In 18 patients who were undergoing upper laparotomies the alveolo-arterial oxygen difference and right-to-left shunt were measured before the operation, on the first post-operative day, and in some cases also later in the post-operative period. The arterial oxygen tension was found to be considerably reduced post-operatively. The right-to-left shunt estimated by the hydrogen isotope technique was moderately increased in most instances, but the increase was far from large enough to account for the observed hypoxaemia. It is concluded that uneven distribution of ventilation relative to perfusion is the main cause of post-operative hypoxaemia, whereas veno-arterial shunt through atelectatic areas is of minor importance.

The limited usefulness of radioimmunoassays of parathyroid hormone in the differential diagnosis of hypercalcaemia invites the use of methods measuring effects of parathyroid hormone (PTH). Data from 4\p=n-\5-day metabolic studies in 107 hypercalcaemic patients (78 retrospective and 29 prospective cases) were combined in a hypercalcaemia discrimination index (HDI). HDI = (urine calcium (mg/24 h) x 100 x serum phosphate (mg/100 ml))/(serum total calcium (mg/100 ml) x 24-h clearance of creatinine (ml/min)) expresses in one figure the combined actions of PTH on the renal handling of calcium and on serum phosphate. A multivariate analysis confirmed that HDI offered optimal discrimination. An identical discrimination was observed in the prospective series. In the complete series HDI = 137 was the optimal discrimination point. Classification of the patients as having hyperparathyroidism (HPT) or pseudohyperparathyroidism (P-HPT) (< 137) or non-parathyroid hypercalcaemia (NON\x=req-\ PTH) ( #$x2267; 137) corresponded in 100 out of 107 patients (93.5%) with the final clinical diagnosis. The effects on HDI of sex, age, season, urine losses, high calcium intake and use of thiazides were also evaluated. HDI appears to be a valuable tool in the endocrine evaluation of hypercalcaemic patients. Used in combination with radioimmunoassays measuring genuine but not ectopic PTH HDI may serve to classify hypercalcaemic patients within the following 3 subgroups: HPT, P-HPT and NON-PTH.

Synthetic salmon calcitonin (sCT, doses of 0.7 Medical Research Council U per kg) was injected into nine normal subjects and three patients with hypergastrinemia (pemicious anemia). sCT depressed basal as well as food-stimulated serum gastrin concentrations without concomitant changes in total and ultrafiltrable concentrations of calcium in serum. Gel filtration of sera revealed that sCT reduced mainly the small components, III (gastrin-17 or "little" gastrin) and IV (gastrin-13 or "mini"-gastrin).