[Effect of preoperative continuous nifedipine maintenance medication on hemodynamics and myocardial lactate extraction in coronary surgery patients].

The cardioprotective efficacy of preoperatively maintained long-term oral nifedipine application to 21 patients undergoing coronary artery bypass grafting (CABG) was investigated during fentanyl-N2O-anaesthesia. Two groups were defined at random; one group of patients receiving their normal morning doses together with the premedication, the other, who received the last nifedipine medication in the evening before surgery. Measurements where performed: 1. before induction of anaesthesia (reference value), 2. after induction, 3. at skin incision, 4. during sternotomy. There were no significant differences of hemodynamic parameters between the two groups. The hemodynamic parameters heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), and coronary perfusion pressure (CPP) decreased after induction in accordance with the plasma-concentrations of epinephrine and norepinephrine in both groups and increased again during sternotomy with HR and CI remaining below and MAP and CPP rising above the reference value. The nifedipine-plasma-concentrations were significantly higher in the group with the morning dose and just within the minimal therapeutic range before and after induction of anaesthesia. But during skin incision and sternotomy the plasma levels fell below 10 ng/ml, i.e. below the therapeutic level. The incidence of myocardial lactate extraction values greater than 10% was highest immediately after induction of anaesthesia and lowest during sternotomy with one patient in both groups exhibiting negative lactate extraction as a symptom of myocardial ischemia. The results suggest that the preoperatively maintained oral nifedipine medication of 10-20 mg p.o. was not able to provide sufficiently high nifedipine-plasma-levels during sternotomy nor to improve the hemodynamic state in patients with CABG.(ABSTRACT TRUNCATED AT 250 WORDS)