A single‑use disposable cartridge contains a microfabricated sensor array, a calibrant solution, fluidics system, and a waste chamber. Sensors for analysis of sodium, potassium, chloride, ionized calcium, pH, PCO2, PO2, urea nitrogen (BUN), glucose, and hematocrit are available in a variety of panel configurations (see Table 1). A whole blood sample of approximately 2 to 4 drops is dispensed into the cartridge sample well.
A hand‑held analyzer into which the blood‑filled cartridge is placed for analysis automatically controls all functions of the testing cycle including fluid movement within the cartridge, calibration, and continuous quality monitoring. Analyzers with thermal control capability for testing at 370 C and cartridges requiring thermal control are labeled with a 37° symbol.
A dedicated desktop computer, called the I‑STAT Central Data Station, provides the primary information management capabilities for the I‑STAT System. IR Links allow for transmission of patient records from a widely distributed network of analyzers to the Central Data Station. Data can be stored, organized, edited and transferred to a laboratory information system or other computer.
Sodium, Potassium, Chloride, Ionized Calcium, pH and PCO2 are measured by ion‑selective electrode potentiometry. Concentrations are calculated from the measured potential through the Nernst equation.
Urea is first hydrolyzed to ammonium ions in a reaction catalyzed by the enzyme urease. The ammonium ions are measured by an ion‑selective electrode and the concentration is calculated from the measured potential through the Nernst equation.
Glucose is measured amperometrically. Oxidation of glucose, catalyzed by the enzyme glucose oxidase, produces hydrogen peroxide. The liberated hydrogen peroxide is oxidized at an electrode to produce an electric current which is proportional to the glucose concentration.
PO2 is measured amperometrically. The oxygen sensor is similar to a conventional Clark electrode. Oxygen permeates through a gas permeable membrane from the blood sample into an internal electrolyte solution where it is reduced at the cathode. The oxygen reduction current is proportional to the dissolved oxygen concentration.
Hematocrit is determined conductometrically. The measured conductivity, after correction for electrolyte concentration, is inversely related to the hematocrit.
A. Blood Volume: See Table I above.
B. Specimen Requirements: Verify patient’s identity by looking at the arm band.
Back flush line with sufficient amount of blood to remove intravenous solution, heparin, or medications that may contaminate the sample. Recommendation: three to six times the volume of the catheter, connectors, and needle.
Fill blood gas syringe to the recommended capacity or use the least amount of liquid heparin anticoagulant that will prevent clotting. Underfilling syringes containing liquid heparin will decrease results due to dilution and will decrease ionized calcium results due to binding. For ionized calcium, balanced or low volume heparin blood gas syringes are recommended.
Mix blood and anticoagulant by rolling syringe between palms for at least 5 seconds and then inverting the syringe repeatedly for at least 5 seconds. Avoid or remove immediately any air drawn into syringe to maintain anaerobic conditions. A blood sample should be tested within 10 minutes after it has been obtained (remix before testing).
If a cartridge cannot be filled immediately, collect sample into an evacuated blood collection tube or a syringe containing heparin (sodium, lithium or balanced) anticoagulant. For ionized calcium measurements, balanced heparin or 10 IU/mL of sodium or lithium heparin is recommended. Fill tubes to capacity; fill syringes for correct blood to heparin ratio. Incomplete filling causes higher heparin to blood ratio which will decrease ionized calcium results and may affect other results.
Mix blood and anticoagulant by rolling syringe between palms for at least 5 seconds and then inverting the syringe repeatedly for at least 5 seconds. If possible, test samples immediately after drawn; samples should be tested within 10 minutes (remix before testing).
Wipe away the first drop of blood, which contains excess tissue fluid which can increase potassium result and dilute other test results. Avoid drawing air into capillary tube. Heparinized capillary tubes are not suitable for ionized calcium due to the high concentration of heparin. Use balanced heparin or plain capillary tubes for collection. Test samples immediately to avoid clotting (especially in neonates).
§ Drawing a specimen from an arm with an I.V.
Store the main supply of cartridges at 2 to 8°C. Do not allow cartridges to freeze. Cartridges may be stored at room temperature (18 to 30°C) for 14 days. Cartridges should never be returned to the refrigerator once they have been at room temperature, and should not be exposed to temperatures above 30°C. Mark the calendar on the box to indicate the two week room temperature expiration date. Cartridges should remain in pouches until time of use. All cartridges that require thermal control at 370C should stand at room temperature for four hours before use. Do not use after the labeled expiration date.
