Changes Of Oxygen Supply And Consumption After Acute Normovolemic Hemodilution Under General Anesthesia

Acute normovolemic hemodilution(ANH) is one of methods of blood conservation commonly used in operation. ANH is defined as the removal of blood(7.5ml/kg ~ 20ml/kg) from patients' artery or vein immediately before or shortly after induction of anesthesia, and simultaneous replacement with an appropriate volume of colloid or three-times volume of crystalloid solution, alone or in combination, such as to maintain the circulating volume. ANH is used to reduce the loss of blood cells during intraoperative bleeding and to avoid or reduce the need for homologous blood transfusion. Blood collected in standard citrate-phosphate-dextrose storage bags is kept at room temperature. The first problem ANH caused is that low hematocrit leads to decreased oxygen delivery. Under general anesthesia, because of muscle relaxants, mechanical ventilation, anesthetic inhibition, loss of consciousness and body temperature, metabolic rate and oxygen consumption decrease. Because FiO2 the anesthetized patients breathing is high even to 1, PaO2 and solved oxygen content is increased obviously according to the Henry Law. Study of the changes of oxygen supply and consumption after ANH under general anesthesia, has significant instructions for the clinical ANH during operation.In clinical conditions, we studied the changes of DO2, VO2 and ExtO2, after general anesthesia and after ANH under general anesthesia respectively, compared with epidural block condition. The index of hemodynamics and blood lactic acid concentration were detected. The main work contained two parts as follows:1. The changes of oxygen supply and consumption after general anesthesiaAim: To study the changes of hemodynamics, DO2, VO2 and ExtO2 after general anesthesia. Method: 44 ASA I ~ II patients undergoing elective general surgery, including 8 cases of cholecystectomy, 20 cases of gastrectomy and 16 cases of Colectomy, were randomly divided into group G(general anesthesia) and group E(epidural block). Hb and Hct were detected and recorded preoperatively. The valueof HR, SBP, DBF, MBP and SpO2 were measured and recorded before and after invasive procedures. The value of Hb, Hct, HR, SAP, DAP, MAP, CVP, MPAP, PAWP and CI were measured and recorded, artery blood gas and mixed venous blood gas were analyzed, the index of hemodynamics, DO2, VO2 and ExtO2 were calculated before anesthesia(T0), at 30 min(T1), 60min(T2) and 90min(T3) after anesthesia in group G and group E respectively. Results: (1) After general anesthesia, HR, SAP, SDP and MAP decreased obviously, CVP, MPAP and PAWP increased slightly, CI and SI kept stable. (2)The value of TI reflected cardiac oxygen consumption decreased respectively by 19.38% 24.80% and 31.18% at 30 min, 60min and 90min after general anesthesia compared with the value before anesthesia. (3)The proportion of solved oxygen delivery in systemic oxygen delivery rose obviously from 1.55% preanesthesia to 7.26%, 8.73% and 8.60% at 30 min, 60min and 90min after general anesthesia (4)The maximal proportion of solved oxygen delivery in systemic oxygen consumption rose obviously from 6.31% preanesthesia to 36.19%, 44.12% and 42.49% at 30 min, 60min and 90min after general anesthesia. (5)At 30 min, 60min and 90min after general anesthesia, VO2 decreased by 19.39%,18.31%and 16.57%, ExtO2 decreased by 15.27%, 20.46% and 19.53%, respectively, compared with the values before anesthesia Conclusion: After general anesthesia, hemodynamics kept stable, the cardiac consumption and systemic consumption decreased. The rise of proportion of solved oxygen delivery was advantageous to oxygen diffusion into tissue.2. The changes of oxygen supply and consumption after ANH under general anesthesiaAim: To study the changes of hemodynamics, DO2, VO2 and ExtO2 after ANH under general anesthesia respectively, and to detect blood lactic acid concentration. Method: Following the study of part one, ANH were performed in two groups. ANH is defined as the removal of blood from patients' artery with the volume according to formula V=EBV (H0-Hf)/Hav, with the removing...