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Drawing Blood Samples After a Transfusion
When patients are transfused, physicians want to know its effect as soon as possible, often before the unit has completely infused. But can a blood sample drawn during or immediately after a transfusion be reliable? How long should one wait after a blood transfusion before drawing blood for testing?
Every infusate, including and especially donor blood, takes time to circulate before it obtains a homogenous, uniform distribution throughout the circulatory system. If the patient is actively bleeding, homogeneity isn’t likely to occur until and unless the bleeding stops and the chemical and cellular constituents of the blood can equilibrate. When the infusion is donor blood and the sample is drawn too soon, the results may lose their validity before the lab even reports them out. If it’s drawn too late, the physician’s window of opportunity to order more units in time to save the patient could close. It’s every physician’s dilemma.
The time it takes donor blood to achieve homogeneity depends on a multitude of variables including the condition of the patient’s heart, kidneys, and circulatory system, the patient’s pre-transfusion blood volume, the age and volume of the transfused cells, the severity of the hemorrhage, etc.. Regardless, the effect of every transfusion, which can only be reflected by timely and accurate laboratory results, drives the physician’s decisions. Depending on the patient’s condition, waiting for the circulatory system to uniformly distribute the donor unit throughout the body may not be an option.
Cell counts drawn during a transfusion provide little useful information except in cases where the patient’s condition is changing rapidly. It is conceivable that accurate cell counts can be obtained immediately after transfusion.1 Delaying the draw for even an hour after the transfusion may provide more accurate results if time permits, but may be too late to save the hemorrhaging patient.1 Therefore, the timing of post-transfusion draws is a decision that should be made by the physician on a case-by-case basis.
Post-transfusion draws are not just about the patient’s hemoglobin and hematocrit. Each unit of donor blood, even when it’s autologous, impacts far more than a CBC. Since red blood cells lyse during storage, transfused donor blood temporarily raises the concentration of plasma hemoglobin, potassium, ammonia, urea nitrogen, uric acid, LD, serum iron, and other analytes for up to 24 hours depending on the patient’s kidney function and other variables.2,3,4
CLSI doesn’t address post-transfusion cell counts in its venipuncture standard, but the document is quite detailed on the proper procedure for drawing blood from a patient receiving IV fluids of any kind, including donor blood.5 In one passage, CLSI states that draws from the same arm as an infusion should be avoided if at all possible. Although drawing above an active IV is discouraged in many documents,5–7 when unavoidable CLSI suggests collectors have the IV shut off for 2 minutes prior to the puncture, tighten the tourniquet, and perform the puncture as usual. Some authors and studies suggest discarding the first 3-10cc of blood.8–10 All blood drawn from the same arm as an IV infusion should be documented as such.5
- McBride K, Eisenbrey A, Haraden L. Venipuncture after transfusion. Adv. Med Lab Prof Q&A column. January 25, 1999:4.
- Narayanan S. The preanalytic phase an important component of laboratory testing. Am J Clin Pathol 2000;113:429–452.
- Mayhre B. Iron values after transfusion. Tips on Specimen Collection. Medical Economics. Montvale, NJ. 1997.
- CLSI. Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture; Approved Standard—Sixth Edition H3-A6. Wayne, PA: Clinical and Laboratory Standards Institute; 2007.
- Young D. Affects of Preanalytical Variables on Clinical Laboratory Tests—Third Edition. AACC Press Washington, DC. 2007.
- Watson R, O’Kell R, Joyce J. Data regarding blood drawing sites in patients receiving intravenous fluids. Am J Clin Pathol 1983;79(1):119–121.
- Read D, Viera H, Arkin C. Effect of drawing blood specimens proximal to an in-place but discontinued intravenous solution. Am J Clin Pathol 1988;90(6):702–706.
- Garza D, Becan-McBride K. Phlebotomy Handbook. 8th Ed. Upper Saddle River, NJ: Prentice Hall; 2009.
- Dale J. Preanalytic variables in laboratory testing. Lab Med 1998;29(9):540–545.
- Mohler M,Sato Y, Bobick K, Wise L. The reliability of blood sampling from peripheral intravenous infusion lines. Jrnl of Intravenous Nurs 1998;21(4):209.
