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ANAESTHETIC ACCIDENT CAUSED BY UNUSUAL LEAKAGE OF ROTAMETER
Br.J. Anaesth. (1976), 48, 499
CORRESPONDENCE A SIMPLE SAFETY DEVICE
Sir,—I agree with Dr E. G. Star (1975) that disconnection of anaesthetic tubing is a common and potentially lethal hazard. This is especially dangerous when the head and neck of a patient are covered by surgical drapes. Figure 1
shows a large-bore anaesthetic connector for endotracheal tubes which has a spiral bayonet, ensuring seal of the taper cone and compensating for wear. This connector of unknown manufacture has been used for about 30 years and is in routine use still for the operation of laryngectomy at our hospital. I consider that this spiral taper is a more satisfactory safeguard than either the straight bayonet described by Dr Star (1975) or a screw-thread connection which is more easily damaged. P. F. DOLAN
Cardiff REFERENCE
Star, E. G. (1975). A simple safety device. Br. J. Anaesth.. 47, 1034.
J. A. MULIYIL
Indian Oxygen Ltd, Calcutta, India REFERENCE
ANAESTHETIC ACCIDENT CAUSED BY UNUSUAL LEAKAGE OF ROTAMETER
Editorial Note As a result of an error in transcription, the impression was conveyed that the first patient referred to in the letter by Gupta and Varshneya (1975) {Br.J. Anaesth., 47, 805) did not recover. In fact, the patient made an eventual recovery from the cardiac arrest. Sir,—I should like to make some observations on the recent letter by Gupta and Varshneya (1975). Our enquiries have revealed that the apparatus concerned was serviced on March 26/27, 1974, and taken over in good working order by the hospital authorities. The first incident took place in the first week of April 1974. It would appear, therefore, that
Gupta, B. L., and Varshneya, A. K. (1975). Anaesthetic accident caused by unusual leakage of rotameter. Br. J. Anaesth., 47, 805. Sir,—I was interested to read the recent report on anaesthetic accidents produced by leakage from a flowmeter bank (Gupta and Varshneya, 1975). It is now time that the flowmeter arrangement on the Boyles machine is modified. In most of the anaesthetic machines of U.K. manufacture, the oxygen flowmeter is on the left-hand side and the nitrous oxide flowmeter is on the right-hand side of the flowmeter bank. If the flowmeter positions are interchanged (that is, the oxygen flowmeter is placed on the right-hand side and the nitrous oxide on the left-hand side) as seen on most of the machines of U.S. origin, hypoxic mixtures are unlikely to be produced. The oxygen flowmeter should be
Downloaded from http://bja.oxfordjournals.org/ at Yale University on July 3, 2015
FIG. 1. Modification to an endotracheal tube connection.
the defect mentioned developed subsequent to the servicing, and that until the incident of April 1974 the apparatus was giving good service. We agree entirely that where the safety of human life is involved it is necessary to ensure that the risk of accidents is eliminated and there should be safeguards against the possibility of recurrence of this type of accident in future. Therefore our company has made a very careful review of the facts that have emerged from this incident and we have decided to take certain steps to refine further the system of testing the apparatus at the time of the usual servicing that is carried out by our service engineers at periodic intervals. Briefly, we propose to provide our service engineers with a plug-in manometer with a preset pressure relief valve. The service engineer, or the user, will obtain a warning if leakages above acceptable limits exist within the system, by noting the time required for the pressure to increase to (say) 60 cm H 2 O pressure when oxygen isflowingat a preset value of 100 ml/min and the time required for it to decrease to 30 cm H 2 O when the oxygen flow is stopped. It has been decided also to make available to staff of hospitals and other institutions using anaesthesia apparatus, the equipment described above which will enable them to check, before each operation, that the rotating bobbin flowmeters are in perfect working order and that there are no leaks. We are also arranging to make explicit, in future editions of the Instruction Manual that is issued with every set sold by our company, that the apparatus should be checked before each operation, and we are arranging to provide a check-list in this Manual for the guidance of anaesthetists and others handling the equipment. In addition, we are writing to the Indian Government recommending that institutions using anaesthesia apparatus should be allowed to import spirometers. Even though the precautions that we are making to refine our testing system and to make available the type of equipment described above to hospital staff should be adequate, it is felt that the availability of spirometers will be an additional safeguard.
500 near the outlet of the machine (Dorsch and Dorsch, 1975). Other preventive devices are the use of baffle systems (Dorsch and Dorsch, 1975), or an oxygen guide-tube to direct the oxygen flow to the outlet of the machine (Katz, 1969). Other instances of hypoxic mixtures from a defective flowmeter have been reported already (Katz, 1968; Bishop, Levick and Hodgeson, 1967). I hope that the manufacturers of anaesthetic equipment will take note of the most recently reported accident (Gupta and Varshneya, 1975).