§ I-STAT controls, Level 1 and Level 3, are aqueous assayed controls intended to verify the integrity of newly received I-STAT cartridges. Each vial contains 5 ml of an aqueous buffered solution with preservatives, electrolytes, glucose and urea equilibrated with precise mixtures of O2, CO2,, and N2 gases. These solutions do not contain human serum or serum products.
Store at 2 to 80C. Controls can be stored at room temperature (20 to 300C) for 5 days. Do not use beyond the expiration date on the box and ampule labels.
§ Hematronix Meter Trax Controls are assayed controls used to monitor the accuracy and precision of hematocrits on various analyzers, the I-STAT being one of them. Each vial contains 2 ml of stabilized human red blood cells in a buffered medium containing preservatives. This product should be handled with care and considered potentially capable of transmitting infectious disease. Store upright at 2 to 80C. Do not freeze. Once opened vials may be used for 30 days provided they have been resealed and refrigerated immediately after each use. Do not use after expiration date on box and vials. The control vials must be mixed very well each time prior to use.
§ Electronic Simulator: a reusable quality control device that simulates 2 levels of electrical signals which stress the analyzer's signal detection functions. The simulator provides a check on the ability of the analyzer to take accurate and sensitive measurements of voltage, current and resistance from the cartridge. Store at room temperature and protect contact pads from contamination by placing the Electronic Simulator in its protective case.
DIS The display key activated the display screen in order to call the most recently displayed test results to the screen or to access the Menu page.
ENT The enter key is pressed in response to a prompt on the display screen to complete an action.
CLR The clear key erases an incorrect number when entering and identification number. The cursor back one space each time the key is pressed.
0 - 9 The "0" through "9" keys are used for identification numbers, date, time, and to make selections from the menu options.
PRT The print key is used to print selected test records.
* The * key has several functions. It serves as a decimal point, to send data to Central Data Station, exit a page, stop transmission of test records to portable printer.
The two softkeys directly below the display screen are activated by the software when needed. When activated, the soft key's function or label will appear on the bottom of the screen, directly above the key.
PAGE This key is pressed to access additional display screens when certain analyzer functions require more space than a single screen allows.
MENU This key is pressed to access the menu page. From menu, status and stored results can be accessed.
CLKSET This key is pressed to enter the clock-setting function. This key is activated when the Status page is displayed.
Page­ Page¯ Operator can page forward (8) and backward (9) through the 10 pages of stored results.
The Menu page has two numbered options, Status and Stored Results.
Status: Contains information such as date, time, BP, Serial #, battery voltage, # of uses, software version, etc.
Stored Results: 50 test records may be stored in memory. Results can be displayed, printed, or transmitted to Laboratory Information System.
Hewlett-Packard HP 82240B Infrared Printer. Used to obtain a printout of a test record at the point of care. The printer is attached to a cradle in which the I-STAT rests on during transmission. The printer operates on four “AA” batteries.
§ Electrical contact is made with the cartridge.
§ Calibration fluid is released to the sensors.
§ Barometric pressure is measures.
§ Sensors are heated to 370C.
§ Electrical signals generated at the sensors are measure.
§ Calibrant solution is displaced with sample.
§ Electrical signals generated at the sensors are measured.
§ Operator and Patient ID numbers are accepted.
§ Blood gas parameters are accepted.
§ Results are calculated and displayed.
Calibration is automatically performed as part of the test cycle on each cartridge. Therefore, no further calibration procedures, including calibration verification, are required. Every cartridge contains a sealed foil pack which contains a calibrant solution with a known concentration of each analyte. During the first part of the testing cycle, the calibrant solution is automatically forced out of the foil pack and over the sensors. The signals produced by the sensors in response to the calibrant solution are stored. Once this sequence is completed, the analyzer automatically moves the sample over the sensors. By comparing the sensors' response to the sample with that of the calibrant, the concentration of each analyte in the sample is calculated. An error message will be displayed if calibration fails. If calibration fails, patient results will not be displayed and the sample will need to be reanalyzed with a new cartridge.
All cartridges should stand at room temperature for 1 hour before use (an entire box). Individual cartridges can be used after standing just 5 minutes at room temperature.
§ Verify that the cartridges stored in the refrigerator are all within the expiration date printed on the boxes.
§ Verify that the refrigerator did not exceed the limits of 2 to 8°C. If the temperature of the cartridge storage refrigerator is within the range of 2 to 8°C use cartridges as required.
§ If the temperature is outside the range of 2 to 8°C, quarantine the cartridges in the storage refrigerator and do not use.
§ Verify that all boxes of cartridges at room temperature have been out of the refrigerator less than two weeks. Do not use any expired cartridges.
1. Remove the cartridge from its pouch. Avoid touching the contact pads or exerting pressure over the calibrant pack in the center of the cartridge.
