- Email: [email protected]
Awareness during anaesthesia
CORRESPONDENCE
Sir—In his commentary on awareness in anaesthesia, Bruno Simini1 rightly emphasises that postoperative memory of intraoperative events is only the most extreme (and presumably least frequent) part of the phenomenon. On the other hand it is not possible to get any impression of unconscious perception. The patients with awareness described in the study by Rolf Sardin and colleagues2 seem to have had only temporary recall, but it is only a matter of belief (or hope) to imagine that all perception was then simultaneously switched off. Anaesthesia is, as Simini initially states, an “indeterminable state”. There can be no doubt that what is commonly understood as awareness in anaesthesia is undesirable and potentially harmful. It is quite possible that such awareness during anaesthesia occurs all the time, or at least very often, without necessarily causing harm to the patients. How can you prevent something which occurs very often, do you need to prevent it, and are other measures necessary? The differences between sleep and anaesthesia is an ill-explored area.3 Patients and surgeons expect sleep during anaesthesia and it is generally possible to provide this impression (no recall of intraoperative events). However, anaesthetists should not believe that no intraoperative awareness will occur. Patients should be treated with respect during anaesthesia in case of awareness: no personal remarks should be made and there should be no discussion of metastasis or bad prognosis.4 Such restriction to comment would be difficult for surgeons who expect total unconsciousness in their patients. Even if benzodiazepines fail to prevent recall of intraoperative events, they may, in the condition of unconscious awareness, be useful as anxiolytics (which is, of course, entirely speculative). Use of devices such as electroencephalography could mislead the anaesthetist to use more anaesthetic than would be good for the patient, in terms of recovery from an operation. The method used by Sandin and colleagues for finding 19 cases of awareness among 11 785 patients was laborious but valuable. Following surgery patients should be asked about conscious awareness (or bad dreams) upon discharge from recovery, and anaesthetists should be alerted to positive reports. Postoperative questioning 1 day or more after surgery should be considered part of
THE LANCET • Vol 355 • May 13, 2000
the anaesthetist’s job, because it will prompt precautions against this and other adverse consequences and allow patients to receive therapy when necessary. John Schou County Hospitals, D-79539 Lörrach, Germany (e-mail: [email protected]) 1
2
3 4
Simini B. Awareness of awareness during general anaesthesia. Lancet 2000; 355: 672–74. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: a prospective case study. Lancet 2000; 355: 707–11. Schou J. A philsophical approach to anaesthesia. Copenhagen: Alix Publ, 1994. Bennett HL. Influencing the brain with information during general anaesthesia: a theory of unconscious hearing. In: Bonke B, Fitch W, Millar K, eds. Memory and awareness in anaesthesia. Amsterdam: Swets & Zeitlinger, 1990: 50–56.
A rockwool fibre worker with lung fibrosis Sir—Richard Hubbard and colleagues (Feb 5, p 466)1 describe the increased mortality from cryoptogenic fibrosing alveolitis in metal-workers. We describe a case of rockwool-induced lung fibrosis, in a patient who had a history of rockwool inhalation for 12 years. A man aged 72 years was admitted to the Tohoku University Hospital, Sendai, Japan, in Sept, 1998, because of progressive pleural thickness in the lower and apical part of the right lung, and reticular shadows in the lower lobe of both sides of the lung seen on chest radiographs. In the preceding 12 years, the patient had been employed full time as a rockwool spray insulator.
Rockwool is a man-made mineral fibre. He smoked 10 cigarettes a day for 20 years. A chest radiograph done before he started this work showed no abnormal shadows. He had no cough, sputum, dyspnoea, or fever. A computed-tomography (CT) scan of his chest showed pleural thickness and calcification, linear, trabecular, and round nodular shadows on both sides of the lower lobes of both lungs. The heart was normal but he had crepitations of lung sounds in both sides of the lower lung field. PaO2 was 78 mm Hg, PaCO2 was 42 mm Hg, and pH was 7·44 (breathing room air). Spirometry showed a mild restrictive impairment with a forced vital capacity of 72% and a forced expiratory volume in 1 s of 92%. Peripheral blood and serum were normal for all values tested. Autoimmune antibodies including antibodies to nuclei and DNA were negative. Light-microscope examination of lung tissue from the round nodular shadow obtained by aspiration needle lung biopsy guided by the CT scan, showed interstitial pulmonary fibrosis with hypertrophy of the alveolar wall and foreign-body deposition. No asbestos body, inflammatory granuloma, lung cancer, or malignant methothelioma was found. Electron-microscope examination of the same lung specimen showed nonstructural fibres (<2·5 m long and 0·3 m in diameter), which had identical dimensions to rockwool fibre (figure). Man-made mineral fibres, including rockwool, have been widely used because of their thermal, acoustic, and fire-resistance properties and to reduce asbestos use. Man-made mineral fibres have been said not to induce the lung fibrosis seen in
Electron microscopy shows deposition of nonstructural fibres in the macrophages (black arrows)
