1 / 47

Errors that Affect Arterial Blood Gas Results

Errors that Affect Arterial Blood Gas Results. Carl Mottram, RRT RPFT FAARC Director - Pulmonary Function Labs & Rehabilitation Associate Professor of Medicine - Mayo Clinic College of Medicine. Arterial Blood Gases (ABG’s). Reflect oxygenation Adequacy of gas exchange in the lungs

nitza
Download Presentation

Errors that Affect Arterial Blood Gas Results

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Errors that Affect Arterial Blood Gas Results Carl Mottram, RRT RPFT FAARC Director - Pulmonary Function Labs & Rehabilitation Associate Professor of Medicine - Mayo Clinic College of Medicine

  2. Arterial Blood Gases (ABG’s) • Reflect oxygenation • Adequacy of gas exchange in the lungs • Acid - base balance CO2 pH O2

  3. Garbage in, Garbage out!

  4. ABG Laboratory Standards and Guidelines • Clinical and Laboratory Standards Institute (CLSI) • C46-A2 Blood Gas and pH Analysis and Related Measurements (2009) • H11-A4 Procedures for the Collection of Arterial Blood Specimens (2004)

  5. ABG Laboratory Standards • AARC Clinical Practice Guidelines • In-Vitro pH and Blood Gas Analysis and Hemoximetry (1999); currently in review • Sampling for Arterial Blood Gas Analysis (1999) • ATS Pulmonary Function Management and Procedure Manual (2005)

  6. ABG Laboratory Standards

  7. CLSI’s Path of Workflow

  8. CLSI’s - Path of Workflow • What processes have the highest rate of error? • Pre-analytical errors still account for nearly 60%-70% of all problems occurring in laboratory diagnostics • Nine steps – G. Lundberg • “the brain to brain cycle”

  9. Clinical Chemistry 53:7 1338–1342 2007

  10. Pre-analytical Errors • Personnel • Patient identification and preparation • Sample collection, container, and procedure • Sample handling, transport, and storage

  11. Pre-analytical - Personnel • Job qualifications • Job descriptions • Orientation • Training • Competency assessment • Continuing education • Performance appraisal

  12. Pre-analytical - Patient and sample identification • Two identifiers or electronic barcode • Sample label • Name and medical number (birth date or personal identification number) • Date

  13. Pre-analytical – Patient Variables • Patient’s full name • Identification number • Birth date/age • Location of the patient • Date and clock time of sampling

  14. Pre-analytical – Patient Variables • Body temperature • Clinical indication • Respiratory rate • Name or initials of person who obtained the specimen • Name of physician requesting the test.

  15. Pre-analytical – Patient Variables • Ventilatory status (e.g. spontaneously breathing or mechanically supported) • Mode of ventilation (i.e., pressure support) or delivery device (i.e., cannula or mask) • Site and manner of sampling • arterial puncture, capillary puncture, or indwelling catheter • Position and/or activity • Upright/supine; rest/exercise

  16. Pre-analytical - - Sample collection, container, and procedure • Common • Radial artery • Dosrsalis pedis • Brachial • Femoral • Uncommon • anterior peroneal, axillary and superficial temporal

  17. Pre-analytical - ABG Sample collection • Preferred site - Radial • Superficial and provides rich collateral circulation • Collateral can be evaluated by the modified Allen’s test E.V. Allen, Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases. Am J Med Sci (1929), pp. 237-244.

  18. Pre-analytical - ABG Sample Collection • Syringe • Dry lithium heparin • Engineered sharps protection (one-handed) • 20-25 gauge short-bevel needles (radial)

  19. Pre-analytical – Sample • Sample error • Failure to observe and record • Contamination of sample • Room air (bubbles) • Venous blood mixing • Flush solution if drawn from an arterial line • Heparin, if using liquid • Delay in analysis • ICU audit showed that 40% of the samples had air or froth and that 4% of sample had a delay in analysis Woolley A. et al Journal of Critical Care. 18(1):31-7, 2003 Mar.

  20. Pre-analytical – Sample • Sample error: Failure to observe and record • Environmental Factors • Suctioning • Recent ventilator changes without crisis • Activity and positioning • Failure to record appropriate information • FIO2, mode of delivery, ventilator management, patient activity • Woolley A. et al Journal of Critical Care. 18(1):31-7, 2003 Mar.

  21. Pre-analytical – Sample • Sample Error: Contamination by room air • Partial pressures of both PaO2 and PaCO2 will migrate towards room air: • PaO2 greater than ~100 torr will decrease • PaO2 less than ~100 torr will increase • PaCO2 greater than 40 will decrease • PaCO2 less than 40 will increase • pH will follow PaCO2 change • Woolley A. et al Journal of Critical Care. 18(1):31-7, 2003 Mar.

