Julie C. Paulson Happel, M.T. (ASCP), M.A., Photographs by: Joel Carl, M.A.*, Edited by: Marian Schwabbauer, Ph.D., CLDir (NCA)**
Upon completion of this section the learner will be able to:
I. Introduction
Quality patient care can be provided only if decisions are based on valid data. The validity of laboratory data is dependent on pre-analytical factors just as it is on analytical parameters. These pre-analytical factors will be discussed in the following text. The National Committee for Clinical Laboratory Standards has established standards for the pre-analytical phase.
II. Patient Education and Preparation
The first step is to educate and properly prepare the patient.
If the test requires the patient to be fasting, does the patient understand the requirements? For example, the patient may ask: "Can I have my morning coffee and/or cigarette if I don't eat anything?"
Next, consider which pre-existing patient conditions or habits might influence which test results; exercise, medications, and disease states should be considered.
Additionally, the importance of the time of day (diurnal variation), the timing (tolerance tests, half-life of drug), and the patient's posture (supine or upright) when drawing a blood sample should be considered.
The laboratory performing the test analysis often can provide information regarding pre-analytical requirements as they pertain to test results and reference ranges. Be sure to check with them regarding any questions.
III. Laboratory Requisitions (test orders)
Complete and legible laboratory requisitions must contain the following:
Incomplete or illegible requisitions may result in delay of patient's test results, an incorrect test being performed, or a test being performed on the wrong patient.
IV. Patient Identification
The identification of the patient is crucial. Briefly greet the patient, identify yourself, and establish a comfortable rapport with her/him. This is to help put the patient at ease. The patient being drawn must be identified as the person designated on the requisition. The following are suggested scenarios for patient identification for various clinical situations.
V. The Blood Sample
The integrity of the sample is dependent on using good venipuncture or skin puncture technique, drawing from an appropriate site, and avoiding hemolysis or contamination of a sample. When performing a venipuncture, do not draw above an IV site, from a vein that is sclerosed, from an area with a hematoma, from an arm with a fistula or shunt, or from the same side where a patient has had a mastectomy. When performing a skin puncture, do not use a finger or heel that is bruised, cold, swollen or cyanotic. Each procedure will include information on the appropriate site to select.
The following procedures for obtaining a blood sample, whether performing a venipuncture, fingerstick or heelstick, assume that the venipuncturist has...
Note: All patient blood specimens are to be treated with "Standard Precautions" as it is frequently impossible to know which specimens might be infectious. Gloves are to be worn when performing a venipuncture or skin puncture procedure.
Assemble all the equipment you might need in an organized manner.
Latex-free products are available. Examples of latex-free supplies include:
Venipuncture using evacuated tube/hub system (to be performed on adults or older children)
Note: If the patient is feeling queasy or faint, follow your lab's protocol for a fainting patient.
Venipuncture using a syringe
Syringes typically are used when the patient's veins are small or fragile and the evacuated tube suction could cause the vein to collapse. Using a syringe allows the venipuncturist to control the amount of suction applied to the vein.
The venipuncture procedure using a syringe follows the same steps as the evacuated tube system procedure. It differs slightly in equipment preparation and assembly, pulling the blood into the syringe, and transferring of blood into evacuated tubes.
The entry into the skin and the vein is exactly the same as with
the evacuated tube system.
Once you feel that the needle is in the vein, pull back gently on the
syringe plunger while holding the syringe barrel securely to keep the
needle in place in the vein. Use the syringe flange to brace against
as you pull back on the plunger just as you do when changing tubes
using a needle/hub system. Fill the syringe with the desired amount
of blood, release the tourniquet and complete the procedure exactly
as you would using an evacuated tube system. (See needle
re-directing when using a syringe.)
To transfer the blood from the syringe to the appropriate tubes, remove the needle from the syringe and replace it with an 18 or 19 gauge needle. Using a large bore needle will help prevent hemolysis of the blood and maintain the integrity of the sample. Do not apply pressure to the plunger, allow the tubes to fill by the negative pressure of the vacuum tube. Since there is the possibility of the formation of micro clots, the blood should be transferred in the appropriate order as quickly as possible into the tubes containing anticoagulant and mixed immediately.
Again, label the tubes and check the status of the patient before allowing the patient to stand or leave.
