- Email: [email protected]
Faulty spring causing a gas leak
382
Correspondence
[3] Xue FS, Zhang GH, Liu J, et al. A clinical assessment of the Glidescope® videolaryngoscope in nasotracheal intubation with general anesthesia. J Clin Anesth 2006;18:611-5. [4] Xue FS, Zhang GH, Liu J, et al. The clinical assessment of Glidescope® in orotracheal intubation under general anesthesia. Minerva Anestesiol 2007;73:451-7. [5] Cooper RM, Pacey JA, Bishop MJ, McClusky SA. Early experience with a new videolaryngoscope (GlideScope®) in 728 patients. Can J Anaesth 2005;52:191-8. [6] Heitz JW, Mastrando D. The use of a gum elastic bougie in combination with a videolaryngoscope. J Clin Anesth 2005;17:408-9 [Letter]. [7] Neustein SM. Advancing the endotracheal tube smoothly when using the GlideScope®. Can J Anaesth 2008;55:314 [Letter].
Reply Thank you for the opportunity to respond to the letter by Xue et al. The technique of using the endotracheal tube (ETT) as a conduit for the bougie is a rescue technique, to be used when the other manipulations mentioned in our letter have failed [1]. It is not our intention that this technique be used if intubation proves easy. As such, this technique is likely to be quicker and less complex than the commonly used alternatives when passage of the ETT through the glottis proves difficult, such as reshaping the stylet or using a different tube. We agree that this technique is not really suitable for small pediatric patients, but then neither are the McGrath and the GlideScope Cobalt videolaryngoscopes. Our recommendation requires that a suitably sized bougie be available. To facilitate the removal of the stylet from the ETT, especially past the proximal curvature of a RAE tube, we recommend the use of a suitable lubricant on the stylet, such as mineral oil or aqueous gel. The bougie is not inserted blindly but under direct vision using the videolaryngoscope. Of course, the bougie tip disappears from vision once it has passed beyond the glottis, but that is always the case when using a bougie. We hope that Xue and colleagues will try the suggested technique again, after lubricating the stylet, and we hope they will agree that it is a simple, quick and useful rescue technique.
Reference [1] Budde AO, Pott LM. Endotracheal tube as a guide for an Eschmann gum elastic bougie to aid tracheal intubation using the McGrath or GlideScope videolaryngoscopes. [Letter]J Clin Anesth 2008;20:560.
Faulty spring causing a gas leak To the Editor: Over the years there have been a number of case reports of gas leaks occurring from the back bar of the anesthetic machine [1-4]. Most of these reports have described vaporizer or seating faults. A case in which a faulty locking spring on the vaporizer seating was the cause of the problem is presented. A 25 year-old, ASA physical status I man presented for removal of orthopedic metalwork. The anesthetic machine (Datex Ohmeda Aestiva/5; Datex-Ohmeda; GE Healthcare, Chalfont St. Giles, Bucks, UK) was checked appropriately prior to commencement of the case, which was the first of the day. The TEC 5 Isoflurane vaporizer attached to the machine was found not to be properly locking onto the mounting on the back bar. The vaporizer was exchanged for another of the same type, which locked onto the back bar without any problems. The case was begun. After induction, fresh gas flows were set to deliver 6 L/min and the isoflurane vaporizer dial was set to deliver 2%. Inspired concentration of isoflurane was noted to be only 0.9% so the isoflurane vaporizer dial was increased to deliver 3%. Inspired isoflurane concentration at this stage increased to 1.8%. The fresh gas flows were reduced to 1.5 L/min, in line with maintaining low-flow anesthesia, and the percentage dialed on the isoflurane vaporizer remained unchanged. Inspired isoflurane concentration at this stage decreased to 0.7%. The decision was made to change the volatile agent being used to sevoflurane. Dialed and delivered sevoflurane remained consistent, even at low-flow. The patient remained stable and anesthetized throughout the procedure.
Leonard M. Pott MBBCh, FCA(SA) (Associate Professor) Department of Anesthesiology Pennsylvania State University Hershey, PA 17033, USA E-mail address: [email protected] Arne O. Budde MD, DEAA (Assistant Professor) Department of Anesthesiology Pennsylvania State University Hershey, PA 17033, USA doi:10.1016/j.jclinane.2009.02.002
Fig. 1 right.
