We would like to thank Dr. Freundlich and colleagues for their informed comments regarding our study. The concerns regarding the lack of adjusting the analysis to reflect serum pH, serum lactate, and the cationic difference between calcium gluconate and calcium chloride are points well taken. Serum pH does impact free calcium levels through ionic coupling with bicarbonate. In vivo this equilibration occurs very quickly. Thus measured iCa 2+ levels reliably reflect available calcium stores unless the pH is changing very rapidly. Error can be introduced into iCa 2+ measurements if samples are stored for a long period of time before being analyzed. In refrigerated samples, the pH generally drops and the measured iCa 2+ will be falsely elevated whereas the opposite occurs in frozen samples. All of the labs we report were from fresh samples. Lactate is known to bind calcium similar to

Objective: Anticoagulation may be a challenge in coronavirus disease 2019 (COVID-19) extracorporeal membrane oxygenation due to endothelial injury and dysregulation of coagulation, which may increase the risk of thrombotic and bleeding complications. This report was created to describe the authors' single institutional experience, with emphasis on the high rate of intracranial hemorrhage for the first 10 patients with COVID-19 placed on venovenous extracorporeal membrane oxygenation (VV ECMO). Design: Case series, retrospective analysis. Setting: Single institution. Participants: Ten patients. Interventions: None. Measurements and Main Results: Patient characteristics, mortality, stroke rate, and length of stay data were collected in all patients. In addition, laboratory values of D-dimer and C-reactive protein and standard measurements of prothrombin and activated partial thromboplastin time were collected on all patients. Ten patients, each confirmed with COVID-19 via reverse transcription-polymerase chain reaction, were supported on VV ECMO for acute respiratory distress syndrome (ARDS) for a mean duration of 9.4 § 7 days. Four of 10 patients had hemorrhagic strokes, 3 of which resulted in death. At 30 days after initiation of VV ECMO, a total of 7 survivors included 6 patients discharged from the hospital and 1 patient who remained in the intensive care unit. Conclusions: In this small study of 10 patients, intracranial hemorrhage was a common complication, resulting in a high rate of death. The authors urge caution in the anticoagulation management of VV ECMO for patients with severe ARDS and COVID-19 patients. Close monitoring of all hematologic parameters is recommended during ECMO support while awaiting larger, multicenter studies to examine the best practice.

Background: Coronary artery bypass graft (CABG) surgery is the most widely performed cardiac surgery in the United States. Transesophageal echocardiography (TEE) is frequently used in a variety of cardiac surgical procedures, but its clinical benefit in isolated CABG surgery is unclear, and guidelines remain indeterminate. The aim of this study was to compare clinical outcomes among patients undergoing isolated CABG surgery with versus without TEE in order to test the hypothesis that TEE would be associated with improved clinical outcomes after CABG surgery.Methods: A matched retrospective cohort study was conducted among Medicare beneficiaries undergoing isolated CABG surgery with versus without intraoperative monitoring using TEE in the United States. The primary analysis was a near/far instrumental variable match that paired hospitals with similar characteristics and patient populations but with opposing probabilities for using TEE in CABG surgery. Outcomes included 30-day mortality, a composite outcome of stroke or 30-day mortality, length of hospitalization, and incidence of esophageal perforation.Results: Of 114,871 patients undergoing isolated CABG surgery, 65,471 (57%) underwent TEE and 49,400 (43%) did not. Hospital-level instrumental variable matched analysis demonstrated that among the subset of 968 matched hospitals, TEE receipt was associated with lower 30-day mortality (3.7% vs 4.9%, P < .001), a lower incidence of the composite outcome of stroke or 30-day mortality (4.5% vs 5.6%, P < .001), no difference in length of hospitalization (10.32 vs 10.52 days, P = .26), and no difference in the incidence of esophageal perforation (0.01% vs 0.01%, P = .63). These results were replicated in surgeon-level and patient-level matched-pair instrumental variable analyses, and all analyses were robust to sensitivity analyses that tested for biases introduced by unmeasured confounding. Conclusions:The findings from this study suggest that TEE may offer a clinical benefit to cardiac surgical patients undergoing isolated CABG surgery.

Background: Despite recommendations regarding the use of intraoperative transesophageal echocardiography (TEE), there is no randomized evidence to support its use in cardiac valve surgery. The purpose of this study was to compare the clinical outcomes of patients undergoing open cardiac valve repair or replacement surgery with and without transesophageal echocardiographic monitoring. The hypothesis was that transesophageal echocardiographic monitoring would be associated with lower 30-day mortality and shorter length of hospitalization. Methods: In this observational retrospective cohort study, Medicare claims were used to test the association between perioperative TEE and 30-day all-cause mortality and length of hospitalization among patients undergoing open cardiac valve repair or replacement surgery between January 1, 2010, and October 1, 2015. Baseline characteristics were defined by inpatient and outpatient claims. Medicare death records were used to ascertain 30-day mortality. Statistical analyses included regression models and propensity score matching. Results: A total of 219,238 patients underwent open cardiac valve surgery, of whom 85% underwent TEE. Patients who underwent TEE were significantly older and had greater comorbidities. After adjusting for patient demographics, clinical comorbidities, surgical characteristics, and hospital factors, including annual surgical volume, the TEE group had a lower adjusted odds of 30-day mortality (odds ratio, 0.77; 95% CI, 0.73 to 0.82; P < .001), with no difference in length of hospitalization (<0.01%; 95% CI, À0.61% to 0.62%; P = .99). Results were similar across all analyses, including a propensity score-matched cohort. Conclusions: Transesophageal echocardiographic monitoring in cardiac valve repair or replacement surgery was associated with lower 30-day risk-adjusted mortality, without a significant increase in length of hospitalization. These findings support the use of TEE as routine practice in open cardiac valve repair or replacement surgery.