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It’s About Time
When it comes to drawing blood samples, timing is everything. From the time you receive the order until the sample is handed to the testing personnel, numerous clocks will tick off precious seconds. If they run out of time your ability to deliver samples capable of rendering accurate test results expires, your potential to protect the patient from injury runs out, and your likelihood of escaping a bloodborne exposure has counted down to zero.
Just like the sands of the hourglass, so are the ways of phlebotomy. Before the clock strikes midnight on you and your patients, consider these reminders of the time-sensitive nature of drawing, handling, processing blood samples, and make sure your timing is perfect.
Turnaround time—In healthcare, time saved can be lives saved. Respond to stats immediately, giving the receipt of the sample by the testing personnel in the laboratory the highest priority, but without cutting short any of the other timely items on this list.
Draw time—Draw TDMs and other timed tests precisely. Your patient is depending on you to get it right so his physician can get his medications right. Likewise, respond to fever-dependent blood cultures as if they were stat. By the time bacteria cause a fever spike, their concentration is already on the decline. The faster you respond, the faster the microbiology department will identify the causative organism and the sooner the patient will be on the right antibiotic.
Handwashing time—Too many phlebotomists either skip this step or “technically” wash their hands by merely getting them wet and dry in a hurry. Proper handwashing between patients should take 20 seconds of brisk friction, or as long as it takes to hum the lyrics to “Happy Birthday” twice.
ID time—By not taking the time to properly seek and confirm every patient’s identification, time can run out on them before it should. Eleven percent of transfusion deaths occur because phlebotomists fail to properly ID the patient or the sample.
Survey time—Do you draw from the first vein you find? Not after today. Every patient deserves for you to spend time finding the most prominent vein, and the one furthest away from nerves and arteries. Not only that, but the standards require it.
Cleansing time—One quick wipe is pointless. For routing lab work, cleanse the site thoroughly with isopropyl alcohol. For blood cultures, conduct a 30-second friction scrub, then allow the antiseptic to remain in contact with the skin for at least 30 seconds. Cutting this step short contaminates the culture and cheats the patient.
Tourniquet time—Sixty seconds: that’s the maximum length of time a tourniquet should be applied prior to accessing the vein. If it takes longer to find and access it, release the constriction for two minutes, then reapply and access the vein within a minute. A longer constriction causes changes significant enough to change the way the patient is treated, diagnosed, medicated and managed.
Observation time—After the draw, if you don’t remove the gauze and watch the site for at least 10 seconds after pressure is removed, you’ll never know if the patient is still bleeding or not. Don’t assume everything is okay without taking ten seconds to watch. Time is money, especially when the lack thereof leads to complications and litigation from a subcutaneous hemorrhage that could have been caught.
Label time—“Stat” doesn’t mean “label the sample later.” Nothing should prevent you from taking the time to label all samples in the presence of the patient. Nothing
Spin time—Likewise, “stat” doesn’t mean “centrifuge hard and fast.” Tubes must be spun at the specs established by their manufacturer. Higher RPMs don’t compensate for an abbreviated spin. No physician is in a hurry for the inaccurate result that will be reported.
Processing time—Serum tubes need time to clot. Blood that no longer looks liquid when inverted is a poor test of readiness for centrifugation. Not even for clot-activator tubes can be centrifugation be rushed. Clot activators facilitate complete clotting, not faster clotting. Activator or no activator, serum tubes take 20-30 minutes to clot.
Assessment time—Releasing a patient from your care too soon can be a timely mistake. Ask all patients if they feel all right before leaving their side or allowing them to leave yours. But don’t trust their answer completely. Assess every patient for their potential to pass out regardless of what they tell you. Statistics tell us 2.5 percent of patients will pass out during or immediately following a blood draw. For many, it’s just as much of a surprise to them as it is to you. Know the signs of an imminent loss of consciousness, and be prepared to react.
Add-on time—When a physician wants to know if they can add on a test to a previously drawn sample, the answer isn’t always “yes.” Check the age of the sample and the stability of the analyte. Adding on an inappropriate test can mislead the physician into treating the patient inappropriately. (The Center for Phlebotomy Education offers a “SmartChart” on analyte stability at www.phlebotomy.com.)
Timing really is everything. If you’ve got these times down, your time in healthcare is well spent, and the patients you draw will receive the best possible outcome time and time again. Not only that, but whenever a promotion comes up or a raise is being considered, your supervisor might just think about you and say, “it’s about time.”
