ABSTRACT
A number of commercial rabbit tissue thromboplastins used in oral anticoagulant control have been calibrated against the first International Reference Preparation for thromboplastins. This was done in a three-stage procedure by one laboratory, each stage representing a different level of thromboplastin comparability. The calibration model recently recommended by ICTH and ICSH was tested. This model proved to be suitable, although a statistically significant aberration was observed for some of the thromboplastins. The bias introduced by using the model in these non-ideal cases was small compared to the overall variation of the International Normalized Ratio, being the universal scale for reporting the prothrombin time during oral anticoagulant control. Batch-to-batch calibration using lyophilized pooled plasmas could be reliably performed for several commercial thromboplastins.
Subject(s)
Anticoagulants/standards , Thromboplastin/standards , Administration, Oral , Animals , Anticoagulants/administration & dosage , Blood Coagulation/drug effects , Humans , International System of Units/standards , Prothrombin Time , Rabbits , Reference Standards , Statistics as Topic , Thromboplastin/administration & dosageABSTRACT
Factors contributing to the blood pressure (BP) response to changes in dietary sodium intake were studied in 25 patients with essential hypertension (EH). Relevant clinical, biochemical and haemodynamic variables were measured after two weeks on a low sodium diet (LS, 50 mmol) and after two weeks on a high sodium diet (HS, 300 mmol). BP was significantly higher during HS. The difference in mean arterial pressure between HS and LS (delta MAP) was taken as a measure of sodium sensitivity. delta MAP was directly related to age, initial BP, plasma noradrenaline during HS and changes in forearm vascular resistance. It was indirectly related to plasma aldosterone during LS. No correlation was found with renin or with the excretion of urinary kallikrein. It is concluded that sodium sensitivity in EH is related to age and blood pressure and is predominantly mediated by changes in vascular resistance to which aldosterone and adrenergic mechanisms are likely to contribute.
