RESUMO
Objective To investigate the effects of acute hypervolemie hemodilution(AHH)combinedwith bypotension(CH)on hemodynamies and tissue perfusion and to evaluate the safety of the technique.MethodsForty-eight ASA Ⅰ-Ⅱ patients of both sexes(28 male,20 female)aged 41-63 yr weighing 47-85kg undergoingelective orthopedic operations were randomly divided into 4 group with 12 patients in each group:A control group;B CH group;C AHH group and D CH+AHH group.The patients were premedicated with oral diazepam 10 mgand intramuscular atropine 0.5 mg.Anesthesia was induced with midazolam 0.04 mg?kg~(-1),fentanyl 4?g?kg~(-1),propefol 1.5-2.0 mg?kg~(-1) and vecuronium 0.1 mg?kg~(-1) and maintained with inhalation of 1%-3 % isoflurane and50% N_2O in O_2 supplemented with intermittent i.v.boluses of vecaronium.The patients were mechanicallyventilated after tracheal intubation(V_T=8-10 ml?kg~(-1),RR 12 bpm).Radial artery and right internal jugular veinwere cannulated.The CVP catheter was inserted into right atrium and the blood obtained from right atrium was usedto replace mixed venous blood.ECG,MAP,HR,CVP,SpO_2 and urine output were continuously monitored duringoperation.Controlled hypotension was induced with sodium nitroprusside(NTP)at 0.1-2 ?g?kg~(-1)?min~(-1) andMAP was maintained at 70% of the baseline MAP during operation.NTP infusion was terminated 30 min beforethe end of surgery.AHH was induced with 6% HES 15 ml?kg~(-1) at 50 ml?min~(-1) after induction of anesthesia andbefore skin incision.Blood samples were taken from radial artery and right atrium before AHH(T_0,baseline),immediately after AHH or before CH(T_1),1h after AHH or 40 min after start of CH(T_2),at the end of surgeryor 30 rain after termination of NTG infusion(T_3)and 24h after surgery(T_4)for blood gas analysis and calculationof oxygen extraction ratio(ERO_2).Blood volume was maintained with infusion of colloid and lactated Ringer'ssolution.The amount of blood loss and blood transfusion were recorded.Hb was maintained above 70 g?L~(-1)Results CVP increassd significantly after AHH in group C and D as compared to baseline(P0.05).Conclusion AHH combined with CH can maintain stable hemodynamics,decrease blood loss andblood transfusion during operation and maintain the balance between oxygen delivery and oxygen consumption.
