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The use of methohexitone in sleep electroencephalography
Electroencephalography and Clinical Neurophysiology Elsevier Publishing Company, Amsterdam - Printed in The Netherlands
273
THE USE OF METHOHEXITONE IN SLEEP
ELECTROENCEPHALOGRAPHY GEORGE W . FENTON AND LEILA SCOTTON
Academic Department of Psychiatry, Middlesex Hospital Medical School, London, W. 1 (Great Britain) (Accepted for publication: February 20, 1967)
Oral quinalbarbitone and intravenous thiopentone sodium are the two barbiturates most commonly used to induce sleep in the E E G laboratory (Aungle et al. 1954). Although thiopentone has the advantage that the rate of onset, level and duration of sleep can be more readily controlled, its disadvantages include the risks of perivenous and intra-arterial injections and occasional delayed recovery of consciousness and return of mental faculties (Barron and Dundee 1961). Methohexitone sodium, a recently introduced ultrashort-acting barbiturate appears to lack these defects. In servo-controlled crossover experiments in dogs and man Belville et al. (1960) reported that its potency is approximately 3 times that of thiopentone. The many reports of its anaesthetic properties have been reviewed by Barton and Dundee (1961) and Robertson (1963). Recovery is more rapid than with thiopentone and there is little "hangover" effect. Most workers, with the exception of Taylor and Stoelting (1960), have noted a low incidence of local irritation, following extravenous injection. In view of these advantages it was felt that this drug might be useful in sleep electroeneephalography, especially with out-patients. This study was undertaken to evaluate it for this purpose by comparing it with thiopentone. METHOD Thirty-two patients, twenty-two male and ten female, who were having several sleep recordings performed during the investigation of epilepsy or suspected organic brain disease, were studied (age range 11 to 57 years, mean 30.4 years). A number were receiving anticonvulsants and a few phenothiazine medication, maintained unchanged throughout. Each subject was examined twice at the same time of day, the interval between the EEGs varying from 1 to 3 weeks. An Ediswan Mark II 8-channel electroencephalograph and a standard bipolar recording technique were used. Sixteen patients had sphenoidal electrodes inserted during both recording periods. Narcosis was induced by intravenous methohexitone on one occasion and thiopentone on the other, the order of administration being random. The subjects were not aware that different drugs were used. Equivalent doses, determined according to body weight (methohexitone 1.76 mg/kg, thiopentone 5.28 mg/kg) were injected at a constant rate (methohexitone 10 mg/15 see, thiopentone 30 mg/15 see). These doses were
chosen empirically as being sufficient to induce the second pattern of barbiturate narcosis in the E E G (Kiersey et al. 1951 ). If this level was not reached, the injection was continued at the same rate until the required E E G pattern appeared. This was necessary in four cases, an identical equivalent dose being given during the second recording. The EEG records were compared by a single observer, who was not aware of the order in which the drugs had been administered. The time taken to recover from the narcosis on each occasion was determined clinically, using a standard procedure. All assessments were performed by the same person, who was unaware of the order in which the drugs had been administered. Each patient was left undisturbed until he opened his eyes. Then Bender's face-hand test was applied (Bender et al. 1951 ; Widdowson et aL 1955). On its correct completion the degree of ataxia was assessed by asking the patient to walk across the room in a straight line, turn round and walk back again. This procedure was repeated at 5 min intervals until the gait was normal. At the same time the patient was examined for nystagmus until its disappearance. In addition, on correct completion of Bender's test, the following questions were put to the subject: "Does your head feel quite clear?", " D o you feel back to normal?". These questions were repeated at 2 min intervals until the answers were in the affirmative. The presence of dysarthria was determined from the verbal responses to these questions. On correct completion of all these tests, the patient was invariably able to leave the department unaided. RESULTS
