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Implementing near-patient coagulation monitoring.

While portable coagulation monitors are easy to operate, putting them to proper use requires a concerted and coordinated effort.

Instituting a test, technique, or instrument outside the laboratory requires lab personnel to work through a myriad of details, many in uncharted territory. Near-patient testing must be planned with special care. Such testing adds a new dimension to QA and QC, for it often requires that non-laboratory staff master unfamiliar technology.

While establishing a near-patient coagulation monitoring system at our large university hospital center, we found it important to incorporate three nontechnical ingredients: commitment, communication, and cooperation. These measures had to be combined with exacting technical standards for quality control. The resulting blend of technical and personal lessons helped us identify issues and strategies associated with near-patient testing. In particular, we learned how such testing strongly affects workplace dynamics and how to delineate responsibilities, especially for nursing and laboratory personnel.

As a tertiary-care institution, our hospital has an inpatient population with critical and complex medical disorders, including a substantial number in the critical care unit who are recovering from acute myocardial infarction or thromboembolic disease. Anticoagulation therapy is an important part of such patient management. Coronary artery patency can be maintained most often in patients who are receiving thrombolytic therapy, such as streptokinase or tissue plasminogen activator, if they also receive heparin therapy during the first 24 to 48 hours.[1,2] In one trial, coronary artery patency was maintained in only 45% of patients whose heparin levels were subtherapeutic at 8 and 12 hours.[3] Furthermore, the risk of recurrent venous thromboembolism can be reduced by a factor of 15 in patients who are therapeutically anticoagulated within 24 hours.[4]

If heparin dosage is too high, however, significant bleeding may result.[5] Consistent, rapid, and reliable monitoring reduces the risks and maximizes the benefits of anticoagulation therapy. * APTT. The standard test for measuring coagulation status is activated partial thromboplastin time (APT7).[6] Until recently, APTT could be performed only in the central laboratory, where the patient's plasma had to be mixed with the reagents that activate the intrinsic pathway of coagulation. The turnaround time for APTT ranges from 45 minutes to several hours.

Even when performed Stat, APTT may not reflect the patient's true anticoagulation status. First, some aspects remain beyond the laboratory's full control, such as specimen transport from the nursing station to the lab. Second, the half-life of heparin varies among patients, depending on the disease state.[7] * New technology. The coagulation monitor that we acquired is a hand-held, battery-operated laser photometer weighing just over one pound. To measure APTT, a cartridge is inserted in the monitor and heated. A drop of whole blood is placed in the application well and drawn into the reagent chamber by capillary action. There it is mixed with an activator and soybean phosphatide to initiate coagulation.

The specimen moves along the reaction path until a clot forms. The endpoint is reached when the blood stops moving and is detected by a laser optical system. The time from specimen application to detection of the clot is the APTT value, which is displayed on the screen of the device. The normal value is 31 seconds; the range, 21 to 41 seconds. The therapeutic range for patients on heparin therapy is 2 to 2.5 times normal, or 62 to 78 seconds.

[Paragraph] Fast. The monitor provides APTT results within three minutes. The system permits immediate decisions concerning the management of heparin.

[Paragraph] Versatile. The monitor can also be used to measure prothrombin time (PT), commonly used in the management of warfarin therapy.

[Paragraph] Reliable. The correlation between results obtained with the cartridge APTT and the traditional test is virtually identical to that between standard plasma APTTs run with different reagents.[8] In comparing replicate specimens on the cartridge system to determine its precision, researchers found a correlation coefficient of 0.97. They concluded that the near-patient methodology avoids several pitfalls of the usual technique. For example, reagent lots are calibrated against a known standard, eliminating any potential variability among reagents. In addition, since whole blood is used, no problems arise related to anticoagulation, centrifugation, collection tubes, or delay in testing.

[Paragraph] Small specimen. The cartridge APTT requires only a small specimen of whole blood obtained from a fingerstick, venipuncture, or indwelling line. * Pilot program. Convinced of the monitor's reliability and usefulness to patient care, we initiated a pilot program in order to determine the feasibility of launching a bedside coagulation monitoring system in our 14-bed coronary care unit (CCU). All the CCU nurses participated in the pilot program, which ran for three months in 1991.

It was clear from the first that we would have to involve all appropriate clinical and laboratory departments in planning the pilot program. The team was headed by representatives of cardiology, clinical pathology/hospital laboratories, hematology/oncology, and nursing education and management. Together we identified our general objectives and discussed issues associated with start-up. The clinical pathology and hospital laboratories retained responsibility for the final outcome. Key factors to consider when integrating a near-patient testing coagulation system into a patient care regimen are listed in Figure I.

Our primary objective was to decrease turnaround time for APTT, thereby improving the management of heparinized patients. The committee identified the following questions, which would be applicable to any near-patient system: Which patients can best be served by the system? How steep will the learning curve be? Will the system aid or impede the provision of patient care by the nursing staff.? Who will perform the tests and oversee quality control? How will test results be reported and charged?

In drafting procedures for the laboratory and nursing staffs, we considered our experience in inaugurating other near-patient systems in our facility, such as glucometers for diabetes management, as well as information from the manufacturer of the coagulation monitor. We took care to use familiar terminology in the instructions we prepared for our employees. * Assignments. Responsibilities were disbursed as follows. Nursing would do fingersticks and provide all on-floor QC, record results on forms, send the forms to the lab, and maintain a bulk supply of cartridges. The lab would verify each new monitor with whole blood QC, maintain a performance log on each monitor and lot of cartridges, oversee QC performed by the nursing staff, enter results in the hospital information system, and purchase the cartridges. * Revising duties. A problem arose with the departmental assignment of quality control duties. The manufacturer recommends using two types: electronic QC cartridges during each shift and whole blood QC in validating each new lot or shipment of reagent cartridges. Moreover, each type of quality control requires two testing levels, reflecting high and low APTT values. Initially we expected the nursing staff to perform both types of QC on each shift. Our experience led us to rethink that plan.

