Proper Needle Selection for Blood Collection

September 2019 - Vol.8 No. 8 - Page #18

Given the degree to which patient satisfaction has become an increasingly important metric in the success of health care providers, special focus must be placed on front-line patient interactions, such as phlebotomy. Despite the requisite nature of this process to numerous laboratory operations, it remains a common area of dislike, pain, and anxiety for many patients. Among the initiatives available to mitigate these issues, the use of smaller needles and decreased insertion force may help reduce the occurrence of painful draws.

A common phlebotomist question is whether to use a straight needle or a butterfly needle to increase efficiency and reduce pain during blood collection. Drawing blood for laboratory analysis is an essential task that may be performed by several different clinicians in the course of a given day. As such, all staff that perform venipuncture and phlebotomy services should be educated on the proper techniques performed with the least amount of patient discomfort.


Phlebotomy Tools

While the practice of venipuncture involves identifying an ideal vein and successfully collecting blood samples, it also involves acquiring intravenous (IV) access for IV medication therapy or the sampling of venous blood. Medical professionals must follow standard protocols for specimen collection to ensure accurate diagnostic results, as an error during the collection process affects all downstream analytics. Among the decisions a skilled phlebotomist must make is determining whether to use a straight needle or a butterfly (winged infusion) blood collection needle. This decision is complicated by the concept that although straight needles are generally considered safer and superior for phlebotomy, there are unique circumstances where this is not be the case.

During phlebotomy, blood collection can be performed using a variety of needle types and sizes, and collection devices. Butterfly needles often come with flexible tubing, whereas straight needles connect to a vacuum container and a syringe. When collecting blood samples, it is essential to choose the best possible resources for the patient, the process, and the facility.

The Straight Needle

The straight needle is attached to a tube holder or syringe prior to collection. If the user selects the tube holder, the phlebotomist inserts the needle into the vein and then places an evacuated tube onto the backside of the straight needle to withdraw the blood specimen.

The back side of the cannula is flexible rubber over the posterior end of the cannula that seals the needle when not in use. Once the operator connects the tube, it breaks the seal, and the vacuum in the evacuated tube automatically withdraws the specified volume of blood. A flexible rubber fitting prevents blood from draining out of the cannula with the removal of each tube. The design of the straight needle and collection system is ideal when multiple samples are required, as many tubes can be attached to and removed from a single needle. Straight needles are commonly available in 21 and 22 gauge.

The generally accepted benefits of straight needles include needle stick reductions, quality venous samples, and cost savings. However, a few extenuating factors lend preference to using the butterfly needle, including when working with small and/or fragile veins.

The Butterfly Needle

The butterfly needle, or a winged-infusion blood collection system, connects with slender tubing for smooth access of difficult veins. The needle is short and straight with plastic wings for the phlebotomist to hold during insertion. The tubing attaches to a connector and either a syringe, vacuum tube holder, collection bottle, or other tubing. The common butterfly needles are 1/2 to 3/4 inches long and come in a range of gauges, with 21 and 23 gauge the most frequently used. The smallest gauge, 25, is used primarily with pediatric patients.1 The short needle length allows the phlebotomist to insert it at a shallow angle that can increase the ease of use. Usually, there is a safety device that slides over the needle to lock it after it has been used to minimize the risk of needle stick.

The design of the winged-infusion blood collection needle is ideal for those with small or fragile veins (eg, hands and feet), including neonatal/pediatric, geriatric, oncology, and burn patients. For these cases, the very finely bored 25-gauge needle is the preferred method. Of note, it is best to avoid straight needles with patients who experience uncontrolled movements, such as tremors or seizing, due to the increased risk of nerve damage.2

