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Cardiac Freezer SOP

Homograft Storage Equipment ("Cardiac Freezer") Maintenance, Alarm Response, and
Record-Keeping Procedures

Section A - Summary
Section B - Notifications
Section C - MGH Contact Information
Section D - Performance Log Construction & Maintenance
Section E – Responding to Alarms
Section F - Protection when working near Liquid Nitrogen
Section G - Maintenance Schedule
Section H – Back Up Freezer & Homograft Transfers
Section I - Alarm Troubleshooting
Section J - Vendor Contact Information

A: Summary

Anesthesia Clinical Engineering’s (ACE) responsibility is to ensure the freezer’s maintenance schedule is met as well as to respond to all cardiac freezer alarms. Accurate documentation of each maintenance activity must be recorded in the Biomedical database. For maintenance, all work performed must be accurately captured using MGH Biomedical Engineering standards. A work order should also be opened for each time you respond to an alarm. ACE will verify the integrity of the freezer’s performance following each state of alarm. Furthermore, ACE will have the responsibility of contributing this work order information to a second database which is managed by the OR Administration.

B: Notifications

Notifications: If ANY member of the hospital staff senses the contents of the freezer may have been compromised, at any time, then notify all parties and Anesthesia Clinical Engineering will assist in the determination of the freezer’s performance.

Normal freezer operating set points are: for temperature, between –196 and –190 Celsius degrees. In the event that the freezer’s internal temperature is not in that range (or suspicion of), Anesthesia Clinical Engineering, or any person, must notify Cardiac Nursing & OR Administration immediately. The contents of the freezer should be considered unusable until an investigation can be completed.

Normal freezer operating set points are: for liquid nitrogen level, between 9 and 12 inches of liquid. In the case that the liquid level has risen and been maintained above 13 inches or more, the contents of the freezer may have become submersed in the liquid nitrogen. Anesthesia Clinical Engineering, or any person, must notify Cardiac Nursing & OR Administration immediately.

C: MGH Contact Information

Buildings & Grounds (6-2422)
Cardiac Nursing (via Gray Desk 6-8910 or pager ID 22022)
OR Admin: 6-1852, pager ID 25812, emergency 781-848-1587
OR Admin (for log data): 6-0581, 6-9032, emergency 617-516-0761
Anesthesia Clinical Engineering: (6-3173, pager ID 24811)
Safety Office: (6-2425, pager ID 26517)

D: Performance Log Construction and Maintenance

The freezer’s system monitor creates an “event log”. This event log is the basis for the Freezer Performance Log. OR Administration will retrieve the freezer’s event log on a scheduled basis (or at the request of Anesthesia Clinical Engineering in the course of an investigation) and add these files to its database. ACE will add documentation to this database on all alarms and maintenance. Therefore, the database data is an integral part of the Freezer Performance Log.

When completing a work order, please include the following details. Please set the DATE OPENED field to the correct calendar day of the alarm notification. In the Requested by field, put in the how and when the alarm was received, (e.g. “Page from B&G @4:30 a.m.). Record these items in the Request field of the work order: the alarm message from the freezer’s display (if functional) and record the two temperature readings and the liquid nitrogen level as found. Be sure to detail actions taken to resolve the alarm. Do NOT close out or lock any work orders until they can be reviewed.

E: Responding to Alarms

Anesthesia Clinical Engineering should be notified for all alarm conditions. During nights and weekend hours, the primary source for an alarm notification will be from Buildings & Grounds. B&G will not have detail on the nature of the alarm because they only receive a general alarm signal (any alarm condition). When they receive the alarm, they will alert the on-call technician through the paging system (24811). The on-call technician should call B&G (726-2422) and verify receipt of the page, stating their name and expected time of response.

F: Protection and Handling Liquid Nitrogen

Liquid Nitrogen (LN2) is a potential asphyxiate and may cause severe frostbite. DO NOT enter the area unless it has adequate ventilation, especially if there appears to be a leak. DO NOT touch frosted pipes or valves. Always wear protective gear to protect the eyes and skin from liquid or cold gas from accidental contact. In the event of a liquid nitrogen spill or leak, clear people from the area & contact the Safety office (6-2425, on call pager 26517) and Anesthesia Clinical Engineering (6-3173), on call pager 24811.

G: Maintenance Schedule

The maintenance schedule for the freezer will follow the manufacturer’s schedule as defined in section 6 of the XLC TEC 2000 System Monitor’s user manual. If the freezer needs to be shutdown for a maintenance event, scheduled or unscheduled, notify Cardiac Nursing & OR Administration. Only Cardiac nursing is trained to handle & administrate the freezer’s contents. ACE will also verify that the UPS that supplies back up power follows its maintenance schedule.

H: Back Up Freezer and Homograft Transfers

The back-up freezer is a Chart/MVE model 230F. Its serial number is CEUF02J104.
When you require the freezer’s contents to be transferred to or from the back up system, notify Cardiac Nursing. The circulating nurse is trained on the safe handling of the homografts and all the administrative procedures that must be followed.

