CARDIOVASCULAR EFFECTS OF MODERATE NORMOVOLEMIC HEMODILUTION DURING ENFLURANE-NITROUS OXIDE ANESTHESIA IN MAN

The cardiovascular effects of mild normovolaemic haemodilution during enflurane-nitrous oxide anaesthesia were studied in 20 patients with n ormal cardiac function before, during and after total hip replacement. After induction of anaesthesia, patients were randomly allocated to o ne control group (C), or one haemodiluted group (H) where Hct was decr eased to 30% by replacement of blood volume by an identical volume of hydroxyethyl starch 200/0.5. Each patient was monitored with a pulmona ry artery catheter allowing the measurement of right ventricular eject ion fraction. During haemodilution, stroke index and right ventricular end-diastolic volume index increased from 33.1 +/- 7.9 to 39.3 +/- 7. 1 ml M(-2) and from 73.8 +/- 20.3 to 94.9 +/- 18.5 ml.M(-2) respective ly (mean +/- s.d., both P< 0.05). However, heart rate decreased so tha t cardiac index did not change. O-2 delivery decreased significantly ( from 389 +/- 70 to 311 +/- 63 ml.min(-1).m(-2) P< 0.05), but was not d ifferent to the control group. O-2 consumption was maintained by an in crease in O-2 extraction. During the surgical procedure, cardiac index was higher in the haemodiluted group than in the control group, so th at O-2 delivery was similar in the two groups. O-2 consumption tended to be greater in the haemodiluted group. In patients with normal cardi ac function, enflurane-nitrous oxide anaesthesia could alter the norma l physiologic response to mild normovolaemic haemodilution.