Why do you release the tourniquet when drawing blood?
A prolonged tourniquet time may lead to blood pooling at the venipuncture site, a condition called hemoconcentration. Hemoconcentration can cause falsely elevated results for glucose, potassium, and protein-based analytes such as cholesterol. Show
Ideally, the tourniquet should be in place no longer than one minute to prevent hemoconcentration. If the phlebotomist takes longer than one minute to assess and locate vein of choice for venipuncture, it is best practice to release the tourniquet, assemble supplies and reapply tourniquet immediately before needle insertion. Tourniquets are a very useful tool for identifying veins when taking blood or inserting a cannula. However, leaving a tourniquet on for too long can affect the interpretation of blood test results. Ideally the tourniquet should be left on for no longer than a minute at a time - if you are having difficulty finding a vein, then release the tourniquet, wait for blood flow to return, then reapply the tourniquet. Always remember to release the tourniquet when leaving a patient's bedside, as very prolonged tourniquet application can result in significant complications.
Next Page ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Preferred venous access sites, and factors to consider in site selection, and ability to differentiate between the feel of a vein, tendon and artery. Patient care following completion of venipuncture. Safety and infection control procedures. Quality assurance issues. Identify the additive, additive function, volume, and specimen considerations to be followed for each of the various color coded tubes. List six areas to be avoided when performing venipuncture and the reasons for the restrictions. Summarize the problems that may be encountered in accessing a vein, including the procedure to follow when a specimen is not obtained. List several effects of exercise, posture, and tourniquet application upon laboratory values. VENIPUNCTURE PROCEDUREThe venipuncture procedure is complex, requiring both knowledge and skill to perform. Each phlebotomist generally establishes a routine that is comfortable for her or him. Phlebotomists are considered to have occupational exposure to blood borne pathogens. The performance of routine vascular access procedures by skilled phlebotomists requires, at a minimum, the use of gloves to prevent contact with blood. Airborne precautions may be considered to provide a level of safety against infectious diseases such as tuberculosis, influenza, and COVID-19. Precautions include a medical grade face mask. With risk for blood spatter a face shield provides protection. A face mask reduces risk for blood culture specimen contamination. Laboratory coats or work smocks are not typically needed as personal protective equipment during routine venipuncture, but an employer must assess the workplace to determine whether certain tasks, workplace situations, or employee skill levels may result in an employee's need for laboratory coats or other personal protective equipment to prevent contact with blood. It is an employer's responsibility to provide, clean, repair, replace, and/or dispose of personal protective equipment/clothing. As part of presenting a professional appearance, an institutional dress code may include wearing of a laboratory coat or smock. Patient identification is critical for safety. At least two patient identifiers, such as name and date of birth, are needed. Label collection tubes after identification of the patient. Interruptions and distractions during medical encounters and procedures should be avoided. Several essential steps are required for every successful collection procedure:
ORDER FORM / REQUISITIONA requisition form must accompany each sample submitted to the laboratory. This requisition form must contain the proper information in order to process the specimen. The essential elements of the requisition form are:
An example of a simple requisition form with the essential elements is shown below: LABELING THE SAMPLEA properly labeled sample is essential so that the results of the test match the patient. The key elements in labeling are:
Automated systems may include labels with bar codes. Examples of labeled collection tubes are shown below: EQUIPMENT:THE FOLLOWING ARE NEEDED FOR ROUTINE VENIPUNCTURE:
ORDER OF DRAWBlood collection tubes must be drawn in a specific order to avoid cross-contamination of additives between tubes. The recommended order of draw for plastic collection tubes is:
