Mortality according to age and burned body surface in the Virgen del Rocio University Hospital

Burns 25 (1999) 317±323

Mortality according to age and burned body surface in the Virgen del Rocio University Hospital T. GoÂmez-CõÂ a *, J. MalleÂn, T. MaÂrquez, C. Portela, I. Lopez Unidad de Quemados, Hospital Universitario Virgen del RocõÂo, Avda. Manuel Siurot s/n, 41013 Seville, Spain Accepted 5 August 1998

Abstract The application of updated clinical protocols for the treatment of burned patients is showing very good results. The mortality curves according to age and the percentage of burned body surface could be of great use for the comparison of clinical results between di€erent burns units. The probability of survival in 1000 consecutive patients admitted to the Burns Unit of the Virgen del Rocõ o University Hospital between July, 1993 and August, 1997, is compared, by graphic analysis, with the mortality curves of other centers, obtaining similar results. We conclude that the results of medical attendance in our unit are in line with those considered as a reference. # 1999 Elsevier Science Ltd and ISBI. All rights reserved. Keywords: Burns; Probability of death; Mortality curves; Evaluation of medical attendance

1. Introduction The importance of the problem of burns and the social, family and individual impact this produces depends on the severity, which varies according to the circumstances of each case. Prevention, based on an extensive epidemiological analysis of the surrounding social environment, is the best treatment possible for both severe and minor burns [1]. However, when the accident has already taken place, the reaction of the social agents (®remen, police, catastrophe alarm systems, etc.) and health care agents (health care emergency systems, healthcare network, etc.) have a vital in¯uence on the ®nal outcome of our patients [2]. The highly specialized treatment of a burned patient is normally carried out, in our country, in a burns center or unit, generally situated in specialized third level and/or university hospitals, using expensive human * Corresponding author.

and material resources to palliate the severe e€ects that a burn accident has on the human being. The advances in the treatment of burned patients has signi®cantly decreased the mortality rates in the last twenty years. A better knowledge of the physiopathology of a burn, the improvement in the resuscitation therapy with reanimation ¯uids, the control of infections, the initiation of adequate metabolic and nutritional support, the prompt coverage of the burn and the early initiation of rehabilitation are some of the milestones that have contributed to the long-term increase in survival of our patients [3]. This general outline of treatment of the burned patient, summarized in this introduction, is applied in the Burns Unit of the Virgen del Rocõ o University Hospital of Seville, Spain. The objective of this study is to analyze the comparability of our results in medical attendance to internationally accepted reference data. Under these circumstances, we would be achieving one of the aims of this unit, initiated 30 years ago, which is to give the optimum treatment to each burn patient of our healthcare district.

0305-4179/99/$20.00+0.00 # 1999 Elsevier Science Ltd and ISBI. All rights reserved. PII: S 0 3 0 5 - 4 1 7 9 ( 9 8 ) 0 0 1 2 6 - 0

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Fig. 1. Distribution, according to age and percentage of burned body surface, of 1000 consecutive patients treated in the Burns Unit of the Virgen del Rocõ o University Hospital of Seville, during a 4-year period. Predominant are those patients between 20 and 40 years of age, although the most numerous population was that of patients under 10 years of age with burns a€ecting less than 20% of the body surface. Patients with more than 41% of the body surface burned were a minority.

2. Material and methods One-thousand consecutive patients, admitted to the Burns Unit of the Virgen del RocõÂ o University Hospital of Seville and treated between July, 1993 and August, 1997, were included in this retrospective study. No patient was excluded because of age, percentage of burned body surface (%BBS), the depth or cause of the lesions. The parameters of age, %BBS and survival were extracted, for further analysis, from the database where the characteristics of each patient and the lesions were registered. All patients received the same treatment throughout the four years analyzed. The resuscitation of patients with severe burns depended on age: for children (5

years of age), we applied the indications of the Shriner's Burn Institute of Galvestone, Texas [4]. The rest of the patients were reanimated following the B.E.T. indications [5]. The scarotomies and/or scarectomies were done on an emergency basis, if necessary. Topical treatment of the burns consisted in the daily or twice daily application of 1% argentic sulphadiazin, with or without cerium, depending on the severity of the lesion (Flammazine and Flammazine cerio, Duphar S.A., Solvay), after washing with a soapy diluted chlorhexidine solution (Hibiscrup, Zeneca Farma S.A., Madrid, Spain). The patients received oral nutrition, mixed oral and enteral nutrition, only enteral or parenteral nutrition, all depending on the clinical situation. The diet was, in all cases, hypercaloric and hyperproteic. The energy requirements were

