It refers to the process whereby red blood cells rupture and their contents leak out into the bloodstream. Hemolysis can happen in vivo or in vitro, the first being linked to medical conditions, and the latter being a marked challenge for the medical sector as it hinders clinical testing.

Below we discuss the two scenarios of red blood cell lysis, when it occurs in the body and outside of it, giving an overview of how it occurs and its significance.

Red blood cell lysis in vivo

In vivo hemolysis has numerous causes and is linked with multiple diseases. It is characteristic of a group of conditions known as hemolytic anemias, the causes of which include immune-mediated erythrocyte destruction, such as neonatal isoerythrolysis; incompatible blood transfusion; drugs including penicillin and heparin; fragmentation, such as disseminated intravascular coagulation (DIC), vasculitis, and uremia; hemoparasites, such as Babesia spp.; infectious agents, including Leptospira, Ehrlichia, Clostridium, and equine infectious anemia virus; hypo-osmolality; hypophosphatemia; some chemicals and plants, such as red maple and phenothiazine; and liver failure.

Other causes of hemolysis include artificial heart values, heart-lung bypass machines, pyruvate kinase deficiency, Wiscott-Aldridge Syndrome, HELLP Syndrome, and more. In total, there may be more than 50 causes of in vivo hemolysis. These causes can be classified as immune or nonimmune, hereditary or acquired.

Essentially, hemolysis occurs in vivo when the rate of red blood cell destruction is increased. This leads to hemoglobin being released into the bloodstream. Usually, red blood cells live for around 120 days, and when they die, the spleen removes them from the blood.

Uterine Artery Hemorrhage

Hemorrhage from the uterine arteries (i.e., the uterine branch of the vaginal artery), the uterine artery, and the uterine branch of the ovarian artery is the most common cause of death of the postpartum mare. A study of 98 mares that died postpartum revealed that 40 died from a ruptured uterine artery.61 It is uncommon for these arteries to rupture at times other than in the first several days postpartum.

The condition is usually seen in older mares. Affected mares are often initially in quite an amount of pain, especially if the blood is contained within the broad ligament. The rectal examination in these mares generally reveals a fluctuant mass in the broad ligament. If the broad ligament ruptures and the blood gains access to the abdominal cavity, the mare may not exhibit as much pain. On rectal examination, the broad ligament has a more edematous feel. These mares generally have very pale mucous membranes, a weak pulse, and an elevated heart rate, and they are anxious and often sweating.

Treatment varies depending on the clinician, but it essentially follows the approach taken for hemorrhagic shock (see Chapters 1 and 4).58 Attempts to ligate the ruptured artery have met with limited success.

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Avoiding hemolysis of biological samples

Hemolysis of blood samples before they are tested is a major challenge within the medical industry. It is particularly impactful on emergency departments who need to acquire accurate test results with speed. Hemolysis that occurs in vitro can happen during the collection of the sample, or through the handling of the sample.

It is a significant problem for clinical testing because the lysis of red blood cells can affect the results. The contents that leak from the broken-down cells can directly impact the reading of the results, or they can cause interferences with laboratory analyzers.

Horse Blood Laked
Horse Blood Laked


The magnitude of the impact is dependent on the type of test being performed and the reagents being used. Tests for potassium, lactate dehydrogenase, and aspartate aminotransferase are particularly affected by hemolysis, where the release of cellular contents into the blood plasma falsely increases the values of the target substances.

Other tests are affected in different ways. When only small levels of hemolysis are detected, the levels are reported along with the test result. When levels of hemolysis are high, the results cannot be relied on, and it calls for a recollection of the sample.

Studies have found that hemolysis is the most common cause for samples to be rejected, with 60% of rejections being attributed to hemolysis. Hemolyzed specimens are five times more frequent than the second most common cause of specimen rejection. This demonstrates the severity of the problem that hemolysis brings to the medical community.

Uterine hemorrhage

Hemorrhage from the uterine artery is most commonly seen in older multiparous mares, but has been seen in primiparous mares. Dystocia (q.v.) does not appear to increase its incidence. Hemorrhage is not always fatal if it is contained within the broad ligament and associated tissues, but the mare will exsanguinate if the hematoma ruptures into the peritoneal cavity or the uterus.

Initial signs, seen within minutes or hours of parturition, are acute moderate to severe colic and sweating, with rapid pulse, which progresses to cardiovascular shock. The mare should be kept quiet with mild sedatives and analgesics. Hypotensive tranquilizers such as acepromazine or detomidine may help to encourage clotting to occur in some cases but may risk acceler-ating cardiovascular collapse (q.v.) in others. Fluid therapy with blood or plasma expander or hypertonic saline does not seem to alter the course of the condition and may be contraindicated as it often stresses the mare and increases blood pressure and further hemorrhage, delaying clotting. Treatment with hypertonic saline solutions has been reported to be useful in some cases. In mares that survive, the hematoma will be palpable for some considerable time.



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