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ELECTROMYOGRAPHIC RESPONSES TO SMALL DOSES OF SUXAMETHONIUM IN CHILDREN AFTER BURNS
Br.J. Anaesth. (1987), 59, 1017-1021
ELECTROMYOGRAPHIC RESPONSES TO SMALL DOSES OF SUXAMETHONIUM IN CHILDREN AFTER BURNS T. C. K. BROWN AND B. BELL
Since the hazard of hyperkalaemia appeared to be related to the extent of the burn, and seemed to be greatest between 2 and 6 weeks after the burn, we set out to do a study (using suxamethonium 0.2 mg kg"1) to assess the influences of the extent of the burn, and time following the thermal injury. Unexpectedly, one of the first patients became apnoeic following this dose. Thus T. C. K. BROWN, MJ>., F.F.A.R.A.CS.; BRENDA BELL, B_APP.SC.,
Department of Anaesthesia, Royal Children's Hospital, Flemington Road, Parkville, Victoria 3052, Australia. Accepted for Publication: March 2, 1987. Correspondence to T. B.
SUMMARY Integrated electromyographic studies in burned patients, and in normal controls, during the administration of small doses of suxamethonium (0.1 or 0.2 mg kg'1) have shown that the level of paralysis and the duration of paralysis are significantly increased in burn patients and that the effect is greater with larger burns. Repeated studies on patients using these small doses have shown that patients with burns pass through a phase of extreme sensitivity to the effects of suxamethonium, usually sometime between 4 and 12 days after the burn.
we undertook this electromyographic study of responses of normal and burned patients to small doses of suxamethonium. PATIENTS AND METHODS
Following the induction of anaesthesia with thiopentone two control groups (50 children each) were given suxamethonium, either 0.1 or 0.2 mg kg"1 diluted to 1 mg ml"1 in sterile water. The selection of burned patients was restricted to those who had an uninjured hand and forearm so that the EMG electrodes could be attached. Thirty-eight burned patients received suxamethonium 0.1 or 0.2 mg kg"1 on 59 occasions. Eleven patients who had repeated anaesthetics were studied on multiple occasions. In these patients the maximum response was used for comparison with the normal controls. The integrated electromyograph (IEMG) was developed and constructed at the Department of Electrical Engineering at Monash University (Lam, Cass and Ng, 1981). Two stimulating electrodes were placed over the median nerve at the wrist, the recording electrodes over the opponens pollicis muscle and a reference electrode
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
Cardiac arrest has occurred following the administration of suxamethonium to burned patients (Fleming et al., 1960), and recognition of this hazard has led to the avoidance of the use of suxamethonium in such patients. Bush (1964) postulated a number of possible mechanisms and, although it was suspected that hyperkalaemia might be the cause, this was not confirmed until Tolmie, Joyce and Mitchell (1967) reported repeated cardiac arrests associated with acute increases in serum potassium concentation in a badly burned soldier in Vietnam. Keneally and Bush (1974) reported a mean maximum change of 0.13 mmol litre"1 after suxamethonium 1.5mgkg~l in children—the only statistically significant change was in the group aged 5 yr and younger, in which there was a mean maximum increase of 0.23 mmol litre"1. Studies reported from our Burn Unit in 1970 showed that the increase in serum potassium concentration appeared to be related to the extent of the burn: an increase of 4.9 mmol litre"1 occurred on the 25th day post-burn in a child with 30 % burns with only a very transient decrease in cardiac output as assessed by the intensity of heart sounds, while a boy with 10% burns showed an increase in potassium concentration of only 1.7 mmol litre"1 (Brown and Bishop, 1970).
