Haemostatic, lipid, and blood-pressure profiles of women on oral contraceptives containing 50 microgram or 30 microgram oestrogen

In 15 women on oral contraceptives containing 30 microgram oestrogen, mean values for factors II, VII, and X, fibrinogen, fibrinolytic activity, antithrombin III, cholesterol, and fasting triglycerides were intermediate between values for 63 women on preparations containing 50 microgram oestrogen and those for 243 premenopausal women not on oral contraceptives. Mean blood-pressure levels, however, were higher in women on 30 microgram than in those on 50 microgram preparations. In 28 women on 50 microgram preparations containing 3 mg or 4 mg norethisterone, mean values of factor VII, fibrinogen, fibrinolytic activity, cholesterol, fasting triglycerides, and systolic blood-pressure were higher than in 15 women whose preparations contained only 1 mg of norethisterone. A less consistent picture was found in women on 30 microgram oestrogen preparations containing either 250 microgram (10 women) or 150 microgram (5 women) d-norgestrel. It is concluded that 30 microgram oestrogen preparations probably result in smaller hemostatic and lipid changes than 50 microgram preparations but that they may have a blood-pressure-raising effect attributable to the particular progestagen, d-norgestrel, used in 30 microgram preparations. The safety of these 30 microgram oestrogen preparations may thus depend partly on the balance between these two sets of effects. It is also concluded that norethisterone may have effects similar to those attributed to oestrogens.

Changes in haemostatic system after application of a tourniquet

In 35 patients undergoing routine orthopaedic operations in which occlusive tourniquets were used there was a pronounced rise in fibrinolytic activity in the systemic circulation which lasted for at least 15 minutes after the release of the tourniquet; this response was seen after operations on both arms and legs. In contrast there was no increase in fibrinolytic activity in the systemic circulation associated with venous occlusion. Neither the application of a tourniquet nor venous occlusion resulted in changes in factors V or VIII, fibrinogen, or platelet-count. The application of a completely occlusive tourniquet might be a simple form of prophylaxis against deep-vein thrombosis and would avoid the disadvantages of using heparin.

Factor V in an industrial population

Factor-V levels have been measured in a random sample of 626 men and 307 women working in a variety of occupations in North West London. The method is an automated one-stage assay using the same batch of freeze-dried thromboplastin, all results being expressed in terms of the same freeze-dried standard plasma; it has been shown that only one dilution of test plasma is necessary. Factor-V levels are significantly higher when venepuncture is difficult than when it is satisfactory, the mean levels being about 130% and 117% respectively. Factor-V levels are approximately normally distributed; they are similar in men and women and in blacks and whites, and increase significantly with age at the rate of about 0.6% per annum. Factor-V levels are not affected by oral contraceptives or the menopause, and there are no differences according to blood group or secretor status.

Reaction pattern to three stresses--electroplexy, surgery, and myocardial infarction--of fibrinolysis and plasma fibrinogen

The effects of three types of stress-electroplexy, surgery, and myocardial infarction-on blood fibrinolytic activity and plasma fibrinogen levels were studied in 10, eight, and six patients respectively. The fibrinolytic response to electroplexy consisted of an initial short increase followed in half the patients by reduced fibrinolytic activity lasting two to four days. After surgery and myocardial infarction normal fibrinolytic activity was followed by a period of reduced activity; the timing of the measurements on these patients may have precluded recognition of an initial increase in fibrinolysis similar to that following electroplexy. The fibrinolytic ;shutdown' which lasted for about 10 days in the coronary patients was evidently due to reduction of plasminogen activator, as judged by prolongation of the euglobulin lysis times as well as of the blood clot lysis times. Plasma fibrinogen levels rose in the surgical and coronary patients but not in the patients given electroplexy which indicates that fibrinolytic activity changes independently of plasma fibrinogen level. The results suggest that the fibrinolytic system exhibits a common reaction pattern to stress, irrespective of its nature and of tissue damage. They call for caution in assuming a specific causal association in acute diseases such as pancreatitis and haematemesis where similar fibrinolytic changes may be encountered.

Methodological study and a recommended technique for determining the euglobulin lysis time

The euglobulin lysis time, which is widely used to measure blood fibrinolytic activity, is shown to be sensitive to the temperature and pH at which the euglobulin fraction of plasma is prepared and also to the type of anticoagulant employed and buffer in which it is suspended. A standardized method for performing the test, which controls these variables and has been found to yield reproducible results, is described. Since, at present, data obtained with this test by different laboratories are, for the reasons given, rarely comparable, it is hoped that the method outlined may be considered suitable for general adoption.