Venipuncture Using an IV Infusion Set
An IV infusion set (butterfly) is used for venipuncture when you draw from a hand or foot vein or from a very small or fragile vein; when the angle of needle entry is awkward, e.g. when a patient is in bed and repositioning of her/his arm is difficult or painful, or when the patient's vein is difficult to find or draw. If a small child must have blood drawn using the venipuncture procedure, a 23 gauge IV infusion set attached to a 1 ml or 3 ml syringe is typically used. This allows for good control and helps prevent excessive suction from the syringe if the blood is drawn slowly and carefully.
The butterfly's needle and plastic "wings" are attached to a length of flexible tubing which is, in turn, attached to either a syringe or luer adapter/hub assembly. The butterfly is lighter and less cumbersome than either the other two assemblies. Thus, it allows better control and "feel" when drawing a patient. Additionally, as soon as the needle is in the vein, blood is visible in the tubing rather having to wait and see as when using the either of the other two methods.
The venipuncture procedure using an IV infusion set follows the same steps stated previously in the evacuated tube system procedure. The IV infusion set differs slightly in a lower angle of needle entry and equipment preparation and assembly. Whether the set is attached to a syringe or to a hub/tube assembly will determine if you will need to transfer the blood to tubes or if they were drawn directly into tubes.
When you are ready to perform the venipuncture, grasp the wings
between your thumb and index or middle finger, hold the skin and vein
taut with your other hand, and enter the skin with the needle.
As soon as you see blood in the tubing, you may pull back on the
syringe plunger or engage the vacuum tube. If you do not see blood on
the tubing you will need to redirect
the needle. When the needle is well anchored in the vein, you may
release the butterfly "wings"; otherwise continue to gently hold the
"wings" during the procedure. If using a syringe, fill it with the
desired amount of blood, release the tourniquet, remove the needle
and complete the procedure exactly as you would using a syringe. If
using a needle/hub assembly, fill the tubes and complete the
procedure as you would drawing directly into evacuated tubes. Again,
be sure to check the status of the patient before allowing the
patient to stand or to leave.
Note: If you are using a safety infusion set, be sure to immediately slide the safety cover over the needle and discard the set. Alternatively, to prevent accidental re-stick with the infusion set needle, hold the base of the needle or the wings as you remove the needle and do NOT let go of the needle base until it is being placed in the biohazard sharps container.
Skin Punctures
Blood obtained from a skin puncture is a mixture of arterioles, venules and capillaries and contains interstitial and intracellular fluids. There is more of the arterial blood than venous blood due to pressure differences in the capillaries. Also, the venous blood in the skin more closely resembles arterial blood than in the other parts of the body. This is especially true when the puncture site has been warmed. Warming the skin primarily increases the arterial blood flow.
Because of the differences in the blood concentration of certain analytes in capillary versus venous or arterial blood, the blood collection technique and site both should be noted on the reports form. This allows the physician to consider the collection technique used when interpreting the results.
The key to obtaining a good skin puncture sample (finger or heel) is performing a puncture that results in free flowing blood. This is dependent upon accessing the capillaries, venules, and arterioles of the dermis and subcutaneous tissues. Manufacturers have developed varied types and sizes of skin puncture devices to safely access this juncture. The devices are usually designed specifically for:
These devices vary in the depth and
width of the cut or puncture.
Preventing hemoylsis is also often technique dependent. Be sure the alcohol has completely air dried before performing the puncture. Residual alcohol may cause red blood cell lysis Also, if blood flow is inadequate or begins to decrease, do not excessively squeeze the adjacent tissue; rather, perform a second skin puncture using all new equipment. Never re-stick the same site or re-use a skin puncture device. Most safety devices will lock after use and prevent re-use. Allow the tube to fill by capillary action. Do not scrape the tube against the site as this may cause mechanical lysis of the RBCs. Technique is even more important when performing a skin puncture on an infant. Infants often have high packed cell volumes and increased red blood cell fragility.
The Finger Puncture Procedure
A finger puncture procedure is performed instead of the venipuncture or heelstick when the patient is a small child older than six months, or the specimen was unattainable by venipuncture. The finger puncture procedure is not to be performed on infants as the distance from the skin surface to the bone at the thickest portion of the distal phalanx of a newborn is between 1.2 to 2.2 mm. The currently available skin puncture depth range is 0.85 to 4.5 mm and thus could easily cause injury to the bone.
