Hemoconcentration: Big word, big problem
Hemoconcentration. It's a mouthful. But utter the word in some of your professional circles and you're likely to win newfound respect for what you know about collecting blood. (See this month's Tip of the Month below.) But you have to know what you're talking about. This article will help you understand what hemoconcentration is and how it can affect test results.
If "hemo" means blood, hemoconcentration is an abnormally high concentration of blood. Blood becomes concentrated, or thickens, when the proportion of cells and other larger elements of the blood increases to such a degree that it no longer reflects the patient's actual health status. Since most of the objective information physicians receive about the well-being of their patients come from laboratory test results, it is critical that specimen collection personnel recognize and prevent situations that lead to hemoconcentration. During phlebotomy, blood can be concentrated several ways. Patient posture, prolonged tourniquet application, and fist pumping.
The physiology of the blood changes when a patient goes from lying down to upright. Here's why:
When a person goes from lying down to sitting or standing, the body senses the change in orientation. It knows it's going to have to do something to keep the brain supplied with blood now that it is "uphill" from the heart. The body---being the marvelous machine it is---responds by releasing hormones into the bloodstream that increase the blood pressure. When blood pressure increases, the brain is continually supplied with oxygenated red blood cells, keeping the patient conscious. However, there's a downside to posture-related changes in blood pressure every phlebotomist must know. The blood circulating throughout the now-upright body becomes instantly hemoconcentrated. That's because when the body senses the circulatory overload from the rise in blood pressure, the capillaries become porous so water and smaller compounds migrate into the tissue. Think of it as a natural "venting" of the circulatory system when it gets the least bit pressurized. What's important for those who draw blood samples to know is that this natural attempt to lower the blood pressure also results in a temporary state of hemoconcentration in the vein you're about to draw blood from.
Think of the sudden porosity of the capillary beds to be like a fishnet, trapping only the larger blood components in the veins. Not only do red blood cells and other cells remain in the circulatory system in a higher concentration temporarily, but so do large substances like proteins and compounds attached to protein that can't pass through the capillary walls because of their molecular size. As a result, they too remain in the bloodstream in temporarily higher concentrations than that in which they existed before the posture change.
Drawing specimens during this change will more than likely lead the laboratory to report a higher test result than if the patient were drawn while recumbent. (1-6) Conversely, when a patient goes from upright to recumbent, the blood is subject to a dilutional effect due to water moving from the tissue into the circulation. It has been reported that cholesterol levels are 10 percent lower and triglycerides 12 percent lower in patients drawn after being recumbent for 5 minutes.(1) Those analytes affected by changes in posture are listed here:(1,7)
Not all of these analytes change to a clinically significant degree. Generally, the change ranges between 5-15 percent.(1) However, all collectors must be aware of the test requirements that specify the patient be recumbent before collection and draw posture-sensitive analytes appropriately. Such requirements are because the effect of hemoconcentration are significant.
Prolonged Tourniquet Application
Hemoconcentration also affects test results when a tourniquet is left on longer than one minute in the same way in which analytes are affected by posture changes. Therefore, when it takes longer than one minute to find and access a vein, hemoconcentration begins affecting test results. That's why CLSI recommends tourniquets be left on no longer than one minute.(8)
It can be difficult to minimize the time a tourniquet is in place when patients' veins are difficult to find. Nevertheless, specimen collection personnel shouldn't rush the vein selection process. Should the survey take more than one minute, CLSI recommends releasing the tourniquet prior to puncture for at least two minutes so that the blood below the tourniquet can equilibrate and hemoconcentration can disperse.
Before releasing the tourniquet, make a mental note of where the vein lies in relation to certain skin "markers" (e.g., freckles, skin creases, contour of the skin, etc.). This can shorten the time it takes to relocate the vein and allow compliance with the one-minute rule.
According to the standards, the tourniquet should be released as soon as the vein is accessed to minimize the effects of hemoconcentration.(8) However, in reality, releasing constriction may interrupt the flow of blood prematurely. Therefore, if the collector feels completing the collection is at risk, he/she should perform the procedure according to what is thought to be best for the patient. It is appropriate to realize not all situations allow for compliance, but knowing the effects of excessive tourniquet time requires the release of the tourniquet upon venous access whenever so doing does not jeopardize the collection.
