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 (PaCO 2 ). 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 PaCO 2 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 2 (p 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.