in-hospital mortality. Two thousand twenty-one patients were included who required PC ECMO for 0-3 days (n = 649 [32.1%]), 4-7 days (n = 776 [38.3%]), 8-10 days (n = 263 [13.0%]), and greater than 10 days (n = 333 [16.5%]). There were no major differences in the investigated preoperative and procedural characteristics among ECMO duration groups. However, the longer ECMO duration category was associated with multiple complications including bleeding, acute kidney injury, arrhythmias, and sepsis. Hospital mortality followed a U-shape curve, with lowest mortality in patients with ECMO duration of 4-7 days (n = 394, 50.8%) and highest in patients with greater than 10 days ECMO support (n = 242, 72.7%). There was no significant difference in post-discharge survival between ECMO duration groups. In patients with ECMO duration greater than 7 days, age, comorbidities, valvular diseases, and complex procedures were associated with nonsurvival. CONCLUSIONS: Nearly 30% of PC ECMO patients were supported for greater than 7 days. In-hospital mortality increased after 7 days of support, especially in patients undergoing valvular and complex surgery, or who had complications, although the long-term post-discharge prognosis was comparable to PC ECMO patients with shorter support duration.

Features and outcomes of female and male patients requiring postcardiotomy extracorporeal life support.

OBJECTIVES: Although cardiogenic shock requiring extracorporeal life support after cardiac surgery is associated with high mortality, the impact of sex on outcomes of postcardiotomy extracorporeal life support remains unclear with conflicting results in the literature. We compare patient characteristics, in-hospital outcomes, and overall survival between females and males requiring postcardiotomy extracorporeal life support. METHODS: This retrospective, multicenter (34 centers), observational study included adults requiring postcardiotomy extracorporeal life support between 2000 and 2020. Preoperative, procedural, and extracorporeal life support characteristics, complications, and survival were compared between females and males. Association between sex and in-hospital survival was investigated through mixed Cox proportional hazard models. RESULTS: This analysis included 1823 patients (female: 40.8%; median age: 66.0 years [interquartile range, 56.2-73.0 years]). Females underwent more mitral valve surgery (females: 38.4%, males: 33.1%, P = .019) and tricuspid valve surgery (feamales: 18%, males: 12.4%, P < .001), whereas males underwent more coronary artery surgery (females: 45.9%, males: 52.4%, P = .007). Extracorporeal life support implantation was more common intraoperatively in feamales (females: 64.1%, females: 59.1%) and postoperatively in males (females: 35.9%, males: 40.9%, P = .036). Ventricular unloading (females: 25.1%, males: 36.2%, P < .001) and intra-aortic balloon pumps (females: 25.8%, males: 36.8%, P < .001) were most frequently used in males. Females had more postoperative right ventricular failure (females: 24.1%, males: 19.1%, P = .016) and limb ischemia (females: 12.3%, males: 8.8%, P = .23). In-hospital mortality was 64.9% in females and 61.9% in males (P = .199) with no differences in 5-year survival (females: 20%, 95% CI, 17-23; males: 24%, 95% CI, 21-28; P = .069). Crude hazard ratio for in-hospital mortality in females was 1.12 (95% CI, 0.99-1.27; P = .069) and did not change after adjustments. CONCLUSIONS: This study demonstrates that female and male patients requiring postcardiotomy extracorporeal life support have different preoperative and extracorporeal life support characteristics, as well as complications, without a statistical difference in in-hospital and 5-year survivals.

Impact of Extracorporeal Membrane Oxygenation Bridging Duration on Lung Transplant Outcomes.

BACKGROUND: We sought to characterize the association between venovenous extracorporeal membrane oxygenation (VV-ECMO) bridging duration and outcomes in patients listed for lung transplantation. METHODS: A retrospective observational study was conducted using the Organ Procurement and Transplantation Network (OPTN) database to identify adults (aged ≥18 years) who were listed for lung transplantation between 2016 and 2020 and were bridged with VV-ECMO. Patients were then stratified into groups, determined by risk inflection points, depending on the amount of time spent on pretransplant ECMO: group 1 (≤5 days), group 2 (6-10 days), group 3 (11-20 days), and group 4 (>20 days). Waiting list survival between groups was analyzed using Fine-Gray competing risk models. Posttransplant survival was compared using Cox regression. RESULTS: Of 566 eligible VV-ECMO bridge-to-lung-transplant patients (median age, 54 years, 49% men), 174 (31%), 124 (22%), 130 (23%), and 138 (24%) were categorized as groups 1, 2, 3, and 4, respectively. Overall, median duration of VV-ECMO was 10 days (interquartile range, 1-211 days), and 178 patients (31%) died on the waiting list. In the Fine-Gray model, compared with group 1, patients bridged with longer ECMO durations in group 2 (subdistribution hazard ratio [SHR], 2.95; 95% CI, 1.63-5.35), group 3 (SHR, 3.96; 95% CI, 2.36-6.63), and group 4 (SHR, 4.33; 95% CI, 2.59-7.22, all P < .001) were more likely to die on the waiting list. Of 388 patients receiving a transplant, pretransplant ECMO duration was not associated with 1-year survival in Cox regression. CONCLUSIONS: Prolonged duration of ECMO bridging was associated with worse waiting list mortality but did not impact survival after lung transplant. Prioritization of very early transplantation may improve waiting list outcomes in this population.