Patients who pump the fist to assist the collector in finding a suitable vein contribute to inaccurate test results. When the muscles are exercised during the constriction of a tourniquet, hemoconcentration results. Studies have been conducted on the effects of fist pumping on potassium and ionized calcium and found them to both be elevated in the arm being used.(1,7-9)
Therefore, collectors should discourage this habit in their patients. Additionally, it is prudent to inform them of the potential for the practice to alter their results. This may serve to prevent them from repeating the behavior in the future.
Google "hemoconcentration" and you'll come up with about 202,000 hits. Induce it in your patients and your lab is likely to come up with an inaccurate test result. That's because it is impossible for those who test specimens to know when a specimen is affected by hemoconcentration. When not prevented, it will likely manifest itself as inaccurate results that lead to patient mismanagement. Because physicians rely on laboratory tests heavily to guide their diagnosis, medication and management of the patient, those who draw specimens play a critical role in the proper care of every patient they draw. When hemoconcentration is understood and its causes prevented, specimen collection personnel are more likely to submit specimens to the clinical laboratory that can produce an accurate assessment of the patient's condition.
1. Narayanan S. The preanalytic phase an important component of laboratory testing. Am J Clin Pathol. 2000;113:429-452.
2. Ernst D, Ernst C. Lab Draw Answer Book. Corydon, IN: Center for Phlebotomy Education; 2017.
3. Ernst D. Applied Phlebotomy. Lippincott Williams & Wilkins. Philadelphia, PA. 2005.
4. Becan-McBride K, Garza D. Phlebotomy Handbook. Upper Saddle River, NJ: Pearson; 2014.
5. Sommer S, Warekois R. Phlebotomy Worktext and Procedures Manual. Philadelphia, PA: WB Saunders;2002.
6. McCall R, Tankersley C. Phlebotomy Essentials, Philadelphia, PA: Lippincott Williams & Wilkins; 2015.
7. Dale J. Preanalytic Variables in Laboratory Testing. Lab Med.1998;29:540-545.
8. CLSI. Collection of Diagnostic Venous Blood Specimens. Approved Standard, GP41-A7, Wayne, PA, 2017.
9. Baer D, Ernst D, Willeford S, Gambino R. Investigating elevated potassium values. MLO. 2006;38(11):24-31.
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What Should We Do?: Fasting
Dear Center for Phlebotomy Education:
Providers in our clinics have approved an 8-hour fast as sufficient for glucose, lipids and Hemoglobin A1C. I've always heard a 12-hour fast is optimal. Also, the question has come up about whether we should inquire the fasting status of every patient we draw for panels that include glucose or lipids even if they weren't ordered as fasting panels. That seems excessive to me. What should we do?
Generally, a fast is defined as a 10- to 12-hour dietary restriction of everything except water and medications. For lipids, a daytime fast is considered acceptable but for glucose it must be overnight.
Some facilities strictly enforce a 12-hour fast for lipids while others relax it to 8-12 hours. However, over the last several years there have been discussions in cardiovascular circles as to whether fasting for lipids is even necessary. So the waters are getting kind of murky right now. Until science sorts things out, your medical staff should establish the parameters they feel most comfortable with.
For diabetes testing, however, most facilities consider a 10-12 hour overnight fast to be optimal. It would not be unacceptable for your facility to establish an 8-hour fasting policy. One study, published in 2011, suggested a 3-hour fast would be acceptable for glucose. Since it must be an overnight fast, though, and since most people sleep 8 hours, an 8- to 10-hour fast should not be too burdensome to impose.
We like the idea of documenting every patient's fasting status when lipids or glucoses are ordered. Though it's not required by the standards, the more information the physician has the better he/she can interpret the results.
Got a challenging phlebotomy situation or work-related question? Email us your submission at WSWDpanel@phlebotomy.com and you just might see it as a future case study. (Names and identifiers will be removed to assure anonymity.)
Product Spotlight: Join Phlebotomy Central
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- To The Point Volumes 1-7--- a compilation of our To The Point downloads into booklets worth $370 if purchased separately.