1018
BRITISH JOURNAL OF ANAESTHESIA
was a similar statistically significant difference between patients with burns receiving suxamethonium 0.2 mg kg"1 compared with controls. 100 |~T The results are summarized in table I and figure 2. The maximum responses were used for patients studied on multiple occasions. Eleven patients were studied on two or more occasions. Only one of the eight patients given 0.2 mg kg"1 had a maximum depression of muscle activity of less than 93%. Two patients given 3 O.lmgkg" 1 had 83% and 93% maximum 5-< depression of muscle activity, respectively, while the third, in whom the decrease was 58 %, was not studied until 16 days after the burn—which is later than the time of maximum depression seen in the other patients. This occurred between 4 and 12 Time days (mean 8 days). FIG. 1. IEMG pattern showing how the measurements were Figures 3, 4 and 5 are illustrative of patients made from the recording. 1 = Maximum depression in muscle activity (IEMG response). 2 = Time from injection to studied on multiple occasions. Figure 3 illustrates maximum IEMG depression. 3 = Time to 50% recovery. the depolarization response without any decrease 4 = Time from 50% of total decrease in activity until recovery in muscle activity following suxamethonium to the same level. 0.1 mg kg"1 in the early post-burn period. This was placed on the forearm. A supramaximal phenomenon was also seen with this dose in some stimulus at 1 Hz for 0.1 ms was used to stimulate of the controls. Four days later the patient had a the median nerve. The depression of the IEMG marked response to suxamethonium which leswas recorded on a chart recorder. Measurements sened on subsequent occasions. Figure 4 shows the marked responses on all were made as illustrated in figure 1. burns The non parametric Mann—Whitney U test was occasions in an older patient with 10% 1 receiving suxamethonium 0.2 mg kg" . Figure 5 used for statistical analysis. shows the marked response to 0.2 mg kg"1 on the first occasion, with a reduced response of shorter RESULTS duration on the second occasion 16 days after the Thirty-eight patients were studied on 59 occa- burn. sions. Suxamethonium O.lmgkg" 1 was given In general, the greater the degree of paralysis on 19 occasions (11 patients) and there was a the longer was the duration of effect measured to statistically significant increase in paralysis (de- the time of maximum depression, to 50 % recovery pression of muscle activity) and duration of and between the midpoints of the downslope and action compared with controls (P < 0.001). There upslope of the IEMG traces (fig. 1). Injection
% max. depression in muscle activity
Time to max. depression (min)
Time to 50% recovery (min)
Dose (mgkg-)
n
Control Burns 20 + %
0.1 0.1
50 6
0.22 ±0.21 5.3±1.6 54.1 ±18.7*** 0.79±0.18***
Control Bums < 10%
0.2 0.2
50 10
56.6±22.2 62.0 ±32.2
0.63 ±0.19 0.97 ±0.30***
1.23 ±0.39 2.19 ±1.29***
Group
0.43 ±0.15 1.67 ±0.90
Bums 11-19%
0.2
7
78.4 ±23.8*
0.94 ±0.37**
3.05 ±1.90**
Bums 20 + %
0.2
10
76.4 ±24.2**
1.25 ±0.46***
3.61 ±1.70***
Time 50% dep. to 50% recovery (min)
0J7±0.11 1.36 ±0.67 0.99 ±0.34 1.85 ±1.23*** 2.72±1.91* 3.20 ±1.59***
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
I. IEMG responses to suxamethonium in burns. Statistical significance compared with controls: *P < 0.01; **P < 0.005; ***P < 0.001
SUXAMETHONIUM IN BURNS
1019
CONTROL 20*%
2
3
0
1 2
3
4
0
1 2
3
4
8
6
0
1
2
3
4
5
6
Time (mm) FIG. 2. The mean IEMG recordings for control subjects and patients with burns after suxamethonium 0.1 mg kg"1 (dotted lines) and 0.2 mg kg"1 (solid lines). SD of maximum depression and time to 50% recovery shown.
100
4 days
4
FIG. 3. Degree and duration of paralysis in a 32-kg 6-yr-old (28% of bums) following suxamethonium O.lmgkg" 1 . It demonstrates the increase in sensitivity at 10 days after the bum.
