Feasibility Study Of Acute Hypervolemic Hemodilution In Patients Undergoing Gastrointestinal Operation During Induction Of General Anesthesia

Objective During induction of general anesthesia, the patients will experience the changes from physiological state to being anesthesized state. Great change of hemodynamics is usually the commonest problem and is always difficult to deal with to the anesthesiologist.The purpose of the study is to investigate the safety and effective- ness of acute hypervolemic hemodilution (AHH) in patients undergoing gastrointestinal operation during induction of general anesthesia by observing the changes of hemodynamics, constitution oxygenation and electrolyte and to provide clinical bases for the reasonable enforcement of AHH during induction of general anesthesia.Methods Twenty ASA I～II patients without cardiac and pulmonary disease of both sexes aged 22-65 years undergoing elective gastro- intestinal surgery were randomly divided into two groups: Voluven group ( group A, n=10) and Plasmalyte A group ( group B, n=10). Radial artery and right subclavian vein were cannulated under local infiltration for MAP (Mean Arterial Pressure) and CVP (Central Venous Pressure) monitoring. ECG(Electrocardiogram),Sp0₂ (Pulse Oxygen Saturation )and PeTCO₂(Partial Pressure of Carbon Dioxide in Endexpiratory Gas) were continuously monitored during anesthesia. Anesthesia was induced with midazolam 0.05 mg·kg^-1 ,fentanyl 3μg·kg^-1 ,propofol 1.5—2.0 mg·kg^-1 in divided doses and vecuronium 0.1 mg·kg^-1 .After tracheal intubation the patients were mechanically ventilated and P_ETCO₂ was maintained at 35～45 mmHg. Anesthesia was maintained with isoflurane and intermittent i.v.doses of fentanyl and vecuronium. Patients of group A received Voluven (Hydroxyethyl Starch 130/0.4) 7 ml·kg^-1 in 20 mins before induction and 8 ml·kg^-1 after induction. Patients of group B received Plasmalyte A (Multiple Electrolytes Injection) as the method of group A.MAP,HR and CVP were recorded before AHH(T₀),before intubation (T₁) ,after intubation(T₂), 5min after intubation(T₃), 10min after intubation(T₄), 20min after intubation(T₅) and before operation(T₆) respectively. Arterial and venous blood samples were taken for blood gas analysis and determination of lactic acid,electrolyte,Hb and Hct before AHH,after AHH and 1h after AHH. Arterial Oxygen Content (CaO₂), Central Venous Oxygen Content (CcvO₂), Oxygen Extraction Ratio (ERO₂) and fluid expansion rate (FER) were calculated. The following is formula: CaO₂=(Hb×1.34×SaO₂+PaO₂×0.00315)×10(ml·L^-1)CcvO₂=Hb×1.34×ScvO₂+PcvO₂×0.00315)×10(ml·L^-1)ERO₂= VO₂/DO₂=[CIx( CaO₂ -CcvO₂)]/(CI×CaO₂ )= ( CaO₂ -CcvO₂) / CaO₂ (%)FER= (Hct before AHH-Hct after AHH) / Hct before AHH(%) Results1. Demographic profileBoth of the groups were comparable in age, weight,height and baseline Hb and Hct of the patients(P > 0.05).2. Changes on hemodynamics: 2.1 Changes on MAP:Within the groups, although MAP decreased at Ti compared with To (P < 0.01), its descendent degree was little combing with clinic; MAP increased at T₂ compared with T₀ (P < 0.01). There were no significant differences at T₃～T₆ compared with T₁ (P > 0.05).There were no significant differences between group A and group B at the corresponding points (P > 0.05). 2.2 Changes on HR:Within the both groups, HR was significantly slower after induction compared with the baseline.There were no significant differences between group A and group B at the corresponding points (P > 0.05).2.3. Changes on CVP:CVP grandually increased following with the increasing of transfusion, but they were all within normal limits.3. Changes on Hb and Hct:Within group A, Hb and Hct significantly decreased after AHH and 1h after AHH compared with those before AHH (P<0.01). Within group B Hb and Hct significantly decreased after AHH compared with those before AHH but significantly increased 1h after AHH and there were no significant differences in Hb and Hct compared with the baseline(P > 0.05).Between group A and group B, there were significant differences in Hb and Hct at the moment of 1h after AHH(P < 0.05).Fluid expansion rate: A > B, lasting time of fluid expansion: A > B. 4. Changes on blood gas and lactic acid:PH increased within group B after AHH, furthermore exceeded the normal value but gradually returned to the baseline 1h after AHH; BE slightly increased after AHH within the normal value; HCO₃^- unchanged before and after AHH. Lactic acid increased both in group A and group B 1h after AHH.5.Changes on CaO₂,CcvO₂ and ERO₂:CaO₂ and CcvO₂ decreased after AHH and 1h after AHH within group A. Within group B CaO₂ and CcvO₂ decreased after AHH but returned to the baseline 1h after AHH. ERO₂ un- changed within both of the groups.6. Changes on electrolytes and Glucose:Na⁺,K⁺,BUN unchanged within both groups; Cl^- decreased within group B after AHH, but returned to the baseline 1h after AHH; Glu gradually increased in both groups.Conclusion 1. The effect of rapid plasma Volume expansion with crystalloid or colloid on prevention of hypotension during induction is similar.2. Plasmalyte A was superior to stabilize physiological internal environment.3. Vouven was safety and effective during induction of general anesthesia; its dilatation and the time of maintainance was superior than Plasmalyte A.