The finger puncture is typically used for lower sample volume
tests that can be placed into special micro-sized tubes.
These tests include CBC, white blood cell differential, hemoglobin,
hematocrit, and limited chemistry tests, e.g. Na, K, Cl, CO2, BUN,
creatinine, and glucose. Fingersticks are also frequently used in
public health screening events, e.g. cholesterol, HDL and glucose
self-monitoring at home.
Again, this procedure assumes that patient education and preparation, test request verification, patient identification, and procedure explanation have occurred.
The steps for the finger puncture are:
The Heelstick Procedure
Skin puncture of the heel is frequently the least problematic
method for obtaining a blood sample from an infant. The puncture is
performed on the most medial or lateral portion of the plantar
surface of the heel. Do not perform a puncture on the central area of
the foot, the arch of the foot, nor the posterior curvature of the
heel. See the shaded portion on diagram.
Also, do not puncture a previously used site which may be infected.
The National Committee for Clinical Laboratory Standards states that
the puncture depth should be no more than 2.4 mm. Studies indicate
that for certain infants, including premature infants, even this
depth may be excessive.
The heel puncture procedure follows the same steps as the finger puncture procedure. Some of the disposable lancets are specifically designed for heelsticks.
VI. Specimen Handling and Transportation
Once a sample is drawn properly, it must be processed, stored, assayed and/or transported correctly or the results may be invalid. Certain blood samples must be placed on ice, others kept at body temperature, and some centrifuged and frozen immediately. If you are sending samples drawn in your office to an outside laboratory for analysis, make sure your specimen collection, handling, and transportation procedures meet the guidelines set by the reference laboratory.
The following is a list of pertinent hyperlinks.
Julie C. Paulson Happel, M.T. (ASCP), M.A., Photographs by Joel Carl, M.A.
The NCCLS standard approved July 1, 1991 for skin punctures is Document H4-A3 Vol. 11 No. 11, "Procedures for the Collection of Diagnostic Blood Specimens by Skin Puncture." This document addresses safety precautions, the sites, devices, and techniques for skin puncture and sample collection on infant through adult patients, and the analyte concentration in the skin puncture specimens.
Other NCCLS documents pertinent to sample collection include the following (Check the NCCLS web site for the latest version):
NCCLS Address:
National Committee for Clinical Laboratory Standards
940 West Valley Road, Suite 1898
Villanova, PA 19085
Phone: (610) 688-0100
FAX: (610) 688-0700
e-mail: exoffice@nccls.org
http://www.nccls.org/
Needles:
Evacuated tubes are manufactured to withdraw a predetermined volume of blood and are typically sterile. They have an expiration date beyond which they should not be used as the vacuum may not be accurate or the anticoagulant may not be effective. The expiration date and the tube type is printed on each individual tube. Tubes selected for general use should be displayed on a wall chart in one or more locations in the venipuncture area to assure proper information for various types of collections. The most common use of the tubes are listed below.
Note: Be sure to check with the laboratory performing the actual test for their specific tube requirements.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Top: Safety female adapter, used to safely transfer blood drawn into a syringe into an evacuated tube.
Left to Right: Needle/hub/evacuated tube assembly; IV infusion set/luer adapter/hub/evacuated tube assembly; IV infusion set/syringe assembly.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Evacuated tubes and micro-collection tubes. (Left to right: EDTA, Na Citrate, SST, Plain, Na Citrate, Na Heparin, EDTA, Acid Solution A, EDTA, and SST). The sample volumes of these tubes range from 250 microliters to 10 milliliters.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Top row: Skin puncture devices for fingersticks.
Bottom row: Skin incision devices for fingersticks.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Commercial heel warmer and skin puncture devices for heelsticks.
Note:
Choosing the Site:
Note: If you do enter an artery, complete the draw and hold the site for a minimum of 5 minutes. Ensure all bleeding has stopped before allowing the patient to leave.
Palpating a Vein:
To palpate a vein, gently and firmly push down on the skin with your index finger, then slowly release the pressure. If you are palpating a vein, you will feel the vein bounce back as you release the pressure. If you are palpating a tendon, it will feel like a rope or thread that is pulled tightly. If you are in doubt, release the tourniquet and palpate the area again. If the "tight rope" is still there, you were palpating a tendon. If you feel a pulse, you were palpating an artery.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Venipuncture using a multidraw needle/hub/evacuated tube assembly.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Venipuncture using a multidraw needle/hub/evacuated tube assembly. Anchoring the vein above and below the insertion point poses a greater risk of an accidental needlestick to the venipuncturist.
