Effects Of Acute Hypervolemic Hemodilution During Induction Of Anesthesia In Geriatric Patients

In recent years, the population of elderly people is increasing rapidly in our country with the development of economy and the enhancement of living standards. So is the elderly patients who need surgery. Anesthesia for the elderly is now being payed more attention than ever before. Because of decreased tolerance to the anesthetics in elderly patients, it is very important for the anesthesiologist to maintain stable hemodynamics and the surgeon reduce the blood loss during operation in the elderly,which can avoid the complications of blood transfusion and help the recovery of the patients afteroperation .During induction of 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.Hemodilution, which at first was used as an effective technique for decreasing blood viscosity, is now widely used as an effective technique for blood saving while maintaining the stability of intra-operative hemodynamics . Hemodilution is usually classified into hypo-,normo-,and hyper-volemic hemodilution according to the blood volume after hemodilution. Acute normovolemic hemodilution(ANH) and acute hypervolemic hemodilution are mainly used in patients undergoing operation. Acute normovolemic hemodilution is administered preoperatively by withdrawing the patient's blood and simultaneously infusing equal volume of crystalloid or colloid solutions. Acute hypervolemic hemodilution(AHH) is administered by hemodiluting the patient with crystalloid or colloid solutions preoperatively without removing their autologous blood. As a new technique for blood saving, AHH is a simple as well as time- and cost-saving alternative to ANH.It has been confirmed that AHH can maintain stable hemodynamics during operation and reduce requirement for homologous blood transfusion during surgery. However, the systemic study of AHH in elderly during induction has not been reported.Hypovolaemia usually exists in the patient before induction because of fasting pre-operatively and will always be aggravated by the vasodilation effects of the anesthetics, so there exists the necessity and importance to administer AHH during induction. There are still no systemic study on AHH during induction and the safety and effectiveness of the AHH during induction have not been fully elucidated.The purpose of this study is to investigate the safety and effectiveness of AHH during induction by observing the changes of hemodynamics, constitution oxygenation, cardiac troponin I, myoglobin and myocardial enzyme in elderly and to provide clinical bases for its administration in geriatrics. Indications for use of the technique might be broadened if it can be shown to be safe in elderly patients.Materials and Methods: Thirty patients (15 men and 15 women) undergoing acute hypervolemic hemodilution were randomly divided into three groups: Group A(AHH with HES),Group B(AHH with Ringer's solution) and Group C(control group).Their ages were 60-75yr and their weights 55-75kg. All patients scheduled for elective abdominal surgery were ASA I — II class without evidence of cardiopulmonary disease and history of hypertention. Their preoperative Hct was ^ 35%andHb^ llOg/L.The patients were premedicated with intramuscular atropine0.5mg and luminal O.lg. Anesthesia was induced with etomidate OJing-kg'1 ,remifentanyl 2ug-kg"1and succinylcholine 1.5mg-kg'1 and maintained with propofol O.lmg-kg^-min"1 and remifentantl O.lug-kg^-min"1. Muscle relaxation was maintained with intermittent intravenous boluses of vecuronium .The patients were mechanically ventilated after tracheal intubation and PEtCO2 was maintained at 35~40mmHg. Radial artery was cannulated for intra-arterial pressure monitoring and blood sampling and subclavian vein were cannulated for CVP monitoring and blood sampling. Heart Rate(HR), Electrocardiogram(ECG), Mean Arterial Pressure(MAP),and Central Venous Pressure(CVP) were monitored continuously throughout operation.In all patients, Ringer solution 6~8ml*kg"1 was infused to compensate for preoperative fluid restriction after midnight. AHH was performed by infusing ISml-kg"1 HES or Ringer solution at a rate of 25 ml-min'1. HES or Ringer solution 7 ml-kg"1 was infused before induction and 8 ml-kg'1 after induction.During operation blood loss was replaced with equal volume of 6%HES. Blood transfusion was considered to maintain appropriate Hct or Hb( Hb^9g/dl, Hct^= 25%).MAP> HR and CVP were recorded before AHH(T0),before intubation(Ti) ,after intubation(T2), 5min after intubation(T3), lOmin after intubation(T4), 20min after intubation(T5) and beforeoperation(T6) respectively. Artery blood samples were taken before and after AHH for blood gas analysis and determination of HCT, HB and lactic acid concentration. Central venous