Phlebotomy Basics For Nurses
Submitted by Mary H. Nielson, DNP, APRN-BC
Phlebotomy is the process where a puncture is made in the vein to remove blood or infuse fluids such as saline. As nurses we are very familiar with the process of inducing fluids, however, we are not so familiar with the process of removing blood. At some point in your nursing career, if you have not already done so, you may have to obtain blood specimens from your patients. The purpose of this article is to give an overview on the basics of blood drawing, such as the process of blood drawing with regards to patient safety, general information regarding blood specimen tubes and finally an overview of common lab panels.
Blood drawing technique:
Your institutions should have policies and procedures regarding phlebotomy for nursing, including training classes on the proper procedures for blood draw, you should review these procedures prior to performing any blood draws. Some basic concepts regarding blood draw are: the need to gather all of your equipment before starting the procedure, and in doing so keeping in mind not to create waste or unnecessary use of supplies. Items you would need for a venipuncture are: a tube holder commonly called a vacutainer, a vacuum collection needle, alcohol pads, tourniquet, 2 X 2 gauze, a band aid, all the blood tubes you may need and patient labels. If you are drawing blood off an existing IV line, you will need an alcohol pad or appropriate cleansing agent for the port, a tube holder, a tourniquet, a needleless vacuum collection device, appropriate blood tubes, patient labels and a saline flush. The longer the IV site has been in place, the more difficult it may be to obtain a blood sample. Most IV saline locks stay in place for up to 72 hours. After 72 hours there is a higher risk of infections, such as phlebitis. After the saline lock has been in for 24 hours, obtaining blood from another source would be recommended. If drawing blood from a peripherally inserted central catheter (PICC) line or central line, you will need an alcohol pad or appropriate cleansing agent for the port, a tube holder, a needleless vacuum collection device, appropriate blood tubes including a waste tube, patient labels and saline flushes for each port. Follow your institutions policy and procedures on how to obtain blood samples from an IV line, PICC line or central line.
The basic step procedure includes:
- Wash your hands
- Gather all your equipment
- Bring equipment to patient bedside
- Wash your hands and don your gloves
- Verify patient with arm band, orders, and labels for blood tubes
- Explain the procedure to the patient
- Prepare your equipment (follow your institution policy)
- Draw the blood test in the proper order and proper blood tube (per your institution policy)
- Label each tube verifying against patients arm band
- Finish the procedure by cleaning the patients area
- Dispose of waste appropriately
- Place tubes in a biohazard bag – doff gloves
- Wash hands
- Send the blood to the lab, including requisition if necessary.
Patient safety - Proper Specimen Labeling
Patient safety must be a priority when drawing your patients’ blood. Ensuring that you use 2 patient identifiers for obtaining and labeling blood specimens must be done at all times. It may seem like an over redundant task, especially when you have become familiar with your patients, but mislabeling specimens can result in improper treatment and care for your patient. The Joint Commission’s Hospital National Patient Safety Goals require that you use two patient identifiers when providing care, treatment and services (The Joint Commission, 2013). The process may seem basic but to review, you need to have two physical forms of ID to identify the patient, the most commonly used are the patients arm band and the patient’s labels and/or orders. In an outpatient setting the patient can verbally verify who they are using name and date of birth, however if the capability to provide an arm band is available then the patient should receive an armband. Secondly, your data points of identification need to include the clients name, and a number identifier, such as medical record number, account number, date of birth or social security number. Most institutions have policy’s regarding patient identification with two forms of identification. Follow your hospital policy on two patient identifiers procedures.
Date and time of specimen collection and collector’s initials, need to be written on the patient label that will go on the sample, especially if you are drawing a specimen for type and screen and type and cross for possible blood transfusion. The specimen requisition form needs to include the same patient identifier information as the labels on the blood specimen. If you work in an outpatient setting where you send the blood to another lab, then the following information should be included on the requisition form: diagnosis, insurance information if necessary, patient location, ordering practitioner (MD, APRN, PA), the test to be performed as well as time of draw start and finish if it is a time sensitive test.
Basic specimen tube information:
The following includes the basic information regarding phlebotomy tubes that are commonly used. Understanding the purpose and use of each phlebotomy tube, is essential in understanding the process of phlebotomy. All phlebotomy tubes have a specific color top and each color tube top corresponds to specific test to be drawn. Also each tube may have a specific process that needs to be considered at the time of the draw, such as inverting the tube or placing the tube on ice. The following is a list of commonly used blood specimen tubes, and they are listed in the order that they should be obtained. However, your institutions policy regarding tube order collection may be slightly different, so follow your institutions policies.