DISCUSSION
Using small doses of suxamethonium, significant differences in response and duration of action were demonstrated in patients with burns compared with normal children. It was found also that patients with burns go through a phase of markedly increased sensitivity to suxamethonium some time between the 4th and 12th days after the
5 6 Time (mm)
6 days
9
10
FIG. 4. Marked response in a 55-kg 15-yr-old with only 10% burns on three occasions between 4 and 11 days after the burn—the period when sensitivity to suxamethonium is maximal.
burn. At this time the degree of paralysis following 0.2 mg kg"1 may cause apnoea and be sufficient to permit intubation of the trachea. Viby-Mogensen and co-workers (1975a) demonstrated a decrease in plasma cholinesterase activity following thermal injury which correlated significantly with the extent of the burn. The decrease to minimum values occurred most rapidly in patients with a burn index greater than 30%. Most of this decrease occurred during the first 2 days after the injury. The duration of the depression in cholinesterase activity was some-
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
1
1020
BRITISH JOURNAL OF ANAESTHESIA /16days
K^,
5days
2- 802 o
" 60
I
40 20
5
6
9
10
Time (mm)
times prolonged and in some patients normal values were not regained for some weeks after full recovery. Although the decrease in plasma cholinesterase concentration could result in an exaggerated response to suxamethonium, the fact that the maximum depression of IEMG activity occurs later suggests that it is not the only factor increasing the sensitivity to suxamethonium in burned patients. Viby-Mogensen and co-workers (1975b) demonstrated a significant correlation between the maximum increase in serum potassium concentration and the extent of the burn when suxamethonium was given after the 14th day. They also noted that major increases before that time occurred only with very extensive burns. Our experience suggests that the greatest increases in serum potassium concentration occur during the 3rd and 4th weeks after the burn (Brown and Bishop, 1970). This is later than the time at which the maximum responses occurred in this study. In two of our patients who showed a markedly greater depression of muscle activity, blood samples taken each minute from 0 to 5 min after suxamethonium, showed no change in serum potassium concentration. In another child, with 30% surface area bums whose potassium concentrations were measured on nine occasions after suxamethonium 0.1 mg kg"1, plasma potassium concentration decreased until 15 days after the burn, when an increase of 0.3 mmol litre"1 occurred. The maximum increase in plasma potassium concentration (0.4 mmol litre"1) occurred on the 26th day after the burn. The maximum depression of muscle activity (IEMG) occurred on day 12. It appears that the exaggerated neuromuscular blocking
ACKNOWLEDGEMENTS The authors wish to thank Dr F. McK. Whan for his help during the early part of this study, Dr N. M. Cass for his comments during the preparation of the paper, and Dr F. Shann for help with the statistics. We also thank Miss F. McGregor and Miss C. Taylor for typing the manuscripts, the Educational Resources Centre, Royal Children's Hospital for preparing the illustrations, and Mr J. R. Solomon and Mr E. J. Keogh of the Burns Unit for their co-operation during the study.
REFERENCES Brown, T. C. K., and Bishop, A. A. (1970). Anaesthesia for children with burns. Proceedings III AACA, Canberra, p. 323. Fisk, G. C. (1979). Anaesthesia for Children, 1st Edn, p. 240. Oxford: Blackwells. Bush, G. H. (1964). The use of muscle relaxants in burned children. Anaesthesia, 19, 231. Fleming, W. B., Hueston, J. T., Stubbe, J. L., and Villiers, J. D. (1960). Two episodes of cardiac arrest in one week.
Br.Med.J., 1, 157. Keneally, J. P., and Bush, G. H. (1974). Changes in serum potassium after suxamethonium in children. Anaesth. Intern. Care, 2, 147. Lam, H. S., Cass, N. M., and Ng, K. C. (1981). Electromyographic monitoring of neuromuscular block. Br. J. Anaesth., 53, 1351.
