Higher Diagnostic Blood Loss Tied to Higher Anemia Risk

WEDNESDAY, Aug. 10 (HealthDay News) -- Increased blood loss from diagnostic phlebotomy increases the risk for moderate to severe hospital-acquired anemia (HAA) among patients with acute myocardial infarction (AMI), according to a study published online Aug. 8 in the Archives of Internal Medicine .

Adam C. Salisbury, M.D., from Saint Luke's Mid America Heart and Vascular Institute in Kansas City, Mo., and colleagues investigated the association between diagnostic phlebotomy and risk of HAA among 17,676 patients, in 57 medical centers, with AMI and no anemia at the time of admission, but who developed moderate to severe HAA, between 2000 and 2008. Total diagnostic blood loss for each patient was calculated by multiplying the standard volume for each tube type by the number and types of blood tubes drawn. The correlation between phlebotomy and risk of developing moderate to severe HAA was derived through hierarchical modified Poisson regression after adjusting for site and confounders.

The investigators found that 20 percent of the patients developed moderate to severe HAA. The mean phlebotomy volume was significantly higher in patients with HAA than without (173.8 mL versus 83.5 mL). Across the hospitals there was significant variability in mean diagnostic blood loss (moderate to severe HAA range from 119.1 to 246.0 mL; mild or no HAA range from 53.0 to 110.1 mL). Each 50 mL of blood drawn was associated with an 18 percent increased risk for moderate to severe anemia (relative risk, 1.18), which showed only a modest reduction after multivariable adjustment (relative risk, 1.15).

"Blood loss from phlebotomy is substantial in patients with AMI, varies across hospitals, and is independently associated with the development of HAA," the authors write.

Several of the study authors disclosed financial relationships with the pharmaceutical and health care industries.

Cardioembolic stroke and Pathophysiology of Cerebral Infarction ...

• Another important cause of acute brain infarction is an embolus. Most embolic disease is caused by thrombus formation in the heart (cardioembolic) or extracranial vessels (aorta or carotid). The thrombus then travels distally into one of the cerebral vessels, most commonly the middle cerebral artery. Frequently, a second stroke follows because the underlying cause of the embolus remains.

• Cardioembolic stroke is commonly associated with atrial fibrillation, myocardial infarction, and valvular heart disease. Individuals with these cardiovascular disorders are usually placed on a regimen of anticoagulation therapy to prevent this dreaded complication.

• There are two other types of brain infarction: lacunar stroke and global hypoperfusion (or watershed) stroke.

Lacunar Stroke

Lacunar stroke refers to small infarcts (less than 1 cm) that occur deep in the brain because of obstruction of very small intracerebral vessels. Lacunar stems from the Latin word “lacuna,” which means “little lake.” It refers to the small areas of infarcted brain tissue surrounded by normal brain. These strokes occur most commonly in individuals with diabetes and hypertension and can result in very localized and unpredictable neurologic deficits.

• Global hypotension (or watershed) strokes occur when total brain perfusion falls because of cardiovascular collapse like that seen in severe myocardial infarction, major dysrhythmias, overwhelming systemic hemorrhage, or massive pulmonary emboli.

• The parts of the brain first affected by this type of stroke are near the surface of the cortex. They are in areas where the appearance of the cerebrovascular vessels is reminiscent of the small streams that feed a large river or lake, thus the name watershed. This type of stroke results in global cognitive dysfunction, irreversible coma, and death.

Hemorrhagic stroke is most often associated with :

• hypertension and weakening of the walls of intracerebral vessels.

• congenital aneurysms or vascular malformations.

• condition that is associated with an increased risk for bleeding, including thrombocytopenia (e.g., caused by drugs or bone marrow disease)

• coagulopathies such as liver disease, hemophilia , and iatrogenic anticoagulation.

• Blood is ejected through the damaged wall of the vessel into the surrounding brain tissue and can leak into the ventricles.

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