Discussion Our results show that the procedure previously proposed 4 reduces drastically the tourniquet application time. This significant reduction of the application time is able to eliminate the venous stasis impact, that is an important source of unpredictable laboratory variability 5 — 8 , 12 — Private laboratories exhibit a significantly lower time of tourniquet application than public laboratories after the training period i. A reliable explanation for this is that private laboratories have more ergonomic furniture in blood collection rooms 4.
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It is almost a rite of passage for those responsible for arterial blood gas ABG laboratories. What is it? These guidelines routinely go through the revision process, the latest being CA2, which was just published in We will briefly review the highlights from these documents to familiarize you with their content and, we hope, entice you to examine them more thoroughly.
Arterial Blood Specimen Collection The collection of arterial specimens is a core competency for respiratory therapists. CLSI published the first proposed standard for the collection of arterial blood specimens in The first approved edition was published in and has been updated over the years with the fourth edition HA4 published in The standard focuses on the quality system essentials QSEs specific to arterial sample collection and the path of workflow.
The primary focus is to address the collection of whole blood specimens for blood gas, electrolyte, and metabolic determinations. The appendices include multiple illustrations that are helpful in the instruction of both students and respiratory therapists.
This guideline describes an overall quality system model that includes the path of workflow concept and quality system essentials. In any quality system, one needs to look at all aspects of the path of workflow, which in the laboratory means we need to assess the preanalytical, analytical, and postanalytical process. In each of these phases of the work performed are quality system essentials. In the QSE Personnel, a process should exist for training of new and existing employees.
Collection of arterial specimens is generally a competence that should be assessed annually. Changes in procedure or identified training needs should prompt an update for existing employees.
One aspect of the process control QSE relates to interferences that need to be considered. Multiple substances have the potential to interfere with the measurement of blood gases, electrolytes, and other metabolites. Understanding these interfering substances related to the measurement and equipment is a critical element of the training procedures. Examples of known substances include ice cooling , heparin, sodium thiopental, dopamine, ethanol, isoniazide, and sodium fluoride.
The guideline reviews each interfering substance and potential impact on blood gases, electrolytes, glucose, and lactate results. Documents and records must address the test request form. Additional information may be required by regulatory or institutional policies. A periodic assessment of the quality system should be performed, and improvements in process made as appropriate. Quality indicators across the path of workflow can be identified and monitored Table.
The information from these indicators will drive improvement activities or changes in process. Attention to the details in each of these areas is key to preventing preanalytical errors. Test ordering should be consistent with institutional polices and address all components required on the test request form. Attention to this element is a primary preventive strategy to eliminate preanalytical error.
All precollection conditions should be confirmed prior to specimen collection. Generally, 20 to 30 minutes of steady state breathing on the required Fio2 is recommended prior to sample collection.
Documentation as defined by institutional policy and best practice should be included on the requisition form. Explanation of the procedure to the patient is completed in a pleasant and reassuring manner. Selection of the site for the arterial puncture includes assessment of collateral blood flow, accessibility and size of the artery, and periarterial tissue. The CLSI document clearly outlines equipment required to collect an arterial specimen.
Hazards of the procedure include vasovagal response, arteriospasm, hematoma, thrombosis, and embolism. Regardless of the frequency of the hazard, each therapist should be well informed in preventive techniques, recognition, and treatment of each.
Procedures for arterial punctures, arterial cannulation, and collection from arterial lines are reviewed in detail. Handling and transport of the arterial specimen is another opportunity for respiratory therapists to prevent preanalytical error. The use of a coolant and impact on results are imperative to understand. If a specimen is analyzed within 30 minutes, a plastic syringe is recommended.
The standard and best practice is to transport the specimen at room temperature and analyze the specimen. The specimen should not be cooled. This should be the exception to normal practice. It was initially published in , with the most recent update in the sixth edition published in The standard reviews all components of the path of workflow, including site selection, collection procedure, handling capillary tubes, and identification and labeling.
It also addresses the devices and analyte variations between skin puncture and venipuncture specimens. Statistical and clinical differences have been reported between skin puncture and venous blood in the concentrations of glucose, potassium, total protein, and calcium. All but glucose has been found to be lower in skin puncture blood. As respiratory therapists appreciate, there are significant differences between the composition of skin puncture blood and specimens collected by arterial puncture.
The potential sites for collection for infants less than 1 year of age include the lateral or medial plantar surface of the heel. A heel puncture must not exceed 2. A specific procedure should be used for arterialization of the site.
This procedure will increase the blood flow sevenfold. It does not burn the skin and will result in insignificant changes for routinely tested analytes with the exception of Po2. The Po2 is expected to be lower in the capillary sample. Low blood flow and high Po2 will increase the difference between the capillary sample and an arterial puncture sample. Engineering controls such as using plastic tubes and work practice controls minimize risk to the health care personnel collecting the specimen.
Respiratory therapists obtaining capillary blood specimens should complete a review of the standard as part of training and whenever updates are available.
We served as advisors to the writing committee for this revision. It has a comprehensive review of the concepts and definitions and would be a great reference for your staff. This section expands on the recommendation of using plastic syringes that are kept at room temperature and analyzed within 30 minutes, by noting that samples collected for special studies eg, shunt studies should be analyzed within 5 minutes.
Incorrect introduction of a sample can cause erroneous results, especially by contamination from air bubbles.
There is an excellent review of analytical interferences, specifically listing interferences for all variables measured. As an example, interference of Po2 sensors with anesthetic gases has been reported.
Nitrous oxide, halothane, and isoflurane are capable of diffusing across the gas permeable membrane of the Po2 sensor, resulting in high Po2 readings. Also reviewed are the interferences with measurement of electrolytes and with co-oximetry.
The comprehensive list of interferences is impressive and a great resource for your staff. The guideline covers blood gas analyzer calibration and quality control.
One subject that is often confusing and covered extensively is traceability. Certainly, participation in an interlaboratory comparison program such as those provided by CAP would then meet the requirements of traceability. The section also reviews both surrogate sample controls, such as tonometry, aqueous, and emulsion control solutions, and nonsurrogate or alternative quality control.
The latter is electronic QC, automated procedural controls, or automated internal checks. These types of controls might check all or a portion of the analytical components each time a patient sample is analyzed and can be used in conjunction with or in place of external control materials. Carl D. For further information, contact rtmagazine allied Clinical and Laboratory Standards Institute.
Available at: www. Accessed September 8,
CLSI Sets the Standards for ABG Laboratories