Revised: 16 December 2005

Safety Information

Malfunction of a Cryosurgical Instrument

Attention:
- CEO District Health Boards
- Colorectal Surgeons
- Dermatologists
- General Practitioners
- Gynaecologists
- Oral and Maxillofacial Surgeons
- Plastic Surgeons
- Sexual Health Clinics

Medsafe has become aware of a patient being seriously injured by the failure of a cryosurgical instrument. Cryosurgical instruments contain a metal probe which reach extremely low temperatures by allowing compressed gas (either nitrous oxide or carbon dioxide) to expand through a valve inside the metal tip of the probe. In this particular case the cryosurgical instrument in which nitrous oxide was used was old and had not been serviced. Difficulty was experienced in stopping the flow of the gas resulting in serious frostbite.

When using this type of cryosurgical instrument it is necessary:

1. for the lines, fittings, seals and probes to be periodically inspected for wear and damage and for the equipment to be serviced regularly;
2. to check that the flow of gas can be controlled by both the "on" and "off" switch on the cryosurgical instrument and also check the regulator attached to the gas cylinder before using the probe on the patient;
3. before every procedure ensure the control mechanism is working by observing that freezing and thawing are occurring at the distal tip of the probe;
4. before every procedure ensure that the exhaust gas from the probe is properly vented. Exposure to nitrous oxide should be kept to a minimum. Modern nitrous oxide cryosurgical units are equipped with scavenging ports.

It is important to be aware that sudden failure of such equipment can lead to serious injury.

Dr Trevor Nisbet
Compliance Team, Medsafe