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Playing it Safe
Lab Coats Outside the Lab
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On a Personal Note...
It’s a three-hour train ride from Brussels to Luxembourg City. When it’s your first time in Belgium, you don’t open your laptop to work; you look out your window. If you have a moment, follow me.
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Unspun Chemistries and Coags
Can we ship unspun chemistry and coag specimens to a reference lab overnight and expect accurate results?
You are correct to be concerned about analyte stability in unspun specimens. Unless the lab has data showing longer stabilities, aPTTs and many routine chemistries, especially potassiums, may be compromised. Protimes will be fine, but the literature is full of evidence that many other important analytes are affected when not centrifuged and separated within 2 hours. Here’s what a literature search dug up:
- Protimes are stable unspun at room temperature for 24 hours; seven hours at refrigerated temperatures as long as the stoppers remain in place. However, aPTTs are only good for four hours at any temperature.1–3
- When left in contact with the cells, potassium, glucose, LDH and ionized calcium are no longer accurate after 2 hours.4 Refrigerating specimens makes matters worse. However, if glucoses are drawn in fluoride (gray stoppers) they are good for a week.
It’s imperative that if you are going to ship overnight, that you centrifuge chemistry specimens within 2 hours of collection and remove the serum or plasma from contact with the cells. If the tube is a gel tube, the barrier will be adequate for separation and not require further processing. Just remember, not all gel tubes are stable when testing therapeutic drugs. Refer to the limitations, if any, provided by your tube’s manufacturer. Gel barriers must be intact and not allow contact between serum and cells.
If you are shipping aPTTs where testing will not occur within four hours, you must centrifuge, separate, and freeze the plasma before shipping. Unseparated, aPTTs are only stable for four hours at any temperature.
- CLSI. Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays and Molecular Hemostasis Assays; Approved Guideline—Fifth Edition. CLSI Document H21-A5. Wayne, PA: Clinical and Laboratory Standards Institute; 2008.
- Reneke J, Etzell J, Leslie S, Ng V, Gottfried E. Prolonged Prothrombin Time and Activated Partial Throboplastin time due to underfilled specimen tubes with 109mmol/L (3.2% ) citrate anticoagulant. Coag Trans Med 1997;109(6):754–7.
- Castellone D. How to deliver quality results in coagulation laboratory: commonly asked questions. Lab Med 2004;4(35):208–13.
- CLSI. Procedures for the Handling and Processing of Blood Specimens for Common Laboratory Tests; Approved Guideline--Fourth Edition. CLSI Document H18-A4. Wayne, PA: Clinical and Laboratory Standards Institute; 2010.
Seeking Patient Permission and Explaining Risks
Last month we asked readers and visitors to our web site if their facility requires blood collection personnel to ask patients for verbal or written permission to draw their blood. We also asked if they are required to inform patients of the risks of having their blood drawn.
Sixty-three percent of those who responded to the first question said that they themselves are not required to solicit consent from patients in their facilities, but that consent was assumed. Thirty-seven percent work in facilities that do not require the collector to provide consent. Of those who work in facilities that require phlebotomists to solicit patient consent, twenty percent obtain verbal permission while seventeen percent require written permission. Their comments include:
Although it was taught as standard procedure to ask if it is OK to do the blood test, I don’t do it as most patients are regulars anyway. For those that aren’t, surely coming in with a doctor’s request and sitting in the phlebotomy chair is implied consent.
We have one basic consent for the phlebotomy, and then specific consents that are also written for donors/patients to sign depending on the procedure they are having….
(We use) a combined consent form with Privacy Practices, insurance billing, and procedure permission.
We assume that when a patient willingly sits in the chair and offers an arm, they are giving us consent. We do tell them to ask away if they have any questions.
We offer copies of patients’ rights before drawing blood.
While sixty-three percent indicated they are not required to solicit permission, it cannot be assumed permission is not solicited elsewhere in the facility. For example, inpatients and outpatients may be asked to sign a form granting permission when they register at the facility upon arrival.
As for informing patients of the risk of phlebotomy procedures, a full 90 percent indicated they were not required to detail the risks, while ten percent were. Their comments include:
After the bleed, (I) advise on care of site and warnings of too much arm movement… unless they are regulars, eg weekly.
