[The influence of neuroleptanalgesia on blood volume and circulatory pressures (author's transl)].

Studies of blood volume (Evans blue), haematocrit, arterial blood and central venous pressure (CVP) were performed in 37 patients aged 61 to 80 years, 15 h (time I) and 15 min (time II) before, and 20 min after (time III) induction of neuroleptanalgesia (NLA) with fentanyl 0.004 mg and droperidol 0.2 mg per kg body weight. The patients underwent total hip arthroplasty for degenerative joint disease. 11 male and 11 female patients had no other medical disorders ("normal" group). 6 had considerable obesity and 9 had hypertension. The mean blood volume was lower in the female patients in comparison with the male patients and lower in the obese and hypertensive patients in comparison with the "normal" subjects. Between time I and II there was little decrease of blood and plasma volume and increase of haematocrit in the "normal" group. In the hypertensive patients the reverse was true. During this time the mean blood pressure decreased in the hypertensive patients only. CVP remained unchanged in each group. Between time II and III blood pressure and CVP decreased in all groups studied. A haemodilutional effect of NLA expressed by significant decrease of haematocrit and increase of blood and plasma volume was observed in each group. After induction of NLA we found a close correlation of CVP, systolic and diastolic blood pressure with blood volume. These observations firmly suggest that NLA expands vascular capacity. Consequently NLA may lead to a marked fall of blood pressure in hypovolaemic patients. This is important, particularly in hypertensive patients who usually have low blood volumes.