Introduction: Often the blood sample in patients exposed to serial blood exams is taken from the venous cannula (PVC) to avoid a second venipuncture.
Aim: To assess whether blood draws from PVCs are more haemolized than those drawn from phlebotomy, and if the blood drawn from a cannula interferes with the test results.
Methods: A bibliographic search was conducted in PubMed, Cinhal and Ovid, with the following key words: Peripheral Catheter, Blood Specimen Collection, Blood Sample, Haemolysis, 19 articles were identified (including 2 meta analyses), selecting the articles involving emergency departments.
Results: The meta-analyses agree on the lower risk for haemolysis in blood drawn from a needle: risk reduction of 84% (RR=0.16, IC 95% 0.11-0.24) (Heyer et al); the blood draw from PVC increased the risk for hemolysis of 7% (RR 1.07 IC 95% 1.06-1.08, p<0.001) (Lippi et al). Manual aspiration reduces the risk for hemolysis compared to the vacutainer equipment. However, the results of tests drawn from PVC are not significantly different compared to the classical phlebotomy.
Conclusions: Blood draws from PVC bear an higher risk for heamolysis but can be safely used for most diagnostic exams, with the exception of blood gase.