Procedure

Procedure

Activated Clotting Time of Whole Blood on the Hemochron Models 401 and 801

Prepared by

Date Adopted

Supersedes Procedure

Review Date

Revision Date

Signature

Distributed to

No. of Copies

Distributed to

No. of Copies

Dialysis Department

Pathology Department

Pediatric Intensive Care

Cardiovascular Surgery

ECMO Department

Cardiac Cath Lab

PRECAUTION: WHILE PERFORMING THIS PROCEDURE, THE FOLLOWING

SAFETY MEASURES MUST BE TAKEN: GLOVES MUST BE WORN; SMOKING, EATING, DRINKING, APPLICATION OF COSMETICS, AND MANIPULATION OF CONTACT LENSES ARE PROHIBITED IN ALL TECHNICAL WORK AREAS. REFER TO THE UNIVERSAL PRECAUTIONS POLICIES.

Complexity: Moderate

I. Method:

The activated clotting time (ACT) is measured with the Hemochron Model 401 or 801 instruments. The ACT test is commonly used for heparin anticoagulation monitoring during bypass surgery, neonatal Extracorporeal Membrane Oxygenation (ECMO), hemodialysis, radio frequency ablation, and critical care.

II. Principle:

Heparin therapy is essential in maintaining hemostasis during certain procedures such as bypass surgery; its administration poses significant risk to the patient. Heparin may vary twelve-fold in both patient sensitivity and the rate at which it disappears from the blood. Overdosing heparin can result in dangerous bleeding, while under dosing can lead to thrombosis.

The Hemochron (Models 401 and 801) is a portable, battery operated instrument designed to perform whole blood coagulation tests. The Model 401 instrument has one test well for single or sequential test determinations. The Model 801 instrument has two individual test wells allowing for simultaneous performance of two coagulation tests. The operation of both the 401 and the 801 is the same.

The ACT is a test in which fresh whole blood is added to a test tube containing an activator (celite glass particles or kaolin) and timed for the formation of a clot. The type of activator used may affect the degree of prolongation of the ACT.

The Hemochron clot detection mechanism consists of a precision aligned magnet within a test tube and a magnetic detector located within the test well. When a test tube is inserted into the well, the magnetic detector senses a magnet within the test tube as the tube slowly rotates. When the clot begins to form, it causes the magnet to lift within the tube. Since the magnet has been displaced, it is no longer sensed by the instrument's magnetic detector. The instrument gives an audible beep and displays the coagulation time.

III. Materials:Hemochron Model 401 and 801 Instrumentation:

Location

Model

Serial #

CMH #

Test Tube Type

Daily QC

ECMO

801

T12460-8

P214/P215

Electronic

ECMO

401

T11607-4

P214/P215

Electronic

Dialysis

401

T12546-4

P214/P215

Electronic

Dialysis

401

T12618-4

P214/P215

Electronic

CVS

401

T12620-4

CA510

Electronic

CVS

401

T12622-4

CA510

Electronic

PICU

401

R5233-4

P214/P215

Electronic

Cath Lab

801

R5138-8

CA510

Whole Blood

Syringes for sample collection:

Tuberculin syringe with no anticoagulant

One of the following test tubes:

§ CA510 (black flip-top) - store at room temperature - No expiration date.

§ P214/P215 (clear plastic flip-top) - store at room temperature - No expiration date.

IV. Specimen Collection and Handling:

Prior to collecting the patient’s sample, the patient’s identity must be verified by looking at the arm band. Obtain blood specimen. Use a 5 cc syringe to collect fresh whole blood. Adhere to the appropriate technique below:

A.(CA510):

Indwelling venous blood line:

NOTE: Do not obtain blood from heparinized access line, lock or indwelling heparin lock.

§ Discontinue fluids drip, if required.

§ Use a two-syringe technique -perform a 5 cc draw and discard the first syringe. Obtain a 3 cc sample with the second syringe for testing.

Extracorporeal blood line port:

§ Flush the extracorporeal blood access line by withdrawing 5 cc of blood then obtain a 3 cc sample with a second syringe for testing.

Venipuncture:

§ Use a two-syringe technique and discard the first 2 cc draw. Obtain a 3 cc sample with the second syringe for testing.

Vacuum Draw:

§ Perform venipuncture maintaining the arm in its downward position.

