Red blood cells (erythrocytes) normally survive 90-120 days in the circulation. Hemolysis is the lysis of red blood cells with release of hemoglobin, i.e., destruction of red blood cells at the end of the cell’s life cycle. Red cell life span may be shortened (prematurely destroyed cells) in a number of disorders, including uremia, resulting in anemia when bone marrow activity cannot compensate for the erythrocyte loss .
More than 200 types of hemolytic anemias are known. The clinical presentation depends on whether the onset is gradual or abrupt and on the severity of erythrocyte destruction . Hemolytic anemias can be grouped in hereditary or acquired, intracorpuscular or extracorpuscular. Intracorpuscular abnormalities are mainly due to inherited disorders of the red blood cell interior or the red cell membrane. Extracorpuscular hemolytic anemias are mainly acquired and caused by factors outside the red blood cell, e.g. hypersplenism, antibodies towards the red blood cell, drugs, infections, toxins and mechanical destruction due to traumatic disruption of the red cell membrane .
Mechanical destruction occur within the vasculature in microangiopathic conditions, e.g. thrombotic microangiopathy, hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and with intravascular prostheses, e.g. cardiac valves, intra-arterial stents and stent grafts [1, 3]. Mechanical destruction outside the vasculature may be caused by extra-corporeal therapies, e.g. hemodialysis and cardiopulmonary bypass perfusion during cardiac surgery, and also due to indwelling catheters [4, 5, 6, 7].
Specimen hemolysis (hemolyzed blood samples) is reported to be the cause of 95 % of all hemolysis (measured as hemoglobin release) found in blood samples sent to laboratory for analysis. Specimen hemolysis is due to incorrect sampling procedures or incorrect handling and transport after blood sampling . It is important to note that this is an artefact and does not reflect a hemolytic condition in the patient.
In dialysis patients the differential diagnosis of hemolysis is broad, and includes all causes of hemolytic anemias seen in nonuremic patients and some causes specific to patients treated with hemodialysis. Occasionally hemolysis can be severe, associated with hypotension, back pain and encephalopathy developing during the dialysis procedure .
Hemolysis related to hemodialysis procedures has varying etiologies. The dialysis solution may contain contaminants (e.g. chloramine, copper, zinc, nitrates, nitrites), excessive amounts of formaldehyde or other sterilants, it may accidentally be overheated or hypo-osmolar, all of which may cause damage to red blood cells [4,5].
Kinked or defective blood line tubings, blood pump malocclusion, central dialysis catheter malfunction peripheral hemodialysis cannulas and double-pump single-needle dialysis may lead to mechanical destruction causing mechanical hemolysis [4,5,6,9,10,11,12]. In mechanical extravascular hemolysis a clinical picture resembling hemolysis within the vasculature (e.g. microangiopathic hemolysis, hemolysis due to intravascular prostheses or stents) with the blood smear showing schistocytes and helmet cells may be seen .
If hemolysis is clinically suspected to develop during a dialysis treatment, the treatment should be stopped immediately and the blood in the extracorporeal circuit should not be given back to the patient. The medical investigation of the suspected hemolysis is a responsibility of the respective physician. The referenced literature [1-13] may provide guidance for such an investigation.
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