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An analysis of burn mortality: a report from a Spanish regional burn centre
Bums
(1991)
27,
(3), 201-204
201
printed in Great Britain
An analysis of burn mortality: a report from a Spanish regional burn centre J. Benito-Ruiz, A. Navarro-Monzonis,
P. Baena-Montilla and V. Mirabet-Ippolito
Bum Centre ‘La Fe’ Hospital, Vajencia, Spain
This paper reports an analysis of tk mortality rates and relatedfactors in our Burn Centre, based on 710 patients Ire&d belween 1985 and 1988. The average age of tk patients was 23.8 years and the average bum size was 14 per cent of the body surface area. Burning injury affected mainly men (66 per cent), and their mortality rate WIES higher than that women. The overall mortality rate was 6.6 per cent, tk average age of the fatally injured patients being 54 years. We conjirm that mortality in burned patients is closely related to: age (51 per cent of the patients were over 60 years of age): bum size (68 per cent of tk patients had bums coveringmore than 30 per cent TBS); burn depth (57.4 per cent hadfull skin thickness burns); inhalation injuy (present in 66 per cent of the fatally injured); and associated risk factors. The main cause of the burning injury was flames, chiefly from domestic accidents. The average survival time for tk fatally injured patients was 10 days. Finally, our experted mortality followed a linear regression model, tk LA 50for patients with only fill skin thickness burns was 50 per cent.
200 180 160 140 120
of
100 80 60 40 20 n ==I0
II-20
Figure I. Distribution
21-30
31-40 41-50 51-60 Age h)
by age and sex.
61-70
?? , Males;
71-80 N,
281
females.
50 40 ;; ax j; E o?
Introduction It is well known fhat mortality from buming injury has decreased over the last few years. This seems to be due to a better understanding of the physiopathology of the burned patients and improvements in their management (Davies, 1982; Clark and Fromm, 1987; Muir et al., 1987). Age and bum severity have been the main factors related to the outcome (Bull, 1971; Muir et al., x987), but multivariate analyses have proved the role of other factors such as lung injury (Thompson et al., 1986; Shirani et al., 1987), bum depth (Zawacki et al., 1979; Clark and Fromm, 1987) and even associated diseases. This paper investigates the mortality of the patients admitted to and treated in our bum centre during a 4 year period.
Materials and methods The charts of 710 patients admitted to our hospital over the 4 years from December 1984 to December 1988 were reviewed. During this period we treated 9794 burned patients in our casualty department, our admission rate was thus 7.25 per cent. 0 1991 Butterworth-Heinemann 0305-4179/91/030201-04
Ltd
30
_.____~_______-.--~.-.--..-_-~
20 IO 0 ,=I0
II-20
21-30
31-40
41-50 51-60 Age (yr)
61-70
Figure 2. Average of burn size by sex and age. females.
71-80
~81
?? , Males; &S,
The average age of the patients was 23.84 f 24.06 years, 469 of the 710 patients (66 per cent) were male, 308 patients (43.4 per cent) were children under 10 years old, and 55 (7.7 per cent) were older than 70 years. The average extent of the bum was 14 f 17 per cent; minor injuries (< 10 per cent TBS) were very common (62 per cent). The distribution of the admitted victims according to age and sex is shown in Figure I, the average bum size by age and sex is shown in Figure 2. Data were statistically analysed by two commercial programmes (MICROSTATTM and EPISTATTM). A multifactorial linear regression model was used to determine the expected mortality, the variable predictors being: Age, bum extent, inhalation injury and associated risk factors, for patients with partial skin thickness bums. 0 The same as above but for patients who sustained only full skin thickness bums.
