Platelet function in recipients of platelets from donors ingesting aspirin

Medication Deferrals in Blood Donors

Medication use is extremely common in blood donors. Blood centers use various methods to obtain a history of medication use, all of which have strengths and weaknesses. Some data are available to develop policies for medications that impact product quality, transmissible disease testing, and infectious risks. Many blood centers defer donors for use of a small number of highly teratogenic medications, as a precautionary measure. Others also defer for possible harms related to the pharmacologic effects of medications. However, a single exposure to a blood component containing medication, with immediate dilution in the recipient's blood stream, is a very different situation from ongoing use of medication in a patient, with steady state concentrations achieved over time. It is therefore highly unlikely that these effects are relevant for recipient safety.

Methods for testing platelet function for transfusion medicine

BACKGROUND

Currently only indirect measures are required for monitoring the function of platelets in platelet concentrates (PC).

METHODS

This is an overview on currently available commercialized methods that have been used to determine platelet function in donors, concentrates and after transfusion. We show examples for the application of the no/low shear methods light-transmission aggregometry, flow cytometry, multiple electrode aggregometry, thrombelastography and dynamic light scattering, and those applying high shear, the platelet function analyzer-100, and the cone and plate analyzer. Advantages and disadvantages of the various methods to screen donors, evaluate the haemostatic properties maintained in the PC and after transfusion are discussed, based on considerations of platelet physiology, and the feasibility of the various procedures. This survey focuses on reports from the last 10 years, as the technology for the production of PCs has advanced significantly during the last few years.

CONCLUSION

Specific aspects of platelet function can be assessed by the no/low shear methods, while the high shear methods provide more general analysis of platelet haemostatic competence. Yet, there is no strong evidence that the in vitro data correspond with the clinical outcome.

Huge thrombosis as a consequence of VA-shunts

OBJECTIVE

Thrombosis is a rare but serious consequence of VA-shunts. We present two cases of near fatal thrombosis and its successful (but in case 2, atypical) management.

RESULTS

Case 1: A 38-year-old woman with VA-shunt suffered from rapidly progressing heart failure and later from progressing underdrainage signs nine years after shunting due to a thrombus on the atrial shunt catheter that occluded >80% of the right atrium. Cardio-surgical removal of thrombus and VA-shunt catheter and VP-shunting normalized neurological and cardiological state. Case 2: A 40-year-old woman received a VA-shunt 5 years before she suddenly suffered dyspnea and venous congestion. Secondarily, underdrainage occurred. The underlying huge thrombosis of the superior caval vein could not be excised because the necessary thoracotomy would have interrupted vital venous bypasses along the thoracic wall. Anticoagulants (heparin, cumarin) and ETV relieved all neurological and cardiological symptoms.

CONCLUSION

Sudden or unexpected symptoms of cardiac failure in the presence of a VA-shunt must be recognized as serious. Interestingly, despite distal shunt occlusion, underdrainage symptoms might be initially mild.

Update on pain management for advanced genitourinary cancer

PURPOSE

Pain is a significant problem in many patients with genitourinary malignancy at all stages of disease. Optimal pain control becomes a primary concern as disease progresses and other therapies are exhausted. The selection of the most appropriate therapy becomes difficult without an understanding of the underlying mechanisms of pain and the available therapies.

MATERIALS AND METHODS

A review of the literature regarding the mechanisms and assessment of pain syndromes was performed. All available therapies were investigated with respect to conservative management with opioid medications and adjuvant drugs, and the indications for invasive techniques.

RESULTS

Increased understanding of the mechanisms and classification of pain syndromes has led to improved assessment and treatment. Despite these advances a significant number of patients have inadequate pain control and the education of treating physicians remains an important target for improving this situation.

CONCLUSIONS

Opioid medication is the mainstay of therapy in the majority of patients but with the appropriate addition of other adjuvant drugs patients may achieve optimal pain control without unwanted side effects. A few patients benefit from more invasive techniques, including plexus blocks and neuraxial infusion therapy, and the indications for these treatments are discussed. These therapies have largely superseded neuroablative procedures that are more destructive and associated with higher morbidity.

Promoting symptom control in palliative care

OBJECTIVES

To describe management of common physical problems that occur in patients with advanced cancer.

DATA SOURCES

Research and review articles, book chapters, and published guidelines.

CONCLUSIONS

Effective symptom control for patients with advanced cancer requires the coordinated efforts of a multidisciplinary team. Excellent palliation can be achieved in patients suffering from pain, as well as from gastrointestinal, respiratory, or dermatologic disorders.

IMPLICATIONS FOR NURSING PRACTICE

Nursing is the cornerstone of effective palliative care. Through accurate assessments and expertise in delivering pharmacologic and nonpharmacologic treatments, nurses ensure optimal palliation of physical symptoms.