2. Direct the dispensing tip or capillary tube containing the blood into the sample well.
3. Dispense the sample until it reaches the FILL TO mark on the cartridge. Leave some sample in the well.
5. Insert the cartridge into the cartridge door until it clicks into place.
6. Enter an operator ID number up to 7 digits. Repeat the process for verification.
7. Enter the patient ID number (6 digit Medical Record #). Repeat the process for verification.
8. Enter the parameters (if required) for cartridges requiring thermal control; Patient temperature can be entered as degrees Centigrade or Fahrenheit. Use the * key for a decimal point. %FIO2 can be entered as the number of liters or as a percentage of the oxygen a patient is receiving.
9. Choose the number corresponding to the type of sample used when prompted at the Sample Type field.
10. Press the SAVE softkey to record the blood gas parameters entered.
11. View results shown on the analyzer's display screen.
The I‑STAT analyzer contains a microprocessor that performs all calculations required for reporting results.
1. Results outside the System's reportable ranges are flagged with a "<" or ">", indicating that the result is below the lower limit or above the upper limit of the reportable range respectively. See the table of Reportable Ranges.
2. Results which are unreportable based on internal QC rejection criteria are flagged with"****". Analyze the specimen again using another cartridge. The results that are not suppressed should be reported in the usual manner.
3. Results will not be reported if a test cycle has a problem with the sample, calibrant solution, sensors, mechanical or electrical functions of the analyzer.
Refer to the I-STAT System Manual's Troubleshooting section.
1. Place the analyzer in the cradle of an IR Interface, IR Link or IR Cradle. Turn the printer on (printer light green) or press the paper advance switch to reactivate.
2. To print the displayed test record, press the PRT key on the analyzer.
3. Do not move the analyzer while "Printing" is displayed.
Note: Results printed on thermal paper will fade with time and are therefore not acceptable as a permanent chartable record.
4. Write the patient's name on the "Pt name line" and the physician's name on the Physician line.
1. Place the analyzer in the cradle of an IR Interface or Link. The IR status light must be green.
2. To transmit the displayed test record, press the * key.
3. To transmit all stored test records, access STORED RESULTS from the menu. Press the "3" key on the analyzer to transmit all test records.
4. Do not move the analyzer while "Transmitting" is displayed. During transmission the IR Status light will blink alternately red and green. If transmission is successful, the IR Link will emit a single high pitched beep and the light will return to green. An unsuccessful transmission is indicated by three low tone beeps. In this case repeat the transmission process. If unsuccessful the second time, notify the point-of-care coordinator at pager #0616.
5. Successful transmissions will automatically be sent to Sunquest, the Laboratory Information System. Billing will occur simultaneously.
C. Anesthesiologists performing analysis will receive results in 2 minutes. Anesthesiologists who order the test but do not perform the analysis, will receive all results within 5 minutes.
Traditional quality control methods, based on analysis of controls in every "run" of patient samples, were designed to detect persistent changes in performance of multiple-use analytical systems which deteriorate with time or usage. However, in a single-use analytical system such as the I-STAT, the analytical units are not reused and subject to deterioration caused by previous samples or reagents. Each new cartridge presents a fresh analytical path for each specimen. A homogenous batch of I-STAT cartridges, verified when newly received and stored properly thereafter, will retain its collective performance at least until its expiration date.
1.Verify the performance of each analyzer in the I-STAT system using the Electronic Simulator every 8 hours of use. The SIM message will appear as a reminder if 8 hours have elapsed since the last electronic simulator test.
§ Remove the Electronic Simulator after the LCK message disappears from the display screen.
§ Transmit the result to the Central Data Station.
§ Use the analyzer as required.
§ Record the failure in the I-STAT System Electronic Simulator Action Log (See attached).
§ .Repeat the procedure with the same Electronic Simulator.
§ If code "L" appears with failure, this may be an indication that moisture may be on the internal connector. In this case, allow the analyzer to sit for half an hour to allow the moisture to evaporate, then insert Electronic Simulator again.
§ If failure still occurs, call the point-of-care coordinator at pager 4431 or ext. 4431 first. If she/he is not available, call the I-STAT technical service at 1-800-366-8020.
§ Do not use analyzer if simulator fails.
Print Electronic Simulator results using the trend function on the Central Data Station.
§ I‑STAT cartridges are shipped refrigerated with a four window indicator to monitor temperature during transit.
§ Fill out the record of receipt and forward materials to refrigerator.
§ If all windows are white or if only the "A" window is blue, then transit temperatures were satisfactory.
