Blood gas testing in the laboratory and at the point of care: finding the right mix.
With its requirement for rapid turnaround time (TAT), blood gas testing is a natural choice for point-of-care testing (POCT). The traditional blood gas laboratory and POCT are in a state of rapid evolution. I believe that both can coexist because both types have advantages and limitations in their present technology.
It becomes clear that the laboratorian must be either a leader or a significant participant in implementing POCT to ensure the right choices are made when deciding between utilizing POCT and laboratory testing.
For instance, there are many questions that confront the laboratorian about POCT for blood gases:
1. In what areas should point-of-care blood gas testing be implemented?
2. Who should be responsible for oversight and testing?
3. Will POCT save time, money, or patient length of stay (LOS)?
4. Which analyzer should be selected?
5. Will the caregivers and patients always be more satisfied with POCT than with present services?
6. How will POCT affect existing laboratories?
The perceived benefits of POCT often are dependent on the specific testing arrangements existing prior to the initiation of POCT. Therefore, a Stat laboratory in an ideal location that offers a variety of tests and is also served by a pneumatic tube system may be more desirable to caregivers than POCT. On the other hand, a distant laboratory that requires manual delivery of samples from an ICU is almost certainly a model of the past. In addition, a laboratory located in a small room within an ICU and offering only blood gases may be a prime candidate for elimination by POCT.
Areas of use
An essential requirement for successful implementation of POCT is that the users embrace POCT while realizing both the responsibilities and the benefits. Information from several institutions shows that point-of-care blood gas testing is frequently present in many cardiac operating rooms, ICUs (medical, surgical, and neonatal), emergency departments, cardiac catheterization laboratories, and respiratory care services. In addition, we have received requests from outpatient areas where surgical and pulmonary patients are seen.
When POCT is implemented in an area, one or more groups must maintain responsibility for the following items:
1. CLIA regulatory license, CAP inspections, monitoring QC results
2. maintaining fresh, labeled reagents and supplies
3. performing routine maintenance, troubleshooting, and service
4. analyzing, recording, and reviewing calibration and quality control checks
5. analyzing samples
6. reporting and documenting the orders and results
7. ensuring that all users are adequately trained and authorized
Because complete responsibility for these items usually is not desired by the caregivers, many of them often remain with the laboratory.
Who does POCT?
The types of personnel who potentially do point-of-care blood gas testing include medical technologists, respiratory therapists, nurses, anesthesia technicians, perfusionists, and hybrid laboratorian/caregivers who have received additional training in the area that is new to them.
Both the clinical laboratory and respiratory care service are natural overseers for point-of-care blood gas testing. Which of these maintains responsibility depends on many factors, such as:
1) who previously held the responsibility for blood gas testing
2) the ability to serve all point-of-care blood gas testing locations
3) the analyzer type used for POCT
Indeed, both groups may participate in offering blood gas testing near the patient. Typically, the respiratory therapist is more attuned to testing than are nurses, who want and need the rapid TAT, but who are frequently fully occupied with taking care of patient needs. Laboratorians are experienced in maintaining CLIA licensure, controlling supplies, and recording and documenting both QC and corrective actions. Therefore, laboratorians, respiratory therapists, and nurses frequently share these responsibilities.
Instrument in laboratory or at point of care?
The complete replacement of all blood gas testing in the laboratories by POCT instruments generally is limited to special circumstances. Usually, the laboratory and POCT coexist, with each doing various proportions of testing.
The circumstances that favor testing in the laboratory include: having a well-functioning pneumatic tube system in the laboratory that is connected to the appropriate ICU, instant transmission and availability of results in a form and place convenient to the caregiver, close proximity of the laboratory to the unit, lack of caregiver time for doing POCT, and a lack of need for the fastest possible blood gas results.
Different models of POCT have evolved and will continue to evolve to meet the specific needs of an institution. The following describes markedly different solutions to the needs of each organization.
The first example illustrates a hospital where virtually all blood gas testing is done as POCT. At this hospital, every respiratory therapist is stationed on a floor and carries a handheld analyzer. They are called to do every blood gas test whenever and wherever it is needed. There are one or two respiratory therapists per floor. They have responsibility for storing and distributing the test cartridges, doing daily electronic control checks, and maintaining regulatory compliance. The very large reagent costs of POCT were offset by not staffing the existing laboratory, presumably without adding respiratory therapists to handle the POCT.
Next is an example where seven stationary POCT analyzers were added to several busy areas of the hospital, where more than 40,000 blood gas tests are done bedside: in the cardiac surgery operating room (OR), cardiac care unit, neonatal ICU, surgical ICU, two medical ICUs, and the emergency department. The laboratory maintains responsibility for providing supplies, control material, and administrative oversight. Savings were achieved by reducing both the caregiver's time and the FTEs in the main laboratory.
As an example of low-volume POCT, we are now starting to utilize movable analyzers in areas with only an occasional need for a blood gas test, but do not have rapid access to the laboratory, such as in outpatient surgery and clinics at which patients with pulmonary problems are seen. The small analyzers are especially suited to low-volume testing where the faster and potentially lower-cost-per-test larger analyzers cannot be justified economically.
Choice of the point-of-care analyzer
An important part of successful point-of-care blood gas testing is the choice of analyzer. The suitability of an analyzer in a specific setting depends on factors such as the total workload and pattern of workload, the analytical skill of testing personnel, the volume of blood available, and the desired location and placement of the point-of-care analyzer(s). Several types of analyzers are available for POCT applications:
1. Small, portable, handheld devices
2. Small analyzers, easily portable
3. Medium-size analyzer, movable on a cart when necessary
4. Standard laboratory analyzers
The portable, handheld devices are suited for each analyst carrying an analyzer at all times. The cost of each cartridge is relatively high ($5-$7), but is somewhat independent of test volume. In general, the likelihood of being in-use or misplaced does not lend these analyzers to portable use by multiple operators, unless each operator has one in his possession.
