I'm a scuba diver. If I dive before going for lab work, what affects will it have on my blood test?
This is a great question, and one we’ve never been asked! We did some research for you and found scuba diving can affect what’s known as your “hematocrit,” which is the percentage of your blood made up by red blood cells alone. The study showed your hematocrit may be affected to a statistically significant degree, but not clinically significant. That means the change in the percentage would not change your physician’s interpretation of the result. A second study assessed diabetic scuba divers and found their glucoses didn’t change. To our knowledge, that’s all that’s been studied. Of course, it stands to reason that your arterial blood gases would be impacted, and probably the pH as well. Sometimes physicians order venous pH levels, which would be affected by scuba diving as well.
Phlebotomy comes from the root words phleb, which means “vein”, and -otomy, which means “to cut.” Generally speaking, phlebotomy is the term for removing blood from a patient. Even though the root word phleb refers to a vein, the term phlebotomy has evolved to include taking blood from veins (venipuncture), arteries (arterial puncture) and capillaries (capillary or skin puncture). Phlebotomy can refer to drawing blood to perform laboratory testing or for collecting a unit of blood from a donor.
Phlebotomists are those healthcare professionals whose responsibility it is to draw blood samples from patients or units of blood from donors. They specialize in the procedure and it is their main responsibility. Phlebotomists often handle and process blood samples in preparation for laboratory testing as well. Well trained and supervised phlebotomists are acutely aware that the way they draw and process samples can have a dramatic impact on the accuracy of the test results and have perfected every aspect of their technique to minimize their impact on the sample.
In all but a few U.S. states, phlebotomy is not a regulated procedure. Therefore, any healthcare professional can be considered “qualified” to perform the procedure. That’s why it’s important to understand the distinction between “qualified” and “competent.”
Because is it not highly regulated, many employers assign phlebotomy procedures to allied healthcare professionals without properly training them to perform and handle samples properly. For example, nurses are rarely taught how to draw blood samples in nursing programs, but it is within a nurses “scope of practice” to draw blood samples. It is expected for nurses to learn this procedure on the job. Same for physicians.
In some states, law enforcement officers are legally qualified to draw blood alcohol samples from DUI suspects. They are legally qualified, but the extent of training can vary significantly. Finally, most medical assisting school include a phlebotomy component in their training, but the extent of such training varies widely. The same holds true for phlebotomy schools and programs. Where phlebotomy is not regulated, training can be comprehensive or inadequate, depending on the integrity of the program’s administrator.
California has the most comprehensive regulations on phlebotomy training. Phlebotomists are required to undergo 80 hours of classroom and clinical training, successfully pass a certification exam from a state-approved agency, and obtain six continuing education credits every two years to maintain their license. Nevada requires those who draw blood for accredited laboratories to complete an approved training program and become certified as a laboratory assistant by a state-approved agency. Continuing education is required to maintain one’s certification. Louisiana requires all who draw blood to be certified unless under the direct supervision of a nurse, physician, or laboratory technologist. Nurses are exempt from these regulations in each of these states.
It’s important to realize the difference between “qualified” and “competent.” Even where phlebotomy is regulated and those who draw blood samples meet their state’s qualifications, there’s no guarantee the individual is competent or proficient in the procedure. Every healthcare facility is obligated to conduct annual competency assessments on their staff, including those who draw blood samples. Unfortunately, the extent of such competency assessments is up to the employer. Some do an outstanding job of assessing their blood collection staff’s competency while others merely document an assessment was conducted without observing the employee’s performance.
In the U.S. there are up to a dozen agencies claiming to certify phlebotomists; only a few are accredited. Some issue certifications to applicants who merely provide documentation of prior work experience that includes blood collection. No exam is required. Others conduct 2-day weekend classes that culminate with “certification.” While such approaches are merely bogus money-makers for the “agency” and do little to assure competency, those who complete their requirements can technically refer to themselves as certified phlebotomists. Therefore, asking the healthcare professional who is about to draw your blood if he/she is certified doesn’t guarantee competence.
Asking if the individual is certified through an accredited agency may not even assure the individual is competent. At least one fully accredited agency certifies without requiring applicants to have ever drawn a patient.
Even if you live in a state where phlebotomists or laboratory assistants must be certified by law, there’s no guarantee the person drawing your blood is indeed certified. Every state that regulates who can perform the procedure exempts nurses and physicians, professions that do not include phlebotomy in their training programs.
One possible indicator the person drawing your blood might be competent, or at least knowledgeable of the risks of the procedure, is to ask if he/she knows where the nerves are in the bend of the arm, where most blood samples are drawn. If he/she doesn’t respond that they nerves most susceptible to injury during a blood collection procedure is in the inside aspect of the arm (see illustration), it’s likely he/she has not been properly trained. Nobody should be drawing blood if he/she does not know where the nerves pass in the area to be punctured. Such gaps in knowledge eventually lead to nerve damage and permanently disabling injuries.
