Oxygen Transport in Pulmonary Oxygenizing Dysfunction in the Early Periods after Extracorporeal Circulation

Abstract

Objective: to study the specific features of oxygen transport function in patients with various oxygen delivery changes caused by alveolar opening maneuver (mobilization) performed early after extracorporeal circulation. Subjects and methods. Alveolar opening maneuver was made in the presence of relative arterial hypoxemia under the control of dynamic thora-copulmonary compliance. The maximum airway pressure was as high as 31.1±0.3 cm H2O; the positive end-expiratory pressure was 16.0±0.3 cm H2O. According to the changes in oxygen delivery after alveolar opening maneuver, the investigators retrospectively identified the following groups: 1) (n=14) with a lower and 2) (n=15) higher values. The groups did not differ in age (53.6±2.8 and 56.4±1.8 years), extracorporeal circulation duration (106.4±11.2 and 86.8±4 min), and inotropic support intensity (4.7±0.5 and 4.6±0.6 ^g/kh/min for dopamine and/or dobutamine) (p>0.05). The mode of alveolar opening maneuver and its impact on thoracopulmonary compliance and pulmonary oxygenizing function were identical in the groups (p>0.05). Results. 48.3% of the patients with relative arterial hypoxemia show a linear relationship between the oxygen delivery and consumption indices (r=0.73; p=0.003), and there was a close inverse correlation between the oxygen utilization coefficient and intrapulmonary shunting (r=-0.77; p=0.001). After alveolar opening maneuver, the oxygen delivery index decreased in these cases from 440.7±31.7 to 376.9±20.4 ml/min/m2 (p<0.05). The time course °f changes oxygen delivery influenced mixed venous hemoglobin oxygen saturation (r=-0.71; p=0.005), which was related to lactatemia before (r=0.71; p=0.004) and after (r=0.7; p=0.005) alveolar opening maneuver. Conclusion. After extracorporeal circulation, relative arterial hypoxemia may be concurrent with the signs of oxygen transport system tension in patients with impaired pulmonary oxygenizing function. Moreover, regional blood flow impairments in the peripheral tissues and those in the lung are closely related. After alveolar opening maneuver that improves pulmonary oxygenizing function, oxygen delivery decreases, affecting mixed venous hemoglobin oxygen saturation. The findings give grounds to recommend close monitoring and timely correction during alveolar mobilization in the early period after cardiosurgery. The specific features of oxygen transport and utilization during standard interventions into the heart under extracorporeal circulation call for further in-depth studies. Key words: oxygen transport, oxygen delivery and consumption, alveolar opening maneuver (mobilization), arterial hypoxemia in cardiosurgical patients.