EEG changes In one subject continuous high voltage, bilaterally synchronous spike and wave complexes obscured the onset of the rhythms induced by both drugs. In the remaining 31 the E E G patterns during methohexitone narcosis were qualitatively similar to those induced by thiopentone. However, the thiopentone records tended to contain a greater quantity of fast activity, while the slow activity was more prominent with methohexitone ( P < 0.004 and 0.001 respectively using Sign test; see Table I). The methohexitone fast activity, although less abundant than that induced by thiopentone, was always present in sufficient amounts to enable its symmetry over the two hemispheres Electroenceph. clin. Neurophysiol., 1967, 23:273-276
274
G. W. FENTON AND L. SCOTTON TABLE I Comparison of drug-induced E E G rhythms. Records of 31 subjects after thiopentone and methohexitone
EEG rhythms
More in thiopentone record
Equal in the two records
More in methohexitone record
18 1
11 3
2 27
Fast Slow
Sign test P < 0.004 P < 0.001
TABLE II Time from onset of injection to appearance of drug-induced activity (Mean values and standard deviations in seconds for 31 subjects) Thiopentone EEG rhythms Fast Slow
Methohexitone
Mean
Standard deviation
Mean
Standard deviation
46.4 75.9
18.7 20.9
41.2 45.5
13.8 30.3
to be assessed and showed similar distribution, frequency and amplitude characteristics. The length of time from the onset of the injection of each drug to the time when the induced fast activity first appeared prominently over both hemispheres was measured and the time taken from the onset of the injection until the slow activity of sleep became the dominant frequency was noted on each occasion (see Table II). The slow activity appeared more rapidly with methohexitone but there was no significant difference between the times of appearance of the fast rhythm induced by the two drugs (Wilcoxon Matched Pairs Signed Ranks Test). Spike or sharp wave discharges appeared during sleep in eleven subjects with both drugs and in one patient during methohexitone narcosis only.
Recovery times The time in minutes from the onset of the injection of
Level of significance P > 0.05 P < 0.01
each drug until the subject completed each test correctly was defined as the recovery time. The score for each test was significantly shorter when methohexitone was used (Wilcoxon test; see Table III).
Complications Involuntary movements occurred during the induction phase in ten subjects (nine with methohexitone and one with thiopentone). Seven of these subjects developed hiccup on one occasion (six with methohexitone and one with thiopentone). In three cases (all having methohexitone) the hiccup was accompanied by mild pronator spasm of the arm being used for the injection. Two other patients developed pronator spasm alone while having methohexitone and a further one clenched and unclenched his fists rhythmically during the early induction phase with methohexitone. None of these phenomena was sufficiently severe to interfere either with the continuation of the injection or
TABLE I I I Mean recovery times in minutes
Test
Bender's test Dysarthria absent Nystagmus absent Ataxia absent "Head clear" "Feels normal"
Thiopentone
NHmber of subjects
Mean
32 31
Methohexitone
Level of
Standard deviation
Mean
Standard deviation
significance
35.6 37.9
18.8 24.2
20.9 21.8
14.0 14.1
P < 0.001 P < 0.001
31
61.3
24.2
29.3
20.5
P < 0.001
31
59.0
27.3
34.3
17.6
P < 0.001
31 31
59.3 59.5
26.1 26.6
37.3 37.3
21.5 21.4
P < 0.001 P < 0.001
Electroenceph. clin. Neurophysiol., 1967, 23:273-276
275