Adjusting Needle Position:
Sometimes when performing a venipuncture, the needle isn't initially positioned correctly in the vein for good blood flow.
If the needle is close to the correct place, re-directing the needle is better than immediately withdrawing the needle. Slightly re-adjusting the needle may eliminate a second venipuncture. Do not attempt to stick the patient more than twice. Ask another trained person to help.
To redirect the needle, first feel for the vein to determine if the needle is beside the vein, is not in quite deep enough, or is in too deep. If the needle has been pushed through the vein you will see a brief spurt of blood when you engage the tube, pull back slowly until you see blood entering the tube. If the needle is on top of the vein or not in quite deep enough to obtain normal flow into the evacuated tube, anchor the vein, increase the degree of angle of the needle slightly, and move forward in the same direction as the vein. If the needle is beside the vein, anchor the vein, pull the needle back slightly, re-adjust the needle and move forward into the vein. If you are sure the needle is in the vein but no blood is flowing into the tube, change to a new tube of the same tube type. (If, while re-directing the needle, you hear a hiss, you have lost the vacuum and will need to replace the tube with a new one.)
Julie C. Paulson Happel, M.T. (ASCP), M.A., Photographs by Joel Carl, M.A.
The blood collection tube(s) must be immediately positively identified at the time of collection. Samples obtained in tubes must be identified with a label firmly attached to the tube. The label should have at least the following information:
Alternatively, a tube may be identified by the requistion label attached to the tube. The requisition and its label are preprinted with a number. The requisition must contain the information as stated previously.
Equipment Preparation:
When preparing the needle/syringe needle assembly, pull back on the syringe plunger before attempting to draw with a syringe. It often takes a significant amount of pull to release the plunger from the base of the syringe barrel the first time. After the plunger has been pulled back once, it can be pulled back fairly easily and smoothly and is ready for use.
Be sure attach the needle to the syringe tightly enough so that no frothing of blood occurs at the connection when you apply the suction. This pooling and frothing will cause hemolysis.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Venipuncture using a needle/syringe assembly.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Venipuncture using a needle/syringe assembly. Anchoring the vein above and below the insertion point poses a greater risk of an accidental needlestick to the venipuncturist.
Needle Re-directing When Using a Syringe:
Re-directing the needle when using a needle/syringe assembly is very similar to the procedure when using a needle/hub assembly. First feel for the vein to determine if the needle is beside the vein, is not in quite deep enough, or is in too deep. If the needle has been pushed through the vein, pull back slowly, while still pulling gently on the plunger, until you see blood entering syringe. (The distance is often is only about the length of the tip bevel.) If the needle is on top of the vein or not in quite deep enough to obtain normal flow into the syringe, anchor the vein, increase the degree of angle of the needle slightly and move forward in the direction of the vein. Then proceed to pull back on the plunger for blood flow. If the needle is beside the vein, anchor the vein, pull back slightly, re-direct the needle and move forward into the vein.
Note: If there is significant resistance, even with some blood flow, to pulling the plunger back, the needle is not positioned correctly and continuing to forcibly pull the plunger back may cause hemolysis of the sample.
Julie C. Paulson Happel, M.T. (ASCP), M.A., Photographs by Joel Carl, M.A.
Note:
Equipment Assembly:
The integrity of the tubing should be check before using an infusion set as on rare occasions there may be defective tube or connection between the tubing and the needle. It is very quick to do and it is also a good time to straighten the tubing and prepare the syringe as stated above. Attach the butterfly to a syringe, pull back on the plunger and expel the air through the infusion set tubing. You should hear air rush out of the end of the needle. If not, check the connection to the syringe and try again. If you do not hear the appropriate sound, discard the butterfly and attach a new one.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Venipuncture using a safety IV infustion / syringe assembly.
Site No. 1: This is typically the better or easier-to-draw site as the vein is straight, longer, and is likely better anchored. Also the vein is usually easier to anchor on the flat area of the back of the hand rather than on the edge of the hand.Site No. 2: This is an acceptable or good vein but it is more difficult to anchor and maintain the needle during the drawing process.
