Blood collection techniques, heparin and quinidine protein binding.
With the use of glass syringes without heparin and all glass equipment, the percent of unbound quinidine was measured by ultrafiltration and a double-extraction assay method after addition of 2 microgram/ml of quinidine sulfate. Compared to the all-glass method, collection of blood using Vacutainers resulted in an erroneous and variable decrease in quinidine binding related to blood to rubber-stopper contact. With glass, the unbound quinidine fraction was (mean +/- standard error) 10 +/- 1% in 10 normal volunteers, 8.5 +/- 1.5% in 10 patients with congestive heart failure, and 11 +/- 2% in 11 patients with chronic renal failure (although in 8 of the latter 11 patients the percent of unbound quinidine was 4 or more standard errors from the mean of the normal group). During cardiac catheterization, patients had markedly elevated unbound quinidine fractions: 24 +/- 2% (p less than 0.001). This abnormality coincided with the addition of heparin in vivo and was less apparent after the addition of up to 10 U/ml of heparin in vitro (120% and 29% increase in unbound quinidine fractions, respectively). Quinidine binding should be measured with all glass or equivalent equipment.
D001798:Blood Proteins / Q000378:metabolism*; D001800:Blood Specimen Collection / Q000295:instrumentation / Q000379:methods*; D006328:Cardiac Catheterization; D006333:Heart Failure / Q000097:blood; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood; D011485:Protein Binding / Q000187:drug effects; D011802:Quinidine / Q000097:blood*
D001798:Blood Proteins; D006493:Heparin; D011802:Quinidine