The procedure should only take a few minutes. After you are identified by the phlebotomist, nurse, or other healthcare professional, you will be asked a few simple questions about your prior experiences or any problems you might have encountered during previous blood draws. The phlebotomist will tighten a tourniquet around your upper arm, and proceed to survey your antecubital area (the bend of your arm) for veins. Depending on how visible your veins are, you may be asked to clench and hold your fist. Do not pump your fist, just clench and hold.
Once a suitable vein has been located, the site will be cleansed, probably with an alcohol pad, and allowed to dry. The device to perform the puncture to your vein will be assembled, and the tubes to be filled selected. The phlebotomist will stretch the skin where he/she intends to insert the needle and warn you when the needle is about to be inserted. you will then feel a small pinch, similar to that of a mosquito bite.
Once the vein has been accessed, the phlebotomist will fill each tube one at a time, mixing each one as soon as it is filled. If a syringe is used, he/she will withdraw as much blood as necessary and fill the tubes after the needle is removed. Before removing the needle, the tourniquet will be released and you will be asked to unclench your fist. The needle will be removed, and a safety feature will be activated on the device that conceals the needle, preventing the healthcare worker from being accidentally stuck.
The phlebotomist will apply pressure to the site with a gauze pad immediately, or ask you to apply direct pressure. You should not be asked to bend your arm up, which goes against the standards and is not an adequate substitute for direct pressure. Bruising may occur and lead to complications. Cotton balls should not be used to apply pressure, as it also goes against the standards for the industry. Cotton fibers could be embedded into the wound as it closes, and cause the wound to reopen when the cotton ball is removed.
The phlebotomist will complete the mixing of the tubes, apply the labels identifying the blood as belonging to you. In some locations, your identification will be hand-written on the tubes. The phlebotomist will then remove the gauze pad and observe the site to assure bleeding has stopped. This observation should not be brief, but should take up to ten seconds. Shorter observations may not be long enough to detect blood leaking from the vein into your tissue, which can lead to a nerve injury
After determining bleeding has stopped from the vein and from the surface of the skin, the site will be bandaged. You will then be shown the labeled tubes and ask to confirm they are labeled correctly. Alternative, if you have an identification band on your wrist, the phlebotomist may simply compare the labeled tubes with your ID band. One of these two confirmatory steps must be conducted. Do not allow the phlebotomist to leave you, or to allow you to leave, without labeling the tubes in your presence and making this final check.
When performed correctly and according to industry standards, venipuncture complications are rare. However, even when properly performed, complications can include fainting, dizziness, bruising at the puncture site (hematoma), nerve injury, and arterial puncture or laceration. If you have ever experienced any of these complications in the past, bring them to the attention of the healthcare professional every time you have your blood drawn.
Statistics show 2.5 percent of patients pass out during or immediately following a blood draw. Those with a history of passing out during a venipuncture procedure should notify the phlebotomist and be made recumbent (lying down) during the procedure. Bruising can be minimized, but not always prevented. When bruising occurs, it is usually minor and only leads to a temporary discoloration of the skin. When significant, especially when the artery has been accidentally punctured or lacerated by the needle, a large hematoma can exert pressure on nerves in the area and lead to a compression nerve injury. Compression nerve injuries typically resolve over time. Only rarely will they develop into Complex Regional Pain Syndrome, which can be permanently disabling.
Your blood samples should be immediately labeled in your presence and mixed by gentle inversion, not sideways tilting. They will then be transported to the laboratory for testing. Some tubes contain additives to prevent clotting while others contain additives that facilitate more complete clotting. Some tubes require centrifugation in order to separate the liquid portion of your blood from the cellular materials (white blood cells, red blood cell, and platelets). That’s because some tests are performed on the liquid portion known as serum (from tubes allowed to clot) or plasma (from tubes containing an additive that prevents clotting). Other tests are performed on whole blood, which refers to samples with clot-prevention additives (anticoagulants) that are not centrifuged, but tested from the entire, well-mixed sample.
Some tests, like bilirubin, require protection from light immediately after collection since light deteriorates what will be measured as the sample is transported and awaiting testing. Others require the sample be immediately placed in an ice slurry since what will be measured deteriorates rapidly at warmer temperatures (e.g., renin and ammonia).
Some tests, like potassium, will change dramatically after two hours if the components of the blood are not separated by centrifugation. The material on the bottom of the tube you saw is a gel that, during centrifugation, positions itself between the layers of cellular material and the liquid portion of your blood (serum or plasma). During centrifugation, the gel barrier moves and positions itself between the liquid and solid components of your blood. The laboratory will use the liquid portion to test your potassium. Without the gel in the tube, the constant contact between the liquid and cellular material will cause potassium to increase in the serum or plasma.
