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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<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 PaCO 2 (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., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: To assess the usefulness of central venous pressure (CVP), diastolic right ventricular pressure, and pulmonary capillary wedge pressure (PCWP) waveform analysis in predicting fluid responsiveness., Design: A prospective observational study., Setting: Tertiary care university hospital., Patients: Forty-four patients undergoing coronary artery bypass grafting., Interventions: Analysis of the a/v wave ratio of the PCWP, CVP, and right ventricular dP/dt to predict an increase in stroke volume >15% after the administration of 500 mL of colloid., Measurements and Main Results: Forty-four patients were enrolled in this study and 7 were excluded. There were 24 responders and 13 nonresponders. No differences in mean CVP and PCWP values between the responders and the nonresponders were found. The only parameter associated with a significant response to volume infusion was the ratio of the a/v waves of the PCWP tracing (p = 0.0001). The performance of the a/v wave ratio>1 of the PCWP tracing in predicting fluid responsiveness was evaluated by constructing a receiver operating characteristic curve. The area under the receiver operating characteristic curve was 0.89 (95% confidence interval, 0.79-0.99; p<0.05)., Conclusions: The a/v ratio measured on the PCWP tracing is a predictor of fluid responsiveness in patients with preserved left ventricular function undergoing coronary artery bypass grafting., (Copyright © 2013 Elsevier Inc. All rights reserved.)