Preoperative Haemodilution and the Action of Neuromuscular Blocking Agents

Abstract

The clinical concept of normovolemic haemodilution (HD) and autologous blood re-transfusion is now accepted as a safe and effective method to reduce the administration of homologous bank blood and the incidence of serum hepatitis. To study the influence of HD on the action of muscle relaxants during neuroleptanaesthesia, in a group of 47 surgical patients two units of venous blood were withdrawn preoperatively and replaced by 1000 ml of dextran 40. Haemoglobin and haematocrit changed from 14.2 ± 1.6 to 10.7 ± 1.5g/100ml resp. from 41.4 ± 3,8 to 31.4 ± 3.7%, total serum protein from 7.1 ± 0.4 to 5.3 ± 0.6 g/100 ml, and serum cholinesterase (ChE) from 5.8 ± 0.9 to 3.6 ± 0.9 U/ml. Neuromuscular blockade was quantitized by means of mechanograms of the hand muscles after supramaximal electrical stimulation of the ulnar nerve. 34 patients without HD served as controls. — Following HD the potency of d-tubocurarine (dTC), pancuronium (PC), and suxamethonium (SuM) was increased as shown by cumulative dose-response curves which displayed a parallel shift to the left, the ratio ED_{50 control}/ED_{50 HD} being 2.1 (dTC), 2.5 (PC) and 2.7 (SuM). Accordingly, the duration of action of a single ED₉₀ of dTC (0.21 mg/kg), PC (0.033 mg/kg), and SuM (0.3 mg/kg) was prolonged 1.4–1.8 times after HD.