T. GoÂmez-CõÂa et al. / Burns 25 (1999) 317±323 Table 1 Demographic pro®le of the population studied according to the survival or not to the burn accident. A 26 years old patient with a severe traumatism, and an additional 2% BBSA, died as a consequence of his injuries in the Trauma Intensive Care Unit of our Hospital Total

Survive

Die

1000

934

66

96 0.5 33 23.63

96 0.5 31 22.93

92 1 55.21 21.9

% BBS Maximum Minimum Mean S.D.

100 1 17 18.24

90 1 14.13 13.65

100 2 53.06 31.68

Mortality (%)

6.6

0

100

Number Age Maximum Minimum Mean S.D.

319

semisynthetic biologic dressings (Biobrane, Dow Hickan Pharmaceuticals, TX) or cryopreserved skin homografts from multiorgan donors of our hospital. De®nite coverage of the burn was done with laminar autografts, meshed skin autografts (Tanner Vanderputt, Zimmer) or ¯aps (random, axial or free) according to the indications and the availability in each case. The donor areas of skin grafts of partial thickness were treated with a hydrocolloid dressing (Varhiesive Gel Control, Bristol Myers Squibb) after hemostasia with the topical application of a 1/500.000 solution of adrenaline in isotonic saline solution. The di€erent complications, are septic, respiratory (produced by the inhalation of toxic substances), traumatologic, etc., provoked by the accident or appearing throughout the clinical course of the cases, were merged in collaboration with the di€erent specialists of a third level University Hospital such as ours. The variables measured in the 1000 patients included in the study were introduced in a calculus sheet (Excel, Microsoft Oce, Version 6.0, Microsoft Corporation), creating a numerical matrix of 3  1000 elements. The mean and standard deviation was obtained for each of the variables: age (years), burned body surface area (% BBSA) and survival (1 = survival, 0 = death). A `smoothing' procedure is applied with the Q-Splines technique (`Statgraphics' Statistical Graphics System, Version 1.1, 1985 STSC and Statistical Graphics). This procedure produces an `almost cubic' line through a sequence of paired data. By this statistical procedure, the discrete values of the matrix are transformed into almost continuous values. Graphic analysis of the probability of survival of the patients according to age and the % BBSA was done in two ways: as a tridimensional surface and by the projection of the contour lines of this surface on a plane, also called level curves. In order to permit comparisons, part of the results published by two di€erent groups of authors, at two

calculated according to the modi®ed Long formula [6]. These estimations were con®rmed weekly by indirect calorimetry (Monitor Deltatrac II, Datex, Helsinki, Finland). The protein requirements were obtained from the daily nitrogen balance. Analgesia consisted mainly of the administration of morphine chloride. The levels of analgesia obtained were measured at regular and frequent intervals. We used P.C.A. devices frequently (Patient Controlled Analgesia; Pain Management Provider, Abott Laboratories, North Chicago, IL). The more painful procedures and surgery were done in cooperation with the Anaesthesia Department. From the third day after the burn we carried out, in those cases indicated, tangential or fascial excisions with temporary or de®nite coverage of the surgical wound. For the temporary coverage we used

Table 2 Probability of death (in decimals) of the burn patients attended in the Burns Unit of the Virgen del RocõÂ o University Hospital of Seville (Spain), according to age (in decades) and the percentage of BBS Age (years)

0±10 11±20 21±30 31±40 41±50 51±60 61±70 71±80 81±90 91±100

% BBS 0±10

11±20

21±30

31±40

41±50

51±60

61±70

71±80

81±90

91±100

0 0 0.01 0 0.02 0 0.06 0 0.06 0.83

0.01 0 0 0.03 0.03 0 0 0.22 0.14 0.98

0 0 0 0 0.1 0.1 0 0.6 0.5 1

0 0 0 0.09 0.25 0 0.5 0.75 1 1

0.15 0 0 0 0 0 0.2 1 1 1

0.3 0 0 0 0 0 0.65 1 1 1

0.47 0 0 0.67 0.75 1 1 1 1 1

0.7 0.5 0.31 0.75 0.85 1 1 1 1 1

0.85 0.67 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1

320

T. GoÂmez-CõÂa et al. / Burns 25 (1999) 317±323

Fig. 2. Tridimensional representation of the probability of death (in decimals) of 1000 consecutive patients treated in the Burns Unit of the Virgen del RocõÂ o University Hospital of Seville. Mortality increased with age and the percentage of burned body surface.