While using the quality control cartridges is a simple, straight-forward procedure, QC involving the reconstitution of whole blood controls is more complex. We found that the nursing staff was using more cartridges than trained laboratorians would have. We decided to let the laboratory staff handle the whole blood controls to validate new reagent lots and shipments. The QC cartridge remains the responsibility of the nursing staff, monitored by the laboratory.

Refrigerator storage of a bulk supply of cartridges had originally fallen to the nursing department. Cartridges must be warmed to room temperature, then used within 30 days. Each time a nurse obtained an APTT result, he or she was supposed to fill out a separate documentation and billing form and send it to the lab, where a technician would key the information into the lab's computer. Yet over time, many cartridges were unaccounted for on the floor, signaling the need for more stringent control. Now the lab holds the bulk supply of cartridges and sends a limited number to the nurses every week. To aid tracking, a form accompanies each cartridge.

The cartridge waste problem was solved when the lab took over pipetting whole blood controls and the nurses grew more familiar with the test procedure. Cartridge use was significantly decreased within 30 days of instituting those changes.

The biomedical engineering department routinely checks the hardware and handles maintenance. Communicating with the manufacturer about servicing the monitors falls to that department as well.

For the most part, blood drawing is done with basic venipuncture. Since our CCU nurses were familiar with this technique, it fit easily into our program. When appropriate, they perform fingersticks or obtain blood specimens from indwelling lines.

The nursing staff discovered that for the first time, they were able to adjust heparin dosage based on patients' immediate coagulation status. It was now necessary for the nurses to learn more about the pharmacokinetics of heparin. As a result, the hospital has expanded its in-service training program for nurses.

Upon reviewing feedback from participating staff following the first month of the pilot program, the planning committee made some adjustments. Figure II shows how responsibilities are now allocated.

The CCU nursing department is currently documenting the benefits of the near-patient testing coagulation monitoring system on patient care. Anecdotal accounts suggest that obtaining real-time APTT has increased nurses' confidence in their knowledge of patients' coagulation status. Our hospital administration is seeking hard data on whether enhanced control of heparin therapy increases the quality of patient care and reduces the length of stay in the CCU or hospital.

An initial concern of the laboratory staff was that the near-patient testing system would lead to the loss of a medical technologist position. According to the latest figures, we are logging 500 APTTs per month with the monitor. The hematology/coagulation laboratory is performing approximately 5,000 standard APTTs per month - about the same number as before. No laboratory jobs have been eliminated because of the monitors. * Success. At the conclusion of the pilot program, we moved enthusiastically to full-scale implementation. The monitor is now in standard use for APTT testing in our CCU. We were pleased that after evaluating our performance recently, CAP inspectors made no recommendations for improving our quality control and maintenance procedures.

An added advantage is that the system has improved the working relationship between the clinical and laboratory staffs. We have gained an appreciation of our respective concerns and duties. Furthermore, we have captured that extra something often lost in the shuffle of a busy medical center - we have learned each other's names. * Blueprint. Implementing a near-patient coagulation monitoring system has opened a new chapter in patient care and workplace dynamics at the University of Massachusetts Medical Center. Our team of cardiologists, nurse educators and managers, laboratory technologists, and biomedical engineers has grown professionally from the experience. Above all, we are confident that the new protocols enhance patient care.

[1.] Bleich, S.D. Nichols, T.D.; Schumacher, R.R.; et al. Effect of heparin on coronary arterial patency after thrombolysis with tissue plasminogen activator in acute myocardial infarction. Am. J. Cardiol. 66: 1412-1417, 1990. [2.] Prins, M.H., and Hirsh, J. Heparin as an adjunctive treatment after thrombolytic therapy for acute myocardial infarction. Am. J. Cardiol. 67: 3A-11A, 1991. [3.] Hsia, J.; Hamilton, W.P.; Kleiman, N.; et al. A comparison between heparin and low-dose aspirin adjunctive therapy with tissue plasminogen activator for acute myocardial infarction. N. Engl. J. Med, 323:1433-1437, 1990. [4.] Hull, R.D.; Raskob, G.E.; Hirsh, J.; et al. Continuous intravenous heparin compared with intermittent subcutaneous heparin in the initial treatment of proximal-vein thrombosis, N. Engl. J. Med. 315: 1109-1114, 1986. [5.] Porter, S.R., and Letcher, J. Heparin: New uses, old problems with special reference to pharmacokinetics. and pharmacodynamics J, Invas. Cardiol. 3: 1,55-167, 1989. [6.] Spector, I., and Corn, M. Control of heparin therapy with activated partial thromboplastin times. JAMA 201:157-159, 1967. [7.] Hirsh, J.; van Aken, W.G.; Gallus, A.S.; et al. Heparin kinetics in venous thrombosis and pulmonary embolism, Circulation 53: 691, 1976. [8.] Ansell, J.; Tiarks, C.; Hirsh, J.; et al. Measurement of the activated partial thromboplastin time from a capillary (fingerstick) specimen of whole blood. Am. J. Clin. Pathol. 95: 222-227, 1991.
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Author:Nardella, Angela; Unser, Susan; Cyr, Jay; Connor, Diane
Publication:Medical Laboratory Observer
Date:Aug 1, 1992
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