[Oxygen economy in patients after open heart surgery--effects of cardiopulmonary bypass on oxygen metabolism].
The relationship between oxygen delivery (DO2) and oxygen consumption (VO2) was studied in thirty patients who underwent open heart surgery. Delivery dependent consumption was observed for the first 48 hours after the surgery even DO2 was in a physiological range (> 300 ml/min/m2). VO2 decreased in proportion to a decrease in DO2 (VO2 = 0.132 x DO2 + 87.9, R = 0.616, p < 0.001). Oxygen extraction rate (ER = VO2/DO2) increased also in proportion to a decrease in DO2 (ER = -0.385 x DO2 + 51.8, R = -0.722, p < 0.001). These results suggest that tissue oxygen demand in the early postoperative period is higher than physiological conditions. Factors which directly influenced ER were cardiac index (CI) and hemoglobin (Hb) as expressed in the following formulas; ER = -6.05 x CI + 51.6 (R = -0.592, p < 0.001), ER = -2.02 x Hb + 56.7 (R = -0.414, p < 0.001). This indicates that hypoperfusion and anemia deteriorate oxygen metabolism in the early postoperative period. As a monitor of oxygen demand, oxygen saturation of mixed venous blood (SvO2) was an useful parameter to indicate the ER (ER = -0.872 x SvO2 + 91.9, R = -0.969, p < 0.001).
Utoh
J
J
First Department of Surgery, Kumamoto University School of Medicine, Japan.
Miyauchi
Y
Y
Goto
H
H
Obayashi
H
H
Hirata
T
T
D000328:Adult; D000368:Aged; D006348:Cardiac Surgical Procedures; D005112:Extracorporeal Circulation; D006801:Humans; D008875:Middle Aged; D008955:Models, Cardiovascular; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
D010100:Oxygen