Apneic Oxygenation Versus Low-Tidal-Volume Ventilation in Anesthetized Cardiac Surgical Patients: A Prospective, Single-Center, Randomized Controlled Trial.

OBJECTIVES: To compare the physiology of apneic oxygenation with low-tidal-volume (VT) ventilation during harvesting of the left internal mammary artery. DESIGN: Prospective, single-center, randomized trial. SETTING: Single-center teaching hospital. PARTICIPANTS: The study comprised 24 patients who underwent elective coronary artery bypass grafting surgery. INTERVENTIONS: Apneic oxygenation (apneic group: 12 participants) and low-VT ventilation (low-VT group: 12 participants) (2.5 mL/kg ideal body weight) for 15 minutes during harvesting of the left internal mammary artery. MEASUREMENT AND MAIN RESULTS: The primary endpoint was an absolute change in partial pressure of arterial carbon dioxide (PaCO2). Secondary endpoints were changes in arterial pH, pulmonary artery pressures (PAP), cardiac index, and pulmonary artery acceleration time and ease of surgical access. The mean (standard deviation) absolute increase in PaCO2 was 31.8 mmHg (7.6) in the apneic group and 17.6 mmHg (8.2) in the low-VT group (baseline-adjusted difference 14.2 mmHg [95% confidence interval 21.0-7.3], p<0.001). The mean (standard deviation) absolute decrease in pH was 0.15 (0.03) in the apneic group and 0.09 (0.03) in the low-VT group baseline-adjusted difference 0.06 [95% confidence interval 0.03-0.09], p<0.001. Differences in the rate of change over time between groups (time-by-treatment interaction) were observed for PaCO2 (p<0.001), pH (p<0.001), systolic PAP (p = 0.002), diastolic PAP (p = 0.023), and mean PAP (p = 0.034). Both techniques provided adequate ease of surgical access; however, apneic oxygenation was preferred predominantly. CONCLUSIONS: Apneic oxygenation caused a greater degree of hypercarbia and respiratory acidemia compared with low-VT ventilation. Neither technique had deleterious effects on PAP or cardiac function. Both techniques provided adequate ease of surgical access.

Brain natriuretic peptide (BNP) as a biomarker of myocardial ischemia-reperfusion injury in cardiac transplantation.

OBJECTIVES: To evaluate brain natriuretic peptide (BNP) as a biomarker of ischemia-reperfusion injury in cardiac transplantation DESIGN: A prospective cohort study. SETTING: A single academic medical center. PARTICIPANTS: Adult patients undergoing orthotopic cardiac transplantation (n = 25). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The authors performed serial measurements of BNP and troponin-I in cardiac allograft donors and recipients, determining the relationship between these biomarkers and established risk factors for and measures of early graft dysfunction. Postoperative BNP correlated moderately with allograft ischemic time (ρ = 0.52, p = 0.01), donor BNP (ρ = 0.45, p = 0.03), and donor troponin-I (ρ = 0.49, p = 0.01). Postoperative BNP was higher in patients with persistently elevated inotrope requirements and enabled the early identification of such patients. In contrast, there was no association between postoperative troponin-I and these same parameters. CONCLUSIONS: Postoperative BNP is associated with preimplantation and clinical performance parameters related to allograft ischemia-reperfusion injury at the time of cardiac transplantation, providing preliminary evidence to support its potential use as an ischemia-reperfusion injury biomarker in this context.

First-in-Human Chronic Implant Experience of the Substernal Extravascular Implantable Cardioverter-Defibrillator.

OBJECTIVES: The aim of this study was to evaluate the safety and performance of an extravascular (EV) implantable cardioverter-defibrillator (ICD). BACKGROUND: Limitations of existing transvenous and subcutaneous ICD systems include lead reliability and morbidity issues associated with ICD lead implantation in the vasculature or lack of pacing therapies (e.g., antitachycardia pacing) in subcutaneous systems. The EV defibrillator uses a novel substernal lead placement to address these limitations. METHODS: This was a prospective, nonrandomized, chronic pilot study conducted at 4 centers in Australia and New Zealand. Participants were 21 patients referred for ICD implantation. Patients received EV ICD systems. Data collection included major systemic and procedural adverse events, defibrillation testing at implantation, and sensing and pacing thresholds. RESULTS: Among 20 patients who underwent successful implantation, the median defibrillation threshold was 15 J, and 90% passed defibrillation testing with a ≥10-J safety margin. Mean R-wave amplitude was 3.4 ± 2.0 mV, mean ventricular fibrillation amplitude was 2.8 ± 1.7 mV, and pacing was successful in 95% at ≤10 V. There were no intraprocedural complications. Two patients have undergone elective chronic system removal since hospital discharge. In the 15 patients presently implanted, the systems are stable in long-term follow-up. CONCLUSIONS: This first-in-human evaluation of an EV ICD demonstrated the feasibility of substernal lead placement, defibrillation, and pacing with a chronically implanted system. There were no acute major complications, and pacing, defibrillation, and sensing performance at implantation were successful in most patients. (Extravascular ICD Pilot Study [EV ICD]; NCT03608670).