Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Cardiovascular Anesthesia
INTRODUCTION: There is need for a rapid on-site assay of hemostasis when there is history of nonsteroidal antiinflammatory (NSAID) use. The Hemochron-Saline (H-S) whole blood coagulation assay has been noted to have high sensitivity and specificity for detection of low levels of heparin in patients stabilized prior to cardiac surgery.  We tested the response of this assay to acetylsalicylic acid (ASA) and ibuprofen (IBU) that was added in-vitro. The H-S assay is automated, but contains no activators or buffers, as such, it appears to be sensitive to subtle changes in hemostasis. Lee-White clotting times (LWCT) were also evaluated for NSAID effects.
METHODS: With IRB approval, 20 ml of blood was drawn from 13 cardiac surgery patients, pre-induction, into sodium citrate tubes. Blood was incubated (37[degree sign]C) for 60 min with either ASA(13-390 [micro sign]g/ml) or IBU(5-50 [micro sign]g/ml); antiinflammatory blood levels of ASA are 195-390 [micro sign]g/ml and IBU is antipyretic at 10 [micro sign]g/ml.  (Controls showed stable clotting times after incubation at 37[degree sign]C for 2-60 min). Assay tubes were reconstituted with 6.8-7.5 [micro sign]moles CaCl2/ml blood, 2.0ml for H-S and 1.0ml for LWCT. LWCT tubes (13mm x 75mm), incubated at 37[degree sign]C, were inverted every 30 sec until the clot adhered, even with tube inversion.
RESULTS: ASA and IBU did not affect clotting time in the H-S assay (Table 1). ASA also had no apparent effect on LWCT, although experimental error was high in LWCT assays, ASA at 13, 52, 210 and 390 [micro sign]g/ml showed average clotting times that were 87%, 120%, 96% and 98% of controls, respectively. In a single experiment, ASA additions were made directly to H-S tubes in the operating room before addition of fresh, uncitrated blood, 66, 130 and 390 [micro sign]g/ml of ASA had clotting times that were 94%, 101% and 102% of control, respectively.
DISCUSSION: ASA and IBU, added in-vitro to blood at therapeutic levels, did not influence clotting times. Expected effects of these NSAID's on platelet function may not have been detectable by the tests employed; or, the drugs did not influence platelet function under the test conditions.
1. Anesth Analg 84: SCA 39, 1997.
2. Goodman and Gilman's, The Pharmacological Basis of Therapeutics, 9th Ed., 1996, pp. 1749, 1780.