- The Manager's Toolbox – a growing list of documents, competency checklists, SmartCharts™, and procedure templates that managers and educators can use to enhance their understanding of preanalytical processes and manage their staff more effectively;
- FAQs – Exclusive to Phlebotomy Central members, answers to hundreds of the most frequently asked questions, searchable by keyword or phrase.
It's often been said the next best thing to knowing a fact is knowing where to find it. You'll find it in Phlebotomy Central.
Test Talk: Hemoglobin A1C
A new column that features a different laboratory test each month, what it measures, why physicians order it, and any collection handling restrictions and requirements that must be met.
Hemoglobin A1c, also known as glycohemoglobin or glycosylated hemoglobin, is increasingly used to assess and diagnose diabetes. Physicians use it as a reflection of the average amount of glucose in the blood over the last several months. Hence, fasting is not required prior to collection.
The predominant form of hemoglobin within red blood cells is hemoglobin A. As glucose circulates, it spontaneously binds to hemoglobin A making it glycohemoglobin, or glycosylated hemoglobin. The glucose that attaches remains bound for the life of the red blood cell. Therefore, the higher the level of glucose in the blood, the more glycosylated hemoglobin exists in the red blood cells. The predominant form of glycosylated hemoglobin is A1c.
Not only is hemoglobin A1c used to screen for and diagnose diabetes, it's also used to monitor treatment for those with diabetes. Nondiabetics typically have levels below 5.7% (39 mmol/mol). Those with diabetes have levels of 6.5% (48 mmol/mol) or above. Diabetics with levels below 7% are considered to have their glucose under control. Nondiabetics with hemoglobin A1c levels between 5.7% and 6.4% (39-46 mmol/mol) are thought to have a higher risk of developing diabetes in the future.
Physicians and newly diagnosed diabetics alike use hemoglobin A1c levels to get a sense for how elevated glucose levels have been over the last several months. Until control is established, physicians may order the assay several times, then at least twice a year thereafter to verify that control is maintained.
Hemoglobin A1C is collected into heparinized tubes (green closure) and tested as whole blood. If testing is to be delayed, the sample should be stored refrigerated. The analyte is stable for three days at room temperature, and at least one week under refrigeration. 1,2
Test results may be falsely low in patients with anemia or whose samples are hemolyzed. Patients who are iron-deficient have falsely elevated hemoglobin A1c levels. Results from recently transfused patients or those undergoing erythropoietin therapy may not be reliable.
1. Young D. Effects of Preanalytical Variables on Clinical Laboratory Tests. AACC Press. Washington, DC. 2007.
2. Rohlfing C, Hanson S, Tennill A, Little R. Effects of whole blood storage on hemoglobin a1c measurements with five current assay methods. Diabetes Technol Ther. 2012;14(3):271-5.
From the Editor's Desk
After being sick for seven days with my annual respiratory crud that seems to find me no matter where I live, I finally broke down and went to the doctor. Mind you, I don't have a doctor since I've only lived in Michigan for a year now, but was able to find an local practitioner who took me as a walk-in. I think there was something predestined in my timing.
After checking in, I sat down and waited my turn. Since waiting rooms are perfect opportunities to be productive, I brought along a hard copy of the CLSI skin puncture standard currently under revision in preparation for a gathering of the committee in a few weeks. I was well into it when a gentleman walked in and asked if he could have some fasting labs drawn in advance of an appointment he had on Monday. They turned him away saying they don't have anyone to draw blood on Saturdays, and asked if he could come back on Monday.
To just sit there and let him be turned away was more than I could stand, but I also knew what an oddity I would have made of myself to the desk clerk and other patients if I were to stand up and offer to draw his blood for them. I went back to my work on GP42. The gentleman went out to the entrance foyer and placed a phone call, then returned to the desk.
"I have to work Monday and my appointment is right after I get off," he said. "I don't think I can come back before then." They suggested he drive to another outpatient clinic a half-hour away where a phlebotomist was on staff.
I was called into an exam room and greeted by "Mary" who took my vitals and recorded my symptoms for the doctor in advance. She was a pleasant gal and probably a medical assistant, but I don't know that for sure.
"The doctor will be right in," she said, then opened the door to leave. About that time I heard someone say "Mary, you have a lab draw to do."
"Ugh!" Mary grunted in disgust.