§ Push tube to the end of the holder and pierce the top of the tube. The contents of the tube should not come in contact with the needle or stopper to prevent the possibility of backflow from the tube.

§ Remove the tourniquet once blood begins to flow into the tube.

§ The appropriate blood volume has entered the tube when the blood flow into the tube ceases.

B.(P214/P215):

Draw 0.4 ml blood sample from a previously flushed extracorporeal line using a 1 cc tuberculin syringe. Make certain that the blood sample is representative (do not take sample from a line through which heparin has been administered).

Extracorporeal blood line port:

§ Flush the extracorporeal blood access line by withdrawing 3 cc of blood.

V. ACT Procedure:

A.(CA510)

1. From the collection syringe dispense exactly 2.0 ml of blood into the test tube. At the same time, depress the "start" button of the Hemochron test well as blood first appears in the tube.

2. Close the flip-top. Immediately agitate the test tube vigorously from end-to-end ten times to disperse the activator.

3. Insert test tube into the Hemochron test well and rotate the tube clockwise until green "detector" light is illuminated. Turn one additional revolution to assure the green light remains on.

4. At the sound of the buzzer, record the test result.

B.(P214/P215):

1. Before drawing the blood sample, hold test tube vertically and tap the tube bottom several times on a horizontal surface to shake activator particles down into testing zone.

2. Flip open the cap of the Hemochron plastic test tube and dispense 0.4 ml of blood into the test tube. At the same time, depress the "start" button as blood first appears in the test tube.

3. Close the flip-top. Holding the test tube in an upright position with thumb and forefinger, mix blood and activator by gently flicking the bottom of the tube with remaining fingers.

4. Insert test tube into the Hemochron and rotate the tube clockwise until green "detector" light is illuminated. Turn one additional revolution to assure that the green light remains on.

5. At the sound of the buzzer, record the test result.

VI. Quality Control:

The quality control products are intended to verify proper instrument and test performance, as well as operator technique.

Materials Needed:

§ Hemochron Whole Blood Liquid Controls:

(Cat. No. CPL-2: Cardiac Cath, CVS)

(Cat. No. CPL 1: ECMO, Dialysis, PICU)

§ Hemochron Instrument 801 or 401

§ Plastic syringe (5 cc) with 20 or 21 gauge needle

§ Hemochron Coagulation test tubes

§ Electronic QC

A. Whole Blood Quality Control:

1. Handling and Storage:

Whole Blood controls are stable until the marked expiration date when stored at 4-8°C. Room temperature storage is possible for non-punctured vials; room temperature dating is to a maximum of seven weeks, but must never exceed the marked expiration date.

Note: If kept refrigerated, allow all quality control and coagulation test vials and/or test tubes to first reach room temperature and then stabilize for at least 20 minutes before use. This may take up to 60 minutes.

2. Frequency:

If Electronic QC’s are not used, two levels of quality control (normal and abnormal) must be performed every 8 hour shift that patient testing occurs. Controls should also be run after any maintenance procedures and whenever the patient values do not match the expected results. It is the responsibility of the personnel performing the patient testing to perform quality control.

If Electronic QC’s are used, two levels of whole blood QC are used to validate each box of ACT test tubes. Once a box is validated for use, print or affix a “VERIFIED” label on the outside of the box.

3. Whole Blood Quality Control Test Procedure:

a. Peel back the flip top on the distilled, deionized water vial, but do not remove the crimp seal (use this technique when opening each vial). Using a 5 cc plastic syringe with needle, withdraw exactly 2 cc from the distilled, deionized vial and transfer into the plasma vial by direct puncture of the stopper. Start the Hemochron timer by depressing the start button. Remove the filled syringe from the plasma vial.

b. Using moderate end-to-end inversion, agitate the plasma vial until 30 seconds elapses on the Hemochron display screen to achieve rehydration. Avoid excessive agitation which will cause foaming of the plasma. Verify complete rehydration of the control visually.

c. Restart the Hemochron timer and allow the plasma to stabilize for 60 seconds.

d. While the plasma is stabilizing, use the same syringe and needle to withdraw exactly 1 cc from the calcium chloride vial.

e. After 60 seconds transfer 1 cc of calcium chloride into the plasma vial by direct puncture of the stopper. Do not remove the syringe and needle from the vial.

f. Firmly holding the syringe in place, vigorously agitate the vial

approximately four to six times.

g. Using the syringe already in place, withdraw the correct amount of the mixture for transfer into the appropriate Hemochron test tube:

CA510- 2 cc

P214/P215- 0.5 cc

h. For CA510 test tubes: Transfer the 2 cc into the Hemochron test tube. Depress the timer button. Vigorously agitate the tube four to six times. Place the tube in the test well, and then gently rotate the tube clockwise until the green "detector" light is illuminated. Rotate the tube one additional turn and assure that the green light remains on.