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
FIG. 5. A child with 20% burns showing a marked difference in response between 5 and 16 days after the bum following suxamethonium 0.2 mg kg"1.
effects are not related to the hyperkalaemic response to suxamethonium. We have shown that, after burns, children exhibit an increased degree and duration of paralysis following small doses of suxamethonium. They pass through a phase of exquisite sensitivity which occurs sometime between the 4th and 12th days after the burn, when they will become paralysed (and the trachea can be intubated) with doses as small as 0.2 mg kg"1. Although intubation can be performed with much reduced doses of suxamethonium—which will not cause dangerous increases in serum potassium concentration—it is not usually necessary to use this neuromuscular blocking drug, and it is generally advisable not to use suxamethonium in patients with large burns. Non-depolarizing drugs can be used, but larger doses than normal, particularly of tubocurarine, may be required (Brown and Fisk, 1979; Martyn et al., 1980). The maximum changes in plasma cholinesterase activity, sensitivity to suxamethonium and potassium concentration after suxamethonium do not occur at the same times after the burn. Although the first two changes may have some interrelation, neither is related to the increase in the release of potassium.
SUXAMETHONIUM IN BURNS Martyn, J. A. J., Szygelbein, S. K., Ali, H. H., Maneo, R. S., and Savarese, J. J. (1980). Increased d-tubocurarine requiranents following major thermal injury. Arusthesiology, 52, 352. Tolmie, J. D., Joyce, T. H., and Mitchell, G. D. (1967). Succinylcholine danger in the burned patient. Anesthesiology, 18, 467.
1021 Viby-Mogensen, J., Hand, H. K., Hansen, E., Sorensen, B., and Graae, J. (1975a). Serum cholinesterase activity in burned patients. 1: Biochemical findings. Acta Anaeitheiiol. Scand., 19, 159. Graae, J.( 1975b). Serum cholinesterase activity in burned patients. II: Anaesthesia, suxamethonium and hyperkalaemia. Acta Aruuslhtsiol. Scand., 19, 169.
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
ELECTROMYOGRAPHIC RESPONSES TO SMALL DOSES OF SUXAMETHONIUM IN CHILDREN AFTER BURNS T. C. K. BROWN AND B. BELL
Since the hazard of hyperkalaemia appeared to be related to the extent of the burn, and seemed to be greatest between 2 and 6 weeks after the burn, we set out to do a study (using suxamethonium 0.2 mg kg"1) to assess the influences of the extent of the burn, and time following the thermal injury. Unexpectedly, one of the first patients became apnoeic following this dose. Thus T. C. K. BROWN, MJ>., F.F.A.R.A.CS.; BRENDA BELL, B_APP.SC.,
Department of Anaesthesia, Royal Children's Hospital, Flemington Road, Parkville, Victoria 3052, Australia. Accepted for Publication: March 2, 1987. Correspondence to T. B.
SUMMARY Integrated electromyographic studies in burned patients, and in normal controls, during the administration of small doses of suxamethonium (0.1 or 0.2 mg kg'1) have shown that the level of paralysis and the duration of paralysis are significantly increased in burn patients and that the effect is greater with larger burns. Repeated studies on patients using these small doses have shown that patients with burns pass through a phase of extreme sensitivity to the effects of suxamethonium, usually sometime between 4 and 12 days after the burn.