Extracorporeal Membrane Oxygenation Physiological Factors Influence Pulse Oximetry and Arterial Oxygen Saturation Discrepancies.

BACKGROUND: Cannulation strategy, vasopressors, and hemolysis are important physiological factors that influence hemodynamics in extracorporeal membrane oxygenation (ECMO). We hypothesized these factors influence the discrepancy between oxygen saturation measured by pulse oximetry (Spo2) and arterial blood gas (Sao2) in patients on ECMO. METHODS: We retrospectively analyzed adults (aged ≥18 years) on venoarterial or venovenous ECMO at a tertiary academic ECMO center. Spo2-Sao2 pairs with oxygen saturation ≥70% and measured within 10 minutes were included. Occult hypoxemia was defined as Sao2 ≤88% with a time-matched Spo2 ≥92%. Adjusted linear mixed-effects modeling was used to assess the Spo2-Sao2 discrepancy with preselected demographics and time-matched laboratory variables. Vasopressor use was quantified by vasopressor dose equivalences. RESULTS: Of 139 venoarterial-ECMO and 88 venovenous-ECMO patients, we examined 20,053 Spo2-Sao2 pairs. The Spo2-Sao2 discrepancy was greater in venovenous-ECMO (1.15%) vs venoarterial-ECMO (-0.35%, P < .001). Overall, 81 patients (35%) experienced occult hypoxemia during ECMO. Occult hypoxemia was more common in venovenous-ECMO (65%) than in venoarterial-ECMO (17%, P < .001). In linear mixed-effects modeling, Spo2 underestimated Sao2 by 9.48% in central vs peripheral venoarterial-ECMO (95% CI, -17.1% to -1.79%; P = .02). Higher vasopressor dose equivalences significantly worsened the Spo2-Sao2 discrepancy (P < .001). In linear mixed-effects modeling, Spo2 overestimated Sao2 by 25.43% in single lumen-cannulated vs double lumen-cannulated venovenous-ECMO (95% CI, 5.27%-45.6%; P = .03). Higher vasopressor dose equivalences and lactate dehydrogenase levels significantly worsened the Spo2-Sao2 discrepancy (P < .001). CONCLUSIONS: Venovenous-ECMO patients are at higher risk for occult hypoxemia compared with venoarterial-ECMO. A higher vasopressor requirement and different cannulation strategies (central venoarterial-ECMO; single-lumen venovenous-ECMO) were significant factors for clinically significant Spo2-Sao2 discrepancy in both ECMO modes.

Patient and Management Variables Associated With Survival After Postcardiotomy Extracorporeal Membrane Oxygenation in Adults: The PELS-1 Multicenter Cohort Study.