For P214/P215 test tubes: Transfer 0.5 cc into the Hemochron test tube. Depress the start button. Holding the tube vertically, flick the tube 4 to 6 times. Place the tube in the test well and then gently rotate the tube clockwise until the green "detector" light is illuminated. Rotate the tube one additional revolution to assure the green light remains on.

I. When the test is complete, read the ACT and record the value on the appropriate Quality Control Log Sheet. There are two types of quality control logsheets for whole blood controls.

4. Troubleshooting:

If quality control does not fall within the acceptable limits the following steps should be taken:

a. Verify that the quality control materials and test tubes are within expiration date. Check tubes for cracks and adequate activator. Verify that the controls and reagents are stored correctly. Verify operator technique. Repeat test using fresh control material.

b. If test is still out-of-limits, perform weekly maintenance and repeat control.

c. If control remains out-of-limits, DO NOT USE INSTRUMENT, put a sign on instrument stating that it is out of order. Contact Pathology department for further assistance (Point of Care Medical Technologist ext. 4431 or pager #4431). Use a backup instrument until problem is resolved (see page 2 for list of instruments and locations).

d. Document all corrective actions on the quality control log.

B. Electronic Quality Control:

1. Handling and Storage:

Electronic QC Verification Tubes are stored at room temperature. They are reusable and have no expiration date.

2. Frequency:

Two levels (normal and abnormal) are used every eight hour shift of patient testing. The normal level is a 100 second QC tube (Cat# EQC-N). There are two abnormal levels. Those areas using CA510 tubes will use the 500 second abnormal QC tube (Cat# EQC-AII) and those using P214/P215 tubes will use the 300 second QC tube (Cat# EQC-AI).

3. Electronic Quality Control Test Procedure:

a. Choose the appropriate QC verification tubes.

b. Insert the electronic QC tube into the test well.

c. Simultaneously press the START buttons on the electronic QC tube and the Hemochron test well.

d. When the test is complete, read the ACT and record the value on the Electronic Quality Control and Maintenance log sheet. Acceptable values are ± 10 seconds.

4. Troubleshooting:

If quality control does not fall within the acceptable limits the following steps should be taken:

a. Repeat Electronic QC Tube.

b. If a fault message is illuminated next to the test result, the battery in the verification tube is nearly depleted and should be replaced.

The verification tubes require 2 “AA” batteries.

d. Document all corrective actions on the quality control log.

VII. Maintenance:

Document all maintenance performed on monthly maintenance sheet.

A. Weekly:

1. Inspect and clean the test well and test tube drive collar of residual dried blood or other foreign matter. Use a cotton swab moistened with a 10% bleach solution. Remove all moisture with dry cotton swab after cleaning.

2. Verify that heater light is lit.

B. Monthly:

Check function of incubator. This can be performed by any operator or a Medical Technologist. The temperature of the test wells is verified using the Hemochron Temperature Calibration Test Tube. Place tube in well and press "Start". If the instrument has not been in use, press the "Prewarm" button prior to temperature check. The temperature of each well should be 37± 0.5 °C. If temperature is not within limits, contact the Pathology department. Use backup instrument (see page 2 for list of instruments and locations.) Document temperature results on the maintenance log.

C. Six Month:

1. Check function of timer against a stopwatch.

2. Check clot detector sensitivity (Calibration Verification).

Note: the two Model 801 test wells are calibrated independently. Once calibration check is completed on the first or upper well, simply insert a test tube into the second well, rotate clockwise two complete revolutions, then repeat steps 3 through 6 for the second well.

a. Place the instrument on a flat level surface.

b. Depress the "Prewarm" switch 13 times in rapid succession. the instrument detector sounder will "beep" and FAULT 04 briefly appears on the display screen followed by C-1. The instrument is ready to begin calibrating.