0
202
Bums (1991) Vol. 17/No. 3 Table I. Associated risk factors at admission
72
8o
$
70
v)
60
g
50
2
40
8
30 20
Disease
IO 0 C!O
II-20 21-30 31-4041-50 51-60 61-70 71-80 81-90~90 Age (yr)
Figure 3. Mortality by sex and age. ?? , Females; &,
Statistical significances test for 2 x 2 contingency
were obtained tables.
males.
by Fisher’s exact
Results The overall mortality rate in our centre over this 4-year period was 6.6 per cent (47 cases). The average age of these fatalities was 54 years, with 24 of the 47 patients (51 per cent) being older than 60 years. The mortality in this group was 28.2 per cent. There was a statistically significant difference between the mortality rates of the younger and the older patients (PC 0.000001). The mortaIity rate was higher in the males than in the females, with a ratio of 2.36 : 1. Figure 3 shows the number of deaths in both groups, related to age. A fatal outcome is slightly greater in females under 10 years old. In elderly patients (> 70 years) the mortality rate is significantly higher in the men (PC 0.05) (56 per cent vs 15 per cent). As expected we have confirmed the close relationship between mortality rate and age and burn size. In our bum centre we distinguish the following causes of burning injury: scalds, flames, gunpowder, electricity, hot contact, ‘bonfire’, chemicals and others. Bums by bonfire’ are defined as those mainly produced by direct contact with burning coal and with small lighters, candles, and burners of cookers and heaters, depending on the personal view of the physician on duty. We acknowledge it is a badly defined entity, with a potential mix of flames and hot contact, but it is recorded on our charts in that way. Flames caused 76.6 per cent of the deaths, followed by gunpowder (6.4 per cent), ‘bonfire’ (6.4 per cent), scalds (4.2 per cent), electricity (2.1 per cent) and hot contact (2.1 per cent). The high rate of mortality due to flames is associated with more severe bums with respect to extent, depth (frequently deep dermal and full skin thickness bums) and the possibility of pulmonary injury by smoke or toxic-gas inhalation. Gunpowder is involved in work-related accidents, consisting of explosions, occurring while handling, or manufacturing rockets (the fireworks industry is a developed sector in our area and is a means of earning a living for thousands of people). With respect to the location of the accident, 59 per cent of the patients were injured at home, IS per cent while working, 10.6 per cent were involved in traffic accidents, 6.4 per cent occurred in the street, 4.2 per cent were attempted suicides, 2 per cent were due to acts of aggression and 2.8 per cent were unknown. The average length of survival for fatal injuries was 10.7 days. The average age of the patients who died in the first 48 h (resuscitation period) was 54 years and the mean
Diabetes mellitus Lung condition Traumatism Asthma Chronic respiratory disease Neurological condition Epilepsy Vascular Senile dementia Parkinsonism Mental retardation Cardiovascular Gastrointestinal Polytraumatism Chronic alcholism Chronic malnourishment Hepatic disease Chronic renal disease Morbid obesity Haematological disease
Patients (no.1 22 3 2 7 9 7 4 1 4 18 7 3 4 4 1 2 it
Number of patients, 79. Patients with 1 risk factor, 57. Patients with z 1 risk factor, 22.
