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Fazadinium was administered as an intravenous bolus of 0.5 or 1 mg/kg to nine patients during neurolept-anaesthesia. Continuous recording of neuromuscular activity and serial collection of blood samples for drug assay allowed the relationship between neuromuscular blockade and plasma fazadinium concentration to be studied. Pharmacokinetic analysis demonstrated high plasma clearances (221 and 185 ml/min), and short terminal half-lives, (30 and 50 min), for the two doses of the drug. Mean plasma concentrations at 10 and 50% recovery were 1.42 and 0.88 micrograms/ml respectively, demonstrating that the potency of fazadinium is approximately half that of tubocurarine and one eighth that of pancuronium. In addition, the relationship between plasma concentration and depression of neuromuscular activity during spontaneous recovery from the relaxant is described.

Autonomic failure in patients with the Shy-Drager syndrome may produce cardiovascular instability during anaesthesia and surgery. The syndrome is reviewed and the anaesthetic management of a case is described. The choice between general and regional anaesthesia seems to be less important than adequate cardiovascular monitoring and the maintenance of blood pressure with intravenous fluids. Sympathomimetic drugs, if used at all, should be administered in very dilute solutions to avoid hypertension from denervation hypersensitivity. In the postoperative period, symptoms from orthostatic hypotension may be severe and their control requires prolonged postural training, by elevation of the head of the bed, and therapy with 9-alpha-fludrocortisone.

Technical advances have made the bedside measurement of colloid osmotic pressure (COP) a rapid and reproducible test. The principles of measurement are described and the place of COP determinations in the recognition, treatment and prophylaxis of oedematous states is discussed.

Suxamethonium was administered to patients during recovery from non-depolarising muscle relaxation. The effect of suxamethonium varied depending upon the degree of recovery from the non-depolarising block when it was administered. Early in recovery suxamethonium produced reversal of the non-depolarising block without paralysis whereas when administered later, initial recovery of the non-depolarising block was followed by paralysis. If administered after 50% recovery the predominant effect was paralysis without initial recovery. Assessment of neuromuscular blockade with train-of-four stimulation showed that the paralysis produced by suxamethonium under these circumstances, had depolarising and non-depolarising features.

Edrophonium was administered as a bolus of 2, 10 or 50 mg (0.03, 0.14 and 0.71 mg/kg) to antagonize neuromuscular block after pancuronium in man. Neuromuscular transmission was measured using "train-of-four" stimulation. Recovery started within 1 min, was maximum at 2 min and was then followed by a plateau of slow continued improvement. The degree of recovery increased with larger doses of edrophonium and also was related to the total amount of pancuronium administered although reversal was attempted at the same degree of spontaneous recovery. There was no evidence of recurarisation or depolarising block.

During pregnancy there is a fall in functional residual capacity and expiratory reserve volume. The point of airway closure in relation to vital capacity and the expiratory reserve volume was determined in 11 post-partum patients who had previously been studied during pregnancy. The lung volume at which airway closure occurred in pregnancy and the post-partum period did not change in relation to the vital capacity whereas the expiratory reserve volume did, so that airway closure became imminent in the pregnant women during tidal ventilation, especially whilst in the suping position. The significance of this alteration in pulmonary function to obstetric anaesthesia is discussed.

The hourly urine volume and urine concentration of seven patients undergoing major abdominal surgery were measured during the operative and postoperative periods. From these, the hourly osmolar output was calculated. The results show that the osmolar output, 700 mOsm/day, in the peri-operative period is less than that of a 70 kg man consuming a normal 2000 calorie diet. Calculation of the osmolar output might help in the differentiation of postoperative oliguria and renal dysfunction.

Measurement of plasma and urine osmolality is quick, easy and accurate. The recognition of the interdependence of urine volume and osmolality on the excretion of the daily obligatory solute load assists in the diagnosis and management of fluid balance and renal excretory problems in the acutely ill. In addition, syndromes of osmotic disequilibrium present a challenge in metabolic care.

The maintenance of osmolar constancy of the body fluids is dependent upon the recognition of osmolar disequilibrium and its correction by modifying the ingestion and excretion of fluid and solute. Osmolar changes are sensed by the hypothalamus which regulates the secretion of antidiuretic hormone to modify the renal excretion of water. The integrity of the system depends upon the renal ability to vary the solute concentration of urine.

The measurement of the osmolality of body fluids is used increasingly in clinical practice. This paper discusses the terminology and describes the methods available for its measurement.