View of faulty stretched spring on left, new spring on
Correspondence
383
References [1] Wilkinson D, Curtis C. A strange leak from the anaesthetic machine. Anaesthesia 2002;57:1038-9. [2] Ong BC, bin Katjo J, Tan BL, Lee CC, Chan YW. Acute failure of oxygen delivery. Anesthesiology 2001;95:1038-9. [3] Garstang JS. Gas leak from TEC 5 isoflurane vaporiser [Letter]. Anaesthesia 2000;55:915. [4] Lum ME. Fault in a Selectatec manifold resulting in awareness. Anaesth Intensive Care 1994;20:501-3.
Fig. 2
Location of spring, circled on back bar.
The machine was examined by members of the medical physics department. A spring into which the vaporizer locks on the back bar was found to be stretched out of shape and preventing secure locking of the vaporizer (Fig. 1). This spring is located in a small cavity between the two prongs onto which the vaporizer slots (Fig. 2). The medical physics department theorized that the first vaporizer on the machine was not locking, as it was not seated properly, and the spring was stretched by forcing the locking mechanism closed. The second vaporizer appeared to lock appropriately as the spring was not very distorted and the vaporizer was seated correctly. There was, however, enough damage to the spring to cause a leak of fresh gas flow at the point where it enters the vaporizer. This leak would have been of constant volume. It would, therefore, have constituted a small percentage of the fresh gas flow at high flows, which did not manifest as an appreciable leak during the case or during testing of the machine. When the flows were reduced, the leak made up a greater proportion of the total fresh gas flow and so had a greater effect on the amount of gas entering the vaporizer. No other users had reported problems and the machine had been recently serviced. Louise Terry MB BCh, BAO (Specialist Trainee) Department of Anesthesiology University Hospitals Birmingham Selly Oak, England B29 6JD E-mail address: [email protected] Egidio Joseph da Silva MB ChB, DA, FRCA, PGCME (Consultant) Department of Anesthesiology Royal Orthopaedic Hospital Birmingham, England B31 2AP doi:10.1016/j.jclinane.2008.11.003
Lateral femoral cutaneous neuropathy following lateral positioning on a bean bag To the Editor: Iatrogenic neuropathy of the lateral femoral cutaneous nerve (meralgia paresthetica) has been described after orthopedic procedures and following prone or lithotomy positioning. A patient who developed meralgia paresthetica after thoracoscopic surgery in the lateral position is presented. A 14-year-old, 81 kg boy was scheduled for thoracoscopic resection of a right-sided anterior mediastinal mass. After intravenous (IV) sedation, a thoracic epidural catheter was inserted uneventfully at the 7th thoracic interspace with the patient in the sitting position. Following IV induction with the patient placed supine, a left-sided double-lumen tube was inserted. The patient was then turned to the left lateral decubitus position on a bean bag of the older design without a gel surface. A gel axillary roll was placed. The bean bag extended from the patient's shoulder to his thigh. It was molded along the patient's front and back and evacuated. Arms and legs were padded in standard fashion. Thoracoscopic resection was performed uneventfully in a three-hour procedure. Intraoperative table movements were tolerated without apparent shift in the patient's position. His trachea was extubated at the end of the procedure while he was in the supine position, and he was comfortable when transferred to the recovery room. He had good surgical pain control with an epidural infusion of bupivacaine 0.1% with fentanyl 2 µg/mL and clonidine 0.4 µg/mL at 10 ml/hr, but he required ketorolac for management of bilateral shoulder pain. He ambulated with assistance. On postoperative day (POD) 3, the chest tube and the epidural catheter were removed and the patient was discharged home. He presented again on POD 6 to the surgeon with a two-day history (since discharge) of left leg pain affecting the outside of the left thigh, described as shooting and burning, with an area of numbness on the lateral aspect of the thigh. He was limping due to the pain but had no motor deficit. The epidural insertion site was benign and there was no back pain. Pain Management Service was involved on POD 8 and a diagnosis of lateral femoral cutaneous neuropathy was made. The patient was started on gabapentin 100 mg three times a day. The dose was incrementally increased to 400 mg three times a day. Transcutaneous nerve stimulation as well
Correspondence
[3] Xue FS, Zhang GH, Liu J, et al. A clinical assessment of the Glidescope® videolaryngoscope in nasotracheal intubation with general anesthesia. J Clin Anesth 2006;18:611-5. [4] Xue FS, Zhang GH, Liu J, et al. The clinical assessment of Glidescope® in orotracheal intubation under general anesthesia. Minerva Anestesiol 2007;73:451-7. [5] Cooper RM, Pacey JA, Bishop MJ, McClusky SA. Early experience with a new videolaryngoscope (GlideScope®) in 728 patients. Can J Anaesth 2005;52:191-8. [6] Heitz JW, Mastrando D. The use of a gum elastic bougie in combination with a videolaryngoscope. J Clin Anesth 2005;17:408-9 [Letter]. [7] Neustein SM. Advancing the endotracheal tube smoothly when using the GlideScope®. Can J Anaesth 2008;55:314 [Letter].