burned size was 56 per cent. Patients who survived more than 48 h had an average age of 54.16 years and an average bum extent of 38 per cent. There is no statistical difference between them. Smoke inhalation injury and ‘shock’ unresponsive to adequate fluid therapy were the main causes of death in the first 48 h. The average burn size for the fatalities (n = 47) was 49 per cent. One hundred and thirteen patients sustained burns covering more than 30 per cent of their body surface, 23 of these patients had only full skin thickness burns. Twentyseven of 47 patients (~7.4 per cent) had full skin thickness bums. As an isolated variable, depth significantly affects the prognosis (PC 0.000001). Thirty-two of the 47 fatalities had greater than 30 per cent TBS (total burned surface) (P
203
Benito-Ruiz et al.: Analysis of bum mortality Table II. Predictive mortality (Ml skin thickness burns) Age (vr) Extent O-5 (%I O-l 0
11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 >91
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
6-10 0 0.1 0.2 0.3 0.4 0.5 0.65 0.75 0.85 0.95
11-15
16-20
21-25
26-30
31-35
36-40
0 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95
0 0.15 0.25 0.35 0.45 0.6 0.7 0.8 0.9 1
0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Table III. LA,, by age
Age group fvr) o-5 6-l 4 15-44 45-60 >60
Full skin thickness burns @I 52 50 46 39 32
There is no statistically significant difference between (2) and (4), but it exists between (I) and (3) at I’< 0.000001. Two formulae indicate the expected probability of death at our centre after burning injury. The first considers the sample without including those patients with only full skin thickness burns (n = 5 7O), and the second one encompasses those patients who sustained only full skin thickness burns on admission (n = 140). Table II shows the classical age/ extent grid for full skin thickness bums. 1. Non-full skin thickness burns: Z = - 0.0618 + O.O013*age -t O.O036*extent i+ 0.05 if associated risk factor + + 0.47 if lung injury Standard error: 0.14 2. Full skin thickness bums: Z = - 0.0326 i- O.O012*age + 0,0054*extent + + 0.147 if associated risk factor + i- 0.5807 if lung injury Standard error: 0.2 Our LA,, (lethal area which determines 50 per cent mortality) is 50 per cent when the sustained bum is full skin thickness. Table III shows the LA,, for the different ages. Thirty-one patients (66 per cent) required ventilatory support due to inhalation injury. The mortality rate was 93 per cent. In 28 patients the cause of the burning injury was flames and three patients were injured by gunpowder. In our experience the presence of lung damage indicates an ominous prognosis.
Discussion The grids of probabilities of mortality for burned patients are a means of comparing results of treatment between bum units. In some ways, they allow us to determine if the standards of care in a bum unit are good, and permit
41-45
46-50
51-55
56-60
61-65
66-70
71-75
76-80
0.1 0.2 0.3 0.4 0.5 0.65 0.75 0.85 0.95 1
0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 1
0.15 0.25 0.35 0.45 0.55 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.65 0.75 0.85 0.95 1 1
0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 1 1
>80 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 1
comparison of successive periods of treatment in any bum unit. The burn team may predict the probability of mortality for a patient admitted to a burn unit using the grid. Nevertheless, we believe that the proper management of a patient should not rely on, or be dictated by, the predictive analysis. Our mortality rate (6.6 per cent) is similar to that reported by Clark and Fromm (1987). The values of the predictive estimate are comparable to those from the grids published by Bull (1971) Zawacki et al. (1979) and Garcia Torres (1989). It is necessary to point out these predictions are approximate, since they are based on data which are assessed on admission by a physician. This is specially applicable to bum depth and the extent of the burned surface. Zawacki et al. (1979) included bum depth in their probit formula. We noticed, reviewing our charts, that although the total extent of the burned area was recorded, there was no classification according to depth. This prevented us from including the percentage of full skin thickness burned area in the regression model. To avoid mistakes in the statistical estimates we decided, first, to consider those patients admitted with only full skin thickness bums, whereas the other formula considers the remaining patients. Age and burn size are closely interrelated concerning prognosis. Patients with bums of more than 30 per cent TBS have a worse prognosis, and mortality increases with age. Elderly patients do not withstand burning injury as well as younger people, and their mortality is high (Herd et al., 1987; Baux et al., 1989). Our mortality ratio for elderly patients (> 70 years) is 32.7 per cent (average age, 78.9 years; average bum size, 20 per cent). This figure is lower than the rate reported recently by Baux et al. (1989) (59 per cent). This good result might follow from our attitude towards these patients which is more ‘conservative’ with delayed debridements (about 10-12 days after injury), whereas we usually perform earlier surgery on younger patients. As with other authors (Zawacki et al., 1979; Tobiasen et al., 1982; Merrell et al., 1987), we believe burn depth is an important factor to be taken into account when predicting mortality rate which, besides age and bum size, contributes markedly to bum severity and outcome. In our patients the mortality rate was higher in males than in females. Men outnumber women (3 : I), and they were more severely burned (especially patients > 70 years). The feasible reason for the predominance of burning injury in male children and teenagers is their playing in a more risky and aggressive way, mainly with fires and small fireworks. The adult males are usually involved in work-related
Burns (1991) Vol. 17/No.
