Printer Friendly

Transient sevoflurane output failure in a Datum vaporiser with concurrent foreign body.

We recently encountered a transient loss of output from a Blease Datum The singular form of data; for example, one datum. It is rarely used, and data, its plural form, is commonly used for both singular and plural.  sevoflurane vaporiser Noun 1. vaporiser - a device that puts out a substance in the form of a vapor (especially for medicinal inhalation)
vaporizer

device - an instrumentality invented for a particular purpose; "the device is small enough to wear on your wrist"; "a device
 (Spacelabs, Issaquah, USA) during surgery for insertion of prostatic brachytherapy rods. Following an uncomplicated intravenous induction, sevoflurane was introduced at 3% via an Aestiva/5 anaesthetic machine (Datex-Ohmeda, GE Healthcare, Bucks, UK). Shortly after the initial normal increase at flows of 4 l/minute, the end-tidal sevoflurane concentration was noted to drop rapidly from 1.6% to 1.1%. We increased the dialled settings. The inspired sevoflurane fraction continued to decrease despite a dialled percentage of up to 8% and oxygen flow of 8 l/minute. Over the next 45 seconds the inspired fraction decreased further to 0.6%. A check of the vaporiser reservoir indicator window showed a small yellow foreign body had appeared (Figure 1). At the same time, the inspired fraction began to rise rapidly, allowing us to decrease gas flows and dialled percentage to the original settings. The foreign body was not present during the preoperative pre·op·er·a·tive
adj.
Preceding a surgical operation.



preoperative

preceding an operation.


preoperative care
the preparation of a patient before operation.
 equipment check.

The vaporiser in question is leased by Abbott Australasia Pty Ltd (Botany, NSW NSW New South Wales

Noun 1. NSW - the agency that provides units to conduct unconventional and counter-guerilla warfare
Naval Special Warfare
), the supplier of sevoflurane. The service agents for the vaporiser are General Anaesthetic Services Australia (Adelaide, SA). When the service agents dismantled the vaporiser, they confirmed that the foreign body, 6x1 mm, was most likely a fragment of plastic material from the cap on a sevoflurane bottle. They reported that it is not uncommon to observe fragments of yellow plastic in similar, but normally functioning, vaporisers returned for routine service. The vaporiser was noted to be under-delivering by 20% across all gas flows, but this did not explain the precipitous decline in inspired gas. Two bench top tests using introduced plastic shavings failed to replicate a sudden drop in output. The vaporiser was also assessed by the manufacturers and found to be functioning within normal tolerance. They found two more plastic shavings and felt these were unrelated to the apparent output failure.

Sevoflurane bottles have a tamper proof cap. When the tamper proof cap is unscrewed for the first time it separates via perforations from a plastic collar. This is a potential source of a foreign body, but there was no obvious defect in the plastic on the bottle most recently used Most Recently Used (MRU) may refer to:
  • A specific menu in Microsoft Windows, see Common menus in Microsoft Windows
  • An uncommon method of caching disk access, see Cache algorithms
 to refill the vaporiser. The Blease Datum vaporiser has an upward pointing port for connection of the sevoflurane bottle, which may promote inadvertent contamination with foreign material. A foreign body may fall in when the filling port cap is removed and be washed in unnoticed as the bottle is connected. In contrast, the Desflurane Tec 6 (Datex-Ohmeda, Wisconsin, USA) has a filling port that faces downward and is then inverted when the bottle is connected.

We were concerned the sudden drop in inspired sevoflurane represented a temporary blockage which resolved when the plastic sliver dislodged to appear in the sight glass. However, on examining a diagram of the vaporiser's internal components it is hard to see how such a small sliver could have interrupted gas flow.

[FIGURE 1 OMITTED]

There are no reported cases of vaporiser malfunction caused by a foreign body. Of the few reports of delivery failure, most were detected following the patient's physiological response to lack of anaesthesia anaesthesia

anesthesia.
 (13). Given the short duration of apparent delivery failure in this case, it may have passed unnoticed had it not been for gas analysis and vigilance. Loss of anaesthetic delivery risks awareness and potential patient movement. Decreased inspired volatile concentration is detected only by regular observation of the monitor. Appropriately set volatile concentration alarms may be considered, but these are generally unhelpful during induction and emergence from general anaesthesia. Alternatively, some vaporisers, like the Desflurane Tec 6 have 'no output' alarms that could alert one to failure sooner.

We cannot conclusively state the foreign body caused the output failure. We have considered other causes. Transient entrainment entrainment /en·train·ment/ (en-tran´ment)
1. a technique for identifying the slowest pacing necessary to terminate an arrhythmia, particularly atrial flutter.

2.
 of room air could cause a dilution of sevoflurane but this is unlikely in a ventilated patient. We cannot exclude transient failure of gas analysis, but the pattern of progressive decline in inspired and expired gases and then gradual increase was more in keeping with a temporary output failure. When we have experienced fluctuations in gas analysis previously, they have tended to be sudden and short lived. We would be interested to hear if anyone else has experienced a similar apparent output failure and any possible explanations. However, foreign bodies within vaporisers are not ideal. When filling Datum vaporisers, anaesthetists and technicians should take care to check the port to ensure there are no foreign bodies that could be washed in. Vaporiser designers could consider similar filling strategies to the Desflurane Tec 6 in order to reduce the chance of this problem occurring.

J. A. PENNEY

G. HOCKING Hocking may refer to:
  • Hocking County, Ohio
  • Hocking Hills in Ohio
  • Hocking College in Ohio
  • Hocking River in Ohio
  • William Ernest Hocking, American Idealist philosopher
 

W. M. WEIGHTMAN

Perth, Western Australia This article is about the metropolitan area of Perth, Western Australia. For the local government area, see City of Perth.
Perth is the capital of the Australian state of Western Australia.
 

References

(1.) Fernando PM, Peck DJ. An uncommon cause of vaporiser failure. Anaesthesia 2001; 56:1009-1010.

(2.) MacLeod DM, McEvoy L, Walker D. Report of vaporiser malfunction. Anaesthesia 2002; 57:299-300.

(3.) Kimatian SJ. With technology comes responsibility: intraoperative failure of an anesthetic vaporizer. Anesthesiology 2002; 96:1533-1534.
COPYRIGHT 2011 Australian Society of Anaesthetists
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2011 Gale, Cengage Learning. All rights reserved.

 Reader Opinion

Title:

Comment:



 

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Correspondence
Author:Penney, J.A.; Hocking, G.; Weightman, W.M.
Publication:Anaesthesia and Intensive Care
Geographic Code:8AUST
Date:Mar 1, 2011
Words:840
Previous Article:Anomalous positioning of femoral artery and vein even 'constant' landmarks can be inconsistent.
Next Article:Telemonitoring made easy and inexpensive.
Topics:

Terms of use | Copyright © 2014 Farlex, Inc. | Feedback | For webmasters