di€erent moments, 1954 [7] and 1996 [8], were represented graphically by the same two procedures described. No other type of analysis of the di€erences observed was made since the information available was not comparable in all cases. 3. Results Fig. 1 represents the distribution of the 1000 patients studied. Approximately half of the patients had burns of less than 10%. The majority of the patients were between 20 and 40 years of age. Patients under 10 years of age, with burns that a€ect less than 20% of the body surface also comprise a large group. Burns of less than 30% in patients between 20 and 60 years of age are also frequent. Fortunately, the number of patients with burns greater than 41% of the body surface admitted to our unit was low. Table 1 shows how the patients that died in our unit were the oldest (55.02 years, s.d. 21.9) and with a signi®cantly greater burned body surface (% BBSA average 53, S.D. 31.7) than patients that survived (31

years, S.D. 22.9, and 14.3% BBSA, S.D. 13.6, respectively). Table 2 shows the probability of death of the burn patients treated in our unit for each age and % of BBS. The tridimensional representation of the numerical matrix of mortality, proceeding from Table 2, is shown in Fig. 2. The contour or level lines, graphically obtained from the projection on a plane of the tridimensional surface, re¯ect the areas with the same probability of death for each age and percentage of burned body surface. Fig. 3 represents the areas corresponding to 1000 consecutive patients treated in our burns unit in the last 4 years. In Figs. 4 and 5 we represent the mortality rate of two previous studies, that of Bull and Fisher, carried out on 2807 consecutive burn patients treated in the Massachusetts General Hospital, between 1939 and 1954 [7] (Fig. 4) and the study of Pruitt et al., done on a series of burn patients treated between 1987 and 1991, in the United States Army Institute of Surgical Research [8] (Fig. 5). We can observe the e€ect of the current clinical protocols, applied to the treatment of

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321

Fig. 3. Graphic representation of the probability of death (in decimals) for each age and % of BBS in 1000 consecutive patients treated in our burns unit during the last four years, shown as level curves or contours obtained from the tridimensional surface of Fig. 2. Compare these mortality curves with those represented in Figs. 4 and 5.

the burned patient, on the fall in the probability of death. The results of our unit (Fig. 3) are comparable to those considered as accepted standards at present (Fig. 5) and, hence, much better than results considered historical (Fig. 4). 4. Discussion The percentage of body surface burned is one of the main determining factors of the severity of a burn. Age also plays an important role. For this reason, these are two of the most frequently included parameters in the prognosis of patients that are admitted to burns units. According to Pruitt [8], Holmes, as early as 1860, emphasized the importance of the extent of body burned on the survival of the patients. Germann [9] states that Wiedenfeld, in 1902, correlated the burned body surface and age with the mortality of his patients. Bull and Squire [7, 10] introduced statistical

models of logistic regression, establishing, with the same parameters and after studying an extensive series of patients, the probability of survival in their hospital during that period and for this pathology. Various authors have given similar contributions [8, 11]. There is no doubt that, besides the age and the body surface burned, there are other risk factors that determine the severity of the burn. As an example, the abbreviated burn severity index (ABSI), which includes the patient's sex, depth of the lesions and the existence or nonexistence of a lung a€ectation due to inhalation, described, in 1982, by Tobiasen et al. [12], has a greater predictive value of the course of a burn patient upon admission to the unit. If additional factors are considered in the groups of borderline patients, such as pre-existing diseases or the abuse of toxic substances, the speci®city (the patients that will predictably survive versus the patients that actually survive) and sensitivity of the predictions (patients that predictably will not survive versus patients that do not survive) improve [9].

322

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Fig. 4. Graphic representation of the mortality contours obtained from data published by Bull and Fisher in 1954 [7].