If you’ve ever fainted during or following a blood draw, tell the phlebotomist. The standards require him/her to have you recline during the draw if you have a history of fainting. It’s for your protection. If you’ve had a mastectomy, the phlebotomist need to know as well since your blood should not be taken on the same side without your physician’s permission. If you’ve ever had any complications, such as a severe bruise or nerve injury, you should also notify the person drawing your blood sample. If you have an allergy to latex, notify the phlebotomist as well. Most healthcare facilities avoid using latex tourniquets and bandages, but you should not expect that to be the case in every facility, or that every employee follows facility policy.
Some states allow patients to order their own blood tests, but not all. In those states you can go to a laboratory and tell them you’d like your cholesterol checked, or order any number of tests on your blood. Depending on the state, you may have to provide a physician’s name to which they will send the results. In other states, the results can come to you directly.
After your blood draw, leave the bandage on for at least 20 minutes. Do not lift anything heavy with the same arm from which your blood was taken. Ladies should not carry their purse in the crook of the same arm in which the venipuncture was performed.
If you see excessive bruising, or if you continue to bleed from the venipuncture site after the phlebotomist has left you, apply pressure and notify the laboratory or your immediate caregiver. If you have any questions about your draw or notice anything unusual, contact the laboratory or the caregiver/facility who performed the procedure.
Unless you ordered the blood tests yourself and live in a state in which citizens can receive their results directly, your lab results will be sent to your physician electronically. If you are an inpatient, your results will be added to your medical record as soon as they are released by the laboratory for your nurse and/or physician to evaluate. Most routine lab work is complete in a matter of hours. If your blood was drawn in a location remote to the laboratory, transit times may delay the posting or transmission of results for a day or more.
Sometimes the pressure exerted within the vein to withdraw the blood is excessive, resulting in the uppermost interior wall of the vein to be pulled onto the narrow, beveled opening of the needle. This can be the result of a needle not positioned in the center of the vein, using a needle too large for the vein, or a vein that is delicate, narrow or fragile. When veins collapse, the flow of blood is interrupted and may have to be terminated and repeated.
Some veins move out of the way when the needle is inserted into the skin, and are referred to as rolling veins. Veins roll when the phlebotomist doesn’t anchor the vein properly, and is not the fault of the patient. Although patients are often faulted by those drawing blood unsuccessfully for having rolling veins, it is rarely the fault of the patient.
Phlebotomists have a wide variety of tools at their disposal to make every draw successful. Most veins can be accessed with a tube holder adapter, which allows each tube to be filled directly from the vein. Some veins require a syringe to be used, while others require what’s known as a butterfly set. You should trust your phlebotomist to use the most appropriate device for the unique features of your veins. You can suggest a particular device, but the final decision should be up to the person drawing your sample.
Some phlebotomists are more proficient with and comfortable using one device over another. Many patients feel a butterfly set is the only device that can be used successfully on them based on prior experiences or the comments of other healthcare professionals who have drawn their blood. The device a phlebotomist uses is selected for a wide variety of reasons. His/her level of comfort with the device, the condition of your veins (size, stability, fragility, location, etc.), the volume of blood required, and other factors all must be considered in addition to your preference. Since the phlebotomist is the professional who knows most about the procedure and equipment and what device would most likely lead to success on the first attempt, he/she should have the final say.
Keep in mind, butterfly sets are exceedingly expensive to the facility, and are associated with a vastly higher rate of accidental needlesticks for healthcare workers than some other devices. Before you request a butterfly set, be aware of these ramifications before insisting the healthcare worker use them when they may not be necessary.
Your input on where others have been most successful in finding your veins is always welcome, but be careful not to insist where the needle must be inserted. Your phlebotomist selects your vein based on a lot of variables. She has to feel confident the vein 1) can be safely accessed on the first attempt, 2) be the least painful to you, 3) is in keeping with the standards in the industry regarding vein selection and 4) does not violate the facility’s policy for acceptable veins. She knows some veins in the bend of the arm are more painful to puncture than others, and are closer to arteries and nerves than others. The standards require all who draw blood to survey all available veins in your arms before making the selection and choose the one least likely to lead to complications. That means your choice of veins may not be the vein from which she has to draw from in order to be compliant with what the standards and her facility policy requires. While patient input is important, patients should be careful not to insist the phlebotomist select a vein that means violating the standards or facility policy.
