Aspirin and bleeding-time

Blood loss in long-term aspirin users undergoing transurethral prostatectomy

As aspirin is now widely used for preventing recurrence of cardiovascular and cerebrovascular disorders, many men selected for transurethral resection of the prostate (TURP) are aspirin users. The previous indication for aspirin as a preoperatively administered antithrombotic agent is no longer common. In this study we investigated the blood loss in long-term aspirin users (250 mg/day) undergoing TURP. The mean blood loss in the 40 aspirin users was 358 (range 50-1550) ml, and in a control group of 42 men it was 478 (40-2400) ml. When mean blood loss was correlated to operating time and prostatic weight, the intergroup difference was not significant. In the late postoperative period two aspirin-treated men had bleeding with tamponade of the urinary bladder requiring emptying in the operating room. As blood loss was not enhanced by aspirin use, avoidance of aspirin before TURP appears to be unnecessary.

Aspirin, a silent risk factor in urology

Aspirin is a widely used drug for its analgetic, antiinflamatory and antipyretic effects as well as for prophylactic effect in cardiovascular diseases. However, an increased number of operative hemorrhagic complications in patients on daily aspirin have been reported, an adverse effect highly relevant in urology. In this review the normal hemostatic mechanism and the chief pharmacological effect of aspirin on hemostasis is described. The literature is reviewed for hemorrhagic complications to aspirin in urology. Few reports indicate that aspirin increases bleeding and need for transfusion following prostatectomy, but no placebo-controlled clinical trials with large patient groups have been carried out. Following prostate biopsy and extracorporeal shock wave lithotripsy aspirin-induced hemorrhagic complications have been reported. Cessation of aspirin ingestion one week prior to invasive urologic procedures and correction of bleeding complications with desmopressin, platelet concentration or fresh whole blood is described.

Effects of nonsteroidal antiinflammatory drugs on platelet function and systemic hemostasis

Aspirin and nonaspirin nonsteroidal antiinflammatory drugs (NSAIDs) inhibit platelet cyclooxygenase, thereby blocking the formation of thromboxane A2. These drugs produce a systemic bleeding tendency by impairing thromboxane-dependent platelet aggregation and consequently prolonging the bleeding time. Aspirin exerts these effects by irreversibly blocking cyclooxygenase and, therefore, its actions persist for the circulating lifetime of the platelet. Nonaspirin NSAIDs inhibit cyclooxygenase reversibly and, therefore, the duration of their action depends on specific drug dose, serum level, and half-life. The clinical risks of bleeding with aspirin or nonaspirin NSAIDs are enhanced by the concomitant use of alcohol or anticoagulants and by associated conditions, including advanced age, liver disease, and other coexisting coagulopathies.

Low-dose preoperative aspirin therapy, postoperative blood loss, and transfusion requirements

The effects of three low-dose regimens of preoperative aspirin therapy on postoperative blood loss, transfusion requirements, and length of hospital stay were recorded in a prospective cohort study of 202 patients undergoing elective coronary artery bypass grafting. One hundred one patients had been prescribed daily aspirin by the referring cardiologist (44 at 75 mg, 28 at 150 mg, and 29 at 300 mg); the remaining 101 patients who had not been prescribed aspirin acted as a control group. A median postoperative blood loss of 870 mL in the control group was increased by 280 mL in the 75-mg aspirin group (p less than 0.001), by 490 mL in the 150-mg aspirin group (p less than 0.001), and by 230 mL in the 300-mg aspirin group (p = 0.03). The median requirement for blood transfusion of 2 U red blood cell concentrates in the control group was increased by 2 U in the 75-mg aspirin group (p less than 0.001), 2 U in the 150-mg aspirin group (p less than 0.001), and 1 U in the 300-mg aspirin group (p = 0.05). Hemostatic "packs" (fresh frozen plasma, platelets, and cryoprecipitate) were required in 20 patients in the aspirin groups as compared with 5 in the control group (p less than 0.01 by chi 2 test). The mean postoperative hospital stay was 8 days for all groups. Regular daily low-dose aspirin therapy produces significant increases in postoperative blood loss, resulting in a substantial increase in blood transfusion and hemostatic pack requirements, but does not prolong postoperative hospital stay.

A study of bleeding time in 120 long-term aspirin trial patients

The bleeding time was measured in 120 patients participating in a longterm randomised double-blind trial of aspirin in thromboembolic prophylaxis (UK-TIA aspirin Study). In 70 patients taking aspirin 300 mg or 1,200 mg daily for a mean duration of 35 months the bleeding time averaged 228 seconds. In comparison with 30 patients randomised to placebo and not taking aspirin whose bleeding time averaged 217 seconds, there was no significant difference. Stratification of bleeding time estimation by duration of treatment suggested no significant trend in either placebo or aspirin groups over several years. These results suggest that the longterm trials of aspirin should be looked at again from the point of view of efficacy of treatment by time from randomisation.