I: Alarm Troubleshooting

1) No Display. In the event that there is no readout on the freezer’s monitor display, check all electrical connections. This unit is not equipped with a battery back up, but is powered through a UPS (located behind the desk). If the monitor/display function cannot be restored, then LN2 level measurements must be checked manually, using the yardstick located on the wall behind the freezer. This operation will be performed twice daily until functionality is restored. Open a work order and record your measurements for each day this needs to be performed. (See also Power Failure alarm in the Alarm Troubleshooting section)

2) Supply (Tank) Alarm. The freezer controller triggers a fill event when the freezer liquid level drops to 9 inches of liquid. This alarm means that the freezer has attempted to add LN2 to the freezer but was unable to reach the fill level of 12 inches of liquid (within the default time of 60 minutes). The consumption rate of liquid is approximately 1.1” per day. One inch of liquid represents approximately 8 liters, so a near empty tank will trigger this alarm if it cannot provide an additional 3 inches of liquid.

To determine the amount of Liquid Nitrogen in the tank refer to the level indicator on the top of the tank. It may be a gauge or a float type indicator. If you determine that the tank is empty and the freezer liquid level is too low, call the supplier (see above) for an emergency shipment, using the customer number, the item number, the location it’s to be delivered to, and a phone number where you can be reached. For liability reasons, it is likely you will need to connect the new supply tank yourself.

3) Low Level Alarm. This is triggered when the freezer liquid level has fallen below 8 inches of liquid. Normally this would occur well after the SUPPLY ALARM has already occurred, and it can be handled in the same manner. Verify the actual liquid level using the yardstick if you suspect that the reading is incorrect. If the supply tank is in good order (and open) then perhaps the freezer’s fill valve has failed to open. Try to raise the liquid level in the freezer by use the fill function (the FILL START button). If this top off method does not raise the liquid level, then press and hold the manual fill pushbutton located on the back panel of the freezer. This should operate the fill valve as long as there is power to the unit. Power is provided by 120 VAC and should be utilizing a red plated emergency branch circuit. On the older freezer, power is provided through a 24VAC step down transformer which is backed up by a UPS.

4) High Level Alarm. This is triggered when the freezer liquid level has risen above 13 inches of liquid. Occasionally this alarm might occur whenever the freezer liquid is caused to slosh around due to impact or the end of a fill cycle, in which case it is only a nuisance. However, if the liquid level is above 13 inches and continues to rise, than it may be caused by a faulty fill valve. If it is safe to do so, close the supply tank immediately. If a spill due to overflow has already occurred, notify the Safety Department (6-2425) and clear all hospital staff out of the vicinity. Nothing else can be done until the LN2 has evaporated.

5) Low Temperature Alarm (A or B). Technically speaking, there is no such thing as too low a temperature for this system. Chances are the temperature probe (RTD) has malfunctioned. Verify the condition by comparing to the other probe (A or B).

6) High Temperature or Open Temperature Alarm (A or B). Normally the high temperature alarm would only occur after a number of other alarms had occurred. Verify the condition by comparing to the other probe (A or B). If liquid nitrogen is present in the freezer, chances are the temperature probe (RTD) has malfunctioned, failed opened or been disconnected. This should be attended to as soon as practical, because the temperature log is central to the recordkeeping on the health & condition of the homografts being stored. If a high temperature condition is found to be true, notify OR Administration and Cardiac Nursing immediately. The condition of the homografts may have been compromised. The data log will have to be viewed as soon as practical.

7) Power Failure Alarm. This unit does not have battery back-up and therefore this alarm will not be displayed unless the UPS system it is plugged into is functional. If you find the unit’s display is blank, verify power connections. If you are unable to re-power the display, then verify liquid level using the yardstick method and if necessary add more LN2 with the manual fill button on the back panel. If that energizes then only the controller has failed. Notify the local representative.

8) Fill Valve Alarm. Normally this alarm would only occur after a High Level Alarm had occurred. The controller is sensing that the fill valve is still in an open condition and that the liquid level has gone above the High Level setting. Close off the tank supply if it is safe to do so.

J: Vendor Contacts

Freezer Manufacturer: Chart/MVE. The model number is MVE 600F. The part number is 11499661. The serial number is CEVN06B103. The local representative is Ron Gonthier (617-780-5460). Technical support can be reached at 770-720-3764. There is no emergency service available. The Control Numbers for the freezer is 1051795. The B&G identifiers is 7272.

Liquid Nitrogen Supplier: Airgas East (866-718-0685). They provide 24 -hour service. Our customer/account number is B8N47. The liquid nitrogen product that the system uses is identified by item number (NI 230LT22). It is a 230 liter container, and is vented at 22 PSI.

Added to site: July, 2007
Document owner: Brian Lee

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This page was last updated on 10/7/2014