Being needle-phobic is not something to be ashamed of. Up to 20% of the population is predisposed to needle phobia. A good phlebotomist will invest the time necessary in getting you through the procedure with the least amount of emotional trauma as possible. If you encounter a less-than-patient phlebotomist, request another phlebotomist or the immediate supervisor.
Studies show applying an ice compress to the site to be drawn is an effective means of minimizing the anxiety of the procedure. So does positioning the patient in a recumbent or reclining position. Distraction has also been found to be effective. Nothing, however, is more effective than genuine and sincere compassion. If you are needle-phobic, reach out to the laboratory or clinic where your blood will be drawn in advance and ask that the phlebotomist most successful and proficient with needle-phobic patients be available when you come in, or schedule your visit around that person’s schedule.
Most lab orders are filled by drawing blood from a vein, not from the capillaries of your finger. That’s because most patients present with orders for multiple tests, which require more blood than what can be obtained by a finger puncture. Fingersticks by nature can easily be contaminated by tissue fluids from the trauma of the puncture device piercing the flesh, and from the squeezing of the finger often required to obtain enough capillary blood for the test.
Additionally, venous blood is considered to be the gold standard for blood samples because they represent the entire volume of circulating blood. So even when only one test is ordered, a venous sample is considered the type of sample that can best represent the patient’s actual condition.
Finally, when the laboratory reports the test results to the physician on your blood, the report contains the “normal” or “reference” ranges for each test. These ranges were likely reached by testing the venous samples from healthy patients, not capillary samples. For many tests, the normal results can be significantly different.
There are lots of reasons your blood draw may be successful one time and difficult the next. It may be variables unique to you that are different between visits, or the skill sets between different phlebotomists.
If you were significantly more dehydrated on the unsuccessful draw than the successful draw, that would be enough to make a difference. Your veins could also be harder to find if you or the weather were significantly colder during the unsuccessful draw than the successful event.
If your unsuccessful draw was at the hands of someone with lesser experience or expertise, it’s obvious why it could have been trying for you both. Even if it were the same phlebotomist on both attempts, people can have an “off” day when even the easiest veins play hide-and-seek.
Every patient should be asked to state his/her full name and spell at least his/her last name. Asking you to affirm the name the phlebotomist states is not the proper way to identify the patient. The tubes should always be labeled in your presence, not after you leave. You should also be asked to look at the tubes after they are labeled to confirm they are labeled with your name, and the information on the label is correct. If you are wearing an ID bracelet, the phlebotomist is permitted by the standards to compare the labeled tube with your ID band. The standards don’t require outpatients to have ID bands, but if you do, you should make sure your ID band is correct in all regards. All inpatients are required to have ID bands affixed to them before any procedure, including phlebotomy. Healthcare professionals are not permitted to trust ID bands that are attached to the foot of the bed, on the bed rail or anywhere other than their person.
When your doctor orders fasting lab work, it’s because a recently consumed meal or snack will lead to significant changes in the test result. Fasting is generally defined as a complete overnight dietary restriction of everything except water and medications for 10-12 hours. For lipids like cholesterol and triglycerides, studies show a daytime fast is acceptable. But for glucose, it must be overnight.
As for coffee and tea, physicians often allow patients this luxury as a gesture of compassion. Studies are inconclusive as to whether or not their consumption affects fasting lipid levels. Some studies show significant changes, some show none. The most important thing you can do as a patient is to apply the same fasting conditions every time you have the same fasting test drawn.
No. Pumping the fist significantly elevates your ionized calcium and potassium level temporarily. Potassium is one of the most common laboratory tests ordered by physicians, and is often included in metabolic panels, electrolyte panels, and basic metabolic profiles.
If your potassium is dangerously low and you are asked to pump your fist by the phlebotomist to make your veins easier to find, you could easily double the test result. When the physician receives a normal result for your potassium level from the lab, you won’t get the critical attention you need. If you are going to surgery, you could have a seizure or heart attack during surgery. Conversely, if your potassium is normal and you are told to pump your fist, your physician will be misled into thinking you have a high potassium level and treat you for a serious condition you don’t have.
If you are not being tested for ionized calcium or potassium, or panels that include them, you should still not pump your fist. Physicians often call the laboratory after blood has been collected to add on additional tests to the sample drawn earlier. If a panel that includes potassium or ionized calcium is added, there’s no way it will be accurate. However, the person testing the sample will have no idea you were asked to pump your fist during the draw. So don’t pump your fist. Clenching and holding your fist is fine, and not known to alter test results.
The American Society for Clinical Laboratory Sciences has an excellent site managed by its members to respond to consumer questions on laboratory work. Lab Tests Online has answered questions on laboratory testing since 2001, serving over 100 million inquiries from consumers like you. These are the same people who test blood samples every day. Trust their answers are the most reliable in the industry.
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