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The risk of an endotracheal tube's combustion during laser airway surgery necessitates the use of special anesthetic techniques and equipment to prevent this complication. This study was designed to evaluate the Laser-Trach(TM), a new laser-resistant rubber endotracheal tube for use during laser airway surgery. The Laser-Trach endotracheal tubes that were evaluated were size 6.0 mm internal diameter (ID) red rubber endotracheal tubes which had been commercially wrapped by Kendall-Sheridan (Mansfield, Mass.) with copper foil tape and overwrapped with fabric. The fabric layer was saturated with water prior to our tests, as recommended by the manufacturer. The Laser-Trach endotracheal tubes were compared with plain (bare) size 6.0 mm ID Rusch red rubber endotracheal tubes. The tubes under study were positioned horizontally on wet towels in air and had 5 L x min(-1) of oxygen flowing through them. They were subjected to continuous laser radiation at 40 W from either a CO2 or an Nd-YAG laser. The Nd-YAG laser was propagated via a 600-micron fiber bundle. Each laser was directed perpendicularly at the shaft of the endotracheal tube being studied, and its output was continued until a blowtorch fire occurred or 60 seconds had elapsed. Sixty seconds of CO2 laser fire did not ignite any of the eight Laser-Trach endotracheal tubes tested. However, blowtorch ignition of all eight bare rubber tubes tested occurred after 0.87 +/- 0.21 (mean +/- SD) seconds of CO2 laser fire. Nd-YAG laser contact with the Laser-Trach endotracheal tubes caused the perforation and blowtorch ignition of all eight tubes tested after 18.79 +/- 7.83 seconds. This was a significantly (P<.05) longer time than the 5.45 +/- 4.75 seconds required for the blowtorch ignition of all eight plain rubber endotracheal tubes tested with the Nd-YAG laser. Our results show that under the conditions of this study, the shafts of the Kendall-Sheridan Laser-Trach endotracheal tubes were resistant to the C02 laser. However, this endotracheal tube is not recommended for use with the Nd-YAG laser.

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The occurrence of airway fires during laser airway surgery necessitates the use of special techniques to improve patient safety. For example, it is recommended that the endotracheal tube cuff be inflated with saline. However, in the event of an endotracheal tube fire, the tube must be quickly removed. This study was designed to determine the time necessary for red rubber (RR) or polyvinylchloride (PVC) endotracheal tubes to be removed from a model airway after inflating the cuffs with saline. A model larynx and trachea was suspended vertically. It was intubated with either 7.0 RR or PVC endotracheal tubes. Six milliliters of saline was used to inflate the endotracheal tube cuffs. After inflation, a clamp was used to occlude the pilot tube on the RR endotracheal tubes. A 4-lb weight was then suspended from the endotracheal tube. The time to spontaneous extubation of the model trachea after unclamping the pilot tubes on 12 RR endotracheal tubes was determined. For the PVC endotracheal tubes, the times to spontaneous extubation using the 4-lb weight were determined in 12 endotracheal tubes after cutting the pilot tube and in 12 by maximum aspiration of the saline from the endotracheal tube cuff with a 10-ml syringe. A time of 0.94 +/- 0.10 sec (mean +/- SD) was required for spontaneous extubation of the RR endotracheal tubes after unclamping the pilot tube. For the PVC endotracheal tubes, extubation occurred 3.28 +/- 1.08 and 1.81 +/- 0.60 sec after cutting the pilot tube or deflating the cuff with a syringe, respectively. The mean times for each of the 3 groups were significantly different (p < 0.05) from each other as determined by the ANOVA. This study shows that if PVC endotracheal tubes are used, deflation of the saline-filled cuff by aspiration with a 10-ml syringe is faster than cutting the pilot tube. Unclamping the pilot tube on the RR endotracheal tubes resulted in the fastest time to endotracheal extubation.

