Abstract
Objective
We performed retrospective clinical analysis and in vitro testing to analyze the risks involved in laryngeal surgery using a CO 2 laser.
Materials and methods
The occurrence of adverse events during laryngeal surgeries using a CO 2 laser, the reasons for these adverse events, and the risks of laryngeal laser surgery were analyzed in 704 patients. In vitro experiments were performed to observe the tolerance of the cuffs of polyvinylchloride (PVC) endotracheal tubes to the CO 2 laser under conditions of filling water or air, different laser power levels, and different cutting patterns. The flammability of the PVC endotracheal tube under different oxygen concentrations, laser power levels, and laser cutting patterns were also studied.
Results
In the 704 patients who underwent laryngeal laser surgery, the tracheal cuff broke in 92 cases; sparks were observed in 8 cases; and dense smoke, in 27 cases during surgery. No fires or explosions occurred. The in vitro results were as follows: (1) Under the intermittent stimulation mode, the water cuff did not break, but the air cuff broke during the first stimulation. (2) Under the continuous stimulation mode, the water and air cuffs broke easily, and the water and air cuffs broke immediately when the stimulation power was greater than 8 W. (3) Under the intermittent stimulation mode, the PVC endotracheal tube burned only under conditions of pure oxygen supply and 10 W of laser power. Under the continuous stimulation mode, the tube did not burn with 5 W of laser power, regardless of the oxygen concentration used. When the laser power level reached 8 W and the oxygen concentration was greater than 50%, the tube will easily burn. When the laser power level was 10 W, the tube burned at oxygen concentrations greater than 20%.
Conclusions
Burning of the tube during laryngeal surgery using a CO 2 laser could be effectively avoided when appropriate measures were taken, such as filling the endotracheal cuff with water, maintaining less than 40% oxygen concentration, using less than 8 W laser power, and using the intermittent stimulation mode.
1
Introduction
Since the introduction of CO 2 lasers in laryngeal surgery by Strong and Jako in 1972 , laser surgery has been widely used for treating airway diseases. However, airway burning or endotracheal tube explosions often occurred during these procedures , which has caused concern among otolaryngologists and anesthetists. In developing countries, endotracheal tubes made from polyvinylchloride (PVC) are the most commonly used intraoperative endotracheal tubes; these tubes are easily flammable as their melting point is between 100°C and 260°C. Therefore, it is necessary to explore the safety issues associated with the use of PVC tubes.
The study was divided into 2 parts: (1) assessment of the occurrence of adverse events during a laryngeal CO 2 laser surgery, the reasons for these adverse events, and the risks of laryngeal laser surgery in 704 patients and (2) in vitro experiments to observe the flammability of ordinary PVC tubes and tube cuffs and a discussion of the safety issues associated with PVC tube flammability.
2
Materials and methods
2.1
Clinical observation
We retrospectively analyzed the complications in 704 American Society of Anesthesiology I-II patients who underwent laryngeal surgery using a CO 2 laser between July 2003 and August 2008 in our hospital. All surgeries were performed under general anesthesia; and tracheal intubation, including 564 surgeries, performed under combined intravenous and inhalation anesthesia; and 140 surgeries, performed under total intravenous anesthesia. Rapid intravenous induction of anesthesia and tracheal intubation were performed. The induction drugs included fentanyl (2–4 μ g/kg), propofol (1.5–2.5 mg/kg), and succinylcholine chloride (2 mg/kg), and the auxiliary drugs used included penehyclidine (10 μ g/kg) and methylprednisolone (20–28 mg). Polyvinylchloride tracheal tubes (Mallinckrodt Company, Damastown Mulhaddart Dublin, The Republic Of Ireland) with an internal diameter of 4.5 to 7.0 mm were used. All surgeries were performed under a suspension laryngoscope. Cotton slices or gauze pads soaked with salt water were inserted between the cuff of the endotracheal tube and the vocal cords during the surgery. A 2- to 10-W laser device (NO.AA2345100; Lumenis, Medan, Indonesia) was used during the surgery. The intraoperative risks and complications, including broken tracheal cuffs, dense smoke, burnt smell, sparks, burning, and explosions, were analyzed.