The point-of-care analyzers designed to remain stationary generally may be better suited to areas in which several operators ordinarily use the analyzer. One analyzer (GemPremier) uses either 150- or 300-test reagent packs, which must be used within two weeks. Depending on which test-pack is used and how efficiently a pack is utilized, the cost per test may be either higher or lower ($2.50 to $6.50 or more) than for analyzers with single-use disposable cartridges.
In areas of high test volume, a standard analyzer has advantages of lowest cost per test ($1 to $3, depending on volume and frequency of analyzing liquid quality control material), ease of use, and much shorter time to obtain a result (60 seconds versus 3.5 minutes to find, open, and place a cartridge, then wait for cartridge calibration and analysis of the sample).
Important note. The cost per test must include the analysis of control material. Some point-of-care analyzer manufacturers emphasize daily use of only an electronic monitor (which checks only the analyzer function), with liquid controls analyzed only at lot changes (monthly or less). For analyzers with single-use cartridges, this is a much less expensive protocol than liquid controls run daily or on each shift. One should consider their individual requirements for frequency of controls when calculating their expected cost per test.
We have used standard laboratory analyzers at the point-of-care in busy ORs for more than 15 years. Anesthesia technicians run most samples, while the laboratory calibrates, maintains, and holds license to the analyzers. This approach provides high-quality results at a low reagent cost per test of about $1. A significant issue is that these analyzers do not yet have the operator and patient identification security that is now necessary for POCT.
Communication between the laboratory and the users
Once POCT is instituted, a vital ingredient is maintaining communication with the groups who do the test. This is especially challenging because of the cross-departmental responsibilities for POCT. One has to deal with both administrative issues as might be discussed in a monthly committee meeting and with daily operational needs that often require rapid resolution. Usually, a cross-departmental POCT committee needs to be formed to discuss the many issues that will arise about POCT. This committee may meet monthly to quarterly and must have sufficient authority to make decisions when necessary.
Savings by POCT
While a faster result turnaround is expected for POCT, this depends on the ability of the analyst to quickly handle the workload, which has limits. The overall cost savings achieved by POCT are often either based on subjective assessments or are very difficult to calculate. Factors to consider are: labor, reagents, blood product usage, the caregiver's time, saving of additional diagnostic procedures, and the patient's LOS.
For example, labor may be saved in one area, yet increased in another; reagent cost may increase while blood usage decreases. It is difficult to put a monetary value on patient or physician satisfaction if a faster TAT allows a patient to be moved sooner. If an insufficient POCT result necessitates an additional medical procedure or, worse, a lawsuit, other cost benefits will be depleted quickly.
Among the best studies done to determine the savings of POCT are those by Parvin, et al. and Despotis, et al. In the study by Parvin, the patient LOS in the emergency department was used as the criterion for success. Two periods were compared: a three-month period in which samples for Chem 6 (Na, K, Cl, HC[O.sub.3], BUN, and glucose) testing were sent to the laboratory, and another three-month period in which samples were tested by the i-STAT. During the latter period, samples for this test panel could not be sent to the laboratory. After reviewing nearly 5,000 patient records, they found that the patient LOS in the emergency department did not improve with POCT.
The study by Despotis was on 66 patients who underwent cardiac surgery with cardiopulmonary bypass and who developed microvascular bleeding. These patients then either received the usual empiric therapy (without any coagulation test results), or therapy based on the PT, PTT, and platelet count results done at the point of care. This report concluded that the availability of rapid coagulation test results at the point of care allowed less FFP, packed RBC, and platelets to be used, and the patients had less chest tube drainage and shorter operative times.
The excellent studies cited here show that POCT may have either significant improvements or no improvements, depending on the setting, the tests, and the patients involved.
Many factors will determine the impact that POCT will have on patient care. For example, POCT may offer little benefit to the emergency department, but may expedite caring for patients in an OR or an ICU. One group of patients may have a decreased LOS, another may require less blood products, while another may not benefit at all. The studies cited here required enormous effort and time. While overall savings that result from POCT can be difficult to quantify, the assumed cost savings may have the most impact within a particular hospital. These savings in physician time, medical procedures, ICU beds, or.blood-product usage will offset increases in reagent costs.
Point-of-care blood gas testing will not be a panacea for all. Someone still must do the sample handling and analysis; further, some point-of-care analyzers are more cumbersome and slower than comparable standard laboratory analyzers. In addition, analyzers designed specifically for POCT often are not suited to handle large boluses of work.
With so many variables, POCT represents a frontier for the laboratorian and the caregiver in providing laboratory tests. The specific arrangements of the laboratory and the POCT, who does the test, where it is done, and which analyzer to choose all are questions that need to be answered by the laboratorians and caregivers at each institution.
1. Parvin CA, Lo SF, Deuser SM, Weaver LG, Lewis LM, Scott MG. Impact of point-of-care testing on patient's length of stay in a large emergency department. Clin Chem. 1996;42:711-7.
2. Despotis GJ, Santoro SA, Spitznagel E, et al. Prospective evaluation and clinical utility of on-site monitoring of coagulation in patients undergoing cardiac operation. J Thorac Cardiovasc Surg. 1994; 107:271-79.
John Toffaletti, PhD, is Director of Blood Gas Services, Associate Professor of Pathology at Duke University Medical Center in Durham, N.C.
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|Title Annotation:||Critical Issues in Critical Care|
|Publication:||Medical Laboratory Observer|
|Date:||Sep 1, 1997|
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