BRITISH JOURNAL OF ANAESTHESIA REFERENCES
Downloaded from http://bja.oxfordjournals.org/ at Yale University on July 3, 2015
Bishop, C , Levick, C. H., and Hodgeson, C. A. (1967). A design fault in the Boyle apparatus. Br. J. Anaesth., 39, 908. Eger, E. I., Hylton, R. R., Irwin, R. H., and Guadagni, N. (1963). Anaesthetic flow meter sequence—a cause for hypoxia. Anesthesiology, 24, 396. Gupta, B. L., and Varshneya, A. K. (1975). Anaesthetic accident caused by unusual leakage of rotameter. Br. J. Anaesth., 47, 805. J. P. VARSHNEY Katz, D. (1968). Recurring cyanosis of intermittent Meerut, India mechanical origin in anesthetised patients. Anesth. REFERENCES Analg. (Cleve.), 17, 233. (1969). Increasing the safety of anesthesia machines. Bishop, C , Levick, C. H., and Hodgeson, C. A. (1967). A I: Further modification to the Draeger machine. II: design fault in the Boyle apparatus. Br.J. Anaesth.,39,908. Consideration for the standardization of certain basic Dorsch, J. A., and Dorsch, S. E. (1975). Understanding of components. Anesth. Analg. (.Cleve.), 48, 242. Anesthesia Equipment, p. 48. Baltimore: Williams & Llew, P. C , and Ganandran, A. (1973). Oxygen failure: a Wilkins. potential danger with air-flowmeters in anaesthetic Gupta, B. L., and Varshneya, A. K. (1975). Anaesthetic machines with remote controlled needle-valves. Br. J. accident caused by unnusual leakage of rotameter. Anaesth., 45, 1165. Br. J. Anaesth., 47, 805. Katz, D. (1968). Recurring cyanosis of intermittent Wilson, M. E. (1975). Design of anaesthesia apparatus. Lancet, 2, 35. mechanical origin in anesthetised patients. Anesth. Analg. {Cleve.), 47, 233. CANNULATION OF THE FEMORAL VESSELS (1969). Increasing the safety of anesthesia machines. I: Further modification to the Draeger machine. II: Sir,—Internal jugular and subclavian vein cannulation Consideration for the standardization of certain basic are now well-established techniques for immediate and long-term therapy and monitoring. Occasionally they are components. Anesth. Analg. {Cleve.), 48, 242. difficult or unsuccessful, when the femoral vein is an Sir,—The report by Gupta and Varshneya (1975) of important alternative, especially in an emergency or for cardiac arrest in two patients, resulting from the escape of cardiac surgery. The femoral artery also can be cannuoxygen from the flowmeter housing before delivery to the lated when other arterial routes fail. patient, gives further emphasis to the plea of Wilson (1975) Because of its disadvantages, in particular the risk of for coherent international agreement on the controls of infection or venous thrombosis, femoral vessel cannulaanaesthetic apparatus. tion is not taught widely, although it is usually easy. It These two incidents are the most recent of a number of has been simplified by the introduction of the 14-cm Bard reports since Eger and others (1963) suggested that the Teflon cannula (C. R. Bard Inc., Murray Hill, New Jersey problem be solved by putting the oxygen flowmeter 07974, U.S.A.) and the very similar Deseret Angiocath nearest the outlet of the flowmeter block on the right (Deseret Pharmaceutical Co., Sandy, Utah 84070, U.S.A.). (Bishop, Levick and Hodgeson, 1967; Katz, 1968, 1969; Llew and Ganandran, 1973). There is little doubt that the simplest and least expensive solution to the problem would be to have an authorized serviceman change the oxygen flowmeter to the right-hand position, which could be carried out in the hospital. It has been argued that there would be an increased hazard and confusion during the change-over period, but if this were carried out on a hospital or hospital area basis with suitable publicity, the re-education programme should not be too difficult. The reason for suggesting this solution is that the alternative would require a bypass to be fitted within the flowmeter block to deliver oxygen to the outlet. This would necessitate a different internal fitting for each design of flowmeter block. This might involve the despatch of the machine to the manufacturer at considerable expense. The cost and inconvenience would inevitably delay the elimination of this hazard. I would urge, therefore, that we consider making the change to a uniform design of the oxygen flowmeter on the FIG. 1. Once blood can be aspirated freely, the cannula is right, nearest to the outlet of the rotameter block. smoothly inserted along the needle into the vessel. Even the slightest resistance indicates incorrect insertion. The L. RENDELL-BAKER cannula is best anchored with a skin stitch. New York
CORRESPONDENCE A SIMPLE SAFETY DEVICE
Sir,—I agree with Dr E. G. Star (1975) that disconnection of anaesthetic tubing is a common and potentially lethal hazard. This is especially dangerous when the head and neck of a patient are covered by surgical drapes. Figure 1
shows a large-bore anaesthetic connector for endotracheal tubes which has a spiral bayonet, ensuring seal of the taper cone and compensating for wear. This connector of unknown manufacture has been used for about 30 years and is in routine use still for the operation of laryngectomy at our hospital. I consider that this spiral taper is a more satisfactory safeguard than either the straight bayonet described by Dr Star (1975) or a screw-thread connection which is more easily damaged. P. F. DOLAN
Cardiff REFERENCE
Star, E. G. (1975). A simple safety device. Br. J. Anaesth.. 47, 1034.