Effect of incremental doses of aspirin on bleeding time, platelet aggregation and thromboxane production in patients with cerebrovascular disease

Bleeding time, thromboxane production and inhibition of platelet aggregation were studied before and during administration of acetylsalicylic acid in doses of 50, 100, 325 an 1000 mg daily in eighteen patients with cerebrovascular disease. Inhibition of thromboxane production and platelet aggregation was almost complete at 50 mg acetylsalicylic acid daily, and median bleeding time had increased significantly from 5.5 to 6.5 min at this dose and reached a maximum of 7.5 min at 100 mg daily. Further increase of the dose resulted in a slight decrease in bleeding time. It appears that a strong effect on platelet function can be achieved by small doses of acetylsalicylic acid, and that higher doses might be less effective.

[Importance of prostaglandins for the in vitro adhesiveness and in vivo margination of neutrophilic granulocytes]

The (patho-)physiological role of prostaglandins and thromboxanes on granulocyte function remains controversial. In a combined in vitro and in vivo study, we analyzed the influence of these arachidonic acid metabolites on granulocyte adhesion and margination. A dichotomous dose-dependent effect on epinephrine-induced granulocyte demargination parallels the paradoxical effect of low (0.5 g)- and high (4 g)-dose aspirin on bleeding time. These observations suggest that prostacyclin acts as a modulator for low-affinity adhesion and margination of granulocytes. With respect to the induction of high-affinity adhesion, which is reflected in a state of hypermargination in vivo and accompanied by potentially cytotoxic cell activation, prostaglandins in general and prostacyclin in particular are without effect when such activation is induced, either by endotoxin, by formylated chemotactic peptide, or by activated complement.

Platelets, carotids, and coronaries. Critique on antithrombotic role of antiplatelet agents, exercise, and certain diets

"Antiplatelet" drugs and certain life styles seem to have an "antithrombotic" effect that may help protect against stroke and heart attack. This review of the experience with aspirin, dipyridamole, and sulfinpyrazone offers new interpretations of some of the major clinical trials, suggests guidelines for use of antiplatelet drugs, and integrates novel observations on diet and exercise into the "thromboxane-prostacyclin balance" hypothesis. It is argued that the Canadian stroke study showed that aspirin protects men with transient ischemic attacks from coronary death as well as from stroke, that type II errors may have been made in some clinical trials, that aspirin protects women as well as men, that aspirin benefits patients who have had a heart attack, that the effect of aspirin in angina varies with the type of angina, that the dose of aspirin used may not be critical, that guidelines for use of dipyridamole and sulfinpyrazone are still inconclusive, and that exercise and fish oil supplements may be "antithrombotic."

Usefulness of the measurement of plasma beta-thromboglobulin (beta-TG) in cerebrovascular disease

The plasma concentration of the platelet-specific protein beta-thromboglobulin (beta-TG) was measured in 39 normal subjects and 568 patients of neurological diseases. The beta-TG RIA commercially available KIT was also evaluated. Abnormally high plasma levels of beta-TG were demonstrated in groups of ischemic or obstructive cerebrovascular diseases as compared with that of normal subjects. The highest concentrations were found in 8 patients with Moya-Moya disease, (mean concentration of beta-TG was 204.4 ng/ml), completed stroke at an acute stage was next (mean beta-TG level was 194.8 +/- 70.8 ng/ml). On the other hand, many hemorrhagic cerebro-vascular diseases or other neurological diseases such as brain tumors, hydrocephalus, etc. do not show elevated beta-TG levels. In many patients with ischemic or obstructive cerebro-vascular diseases treated with anti-platelet drugs such as Aspirin, Dipyridamole, Bencyclane or Ticlopidine, a significant fall in plasma concentration of beta-TG was chronologically demonstrated. The measurement of plasma beta-TG concentration may be useful not only in the diagnosis of ischemic or obstructive cerebro-vascular disorders but also in judging the efficacy of anti-platelet therapies and prognosis.

Effects of acetylsalicylic acid and dietary intervention on primary hemostasis

There is evidence that pathological aggregation of platelets in atherosclerotic arteries is initiated by hemorrhage through fissures in atheromatous plaques. Bleeding time determination reflects in vivo the physiologic function of platelets in their aggregation in injured vessels and can be used as a relevant model for primary hemostasis in investigations with antithrombotic aims. Acetylsalicylic acid is known to cause prolongation of bleeding time by inhibiting prostaglandin biosynthesis. Recent experiments have shown that dietary supplementation with omega-3 polyunsaturated fatty acids results in prolongation of bleeding time and decreased platelet aggregability. This paper is mainly concerned with the effect of different doses of aspirin (3.5 mg/kg, 5 mg/kg, and 10 mg/kg), and fish diets rich in omega-3 polyunsaturated fatty acids, on bleeding time and platelet aggregation. The effects of aspirin separately, as well as aspirin administration during dietary intervention, will be described. Administration of all three dose levels of aspirin prolonged bleeding time significantly (p less than 0.001). The effect of aspirin on bleeding time was dose-dependent and an optimum interval was found. A fish diet, rich in omega-3 polyunsaturated fatty acids, causes bleeding time prolongation and decreased platelet aggregability similar to those caused by aspirin. Aspirin taken during this diet prolonged bleeding time by more than the sum of the increases in bleeding time caused by aspirin and the diet with omega-3 polyunsaturated fatty acids, separately, but the synergism was not significantly more than additive. These observations suggest that fish diets affect primary hemostasis by mechanisms different from those of aspirin. Dietary intervention may therefore enhance the antithrombotic effects of aspirin.

