• Donovan G Dwyer, Margaret Fry, Annabel Somerville, and Anna Holdgate.
• Department of Emergency Medicine, St George Hospital, Gray Street, Sydney, New South Wales, Australia. dwyerd@sesahs.nsw.gov.au
• Emerg Med Australas. 2006 Oct 1;18(5-6):484-8.

ObjectiveBlood aspiration through i.v. cannulae is a common ED sampling method. It is, however, associated with increased haemolysis rates when compared with direct venipuncture. Our ED utilizes two common methods of sampling through cannulae. The aim of the present study was to examine the haemolysis rates for these two techniques.MethodsA randomized, single blinded prospective study was performed. From a convenience sample patients were randomized to either 'Method one' (blood taken directly from cannula hub) or 'Method two' (blood taken using an Interlink device through cannula cap). For each group patient demographics, clinical information and haemolysis were analysed. chi(2)-analysis and a multivariate logistic regression model were applied to determine significant relationships.ResultsA total of 1390 patients were enrolled, 694 had blood collected by 'Method one' and 696 by 'Method two', with haemolysis rates of 6.5% and 7.2%, respectively. Univariate analysis showed ease of aspiration to be the only variable to have a strong association with haemolysis (P < 0.0001). After allowing for ease of aspiration the technique used did not significantly affect haemolysis rate (P = 0.7).ConclusionsThe rate of haemolysis is unrelated to the technique of blood aspiration. However, haemolysis rates increase significantly with perceived difficulty of blood draw.

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