204
accidents. The importance of bum extent in the outcome is shown in Figures 2 and 3. The burn size in men is, on average, more extensive than in women, and justifies their mortality rate. There are more fatalities in females under 10 years old and in the group between 60 and 70 years, but we can not provide an explanation for such a predominance. Respiratory complications are the most frequent cause of death in our patients, commonly secondary to inhalation injuries, both during the early phase of resuscitation and subsequently. Unresponsive ‘shock is the second cause of death in the first 48 h, and sepsis is the main cause of death after the first week. Concurrent risk factors on admission affect the outcome and make the management more difficult. The association of inhalation injury and a poor general condition increases the risk of death at our centre. Our regression analysis shows an increasing deleterious role for the outcome with age, extent of injury, associated risk factor and inhalation injury. Bum depth (full skin thickness burns) also worsens the prognosis. Our team will keep on working to decrease the mortality rate in our centre, and our main objective is to reduce the mortality by inhalation injury, which, in the light of the above results, should be the ‘workhorse’ in our bum centre.
Bull J. P. (1971) Revised analysis of mortality due to bums. Luncet ii, 1133. Clark W. R. and Fromrn B. S. (1987) Burn mortality. Experience at a Regional Burn Unit and Literature Review. Actu Chir. Scund. Suppl. 537,1-126. Davies J. W. L. (1982) Physi&gical Responses to Burning Injury. London: Academic, pp. 1-8. Garcia Torres V. (1989). Quemaduras. Tratamienfo de urgencia. Madrid: Duphar Pharmaceutical (eds), p. 23. Herd B. M., Herd A. H. and Tanner N. S. B. (1987) Burns to the elderly: a reappraisal. Br. J P/asf. Surg. 40, 278. Merrell S. W., Saffle J. R., Sullivan J. J. et al. (1987) Increased survival after major thermal injury. A nine year review. Am. J Surg. 154, 623. Muir I. F. K., Barclay T. L. and Settle J. A. D. (1987) Bums and fheir Treatment. London: Butterworth, pp. 6-10. Shirani K. Z., Pruitt B. A. and Mason A. D. (1987) The influence of inhalation injury and pneumonia on bum mortality. Ann. Surg. 205,82. Thompson P. B., Hemdon D. N. and Traber D. L. (1986) Effect on mortality of inhalation injury. 1. Trauma 26, 163. Tobiasen J., Hiebert J. H. and Edlich R. F. (1982) Prediction of bum mortality. Surg. Gynecol. Obstet. 154, 711. Zawacki B. E., Azen S. P., Imbus S. H. et al. (1979) Multifactorial probit analysis of mortality in burned patients. Ann. Surg.
189, 1.
References
Paper accepted 29 December
Baux S., Mimoun M., Saade H. et al. (1989) Burns in the elderly. Bums 15,239.
Correspowdenceshouti be aaikwd to: Dr J. Benito-Ruiz, c/Hospital, 32, A, 30 8a 46001 Valencia, Spain.
1990.
James Laing Memorial Essay The British Bum Association has instituted a memorial essay to be awarded annually in memory of James Ellsworth Laing, Bum Surgeon, founder member of the British Bum Association and a former Editor of this Journal. There is a prize of up to f500 for the winning essay. The subject for the seventh essay is: ‘Burn wound healing’
The essay should be confined to not more than 10 000 words and correspondingly less if up to 6 Figures and/or Tables are included. The substance of the essay should not already have been published since the winning essay will be published in this Journal. The essays will be assessed anonymously. All persons interested in the problems associated with burning injury are eligible to submit an essay. The deadline for submission of an essay (4 copies) is 31 December 1991. Completed essays and any queries should be sent to the Secretary of the British Bum Association: Dr J. C. Lawrence, PhD., The Bums Research Group, Accident Hospital, Birmingham B15 lNA, U.K. The title and author(s) of the winning
3
essay will be announced
in March or April, 1992.