J. A. MULIYIL
Indian Oxygen Ltd, Calcutta, India REFERENCE
ANAESTHETIC ACCIDENT CAUSED BY UNUSUAL LEAKAGE OF ROTAMETER
Editorial Note As a result of an error in transcription, the impression was conveyed that the first patient referred to in the letter by Gupta and Varshneya (1975) {Br.J. Anaesth., 47, 805) did not recover. In fact, the patient made an eventual recovery from the cardiac arrest. Sir,—I should like to make some observations on the recent letter by Gupta and Varshneya (1975). Our enquiries have revealed that the apparatus concerned was serviced on March 26/27, 1974, and taken over in good working order by the hospital authorities. The first incident took place in the first week of April 1974. It would appear, therefore, that
Gupta, B. L., and Varshneya, A. K. (1975). Anaesthetic accident caused by unusual leakage of rotameter. Br. J. Anaesth., 47, 805. Sir,—I was interested to read the recent report on anaesthetic accidents produced by leakage from a flowmeter bank (Gupta and Varshneya, 1975). It is now time that the flowmeter arrangement on the Boyles machine is modified. In most of the anaesthetic machines of U.K. manufacture, the oxygen flowmeter is on the left-hand side and the nitrous oxide flowmeter is on the right-hand side of the flowmeter bank. If the flowmeter positions are interchanged (that is, the oxygen flowmeter is placed on the right-hand side and the nitrous oxide on the left-hand side) as seen on most of the machines of U.S. origin, hypoxic mixtures are unlikely to be produced. The oxygen flowmeter should be
Downloaded from http://bja.oxfordjournals.org/ at Yale University on July 3, 2015
FIG. 1. Modification to an endotracheal tube connection.
the defect mentioned developed subsequent to the servicing, and that until the incident of April 1974 the apparatus was giving good service. We agree entirely that where the safety of human life is involved it is necessary to ensure that the risk of accidents is eliminated and there should be safeguards against the possibility of recurrence of this type of accident in future. Therefore our company has made a very careful review of the facts that have emerged from this incident and we have decided to take certain steps to refine further the system of testing the apparatus at the time of the usual servicing that is carried out by our service engineers at periodic intervals. Briefly, we propose to provide our service engineers with a plug-in manometer with a preset pressure relief valve. The service engineer, or the user, will obtain a warning if leakages above acceptable limits exist within the system, by noting the time required for the pressure to increase to (say) 60 cm H 2 O pressure when oxygen isflowingat a preset value of 100 ml/min and the time required for it to decrease to 30 cm H 2 O when the oxygen flow is stopped. It has been decided also to make available to staff of hospitals and other institutions using anaesthesia apparatus, the equipment described above which will enable them to check, before each operation, that the rotating bobbin flowmeters are in perfect working order and that there are no leaks. We are also arranging to make explicit, in future editions of the Instruction Manual that is issued with every set sold by our company, that the apparatus should be checked before each operation, and we are arranging to provide a check-list in this Manual for the guidance of anaesthetists and others handling the equipment. In addition, we are writing to the Indian Government recommending that institutions using anaesthesia apparatus should be allowed to import spirometers. Even though the precautions that we are making to refine our testing system and to make available the type of equipment described above to hospital staff should be adequate, it is felt that the availability of spirometers will be an additional safeguard.
500 near the outlet of the machine (Dorsch and Dorsch, 1975). Other preventive devices are the use of baffle systems (Dorsch and Dorsch, 1975), or an oxygen guide-tube to direct the oxygen flow to the outlet of the machine (Katz, 1969). Other instances of hypoxic mixtures from a defective flowmeter have been reported already (Katz, 1968; Bishop, Levick and Hodgeson, 1967). I hope that the manufacturers of anaesthetic equipment will take note of the most recently reported accident (Gupta and Varshneya, 1975).
