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PAIN AND AWARENESS DURING GENERAL ANAESTHESIA
1033 PAIN AND AWARENESS DURING GENERAL ANAESTHESIA
SIR,-Although about 1% of patients experience awareness during general anaesthesial the subject is poorly documented and previous investigations have not generated enough cases for the experience to be characterised. To investigate this further I placed a small advertisement in the personal columns of three British newspapers asking readers to report instances of awareness during general anaesthesia. Further details of this investigation will be published elsewhere2 but three aspects deserve particular mention. 27 reports of awareness were obtained, relating to events up to 59 years previously (average 18 years); the experiences were clearly enduring. 21 patients found the experience disturbing and 9 of them thought it the worst experience of their lives; surprisingly, the other 6 did not. 20 of the 21 patients who found awareness disturbing had felt pain while only 2 of the 6 patients who were not disturbed had felt pain. This is consistent with the observation that patients who are aware during high-dose narcotic anaesthesia, as often used for open heart surgery, do not appear to report awareness in terms of any great distress; in contrast, almost all patients who take legal action in respect of awareness have experienced severe pain (L. Hargrove, personal communication). Thus the perception of pain during periods of awareness may cause patients very much distress. 3 reports described experiences during childhood, at the ages of 4, 4, and 7 years. Could awareness be more common in children than in adults? Anaesthesia requirements increase with decreasing age during most of childhood, and children are often lightly anaesthetised. In the only study of awareness in children McKie and Thorps found dreams and awareness reported in 11 % of cases, 5 % experiencing awareness. Thus the provision of adequate analgesia during anaesthesia should not only counter the physiological stress of surgery (as discussed in your Sept 5 editorial) but also guard against psychological stress and sequelae during periods of awareness; this may be especially important for children. The practical application of this policy presents a dilemma. Anaesthesia based largely upon narcotic analgesics is generally held to carry a greater risk of awareness-but the patient may be pain-free. On the other hand, anaesthesia based upon volatile agents is thought to have a lower risk of awareness but, for those patients who are aware, the experience may prove painful and unpleasant. Nuffield Department of Anaesthetics, Radcliffe Infirmary, Oxford OX2 6HE 1 2
3
JOHN M.
EVANS
Breckenndge JL, Aitkenhead AR Awareness during anaesthesia: a review Ann Roy Coll Surg Engl 1983; 65: 93-96. Evans JM. Patients’ expenences of awareness during general anaesthesia. In: Rosen M, Lunn JN, eds. Consciousness, awareness and pain in general anaesthesia. London: Butterworths (in press) Hilgenberg JC. Intra-operative awareness during high-dose fentanyl-oxygen
anesthesia. Anesthesiology 1981, 54: 341-43. 4. Mummaneni N, Rao TLK, Montoya A. Awareness and recall with high-dose fentanyl oxygen anesthesia Anesth Analg 1980; 59: 948-49. 5. McKie BD, Thorp EA. Awareness and dreaming dunng general anaesthesia in a paediatric hospital. Anaesth Intens Care 1973; 1; 407-14.
HYPERVENTILATION AND ANAESTHETIC REQUIREMENT IN BABIES
SiR,—Your Sept 5 editorial, which discusses the provision of adequate anaesthesia for premature and newborn infants, states that hyperventilation reduces the minimum alveolar concentration (MAC), a measure of anaesthetic potency, of nitrous oxide in babies. However, there is no evidence to support this statement. In contrast, studies contradict this supposition. In dogs, halothane MAC is not altered by reducing PCO from 42 to 14 mm Hg.1 In adults, halothane MAC does not differ in
normocapnic cases (PaC02 38 mm Hg) compared with hypocapnic patients (PaC02 21 mm Hg)The influence of hyperventilation ori nitrous oxide MAC has not beeri determined in adults or babies. Measurement of nitrous oxide MAC (1-04 atm absolute) in young adult volunteers under non-hyperventilating conditions required the use of a hyperbaric chamber.3Nitrous oxide MAC in babies is not known.
Hyperventilation does not alter MAC in adults. Although babies may be different from adults in this regard, studies demonstrating a decrease in nitrous oxide MAC in babies with hyperventilation have not yet been done. Department of Anesthesia, University of California, San Francisco,
DONALD D. KOBLIN
California 94121, USA 1. 2.
3.
Eger EI II, Saidman LJ, Brandstater B. Minimum alveolar anesthetic concentration: a standard of anesthetic potency. Anesthesiology 1965; 26: 756-63. Bridges BE, Eger EI II. The effect of hypocapnia on the level of halothane anesthesia in man. Anesthesiology 1966, 27: 634-37. Hornbein TF, Eger EI II, Winter PM, Smith G, Wetstone D, Smith KH. The minimum alveolar concentration of nitrous oxide in man. Anesth Analg 1982; 61: 533-36.