(1991)
27,
(3), 201-204
201
printed in Great Britain
An analysis of burn mortality: a report from a Spanish regional burn centre J. Benito-Ruiz, A. Navarro-Monzonis,
P. Baena-Montilla and V. Mirabet-Ippolito
Bum Centre ‘La Fe’ Hospital, Vajencia, Spain
This paper reports an analysis of tk mortality rates and relatedfactors in our Burn Centre, based on 710 patients Ire&d belween 1985 and 1988. The average age of tk patients was 23.8 years and the average bum size was 14 per cent of the body surface area. Burning injury affected mainly men (66 per cent), and their mortality rate WIES higher than that women. The overall mortality rate was 6.6 per cent, tk average age of the fatally injured patients being 54 years. We conjirm that mortality in burned patients is closely related to: age (51 per cent of the patients were over 60 years of age): bum size (68 per cent of tk patients had bums coveringmore than 30 per cent TBS); burn depth (57.4 per cent hadfull skin thickness burns); inhalation injuy (present in 66 per cent of the fatally injured); and associated risk factors. The main cause of the burning injury was flames, chiefly from domestic accidents. The average survival time for tk fatally injured patients was 10 days. Finally, our experted mortality followed a linear regression model, tk LA 50for patients with only fill skin thickness burns was 50 per cent.
200 180 160 140 120
of
100 80 60 40 20 n ==I0
II-20
Figure I. Distribution
21-30
31-40 41-50 51-60 Age h)
by age and sex.
61-70
?? , Males;
71-80 N,
281
females.
50 40 ;; ax j; E o?
Introduction It is well known fhat mortality from buming injury has decreased over the last few years. This seems to be due to a better understanding of the physiopathology of the burned patients and improvements in their management (Davies, 1982; Clark and Fromm, 1987; Muir et al., 1987). Age and bum severity have been the main factors related to the outcome (Bull, 1971; Muir et al., x987), but multivariate analyses have proved the role of other factors such as lung injury (Thompson et al., 1986; Shirani et al., 1987), bum depth (Zawacki et al., 1979; Clark and Fromm, 1987) and even associated diseases. This paper investigates the mortality of the patients admitted to and treated in our bum centre during a 4 year period.
Materials and methods The charts of 710 patients admitted to our hospital over the 4 years from December 1984 to December 1988 were reviewed. During this period we treated 9794 burned patients in our casualty department, our admission rate was thus 7.25 per cent. 0 1991 Butterworth-Heinemann 0305-4179/91/030201-04
Ltd
30
_.____~_______-.--~.-.--..-_-~
20 IO 0 ,=I0
II-20
21-30
31-40
41-50 51-60 Age (yr)
61-70
Figure 2. Average of burn size by sex and age. females.
71-80
~81
?? , Males; &S,
The average age of the patients was 23.84 f 24.06 years, 469 of the 710 patients (66 per cent) were male, 308 patients (43.4 per cent) were children under 10 years old, and 55 (7.7 per cent) were older than 70 years. The average extent of the bum was 14 f 17 per cent; minor injuries (< 10 per cent TBS) were very common (62 per cent). The distribution of the admitted victims according to age and sex is shown in Figure I, the average bum size by age and sex is shown in Figure 2. Data were statistically analysed by two commercial programmes (MICROSTATTM and EPISTATTM). A multifactorial linear regression model was used to determine the expected mortality, the variable predictors being: Age, bum extent, inhalation injury and associated risk factors, for patients with partial skin thickness bums. 0 The same as above but for patients who sustained only full skin thickness bums.