METHOHEXITONE IN SLEEP EEG the recording. Examination of the EEGs revealed movement artefact only at the time of the involuntary movements in seven cases. In the other three, spikes or sharp wave activity appeared sometimes to coincide with the occurrence of the hiccups. At other times, however, the hiccups occurred without ictal phenomena being present, and vice versa. DISCUSSION Our finding of a shorter recovery time following methohexitone agrees with the previous work concerning its use in anaesthesia, where the rate of administration is much quicker. Pampiglione (1965) has recently reported on the use of intravenous injections of small doses of methohexitone in the detection of cortical lesions. He commented on the short-lived effect of the drug. Frank et al. (1966) have found intramuscular methohexitone to be a useful sleep-inducing agent in children and have reported a quicker recovery than with other hypnotic drugs used for the same purpose. This rapid clinical recovery is a distinct advantage when dealing with out-patients. Its activating effect is similar to that of thiopentone. The methohexitone-induced fast activity, although less abundant, is always sufficient in amount to enable the study of the symmetry of its distribution. The action of the two drugs on the cortex, as assessed by the first appearance of fast activity, is approximately equal. However, methohexitone produces narcosis more rapidly. This suggests that its effect on the reticular activating system is more potent than a dose of thiopentone 3 times as great. The higher incidence of spontaneous muscle movement and hiccup with methohexitone is a disadvantage. Wyant and Chang (1959) and Dundee and Moore (1961) have described similar phenomena during the induction phase of methohexitone anaesthesia. Their occurrence has been attributed to the chemical structure of the drug, i.e. the presence of a methyl group in the N-1 position of the barbiturate nucleus. A compound of similar structure (Lilly 22451) was found to have convulsant properties (Dundee et aL 1961). In our cases these phenomena were not associated with any consistent E E G change. SUMMARY The use of methohexitone in sleep electroencephalography was assessed by comparing its effect with that of an equivalent dose of thiopentone in the same subject. 32 patients were examined. Methohexitone produced the classical E E G patterns of barbiturate narcosis, but the induced fast rhythms were slightly less abundant than those seen with thiopentone. However, there were always sufficient to compare the symmetry between the two hemi~ spheres. Slow activity appeared more quickly with methohexitone and was more prominent. Paroxysmal phenomena occurred equally commonly with both drugs. Spontaneous muscle movements and hiccup were more common with methohexitone but were never severe enough to cause a serious problem. The recovery time after methohexitone was substantially shorter than after thiopentone. Methohexitone is a useful drug for inducing sleep, especially in out-patients.
Rf~SUMf~ L'UTILISATION DU MI~THOHEXITONE DANS L'I~LECTROENCEPHALOGRAPHIE DU SOMMEIL L'utilisation du m6thohexitone dans l'61ectroenc6phalographie du sommeil est mesur6e par comparaison de ses effets b_ ceux d'une dose 6quivalente de thiopentone chez le mSme sujet. Trente-deux malades ont 6t6 examin6s. Le m6thohexitone fait apparaitre les patterns EEG classiques de la narcose barbiturique, mais les rythmes rapides induits sont 16g6rements moin abondants que ceux que l'on voit avec le thiopentone. Cependant, ils sont toujours suffisants pour appr6cier la sym6trie entre les deux h6misph6res. L'activit6 lente apparait plus rapidement avee le m6thohexitone et est plus importante. Des ph6nom6nes paroxystiques surviennent 6galement de faqon habituelle avec les deux drogues. Des mouvements musculaires spontan6s ont 6t6 observ6s de faqon plus fr6quente avec le m6thohexitone, ainsi que des hoquets, mais il n'ont jamais 6t6 assez importants pour constituer un probl6me s6rieux. Le temps de r6cup6ration apr6s m6thohexitone s'est montr6 substantiellement plus court qu'apr6s thiopentone. Le m6thohexitone est une drogue utile pour induire le sommeil, sp6cialement chez les malades ambulatoires. We wish to thank Professor Sir Denis Hill for his help and advice with this work and Dr. Miller Mair for advice on the statistics. REFERENCES AUNGLE, P., MITCHELL, W. and PAMPIGLIONE, G. Seconal versus Pentothal in E E G with sphenoidal electrodes. Electroenceph. clin. Neurophysiol., 1954, 6: 344-345. BARRON, D. W. and DUNDEE, J. W. The recently introduced rapidly acting barbiturates; a review and critical appraisal in relation to thiopentone. Brit. J. Anaesth., 1961, 33: 81-91. BELLVILLE, J. W., FENNEL, P. J., MURPHY, T. and HOWLAND, W. S. The relative potencies of methohexital