Inhibition of prostacyclin and platelet thromboxane A2 after low-dose aspirin

To compare the inhibitory effects of aspirin on prostaglandin synthesized by vessel walls and platelets, we obtained vein segments from five subjects before they were given 150 or 300 mg of aspirin and at various intervals afterward. We then measured prostacyclin (PGI2) synthesis with a radioimmunoassay for its stable metabolite, 6-keto-prostaglandin F1 alpha. Platelet production of thromboxane A2 was measured with a radioimmunoassay for its stable metabolite, thromboxane B2. Two hours after aspirin had been given, 81 to 100 per cent inhibition of PGI2 synthesis was demonstrated; 86 per cent inhibition was still evident in one subject tested eight hours after administration. Simultaneously, platelet production of thromboxane B2 was completely inhibited for more than 24 hours. We conclude that there is little difference between the initial inhibitory response of platelet cyclooxygenase and that of vessel-wall cyclooxygenase to these doses of aspirin. Our results also indicate that in male subjects the prolonged template bleeding time after aspirin is not the consequence of selective inhibition of platelet production of thromboxane.

Acetylsalicylic acid-induced prolongation of bleeding time in healthy men

Bleeding times were determined in 25 healthy men using the Thrombolette bleeding time device. The median bleeding times prior to low and high doses of acetylsalicylic acid (ASA), 245 and 230 s, were not significantly different (P = 0.12). 2 h after randomized ingestion of 0.44 and 3.96 g ASA, the median bleeding times rose to 450 and 430 s, respectively. Both increased in bleeding time were significant (P less than 0.001), but the difference was not significant (P = 0.29). The maximum increase in bleeding time was estimated to occur 2.6 h after ingestion of a single low ASA dose, and 2.4 h after a single high dose. Following ingestion of 0.44 as well as 3.96 g ASA the bleeding time returned to basal levels within 5-6 d. Compared to the younger ones, volunteers with a higher age showed a tendency to have lower plasma salicylate levels as well as smaller increases in bleeding times following ASA ingestion.

Congenital deficiency of thromboxane and prostacyclin

Animal work suggests that with certain doses of aspirin the antithrombotic effect exerted via the inhibition of the proaggregatory platelet thromboxane A2 (TXA2) may be neutralised by the concomitant vascular reduction of the antiaggregatory prostacyclin (PGI2). Such a situation might result not only in therapeutic ineffectiveness but also in a thrombotic tendency. A patient with a bleeding disorder characterised by a mildly prolonged bleeding time and defective platelet-release reaction due to a congenital deficiency of cyclo-oxygenase provided an opportunity for studying this problem. Her platelets did not aggregate with arachidonic acid, but they did so with a synthetic endoperoxide analogue. Thrombin added to her platelet-rich plasma and whole blood did not generate thromboxane B2 (TXB2). Washed platelets, when incubated with 14C-arachidonic acid, did not produce the cyclo-oxygenase metabolites. A biopsy specimen of her vein did not generate PGI2, as measured both by platelet-aggregation inhibition and radioimmunoassay of 6-keto-PGF1 alpha. Clinically, the patient had a mild bleeding tendency but no thrombotic problems. The findings suggest that in man aspirin therapy, even at doses which inhibit PGI2 formation, would only impair haemostasis mildly without producing a thrombotic tendency.

Anticoagulant vs anti-platelet therapy as prophylactic against cerebral infarction in transient ischemic attacks

156 patients with transient ischemic attacks (TIA) or reversible ischemic neurological deficit (RIND) were given prophylactic anticoagulant (AC) treatment against cerebral infarction in a prospective multicenter study from 5 hospitals in southern Sweden. After 2 months of AC treatment, 135 patients remained in the study and were randomized into 2 groups; one continued with AC treatment and one changed to anti-platelet therapy. The patients were followed for 12 months. No significant difference was seen between the 2 groups but 3 completed cerebral infarctions occurred during anti-platelet therapy against one during AC treatment. One cerebral hemorrhage was seen during AC treatment. All completed strokes occurred in men who initially had carotid symptoms. The number of patients with TIA/RIND was somewhat higher in the anti-platelet group whereas myocardial infarctions occurred more often during AC treatment. Compared to the natural history of untreated TIA/RIND both treatments were found to have a prophylactic effect against cerebral infarction.