0
202
Bums (1991) Vol. 17/No. 3 Table I. Associated risk factors at admission
72
8o
$
70
v)
60
g
50
2
40
8
30 20
Disease
IO 0 C!O
II-20 21-30 31-4041-50 51-60 61-70 71-80 81-90~90 Age (yr)
Figure 3. Mortality by sex and age. ?? , Females; &,
Statistical significances test for 2 x 2 contingency
were obtained tables.
males.
by Fisher’s exact
Results The overall mortality rate in our centre over this 4-year period was 6.6 per cent (47 cases). The average age of these fatalities was 54 years, with 24 of the 47 patients (51 per cent) being older than 60 years. The mortality in this group was 28.2 per cent. There was a statistically significant difference between the mortality rates of the younger and the older patients (PC 0.000001). The mortaIity rate was higher in the males than in the females, with a ratio of 2.36 : 1. Figure 3 shows the number of deaths in both groups, related to age. A fatal outcome is slightly greater in females under 10 years old. In elderly patients (> 70 years) the mortality rate is significantly higher in the men (PC 0.05) (56 per cent vs 15 per cent). As expected we have confirmed the close relationship between mortality rate and age and burn size. In our bum centre we distinguish the following causes of burning injury: scalds, flames, gunpowder, electricity, hot contact, ‘bonfire’, chemicals and others. Bums by bonfire’ are defined as those mainly produced by direct contact with burning coal and with small lighters, candles, and burners of cookers and heaters, depending on the personal view of the physician on duty. We acknowledge it is a badly defined entity, with a potential mix of flames and hot contact, but it is recorded on our charts in that way. Flames caused 76.6 per cent of the deaths, followed by gunpowder (6.4 per cent), ‘bonfire’ (6.4 per cent), scalds (4.2 per cent), electricity (2.1 per cent) and hot contact (2.1 per cent). The high rate of mortality due to flames is associated with more severe bums with respect to extent, depth (frequently deep dermal and full skin thickness bums) and the possibility of pulmonary injury by smoke or toxic-gas inhalation. Gunpowder is involved in work-related accidents, consisting of explosions, occurring while handling, or manufacturing rockets (the fireworks industry is a developed sector in our area and is a means of earning a living for thousands of people). With respect to the location of the accident, 59 per cent of the patients were injured at home, IS per cent while working, 10.6 per cent were involved in traffic accidents, 6.4 per cent occurred in the street, 4.2 per cent were attempted suicides, 2 per cent were due to acts of aggression and 2.8 per cent were unknown. The average length of survival for fatal injuries was 10.7 days. The average age of the patients who died in the first 48 h (resuscitation period) was 54 years and the mean
Diabetes mellitus Lung condition Traumatism Asthma Chronic respiratory disease Neurological condition Epilepsy Vascular Senile dementia Parkinsonism Mental retardation Cardiovascular Gastrointestinal Polytraumatism Chronic alcholism Chronic malnourishment Hepatic disease Chronic renal disease Morbid obesity Haematological disease
Patients (no.1 22 3 2 7 9 7 4 1 4 18 7 3 4 4 1 2 it
Number of patients, 79. Patients with 1 risk factor, 57. Patients with z 1 risk factor, 22.
burned size was 56 per cent. Patients who survived more than 48 h had an average age of 54.16 years and an average bum extent of 38 per cent. There is no statistical difference between them. Smoke inhalation injury and ‘shock’ unresponsive to adequate fluid therapy were the main causes of death in the first 48 h. The average burn size for the fatalities (n = 47) was 49 per cent. One hundred and thirteen patients sustained burns covering more than 30 per cent of their body surface, 23 of these patients had only full skin thickness burns. Twentyseven of 47 patients (~7.4 per cent) had full skin thickness bums. As an isolated variable, depth significantly affects the prognosis (PC 0.000001). Thirty-two of the 47 fatalities had greater than 30 per cent TBS (total burned surface) (P
203
Benito-Ruiz et al.: Analysis of bum mortality Table II. Predictive mortality (Ml skin thickness burns) Age (vr) Extent O-5 (%I O-l 0
11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 >91
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
6-10 0 0.1 0.2 0.3 0.4 0.5 0.65 0.75 0.85 0.95
11-15
16-20
21-25
26-30
31-35
36-40
0 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95
0 0.15 0.25 0.35 0.45 0.6 0.7 0.8 0.9 1
0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Table III. LA,, by age
Age group fvr) o-5 6-l 4 15-44 45-60 >60