World Health Organization Recommendations

When assessing whether to use the straight needle or the butterfly needle, review the recommendations of acknowledged professional organizations, such as The World Health Organization (WHO) guidelines on phlebotomy best practices that support the primary use of the straight needle (other than in the conditions mentioned above).3 The WHO describes the straight needle and syringe as possessing a variety of sizes and gauges, being readily available, and beneficial for a variety of blood draws (including pediatric population), and if heparinized, arterial blood collection. The WHO also states that butterfly needles are recommended for difficult to access, small veins in pediatric patients, the elderly, and other at-risk

Proper Use of the Winged Collection System

In addition to the scenarios described previously, butterfly needles are best used for blood cultures, patients with bleeding disorders, and venous blood gases.2 Furthermore, butterfly needles benefit patients who cannot physically change the position of their arms or if ten or more tubes are to be collected at one time.2

These specialized uses notwithstanding, improper use of butterfly needles can lead to a higher risk of needlestick injury due to the butterfly design, which may encourage the user to release control of the needle to free one hand to support the rear of the kit while affixing and withdrawing the collection vial on the device.4 Releasing the sharp at this point breaks OSHA regulations, and any design that leads to a lack of control is a deviation from good practice. The butterfly needle also can be costly at nearly three times the expense of a straight needle (cost dependent on purchasing arrangements).5

Straight Needle Benefits

Straight needles are generally considered the first choice for blood sample collection, as they are less prone to clotting (versus the flexible tubing used in winged-infusion blood collection systems) and less prone to hemolysis than collection through IV catheters. A 2003 study to evaluate risk factors for clotting in blood samples found that straight needles are preferable to IV catheters due to decreased risk of hemolysis.6 Also of note, in a 2008 study, straight needles that retract were found to be the safest and lead to a 62% reduction in the risk of needlestick injuries.7

Although secondary to patient and user safety, cost is not to be ignored when considering the volume of use involved in phlebotomy supplies. Thus, straight needles are relatively cheap, costing less than twenty cents a specimen draw. Therefore, hospitals and laboratories should monitor the use of butterfly needles carefully, as judicial evaluation of available patient veins, available needle sizes and types, and collection kit choice is critical.


Choosing the correct vein, collection tube, device type, and needle size for each individual patient is vital to proper phlebotomy, the quality of which impacts all other subsequent processes. Given the evidence, straight needles offer greater safety against needle sticks due to poor technique, generally have less hemolysis and clotting, and can provide significant cost savings. That said, butterfly needle sets should be on hand and used for their specific, beneficial purposes. Attention to quality in phlebotomy is a boon to all laboratory services.


  1. Lippi G, Salvagno GL, Montagnana M, et al. Influence of the needle bore size used for collecting venous blood samples on routine clinical chemistry testing. Clin Chem Lab Med. 2006;44(8): 1009-1014.
  2. Alberta Health Services. Performing Blood Collections Using a Butterfly Needle. Preanalytics and Specimen Handling. 2018. Accessed: 7.20.19
  3. World Health Organization. WHO guidelines on drawing blood: Best practices in phlebotomy. Geneva, Switzerland; 2010. Accessed: 7.20.19
  4. Fischel L. Inherent Dangers of Phlebotomy Needles & Available Solutions. Healthbeat. 11(2), 1-14. Accessed: 7.20.19
  5. East Coast Medical Supply. 2019. Accessed: 7.20.19.
  6. Grant M. The effect of blood drawing techniques and equipment on the hemolysis of ED laboratory blood samples. J Emerg Nurs. 2003;29(2): 116-121.
  7. Whitby M, McLaws ML, Slater K. Needlestick injuries in a major teaching hospital: The worthwhile effect of hospital-wide replacement of conventional hollow-bore needles. Am J Infect Control. 2008;36(3):180-186.

Caitlin Goodwin, MSN, CNM, APRN, is a certified nurse-midwife at the Cleveland Clinic in Cleveland, Ohio. She has over 10 years’ experience working in pulmonary intensive care, obstetrics, and pediatric nursing. She received a MS in Nursing from the University of Toledo in Toledo, Ohio, and a MS in Nurse-Midwifery from Frontier Nursing University in Hyden, Kentucky.


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