The prevention of fire during oropharyngeal electrosurgery. (Original Article).

Abstract

We report the results of our study of 25 children who underwent tonsillectomy and/or adenoidectomy under endotracheal general anesthesia with respect to their risk of fire in the oropharynx. We also attempt to explain the reasons for the difference between the relatively high incidence of airway explosions and fires that have occurred during tracheostomy with electrosurgery and electrocautery and the low incidence of these events during electrosurgical dissection of the tonsils. Finally, we review the precautions that physicians can take to lower the risk of operating-room fires and explosions.

Introduction

Electrosurgery has become increasingly popular over the past decade. However, performing electrocautery in the head and neck region can pose a risk of fire because it involves the presence of combustible materials in an oxygen-rich environment in the upper aerodigestive tract and bronchopulmonary area. Several instances of operating-room fires and explosions that started in breathing tubes during tracheostomy have been reported, (1-7) as have occasional fires in the oropharynx during tonsillectomy. (8-10)

Protocols have been established for the use of electrocautery devices during tracheostomy. However, little attention has been given to the incidence and causes of fires in the oropharynx during tonsil and adenoid procedures performed with general anesthesia and electrocautery dissection. Even though many more electrocautery dissections of the tonsils are performed than are tracheostomies, there are few reports of electrocautery-related fires. In this article, we report the results of our study of fire in the oropharynx.

Patients and methods

We prospectively studied 25 consecutive patients--13 girls and 12 boys, aged 4 to 11 years (mean: 6.2)--who had undergone tonsillectomy and/or adenoidectomy under endotracheal general anesthesia (table). The general anesthetic (sevoflurane, nitrous oxide, and oxygen) was supplemented with intravenous morphine as needed for analgesia. Children younger than 10 years of age were induced by inhalation, and those who were older were induced with 2 to 3 mg/kg of IV propofol. Children younger than 10 years were intubated without the use of a muscle relaxant; the older children received a dose of rocuronium at 0.6 mg/kg. The size of the endotracheal tube in the younger group was based on the patient's age (tube size = [age + 16] % 4); tube size in the older group was selected on the basis of the patient's weight and the results of the anesthesiologist's clinical evaluation.

After induction and tube placement was achieved, anesthesia was maintained with 2 to 3% sevoflurane, nitrous oxide, and oxygen at 2 liters each during the entire surgical procedure. Patients were ventilated with positive pressure, and peak airway pressures were maintained at approximately 20 cm of water. A Crow-Davis mouth gag was inserted to facilitate the surgical procedure.

Nitrous oxide and oxygen concentrations were measured with a Datex-Engstrom AS/3 anesthetic monitor equipped with an AS/3 airway module. Inspiratory concentrations of both nitrous oxide and oxygen were recorded by a gas-sampling line attached to a standard anesthetic circuit. A 14 French Airlife oxygen catheter was then placed in the tonsillar fossa, and nitrous oxide and oxygen concentrations were again sampled. Airway leak pressure was quantified in terms of the amount of airway pressure (cm [H.sub.2]O) at which an uncuffed endotracheal tube leaks gas flow; it was detected by listening through a stethoscope placed over the trachea.

Results

No airway fires occurred during the course of this study despite the use of electrocautery to achieve hemostasis. Airway gas analysis at the tonsillar fossa revealed that when airway leak pressures were lower than 12 cm [H.sub.2]O, the concentrations of nitrous oxide and oxygen were essentially the same as the inspired concentration of the delivered gas flow. When airway leak pressures were higher than 12 cm [H.sub.2]O, the inspired gas concentrations were essentially the same as that of room air (nitrous oxide: 0%; oxygen: 21%). Of note is the fact that at an airway leak pressure of exactly 12 cm [H.sub.2]O, one patient exhibited room-air gas concentrations and one patient exhibited inspiratory gas concentrations measured at the tonsillar fossa.