However, this same author states that the predictions based exclusively on age and the % of BBS (body surface area burned) achieve sucient speci®city for clinical and scienti®c goals, although he believes that the low sensitivity found in the analysis weakens the precision of the prediction if additional factors are not considered. The survival of the patients attended in the burns units is the aim of these units. All the resources, e€orts and dedication of the personnel that participate in teams dedicated to medical attendance, including clinical and experimental investigation related to burns, have this common objective. In everyday practice this means the use of consensed clinical protocols by the specialists in this area. After being applied in our burns units, the eciency of these protocols must be evaluated. We believe that a proper method would be to compare our own results with those considered standard, proceeding from internationally homologated units or centers. Statistical analysis in depth has not been possible, since we could not obtain data from other centers comparable to our own.

So, we have considered that the curves of survival of the patients who attended our unit could be used as a control of their e€ectiveness, when compared with those published by authors of international prestige. We have selected a classic contribution for this purpose, that of Bull and Fisher, 1954 [7, 10], due to its originality at that moment in time and because the clinical protocols used then were clearly di€erent from the present ones. As a representation of the burns units with results that are currently homologated (rati®ed) we have selected, among many possible candidates, the Burns Unit of the United States Army Institute of Surgical Research, considering its important role in the subject we are studying [8]. We believe that the representation, as level curves, of the probability of death in our center permits an e€ective visual comparison with the two series mentioned. It is evident, when comparing data from the early 1950's with data from the early 1990's, that the improvement of the clinical protocols applied to these patients is related to a signi®cative increment in survival after a burn. Similar results were clearly described

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323

Fig. 5. Graphic representation of the mortality contours obtained from data published by Pruitt and Mason in 1996 [8].

by Pruitt when analyzing two burn populations treated at the same center during two periods separated by more than 20 years (1959±1963 and 1987±1991) [8]. On the other hand, we can observe, in the same ®gure, how the curves of probability of survival/death according to age and BBS% of our unit are very similar to those published by Pruitt et al. and ratify, at least from our point of view, our activity concerning medical attendance. We conclude that the application of the present clinical protocols of burn treatment permit the obtention of results that can be rati®ed. The curves of mortality according to age and BBS% are a simple and e€ective implementation for the comparison of clinical results among di€erent burns units, as long as the population studied is sucient and as uniform as possible. The time course of this type of curve in a speci®c unit can be useful in evaluating its long-term eciency, in addition to measuring the impact that the changes of strategies have on the ®nal results. References [1] FernaÂndez-Morales E, GaÂlvez-Alcaraz L, FernaÂndez-CrehuetNavaÂjas J, GoÂmez-Gracia E, Salinas-Martõ nez J. Epidemiology of burns in MaÂlaga, Spain. Burns 1997;23(4):323±32.

[2] Arturson G. Analysis of severe disasters. In: Massellis M, Gunn S, editors. The management of mass burn casualties and ®re disasters: Proceedings of the First International Conference on Burns and Fire Disasters, ch. 4. Dordrecht/Boston/London: Kluwer Academic Publishers, 1992. p. 24±33. [3] Rose J, Herndon D. Advances in the treatment of burn patients. Burns 1997;23 (Suppl. 1):S19±S26. [4] Carvajal H. Fluid therapy for the acutely burned child. Compr Ther 1977;3(3):17±24. [5] GoÂmez-Cõ a T, Roa L. A burn patient resuscitation therapy designed by computer simulation (BET). Part 2: initial clinical validation. Burns 1993;19(4):332. [6] Long C. Energy expenditure of major burns. J Trauma 1979;19:904±5. [7] Bull JP, Fisher AJ. A study of burns at the Massachusetts General Hospital, 1939±1954. Ann Surg 1954;145:210. [8] Pruitt BA, Mason A. Epidemiological, demographic and outcome characteristics of burn injury. In: Herndon D, editor. Total burn care. London: Saunders Co., 1996. p. 13. [9] Germann G, Barthold U, Lefering R, Ra€ T, Hartmann B. The impact of risk factors and pre-existing conditions on the mortality of burn patients and the precision of predictive admissionscoring systems. Burns 1997;23(3):195±203. [10] Bull J, Squire J. A study of mortality in a burns unit. Ann Surg 1949;130:160. [11] Barisoni D, Peci S, Governa M, Sanna A, Furlan S. Mortality rate and prognostic indices in 2615 burned patients. Burns 1990;16:273. [12] Tobiasen J, Hiebert J, Edlich R. A practical burn severity index. J Burn Care 1982;3:229.