I felt sorry for the poor man who was about to be stuck by someone who had such a reaction. Even more so if he, too, overheard her reaction.
I now am on the requisite antibiotics and feel much better. But Saturday's encounter became an immediate calling for me. If I'm going to live in this community, I need to share what I know to improve the quality of health here. For me, that means improving the availability of lab draws to those who need them and the confidence of those tasked with performing them, especially since I'll be one of their patients.
I don't need another job, nor do I want to spend my Saturdays drawing blood in a clinic. But this much I know for certain: I was brought to live in this area for a reason, a purpose for which I knew not when we chose this community 16 months ago over all the other ones we considered from Maine to Montana. Over the last year, that purpose is slowly being revealed in multiples. I'll be going back in March for my new-patient appointment and will offer my service to the physician, then let things unfold as they may... or may not. I'm not invested in the outcome either way.
The only outcome I care about is that I'm doing that which I was brought here to do. Discovering just what that is is making this a very interesting time of life. I'll keep you posted.
Dennis J. Ernst, editor
2019 Global Summit Location Announced
Greiner Bio-One has just announced the date and location of the 2019 Global Summit on Best Practices in Preanalytics. The event will be held at the Mirage in Las Vegas, Nevada from October 7-10.
The high-powered event, which set a new attendance record last year, will include a world-class faculty and three days of management and technical topics covering a broad spectrum of preanalytic interests. Attendees who stay at the Mirage will receive a discounted room rate of $136 per night. Early registrations are being taken at the early bird rate of $449 through August 1st.
Attendees at the 2018 event in Charlotte raved about the presentations and the caliber of the event. Read their testimonials.
Register for the 2019 event.
Advice From the OSHA Expert: Making training fun
[Editors' Note: We're pleased to welcome safety expert and columnist, Dan Scungio, MT (ASCP), SLS, also known as "Dan the Lab Safety Man" as our newest contributor.]
Throughout this year I'll be writing about various safety topics related to phlebotomy and the laboratory. The articles are not meant to present "read it and forget it" topics, but often that happens with safety. For a safety culture to survive and thrive in your workplace, safety training and awareness must be in the spotlight throughout the year. If this is not what happens in your place of employment, you can help make a difference.
If you are not a leader, you can still be a leader in your area for safety. Make safety posters to hang up, and change them monthly. Send out weekly safety e-mails. Take five minutes to discuss a safety topic at staff meetings. In my opinion, there are enough safety topics that you could discuss a different one every day. Do you need ideas? Consider highlighting certain safety topics during specific months:
February---Hoods and environmental issues
March---Personal protective equipment
August---Safe work practices
If some of these topics do not apply to your area, substitute one. For example, if you do not have compressed gases, spend a month discussing needle safety. There are plenty of other phlebotomy-specific topics ranging from aggressive patients to OSHA violations. Remember, you need to repeat these topics from time to time for the purpose of continued awareness, but you need to do it differently each time to keep your staff interested and educated.
Play games, create quizzes, or conduct safety scavenger hunts. Toss a ball to people and have them answer safety questions for prizes. Remember to consider the ages and background of your staff. That can make a difference in how you present safety information. However you decide to promote and maintain safety, be sure to make it fun!
You can contact Dan Scungio, "Dan the Lab Safety Man" at firstname.lastname@example.org
The Empowered Healthcare Manager
Every month we run an excerpt from our editor's popular blog, The Empowered Healthcare Manager.
Branding Employees Versus Behaviors
Which sounds worse:
He stole some supplies.
He's a thief.
She talked about someone behind his back.
She's a gossip..
She lied to her boss.
She's a liar.
One brands the behavior, the other brands the person. One incident of pilfering, gossiping, or lying doesn't make a person a thief, gossip or liar. Only habitual behavior can do that. Even then, applying the brand to the person serves no purpose for the empowered manager. Person-branding must be self-inflicted.
Branding the behavior instead of the person is the first step to nurturing a life-long employee. After calling out the behavior for what it is, those who choose to defy corrective measures brand themselves, effectively calling an end to the working relationship.
Empowering the employee always empowers the manager.
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Tip of the Month: Talk the Talk
Click here for this month's featured Tip of the Month from our rich library of archived Tips.