SiR,—The misapprehensions of those who reacted against Dr Anand and colleagues’ study are regrettable. But in another respect, it is impossible to use language too hyperbolic or excessive todescribe the practice which, though prevalent, was not discussed at length in your editorial-that of conducting major surgery of all types on premature and term infants with no pain relief or anaesthesia whatsoever, not even nitrous oxide. In 1985 our severely premature son had a ’Broviac’ catheter implanted and patent ductus arteriosus surgery over a period of 1 V2 hours. He was not moribund. He was not comatose. He was in no immediate danger from symptoms caused by his open ductus; rather the surgery was scheduled to increase his chances of a successful outcome over the long run. On the morning of the operation, planned 3 days in advance, his blood pressure was low and he became unstable when being taken to the theatre. Instead of waiting until he was stable the anaesthetist paralysed him, and he underwent thoracotomy with only oxygen and paralysing agents. I was later told that pain relief had been withheld not only because of low blood pressure but also because it had never been demonstrated that babies can feel pain. My son died 5 weeks later after a "worst-case" clinical course comparable with that described by Anand and colleagues for infants unprotected from surgical stress. What happened to my son meets the dictionary definition of vivisection. Even so I delayed going to the media for 7/2 months while trying to work with hospital staff, local and national associations, and regulatory bodies. If any one of them had taken action, I never would have "gone public". But not one did act, and the local medical society declared that the anaesthetist had done a good job. Thus public disclosure1 offered the only hope for promoting change in our medical community. Some reporting has been inaccurate. This happens when lay people are forced to enter the technically difficult world of physicians to defend their children. You may label some of their efforts inaccurate, inappropriate, or whatever-just please continue to help us. 9404 Piney Branch Road, Apt 205, Silver Spring, Maryland 20903, USA
1 Lawson
JR.
Letter
to
the editor Birth
JILL R. LAWSON 1986; 13: 125-26
MONITORING FOR ANAESTHESIA
SIR,-Your Sept 26 editorial
on monitoring during anaesthesia discuss monitor design. Anaesthetists may welcome guidance on the mass of devices (and information derived from them) now on offer from equipment manufacturers. Monitors designed for use in theatre usually contain microprocessors which can perform a variety of functions. Selftesting apart, the machines provide a range of alarms and information from basic data to complex trend analyses. If anaesthesia is progressing smoothly these displays can be examined at leisure. However, if the monitor detects a problem, the alarm and display systems are often so complex that a significant amount of time can be spent trying to find out what has changed and turning off the alarms, which can be distracting. Occasionally essential information has to be obtained by interrogating the monitor via a key system, which means more time and attention being deflected from the patienti
did
not
SIR,-Although about 1% of patients experience awareness during general anaesthesial the subject is poorly documented and previous investigations have not generated enough cases for the experience to be characterised. To investigate this further I placed a small advertisement in the personal columns of three British newspapers asking readers to report instances of awareness during general anaesthesia. Further details of this investigation will be published elsewhere2 but three aspects deserve particular mention. 27 reports of awareness were obtained, relating to events up to 59 years previously (average 18 years); the experiences were clearly enduring. 21 patients found the experience disturbing and 9 of them thought it the worst experience of their lives; surprisingly, the other 6 did not. 20 of the 21 patients who found awareness disturbing had felt pain while only 2 of the 6 patients who were not disturbed had felt pain. This is consistent with the observation that patients who are aware during high-dose narcotic anaesthesia, as often used for open heart surgery, do not appear to report awareness in terms of any great distress; in contrast, almost all patients who take legal action in respect of awareness have experienced severe pain (L. Hargrove, personal communication). Thus the perception of pain during periods of awareness may cause patients very much distress. 3 reports described experiences during childhood, at the ages of 4, 4, and 7 years. Could awareness be more common in children than in adults? Anaesthesia requirements increase with decreasing age during most of childhood, and children are often lightly anaesthetised. In the only study of awareness in children McKie and Thorps found dreams and awareness reported in 11 % of cases, 5 % experiencing awareness. Thus the provision of adequate analgesia during anaesthesia should not only counter the physiological stress of surgery (as discussed in your Sept 5 editorial) but also guard against psychological stress and sequelae during periods of awareness; this may be especially important for children. The practical application of this policy presents a dilemma. Anaesthesia based largely upon narcotic analgesics is generally held to carry a greater risk of awareness-but the patient may be pain-free. On the other hand, anaesthesia based upon volatile agents is thought to have a lower risk of awareness but, for those patients who are aware, the experience may prove painful and unpleasant. Nuffield Department of Anaesthetics, Radcliffe Infirmary, Oxford OX2 6HE 1 2
3
JOHN M.