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STUDY OBJECTIVE: To predict the inspired concentrations achieved when nitrous oxide (N2O)/oxygen mixtures are administered to patients by way of a nasal cannula. DESIGN: The method used for estimating the FiN2O is based on one employed to calculate the FiO2 obtained with a nasal cannula. We assume a tidal volume of 500 ml, a respiratory rate of 20 breaths per minute, an inspiratory time of 1 second, an expiratory time of 2 seconds, and an anatomic reservoir volume of 50 ml. The reservoir consists of the nose, the nasopharynx, and the oropharynx. Its volume is assumed to be one-third of the anatomic dead space. It is also assumed that during the last 0.5 second of expiration, there is negligible flow of expired respiratory gases. A 6 L/min flow from the cannula will completely fill the reservoir. The FiO2 or FiN2O is then calculated by assuming that during the 1 second inspiratory time period, the gases in the anatomic reservoir that are provided by the nasal cannula and a volume of air such that the sum of the components of the tidal volume equals 500 ml are inspired. SETTING: Research laboratory of a university-affiliated metropolitan medical center. MEASUREMENTS AND MAIN RESULTS: The calculated FiO2 values for 100% oxygen delivered by nasal cannula agree with those determined by others. The FiN2Os estimated were directly proportional to the cannula flow rate and the fraction of N2O delivered. At the maximum total flow rate considered, 6L/min flow, with 70% N2O (remainder O2) delivered to the nasal cannula, an FiN2O of only 0.21 was estimated due to the large volume of air inspired. The FiO2 under these conditions would only be 0.23. CONCLUSIONS: Our analysis shows that the maximum FiN2O achievable by using a nasal cannula is limited to 0.21 even with a 6 L/min flow of 70% N2O for the defined respiratory parameters.

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STUDY OBJECTIVE: To determine unbiased patient preferences for either spinal or general anesthesia for upcoming surgeries. DESIGN: Prior to contact with anesthesia personnel, a simple questionnaire was completed by surgical patients to determine their demographic characteristics and previous anesthetic experiences. Their concerns regarding a list of complications of general and spinal anesthesia and their preferences for general or spinal anesthesia if either method could be used were also determined. SETTING: University-affiliated suburban community hospital. MEASUREMENTS AND MAIN RESULTS: The survey was completed by 254 patients. A preference for general over spinal anesthesia was expressed by 80.2% of the patients responding. They expressed significantly more concerns regarding nausea/vomiting, sore throat, feeling sleepy, and death with general anesthesia than with spinal anesthesia. Concerns of back pain, nerve damage and paralysis were statistically related to spinal anesthesia. CONCLUSIONS: This survey shows a strong patient preference for general anesthesia and a phobia for spinal anesthesia.

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STUDY OBJECTIVE: To determine whether saline soaked pledgets would protect the cuffs of polyvinylchloride (PVC) endotracheal tubes from carbon dioxide (CO2) laser-induced combustion. DESIGN: 12 PVC endotracheal tubes were studied. The cuffed end of each was placed in a graduated cylinder and flushed with 5 L/min of oxygen for 5 minutes. The endotracheal tube's cuff was then inflated with air and the system pressure set to 20 cm H2O. SETTING: Research laboratory of a university hospital. INTERVENTIONS: Six of the endotracheal tube cuffs were protected with 1 inch by 3 inch saline soaked pledgets and six were left unprotected. A CO2 laser set to 40 watts was then fired at the cuffs. MEASUREMENTS AND MAIN RESULTS: All six unprotected cuffs were ignited in less than 1 second. No significant combustion occurred at the six pledget protected endotracheal tube cuffs after 1 minute of laser fire. CONCLUSIONS: Under the conditions of this experiment, saline soaked pledgets protected PVC endotracheal tube cuffs from the CO2 laser.