Anesthesia with antiphospholipid antibodies: anesthetic management of a parturient with lupus anticoagulant and anticardiolipin antibody

The anesthetic management of a parturient with a circulating lupus anticoagulant and an anticardiolipin antibody presenting to the obstetric suite taking heparin and aspirin is discussed. Issues concerning placement of a regional anesthetic with recent aspirin ingestion and heparin therapy are discussed. Documentation of heparin dissipation via a whole blood heparin concentration assay before induction of regional anesthesia, including several laboratory tests that could be used in monitoring coagulation status in this patient population, is discussed in detail.

Nonsteroidal antiinflammatory drugs, perioperative blood loss, and transfusion requirements in elective hip arthroplasty

A study of 160 elective total hip arthroplasties revealed that those patients receiving nonsteroidal antiinflammatory drugs (NSAIDs) in the preoperative period had a significantly increased perioperative blood loss and transfusion requirement when compared with a control group receiving other forms of analgesia for their osteoarthritis. The results suggest that NSAIDs are implicated in increasing the operative blood loss in these patients. The range of increased blood loss varied from 1.57 to 2.08 times the blood loss in the control group, and this effect was seen when the operation was carried out under spinal as well as when under general anesthesia.

Plasma concentrations and anti-platelet effects after low dose acetylsalicylic acid

The present study has investigated whether low-dose acetylsalicylic acid (ASA) can inhibit platelet aggregation locally at its site of gastrointestinal absorption without concentrations in the systemic circulation high enough for inhibition of cyclooxygenase. For this purpose platelet aggregation, thromboxane formation as well as ASA plasma concentrations were measured in 8 volunteers before oral intake of 100 mg ASA as well as 20 to 300 minutes thereafter. At each time 5 ml of blood were mixed with 5 ml of blood obtained from a second, untreated volunteer. Aggregation and thromboxane formation were also determined in these mixed blood samples. The same protocol was performed with 4 volunteers after administration of 1500 mg ASA as well as after no drug intake. In a separate experiment the concentration-effect-relationship of ASA was assessed in vitro. One hundred and forty minutes after administration of 100 mg ASA aggregation and thromboxane formation were significantly decreased to 49.4 and 4.5% of the initial values, respectively, whereas in the mixed blood sample aggregation was not impaired. Inhibition of thromboxane formation was constantly 73% of the inhibition observed in the unmixed sample throughout the study period and thus most probably was caused by dilution of the platelets of the untreated volunteer by the inactivated platelets of the ASA-treated volunteer. These data suggest the absence of pharmacologically active drug concentrations in the peripheral blood. ASA plasma concentration was highest after 40 minutes (2.2 +/- 1.6 microgram/ml; n = 5). After the 1500 mg ASA dose platelet function and thromboxane formation decreased to 29.8 and 2.0% of the initial values, respectively. Furthermore, aggregation and thromboxane formation in the mixed blood sample were markedly reduced. Thus, after the high dose of ASA effective plasma concentrations were present in the peripheral circulation. Highest ASA plasma concentrations were 21.1 +/- 8.9 micrograms/ml. IC50 values were 1.00 +/- 0.36 and 0.30 +/- 0.05 microgram/ml for aggregation and thromboxane formation in vitro, respectively. It is concluded that low dose ASA can effectively inhibit platelet function without producing pharmacologically active concentrations in the peripheral circulation.

A platelet release defect induced by aspirin or penicillin G does not increase gastrointestinal blood loss in thrombocytopenic rabbits

Gastrointestinal blood loss was compared in groups of normal and thrombocytopenic animals treated with medications known to induce qualitative platelet dysfunction. Thrombocytopenia was induced in rabbits by the intraperitoneal injection of busulphan dissolved in polyethylene glycol (PEG) at a dose of 60 mg/kg. Control animals received PEG alone; each group subsequently received daily intravenous injections of penicillin G, aspirin, sodium salicylate or isotonic saline. Mean daily gastrointestinal blood loss was determined by monitoring the appearance of 51Cr radioactivity in the faeces following the administration of 51Cr-labelled erythrocytes prior to the administration of the test and control therapies. The administration of penicillin G was not associated with increased gastrointestinal blood loss in the thrombocytopenic animals as compared with the saline treated thrombocytopenic controls. Platelet aggregation studies confirmed the presence of a mild but significant defect in platelet aggregation. Aspirin produced a more pronounced defect in platelet aggregation but did not induce increased bleeding in the normal animals as compared with the controls, nor did it exacerbate the bleeding in thrombocytopenic animals. Sodium salicylate did not produce an aggregation defect and did not significantly modify gastrointestinal blood loss. It was concluded that drug-induced qualitative platelet dysfunction does not necessarily increase bleeding through intact vessels despite previous evidence of a significant effect on platelet plug formation as monitored by the bleeding time.

Dosage frequency for suppression of platelet function by low dose aspirin therapy

A study of platelet aggregation and MDA production after an oral dose of 300 mg aspirin indicated that partial recovery of platelet function occurred when approximately one third of the circulating platelets had been replaced by new (uninhibited) platelets. In vitro studies on mixtures of normal and aspirin inhibited platelets indicated partial restoration of platelet aggregation and thromboxane B2 production with as little as 10% of normal platelets in some subjects. Restoration of full function required a higher proportion of normal platelets. There was considerable variation between subjects. These data suggest that complete suppression of platelet functions in all normal subjects requires daily administration of the drug.