  22. Pre-analytical – Sample • Sample Error: Contamination by venous blood • Know normal venous blood values • pH=7.38 ; PvO2=40 torr, PvCO2=46 torr, SvO2=75% • Small amount of venous blood can make a significant difference (esp in PaO2) • Cross check • Patient’s clinical status & ABG picture • PaO2 & SaO2 vs. SpO2

  23. Pre-analytical – Sample • Sample Error: Hemolysis of the sample • Study demonstrated 1.2% in adult patients and 8.5 in pediatric of ABG samples with various degrees of hemolysis Clin Chem Lab Med 2011;49(5):931–932

  24. Pre-analytical – Sample • Sample Error: contamination by heparin • Excessive heparin will drop PCO2 values • Anticoagulant • Lyophilized lithium heparin is recommended • If liquid heparin (sodium or lithium, 1,000 units/mL of blood) is used, excess heparin (all except that filling the dead space of the syringe and needle) should be expelled and a blood sample of 2-4 mL be drawn

  25. Pre-analytical – Sample • Sample Error: Delay in analysis • Cellular process • Consumes O2 & generates CO2 • Quantitative Effect • @ 37 C in 1 hr • pH fall 0.05 units • PaCO2 5 torr • PaO2 fall depends on initial level • if high (>300 torr) will    precipitously • if lower (100 torr) will    20 torr/hr • if low (< 60 torr) will  but < 20torr/hr

  26. Pre-analytical – Sample • Sample Error: Delay in analysis • Normal RBCs not responsible for significant metabolism • Metabolic activity predominantly • Leukocytes & reticulocytes • Example: • WBC=276,000 cells/mm3 PaO2 from 130 to 58 torr in 2 minutes • WBC=450,000 cells/mm3 PaO2 to 0

  27. Pre-analytical – Sample • Current guidelines related to icing sample • If blood gas analysis will not be performed within 30 minutes after specimen collection, ice the sample • Procedures for the Collection of Arterial Blood Specimens: H11-A4 • Specimens held at room temperature must be analyzed within 30 minutes of drawing; iced samples should be analyzed within 1 hour. • AARC’s CPG Sampling for Arterial Blood Gas Analysis

  28. Analytical • Follow manufacturer’s instructions carefully when introducing sample • Improper introduction can cause erroneous results, especially from air bubbles, clots, or leaks • Repeat analysis if; • Inconsistent with patient’s past results and/or condition • Internally inconsistent (pH, CO2, HCO3) • At the extreme range of expected values

  29. Analytic • Operator error • Failure to label sample • Equipment malfunction • Analysis with out-of-control instrument • QC material and Levey-Jennings Plots • Failure to mix an sample • Gently rotate for a minimum of 2 minutes • Can raise the pH of a sample by 0.11 units • Calculated SaO2 and CaO2 • Erroneous in the presence of dyshemoglobins

  30. Analytical Interferences • PO2: nitrous oxide, halothane, isoflurane • Interferences with Co-oximetry • Sulfhemoglobin • Methylene Blue • Fetal hemoglobin • Turbidity: hyperlipemia

  31. Post - Analytical • Comment on the quality of the specimen, transportation or delays in analysis • Accurate transcription (review process) • Meeting the expectations of the customer • Satisfaction surveys

  32. Post - Analytical • Post-analysis sample management (disposal) • Posting data to the record in a timely fashion (i.e. turn-around time) • Validating EMR report with lab data

  33. Quality Control in the Lab • Clinical Laboratory Improvement Act 1988 • Law!! • Enforced by the CDC, CLIAC, and CMS

  34. Quality Control in the Lab • Daily QC with Levy-Jennings plots • John Westgard PhD • www.westgard.com

  35. Westgard’s Rules for Quality Control • Rule 1: (1 : 2s).......One Value outside ± 2 s.d. • No action required, still considered “in control” • Rule 2-6 considered “out of control” corrective action required • Rule 2: (1 : 3s).......One value outside ± 3 s.d. • Rule 3: (2 : 2s).......Two consecutive values outside ± 2 s.d. • Rule 4: (R : 4s).......Range from highest to lowest values > 4 s.d. • Rule 5: (4 : 1s).......Four consecutive values outside ± 1 s.d. • Rule 6 : (10 x).......10 consecutive values falling on one side of the mean

  36. Levy-Jennings Plot: “In control”

  37. Levy-Jennings Plot: Rule 1 • Rule 1: (1 : 2s).......One Value outside ± 2SD • No action required, still considered “in control”

  38. Levy-Jennings Plot: Rule 2 • Rule 2: (1 : 3s).......One value outside ± 3 SD

  39. Levy-Jennings Plot: Rule 3 • Rule 3: (2 : 2s).......Two consecutive values outside ± 2SD

  40. Levy-Jennings Plot: Rule 4 Rule 4: (R : 4s).......Range from highest to lowest values > 4SD

  41. Levy-Jennings Plot: Rule 5 • Rule 5: (4 : 1s).......Four consecutive values outside ± 1SD

  42. Levy-Jennings Plot: Rule 6 • Rule 6 : (10 x).......10 consecutive values falling on one side of the mean

  43. CLSI’s Quality Systems QSE: Assessment • College of American Pathologist • Inter-laboratory comparison – Blinded samples • Inter-laboratory comparison – Daily QC materials (provided by vendor) • Institutional comparison – Other lab within the same institution

  44. Selection process Installation Calibration log Maintenance log Troubleshooting log Service and repair log Training Documentation and review CLSI’s Quality Systems QSE: Equipment

  45. CLSI’s Quality Systems QSE – Customer Focus

  46. What’s these mean to you? • Any shortfall in the “Path of workflow” can effect the quality of the test results • Practitioners need to be knowledgeable about the current quality models as they relate to ABG’s

  47. Questions?

More Related