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Abnormal red blood cells may be responsible for the abnormal blood clotting seen in pregnant women with preeclampsia. Researchers measured the time it took blood to clot in blood samples from 25 non-pregnant women, 25 healthy pregnant women, and 10 pregnant women with preeclampsia. The blood from women with preeclampsia clotted more quickly than blood from the other two groups. However, when red blood cells were removed from the samples, all three groups of samples clotted in approximately the same amount of time.

* Background. -- Office-based anticoagulation monitors offer significant advantages in convenience, yet their performance has been inadequately characterized. Methods. -- We characterized the performance of a portable anticoagulation monitoring system with respect to precision and agreement with a reference laboratory. Eighty-five patients from a university outpatient anticoagulation clinic provided 143 whole blood sample pairs for evaluating agreement between the monitor and the laboratory. Fifty-four patients each provided a second pair of samples for assessing the monitor's precision, and 23 pairs of measurements from the reference laboratory were used for assessing the laboratory's precision. Anticoagulation was measured using International Normalized Ratio (INR) values. Agreement between monitor and laboratory was evaluated as the difference between paired measurements. Precision was calculated as the within-patient standard deviation based on paired values. Results. -- Within the range of 2.0 to 3.0 INR units, the monitor yielded values that were up to 0.3 units higher on average than the laboratory values. Within the range of greater than 3.0 to 4.5 INR units, the monitor yielded values that were up to 0.5 units lower on average than the laboratory values. Seventy-five percent of paired monitor and laboratory values were within 0.7 INR units; 90% were within 0.9 units. Within-patient standard deviation was 0.23 units for the monitor and 0.19 units for the laboratory. Conclusions. -- The monitor differed systematically from the laboratory and was moderately less precise. The magnitude of these effects was not great, however, and accuracy was best at around INR = 3.0, the border between low and high therapeutic ranges. The clinic-based monitor is useful for patients requiring frequent surveillance of anticoagulation status. (Arch Intern Med. 1992;152:589-592)

Percutaneous transluminal coronary angioplasty (PTCA) is a technique for repairing coronary blood vessels that are clogged and narrowed. It involves inserting a catheter tipped with a deflated balloon into the vessel and inflating the balloon at the diseased site. One potential problem with this procedure, as with most procedures treating blood vessels and the heart, is the development of blood clots. Heparin is a drug that helps prevent blood from clotting. It is commonly given to patients undergoing PTCA to prevent unwanted clotting both during and after the procedure. A problem with heparin is that it has highly variable effects. By measuring the time it took for blood to clot during angioplasty, this study attempted to develop a regimen with heparin that would allow consistent anticoagulation during the operation. It also examined the use of heparin in preventing side effects following PTCA. Forty patients undergoing PTCA were randomly assigned to one of two treatment groups, one receiving a single, large injection (bolus) of heparin at the beginning of the procedure, and the other receiving a bolus plus a constant infusion of heparin. Following completion of PTCA, a continuous infusion was given to both groups for 24 hours. Activated clotting time, a test measuring the blood's speed in clotting, was observed at various times to determine the effectiveness of the heparin administration. Results showed that during PTCA, 11 (55 percent) of the patients receiving only the bolus and 3 (15 percent) receiving both the bolus and the constant infusion required additional heparin injections. Activated clotting time was greater for arterial blood than venous blood in 70 percent of the patients for the first 30 minutes. These results show that patients undergoing PTCA should be given a bolus and a constant infusion of heparin rather than a single bolus alone. Monitoring of the effectiveness of the heparin is best done by measuring the activated clotting time of arterial blood. (Consumer Summary produced by Reliance Medical Information, Inc.)

Raytel Cardiac Services now offers patients a self-testing program for monitoring international normalized ratio (INR) levels. The INR@Home self-testing service allows patients to measure their INR level with a lightweight, [...]

The Harmony monitoring system allows patients to monitor their blood dotting time (international normalized ratio) at home. The system was designed for people who take warfarin to prevent blood dots [...]