we undertook this electromyographic study of responses of normal and burned patients to small doses of suxamethonium. PATIENTS AND METHODS
Following the induction of anaesthesia with thiopentone two control groups (50 children each) were given suxamethonium, either 0.1 or 0.2 mg kg"1 diluted to 1 mg ml"1 in sterile water. The selection of burned patients was restricted to those who had an uninjured hand and forearm so that the EMG electrodes could be attached. Thirty-eight burned patients received suxamethonium 0.1 or 0.2 mg kg"1 on 59 occasions. Eleven patients who had repeated anaesthetics were studied on multiple occasions. In these patients the maximum response was used for comparison with the normal controls. The integrated electromyograph (IEMG) was developed and constructed at the Department of Electrical Engineering at Monash University (Lam, Cass and Ng, 1981). Two stimulating electrodes were placed over the median nerve at the wrist, the recording electrodes over the opponens pollicis muscle and a reference electrode
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
Cardiac arrest has occurred following the administration of suxamethonium to burned patients (Fleming et al., 1960), and recognition of this hazard has led to the avoidance of the use of suxamethonium in such patients. Bush (1964) postulated a number of possible mechanisms and, although it was suspected that hyperkalaemia might be the cause, this was not confirmed until Tolmie, Joyce and Mitchell (1967) reported repeated cardiac arrests associated with acute increases in serum potassium concentation in a badly burned soldier in Vietnam. Keneally and Bush (1974) reported a mean maximum change of 0.13 mmol litre"1 after suxamethonium 1.5mgkg~l in children—the only statistically significant change was in the group aged 5 yr and younger, in which there was a mean maximum increase of 0.23 mmol litre"1. Studies reported from our Burn Unit in 1970 showed that the increase in serum potassium concentration appeared to be related to the extent of the burn: an increase of 4.9 mmol litre"1 occurred on the 25th day post-burn in a child with 30 % burns with only a very transient decrease in cardiac output as assessed by the intensity of heart sounds, while a boy with 10% burns showed an increase in potassium concentration of only 1.7 mmol litre"1 (Brown and Bishop, 1970).
1018
BRITISH JOURNAL OF ANAESTHESIA
was a similar statistically significant difference between patients with burns receiving suxamethonium 0.2 mg kg"1 compared with controls. 100 |~T The results are summarized in table I and figure 2. The maximum responses were used for patients studied on multiple occasions. Eleven patients were studied on two or more occasions. Only one of the eight patients given 0.2 mg kg"1 had a maximum depression of muscle activity of less than 93%. Two patients given 3 O.lmgkg" 1 had 83% and 93% maximum 5-< depression of muscle activity, respectively, while the third, in whom the decrease was 58 %, was not studied until 16 days after the burn—which is later than the time of maximum depression seen in the other patients. This occurred between 4 and 12 Time days (mean 8 days). FIG. 1. IEMG pattern showing how the measurements were Figures 3, 4 and 5 are illustrative of patients made from the recording. 1 = Maximum depression in muscle activity (IEMG response). 2 = Time from injection to studied on multiple occasions. Figure 3 illustrates maximum IEMG depression. 3 = Time to 50% recovery. the depolarization response without any decrease 4 = Time from 50% of total decrease in activity until recovery in muscle activity following suxamethonium to the same level. 0.1 mg kg"1 in the early post-burn period. This was placed on the forearm. A supramaximal phenomenon was also seen with this dose in some stimulus at 1 Hz for 0.1 ms was used to stimulate of the controls. Four days later the patient had a the median nerve. The depression of the IEMG marked response to suxamethonium which leswas recorded on a chart recorder. Measurements sened on subsequent occasions. Figure 4 shows the marked responses on all were made as illustrated in figure 1. burns The non parametric Mann—Whitney U test was occasions in an older patient with 10% 1 receiving suxamethonium 0.2 mg kg" . Figure 5 used for statistical analysis. shows the marked response to 0.2 mg kg"1 on the first occasion, with a reduced response of shorter RESULTS duration on the second occasion 16 days after the Thirty-eight patients were studied on 59 occa- burn. sions. Suxamethonium O.lmgkg" 1 was given In general, the greater the degree of paralysis on 19 occasions (11 patients) and there was a the longer was the duration of effect measured to statistically significant increase in paralysis (de- the time of maximum depression, to 50 % recovery pression of muscle activity) and duration of and between the midpoints of the downslope and action compared with controls (P < 0.001). There upslope of the IEMG traces (fig. 1). Injection