and thiopentone. J. Pharmacol. exp. Ther., 1960, 129: 108-129. BENDER, M. B., FINK, M. and GREEN, M. Patterns in perception on simultaneous tests of face and hand. Arch. Neurol. Psychiat. (Chic.), 1951, 66: 355-362. DUNDEE, J. W. and MOORE, J. Thiopentone and methohexital: a comparison as main anaesthetic agents for a standard operation. Anaesthesia, 1961, 16: 50-60. DUNDEE, J. W., RIDING, J. E., BARRON, D.W. and NICHOLL, R. M. Some factors influencing the induction characteristics of methohexitone anaesthesia. Brit. J. Anaesth., 1961, 33: 296--302. FRANK, G. S., FRASER, R. A. R. and WHITCHER, C. Intramuscular methohexital for rapid induction of short duration sleep in the E E G laboratory: a study of fortyfour hyperkinetic children. Electroenceph. clin. Neurophysiol., 1966, 2I : 76-78. KIERSEY, D. K., BICKFORD, R. G. and FAULCONER, A. Electroencephalographic patterns produced by thiopentone sodium during surgical operations. Description Electroenceph. clin. Neurophysiol., 1967, 23:273-276
276
G. W. FENTON AND L. SCOTTON
and classification. Brit. J. Anaesth., 1951, 23: 141-152. PAMPIGLIONE, G. Very short acting barbiturate (methohexital) in the detection of cortical lesions. Electroenceph. clin. Neurophysiol., 1965,19: 314-316. ROBERTSON, J. D. Intravenous anaesthesia. In C. LANGTON HEWER (Ed.), Recent advances in anaesthesia and analgesia. Churchill, London, 1963: 30-78. TAYLOR, C. and STOELTING,V. K. Methohexital sodium - -
a new ultrashort acting barbiturate. Anesthesiology, 1960, 21 : 29-34. WIDDOWSON, n . R., AQUINO, T. D. and VIRTUE, R.W. Recovery time following Demerol or Pentothal supplementation of nitrous oxide anaesthesia. Anesthesiology, 1955, 16: 747-750. WYANT, G. M. and CHANG, C. A. Sodium methohexital : a clinical study. Canad. Anaesth. Soc. J., 1959, 6: 40-50.
Reference: FENTON, G. W. and SCOTTON,L. The use of methohexitone in sleep electroencephalography. Electroenceph. clin. NeurophysioL, 1967, 23: 273-276.
273
THE USE OF METHOHEXITONE IN SLEEP
ELECTROENCEPHALOGRAPHY GEORGE W . FENTON AND LEILA SCOTTON
Academic Department of Psychiatry, Middlesex Hospital Medical School, London, W. 1 (Great Britain) (Accepted for publication: February 20, 1967)
Oral quinalbarbitone and intravenous thiopentone sodium are the two barbiturates most commonly used to induce sleep in the E E G laboratory (Aungle et al. 1954). Although thiopentone has the advantage that the rate of onset, level and duration of sleep can be more readily controlled, its disadvantages include the risks of perivenous and intra-arterial injections and occasional delayed recovery of consciousness and return of mental faculties (Barron and Dundee 1961). Methohexitone sodium, a recently introduced ultrashort-acting barbiturate appears to lack these defects. In servo-controlled crossover experiments in dogs and man Belville et al. (1960) reported that its potency is approximately 3 times that of thiopentone. The many reports of its anaesthetic properties have been reviewed by Barton and Dundee (1961) and Robertson (1963). Recovery is more rapid than with thiopentone and there is little "hangover" effect. Most workers, with the exception of Taylor and Stoelting (1960), have noted a low incidence of local irritation, following extravenous injection. In view of these advantages it was felt that this drug might be useful in sleep electroeneephalography, especially with out-patients. This study was undertaken to evaluate it for this purpose by comparing it with thiopentone. METHOD Thirty-two patients, twenty-two male and ten female, who were having several sleep recordings performed during the investigation of epilepsy or suspected organic brain disease, were studied (age range 11 to 57 years, mean 30.4 years). A number were receiving anticonvulsants and a few phenothiazine medication, maintained unchanged throughout. Each subject was examined twice at the same time of day, the interval between the EEGs varying from 1 to 3 weeks. An Ediswan Mark II 8-channel electroencephalograph and a standard bipolar recording technique were used. Sixteen patients had sphenoidal electrodes inserted during both recording periods. Narcosis was induced by intravenous methohexitone on one occasion and thiopentone on the other, the order of administration being random. The subjects were not aware that different drugs were used. Equivalent doses, determined according to body weight (methohexitone 1.76 mg/kg, thiopentone 5.28 mg/kg) were injected at a constant rate (methohexitone 10 mg/15 see, thiopentone 30 mg/15 see). These doses were