Full skin thickness burns @I 52 50 46 39 32
There is no statistically significant difference between (2) and (4), but it exists between (I) and (3) at I’< 0.000001. Two formulae indicate the expected probability of death at our centre after burning injury. The first considers the sample without including those patients with only full skin thickness burns (n = 5 7O), and the second one encompasses those patients who sustained only full skin thickness burns on admission (n = 140). Table II shows the classical age/ extent grid for full skin thickness bums. 1. Non-full skin thickness burns: Z = - 0.0618 + O.O013*age -t O.O036*extent i+ 0.05 if associated risk factor + + 0.47 if lung injury Standard error: 0.14 2. Full skin thickness bums: Z = - 0.0326 i- O.O012*age + 0,0054*extent + + 0.147 if associated risk factor + i- 0.5807 if lung injury Standard error: 0.2 Our LA,, (lethal area which determines 50 per cent mortality) is 50 per cent when the sustained bum is full skin thickness. Table III shows the LA,, for the different ages. Thirty-one patients (66 per cent) required ventilatory support due to inhalation injury. The mortality rate was 93 per cent. In 28 patients the cause of the burning injury was flames and three patients were injured by gunpowder. In our experience the presence of lung damage indicates an ominous prognosis.
Discussion The grids of probabilities of mortality for burned patients are a means of comparing results of treatment between bum units. In some ways, they allow us to determine if the standards of care in a bum unit are good, and permit
41-45
46-50
51-55
56-60
61-65
66-70
71-75
76-80
0.1 0.2 0.3 0.4 0.5 0.65 0.75 0.85 0.95 1
0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 1
0.15 0.25 0.35 0.45 0.55 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1
0.2 0.3 0.4 0.5 0.65 0.75 0.85 0.95 1 1
0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 1 1
>80 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 1
comparison of successive periods of treatment in any bum unit. The burn team may predict the probability of mortality for a patient admitted to a burn unit using the grid. Nevertheless, we believe that the proper management of a patient should not rely on, or be dictated by, the predictive analysis. Our mortality rate (6.6 per cent) is similar to that reported by Clark and Fromm (1987). The values of the predictive estimate are comparable to those from the grids published by Bull (1971) Zawacki et al. (1979) and Garcia Torres (1989). It is necessary to point out these predictions are approximate, since they are based on data which are assessed on admission by a physician. This is specially applicable to bum depth and the extent of the burned surface. Zawacki et al. (1979) included bum depth in their probit formula. We noticed, reviewing our charts, that although the total extent of the burned area was recorded, there was no classification according to depth. This prevented us from including the percentage of full skin thickness burned area in the regression model. To avoid mistakes in the statistical estimates we decided, first, to consider those patients admitted with only full skin thickness bums, whereas the other formula considers the remaining patients. Age and burn size are closely interrelated concerning prognosis. Patients with bums of more than 30 per cent TBS have a worse prognosis, and mortality increases with age. Elderly patients do not withstand burning injury as well as younger people, and their mortality is high (Herd et al., 1987; Baux et al., 1989). Our mortality ratio for elderly patients (> 70 years) is 32.7 per cent (average age, 78.9 years; average bum size, 20 per cent). This figure is lower than the rate reported recently by Baux et al. (1989) (59 per cent). This good result might follow from our attitude towards these patients which is more ‘conservative’ with delayed debridements (about 10-12 days after injury), whereas we usually perform earlier surgery on younger patients. As with other authors (Zawacki et al., 1979; Tobiasen et al., 1982; Merrell et al., 1987), we believe burn depth is an important factor to be taken into account when predicting mortality rate which, besides age and bum size, contributes markedly to bum severity and outcome. In our patients the mortality rate was higher in males than in females. Men outnumber women (3 : I), and they were more severely burned (especially patients > 70 years). The feasible reason for the predominance of burning injury in male children and teenagers is their playing in a more risky and aggressive way, mainly with fires and small fireworks. The adult males are usually involved in work-related
Burns (1991) Vol. 17/No.