BRITISH JOURNAL OF ANAESTHESIA REFERENCES
Downloaded from http://bja.oxfordjournals.org/ at Yale University on July 3, 2015
Bishop, C , Levick, C. H., and Hodgeson, C. A. (1967). A design fault in the Boyle apparatus. Br. J. Anaesth., 39, 908. Eger, E. I., Hylton, R. R., Irwin, R. H., and Guadagni, N. (1963). Anaesthetic flow meter sequence—a cause for hypoxia. Anesthesiology, 24, 396. Gupta, B. L., and Varshneya, A. K. (1975). Anaesthetic accident caused by unusual leakage of rotameter. Br. J. Anaesth., 47, 805. J. P. VARSHNEY Katz, D. (1968). Recurring cyanosis of intermittent Meerut, India mechanical origin in anesthetised patients. Anesth. REFERENCES Analg. (Cleve.), 17, 233. (1969). Increasing the safety of anesthesia machines. Bishop, C , Levick, C. H., and Hodgeson, C. A. (1967). A I: Further modification to the Draeger machine. II: design fault in the Boyle apparatus. Br.J. Anaesth.,39,908. Consideration for the standardization of certain basic Dorsch, J. A., and Dorsch, S. E. (1975). Understanding of components. Anesth. Analg. (.Cleve.), 48, 242. Anesthesia Equipment, p. 48. Baltimore: Williams & Llew, P. C , and Ganandran, A. (1973). Oxygen failure: a Wilkins. potential danger with air-flowmeters in anaesthetic Gupta, B. L., and Varshneya, A. K. (1975). Anaesthetic machines with remote controlled needle-valves. Br. J. accident caused by unnusual leakage of rotameter. Anaesth., 45, 1165. Br. J. Anaesth., 47, 805. Katz, D. (1968). Recurring cyanosis of intermittent Wilson, M. E. (1975). Design of anaesthesia apparatus. Lancet, 2, 35. mechanical origin in anesthetised patients. Anesth. Analg. {Cleve.), 47, 233. CANNULATION OF THE FEMORAL VESSELS (1969). Increasing the safety of anesthesia machines. I: Further modification to the Draeger machine. II: Sir,—Internal jugular and subclavian vein cannulation Consideration for the standardization of certain basic are now well-established techniques for immediate and long-term therapy and monitoring. Occasionally they are components. Anesth. Analg. {Cleve.), 48, 242. difficult or unsuccessful, when the femoral vein is an Sir,—The report by Gupta and Varshneya (1975) of important alternative, especially in an emergency or for cardiac arrest in two patients, resulting from the escape of cardiac surgery. The femoral artery also can be cannuoxygen from the flowmeter housing before delivery to the lated when other arterial routes fail. patient, gives further emphasis to the plea of Wilson (1975) Because of its disadvantages, in particular the risk of for coherent international agreement on the controls of infection or venous thrombosis, femoral vessel cannulaanaesthetic apparatus. tion is not taught widely, although it is usually easy. It These two incidents are the most recent of a number of has been simplified by the introduction of the 14-cm Bard reports since Eger and others (1963) suggested that the Teflon cannula (C. R. Bard Inc., Murray Hill, New Jersey problem be solved by putting the oxygen flowmeter 07974, U.S.A.) and the very similar Deseret Angiocath nearest the outlet of the flowmeter block on the right (Deseret Pharmaceutical Co., Sandy, Utah 84070, U.S.A.). (Bishop, Levick and Hodgeson, 1967; Katz, 1968, 1969; Llew and Ganandran, 1973). There is little doubt that the simplest and least expensive solution to the problem would be to have an authorized serviceman change the oxygen flowmeter to the right-hand position, which could be carried out in the hospital. It has been argued that there would be an increased hazard and confusion during the change-over period, but if this were carried out on a hospital or hospital area basis with suitable publicity, the re-education programme should not be too difficult. The reason for suggesting this solution is that the alternative would require a bypass to be fitted within the flowmeter block to deliver oxygen to the outlet. This would necessitate a different internal fitting for each design of flowmeter block. This might involve the despatch of the machine to the manufacturer at considerable expense. The cost and inconvenience would inevitably delay the elimination of this hazard. I would urge, therefore, that we consider making the change to a uniform design of the oxygen flowmeter on the FIG. 1. Once blood can be aspirated freely, the cannula is right, nearest to the outlet of the rotameter block. smoothly inserted along the needle into the vessel. Even the slightest resistance indicates incorrect insertion. The L. RENDELL-BAKER cannula is best anchored with a skin stitch. New York