1723
Sir—In his commentary on awareness in anaesthesia, Bruno Simini1 rightly emphasises that postoperative memory of intraoperative events is only the most extreme (and presumably least frequent) part of the phenomenon. On the other hand it is not possible to get any impression of unconscious perception. The patients with awareness described in the study by Rolf Sardin and colleagues2 seem to have had only temporary recall, but it is only a matter of belief (or hope) to imagine that all perception was then simultaneously switched off. Anaesthesia is, as Simini initially states, an “indeterminable state”. There can be no doubt that what is commonly understood as awareness in anaesthesia is undesirable and potentially harmful. It is quite possible that such awareness during anaesthesia occurs all the time, or at least very often, without necessarily causing harm to the patients. How can you prevent something which occurs very often, do you need to prevent it, and are other measures necessary? The differences between sleep and anaesthesia is an ill-explored area.3 Patients and surgeons expect sleep during anaesthesia and it is generally possible to provide this impression (no recall of intraoperative events). However, anaesthetists should not believe that no intraoperative awareness will occur. Patients should be treated with respect during anaesthesia in case of awareness: no personal remarks should be made and there should be no discussion of metastasis or bad prognosis.4 Such restriction to comment would be difficult for surgeons who expect total unconsciousness in their patients. Even if benzodiazepines fail to prevent recall of intraoperative events, they may, in the condition of unconscious awareness, be useful as anxiolytics (which is, of course, entirely speculative). Use of devices such as electroencephalography could mislead the anaesthetist to use more anaesthetic than would be good for the patient, in terms of recovery from an operation. The method used by Sandin and colleagues for finding 19 cases of awareness among 11 785 patients was laborious but valuable. Following surgery patients should be asked about conscious awareness (or bad dreams) upon discharge from recovery, and anaesthetists should be alerted to positive reports. Postoperative questioning 1 day or more after surgery should be considered part of
THE LANCET • Vol 355 • May 13, 2000
the anaesthetist’s job, because it will prompt precautions against this and other adverse consequences and allow patients to receive therapy when necessary. John Schou County Hospitals, D-79539 Lörrach, Germany (e-mail: [email protected]) 1
2
3 4
Simini B. Awareness of awareness during general anaesthesia. Lancet 2000; 355: 672–74. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: a prospective case study. Lancet 2000; 355: 707–11. Schou J. A philsophical approach to anaesthesia. Copenhagen: Alix Publ, 1994. Bennett HL. Influencing the brain with information during general anaesthesia: a theory of unconscious hearing. In: Bonke B, Fitch W, Millar K, eds. Memory and awareness in anaesthesia. Amsterdam: Swets & Zeitlinger, 1990: 50–56.
A rockwool fibre worker with lung fibrosis Sir—Richard Hubbard and colleagues (Feb 5, p 466)1 describe the increased mortality from cryoptogenic fibrosing alveolitis in metal-workers. We describe a case of rockwool-induced lung fibrosis, in a patient who had a history of rockwool inhalation for 12 years. A man aged 72 years was admitted to the Tohoku University Hospital, Sendai, Japan, in Sept, 1998, because of progressive pleural thickness in the lower and apical part of the right lung, and reticular shadows in the lower lobe of both sides of the lung seen on chest radiographs. In the preceding 12 years, the patient had been employed full time as a rockwool spray insulator.
Rockwool is a man-made mineral fibre. He smoked 10 cigarettes a day for 20 years. A chest radiograph done before he started this work showed no abnormal shadows. He had no cough, sputum, dyspnoea, or fever. A computed-tomography (CT) scan of his chest showed pleural thickness and calcification, linear, trabecular, and round nodular shadows on both sides of the lower lobes of both lungs. The heart was normal but he had crepitations of lung sounds in both sides of the lower lung field. PaO2 was 78 mm Hg, PaCO2 was 42 mm Hg, and pH was 7·44 (breathing room air). Spirometry showed a mild restrictive impairment with a forced vital capacity of 72% and a forced expiratory volume in 1 s of 92%. Peripheral blood and serum were normal for all values tested. Autoimmune antibodies including antibodies to nuclei and DNA were negative. Light-microscope examination of lung tissue from the round nodular shadow obtained by aspiration needle lung biopsy guided by the CT scan, showed interstitial pulmonary fibrosis with hypertrophy of the alveolar wall and foreign-body deposition. No asbestos body, inflammatory granuloma, lung cancer, or malignant methothelioma was found. Electron-microscope examination of the same lung specimen showed nonstructural fibres (<2·5 m long and 0·3 m in diameter), which had identical dimensions to rockwool fibre (figure). Man-made mineral fibres, including rockwool, have been widely used because of their thermal, acoustic, and fire-resistance properties and to reduce asbestos use. Man-made mineral fibres have been said not to induce the lung fibrosis seen in
Electron microscopy shows deposition of nonstructural fibres in the macrophages (black arrows)
1723