§ If any or all of the "B", "C", or "D" windows are blue, quarantine the suspect cartons and notify the point-of-care coordinator immediately.
§ DO NOT USE cartridges from the suspect cartons.
§ Record the out of control event in the I‑STAT QC Log (See attached).
§ From each lot of cartridges received, analyze I‑STAT Level 1 and 3 and Meter Trax Low and High controls each in duplicate, using any verified analyzer. Transmit the results to the Central Data Station.
§ Use the expected values published in the package inserts to verify the integrity of the cartridges.
a. Remove I-STAT ampule(s), Metertrax controls and cartridge(s) from the refrigerator and allow all to come to room temperature (approximately 30 minutes). Tap the tip of the ampule to send any solution back into body. Carefully snap off the neck of the ampule and draw solution from the body of the ampule using a fresh capillary tube or sterile 1‑3cc syringe with 20 gauge needle. Expel approximately one or two drops of solution into cartridge until solution reaches the fill to line on the cartridge. Close the cartridge and insert into the analyzer. Metertrax controls are to be mixed very well prior to use and are dispensed directly into the cartridge.
b. The contents of one ampule may be used to fill more than one cartridge as long as it is used within 10 minutes of opening. Always use a fresh syringe or capillary tube for each level of solution.
d. Compare results to the package insert values. Check that the lot number on the control ampule matches the lot number on the package insert, and that the software version listed on the insert matches the software installed in the analyzer. If all results are within expected ranges use the cartridges as needed.
e. Record all results on the I-STAT System QC Log.
f. Transmit the results to the Central Data Station.
a. Remove I-STAT QC ampule(s) and cartridge(s) and Metertrax controls from the refrigerator and allow to come to room temperature (minimum 4 hours for ampule(s) and cartridges).
b. Shake the ampule vigorously for 10 seconds to equilibrate the liquid and gas phases. Tap the top of the ampule to send any solution back into body.
c. Carefully snap off the neck of the ampule, and immediately draw solution from the body of the ampule using a fresh capillary tube or sterile 1‑3cc syringe with 20 gauge needle. It is important not to expose the solution to room air since this will alter the results. If air is trapped near the plunger, do not invert the syringe to expel it; this air will not affect solution to be used at the tip of the syringe. If bubbles are continually drawn in the syringe and near the tip, discard and use a fresh ampule and syringe.
d. Expel two drops from the syringe or capillary tube into a gauze pad. Then place two to four drops of the solution into the cartridge. Be sure that the solution reaches the FILL TO line. Metertrax controls are to be mixed very well prior to use and are dispensed directly into the cartridges.
e. Close the cartridge and insert into the analyzer. Use one ampule for each cartridge to be tested. An ampule should not be used more than once.
h. Compare results to the package insert values. Check that the lot number on the control ampule matches the lot number on the package insert and that the software version listed on the insert matches the software installed in the analyzer. If all results are within expected ranges use the cartridges as needed.
i. Record all results on I-STAT System QC log.
j. Transmit the results to the Central Data Station.
§ DO NOT USE cartridges from the suspect lot.
§ Quarantine the suspect lot.
§ Notify the point-of-care coordinator immediately.
§ Record the QC failure in the I‑STAT QC Action Log along with the action taken.
The I-STAT Corporation suggests that Calibration Verification is not required because each I-STAT cartridge contains a calibrant solution and therefore, the requirement by CLIA for a calibration procedure is met each time a cartridge is run.
Competency checks will be performed on each operator annually by a representative from the I-STAT Corp, the Coordinator of Point-of-Care Testing, or the Anesthesia Nurse Coordinator.
Proficiency testing will be provided by CAP. The survey performed on the EG6+, EG7+ and G cartridges will be the Aqueous Blood Gas (AQ) survey which provides five challenges three times per year. PT will be performed by routine operators.
Results will be received and reviewed by the Director of Clinical Pathology. Results will be communicated to the anesthesia department via the Point-of-Care Coordinator.
Correlations of a whole blood sample will be performed on the I-STAT and on an analyzer of different methodologies every 6 months. Tonometry of EQUIL has proven not to work on the I-STAT.
Fundamentals of Clinical Chemistry, N. Tietz, Third Edition, Pages :426-435, 614-616, and 676-678.
Clinical Chemistry Theory, Analysis & Correlation, Kaplan/Pesce, Second Edition, Pages 850-856, 872-875, 884-888, and 1021-1024.
Barry A. Shapiro, M.D., William T. Peruzzi, M.D., Rozanna Kozelowski-Templin, C-C.P.T., C.P.F.T.: Clinical Applications of Blood Gases, 5th Ed., 1994, p.55-65.