Background Extracorporeal membrane oxygenation (ECMO) has been increasingly used for postcardiotomy cardiogenic shock, but without a concomitant reduction in observed in-hospital mortality. Long-term outcomes are unknown. This study describes patients' characteristics, in-hospital outcome, and 10-year survival after postcardiotomy ECMO. Variables associated with in-hospital and postdischarge mortality are investigated and reported. Methods and Results The retrospective international multicenter observational PELS-1 (Postcardiotomy Extracorporeal Life Support) study includes data on adults requiring ECMO for postcardiotomy cardiogenic shock between 2000 and 2020 from 34 centers. Variables associated with mortality were estimated preoperatively, intraoperatively, during ECMO, and after the occurrence of any complications, and then analyzed at different time points during a patient's clinical course, through mixed Cox proportional hazards models containing fixed and random effects. Follow-up was established by institutional chart review or contacting patients. This analysis included 2058 patients (59% were men; median [interquartile range] age, 65.0 [55.0-72.0] years). In-hospital mortality was 60.5%. Independent variables associated with in-hospital mortality were age (hazard ratio [HR], 1.02 [95% CI, 1.01-1.02]) and preoperative cardiac arrest (HR, 1.41 [95% CI, 1.15-1.73]). In the subgroup of hospital survivors, the overall 1-, 2-, 5-, and 10-year survival rates were 89.5% (95% CI, 87.0%-92.0%), 85.4% (95% CI, 82.5%-88.3%), 76.4% (95% CI, 72.5%-80.5%), and 65.9% (95% CI, 60.3%-72.0%), respectively. Variables associated with postdischarge mortality included older age, atrial fibrillation, emergency surgery, type of surgery, postoperative acute kidney injury, and postoperative septic shock. Conclusions In adults, in-hospital mortality after postcardiotomy ECMO remains high; however, two-thirds of those who are discharged from hospital survive up to 10 years. Patient selection, intraoperative decisions, and ECMO management remain key variables associated with survival in this cohort. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03857217.

Hospital variability in modifiable factors driving coronary artery bypass charges.

OBJECTIVE: Coronary artery bypass grafting is associated with significant interhospital variability in charges. Drivers of hospital charge variability remain elusive. We identified modifiable factors associated with statewide interhospital variability in hospital charges for coronary artery bypass grafting. METHODS: Charge data were used as a surrogate for cost. Society of Thoracic Surgeons data from Maryland institutions and charge data from the Maryland Health Care Commission were linked to characterize interhospital charge variability for coronary artery bypass grafting. Multivariable linear regression was used to identify perioperative factors independently related to coronary artery bypass grafting charges. Of the factors independently associated with charges, we analyzed which factors varied between hospitals. RESULTS: A total of 10,337 patients underwent isolated coronary artery bypass grafting at 9 Maryland hospitals from 2012 to 2016, of whom 7532 patients were available for analyses. Mean normalized charges for isolated coronary artery bypass grafting varied significantly among hospitals, ranging from $30,000 to $57,000 (P < .001). Longer preoperative length of stay, operating room time, and major postoperative morbidity including stroke, renal failure, prolonged ventilation, reoperation, and deep sternal wound infection were associated with greater hospital charges. Incidence of major postoperative events, except stroke and deep sternal wound infection, was variable between hospitals. In a univariate linear regression model, patient risk profile only accounted for approximately 10% of statistical variance in charges. CONCLUSIONS: There is significant charge variability for coronary artery bypass grafting among hospitals within the same state. By targeting variation in preoperative length of stay, operating room time, postoperative renal failure, prolonged ventilation, and reoperation, cardiac surgery programs can realize cost savings while improving quality of care for this resource-intense patient population.

Early posthospitalization recovery after extracorporeal membrane oxygenation in survivors of COVID-19.

OBJECTIVE: We sought to determine the influence of venovenous extracorporeal membrane oxygenation (ECMO) on outcomes of mechanically ventilated patients with COVID-19 during the first 120 days after hospital discharge. METHODS: Five academic centers conducted a retrospective analysis of mechanically ventilated patients with COVID-19 admitted during March through May 2020. Survivors had access to a multidisciplinary postintensive care recovery clinic. Physical, psychological, and cognitive deficits were measured using validated instruments and compared based on ECMO status. RESULTS: Two hundred sixty two mechanically ventilated patients were compared with 46 patients cannulated for venovenous ECMO. Patients receiving ECMO were younger and traveled farther but there was no significant difference in gender, race, or body mass index. ECMO patients were mechanically ventilated for longer durations (median, 26 days [interquartile range, 19.5-41 days] vs 13 days [interquartile range, 7-20 days]) and were more likely to receive inhaled pulmonary vasodilators, neuromuscular blockade, investigational COVID-19 therapies, blood transfusions, and inotropes. Patients receiving ECMO experienced greater bleeding and clotting events (P < .01). However, survival at discharge was similar (69.6% vs 70.6%). Of the 217 survivors, 65.0% had documented follow-up within 120 days. Overall, 95.5% were residing at home, 25.7% had returned to work or usual activity, and 23.1% were still using supplemental oxygen; these rates did not differ significantly based on ECMO status. Rates of physical, psychological, and cognitive deficits were similar. CONCLUSIONS: Our data suggest that COVID-19 survivors experience significant physical, psychological, and cognitive deficits following intensive care unit admission. Despite a more complex critical illness course, longer average duration of mechanical ventilation, and longer average length of stay, patients treated with venovenous ECMO had similar survival at discharge and outcomes within 120 days of discharge.