Discussion

We attempted to explain the reasons for the difference between the relatively high incidence of airway explosions and fires that have occurred during tracheostomy with electrosurgery and electrocautery and the low incidence of these events during electrosurgical dissection of the tonsils. When performing these two types of surgery, the physical milieu is similar; both are performed in an oxygen-rich environment and with the same electrosurgical equipment and combustible materials. It is well known that the origination of a fire requires a combustible material, an ignition source, and an oxidizing agent. All three elements are present during tonsil and adenoid surgery. The combustible materials include the endotracheal tube, tonsillar tissue, necrotic charred tissue, and suture materials; the ignition source is the electrosurgical device; and the oxidizing agent is nitrous oxide and/or oxygen.

Operating-room fires were more common in the past, when ether and cyclopropane anesthetics were frequently used. Today, combustible anesthetic agents are no longer used. Room air is approximately 20% oxygen. The concentration of oxygen at the surgical site can be considerably higher when oxygen is being administered to the patient. A high percentage of inspired oxygen (25 to 50%) is needed to support combustion. The minimum concentration of oxygen necessary to adequately oxygenate a patient varies according to the patient's age, the presence of any coexisting medical conditions, and other medical factors. When a high concentration is necessary, the surgeon should be informed so that an instrument other than an electrosurgical scalpel might be selected.

The prevention of surgical fires begins in the preoperative period. Electrosurgical equipment should be calibrated and inspected frequently and the equipment so labeled. The equipment should be used only by properly trained physicians who are certified to execute the specific procedure being performed. Surgeons must understand the differences between electrosurgical and electrocautery techniques and bipolar and unipolar instrumentation. In the presence of flammable substances, these electrical devices should either not be used or used with extreme caution.

Anesthesiologists must make certain that all oxygen circuit connections are leak-free and that the cuff of the endotracheal tube seals the lower airway from the upper airway. In pediatric cases where an uncuffed endotracheal tube is used, the selection of the tube size should be made with the understanding that too large an airway leak can significantly raise the nitrous oxide and oxygen concentrations at the operative site. Surgeons must make sure that all electrical connections are secure in order to diminish the potential for a spark or arcing of the circuit.

Yet despite all precautions, a spark or arc at the tissue-electrode interface can still occur and increase the possibility of fire if other factors are not controlled. The excessive charring of tissue can result in the emission of organic gases in sufficient quantity to act as a combustible agent. Therefore, char should be kept to a minimum. Other sources of fuel are fatty tissue, dry muscle, dry connective tissue, dry gauze and pharyngeal packing, suture material, adhesive tape used to secure the endotracheal tube, tincture of benzoin, and aerosolized topical anesthetic sprays.

In view of all the potential risk factors, it is a wonder that so few fires have been reported in the oropharynx. After surgeons and anesthesiologists have practiced for years without incident, we often neglect to adhere to the basic safety precautions and thought processes that were instilled in us during training and our early years of experience. When competent senior surgeons on our staff reviewed the occurrence of tracheal fires during tracheostomy, many did not regard the backflow of oxygen at the point of tracheostomy to be a critical factor. Yet when given the opportunity to think about it, all agreed that the potential for significant complications certainly does exist.

Several reasons explain the low incidence of oropharyngeal fires during electrosurgical techniques. During gentle fine-needle electrosurgical dissection, very little combustible material is available in the way of char, fat, and dry or necrotic tissue. The endotracheal tube is in the surgeon's direct vision and away from the electrosurgical dissection field. The oxidizing agents are of low concentration, and no other combustible anesthetic agents are in use. Although the endotracheal tube is at times very close to the electrode, the tube is almost never violated. Because the "oxygen index of flammability" (the percentage of oxygen concentration required to support combustion) of the polyvinyl chloride in tracheal tubes is relatively high (26.3%), these tubes are not likely to ignite in a low-oxygen environment. (2) A polyvinyl chloride tube will not support combustion if the oxygen concentration is less than 25%.

