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Obtaining Blood Samples From Peripheral Intravenous Catheters: Best Practice?

2009; American Association of Critical-Care Nurses; Volume: 18; Issue: 5 Linguagem: Inglês

10.4037/ajcc2009686

1937-710X

Margo A. Halm, Melissa Gleaves,

Sepsis Diagnosis and Treatment

Occasionally, nurses perform phlebotomy via intravenous catheters, especially to improve efficiency in short-stay or procedural units. The intent of this practice is to reduce the number of venipunctures and thus increase patients' comfort. However, obtaining laboratory specimens from peripheral intravenous catheters may hemolyze the specimens, and can even dislodge catheters and necessitate restarts. Both of these scenarios may lead to multiple needle sticks and delayed treatment, not only reducing patients' satisfaction but also increasing costs of care.1Hemolysis is a rupture of red blood cells with a release of hemoglobin and other intracellular contents into the plasma.2 In vitro hemolysis interferes with tests such as blood bank/coagulation testing and measurement of levels of creatine kinase, lactate dehydrogenase, potassium, iron, digoxin, alanine and aspartate aminotransferase, and β-human chrorionic gonadotropin.3 Depending on the level of hemolysis, specimens may need to be rejected and another sample would need to be collected.Overall, hemolyzed specimens account for nearly 60% of rejected specimens.4 Factors that contribute to hemolysis vary from anatomical and physiological characteristics to equipment and techniques used during phlebotomy.3 According to the American Society for Clinical Pathology,2 a 2% hemolysis rate is considered best practice. In this review, we synthesize available evidence about the effect of collecting blood samples for laboratory tests from peripheral intravenous catheters on hemolysis rates in the specimens.MEDLINE and CINAHL were the search engines used. Key search words were phlebotomy, intravenous catheters, Vacutainers (Becton, Dickinson, and Company, Franklin Lakes, New Jersey), and hemolysis. Both research evidence and manufacturers' evidence were included.Eight studies were retrieved (Table 1). Designs included observational, descriptive, comparative, and experimental. In half of the studies,2,6–8 hemolysis was compared between specimens collected from intravenous catheters and specimens collected from venipunctures; in 1 study,5 hemolysis was compared between 5- and 10-mL tubes; and in 3 studies,1,3,4 causes of hemolysis of specimens obtained from intravenous catheters were investigated. In most of the studies, hemolysis was assessed via visual inspection to detect a color change indicating presence of hemoglobin; in a few studies, researchers used spectrophotometers or daily comment logs.Hemolysis varied considerably between methods and units. Hemolysis occurred in 3.3% to 77% of blood samples obtained via intravenous catheters, whereas it occurred in only 0% to 3.8% of blood samples obtained via venipuncture. Hemolysis of samples obtained from intravenous catheters via different methods ranged from 5.6% to 77% for samples obtained with a Vacutainer, 3.3% to 49% for samples obtained with a syringe, 12.8% to 49% for samples obtained from new intravenous catheters, and 24% for samples obtained from established intravenous catheters. In 1 study,1 researchers reported that hemolysis rates were higher for specimens collected in the emergency department than for specimens collected in medical units. This finding was attributed to trained phlebotomists collecting blood samples on the medical units. Overall, these results reflect higher hemolysis rates when laboratory specimens are collected from newly inserted intravenous catheters and when Vacutainers are used with new or established intravenous catheters. Furthermore, in 1 study,6 not only did collection of blood samples from intravenous catheters increase hemolysis, but tests were canceled 20 times more often when samples had been collected from intravenous catheters rather than venipuncture.In 1 study,4 in vivo hemolysis accounted for 3% of hemolyzed specimens. These cases were associated with prolonged extracorporeal circulation during cardiac surgery, acute alcohol poisoning, transfusion reactions, necrotic-hemorrhagic pancreatitis, and rhabdomyolysis from drug overdose. In 31% of these cases, the presence of in vivo hemolysis was not suspected by clinicians, thus the hemolyzed finding was essential for identifying a critical clinical situation.Factors associated with hemolysis can be categorized as anatomic, equipment-related, or technical. Anatomic and physiological factors included the right hand, forearm, or antecubital space; smaller distal veins; and discharge diagnoses (respiratory, gastrointestinal, reproductive, dermatological, endocrine).1,3 In terms of location, one explanation may be that it is easier to obtain samples from the dominant side of the patient's body.3 Compared with the antecubital