Neuromonitoring detects brain injury in patients receiving extracorporeal membrane oxygenation support.

OBJECTIVE: There is limited evidence on standardized protocols for optimal neurological monitoring methods in patients receiving extracorporeal membrane oxygenation (ECMO). We previously introduced protocolized noninvasive multimodal neuromonitoring using serial neurological examinations, electroencephalography, transcranial Doppler ultrasound, and somatosensory evoked potentials. The purpose of this study was to examine if standardized neuromonitoring is associated with detection of acute brain injury (ABI) and improved patient outcomes. METHODS: A retrospective analysis of ECMO patients who received neurocritical care consultation was performed and outcomes were reviewed. The cohort was stratified according to those who did not receive standardized neuromonitoring (era 1: 2016-2017) and those who received standardized neuromonitoring (era 2: 2017-2020). Multivariable logistic regression was used to evaluate the association between standardized neuromonitoring and ABI. RESULTS: A total of 215 patients (mean age, 54 years; 60% male) underwent ECMO (71% venoarterial-ECMO) in our institution, 70 in era 1 and 145 in era 2. The proportion of patients diagnosed with ABI were 23% in era 1 and 33% in era 2 (P = .12). In multivariable logistic regression, standardized neuromonitoring (odds ratio, 2.24; 95% CI, 1.12-4.48; P = .02) and pre-ECMO cardiac arrest (odds ratio, 2.17; 95% CI, 1.14-4.14; P = .02) were independently associated with ABI. There was a greater proportion of patients with good neurological outcomes when discharged alive in era 2 (54% vs 30%; P = .04). CONCLUSIONS: Standardized neuromonitoring was associated with increased ABIs in ECMO patients. Although neuromonitoring does not prevent ABI from occurring, it might prevent worsening with timely interventions (eg, anticoagulation management, optimizing oxygen delivery and blood pressure), leading to improved neurological outcomes at discharge.

Causal determinants of postoperative length of stay in cardiac surgery using causal graphical learning.

OBJECTIVE: We aimed to learn the causal determinants of postoperative length of stay in cardiac surgery patients undergoing isolated coronary artery bypass grafting or aortic valve replacement surgery. METHODS: For patients undergoing isolated coronary artery bypass grafting or isolated aortic valve replacement surgeries between 2011 and 2016, we used causal graphical modeling on electronic health record data. The Fast Causal Inference (FCI) algorithm from the Tetrad software was used on data to estimate a Partial Ancestral Graph (PAG) depicting direct and indirect causes of postoperative length of stay, given background clinical knowledge. Then, we used the latent variable intervention-calculus when the directed acyclic graph is absent (LV-IDA) algorithm to estimate strengths of causal effects of interest. Finally, we ran a linear regression for postoperative length of stay to contrast statistical associations with what was learned by our causal analysis. RESULTS: In our cohort of 2610 patients, the mean postoperative length of stay was 219 hours compared with the Society of Thoracic Surgeons 2016 national mean postoperative length of stay of approximately 168 hours. Most variables that clinicians believe to be predictors of postoperative length of stay were found to be causes, but some were direct (eg, age, diabetes, hematocrit, total operating time, and postoperative complications), and others were indirect (including gender, race, and operating surgeon). The strongest average causal effects on postoperative length of stay were exhibited by preoperative dialysis (209 hours); neuro-, pulmonary-, and infection-related postoperative complications (315 hours, 89 hours, and 131 hours, respectively); reintubation (61 hours); extubation in operating room (-47 hours); and total operating room duration (48 hours). Linear regression coefficients diverged from causal effects in magnitude (eg, dialysis) and direction (eg, crossclamp time). CONCLUSIONS: By using retrospective electronic health record data and background clinical knowledge, causal graphical modeling retrieved direct and indirect causes of postoperative length of stay and their relative strengths. These insights will be useful in designing clinical protocols and targeting improvements in patient management.

Interhospital variability in failure to rescue rates following aortic valve surgery.