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We determined whether propofol, thiopental, or 0.9% saline would serve as a growth medium for Candida albicans. In Part I, we investigated whether opening 20 propofol ampules would cause glass particles from the exterior of the ampule to fall into the emulsion and contaminate it. Each ampule was painted with red fingernail polish and its contents were passed through filter paper after it was opened in a routine manner. In Part II, a sample from a colony of C albicans was added to sterile vials containing 20 mL of either 0.9% saline, 1% propofol, or 2.5% thiopental. A 1-microL sample from each vial was then plated onto Sabaroud's dextrose plus brain-heart infusion (SABHI) agar at the following times after inoculation: 0, 3, 6, 16, and 24 h. The plates were incubated at 35 degrees C for 24 h and the number of colony-forming units counted. The filtration of two of the painted ampules in Part I revealed red glass fragments. In Part II, the saline and thiopental solutions did not increase the number of colonies of C. albicans by 24 h. However, the propofol, after a latent period between 6 and 16 h, supported the growth of C. albicans at a rapid rate. Our investigation shows that glass particles from the exterior of a propofol ampule can contaminate its contents when the ampule is opened in a routine manner. Furthermore, propofol provides an excellent growth medium for C. albicans. Thiopental and saline showed no growth. We conclude that the ability of propofol to grow C. albicans necessitates rigorous standards of sterility in its handling.

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STUDY OBJECTIVE: To determine whether the window design of pencil-point spinal needles leads to deformation under lateral or axial loading conditions. DESIGN: Independent-measure, multigroup study of the force required to deform needles. SETTING: Independent testing laboratory. MEASUREMENTS AND MAIN RESULTS: The force necessary to bend 22- and 24-gauge Sprotte, 22- and 25-gauge Whitacre, and 22- and 25-gauge Quincke needles was measured using an Instron gauge (Instron Corp., Canton, MA) after microscopic verification of needle uniformity. Effects of lateral and axial forces were evaluated in separate experiments. The force needed to bend the Sprotte needles was less than that needed for the Whitacre and Quincke needles of similar size when lateral or axial pressure was applied. Microscopic inspection of the needles showed a marked variability in the window area placement in a single lot of Sprotte needles. Examination of the needle tips demonstrated that the Sprotte needles were most likely to bend at the needle window, while the Quincke and Whitacre needles deformed at the point of clamping. CONCLUSIONS: The Sprotte needles have an inherent design weakness to lateral and axial pressure, which may result in a greater number of needle tip deformations upon needle insertion. The nature of this deformation may result in difficulty in needle withdrawal and possibly fracture of the needle tip.

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The protection afforded against CO2 laser-induced combustion by five different types of tracheal tubes or protective foil wraps was evaluated. They were compared before and after the application of human blood to their external surfaces. The tracheal tubes tested were polyvinylchloride (PVC) tubes wrapped with Venture copper (Cu) foil tape, 3M aluminum (Al) foil tape, and the Laser-Guard protective coating. The Xomed Laser Shield II and Mallinckrodt Laser-Flex tracheal tubes were also tested. A CO2 laser set to 38 W in the continuous mode was directed at the shaft of the tracheal tube under study, which had 5 L/min of oxygen flowing through it. The laser was actuated for 90 seconds or until combustion or melting occurred. The copper foil-wrapped and aluminum foil-wrapped PVC tracheal tubes were unaffected by 90 seconds of laser fire in five trials with each type of tape. However, the application of blood to the foil wrapped PVC tracheal tube shafts resulted in combustion in 3 of 5 copper foil-wrapped tubes and melting of the underlying tracheal tube shaft in 3 of 5 aluminum foil-wrapped PVC tracheal tubes. Blood did not affect the protection afforded by the Laser-Guard coating when it was applied to the shafts of PVC tracheal tubes. Similarly, the Xomed Laser Shield II tracheal tube's shaft offered good protection from the laser both before and after application of blood. Combustion occurred in 1 of 4 Mallinckrodt Laser Flex tracheal tubes studied prior to the application of blood. The application of blood resulted in almost immediate combustion in all 4 Mallinckrodt Laser Flex tracheal tubes tested. The presence of blood on the surface of metallic foil-wrapped or special tracheal tubes may make laser-induced combustion more likely during airway surgery. However, the Laser-Guard protective coating and the Xomed Laser-Shield II tracheal tube provide good protection even when covered with blood.