EVANS
Breckenndge JL, Aitkenhead AR Awareness during anaesthesia: a review Ann Roy Coll Surg Engl 1983; 65: 93-96. Evans JM. Patients’ expenences of awareness during general anaesthesia. In: Rosen M, Lunn JN, eds. Consciousness, awareness and pain in general anaesthesia. London: Butterworths (in press) Hilgenberg JC. Intra-operative awareness during high-dose fentanyl-oxygen
anesthesia. Anesthesiology 1981, 54: 341-43. 4. Mummaneni N, Rao TLK, Montoya A. Awareness and recall with high-dose fentanyl oxygen anesthesia Anesth Analg 1980; 59: 948-49. 5. McKie BD, Thorp EA. Awareness and dreaming dunng general anaesthesia in a paediatric hospital. Anaesth Intens Care 1973; 1; 407-14.
HYPERVENTILATION AND ANAESTHETIC REQUIREMENT IN BABIES
SiR,—Your Sept 5 editorial, which discusses the provision of adequate anaesthesia for premature and newborn infants, states that hyperventilation reduces the minimum alveolar concentration (MAC), a measure of anaesthetic potency, of nitrous oxide in babies. However, there is no evidence to support this statement. In contrast, studies contradict this supposition. In dogs, halothane MAC is not altered by reducing PCO from 42 to 14 mm Hg.1 In adults, halothane MAC does not differ in
normocapnic cases (PaC02 38 mm Hg) compared with hypocapnic patients (PaC02 21 mm Hg)The influence of hyperventilation ori nitrous oxide MAC has not beeri determined in adults or babies. Measurement of nitrous oxide MAC (1-04 atm absolute) in young adult volunteers under non-hyperventilating conditions required the use of a hyperbaric chamber.3Nitrous oxide MAC in babies is not known.
Hyperventilation does not alter MAC in adults. Although babies may be different from adults in this regard, studies demonstrating a decrease in nitrous oxide MAC in babies with hyperventilation have not yet been done. Department of Anesthesia, University of California, San Francisco,
DONALD D. KOBLIN
California 94121, USA 1. 2.
3.
Eger EI II, Saidman LJ, Brandstater B. Minimum alveolar anesthetic concentration: a standard of anesthetic potency. Anesthesiology 1965; 26: 756-63. Bridges BE, Eger EI II. The effect of hypocapnia on the level of halothane anesthesia in man. Anesthesiology 1966, 27: 634-37. Hornbein TF, Eger EI II, Winter PM, Smith G, Wetstone D, Smith KH. The minimum alveolar concentration of nitrous oxide in man. Anesth Analg 1982; 61: 533-36.
SiR,—The misapprehensions of those who reacted against Dr Anand and colleagues’ study are regrettable. But in another respect, it is impossible to use language too hyperbolic or excessive todescribe the practice which, though prevalent, was not discussed at length in your editorial-that of conducting major surgery of all types on premature and term infants with no pain relief or anaesthesia whatsoever, not even nitrous oxide. In 1985 our severely premature son had a ’Broviac’ catheter implanted and patent ductus arteriosus surgery over a period of 1 V2 hours. He was not moribund. He was not comatose. He was in no immediate danger from symptoms caused by his open ductus; rather the surgery was scheduled to increase his chances of a successful outcome over the long run. On the morning of the operation, planned 3 days in advance, his blood pressure was low and he became unstable when being taken to the theatre. Instead of waiting until he was stable the anaesthetist paralysed him, and he underwent thoracotomy with only oxygen and paralysing agents. I was later told that pain relief had been withheld not only because of low blood pressure but also because it had never been demonstrated that babies can feel pain. My son died 5 weeks later after a "worst-case" clinical course comparable with that described by Anand and colleagues for infants unprotected from surgical stress. What happened to my son meets the dictionary definition of vivisection. Even so I delayed going to the media for 7/2 months while trying to work with hospital staff, local and national associations, and regulatory bodies. If any one of them had taken action, I never would have "gone public". But not one did act, and the local medical society declared that the anaesthetist had done a good job. Thus public disclosure1 offered the only hope for promoting change in our medical community. Some reporting has been inaccurate. This happens when lay people are forced to enter the technically difficult world of physicians to defend their children. You may label some of their efforts inaccurate, inappropriate, or whatever-just please continue to help us. 9404 Piney Branch Road, Apt 205, Silver Spring, Maryland 20903, USA
1 Lawson
JR.
Letter
to
the editor Birth
JILL R. LAWSON 1986; 13: 125-26
MONITORING FOR ANAESTHESIA
SIR,-Your Sept 26 editorial
on monitoring during anaesthesia discuss monitor design. Anaesthetists may welcome guidance on the mass of devices (and information derived from them) now on offer from equipment manufacturers. Monitors designed for use in theatre usually contain microprocessors which can perform a variety of functions. Selftesting apart, the machines provide a range of alarms and information from basic data to complex trend analyses. If anaesthesia is progressing smoothly these displays can be examined at leisure. However, if the monitor detects a problem, the alarm and display systems are often so complex that a significant amount of time can be spent trying to find out what has changed and turning off the alarms, which can be distracting. Occasionally essential information has to be obtained by interrogating the monitor via a key system, which means more time and attention being deflected from the patienti
did
not