NOTE:Tubes with additives must be thoroughly mixed. Erroneous test results may be obtained when the blood is not thoroughly mixed with the additive. Transferring a sample from one collection tube to another or mixing blood from different collection tubes must be avoided. PROCEDURAL ISSUESPATIENT RELATIONS AND IDENTIFICATION: The phlebotomist's role requires a professional, courteous, and understanding manner in all contacts with the patient. Greet the patient and identify yourself and indicate the procedure that will take place. Effective communication - both verbal and nonverbal - is essential. Proper patient identification MANDATORY. If an inpatient is able to respond, ask for a full name and always check the armband or bracelet for confirmation. For an inpatient DO NOT DRAW BLOOD IF THE ARMBAND OR BRACELET IS MISSING. For an inpatient the nursing staff can be contacted to aid in identification prior to proceeding. An outpatient must provide identification other than the verbal statement of a name. Using the requisition for reference, ask a patient to provide additional information such as a birthdate. A government issued photo identification card such as a driver's license can aid in resolving identification issues. If possible, speak with the patient during the process. The patient who is at ease will be less focused on the procedure. Always thank the patient and excuse yourself courteously when finished. PATIENT'S BILL OF RIGHTS: The Patient's Bill of Rights has been adopted by many hospitals as declared by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO). The basic patient rights endorsed by the JCAHO follow in condensed form are given below. The patient has the right to:
VENIPUNCTURE SITE SELECTION: Although the larger and fuller median cubital and cephalic veins of the arm are used most frequently, the basilic vein on the dorsum of the arm or dorsal hand veins are also acceptable for venipuncture. Foot veins are a last resort because of the higher probability of complications. Certain areas are to be avoided when choosing a site:
PROCEDURE FOR VEIN SELECTION:
PERFORMANCE OF A VENIPUNCTURE:
PHLEBOTOMY PROCEDURE ILLUSTRATED:PERFORMANCE OF A FINGERSTICK:
FINGERSTICK PROCEDURE ILLUSTRATED: ADDITIONAL CONSIDERATIONS:To prevent a hematoma:
To prevent hemolysis (which can interfere with many tests):
Indwelling Lines or Catheters:
Hemoconcentration: An increased concentration of larger molecules and formed elements in the blood may be due to several factors:
Prolonged Tourniquet Application:
Patient Preparation Factors:
REASONS FOR CANCELING A LABORATORY TESTA test that has been ordered may be cancelled due to problems unrelated to drawing the specimen, and these are the most common causes for cancellations:
A test may be cancelled due to a technical problem in the specimen collection process:
SAFETY AND INFECTION CONTROLBecause of contacts with sick patients and their specimens, it is important to follow safety and infection control procedures. PROTECT YOURSELF
PROTECT THE PATIENT
TROUBLESHOOTING GUIDELINES:IF AN INCOMPLETE COLLECTION OR NO BLOOD IS OBTAINED:
IF BLOOD STOPS FLOWING INTO THE TUBE:
PROBLEMS OTHER THAN AN INCOMPLETE COLLECTION:
BLOOD COLLECTION ON BABIES:
HEELSTICK PROCEDURE ILLUSTRATED: PEDIATRIC PHLEBOTOMY:
COLLECTION TUBES FOR PHLEBOTOMY
Red TopADDITIVENoneMODE OF ACTIONBlood clots, and the serum is separated by centrifugationUSESChemistries, Immunology and Serology, Blood Bank (Crossmatch) Gold TopADDITIVENoneMODE OF ACTIONSerum separator tube (SST) contains a gel at the bottom to separate blood from serum on centrifugationUSESChemistries, Immunology and Serology Light Green TopADDITIVEPlasma Separating Tube (PST) with Lithium heparinMODE OF ACTIONAnticoagulates with lithium heparin; Plasma is separated with PST gel at the bottom of the tubeUSESChemistries Purple TopADDITIVEEDTAMODE OF ACTIONForms calcium salts to remove calciumUSESHematology (CBC) and Blood Bank (Crossmatch); requires full draw - invert 8 times to prevent clotting and platelet clumping Light Blue TopADDITIVESodium citrateMODE OF ACTIONForms calcium salts to remove calciumUSESCoagulation tests (protime and prothrombin time), full draw required Green TopADDITIVESodium heparin or lithium heparinMODE OF ACTIONInactivates thrombin and thromboplastinUSESFor lithium level, use sodium heparin For ammonia level, use sodium or lithium heparin Dark Blue TopADDITIVEEDTA-MODE OF ACTIONTube is designed to contain no contaminating metalsUSESTrace element testing (zinc, copper, lead, mercury) and toxicology Light Gray TopADDITIVESodium fluoride and potassium oxalateMODE OF ACTIONAntiglycolytic agent preserves glucose up to 5 daysUSESGlucoses, requires full draw (may cause hemolysis if short draw) Yellow TopADDITIVEACD (acid-citrate-dextrose)MODE OF ACTIONComplement inactivationUSESHLA tissue typing, paternity testing, DNA studies Yellow - Black TopADDITIVEBroth mixtureMODE OF ACTIONPreserves viability of microorganismsUSESMicrobiology - aerobes, anaerobes, fungi Black TopADDITIVESodium citrate (buffered)MODE OF ACTIONForms calcium salts to remove calciumUSESWestergren Sedimentation Rate; requires full draw Orange TopADDITIVEThrombinMODE OF ACTIONQuickly clots bloodUSESSTAT serum chemistries Light Brown TopADDITIVESodium heparinMODE OF ACTIONInactivates thrombin and thromboplastin; contains virtually no leadUSESSerum lead determination Pink TopADDITIVEPotassium EDTAMODE OF ACTIONForms calcium saltsUSESImmunohematology White TopADDITIVEPotassium EDTAMODE OF ACTIONForms calcium saltsUSESMolecular/PCR and bDNA testing ReferencesGiavarina D, Lippi G. Blood venous sample collection: Recommendations overview and a checklist to improve quality. Clin Biochem. 2017;50(10-11):568-573. Kiechle FL. So You're Going to Collect a Blood Specimen: An Introduction to Phlebotomy, 13th Edition (2010), College of American Pathologists, Northfield, IL. Dalal BI, Brigden ML. Factitious biochemical measurements resulting from hematologic conditions. Am J Clin Pathol. 2009 Feb;131(2):195-204. Lippi G, Salvagno GL, Montagnana M, Franchini M, Guidi GC. Phlebotomy issues and quality improvement in results of laboratory testing. Clin Lab. 2006;52(5-6):217-30. Lippi G, Blanckaert N, Bonini P, Green S, Kitchen S, Palicka V, Vassault AJ, Mattiuzzi C, Plebani M. Causes, consequences, detection, and prevention of identification errors in laboratory diagnostics. Clin Chem Lab Med. 2009;47(2):143-53. Occupational Safety and Health Administration, United States Department of Labor. https://www.osha.gov/laws-regs/standardinterpretations/2007-10-26 and https://www.osha.gov/OshDoc/data_BloodborneFacts/bbfact03.pdf (Accessed June 13, 2022). Phelan MP, Reineks EZ, Berriochoa JP, Schold JD, Hustey FM, Chamberlin J, Kovach A. Impact of Use of Smaller Volume, Smaller Vacuum Blood Collection Tubes on Hemolysis in Emergency Department Blood Samples. Am J Clin Pathol. 2017;148(4):330-335. Sanders AM, Agger WA, Gray AM, Fischer CM, Kamprud EA. Use of hair nets and face masks to decrease blood culture contamination rates. Diagn Microbiol Infect Dis. 2019;95(1):15-19. doi: 10.1016/j.diagmicrobio.2019.04.001. Uman LS, Birnie KA, Noel M, et al. Psychological interventions for needle-related procedural pain and distress in children and adolescents. Cochrane Database Syst Rev. 2013 Oct 10;(10):CD005179. doi: 10.1002/14651858.CD005179.pub3. Valenstein PN, Sirota RL. Identification errors in pathology and laboratory medicine. Clin Lab Med. 2004;24(4):979-96, vii. World Health Organization. WHO guidelines on drawing blood: best practices in phlebotomy. https://www.ncbi.nlm.nih.gov/books/NBK138650/pdf/Bookshelf_NBK138650.pdf (Accessed June 13, 2022) And for our furry friends: Joslin JO. Blood Collection Techniques in Exotic Small Mammals. Journal of Exotic Pet Medicine. 2009;18(2):117-139. Are you supposed to leave the tourniquet on when drawing blood?Once sufficient blood has been collected, release the tourniquet BEFORE withdrawing the needle. Some guidelines suggest removing the tourniquet as soon as blood flow is established, and always before it has been in place for two minutes or more.
What happens if you don't release the tourniquet?A prolonged tourniquet time may lead to blood pooling at the venipuncture site, a condition called hemoconcentration. Hemoconcentration can cause falsely elevated results for glucose, potassium, and protein-based analytes such as cholesterol.
Why should release tourniquet before blood withdraw?Rationale: Releasing the tourniquet before obtaining the required amount of blood for the laboratory tests reduces bleeding at the site when the needle is withdrawn.
When should the tourniquet be released?Old aspects recommend that tourniquet should be released in every 15-30 minutes intervals, but new studies show and current training books recommend that tourniquet can be used safely within two hours and a tourniquet should not be released unless the hemorrhage can be controlled surgically.
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