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Published: August 2013
Hot Topic Q&A is an opportunity for viewers to submit questions to the Hot Topic presenter. The opportunity to submit questions for this topic is now closed.
The following questions were submitted by viewers and answered by the presenter, Brad Karon, MD, PhD, Associate Professor of Laboratory Medicine and Pathology, and Co-Director of Laboratory Services in the Division of Clinical Core Laboratory Services at Mayo Clinic in Rochester, Minnesota.
Questions are presented as submitted (unedited).
We have worked with ED to reduce the incidence of IV start blood draws, without eliminating them altogether. By defining the issues related to these draws and working with ED physician and nursing leadership to encourage venipuncture whenever possible, we have reduced the incidence of IV blood draws in the ED from 38% of all ED draws to only 5% of all ED draws. The overall rate of redraws in ED in the same time period fell from 3.8% to 1.8%.
We very rarely report hemolyzed specimens with a comment, but rather issue an automatic redraw in almost every case that the free hemoglobin content exceeds levels the test manufacturer indicates cause interference. We measure H index on our automated equipment as done in many labs, and if the H index is below the threshold for the test report the result, if above issue a redraw. We involve a resident or fellow on call, or lab director, in any instance where reporting of results with a comment is required. The trend is moving away from reporting results with "disclaimers."
As far as I am aware, the IV start draw is associated with hemolysis, but not contamination or other issues that could give falsely elevated values for most tests. This is assuming the “IV start” draw is performed before the IV line is hooked up to any other medication or fluid. Hemolysis will cause falsely elevated potassium and AST (mainly, probably a few others) which is the problem with using these specimens.
We reviewed our internal hemolysis/redraw data, and encouraged our ED nurses to reach out to their colleagues in other institutions and their professional societies, listserves, etc to find out what other ED nursing groups were doing about this issue. Once they started asking around to their colleagues in other EDs, they realized that other groups had addressed this issue with success by limiting IV draws.
Our main emphasis since this data was collected has been working with nursing to reduce the frequency of IV start draws, since that is most likely to impact the rate of hemolyzed or unacceptable specimens. By doing that we have reduced the incidence of IV blood draws in the ED from 38% of all ED draws to only 5% of all ED draws. The overall rate of redraws in ED in the same time period fell from 3.8% to 1.8%. That is more recent data not presented, though it demonstrates that minimizing IV start draws is effective.
It depends to some extent on what test is being performed, but for many tests that require fasting, intake of non-carbohydrate containing liquids a few hours before testing will not impact results. We have worked here to make 1 standard definition of “fasting” that encompasses most test requirements. We allow clear liquids (water, black coffee) up until 2 hours before a test or procedure. The definition of fasting should be clarified for all procedures in your institution if possible.
I am not aware of any literature that suggests that clots can be introduced by using IV catheters for blood draws.