PROLONGATION AND NORMALIZATION OF SUBAQUEOUS BLEEDING-TIME UNDER THERAPY WITH DIFFERENT DOSAGES OF ACETYLSALICYLIC-ACID

The present study investigated whether there is a statistically signif icant correlation between platelet aggregation inhibition (TAI) and pr olongation of subaqueous bleeding time (SBT) under therapy with 40 mg (n = 20) and 500 mg (n = 20) acetylsalicylic acid (ASA) daily and when parameters return to normal after discontinuation of long-term (4 wee ks) and short-term (I week) treatment. The results of this study may b e helpful in clinical practice when deciding upon indications for cert ain operative or anaesthetic procedures. Results. Under ASA treatment, neither TAI nor prolongation of SBT was dependent on dosage or time ( Figs. 1-4). After discontinuation of ASA, platelet aggregation returne d to normal 1-4 days later than SBT, depending on the dosage and durat ion of medication. SBT declined to its initial value on the 3rd day fo llowing discontinuation of ASA in both dosage groups (Figs. 2 and 4). Normalisation of platelet aggregation depended on dosage: in those gro ups with 40 mg ASA, thrombocyte aggregation had normalised on the 4th day irrespective of duration of medication; in groups with 500 mg aggr egation capacity was completely restored on the 5th day after 1-week t herapy and on the 7th day after 4-week therapy (Figs. 1 and 3). Consid ering these results, an important factor is the time of discontinuatio n of ASA intake. Prior to scheduled operative procedures or regional a naesthetics near the spinal cord, ASA should be discontinued, dependin g on the dosage, 2-3 days ahead. At this time SBT has reached the init ial value, however, the aggregation capacity of thrombocytes is still reduced for a few days. For reasons of safety, in patients on ASA the SBT should be determined prior to regional anaesthesia. If it is below 5 min there are no contraindications, as experience has shown. If val ues exceed 5 min, certain regional anaesthetic procedures (e.g., epidu ral anaesthesia) should not be performed. In these cases spinal anaest hesia might be an acceptable alternative because of the thinner needle used and therefore reduced risk of bleeding.