2.2
In vitro experiments
The PVC endotracheal tube cuffs were filled with saline or air in vitro. The filled volume was 5 to 8 mL, until the cuff was completely full, and the cuff pressure was 20 to 30 cm H 2 O. Polyvinylchloride endotracheal tube cuffs were stimulated in air by a CO 2 laser beam with an emission power of 5, 8, or 10 W under continuous or intermittent mode. The tolerance and flammability of the cuffs were observed under different laser power levels and cutting patterns. Then, the walls of the PVC endotracheal tubes were stimulated under continuous or intermittent continuous mode by a CO 2 laser beam with an emission power of 5, 8, or 10 W and oxygen concentrations of 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. The flammability of the PVC endotracheal tubes was observed under different laser power levels, cutting patterns, and oxygen concentrations. Ten PVC endotracheal tubes (Mallinckrodt Corporation) were used in each group. Laser stimulation was stopped when the air cuff broke or when the tube was burned. If the tube did not break or burn, then the stimulation time was set as 60 seconds. All the parameters were presented as mean ± SD.
2
Materials and methods
2.1
Clinical observation
We retrospectively analyzed the complications in 704 American Society of Anesthesiology I-II patients who underwent laryngeal surgery using a CO 2 laser between July 2003 and August 2008 in our hospital. All surgeries were performed under general anesthesia; and tracheal intubation, including 564 surgeries, performed under combined intravenous and inhalation anesthesia; and 140 surgeries, performed under total intravenous anesthesia. Rapid intravenous induction of anesthesia and tracheal intubation were performed. The induction drugs included fentanyl (2–4 μ g/kg), propofol (1.5–2.5 mg/kg), and succinylcholine chloride (2 mg/kg), and the auxiliary drugs used included penehyclidine (10 μ g/kg) and methylprednisolone (20–28 mg). Polyvinylchloride tracheal tubes (Mallinckrodt Company, Damastown Mulhaddart Dublin, The Republic Of Ireland) with an internal diameter of 4.5 to 7.0 mm were used. All surgeries were performed under a suspension laryngoscope. Cotton slices or gauze pads soaked with salt water were inserted between the cuff of the endotracheal tube and the vocal cords during the surgery. A 2- to 10-W laser device (NO.AA2345100; Lumenis, Medan, Indonesia) was used during the surgery. The intraoperative risks and complications, including broken tracheal cuffs, dense smoke, burnt smell, sparks, burning, and explosions, were analyzed.
2.2
In vitro experiments
The PVC endotracheal tube cuffs were filled with saline or air in vitro. The filled volume was 5 to 8 mL, until the cuff was completely full, and the cuff pressure was 20 to 30 cm H 2 O. Polyvinylchloride endotracheal tube cuffs were stimulated in air by a CO 2 laser beam with an emission power of 5, 8, or 10 W under continuous or intermittent mode. The tolerance and flammability of the cuffs were observed under different laser power levels and cutting patterns. Then, the walls of the PVC endotracheal tubes were stimulated under continuous or intermittent continuous mode by a CO 2 laser beam with an emission power of 5, 8, or 10 W and oxygen concentrations of 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. The flammability of the PVC endotracheal tubes was observed under different laser power levels, cutting patterns, and oxygen concentrations. Ten PVC endotracheal tubes (Mallinckrodt Corporation) were used in each group. Laser stimulation was stopped when the air cuff broke or when the tube was burned. If the tube did not break or burn, then the stimulation time was set as 60 seconds. All the parameters were presented as mean ± SD.
3
Results
3.1
Clinical observation
Between July 2003 and August 2008, 704 patients underwent CO 2 laser surgery. The oldest patient was 87 years old, and the youngest was 2 years old (mean age, 48.6 years). There were 469 male patients (mean age, 50.9 years) and 235 female patients (mean age, 41.6 years). Intraoperative laser power levels were 2 to 10 W. Intraoperative stimulation modes included continuous and intermittent stimulation modes. The disease types are shown in Table 1 .
| Disease type | Cases |
|---|---|
| Vocal cord leukoplakia | 167 cases |
| Laryngeal cancer | 70 cases |
| Vocal cord dysplasia | 22 cases |
| Vocal cord neoplasm | 141 cases |
| Laryngeal papilloma | 98 cases |
| Arytenoid cyst | 11 cases |
| Vocal cord polyp | 71 cases |
| Vocal cord adhesion and stenosis | 49 cases |
| Vocal cord paralysis | 27 cases |
| Vocal cord granuloma | 24 cases |
| Epiglottic cyst | 13 cases |
| Others | 11 cases |
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