Plasma-free hemoglobin interferes with the routine clinical assays of a number of metabolites, electrolytes and enzymes, notably potassium, glucose, creatinine, bilirubin and alkaline phosphatase. Repeated blood draws must be performed to replace inaccurate assays. In a study involving 350 emergency department patients, Raisky, et al. [1994] found significant hemolysis (> 5 mg/dl) in 12% of samples drawn by vacuum tube through stainless steel needles, 42% of samples drawn through Teflon catheters and 55% of samples drawn through polyurethane catheters. Repeated blood draws result in further patient discomfort, additional clinical staff time and resources, and perhaps most importantly, delays in diagnosis. This latter problem may be especially critical in the emergency department, where the need for timely assay results may be acute and where hemolysis rates seem to be greater. Fernandez, et al. [1997] found the need for recollection of blood samples in the emergency department due to hemolysis in 1% of samples drawn by venipuncture and 20% of samples by intravenous (iv.) catheter. Kennedy, et al. [1996] found excessive hemolysis in 3.8% of venipuncture samples and 13.7% of i.v. catheter samples.
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