chosen empirically as being sufficient to induce the second pattern of barbiturate narcosis in the E E G (Kiersey et al. 1951 ). If this level was not reached, the injection was continued at the same rate until the required E E G pattern appeared. This was necessary in four cases, an identical equivalent dose being given during the second recording. The EEG records were compared by a single observer, who was not aware of the order in which the drugs had been administered. The time taken to recover from the narcosis on each occasion was determined clinically, using a standard procedure. All assessments were performed by the same person, who was unaware of the order in which the drugs had been administered. Each patient was left undisturbed until he opened his eyes. Then Bender's face-hand test was applied (Bender et al. 1951 ; Widdowson et aL 1955). On its correct completion the degree of ataxia was assessed by asking the patient to walk across the room in a straight line, turn round and walk back again. This procedure was repeated at 5 min intervals until the gait was normal. At the same time the patient was examined for nystagmus until its disappearance. In addition, on correct completion of Bender's test, the following questions were put to the subject: "Does your head feel quite clear?", " D o you feel back to normal?". These questions were repeated at 2 min intervals until the answers were in the affirmative. The presence of dysarthria was determined from the verbal responses to these questions. On correct completion of all these tests, the patient was invariably able to leave the department unaided. RESULTS
EEG changes In one subject continuous high voltage, bilaterally synchronous spike and wave complexes obscured the onset of the rhythms induced by both drugs. In the remaining 31 the E E G patterns during methohexitone narcosis were qualitatively similar to those induced by thiopentone. However, the thiopentone records tended to contain a greater quantity of fast activity, while the slow activity was more prominent with methohexitone ( P < 0.004 and 0.001 respectively using Sign test; see Table I). The methohexitone fast activity, although less abundant than that induced by thiopentone, was always present in sufficient amounts to enable its symmetry over the two hemispheres Electroenceph. clin. Neurophysiol., 1967, 23:273-276
274
G. W. FENTON AND L. SCOTTON TABLE I Comparison of drug-induced E E G rhythms. Records of 31 subjects after thiopentone and methohexitone
EEG rhythms
More in thiopentone record
Equal in the two records
More in methohexitone record
18 1
11 3
2 27
Fast Slow
Sign test P < 0.004 P < 0.001
TABLE II Time from onset of injection to appearance of drug-induced activity (Mean values and standard deviations in seconds for 31 subjects) Thiopentone EEG rhythms Fast Slow
Methohexitone
Mean
Standard deviation
Mean
Standard deviation
46.4 75.9
18.7 20.9
41.2 45.5
13.8 30.3
to be assessed and showed similar distribution, frequency and amplitude characteristics. The length of time from the onset of the injection of each drug to the time when the induced fast activity first appeared prominently over both hemispheres was measured and the time taken from the onset of the injection until the slow activity of sleep became the dominant frequency was noted on each occasion (see Table II). The slow activity appeared more rapidly with methohexitone but there was no significant difference between the times of appearance of the fast rhythm induced by the two drugs (Wilcoxon Matched Pairs Signed Ranks Test). Spike or sharp wave discharges appeared during sleep in eleven subjects with both drugs and in one patient during methohexitone narcosis only.
Recovery times The time in minutes from the onset of the injection of
Level of significance P > 0.05 P < 0.01
each drug until the subject completed each test correctly was defined as the recovery time. The score for each test was significantly shorter when methohexitone was used (Wilcoxon test; see Table III).
