Thrombocytopenia. Issues in diagnosis and therapy

Pseudothrombocytopenia: A Rare Phenomenon

Thrombocytopenia is a serious situation that causes anxiety in doctors and patients due to its relationship with serious hemorrhagic manifestations. Pseudothrombocytopenia, however, is a situation without clinical interest because it is an in vitro decrease in platelet count. Pseudothrombocytopenia is related to the ethylenediaminetetraacetate (EDTA)-dependent exposure of antigenic determinants of platelet membrane gly coproteins gpIIb-IIIa and the subsequent reaction of common antibodies with these receptors. To our knowledge, a similar situation in Greece has not been reported. The main character istic of pseudothrombocytopenia due to EDTA is that the fall in platelet count is time-dependent and it disappears after the use of anticoagulant other than EDTA (e.g., citrate sodium or hep arin). We present seven cases of pseudothrombocytopenia re vealed when we used automatic hematologic analyzers and EDTA as an anticoagulant. After the use of another anticoagu lant (e.g., citrate sodium) the platelet count in the same hema tologic analyzer was normal.

Drug-induced thrombocytopenia

Drug-induced thrombocytopenia (DIT) is a relatively common clinical disorder. It is imperative to provide rapid identification and removal of the offending agent before clinically significant bleeding or, in the case of heparin, thrombosis occurs. DIT can be distinguished from idiopathic thrombocytopenic purpura, a bleeding disorder caused by thrombocytopenia not associated with a systemic disease, based on the history of drug ingestion or injection and laboratory findings. DIT disorders can be a consequence of decreased platelet production (bone marrow suppression) or accelerated platelet destruction (especially immune-mediated destruction).

Drug-induced thrombocytopenia in the coronary care unit

Drug-induced thrombocytopenia is a phenomenon that causes significant morbidity and mortality among patients. Practitioners should be able to recognize the clinical manifestations of drug-induced thrombocytopenia, differentiate it from other causes, and manage it appropriately. Numerous case reports have documented drug-induced causes of thrombocytopenia. The following article focuses on the characteristics and management of drug-induced thrombocytopenia secondary to medications commonly encountered in the coronary care unit. Pharmacotherapeutic agents that are most commonly implicated in this setting include ticlopidine, unfractioned heparin, glycoprotein (GP)IIb/IIIa inhibitors, H(2)-receptor antagonists, quinidine and antibiotics. Case reports were obtained through a comprehensive search of the Medicine database and subsequently complemented by bibliographic reviews of the agents just specified. Reports that exhibited possible, probable, and definite associations with drug-induced thrombocytopenia are included in the article.

Evaluation and management of drug-induced thrombocytopenia in the acutely ill patient

The numerous drugs to which the acutely ill are exposed place these patients at a significant risk of developing drug-induced thrombocytopenia. Such patients tend to have preexisting hemostatic defects that place them at additional risk of complications as a result of the drug-induced thrombocytopenia. The clinical challenge is to provide rapid identification and removal of the offending agent before clinically significant bleeding or, in the case of heparin, thrombosis results. Drug-induced thrombocytopenic disorders can be classified into three mechanisms: bone marrow suppression, immune-mediated destruction, and platelet aggregation. Clinical characteristics, preliminary laboratory findings, and drug history specific to the mechanisms can assist clinicians in rapidly isolating the causative drug.

Disseminated intravascular coagulation

OBJECTIVES

To provide an overview of the pathophysiology, manifestations, diagnosis, and treatment of disseminated intravascular coagulation (DIC) as it occurs in cancer.

DATA SOURCES

Published articles, research reports, and book chapters.

CONCLUSIONS

The syndrome of DIC is a serious hypercoagulation state that in its acute form may be life-threatening. The hemorrhage and intravascular coagulation that occur with DIC may lead to irreversible morbidity and mortality. Prompt recognition and emergency treatment are necessary to help minimize morbidity and mortality.

IMPLICATIONS FOR NURSING PRACTICE

Nurses can play an important role in early recognition of DIC to allow for prompt intervention. Nurses caring for patients affected by DIC will be providing complex nursing care, in addition to psychosocial support to patients and families.

Heparin-induced thrombocytopenia

OBJECTIVE

To highlight the importance of heparin-induced thrombocytopenia (HIT), a potentially fatal adverse effect of heparin therapy.

