Midline intravenous catheters (MCs) have been used in clinical settings since the 1950s and are an alternative for intravenous (IV) access for giving infusions and medications for long-term therapy in patients who have limited IV access and can be used up to one month duration. Accessing the midline catheter for blood sampling is sometimes used for those patients who have difficult IV access and those with the need for frequent blood sampling for testing. Studies have reported on the outcomes of using MCs, however, little is known or reported about the procedures used to sample blood from midline catheters or outcomes from using the MC for this purpose. While the Infusion Nursing Society (INS) standards include recommendations for blood sampling from central venous and short peripheral catheters (SPCs), the newest INS 2021 standards indicate that, while midline catheters might be used to obtain blood samples, there was no evidence available regarding the processes or outcomes of performing this procedure.
In general, IV catheters are intended for giving fluids or medications in a forward, antegrade flow rather than a backwards, retrograde flow when withdrawing blood to test for patency or for laboratory testing. The impact of the flow dynamics and effects on IV catheter performance and vasculature when withdrawing blood from MC is not well known and no recommendations or procedures exist for sampling blood from midline catheters, although it is known that this is performed in the clinical setting.
Hemolysis, the injury or splitting (lysis) of red blood cells, is an unintended and unwelcome consequence of sampling blood from intravenous catheters. The release of contents in red blood cells when “lysed” can alter some blood test values, making blood samples unusable for analysis. This may result in the need to draw another blood sample with potential delays in care, repeated venipunctures and vein injury, and financial impact. Using SPCs for blood sampling is associated with increased hemolysis and may result from mechanical shearing and turbulence encountered during withdrawal of blood. The American Society for Clinical Pathology recommends that hemolysis rates at or below 2%, and reports rates from 3-32% hemolysis occurring in acute clinical settings.
Midline Catheter Design Changes to Improve Blood Draw
Recently, anecdotal feedback from practitioners experiencing hemolyzed samples when withdrawing blood samples from midline catheters prompted a company to develop a change in their midline catheter to overcome hemolysis. After conducting laboratory studies on fluid dynamics when withdrawing blood through the catheter lumen, the company designed the MC with a reinforced tip to reduce hemolysis during backwards flow when withdrawing blood for sampling. This MC (PowerGlide Pro™; BD, Salt Lake City, UT) received 510K clearance from the U.S. Food and Drug Administration in September 2016. However, this MC had not undergone assessment in a real clinical setting to evaluate for performance and rates of hemolysis and was needed.
Given that little to no evidence was found in the literature about procedures or clinical outcomes from using MCs for blood sampling, my colleagues and I at Orlando Health conducted an observational study to explore the practices used by clinicians and outcomes when using the MC for blood collection.
The purpose of this study was to assess the processes and outcomes of using the MC to sample blood for laboratory testing. We aimed to evaluate the MC in an acute care setting for hemolysis rates when blood was drawn from the MC for laboratory analysis, catheter outcomes, and nurses’ practices and perceptions when sampling blood from the MC. Since only the MC with the reinforced tip was used at this facility, we only studied these outcomes in that particular catheter.
Our study findings were published in the most recent issue of the Journal of the Association for Vascular Access (JAVA), Volume 25, No. 4.
Findings from this study showed that we had very low rates of hemolysis and withdrawing blood from the catheter did not significantly impact dwell time of the ability to complete IV therapy. Since we only tested the one type of MC designed to lessen hemolysis, it is not known if these outcomes would be achieved with other types of MCs or in different settings. We found that MCs were mostly removed at discharge from the hospital, so it was not possible to determine longer-term outcomes from blood sampling or its effects on catheter dwell time if it were to have remained for longer periods of time. We learned from focus groups with nurses, that they learned how to withdraw blood from MCs from their preceptors or other nurses and tended to use processes recommended for phlebotomy from other types of vascular access devices, such as central venous or short peripheral catheters. Since there are still no recommendations from the Infusion Nurses Society about using MC for blood withdrawal, more information gained from this study helped inform nurse actions used for blood withdrawal from MCs and opportunities still exist to develop procedures and practices for this purpose.
Recommendations for Practice
This was the first study of this kind known to evaluate the outcomes and processes used for blood withdrawal for sampling from a midline catheter. Thus, more information and studies are needed to develop and evaluate outcomes using other types of MCs and in other settings. Further, other recommendations are to develop and test procedures for blood sampling from MCs to contribute to and establish standards of practice in this area.
Editor’s Note: The study mentioned in the article was funded by Becton Dickinson. The author has no financial relationship with BD .
Photo: Anastasia Usenko, Getty Images