% max. depression in muscle activity
Time to max. depression (min)
Time to 50% recovery (min)
Dose (mgkg-)
n
Control Burns 20 + %
0.1 0.1
50 6
0.22 ±0.21 5.3±1.6 54.1 ±18.7*** 0.79±0.18***
Control Bums < 10%
0.2 0.2
50 10
56.6±22.2 62.0 ±32.2
0.63 ±0.19 0.97 ±0.30***
1.23 ±0.39 2.19 ±1.29***
Group
0.43 ±0.15 1.67 ±0.90
Bums 11-19%
0.2
7
78.4 ±23.8*
0.94 ±0.37**
3.05 ±1.90**
Bums 20 + %
0.2
10
76.4 ±24.2**
1.25 ±0.46***
3.61 ±1.70***
Time 50% dep. to 50% recovery (min)
0J7±0.11 1.36 ±0.67 0.99 ±0.34 1.85 ±1.23*** 2.72±1.91* 3.20 ±1.59***
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
I. IEMG responses to suxamethonium in burns. Statistical significance compared with controls: *P < 0.01; **P < 0.005; ***P < 0.001
SUXAMETHONIUM IN BURNS
1019
CONTROL 20*%
2
3
0
1 2
3
4
0
1 2
3
4
8
6
0
1
2
3
4
5
6
Time (mm) FIG. 2. The mean IEMG recordings for control subjects and patients with burns after suxamethonium 0.1 mg kg"1 (dotted lines) and 0.2 mg kg"1 (solid lines). SD of maximum depression and time to 50% recovery shown.
100
4 days
4
FIG. 3. Degree and duration of paralysis in a 32-kg 6-yr-old (28% of bums) following suxamethonium O.lmgkg" 1 . It demonstrates the increase in sensitivity at 10 days after the bum.
DISCUSSION
Using small doses of suxamethonium, significant differences in response and duration of action were demonstrated in patients with burns compared with normal children. It was found also that patients with burns go through a phase of markedly increased sensitivity to suxamethonium some time between the 4th and 12th days after the
5 6 Time (mm)
6 days
9
10
FIG. 4. Marked response in a 55-kg 15-yr-old with only 10% burns on three occasions between 4 and 11 days after the burn—the period when sensitivity to suxamethonium is maximal.
burn. At this time the degree of paralysis following 0.2 mg kg"1 may cause apnoea and be sufficient to permit intubation of the trachea. Viby-Mogensen and co-workers (1975a) demonstrated a decrease in plasma cholinesterase activity following thermal injury which correlated significantly with the extent of the burn. The decrease to minimum values occurred most rapidly in patients with a burn index greater than 30%. Most of this decrease occurred during the first 2 days after the injury. The duration of the depression in cholinesterase activity was some-
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
1
1020
BRITISH JOURNAL OF ANAESTHESIA /16days
K^,
5days
2- 802 o
" 60
I
40 20
5
6
9
10
Time (mm)
times prolonged and in some patients normal values were not regained for some weeks after full recovery. Although the decrease in plasma cholinesterase concentration could result in an exaggerated response to suxamethonium, the fact that the maximum depression of IEMG activity occurs later suggests that it is not the only factor increasing the sensitivity to suxamethonium in burned patients. Viby-Mogensen and co-workers (1975b) demonstrated a significant correlation between the maximum increase in serum potassium concentration and the extent of the burn when suxamethonium was given after the 14th day. They also noted that major increases before that time occurred only with very extensive burns. Our experience suggests that the greatest increases in serum potassium concentration occur during the 3rd and 4th weeks after the burn (Brown and Bishop, 1970). This is later than the time at which the maximum responses occurred in this study. In two of our patients who showed a markedly greater depression of muscle activity, blood samples taken each minute from 0 to 5 min after suxamethonium, showed no change in serum potassium concentration. In another child, with 30% surface area bums whose potassium concentrations were measured on nine occasions after suxamethonium 0.1 mg kg"1, plasma potassium concentration decreased until 15 days after the burn, when an increase of 0.3 mmol litre"1 occurred. The maximum increase in plasma potassium concentration (0.4 mmol litre"1) occurred on the 26th day after the burn. The maximum depression of muscle activity (IEMG) occurred on day 12. It appears that the exaggerated neuromuscular blocking
ACKNOWLEDGEMENTS The authors wish to thank Dr F. McK. Whan for his help during the early part of this study, Dr N. M. Cass for his comments during the preparation of the paper, and Dr F. Shann for help with the statistics. We also thank Miss F. McGregor and Miss C. Taylor for typing the manuscripts, the Educational Resources Centre, Royal Children's Hospital for preparing the illustrations, and Mr J. R. Solomon and Mr E. J. Keogh of the Burns Unit for their co-operation during the study.