CASE SUMMARY

There are two types of HIT with distinct etiology. Type 1 HIT is a relatively mild thrombocytopenia of early onset that generally resolves with ongoing heparin therapy. Clinical complications are uncommon. Type 2 HIT, which is more severe, is the main focus of this report. Five patients receiving heparin therapy developed type 2 HIT, which in some cases resulted in complications that required limb amputation, or eventuated in death.

DISCUSSION

In a patient receiving heparin therapy, the development of thrombocytopenia should alert the caregiver to the possible development of HIT. Prompt management of HIT can help prevent complications. HIT usually manifests 5-8 days after starting heparin therapy. The platelet count usually decreases to less than 100 x 10(3)/mm3. It generally normalizes within 5-7 days after discontinuing heparin therapy. In spite of the thrombocytopenia, thrombosis or disseminated intravascular coagulation can occur. The management may be subdivided into three clinical situations: mild-to-moderate asymptomatic thrombocytopenia, severe thrombocytopenia with a platelet count of less than 50 x 10(3)/mm3, and thrombosis or embolism complicating HIT.

CONCLUSIONS

Heparin-induced thrombocytopenia is an uncommon but potentially serious, and sometimes lethal, complication of heparin therapy. Therefore, it is important to be aware of the possibility of the development of HIT with heparin therapy, to recognize it early, and to manage it appropriately before the manifestation of adverse effects.

Platelet-associated bleeding disorders

OBJECTIVE

To provide a review of platelet disorders, treatment, and nursing care.

DATA SOURCES

Review articles and book chapters pertaining to quantitative and qualitative platelet disorders.

CONCLUSIONS

Platelet-associated bleeding disorders are classified as quantitative (abnormal number), qualitative (abnormal function), or hypercoagulable states (errors in hemostasis). The resulting complications include thrombocytosis, thrombocytopenia, hypercoagulation, or bleeding dyscrasias. The administration of drugs, plasma, or platelet therapy may be beneficial to these patients.

IMPLICATIONS FOR NURSING PRACTICE

Patients with platelet disorders are at great risk of life-threatening hemorrhage and require close monitoring to prevent unnecessary sequelae. Patient instruction to prevent trauma is required.

The effect of age on hemopoiesis

Although several workers have described numerous changes affecting the hemopoietic system during senescence, the existence of univocal "hematological disease" closely related to the elderly is controversial. Many of the hematological changes described, such as sideropenic or megaloblastic anemia, are frequently the consequence of the different pathological conditions which often affect elderly patients. This review will consider the most important alterations of hemopoiesis and coagulation in the elderly, the causes capable of influencing hematological changes in old people, and their pathogenesis. Some of the major diagnostic problems encountered in the management of elderly subjects with hematological changes are also addressed. In the presence of an elderly patient with hematological alteration, it is necessary to follow a precise diagnostic schedule, which should first of all exclude the presence of a primary hematological disorder, and consider the different extrahematological conditions which frequently occur in elderly subjects (malignancies, malnutrition, chronic infections from immunological abnormalities, hormonal changes, deficiencies of various organs and systems etc.) and are responsible for many different hematological changes. These must be tackled rationally so that treatment may not only be symptomatic, but may also directly intervene on the cause of the disorder.

The structure, biology and potential therapeutic applications of recombinant thrombopoietin

Platelets, an integral component of hemostasis, are produced by megakaryocytes derived from the differentiation of pluripotent stem cells in the bone marrow or spleen. After decades of study, the regulation of this process is still not well understood. However, the recent cloning and characterization of thrombopoietin, a ligand for the receptor encoded by the c-mpl proto-oncogene, provides new insights into the humoral regulation of megakaryocytopoiesis and platelet production. Consistent with the proposed role as a major physiological regulator of megakaryocytopoiesis, thrombopoietin has potent effects on megakaryocytopoiesis in vitro and in vivo. In addition to the original supposition that thrombopoietin functions as a late-acting megakaryocyte maturation factor, recombinant thrombopoietin proves also to be a potent stimulator of hematopoietic progenitor cells, inducing them to undergo proliferation and differentiation into megakaryocytic colonies. When administered to mice, thrombopoietin causes an increase in peripheral platelet numbers to previously unattainable levels within a few days. Studies of the efficacy of thrombopoietin are underway. It is envisaged that this new cytokine will have widespread applications as a therapeutic agent for the management of bleeding due to thrombocytopenias, in particular those resulting from cancer chemo- or irradiation therapy.