Rapid return of cyclo-oxygenase active platelets in dogs after a single oral dose of aspirin

A single dose of oral aspirin in human subjects inhibits the aggregation response of platelets to arachidonate and other agents for approximately one week after ingestion. In the present study we have evaluated the rate at which cyclo-oxygenase active platelets return to the circulation in humans and dogs and compared the response curves obtained to improvements in cyclo-oxygenase activity produced by the aspirin platelets. After a single dose of aspirin, dog platelet function was compromised for several days. Normal responses to arachidonate and other aggregating agents were restored six days after aspirin, and the pattern of recovery was the same for dogs and human subjects. However, cyclo-oxygenase active platelets returned to the circulation in dogs more rapidly than in humans and chemical competence was restored in both species well before correction of the defective response to aggregating agents. The delay of 1-3 days before return of significant numbers of cyclo-oxygenase active platelets most likely reflects acetylation of bone marrow megakaryocytes by the drug. More rapid return of chemically competent cells in dogs than humans probably relates to the more rapid turnover and shorter life span of canine platelets. The basis for the discrepancy in return of chemical integrity compared to functional activity after aspirin in vivo compared to simultaneous correction of chemistry and function when 10% normal platelets are added to aspirin platelets in vitro remains unresolved.

Influence of epinephrine on the aggregation response of aspirin-treated platelets

We have evaluated the influence of epinephrine on the sensitivity of aspirin-treated platelets to aggregating agents. Concentrations of ADP, thrombin and arachidonate that caused reversible stimulation of aspirin platelets produced irreversible aggregation when the aspirin samples had been pretreated with epinephrine. The correction was not due to improvement in the ability of aspirin platelets to synthesize prostaglandins or secrete products of the release reaction. Epinephrine induced correction of refractory aspirin platelets may help to explain why aspirin is not a universally effective anti-thrombotic agent.

Chronic myeloproliferative disorders: improved platelet aggregation following venesection

Venesection of 10% of whole blood volume or plateletpheresis was performed in nine patients with chronic myeloproliferative disorders and in five normal control subjects. Before venesection, the patients showed impaired platelet aggregation in 33% of tests, most often in response to stimulation with 9 mumol adrenaline. After venesection, the platelet and megathrombocyte counts increased rapidly and excessively in most patients and platelet aggregation improved markedly. In some cases, spontaneous in vitro aggregation was seen at high platelet concentrations. In two patients impaired platelet aggregation with adrenaline was not corrected. The splenic platelet pool is thought to be the probable source of the new platelets.

Recording of drug prescriptions in the county of Jämtland, Sweden. III. Drugs presented for blood donors in a 5 year period

Drug prescriptions in the county of Jämtland, Sweden, have been examined in order to estimate drug exposure of blood donors. During the period 1970-74 a donor group (n = 292) purchased significantly more drugs than non-donors matched for age, sex and residential area in the county. This was true for most drug categories, except for cardiovascular and endocrine drugs and iron preparations. The actual consumption of the drugs obtained was not investigated. Prospective studies are required to assess the clinical consequences of the surprisingly high drug exposure of blood donors.

Gingival hemorrhage related to aspirin ingestion. A case report

A case report illustrating the clinical manifestations of platelet defects induced by ingestion of two aspirin tablets has been presented. The specific effects on platelets produced by aspirin ingestion have been summarized and the resultant hemostatic defect explained.

Inhibition of platelet aggregation caused by estrogen treatment in patients with carcinoma of the prostate

Platelet aggregation is increased in patients with carcinoma of the prostate treated with estrogens. Hence, these patients have a high incidence of cardiovascular and thromboembolic diseases. Platelet aggregation has been tested with the platelet aggregation test. It was inhibited by administration of 500 mg. acetylsalicylic acid twice daily. An aggregation inhibiting effect has been found in all 38 patients. To reduce the excess hazards of cardiovascular complications of estrogens in treating carcinoma of the prostate acetylsalicylic acid is recommended as an adjunct therapy.

Reduction of platelet/fibrin deposition in haemodialysers by aspirin administration

Aspirin, a drug known to inhibit the platelet release reaction, was evaluated for its potential in reducing platelet/fibrin deposition in hollow fibre dialysers. Twelve patients with endstage renal failure were given the drug under controlled conditions while being treated by regular maintenance haemodialysis. After base-line data were collected during a mean number of 11.7 dialysers per study, observations were repeated for a mean of 9.3 dialysers, during which time each patient took 600 mg of aspirin by mouth every morning. Thrombus deposition, measured by volume loss of the blood compartment of the dialyser fibre bundle, was significantly reduced (P less than 0.05) during aspirin administration in six of the 12 studies. The mean volume loss of the fibre bundle in these six studies (responders) was 25% per dialysis during the control period, and 13% with aspirin; in the other six studies (non-responders), the mean values were 8% and 6% respectively. Aspirin prolonged the bleeding time in all patients, and significantly (p less than 0.05) impaired platelet aggregation in both responders and non-responders.