REFERENCES Brown, T. C. K., and Bishop, A. A. (1970). Anaesthesia for children with burns. Proceedings III AACA, Canberra, p. 323. Fisk, G. C. (1979). Anaesthesia for Children, 1st Edn, p. 240. Oxford: Blackwells. Bush, G. H. (1964). The use of muscle relaxants in burned children. Anaesthesia, 19, 231. Fleming, W. B., Hueston, J. T., Stubbe, J. L., and Villiers, J. D. (1960). Two episodes of cardiac arrest in one week.
Br.Med.J., 1, 157. Keneally, J. P., and Bush, G. H. (1974). Changes in serum potassium after suxamethonium in children. Anaesth. Intern. Care, 2, 147. Lam, H. S., Cass, N. M., and Ng, K. C. (1981). Electromyographic monitoring of neuromuscular block. Br. J. Anaesth., 53, 1351.
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015
FIG. 5. A child with 20% burns showing a marked difference in response between 5 and 16 days after the bum following suxamethonium 0.2 mg kg"1.
effects are not related to the hyperkalaemic response to suxamethonium. We have shown that, after burns, children exhibit an increased degree and duration of paralysis following small doses of suxamethonium. They pass through a phase of exquisite sensitivity which occurs sometime between the 4th and 12th days after the burn, when they will become paralysed (and the trachea can be intubated) with doses as small as 0.2 mg kg"1. Although intubation can be performed with much reduced doses of suxamethonium—which will not cause dangerous increases in serum potassium concentration—it is not usually necessary to use this neuromuscular blocking drug, and it is generally advisable not to use suxamethonium in patients with large burns. Non-depolarizing drugs can be used, but larger doses than normal, particularly of tubocurarine, may be required (Brown and Fisk, 1979; Martyn et al., 1980). The maximum changes in plasma cholinesterase activity, sensitivity to suxamethonium and potassium concentration after suxamethonium do not occur at the same times after the burn. Although the first two changes may have some interrelation, neither is related to the increase in the release of potassium.
SUXAMETHONIUM IN BURNS Martyn, J. A. J., Szygelbein, S. K., Ali, H. H., Maneo, R. S., and Savarese, J. J. (1980). Increased d-tubocurarine requiranents following major thermal injury. Arusthesiology, 52, 352. Tolmie, J. D., Joyce, T. H., and Mitchell, G. D. (1967). Succinylcholine danger in the burned patient. Anesthesiology, 18, 467.
1021 Viby-Mogensen, J., Hand, H. K., Hansen, E., Sorensen, B., and Graae, J. (1975a). Serum cholinesterase activity in burned patients. 1: Biochemical findings. Acta Anaeitheiiol. Scand., 19, 159. Graae, J.( 1975b). Serum cholinesterase activity in burned patients. II: Anaesthesia, suxamethonium and hyperkalaemia. Acta Aruuslhtsiol. Scand., 19, 169.
Downloaded from http://bja.oxfordjournals.org/ at University of Manitoba on June 15, 2015