In writing on the donor card, in writing as a separate consent for some procedures and in writing on the provider order form required for some procedures such as therapeutic phlebotomy or autologous blood donation.
We try to educate when patient’s request inappropriate areas such as the underside of the wrist.
…with a new phlebotomy patient who’s never been drawn before, we tell them what to expect and what we will be doing. We still don’t explain the risks unless they ask us.
Whether or not to provide patients with information on the risks of the procedure is largely a matter of risk management, and most often decided after consultation with the facility’s legal counsel. While the risk of nerve injury is rare, when it happens it’s catastrophic for the patient and the facility, especially if legal action is taken. Hematoma formation is the most common complication, occurring in 12 to 17 percent of draws for clinical laboratory testing.1,2 Fainting has been reported to occur in 2.5% of clinical laboratory draws.3 For complications surrounding blood donor draws, bruising has been reported to occur after 9 to 16 percent of donations, while fainting during or after donations occurs in 2.6 percent of adult donors and 8% of the time in donors of high-school age.4 Fainting rates may be as high as 27 percent in first-time donors who weigh between 100-139 pounds.4
- Galena, H. Complications occurring from diagnostic venipuncture. J Family Practice. 1992;34(5):582–4.
- Howanitz P, Cembrowski G, Bachner P. Laboratory Phlebotomy. Arch Pathol Lab Med 1994;115:867–72.
- Vissers D, Matthyssen B, Truijen S, Blommaert S, et al. Fainting and hemolysis during blood sampling in youngsters: prevalence study. Int J Nurs Stud 2008;45(5):760–4.
- Newman B. Vasovagal reaction rates and body weight: findings in high- and low-risk populations. 2004 Transfusion 2004;43(8):1084–8.
This month’s survey question: Three years ago we asked Phlebotomy Today STAT! readers if their facility requires phlebotomists to be certified and, if not, if they paid certified phlebotomists more than non-certified phlebotomists. We’d like to see if times have changed.
Participate in the survey.
Last Month on Facebook
During the month of March, fans and visitors to our Facebook page shared their thoughts on the following topics:
- The average number of draws per hour
- ER Techs drawing blood
- Drawing from children
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What Should We Do?
What Should We Do? gives you the opportunity to ask our team of technical experts for advice on your most pressing phlebotomy challenges. Whether technical or management in nature, we’ll carefully consider solutions and suggestions based on the industry’s best practices so that you and those in other facilities with the same problem can benefit, all the while maintaining your facility’s anonymity. What Should We Do? is your opportunity to ask us for suggestions on the best way to handle your real-life dilemmas.
This Month’s Case Study
Tourniquets and Gloves: the Cost of Infection Control
One reader writes:
We are screening around 2500 applicants per day for infectious diseases namely HIV/HBV/HCV infection. We are just wondering what to do with this huge workload in regard to the practice of changing the gloves and tourniquet with each applicant.
Twenty-five hundred draws per day is an enormous volume for any facility; your expense for single-use supplies must be equally enormous. We understand the need to contain costs by reusing as many supplies as possible. However, the risks involved can easily outweigh the benefit of reusing gloves and tourniquets. Here in the U.S. a new pair of gloves must be used on every patient. Single-use tourniquets, however, are not mandated, but are becoming a wide-spread practice to reduce hospital-acquired and community-acquired infections.
While HIV cannot be acquired from a contaminated tourniquet, the hepatitis B virus can remain infectious on surfaces for up to a week. Although acquiring the infection from a contaminated tourniquet is unlikely, it is conceivable, and you should prevent all modes of transmission, however unlikely. Should a contaminated tourniquet distribute the virus from one patient to another, you could be contributing to the spread of the same infection you’re working hard to eradicate.
We strongly recommend your continued use of single-use gloves, and to consider single-use tourniquets. At the very least, tourniquets should be discarded when visibly soiled and/decontaminated regularly.
Each month, our “What Should We Do?” panel of experts collaborates on a response to one of the many compelling problems submitted by our readers. Panelists include:
Dennis J. Ernst
Got a challenging phlebotomy situation or work-related question?
Email us your submission at WSWD@phlebotomy.com and you just might see it as a future case study. (Names and identifiers will be removed to assure anonymity.)
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