No abstract

The effects of atropine and oxprenolol on changes occurring in total catecholamine, cyclic AMP (cAMP) and lactate concentrations in arterial and coronary sinus blood, during submaximal isometric exercise, were studied in 10 patients. Static one-third-maximal handgrip exercsie, sustained for 5 minutes, did not produce an increase in either arterial or coronary sinus plasma catecholamine concentrations (measured at rest and during the last minute of exercise) and was not influenced by atropine and oxprenolol. Myocardial lactate production did not occur. Coronary sinus cAMP concentrations fell during isometric exercise from 11.53 ± 0.93 to 9.42 ± 0.81 nmol/l ( ± SEM), and following autonomic blockade from 12.46 ± 1.12 to 9.6 ± 0.87 nmol/l but rose on subsequent isometric exercise to 11.27 ± 0.8 nmol/l (p < 0.05). Although this latter increase could still be due to β-adrenergic stimulation, the absence of any change in catecholamine concentrations in the presence of β-blockade suggests that other factors may have been responsible.

. (1973). Thorax, 28,[762][763][764][765][766][767]. Effect on blood volume of maintaining a high central venous pressure after major aortic valve surgery. Serial blood volume measurements were made in 15 patients undergoing major aortic valve surgery requiring cardiopulmonary bypass. In all patients the plasma volume was measured by iodine-125 (125I) labelled albumin and in 10 the red cell mass was measured by chromium-5 1 (51Cr) labelled red cells. Close correlation was found between the blood volume derived from the plasma volume and central venous haematocrits and the blood volume derived by addition of the plasma volume and red cell mass. Postoperatively blood was given to maintain the right atrial pressure at between 10 and 15 cm H20. Before operation the red cell mass, and plasma and blood volumes related to body weight were within the normal range. In the postoperative phase the first measurement two hours after the end of the operation showed a significant decrease in mean blood volume, red cell mass, and plasma volume as compared with the preoperative level. By the second postoperative measurement six hours after the end of operation the mean blood volume had risen to the preoperative level. Subsequently, over postoperative days 1 to 6 the mean blood volume remained steady, although the red cell mass tended to fall. After blood transfusion had ceased the red cell mass usually showed a progressive fall. It was considered that although there was little relationship between the right atrial pressure and the blood volume there was little or no clinical value in performing serial postoperative measurements of blood volume in addition to venous pressure monitoring in these patients.