blood samples were taken before AHH, 4 hour and 24 hour after AHH respectively for determination of cardiac troponin I , myoglobin and myocardial enzyme concentration.All data were expressed as median or mean±SD. To study the pattern of changes in individual hemodynamic variables in each group during various phases of study, an analysis of variance for repeated measures was performed. When the F value showed a significant difference(p<0.05),a Student-Newman-Keuls test for all possible comparisons was performed to detect differences among phases. The hemodynamic data at same phase of study were compared among the three groups by using one-way analysis of variance .Blood transfusion and dosage of ephedrine were compared by using the nonparemetric Kruskal-Wallis test. Where appropriate , p<0.05 was considered significant. Results 1. Demographic profileThe three groups were comparable in age, sex, weight, and baseline HCT of the patients(P>0.05). The age ranged from 60 to 75yr-2.Changes on hemodynamicsChanges on MAP: Within the AHH groups (group A or group B), there were no significant alterations during induction of anesthesia(P > 0.05).Within C group,the MAP decreased significantly at TL~T6 compared with the baseline(P < 0.05). Although the baseline MAP in the three groups was comparable(P>0.05), MAP was significantly higher in the AHH groups than the control group at the corresponding points (P < 0.05) .Changes on CVP: Within AHH groups, there were no significant alterations in the CVP at Tl5 T2 points, although CVP at Tb T2 was higher compared with To. However, CVP at Ts~T6was significantly higher compared with To (P < 0.05).Within C group, there was no significant changes during induction of anesthesia (P>0.05) . The baseline CVP in the three groups was comparable(P>0.05). AT 1\, T2 points, CVP was higher in AHH groups than in the control group, but it was not significant. At T3~-T6, CVP was significantly higher in the AHH groups than the control group at the corresponding points (P < 0.05).Changes on HR: Within the three groups, the HR was significantly slower after induction compared with the baseline. There was no significant difference in the HR among the three groups at the corresponding points (P < 0.05). 3.Changes on HCT, HBWithin AHH groups, HCT and HB decreased significantly afterAHH compared with those before AHH (P < 0.01). Within C group, there was no significant alterations during induction of anesthesia(P> 0.05).The baseline HCT and HB in the three groups were comparable(P>0.05). HCT and HB in the AHH groups decreased significantly than in the control group(P < 0.01), but there was no significant difference in HCT and HB between group A and group B(P >0.05). 4.Changes on PH ,K+ ,Na+ ,Ca2+and Lactic acidWithin the three groups ,there were no significant changes on PH ,K+ ,Na+ ,Ca2+and Lactic acid before and after AHH(P>0.05). There was no significant difference in the PH ,K+ ,Na+ ,Ca2+and Lactic acid among the three groups at the corresponding points (P>0.05). 5.Changes on cardiac troponin I, myoglobin and creatine kinase isoenzymeWithin the three groups, there was no significant alterations in cardiac troponin I before and after AHH(P > 0.05), however, concentrations of myoglobin and creatine kinase isoenzyme at 4 hour and 24 hour after AHH were significantly higher than those before AHH(P < 0.01). There was no significant difference in the concentrations of cardiac troponin I, myoglobin and creatine kinase isoenzyme among the three groups at the corresponding points (P> 0.05). 6.Dose of ephedrineDose of ephedrine was significantly different among the three groups (P < 0.05).More ephedrine was used in control group than in the AHH groups. 7.0ther dataThere was no significant difference among the three groups in induction time ,operation time , fluid infusion volume and blood loss during operation(P>0.05).There was significant difference between the AHH groups and the control group in urine output and fluid infusion(P < 0.05).The amount of allogeneic blood was significantly different among the three groups(P < 0.05).Conclusions:1. Acute hypervolemic hemodilution(AHH) with ISml-kg"1 HES or Ringer's solution can be safely used in geriatric patients who have no evidence of heart and lung disease. There were no significant alterations in cardiac troponin I and lactic acid concentration before and after AHH.2. AHH during induction of anesthesia can avoid the great changes of hemodynamics in the elderly patients and help maintain stable hemodynamics during operation.3. Mild-degree AHH has no effects on acid-base balance and electrolyte.4. The procedure of AHH seems to be a simple as well as time- andcost-saving blood conservation strategy. AHH can be used extentively in all typs of surgeries and its indications can be broadened.