[Leakage in anesthesia circuits--a comparison between 1998 and 2005 investigations].

BACKGROUND: We checked for the occurrence of any leakage in an anesthesia circuit to estimate the present situation of airtightness of an anesthesia circuit in 55 anesthesia machines at various medical institutions in Okinawa. METHODS: Leakage was detected and measured by a leak checker. RESULTS: A certain degree of leakage was found in 28 of the anesthesia machines (51%). The average and maximal amounts of leakage in the anesthesia machines were 0.26, and 1.29 l x min(-1), respectively. Thirty-eight of anesthesia machines met the standards of a low flow leak test (69%). The average and maximal amounts of leakage in the inside circuit were 0.02, and 0.20 l x min(-1), respectively. The leak points of the inside circuit were present in a unidirectional valve for an oxygen sensor (14%) and for unknown reason (7%). The average and maximal amounts of leakage in the outside circuit were 0.24, and 1.29 l x min(-1), respectively. Leak points in the inside circuit were found in the corrugated breathing tube (82%) and canister (32%). CONCLUSIONS: Most instances of leakage of the above described anesthesia circuits were identified in the corrugated breathing tube and canister. As a result of our findings, we strongly recommend that these parts be checked very carefully during pre-anesthetic leak tests.

Aberrant halt of syringe pump motion: an improved system to prevent false setting of the syringe.

A syringe pump is used to inject precise doses of drugs having a strong action; for example, vasoactive drugs. Unexpected and undetected halt of a syringe pump can lead to potentially life-threatening complications. We experienced a sudden halt in the movement of a syringe pump (Terufusion syringe pump; Terumo, Tokyo, Japan) in two patients while administering norepinephrine in the intensive care unit (ICU). Fortunately, the patients had only transient hypotension, which was immediately detected and promptly treated, without any untoward sequelae. As a result of the occurrence of such cases, we conducted a detailed investigation of the causes of this sudden halt in the syringe pump. We could not reproduce the aberration of the syringe pump and thus could not specify the cause in the first patient. In the second patient, however, a false setting on the syringe was suspected to be the cause of the problem. In order to prove this, we tried to reproduce the situation where a syringe pump, due to a false syringe setting, abruptly terminated while giving a "syringe loss" warning, after a period of precise functioning. Once we had determined how a false setting of the syringe could occur without the syringe pump giving off an alarm from the onset, we collaborated with the Terumo Company to revise their current instruction manual to incorporate this as a warning. We also helped in the development of a new model, including a new safety feature that would prevent a false setting of the syringe from occurring at all. This new model was released in December 2003.

Non-zero basal oxygen flow a hazard to anesthesia breathing circuit leak test.

The non-zero basal flow (BF) of oxygen in anesthesia machines has been set to supply the basal metabolic requirement of oxygen. However, there is no scientific evidence of its necessity. In this study we sought to clarify whether non-zero BF affects leak detection during preanesthetic inspections. Twenty-five participants performed leak tests on anesthesia machines to detect breathing circuit leaks. Artificial leak-producing devices were used to create leaks from 0 to 1.0 L/min. The investigator randomly chose the leak device and connected it into the breathing circuit. Participants, blinded as to the presence or the type of leak producing device, then tested the breathing circuit for leaks. The conventional breathing system leak test was performed with and without BF. The results of leak detection in each leak procedure were analyzed statistically. The leak detection rate of leak test with BF was less than without BF (P < 0.01). We demonstrated that non-zero BF of oxygen decreases the leak detection rate and is an obstacle for leak detection, especially for small leaks. Therefore, we recommend that breathing circuit leak tests should be performed in the absence of BF of oxygen.