fossa, distal veins may also lead to more hemolysis because of their smaller diameters and thus slower flow and more resistance. These findings merit further research.Equipment factors focused on plastic, smaller, and new intravenous catheters; use of Vacutainers or syringes; partial catheter obstructions; and laboratory tube size.1–4,5,8 Partial catheter obstructions were thought to increase aspiration force when syringes were used to collect samples. For tube size, findings were mixed: in 1 study,3 researchers reported increased hemolysis with smaller tubes, whereas in another study5 researchers reported increased hemolysis with larger tubes. More research is needed to understand the mechanism of how low- or high-vacuum collection tubes are implicated with hemolysis.Technical factors included difficult catheter placements or difficulty collecting blood samples, multiple attempts to place an intravenous catheter, filling tubes less than half full, and using excessive force when aspirating blood or filling tubes.1,3,4 Although Dugan et al3 reported that hemolysis rates decreased significantly after nurses were instructed on how to collect samples from extension tubing to reduce pressure and manipulation on the catheter hub, their reported hemolysis rate of 3.7% was still higher than the national 2% benchmark. Additionally, these investigators commented that the hemolysis associated with difficult catheter placement may have been due to manipulation of the patient's extremity and extended tourniquet time, which increases venous pressure and extravasation of fluid into the intracellular space.9 Fullness of the collection tube may affect hemolysis by a poorly understood mechanism of pneumatic tube transportation.1In addition to research findings, evidence from manufacturers discourages collecting blood samples for laboratory tests from intravenous catheters. Intravenous catheter material often consists of soft plastic that stays open under positive pressure of intravenous delivery of fluids and medication. However, the soft plastic can collapse under negative pressure when blood samples are collected, causing turbulence and hemolysis.10The reported studies and manufacturers' information provide class III evidence against collecting laboratory specimens from peripheral intravenous catheters (Table 2). Although nurses may collect blood samples from peripheral intravenous catheters to reduce the number of needle sticks that patients must endure, this practice is associated with greater hemolysis. Hemolysis can lead to delays in diagnosis and treatment while samples are collected and analyzed again, potentially affecting patients' length of stay, especially in short-stay settings.As a result of this evidence, blood samples should not be collected when new intravenous catheters are started or from established intravenous catheters. Some clinical exceptions include patients receiving thrombolytic agents or patients at increased risk of bleeding, or possibly in an emergency situation with limited vascular access, although hemolysis may still result and delay critical treatment. In general, blood samples for laboratory tests should be obtained via venipuncture, preferably by using Vacutainers with straight needles because such needles provide a smooth, solid inner lumen surface that is unaffected by drawing pressure, which can increase hemolysis. If blood collection into a syringe cannot be avoided, larger syringes (3–10 mL) are recommended.9 The antecubital fossa is the preferred site for collecting blood samples for laboratory tests because of the faster blood flow and thus decreased resistance associated with greater vessel diameter.1 Tourniquets should also be disengaged as soon as the flow of blood through the needle is established.9 Table 3 summarizes additional actions that nurses can use to prevent hemolysis.Once blood samples have been collected, Carraro et al4 caution that hemolyzed specimens cannot simply be rejected. Laboratories must alert clinicians so that in vivo hemolysis can be ruled out. Therefore, clinicians can more quickly identify clinical situations that require immediate intervention, potentially improving patients' outcomes.Hospitals are encouraged to develop or revise standardized protocols to reflect venipuncture as the best practice for collecting blood samples, except in patients at increased risk of bleeding or patients with difficult venous access. Standardization of practice and education of staff will help eliminate the equipment and technical factors associated with greater hemolysis. However, strategies must be developed to overcome barriers to changing this practice, including personal preference and feasibility.1 By sharing the evidence with clinicians and emphasizing the intention of promoting quick and reliable access to essential clinical data, some barriers to practice change may be overcome.The authors acknowledge the efforts of the 2009 Nursing Research Council in critically reviewing the literature