Re-directing the Needle When Using a Butterfly:
When you have not entered the vein, redirecting of the needle into the vein is basically the same as it is for either the needle/hub or needle/syringe assembly. However once you are in a small vein with a 23 gauge/butterfly assembly, very slight movement will stop or start blood flow. Frequently the cause of this is that the small bevel of the needle touches the vein wall. Raising the back of the butterfly needle slightly often restarts blood flow. If not, next try repositioning the needle by slightly moving the needle sideways, and finally forward or backward. Again feeling for the vein and holding the skin and vein taut helps.
Warming the Skin:
Warming the skin puncture site with a warm, moist towel at a temperature no more than 42 degrees C or using a commercially available heel warmer for at least three minutes is recommended. This can increase the blood flow through the site seven-fold. When collecting blood for pH or blood gas determination, warming the site is essential.
Heelstick:
Burns, Edward, MD: "Development and Evaluation of a New Instrument for Safe Heelstick Sampling of Neonates". Laboratory Medicine, Vol. 20, No. 7, July 1989. This article compares puncture versus incision types of semi-automatic skin puncture devices, including differences in healing of the wound.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
A. Lasette: Laser finger perforator for capillary blood sampling. In July 1998, the FDA cleared it for home use in glucose and hematocrit blood collection for ages 5 years old to adult. Developed by Cell Robotics and marketed by Chronimed.
Image from Cell Robotics, copywrite for use by Media Page
B.: Varied sizes of International Technydyne Corporation skin incision devices for heelsticks.
C. Varied sizes of International Technydyne Corporation skin incision devices for fingersticks.
D.: Varied sizes of Becton Dickinson lancets.
Hemolysis may occur due to:
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Micro-collection tubes. Sample volumes range from 250 microliters to 1.8 ml.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photograph by Julie C. Paulson Happel, M.T. (ASCP), M.A.
Peform finger or heel puncture across the fingerprints as the blood will more likely bead rather than run down the "channels" of the fingerprints. Also, the puncture devices (the depth) are designed to be used in this manner.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photograph by Julie C. Paulson Happel, M.T. (ASCP), M.A.
Fingerstick procedure using a skin puncture lancet.
Blood Collection:
It is acceptable to apply gentle pressure from the base of the finger progressing to the tip, then ease the pressure and repeat. Do NOT squeeze the finger hard or excessively. You will obtain a much better sample by performing a second skin puncture.
When collecting blood samples from a skin puncture, the correct order of collection is:
* If blood for cell morphology cannot be collected directly from the skin puncture site onto a clean slide, blood smears from blood collected into EDTA should be made within one hour.
** Micro-capillary tubes for spun hematocrit (packed cell volume) should be filled at least 2/3 full and be run in duplicate.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Shaded areas represent acceptable skin puncture sites on an infant's heel.
Julie C. Paulson Happel, M.T. (ASCP), M.A.
Photographs by Joel Carl, M.A.
Heelstick using an incision device.
Julie C. Paulson Happel, M.T. (ASCP), M.A., Photographs by Joel Carl, M.A.
Becan-McBride, Kathleen, EdD.; "Pre-Analytical Phase an Important Requistion of Laboratory Testing." ADVANCE for Medical Laboratory Professions; September 28, 1998.
Garza D and Becan-McBride K. Phlebotomy Handbook, 2nd Ed. Norwalk, Connecticut: Appleton and Lange: 1989.
National Committee for Clinical Laboratory Standards; "Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture; Approved Standard-Fourth Addition." Document H3-A4 Vol. 18 No. 7, June 1998.
National Committee for Clinical Laboratory Standards. Procedures for the Collection of Diagnostic Blood Specimens by Skin Puncture. Document H4-A3. Vol. 11 No. 11, 1991.
Occupational Safety and Health Administration. Latex Allergy. http://www.osha-slc.gov/SLTC/latexallergy/index.html January 27, 1999.
Phelan, S. Phlebotomy Techniques: A Laboratory Workbook. Chicago, Ill.: American Society of Clinical Pathologists: 1993.
Spina Bifida Association of America. Latex Information Page. http://www.sbaa.org/Latex.htm October 15, 1998.
University of Iowa Hospital and Clinics, Pediatric Phlebotomy Training Manual. 1994, unpublished.
University of Iowa Hospital and Clinics, Phlebotomy Training Manual. 1994, unpublished.