- Yellow tubes: Usually for blood cultures, these tubes needs to be drawn first and should be inverted 8-10 times after draw.
- Red tubes (Serum tubes): A serum tube is usually used for odd testing such as drug levels. Drawn first if blood cultures are not required, there is no need to invert these tubes.
- Blue tubes: This tube contains a Citrate additive with a 9:1 ratio, it is used to run clotting test. Due to the citrate additive it is so important to fill the tube to the proper amount, usually marked by a blue line on the tube. The laboratory cannot run or report the test results if the ratio of the citrate additive and the blood is out of proportion, as it this will result in an invalid test. These tests usually need to be run within 4 hours of collection. This test is the third test to be drawn and should be inverted 3-4 times.
- Tiger tops/Gold tubes: These are at times referred to as SST’s (Standard serum tubes), and are used for a wide variety of testing, such as chemistry profiles (CMP, BMP), Creatine phosphokinase test (CPK), C-reactive protein and thyroid studies, they should be inverted 5 times.
- Dark green tubes: Contains sodium heparin, and is used for stat chemistries, at some institutions, these are not commonly used
- Mint green tubes: Contains lithium heparin, which is a gel separator tube that contains a clot activator to make a barrier. Testing that maybe included in these tubes would include a Creatine phosphokinase Myoglobin (CPK MB) and triponan. They would follow the standard serum tubes in the draw order, and need to be inverted 8-10 times.
- Lavender (purple) tubes: Has the additive EDTA, which binds calcium to prevent the blood from coagulating. It is used for Complete blood count (CBC), B-type Natriuretic Peptide (BNP), Erythrocyte Sedimentation Rate (ESR) and a glycated hemoglobin (HA1C). This tube is usually the last tube drawn for most cases, and needs to be inverted 8-10 times.
Uncommon phlebotomy tubes
- Gray tubes: This tube contains Sodium fluoride and Potassium oxalate, an enzyme inhibitor that is used to measure ammonia levels and alcohol levels. This tube must be put on ice immediately and needs to be inverted 8-10 times.
- White tubes: Contains a plasma separator and is commonly used for polymerase chain reaction (PCR) assays, this tube needs to be inverted 8-10 times.
- Royal Blue tubes: Used to test for heavy metals, may contain EDTA or heparin.
In review if you are to drawing a CBC, CMP and PT/INR for your patient, you would draw a blue tube first (PT/INR), followed by a tiger or gold top (CMP), followed by lavender top (CMP). Always ensure you will fill each blood tube and collect specimen per your institutional policy and procedure, and do not hesitate to contact your laboratory for questions. If you specimen is not going to strait to the laboratory for testing, ensure that you refrigerate you sample. Never freeze your blood samples unless specifically directed to do so by the laboratory performing the test.
Review of labs:
Dynamics of the inpatient setting dictate that laboratory test are drawn on the changing patient’s needs. In an emergency department, outpatient clinic, private practice office or extended care facility general screening panels are the most common tests ordered. These are to identity the patient’s base line as well as identify any outlying conditions that may need to be addressed. The normal ranges for your blood test will be reported out with your results for comparison. The following is a list of general laboratory screening test including and specifics regarding the phlebotomy tube:
CBC (complete blood cell count)
A CBC is an overview of your red and white blood cells. The CBC may or may not have a differential ordered. The differential is the cellular component breakdown of the WBC, and can be ordered as a manual or auto count. In a manual differential, the cells are manually counted by a certified lab technician; an auto differential means that the cells are counted by machine.
BMP or CMP (basic metabolic profile/complete metabolic profile)
These two tests have a variety of aliases such as chemistry’s, chem 7, chem 12. In general a BMP will include: Sodium (Na), Chloride (Cl), Potassium (K), Glucose, Blood Urea nitrogen (BUN), Creatinine (CR) and a Carbon dioxide (CO). A CMP includes other test such as Calcium, Albumin, Phosphatase Alkaline, Protein total, transferase, alanine amino (ALT or SGPT) and a transferase aspartate amino (AST or SGOT). The ALT and AST are used to assess liver function.
A lipid profile will assess a patients cholesterol status, these test include total cholesterol, Low density lipoprotein (LDL), High density lipoprotein ( HDL), LDL ratio and triglycerides.
