The Anesthesia Gas Machine
Last updated July 2012. Comments or
criticism to the author at:
Click on the headings in the table of contents for this page and you will be taken directly to each section.
The Anesthesia Gas Machine is a large, current, full-text, illustrated, comprehensive treatment of all aspects, from the University of Detroit Mercy. Last revised July 2012. It covers gas supply, the internal pneumatics and other processing, delivery to the patient (circuits, ventilators), disposal (scavenging systems), an extensive section on the gas machine checklist, vaporization, compressed gases, and a variety of smaller topics (malignant hyperthermia, medical legal, etc.). The last portion is a "Test Yourself", which covers selected clinical implications in a question and answer format. By the author of the chapter on equipment in Nagelhout and Plaus (Eds.) Nurse Anesthesia 5th ed. in press 2012.
Third World Anesthesia by ST Brown CRNA is older, but a good general discussion of considerations for mission anesthesia overseas. Anaesthesia services in developing countries: defining the problems, from SC Hodges et al (Anaesthesia, 2007, 62, pages 4–11) is similar. Pediatric anesthesia in developing countries (AT Bosenberg, Curr Opin Anaesthesiol 2007;20:204–210) discusses special problems in anesthetizing children.
Military Anesthesia Machines is a book chapter of interest even for those who may never use equipment under wartime or mobile army surgical hospital conditions. It contains the Ohmeda 885A description and safety review, Vernitrol vaporizer theory & use, and references.
Drager Medical- Anesthesia Workstations showcases new products such as Apollo, Tiro, and Fabius gas machines. The GE Medical site has an overview of GE gas machines, including Aisys, Avance, Aestiva and Aespire, and gives some details of their features. Paragon Services offers the Platinum and Mindray gas machines.
Checklists and Pre-Use checkout of the anesthesia gas machine are covered in several places. The checklist given at Anesthesia Apparatus Checkout Procedure, does not correspond to the current Pre-Anesthesia Checklist (2008). However, it has a unique and useful feature: giving potential faults the user might discover while checking each component. The University of Michigan checkout has color photos of the Narkomed 2B, and is well-presented. It dates from 1994. Putting it all together- Checklist, Medicolegal, Cleaning and Sterilization (a subset of the overview mentioned earlier on this page) discusses the current Pre-Anesthesia Checklist (2008). It also has a section which presents a minimum checklist (when time to check the machine is not available), a checklist for older gas machines, and a modified checklist designed to eliminate common faults (and a few helpful reminders). Finally, Dr J. Andrews (author of equipment chapters in texts edited by Miller et al. and Barash et al.) writes a helpful article on Troubleshooting the anesthesia gas machine, which in part addresses checkout.
The last few years have seen a revolutionary change in a component of gas machines whose formulation dates to the First Word War- soda lime carbon dioxide absorption. Because the methyl ethyl ethers (desflurane, enflurane, isoflurane) break down to carbon monoxide, and sevoflurane produces a toxic breakdown product (Compound A) in dry soda lime or barium hydroxide lime, research has focused on the clinical significance of the problem, and potential solutions. Since 2000, a potential solution has been found in the form of a change in carbon dioxide absorption granule formulation- elimination of the "activators" (strong bases sodium and potassium hydroxide).
Baralyme has been withdrawn in Aug 2004: "Allied Healthcare Products, Inc. (NASDAQ NM : AHPI) filed an 8-K on 8/30, in which the Company reported that on 8/27, it entered into an agreement with Abbott Laboratories pursuant to which Allied will cease production of its product Baralyme(R), will, within sixty days, effect the withdrawal of Baralyme(R) product held by distributors and will pursue the development of a new carbon dioxide absorbent product."
Read more by searching for "soda lime" in Anesthesiology or Anesthesia and Analgesia.
Low Flow and Closed circuit Anesthesia is a powerpoint with information from an expert in these techniques (the author of GasMan software).
Michael Olympio offers a fascinating analysis of the effect of new gas machine designs on patient safety at Modern Anesthesia Machines Offer New Safety Features. The Low-Pressure Alarm Condition: Safety Considerations and the Anesthesiologist's Response gives an algorithm and detailed analysis for troubleshooting leaks.
The Oklahoma State University Safety Library: Compressed gases links to many government, university, and manufacturer's documents. Medical gas contamination, especially as supplied by pipelines, is a continuing source of mortality and morbidity. See JCAHO Sentinel Alert: Medical gas mix-ups which reports on two deaths and five injuries occurring in 2000.
A Bibliography on equipment and liability is an index to several worthwhile articles on this topic. Also at that site is an ASA Newsletter article by Kaplan, which contains data on equipment problems, and how they impact patient safety.
The Malignant Hyperthermia Association of the US (MHAUS) contains several worthwhile items. Click For healthcare professionals which gives a quick overview of emergency procedures for an MH crisis. Scroll down to the FAQ, which discusses anesthesia machine preparation for the MH-susceptible patient. Using breathing circuits and ventilators has a section discussing the equipment implications of malignant hyperthermia.
ASTM lists the scope and subcommittees of Committee F-29 on Anesthetic and Respiratory Equipment, also refers to the standards writing process and gives contact information. The current (F1850-2005) standard for anesthesia workstations is available for purchase there. ASA standards relating to Pre and Post Anesthesia care, and Intraoperative Monitoring standards have equipment implications.
GasMan is a commercial product which allows one to simulate and experiment with anesthesia delivery systems. One can vary fresh gas flow, minute ventilation, circuit type, patient body habitus, cardiac output, vaporizer settings, and other parameters, while observing the effects on volatile agent uptake and distribution (in several body compartments), excretion, and cost. Fascinating and worthwhile (but not free).
A "virtual anesthesia machine" is an animated gas machine illustration on computer screen, which is modifiable when the user selects different gas flows, vapor concentrations, etc. It requires Shockwave, or there is a downloadable version.
The Review of Currently Used Inhalation Anesthetics Part I has some implications for equipment and how it is used. Part II has good pictures and descriptions of several topics including how to fill vaporizers.
OSHA posts a collection of links on WAGs. There is a very comprehensive document available for download via a link at Waste anesthesia gases.
This page is one chapter of many in the Virtual Anaesthesia Textbook. Please direct all comments about the organisation of this chapter, corrections to links, and suggestions for additions to: Michael Dosch CRNA PhD, Associate Professor and Chair of Nurse Anesthesia, University of Detroit Mercy
Questions about the Virtual Anaesthesia Textbook project itself should be e-mailed to Chris Thompson.