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STUDY OBJECTIVE: To determine whether metallic Y-pieces and elbows would halt the progression of a laser-induced endotracheal tube fire. DESIGN: A segment of polyvinyl chloride endotracheal tube was attached to either an all-plastic anesthesia circle breathing system (n = 5) or a circuit consisting of a metal Y-piece and elbow with plastic hoses (n = 5). In each case, an Nd-YAG laser was used to ignite the endotracheal tube segment and attached anesthesia circuit as 5 L/min of oxygen was flowing through them. SETTING: Research laboratory of a university-affiliated metropolitan medical center. MEASUREMENTS AND MAIN RESULTS: The flames from the endotracheal tubes burned through the 22 mm hoses that were part of the all-plastic circuits in 49.5 +/- 8.8 seconds (mean +/- SD). In none of the trials with the metal components did the fire advance beyond the endotracheal tube's 15 mm adapter. CONCLUSIONS: Metal circuit components halt the progression of laser-induced endotracheal tube fires toward the anesthesia machine.

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STUDY OBJECTIVE: To determine whether nitrogen insufflation reduces the laser-induced combustibility of polyvinyl chloride (PVC) endotracheal tube cuffs. SETTING: Research laboratory of a metropolitan, university-affiliated medical center. DESIGN AND INTERVENTIONS: A plastic catheter was fastened along the shafts of 10 PVC endotracheal tubes with self-adhesive copper foil tape down to a level just above the cuff. The modified endotracheal tubes were inserted into graduated cylinders and flushed with oxygen. The cuffs were then inflated with air, and a carbon dioxide (CO2) laser was aimed at them. Five of the modified endotracheal tubes had 10 L/min of nitrogen insufflated via the plastic tube. MEASUREMENTS AND MAIN RESULTS: The laser ignited only 1 of the cuffs insufflated with nitrogen; however, all 5 of the modified endotracheal tubes that were not insufflated burned (p < 0.05). CONCLUSION: Nitrogen insufflation decreases CO2 laser-induced PVC endotracheal tube cuff combustibility. However, clinical applications of this technique should be undertaken with caution, as the administration of a hypoxic mixture may be possible.

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Patient infections related to the use of propofol have been reported. To investigate the growth of Staphylococcus aureus in propofol, thiopental, methohexital, etomidate, and 0.9% saline containing no bacteriostatic drug, these preparations were inoculated and samples were plated onto blood agar at 0, 3, 6, 21, 24, and 27 h. The number of colony-forming units (CFU) on the plates was then determined after 24 h of incubation. Samples from the inoculated etomidate solution showed zero CFU at 3 h and thereafter, whereas 21 h were required by the methohexital and thiopental solutions to reduce the number of CFU to zero. For normal saline, no significant change in CFU was seen before the first 6 h, then the number of CFU gradually declined, although some S. aureus CFU were still present at 27 h. Inoculation of the propofol emulsion resulted in a substantial growth of S. aureus between 6 and 21 h after inoculation. We conclude that, of the preparations tested, only propofol was an excellent medium for the rapid growth of S. aureus. Meticulous sterile technique, therefore, is advised when handling it.

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To determine whether Dermacare's laser eye shield, anesthesia circuit protector, and barrier drape were laser resistant, the three products were tested with CO 2 and Nd:YAG lasers set to 70 to 60 W, respectively. Five separate areas on each product were unaffected by 1 min of continuous laser fire with each type of laser. It is concluded that the Dermacare draping products offer good laser safety under the conditions of this experiment.

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The potassium-titanyl-phosphate laser is being used for airway surgery and could cause an endotracheal tube fire. To determine whether five different metallic foil tapes or the Laser-Guard protective wrap would protect polyvinylchloride (PVC) endotracheal tubes from this laser, it was set to a power of 18 W and aimed at the wrapped endotracheal tube under study for up to 1 min while 5 L/min of oxygen flowed through the endotracheal tube. A plain (unwrapped) PVC endotracheal tube was studied also. The plain PVC endotracheal tube was ignited by the laser after 14 s. Potassium-titanyl-phosphate laser radiation did not significantly affect the nonadhesive sides of the foil tapes tested or the Laser-Guard covering. However, potassium-titanyl-phosphate laser radiation caused ignition or melting of underlying PVC endotracheal tubes when it was applied to the endotracheal tubes with the adhesive side of the foil tapes facing outward. It is concluded that only the Laser-Guard protective coating adequately protected the PVC endotracheal tubes tested under the conditions of this experiment.

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