Complications Involuntary movements occurred during the induction phase in ten subjects (nine with methohexitone and one with thiopentone). Seven of these subjects developed hiccup on one occasion (six with methohexitone and one with thiopentone). In three cases (all having methohexitone) the hiccup was accompanied by mild pronator spasm of the arm being used for the injection. Two other patients developed pronator spasm alone while having methohexitone and a further one clenched and unclenched his fists rhythmically during the early induction phase with methohexitone. None of these phenomena was sufficiently severe to interfere either with the continuation of the injection or
TABLE I I I Mean recovery times in minutes
Test
Bender's test Dysarthria absent Nystagmus absent Ataxia absent "Head clear" "Feels normal"
Thiopentone
NHmber of subjects
Mean
32 31
Methohexitone
Level of
Standard deviation
Mean
Standard deviation
significance
35.6 37.9
18.8 24.2
20.9 21.8
14.0 14.1
P < 0.001 P < 0.001
31
61.3
24.2
29.3
20.5
P < 0.001
31
59.0
27.3
34.3
17.6
P < 0.001
31 31
59.3 59.5
26.1 26.6
37.3 37.3
21.5 21.4
P < 0.001 P < 0.001
Electroenceph. clin. Neurophysiol., 1967, 23:273-276
275
METHOHEXITONE IN SLEEP EEG the recording. Examination of the EEGs revealed movement artefact only at the time of the involuntary movements in seven cases. In the other three, spikes or sharp wave activity appeared sometimes to coincide with the occurrence of the hiccups. At other times, however, the hiccups occurred without ictal phenomena being present, and vice versa. DISCUSSION Our finding of a shorter recovery time following methohexitone agrees with the previous work concerning its use in anaesthesia, where the rate of administration is much quicker. Pampiglione (1965) has recently reported on the use of intravenous injections of small doses of methohexitone in the detection of cortical lesions. He commented on the short-lived effect of the drug. Frank et al. (1966) have found intramuscular methohexitone to be a useful sleep-inducing agent in children and have reported a quicker recovery than with other hypnotic drugs used for the same purpose. This rapid clinical recovery is a distinct advantage when dealing with out-patients. Its activating effect is similar to that of thiopentone. The methohexitone-induced fast activity, although less abundant, is always sufficient in amount to enable the study of the symmetry of its distribution. The action of the two drugs on the cortex, as assessed by the first appearance of fast activity, is approximately equal. However, methohexitone produces narcosis more rapidly. This suggests that its effect on the reticular activating system is more potent than a dose of thiopentone 3 times as great. The higher incidence of spontaneous muscle movement and hiccup with methohexitone is a disadvantage. Wyant and Chang (1959) and Dundee and Moore (1961) have described similar phenomena during the induction phase of methohexitone anaesthesia. Their occurrence has been attributed to the chemical structure of the drug, i.e. the presence of a methyl group in the N-1 position of the barbiturate nucleus. A compound of similar structure (Lilly 22451) was found to have convulsant properties (Dundee et aL 1961). In our cases these phenomena were not associated with any consistent E E G change. SUMMARY The use of methohexitone in sleep electroencephalography was assessed by comparing its effect with that of an equivalent dose of thiopentone in the same subject. 32 patients were examined. Methohexitone produced the classical E E G patterns of barbiturate narcosis, but the induced fast rhythms were slightly less abundant than those seen with thiopentone. However, there were always sufficient to compare the symmetry between the two hemi~ spheres. Slow activity appeared more quickly with methohexitone and was more prominent. Paroxysmal phenomena occurred equally commonly with both drugs. Spontaneous muscle movements and hiccup were more common with methohexitone but were never severe enough to cause a serious problem. The recovery time after methohexitone was substantially shorter than after thiopentone. Methohexitone is a useful drug for inducing sleep, especially in out-patients.
