Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Cardiovascular Anesthesia
INTRODUCTION: Patients receiving nitroglycerine (NTG) infusion during medical treatment required higher heparin doses to achieve an adequate increase in aPTT . NTG and heparin are often used together during cardiopulmonary bypass (CPB). ACT is used to determine the anticoagulant effect of heparin during CPB. In this prospective controlled study the effect of NTG on ACT was investigated in heparinized patients during cardiac surgery under normothermic and mild hypothermic conditions ex vivo.
METHODS: Following IRB approval, informed consent was obtained from 20 adult patients undergoing cardiac surgery requiring CPB. Patients receiving NTG infusion were excluded. Blood volume was calculated according to percentage of body weight prior to and following addition of prime solution (2250 ml) . A 2 [micro sign]g/ml solution of NTG in %0.9 saline was prepared for each patient with commercially available NTG preparation in a glass container. Each patient was assumed to receive a bolus dose of 0.5 mg and 5 mg NTG. NTG concentration in 10 ml of blood volume at the time of sampling was calculated. Blood was obtained from the patients; I) Prior to heparinization at normothermia, II) During CPB at 32[degree sign]C and III) During CPB at 30[degree sign]C (rectal). ACT (Medtronic Hemotec, Eaglewood Col.) and whole blood count (Hemoglobin, hematocrit and platelet count) (Coulter Microdiff 18, Miami Fl.) were performed simultaneously; before (control) and after both NTG additions (calculated doses of 0.5 mg and 5 mg bolus). Addition of prime solution was considered in calculating NTG concentration for the 2nd and 3rd sampling. Repeated measures ANOVA and posthoc Tukey's HSD test was used for significant variables. Values are expressed as mean +/- SD.
RESULTS: NTG addition (in both doses) did not change ACT values compared to control values at normothermic or hypothermic conditions (Table 1). Hemoglobin, hematocrit values and platelet counts were significantly lower during CPB compared to baseline values (p<0.05). NTG addition did not cause a significant change in whole blood count components compared to control values.
DISCUSSION: NTG is often used during cardiac surgery, however highest toxic or effective dose has not been defined yet . Since the dose requirement is quite variable during CPB a controlled study in patients receiving peroperative NTG during cardiac surgery is difficult to perform. Results of this ex vivo study demonstrate that concomitant use of NTG and heparin does not have any effect on ACT values during CPB.
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