Reply Thank you for the opportunity to respond to the letter by Xue et al. The technique of using the endotracheal tube (ETT) as a conduit for the bougie is a rescue technique, to be used when the other manipulations mentioned in our letter have failed [1]. It is not our intention that this technique be used if intubation proves easy. As such, this technique is likely to be quicker and less complex than the commonly used alternatives when passage of the ETT through the glottis proves difficult, such as reshaping the stylet or using a different tube. We agree that this technique is not really suitable for small pediatric patients, but then neither are the McGrath and the GlideScope Cobalt videolaryngoscopes. Our recommendation requires that a suitably sized bougie be available. To facilitate the removal of the stylet from the ETT, especially past the proximal curvature of a RAE tube, we recommend the use of a suitable lubricant on the stylet, such as mineral oil or aqueous gel. The bougie is not inserted blindly but under direct vision using the videolaryngoscope. Of course, the bougie tip disappears from vision once it has passed beyond the glottis, but that is always the case when using a bougie. We hope that Xue and colleagues will try the suggested technique again, after lubricating the stylet, and we hope they will agree that it is a simple, quick and useful rescue technique.
Reference [1] Budde AO, Pott LM. Endotracheal tube as a guide for an Eschmann gum elastic bougie to aid tracheal intubation using the McGrath or GlideScope videolaryngoscopes. [Letter]J Clin Anesth 2008;20:560.
Faulty spring causing a gas leak To the Editor: Over the years there have been a number of case reports of gas leaks occurring from the back bar of the anesthetic machine [1-4]. Most of these reports have described vaporizer or seating faults. A case in which a faulty locking spring on the vaporizer seating was the cause of the problem is presented. A 25 year-old, ASA physical status I man presented for removal of orthopedic metalwork. The anesthetic machine (Datex Ohmeda Aestiva/5; Datex-Ohmeda; GE Healthcare, Chalfont St. Giles, Bucks, UK) was checked appropriately prior to commencement of the case, which was the first of the day. The TEC 5 Isoflurane vaporizer attached to the machine was found not to be properly locking onto the mounting on the back bar. The vaporizer was exchanged for another of the same type, which locked onto the back bar without any problems. The case was begun. After induction, fresh gas flows were set to deliver 6 L/min and the isoflurane vaporizer dial was set to deliver 2%. Inspired concentration of isoflurane was noted to be only 0.9% so the isoflurane vaporizer dial was increased to deliver 3%. Inspired isoflurane concentration at this stage increased to 1.8%. The fresh gas flows were reduced to 1.5 L/min, in line with maintaining low-flow anesthesia, and the percentage dialed on the isoflurane vaporizer remained unchanged. Inspired isoflurane concentration at this stage decreased to 0.7%. The decision was made to change the volatile agent being used to sevoflurane. Dialed and delivered sevoflurane remained consistent, even at low-flow. The patient remained stable and anesthetized throughout the procedure.
Leonard M. Pott MBBCh, FCA(SA) (Associate Professor) Department of Anesthesiology Pennsylvania State University Hershey, PA 17033, USA E-mail address: [email protected] Arne O. Budde MD, DEAA (Assistant Professor) Department of Anesthesiology Pennsylvania State University Hershey, PA 17033, USA doi:10.1016/j.jclinane.2009.02.002
Fig. 1 right.