CAUTION: Now is the only time to abort the calibration mode if desired. The entire calibration procedure must be followed once step 3 is performed. To abort the calibration mode, depress the "Prewarm" switch 13 additional times in rapid succession. the instrument will "beep" three times and the timer will begin. Depress the "Start" button to exit the calibration mode.

c. To begin calibration, insert a test tube into the appropriate test well. Rotate the test tube two complete revolutions. Depress the "Start" button. The "-" (hyphen) will now flash. This flashing is common to each of the four calibration steps.

NOTE: If a procedural error is made during calibration, the calibration sequence can be restarted by depressing the "Prewarm" button (channel 1 on Model 801) while the hyphen is flashing.

Once this step is complete, the instrument will "beep" twice and C-2 will appear on the display screen.

d. With the tube still in place, prop up the right side of the instrument at approximately 45° angle. Once the instrument is securely in this position, depress the "Start" button and the second calibration step will begin. At completion, the instrument will "beep" twice and C-3 will appear on the display screen.

e. With the test tube still in place, stand the Hemochron against a flat surface (ie, a wall) so that the instrument is at a 90N angle (perpendicular to the surface). Once the instrument is in position, depress the "Start" button and the third calibration step begins. The instrument will "beep" and C-4 will appear on the display screen.

f. Return the instrument to its correct position. Remove the test tube. Depress the "Start" button to begin the final calibration step. The instrument will "beep" four times upon completion of calibration. A “0” will flash on the display screen. The instrument is ready to perform a coagulation test.

C. Other:

Instrument malfunctions that cannot be corrected by routine maintenance procedures should be referred to the Biomedical Engineering Department or the manufacturer for service. International Technidyne Corporation 1-800-631-5945.

VIII. Quality Assurance:

Quality control results and maintenance is reviewed weekly by a Medical Technologist. Quality assurance reports are completed and distributed monthly to each testing area for review.

IX. Limitations:

The Hemochron ACT tests are affected by poor technique, including specimen collection and test procedure. Inadequate specimen/reagent mixing may result in reduced precision and accuracy. Improper storage of test kits may affect results.

The ACT may be affected by hemodilution, cardioplegic solutions, hypothermia, platelet dysfunction, hypofibrinogenemia, other coagulopathies, and certain medications.

Test results of 600 or more seconds imply a slow rate of fibrin formation. Results greater than 600 seconds should be interpreted qualitatively only. Results of 80 seconds or less generally indicate improper instrument starting technique.

X. Expected Values:

The reference range for ACT is to be established by each patient care area. Generally, a baseline is taken before heparin is given. The ACT is then expected to increase after the dose is given.

This increase depends upon how large the dose is and the duration of the procedure. All ACT test results are put into the patient’s chart and/or appropriate computer system: Sunquest, CareView, or Siemens Cath-Cor. Critical values are up to the assessment of the physician.

XI. Interpretation of Test Results:

Hemochron test results are quantitative indices of the in vitro rate of coagulability of the blood specimen tested. The results may be interpreted by the clinician as an indication of the status of anticoagulant therapy at the time of sample collection.

XII. Linearity:

The linearity of the ACT test is 80-600 seconds. Results out of the reportable range should be reported as <80 or >600 sec.

XIII. Proficiency Testing:

Proficiency testing will be provided by the College of American Pathologists (CAP). Two specimens will be received three times a year for analysis of activated clotting time.

A passing grade is required to maintain proficiency. Only Hemochron operators may perform PT.

Results will be received and reviewed by the Director of Clinical Pathology. Results will be communicated to each department by the Point-of-Care Medical Technologist via the monthly Quality Assurance reports.

XIV. Competency Checks:

Competency checks are performed on each operator during initial inservice and yearly. Observance of incompetency will necessitate re-inservicing and inability to use analyzer until competency is acceptable.

XV. References:

Hemochron Models 401 & 801 Operator's Manual. International Technidyne Corporation. February, 1991.

Hemochron System Instruction and Technical Guide. September, 1983.

Activated Clotting Time by Hemochron CA510/CA510, K-ACT/FTK-ACT, P214/P215, S412, Package Insert. May, 1992.