We conclude that electrosurgical procedures of the oropharynx and hypopharynx appear to be safe when performed in a controlled anesthetic environment in a properly intubated patient. To minimize the risk of airway fire in children, we recommend that an appropriately sized uncuffed endotracheal tube be placed so that the airway leak pressure remains higher than 12cm [H.sub.2]O. In our study, we found that such a placement kept the nitrous oxide and oxygen concentrations at the surgical site to a minimum.

Table

Patient characteristics and findings

         Tube     Cuff leak      % Insp      % Insp      % Exp
Age/sex  size  (cm [H.sub.2]O)  [O.sub.2]  [N.sub.2]O  [O.sub.2]

  8/F    5.5         15            51          44         21
 11/F    5.5         12            61          37         21
  3/F     5          18            49          48         21
  5/M     5           8            51          46         48
  6/F    5.5          8            49          48         45

  9/F     6           8            52          47         38
  3/F    4.5         22            52          43         21
  5/M     5           8            47          50         47
  9/M    5.5         16            50          47         26
 10/F    5.5        None           49          47         21

  7/M    5.5        None           51          46         21
  4/M     5          12            41          58         21
  5/M     5          18            33          51         21
  4/M    4.5          6            48          49         43
  5/F     5           8            49          47         22

  6/F    5.5         10            50          48         41
  5/F     5           8            49          47         48
 10/M    6.5          4            51          45         49
  6/F     5           8            48          49         47
  7/M    5.5         12            31          62         31

  4/F     5           4            38          62         38
  5/F    5.5        None           56          44         21
  5/M     5           8            38          62         41
  5/M     5           7            42          58         48
  7/M     6           8            52          48         57

           % Exp
Age/sex  [N.sub.2]O

  8/F        0
 11/F        0
  3/F        0
  5/M        44
  6/F        48

  9/F        31
  3/F        0
  5/M        45
  9/M        10
 10/F        0

  7/M        0
  4/M        0
  5/M        0
  4/M        46
  5/F        3

  6/F        54
  5/F        49
 10/M        40
  6/F        47
  7/M        62

  4/F        62
  5/F        1
  5/M        59
  5/M        52
  7/M        43

References

(1.) Awan MS, Ahmed I. Endotracheal tube fire during tracheostomy: A case report. Ear Nose Throat J 2002;81:90-2.

(2.) Lim HJ, Miller GM, Rainbird A. Airway fire during elective tracheostomy. Anaesth Intensive Care 1997;25:150-2.

(3.) Bailey MK, Bromley HR, Allison JG, et al. Electrocautery-induced airway fire during tracheostomy. Anesth Analg 1990;71:702-4.

(4.) Mandych A, Mickelson S, Amis R. Operating room fire [letter]. Arch Otolaryngol Head Neck Surg 1990;116:1452.

(5.) Thompson JW, Colin W, Snowden T, et al. Fire in the operating room during tracheostomy. South Med J 1998;91:243-7.

(6.) Marsh B, Riley RH. Double-lumen tube fire during tracheostomy. Anesthesiology 1992;76:480-1.

(7.) Baur DA, Butler RC. Electrocautery-ignited endotracheal tube fire: Case report. Br J Oral Maxillofac Surg 1999;37:142-3.

(8.) Brechtelsbauer PB, Carroll WR, Baker S. Intraoperative fire with electrocautery. Otolaryngol Head Neck Surg 1996;114:328-31.

(9.) Simpson JI, Wolf GL. Endotracheal tube fire ignited by pharyngeal electrocautery. Anesthesiology 1986;65:76-7.

(10.) Wolf GL, Sidebotham GW. Endotracheal tube fire: Comments on the advisability of not extubating [letter]. Anesthesiology 1999;91:888-9.

From the Division of Otolaryngology-Head and Neck Surgery. (Dr. Mattucci) and the Department of Anesthesiology (Dr. Militana), North Shore University Hospital, Manhasset, N.Y.

Reprint requests: Kenneth F. Mattucci, MD, 333 E. Shore Rd., Manhasset, NY 11030. Phone: [phone]; fax: [phone]; e-mail: [e-mail]