Objective: This study evaluated interhospital variability and determinants of failure-to-rescue for patients undergoing surgical aortic valve replacement. Methods: An observational study was conducted among 28,842 patients undergoing aortic valve replacement with or without coronary artery bypass grafting between July 2011 and June 2017 across 90 hospitals participating in the Society of Thoracic Surgeons Adult Cardiac Surgery Database. Postoperative complications were defined as major (stroke, renal failure, reoperation, prolonged ventilation, sternal infection) and overall (major plus 14 other morbidities). Hospital terciles of observed to expected (O/E) mortality were compared on crude rates of major and overall complications, operative mortality, and failure to rescue (among major and overall complications). The correlation between hospital observed and expected failure-to-rescue rates was assessed. Results: Median Society of Thoracic Surgeons Adult Cardiac Surgery Database predicted mortality risk was similar across hospital O:E mortality terciles (P = .10). As expected, mortality rates significantly increased across terciles (low O/E tercile: 1.6%, high O/E tercile: 4.7%; P < .001). Failure-to-rescue rates increased substantially across hospital mortality terciles among patients with major (low tercile, 8.8% and high tercile, 20.8%) and overall (low tercile, 3.0% and high tercile, 8.9%) complications. Hospital-level expected failure to rescue had a higher correlation with observed complications for overall complications (R2 = 0.71) compared with Society of Thoracic Surgeons major complications (R2 = 0.24). Conclusions: Considerable interhospital variation exists in failure-to-rescue rates following aortic valve replacement. Hospitals in the low O/E mortality tercile experience failure to rescue nearly one-third less than those in the high O/E mortality tercile. Efforts to advance quality will benefit from identifying and disseminating optimal rescue strategies in this patient population.

Comparison of Clinical Scoring Tools to Predict Heparin-Induced Thrombocytopenia in Cardiac Surgery.

The 4Ts and HIT-Expert Probability (HEP) scoring tools for heparin-induced thrombocytopenia (HIT) have not been validated in cardiac surgery patients, and the reported sensitivity and specificity of the Post-Cardiopulmonary Bypass (CPB) scoring tool vary widely in the 2 available analyses. It remains unclear which of the available scoring tools most accurately predicts HIT in this population. Forty-nine HIT-positive patients who underwent on-pump cardiac surgery within a 6-year period were loosely matched to 98 HIT-negative patients in a 1:2 case-control design. The 4Ts, HEP, and CPB scores were calculated for each patient. Sensitivity and specificity of each tool were calculated using standard cut-offs. The Youden method was utilized to determine optimal cut-offs within receiver operating characteristic (ROC) curves of each score, after which sensitivities and specificities were recalculated. Using standard cut-offs, the sensitivities for the CPB, HEP, and 4Ts scores were 100%, 93.9%, and 69.4%, respectively. Specificities were 51%, 49%, and 71.4%, respectively. The AUC of the scoring tool ROC curves were 0.961 for the CPB score, 0.773 for the HEP score, and 0.805 for the 4Ts score. Using the Youden method-derived optimal cut-off of  ≥3 points on the CPB score, sensitivity remained 100% with improved specificity to 88.9%. The CPB score is the preferred HIT clinical scoring tool in adult cardiac surgery patients, whereas the 4Ts score performed less effectively. A cut-off of ≥ 3 points on the CPB score could increase specificity while preserving high sensitivity, which should be validated in a prospective evaluation.

Nutrition Support After Cardiac Surgery: Lessons Learned From a Prospective Study.

The importance of postoperative nutrition support (NS) has been poorly recognized in cardiac surgery. In this population, we aim to describe the delivery of NS, factors affecting calorie/protein delivery and NS-associated morbidity. From January 2015 to January 2017, we prospectively observed all cardiac surgery patients at a single institution who could not take nutrition orally, requiring postoperative NS, either enteral or parenteral, for the duration of NS up to 14 days. We compared outcomes to patients without NS and examined NS indications, factors affecting its delivery and its associated complications. Nine percent of patients (232/2603) required NS for a total of 1938 NS-days. The most common indication was mechanical ventilation. NS met 69% of daily caloric needs. On days when tube feeds (TFs) were held (mean of 13 hours), this decreased to 43%, compared to 96% when TFs were not held (P < 0.001). The most common reason for holding TFs was procedures. When TFs were supplemented with parenteral nutrition (TFs + PN), 86% of daily caloric needs were met. Even on days when TFs were held, this only dropped to 77% (TFs + PN), compared to 36% (TFs-only). By multivariable logistic regression, elemental and semielemental formulas, TF volume, and postpyloric feeds increased the risk of diarrhea, occurring in 28% of patients and 18% of TF-days. In cardiac surgery patients given postoperative NS, mortality and morbidity were an order of magnitude higher than those able to be fed orally. Enteral feeding delivered approximately two-thirds of needs, but PN supplementation dramatically improved this. Diarrhea was common, associated with the postpyloric route, increasing TF volume, and nonintact formula.