ASA Panel Reports Risks
It has been estimated that only one in ten to one in one hundred operating room fires is reported. The exact incidence is therefore unknown. By “guesstimate,” there are probably between one hundred and two hundred operating room fires in the United States per year, as gleaned from FDA reports and ECRI investigations. Approximately 20% of those reported fires result in serious patient injury. The one or two deaths per year are usually secondary to airway fire. Most operating room fires are associated with an oxygen enriched atmosphere which may also include nitrous oxide.
At the ASA Annual Meeting in Dallas in October, there was a Panel presentation entitled “Fire in the Operating Room! Still a Problem” moderated by Gerald L. Wolf, M.D. from SUNY, Brooklyn. Panelists included Carol Hirshman, M.D. from the College of Physicians and Surgeons of Columbia University, George W. Sidebotham, Ph.D., from the Albert Nerken School of Engineering of The Cooper Union for the Advancement of Science and Art, Frederick W. Williams, Ph.D., Director, Navy Technology Center for Safety and Survivability of the Naval Research Laboratory and Daniel E. Supkis, Jr., M.D., from the Division of Anesthesiology and Critical Care of the MD Anderson Cancer Center, Houston.
Dr. Hirshman discussed various reported operating room fire events published in the medical literature and lay press. She reinforced that these are no longer flammable anesthetic agent fires since halogenation of hydrocarbon anesthetics has made modern anesthetics nonflammable. Included in her discussion were examples of surgical drape fires ignited by the electrosurgical unit in the oxygen enriched atmosphere common to operating rooms, particularly in the area of the head and neck. Also discussed were cases of surgical drape fires ignited by lasers.
Endotracheal tube fires, the most lethal, were also presented in detail. These included electrosurgical ignition of the endotracheal tube in an oxygen- enriched atmosphere during tracheostomy and tonsillectomy. The polyvinyl chloride tube ignition during tracheostomy occurs when the electrosurgical unit is used to incise the pretracheal fascia and trachea, or during cauterization of trachea edge bleeders at the tracheal incision site. Laser ignition of endotracheal tubes during laryngeal surgery was discussed, including ignition of “laser resistant” endotracheal tubes. A report of a laser igniting a surgeon’s glove during jet ventilation was mentioned. Intestinal gas fires and explosions, ignited by an electrosurgical unit or laser were also outlined as significant, potentially lethal, problems.
Prof. Sidebotham reviewed some aspects of combustion science particularly related to the operating room environment. He discussed the three legs of the fire triangle which are required for a fire: the oxidizer, the ignition source, and the fuel. A fire cannot occur if one of these components is absent. A fire may occur if all the physical and chemical factors are present. Air, compressed air, oxygen and nitrous oxide are the oxidizers in the typical operating room. There are many ignition sources, including especially the electrosurgical unit and laser. Potential fuels commonly present include surgical drapes, endotracheal tubes, and alcohol-based prep solutions. A fire is possible when the three legs are present in “appropriate” (combustible) chemical and physical configurations.
Endotracheal tube fires are typically composed of an intraluminal flame traveling along the inner surface of the tube toward the flow of oxidizer and a secondary flame anchored at the downstream end of the tube. The heat from the intraluminal flame vaporizes volatile combustible products from the downstream tube wall that become the fuel for the secondary flame that can shoot out the internal end of an endotracheal tube like a blowtorch, causing massive airway damage.
Dr. Williams reviewed the U.S. Navy’s approach to fire safety. Two categories of fire safety were discussed, the passive and active approaches. The passive approach implies minimizing the chance of and damage from a fire by careful assessment and adjustment/regulation of the available fuel load. Decisions, for example: choice of a mattress, are made by balancing comfort and the contribution of the mattress to the total fuel load present in a given environment. Another passive approach is the creation of flame-spread barriers. The active approach refers to the actual method of fire extinguishment. With the phasing out of halon as a fire extinguishing agent because of its environmental impact, other fire extinguishing techniques have been explored. The most promising technique is water droplet delivery to the flaming fuel. Required droplet size is less than 100 microns. The effect of the water droplets is based on expansion to water vapor at the flame origin site thereby diluting available oxygen to the flame below that is required for a sustained flame. The flame is also cooled by the uptake of heat of vaporization of the water droplets.
Dr. Supkis reviewed anesthetic considerations intended to reduce the operating room fire hazard. He discussed the appropriate use of oxygen pointing out the need to consider its concomitant increased fire risk.
The pulse oximeter provides us with a means to assess the need for supplemental oxygen and allows us to withhold supplementation in potentially dangerous situations when it is not really indicated in order to minimize the fire risk. He discussed the appropriate use of the electrosurgical unit, including the increased risk during head and neck procedures during which an oxygen enriched atmosphere is common. He also recommended “holstering” the electrosurgical unit when not in active use to help prevent accidental activation causing ignition. During tracheostomy the use of sharp dissection to enter the trachea is encouraged to avoid ignition of the underlying endotracheal tube in the oxygen and nitrous oxide enriched anesthetic atmosphere. The placement of the laser in “standby” mode when not in active use is mandatory for reasons similar to those for holstering the cautery wand.
For surgery of the upper airway involving a laser, a laser-resistant tube should be utilized, the FiO2 should be kept to 30% or below, and as limited as possible an amount of power should be utilized by the laser. For surgery involving the lower airway, mainly trachea, there are currently no laser resistant tracheal tubes. Therefore, there should be no flammable material below the tip of the laser fibers. FiO2 should be limited to 30% or less without the use of nitrous oxide. If an airway fire is suspected, stop ventilation and immediately disconnect the breathing tube Y-piece from the endotracheal tube adaptor, and in the same motion remove the endotracheal tube and any other airway adjunct from the airway. Then, resume ventilation via bag/mask and re-intubate the patient. Perform rigid and/or flexible bronchoscopy to assess airway damage. Draw blood for carboxy hemoglobin determination to access the amount of smoke the patient has inhaled during the airway fire.
Fires can occur in and around the patient. The use of organic solvents can serve as accelerants to help ignite the draping system. The drapes can be easily ignited by the electrosurgical unit, hot wire cautery and laser devices. It must be remembered that supplemental oxygen supplied to the patient can migrate through the draping system and be trapped between the layers of drapes rendering the draping system layers extremely flammable. Care must be taken in using any source of ignition around the draping system where supplemental oxygen is being employed.
Intestinal gas fire and explosion can occur when ignited by the electrosurgical unit or laser. Sufficient oxygen to support combustion of hydrogen and/or methane is normally not present in intestinal gas. However, the administration of nitrous oxide and its subsequent diffusion into the intestinal lumen can create a flammable premixed fuel/oxygen mixture. The chance of such an explosion/fire is reduced if nitrous oxide is avoided.
The panel discussion was well attended and generated many questions and comments from audience members.
Dr. Wolf is Professor of Anesthesiology, State University of New York Health Science Center in Brooklyn, NY.