View of faulty stretched spring on left, new spring on
Correspondence
383
References [1] Wilkinson D, Curtis C. A strange leak from the anaesthetic machine. Anaesthesia 2002;57:1038-9. [2] Ong BC, bin Katjo J, Tan BL, Lee CC, Chan YW. Acute failure of oxygen delivery. Anesthesiology 2001;95:1038-9. [3] Garstang JS. Gas leak from TEC 5 isoflurane vaporiser [Letter]. Anaesthesia 2000;55:915. [4] Lum ME. Fault in a Selectatec manifold resulting in awareness. Anaesth Intensive Care 1994;20:501-3.
Fig. 2
Location of spring, circled on back bar.
The machine was examined by members of the medical physics department. A spring into which the vaporizer locks on the back bar was found to be stretched out of shape and preventing secure locking of the vaporizer (Fig. 1). This spring is located in a small cavity between the two prongs onto which the vaporizer slots (Fig. 2). The medical physics department theorized that the first vaporizer on the machine was not locking, as it was not seated properly, and the spring was stretched by forcing the locking mechanism closed. The second vaporizer appeared to lock appropriately as the spring was not very distorted and the vaporizer was seated correctly. There was, however, enough damage to the spring to cause a leak of fresh gas flow at the point where it enters the vaporizer. This leak would have been of constant volume. It would, therefore, have constituted a small percentage of the fresh gas flow at high flows, which did not manifest as an appreciable leak during the case or during testing of the machine. When the flows were reduced, the leak made up a greater proportion of the total fresh gas flow and so had a greater effect on the amount of gas entering the vaporizer. No other users had reported problems and the machine had been recently serviced. Louise Terry MB BCh, BAO (Specialist Trainee) Department of Anesthesiology University Hospitals Birmingham Selly Oak, England B29 6JD E-mail address: [email protected] Egidio Joseph da Silva MB ChB, DA, FRCA, PGCME (Consultant) Department of Anesthesiology Royal Orthopaedic Hospital Birmingham, England B31 2AP doi:10.1016/j.jclinane.2008.11.003
Lateral femoral cutaneous neuropathy following lateral positioning on a bean bag To the Editor: Iatrogenic neuropathy of the lateral femoral cutaneous nerve (meralgia paresthetica) has been described after orthopedic procedures and following prone or lithotomy positioning. A patient who developed meralgia paresthetica after thoracoscopic surgery in the lateral position is presented. A 14-year-old, 81 kg boy was scheduled for thoracoscopic resection of a right-sided anterior mediastinal mass. After intravenous (IV) sedation, a thoracic epidural catheter was inserted uneventfully at the 7th thoracic interspace with the patient in the sitting position. Following IV induction with the patient placed supine, a left-sided double-lumen tube was inserted. The patient was then turned to the left lateral decubitus position on a bean bag of the older design without a gel surface. A gel axillary roll was placed. The bean bag extended from the patient's shoulder to his thigh. It was molded along the patient's front and back and evacuated. Arms and legs were padded in standard fashion. Thoracoscopic resection was performed uneventfully in a three-hour procedure. Intraoperative table movements were tolerated without apparent shift in the patient's position. His trachea was extubated at the end of the procedure while he was in the supine position, and he was comfortable when transferred to the recovery room. He had good surgical pain control with an epidural infusion of bupivacaine 0.1% with fentanyl 2 µg/mL and clonidine 0.4 µg/mL at 10 ml/hr, but he required ketorolac for management of bilateral shoulder pain. He ambulated with assistance. On postoperative day (POD) 3, the chest tube and the epidural catheter were removed and the patient was discharged home. He presented again on POD 6 to the surgeon with a two-day history (since discharge) of left leg pain affecting the outside of the left thigh, described as shooting and burning, with an area of numbness on the lateral aspect of the thigh. He was limping due to the pain but had no motor deficit. The epidural insertion site was benign and there was no back pain. Pain Management Service was involved on POD 8 and a diagnosis of lateral femoral cutaneous neuropathy was made. The patient was started on gabapentin 100 mg three times a day. The dose was incrementally increased to 400 mg three times a day. Transcutaneous nerve stimulation as well