PMLS LEC Finals

• Three ways in Media Inoculation Methods

  1. Directly into the bottle during specimen collection
  2. After collection as when blood has been collected in a syringe
  3. Use an intermediate collection tube to collect the sample for inoculation in the laboratory no at the bedside
• Blood culture specimens are always collected first in the order of draw to prevent contamination from other tubes.
• Direct inoculation


  1. Collect the specimen directly into the blood culture medium

  2. Use a butterfly and specially designed holder

  3. Connect the special holder to the Luer connector of the butterfly collection set

  4. Fill the aerobic vial first, because the butterfly tubing has air in it

  5. Avoid backflow by keeping the culture bottle or tube lower than the collection site and preventing the culture medium from contacting the stopper or needle during blood collection

  6. Mix each container after removing it from the needle holder

  7. After filling both containers and collecting blood for any other tests, remove the needle from the patient's arm, activate the safety device, and hold pressure over the site
• Blood is sometimes collected in an intermediate collection tube rather than blood culture bottles
• Yellow-top sodium polyanethol sulfonate (SPS) tube


  acceptable for usage in Intermediate collection tube
• Citrate, Heparin, EDTA, oxalate


  toxic to bacteria and are not recommended
• Presence of the antimicrobial agent in the patient’s blood can inhibit growth of the microorganisms in the blood culture bottle
• Antimicrobial Neutralization Products


  collected in:

  1. fastidious antimicrobial neutralization (FAN)(bioMerieux)
  2. antimicrobial removal device (ARD)(Becton Dickinson)
• An ARD contains a resin that removes anitmicrobials from the blood
• FAN contains activated charcoal, neutralizes the antibiotic
• A few milliliters of blood were collected into a plain red-top tube to clear the needle of thromboplastin contamination picked up as it penetrated the skin.
• Clearing tube is discarded if it was not needed for other tests.
• New studies have shown that a clear tube is not necessary when collecting for a PT or PTT.
• Clear tube is required for all other coagulation tests because the CLSI still recommends that they be the second or third tube drawn.
• blue-top CTAD tube is available for coagulation testing
• CTAD tubes


  contain:

  theopylline

  adenosine

  dipyridamole
• CTAD tubes inhibit thrombocyte activation between collection of the blood and performance of the test.
• NEVER pour two partially filled tues together to create a full tube, as the anticoagulant-to-blood ration will be greatly increased.
• Some coagulation factors V and VIIIm are not stable
• If the tests cannot be performed in a timely manner, the specimen must be centrifuged and the plasma frozen.
• If a coagulation specimen must be drawn from an indwelling catheter, the CLSI recommends drawing and discarding 5 mL of blood or 6 times the dead-space volume of the catheter before collecting the specimen.
• If heparin has been introduced into the line, it should be flushed with 5 mL of saline before drawing the discard blood and collecting the specimen.
• Arterial puncture is technically difficult and potentially more painful and hazardous than venipuncture
• Arterial specimens are not normally used for routine blood tests, even though arterial blood composition is more consistent throughout the body than venous, which varies relative to the metabolic needs of the area it serves
• The primary reason for arterial puncture

  To obtain blood for arterial blood gas (ABG) tests, which evaluate respiratory function
• Arterial blood is the best specimen for evaluating respiratory function because of its normally high oxygen content and consistency of composition
• Capillary blood, which is similar to arterial blood in composition provided that the puncture site is warmed prior to specimen collection, is sometimes used to test blood gases in infants
• Those who collect ABG specimens must have a thorough understanding of all aspects of collection in order to ensure accurate results and the safety of the patient
• ABG evaluation


  Used in the diagnosis and management of respiratory disorders such as lung disease to provide information about a patient's oxygenation, ventilation (air entering and leaving the lungs), and acid–base balance and in the management of electrolyte and acid–base balance in patients with diabetes and other metabolic disorders
• ABG specimens are very sensitive to the effects of preanalytical errors; therefore accurate patient assessment and proper specimen collection and handling are necessary to ensure accurate results
• For accurate results, an ABG specimen


  Must not be exposed to air. Consequently, the specimen must be collected in an anaerobic manner, which must be maintained throughout the collection, handling, and testing process
• Most ABG testing instruments directly measure

  • Hydrogen ion activity (pH)
  • Partial pressure of carbon dioxide (PaCO2)
  • Partial pressure of oxygen (PaO2)
• Other clinically useful analytes that may be measured

  • Total hemoglobin (tHb)
  • Oxyhemoglobin saturation (O2Hb)
  • Saturation of abnormal hemoglobins such as carboxyhemoglobin (COHb) and methemoglobin (metHb)
• Values for plasma bicarbonate (HCO3), base excess (or deficit), and oxygen (O2) saturation can be determined by calculation
• Many instruments also measure other critical care analytes such as sodium, potassium, chloride, ionized calcium, and glucose on the same specimen
• Some references use the abbreviations PO2 and PCO2 instead of PaO2 and PaCO2. Although these abbreviations are interchangeable, the latter two are more specific, as they refer to the partial pressure of these gases in arterial blood
• Commonly Measured Arterial Blood Gas (ABG) Analytes

  • pH
  • PaO2
  • PaCO2
  • HCO3
  • O2 saturation
  • Base excess (or deficit)
• Personnel who may be required to perform arterial puncture

  • Nurses
  • Medical technologists and technicians
  • Respiratory therapists
  • Emergency medical technicians
  • Level II phlebotomists
• Phlebotomists who collect arterial specimens must have extensive training involving theory, demonstration of technique, observation of the actual procedure, and performance of arterial puncture with supervision before performing arterial punctures on their own
• Level II personnel


  Supervise level 1 personnel and perform testing as well