Rf~SUMf~ L'UTILISATION DU MI~THOHEXITONE DANS L'I~LECTROENCEPHALOGRAPHIE DU SOMMEIL L'utilisation du m6thohexitone dans l'61ectroenc6phalographie du sommeil est mesur6e par comparaison de ses effets b_ ceux d'une dose 6quivalente de thiopentone chez le mSme sujet. Trente-deux malades ont 6t6 examin6s. Le m6thohexitone fait apparaitre les patterns EEG classiques de la narcose barbiturique, mais les rythmes rapides induits sont 16g6rements moin abondants que ceux que l'on voit avec le thiopentone. Cependant, ils sont toujours suffisants pour appr6cier la sym6trie entre les deux h6misph6res. L'activit6 lente apparait plus rapidement avee le m6thohexitone et est plus importante. Des ph6nom6nes paroxystiques surviennent 6galement de faqon habituelle avec les deux drogues. Des mouvements musculaires spontan6s ont 6t6 observ6s de faqon plus fr6quente avec le m6thohexitone, ainsi que des hoquets, mais il n'ont jamais 6t6 assez importants pour constituer un probl6me s6rieux. Le temps de r6cup6ration apr6s m6thohexitone s'est montr6 substantiellement plus court qu'apr6s thiopentone. Le m6thohexitone est une drogue utile pour induire le sommeil, sp6cialement chez les malades ambulatoires. We wish to thank Professor Sir Denis Hill for his help and advice with this work and Dr. Miller Mair for advice on the statistics. REFERENCES AUNGLE, P., MITCHELL, W. and PAMPIGLIONE, G. Seconal versus Pentothal in E E G with sphenoidal electrodes. Electroenceph. clin. Neurophysiol., 1954, 6: 344-345. BARRON, D. W. and DUNDEE, J. W. The recently introduced rapidly acting barbiturates; a review and critical appraisal in relation to thiopentone. Brit. J. Anaesth., 1961, 33: 81-91. BELLVILLE, J. W., FENNEL, P. J., MURPHY, T. and HOWLAND, W. S. The relative potencies of methohexital and thiopentone. J. Pharmacol. exp. Ther., 1960, 129: 108-129. BENDER, M. B., FINK, M. and GREEN, M. Patterns in perception on simultaneous tests of face and hand. Arch. Neurol. Psychiat. (Chic.), 1951, 66: 355-362. DUNDEE, J. W. and MOORE, J. Thiopentone and methohexital: a comparison as main anaesthetic agents for a standard operation. Anaesthesia, 1961, 16: 50-60. DUNDEE, J. W., RIDING, J. E., BARRON, D.W. and NICHOLL, R. M. Some factors influencing the induction characteristics of methohexitone anaesthesia. Brit. J. Anaesth., 1961, 33: 296--302. FRANK, G. S., FRASER, R. A. R. and WHITCHER, C. Intramuscular methohexital for rapid induction of short duration sleep in the E E G laboratory: a study of fortyfour hyperkinetic children. Electroenceph. clin. Neurophysiol., 1966, 2I : 76-78. KIERSEY, D. K., BICKFORD, R. G. and FAULCONER, A. Electroencephalographic patterns produced by thiopentone sodium during surgical operations. Description Electroenceph. clin. Neurophysiol., 1967, 23:273-276
276
G. W. FENTON AND L. SCOTTON
and classification. Brit. J. Anaesth., 1951, 23: 141-152. PAMPIGLIONE, G. Very short acting barbiturate (methohexital) in the detection of cortical lesions. Electroenceph. clin. Neurophysiol., 1965,19: 314-316. ROBERTSON, J. D. Intravenous anaesthesia. In C. LANGTON HEWER (Ed.), Recent advances in anaesthesia and analgesia. Churchill, London, 1963: 30-78. TAYLOR, C. and STOELTING,V. K. Methohexital sodium - -
a new ultrashort acting barbiturate. Anesthesiology, 1960, 21 : 29-34. WIDDOWSON, n . R., AQUINO, T. D. and VIRTUE, R.W. Recovery time following Demerol or Pentothal supplementation of nitrous oxide anaesthesia. Anesthesiology, 1955, 16: 747-750. WYANT, G. M. and CHANG, C. A. Sodium methohexital : a clinical study. Canad. Anaesth. Soc. J., 1959, 6: 40-50.
Reference: FENTON, G. W. and SCOTTON,L. The use of methohexitone in sleep electroencephalography. Electroenceph. clin. NeurophysioL, 1967, 23: 273-276.