When assessing for cardiac function some of the standard test are Creatine phosphokinase (CPK), CPK–MB, troponin, B-type Natriuretic Peptide (BNP). The CPK measures the Lactate dehydrogenase (LDH), of muscle death. An elevated CPK can be seen with muscle damage such as with motor Vehicle accident. The CPKMB is a specific isoenzyme for the cardiac muscle, but it is also found in skeletal muscle, and is used if the initial troponin level is abnormal (Mayo Clinic Laboratories, 2014). CPKMB usually correlates a positive result within 5 hours from first appearance of symptoms. Troponin is another lab test that is more specific to assess acute myocardial infarctions. Troponin is an enzyme that is released after cardiac muscle death, therefore more specific for actual acute myocardial infarction (AMI). A troponin level will show positive results within 12 hours of an AMI (Jaffe, Ravkilde, Robers, Naslund, Apple, Galvani, Katus, 2000). The one important factor to remember regarding troponin is that it may be elevated while other cardiac enzyme markers remain negative as in a case of unstable angina (Mayo clinic Laboratories, 2014). These lab tests are generally the standard test for heart muscle death, AMI, congested heart failure (CHF), and angina. It is important to remember that there is a time laps before the tests actually show a positive sign of elevation. The normal values of these results are CPK 52-336 u/liter. A normal CPK-MB is < 6.2 ng/ml. The normal value of a troponin result is < 0.10ng/ml,
A B-type Natriuretic Peptide (BNP) is a test used to help differentiate heart failure. Other than the subjective and objective data related to heart failure a BNP test if a definitive test for heart failure. It aids in identifying heart failure in an emergency setting but it also work as a good indicator of the severity of heart failure, as well as response to treatment (Mayo Clinic Laboratory, 2014). The normal value of a BNP result is < 200 pg/ml.
A C-reactive protein is a serum protein marker used to indicate acute inflammation. This test is often used to identify arthritis and rheumatoid arthritis. However, there may not be an elevation even with clinical signs of a flare up (Mayo clinic laboratory, 2014). A C-reactive protein is also being used to help identify AMI or AMI with Coronary artery disease (CAD), however this test is not recommended for the general population (Mayo clinic laboratory, 2014). The normal value for the C-reactive protein is < 5mg/liter, however, you would need to look at you institutions special reports for cardiac values.
An ESR (sedimentation rate) also test for inflammation, and is a good base line test when screening for auto immune diseases. This test take one hour to run, and not very effective in an emergency setting (Mayo clinic laboratory, 2014). Normal ranges are 1-13 mm/hr for male and 1-20 mm/hr for female.
There are several specific tests to monitor a patient’s endocrine system. A few of the most commonly seen are the Thyroid Stimulating Hormone (TSH), glucose level and Hemoglobin Adult 1C type test (HA1C). The TSH with Free T4 will measure a patient’s thyroid function. A TSH measures the specific thyroid stimulating hormone, while the Free T4 will give a good index of the overall thyroid function. Normal ranges for TSH is 0.3-5.0 mIU/L while normal ranges for Free T 4 are 5.0-12.5 ug/dl.
To monitor a patient for diabetes or pre diabetic state, you would check a fasting glucose which should be below 99 mg/dl. A hemoglobin A1C (HA1C) is also checked. This test give an over view of what the average blood glucose level in a person was for the last 3 months. It will not identify highs and lows of a person average blood sugar, but it will give the average. As well as the daily finger stick testing, an HA1C should be done on diabetic patients approximately every three months, and lab test will be reported out with the HA1C along with a corresponding glucose levels range.
Kidney function are measured by the BUN and Creatinine, the Glomular filtration rate (GFR), and can also be measured by a Cystatin C level. The cysteine C is a test that measures a protein inhibitor used to identify kidney function and correlates to the kidneys glomular filtration rate. High values indicate a low GFR and low values indicates high GFR. The Cystatin C is not affected by infection or inflammation, so it is a more reliable marker used to assess kidney function, especially in the elderly and malnourished. The normal ranges are 0.59-0.91 mg/L.
Finally, there are basic cancer markers used to cancer screening. Two of the most common are the CEA and PSA. The CEA (carcinoembryonic antigen serum) is a general screening test for patients who may have or be at risk for colorectal cancer, breast cancer, gastrointestinal tract, liver, lung and ovarian cancers. Normal CEA ranges are < 3 ng/mL, any value grater than 20 ng/ml is strongly suggestive of cancer. The PSA (prostate specific antigen) is more specific for the prostate gland. The normal ranges can vary per age, and screening recommendations have also varied over the years, but should be done if patients have urogenital complaints.
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