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accidents. The importance of bum extent in the outcome is shown in Figures 2 and 3. The burn size in men is, on average, more extensive than in women, and justifies their mortality rate. There are more fatalities in females under 10 years old and in the group between 60 and 70 years, but we can not provide an explanation for such a predominance. Respiratory complications are the most frequent cause of death in our patients, commonly secondary to inhalation injuries, both during the early phase of resuscitation and subsequently. Unresponsive ‘shock is the second cause of death in the first 48 h, and sepsis is the main cause of death after the first week. Concurrent risk factors on admission affect the outcome and make the management more difficult. The association of inhalation injury and a poor general condition increases the risk of death at our centre. Our regression analysis shows an increasing deleterious role for the outcome with age, extent of injury, associated risk factor and inhalation injury. Bum depth (full skin thickness burns) also worsens the prognosis. Our team will keep on working to decrease the mortality rate in our centre, and our main objective is to reduce the mortality by inhalation injury, which, in the light of the above results, should be the ‘workhorse’ in our bum centre.
Bull J. P. (1971) Revised analysis of mortality due to bums. Luncet ii, 1133. Clark W. R. and Fromrn B. S. (1987) Burn mortality. Experience at a Regional Burn Unit and Literature Review. Actu Chir. Scund. Suppl. 537,1-126. Davies J. W. L. (1982) Physi&gical Responses to Burning Injury. London: Academic, pp. 1-8. Garcia Torres V. (1989). Quemaduras. Tratamienfo de urgencia. Madrid: Duphar Pharmaceutical (eds), p. 23. Herd B. M., Herd A. H. and Tanner N. S. B. (1987) Burns to the elderly: a reappraisal. Br. J P/asf. Surg. 40, 278. Merrell S. W., Saffle J. R., Sullivan J. J. et al. (1987) Increased survival after major thermal injury. A nine year review. Am. J Surg. 154, 623. Muir I. F. K., Barclay T. L. and Settle J. A. D. (1987) Bums and fheir Treatment. London: Butterworth, pp. 6-10. Shirani K. Z., Pruitt B. A. and Mason A. D. (1987) The influence of inhalation injury and pneumonia on bum mortality. Ann. Surg. 205,82. Thompson P. B., Hemdon D. N. and Traber D. L. (1986) Effect on mortality of inhalation injury. 1. Trauma 26, 163. Tobiasen J., Hiebert J. H. and Edlich R. F. (1982) Prediction of bum mortality. Surg. Gynecol. Obstet. 154, 711. Zawacki B. E., Azen S. P., Imbus S. H. et al. (1979) Multifactorial probit analysis of mortality in burned patients. Ann. Surg.
189, 1.
References
Paper accepted 29 December
Baux S., Mimoun M., Saade H. et al. (1989) Burns in the elderly. Bums 15,239.
Correspowdenceshouti be aaikwd to: Dr J. Benito-Ruiz, c/Hospital, 32, A, 30 8a 46001 Valencia, Spain.
1990.
James Laing Memorial Essay The British Bum Association has instituted a memorial essay to be awarded annually in memory of James Ellsworth Laing, Bum Surgeon, founder member of the British Bum Association and a former Editor of this Journal. There is a prize of up to f500 for the winning essay. The subject for the seventh essay is: ‘Burn wound healing’
The essay should be confined to not more than 10 000 words and correspondingly less if up to 6 Figures and/or Tables are included. The substance of the essay should not already have been published since the winning essay will be published in this Journal. The essays will be assessed anonymously. All persons interested in the problems associated with burning injury are eligible to submit an essay. The deadline for submission of an essay (4 copies) is 31 December 1991. Completed essays and any queries should be sent to the Secretary of the British Bum Association: Dr J. C. Lawrence, PhD., The Bums Research Group, Accident Hospital, Birmingham B15 lNA, U.K. The title and author(s) of the winning
3
essay will be announced
in March or April, 1992.