Annals of Burns and Fire Disasters - vol. XII - n° 4 - December 1999

SUMMARY. In order to evaluate the contribution of four individual factors (respiratory rate, heart rate, body temperature, and white blood cell count) to the diagnosis of the systemic inflammatory response syndrome (SIRS) in patients with burn trauma, a multiple regression analysis was performed between the S1RS score and the organ dysfunction score. The relationship between the number of days of SIRS with regard to the different criteria and organ dysfunction was also analysed. In relation to the criteria of burn patients with severe SIRS, the concentrations of T3 and T4 in the serum were detected by radioinummoassay. The results showed that the four factors made a different contribution to the occurrence of organ dysfunction. The order of importance of the factors, from large to small, was as follows: respiratory rate, heart rate, body temperature, white blood cell count. Severe SIRS was responsible for organ dysfunction. T3 and T4 concentrations in burn patients with severe SIRS were significantly lower than those in burn patients with nonsevere SIRS. The SIRS score can therefore be used as a predictor of organ dysfunction.

When a person suffers a burn injury, the integrity of the skin is destroyed, causing local and systemic inflammatory reaction. The mediators of inflammation include the kinin system, the coagulation and fibrinolytic systems, the complement system, cytokines, etc. The role of cytokines, which have been deemed to be responsible for mortality in burn patients, is especially important. When we measured the activity of several cytokines and toxic products in serum from burn patients, we were unable to delineate clear pictures of the roles of many cytokines and products of immune cells. We therefore used the systemic inflammatory response to describe the condition of the disarray. In 1992 the American Committee of Chest Physicians/Society of Critical Care Medicine (ACCP/ SCCM) Consensus Conference Committee proposed the term "systemic inflammatory response syndrome" (SIRS) to indicate the body's reaction to injury or infection. Patients can be diagnosed as having SIRS if they present two or more of the following criteria:

1. body temperature over 38 °C or less than 36 °C;
2. heart rate greater than 90 beats per minute;
3. respiratory rate greater than 20 breaths per minute or PC02 less than 32 mm Hg;

4. white blood cell count greater than 12 x 10 or less than 4 x 10, or the presence of more than 10% immature neutrophils.

On the basis of these criteria, 68% of the patients admitted to our intensive care unit met the standard. SIRS therefore showed itself to be too sensitive to reflect the severity of a disease state. When we used SIRS in severely burned patients, the same problem was encountered in clinical practice. In order to overcome the defects of SIRS in assessing patients' conditions, we therefore developed a scoring system for SIRS, and examined its relationship to organ dysfunction.

This retrospective study was carried out on severely burned patients treated in the Burns Centre, Changhai Hospital, China from January 1990 to July 1998. The criteria for enrolment in the study were as follows:

1. admission to the hospital within 24 h post-injury;
2. survival longer than 15 days in the hospital;
3. injury by flame or fluid without chemical damage;
4. age between 18-60 yr;
5. no pre-existing pathologies;
6. TBSA over 50%.

During the period of study 52 patients were found to meet the criteria for inclusion (47 male, 5 female), with a mean age of 33.5 ± 12.9 yr, mean TBSA 73.1 ± 14.4%, mean full-thickness burn area 35.6 ± 27.9%, and mean deep-partial thickness burn area 32.5 ± 20.0%. The patients surviving more than 30 days were 48 in number (44 male, 4 female), with a mean age of 32.1 ± 12.6 yr, mean TBSA 72.5 ± 13.8%, mean full-thickness burn area 33.8 ± 27.2%, and mean partial-thickness burn area 31.9 ± 19.3%. In order to maintain urine output at a level of I ml/kg/h, the patients were immediately given fluid resuscitation with crystal and colloidal solutions including 5% glucose in normal saline, Ringer's solution, human plasma, alburnin, dextran 70, etc. after admission. The wounds were treated with occlusive dressings and topical silver sulphadiazme. If the patients had full-thickness burn wounds, escharectomy was performed 48-96 hr postlesion. During this operation, sufficient full blood was given (1 mi/kg/l% TI1SA).

SIRS scoring system
Data regarding the burn patients' rectal temperature, heart rate, respiratory rate, and white cell count were collected at 6:00 a.m. every day. At this time the patients were seldom being disturbed by medical practices and their real conditions were thus accurately reflected. The SIRS scoring system is listed in Table 1.

Scoring method for organ dysfunction
Organ dysfunctions were evaluated by the standards set by Marshall (Table II).

Detection of T3 and T4 concentration
The concentration of T3 and T4 in the serum of burned patients was detected by radioimmunoassay (RIA). The patients were divided into two groups, with either severe SIRS or SIRS on the basis of the SIRS scoring method (Table III).

Statistical analysis
All values were expressed as mean value ± SI). The statistical comparison of group values included multiple regression analysis and the Student t test.

Results

Progressive multiple regressive analysis
During the first fifteen days post-burn, the formula describing the contributions of the four elements of SIRS to organ dysfunction in severely burned patients was as follows: Y = 0.23282X3 + 0.03574X2 + 0.00035X, -0.00475X4 -2.381 (X,, breathing rate;X2, heart beats; X3, body temperature; X4, WBC counts). The multiple relative coefficient was R = 0.743 (p < 0.01). The regression contributions of breathing rate, heart beat, body ternperature, and WBC counts were respectively 237, 84, 11, and 2. During the thirty days of treatment of the severely burned patients, the formula of progressive multiple regressive analysis was as follows: Y = 0.10819X, + 0.01819X2 + 0.00323X4 + 0.00236X, -1.85-1. The multiple relative coefficient was R = 0.780 (p < 0.0 1). The regression contributions of breathing rate, heart beat, body teinperature, and WBC counts were respectively 207, 116, 29, and 22. The contributions of the four SIRS criteria to multiple organ dysfunction were, in diminishing order, breathing rate, heart beat, body temperature, and WBC counts after fifteen and thirty days.
On the basis of the above analyses, we proposed a standard method for the diagnosis of severe SIRS (see Table 3). Using this scoring method to re-evaluate the relation between SIRS and organ dysfunction, we found that patients presented organ dysfunction when their SIRS score was above 4 on five consecutive days. The criteria could therefore be used as a predictor of organ dysfunction and regarded as indicative of severe SIRS.
Using the SIRS criteria, the number of days corresponding to two of the four conditions was 27.9 ± 4.4 days, while the coefficient of the correlation with organ dysfunction was R = 0.338 (p < 0.01). Although some patients had been long diagnosed as having SIRS, they did not all present symptoms of organ dysfunction, which means that the criteria for SIRS in severely burned patients were too sensitive - the number of days fitting three criteria was 19.9 ± 8.1 days. The coefficient of the SIRS correlation with organ dysfunction was R = 0.542 (p < 0.01); the number of days fitting the four criteria was 9.0 ± 7.8 days.
The coefficient of the SIRS correlation with organ dysfunction was R = 0.366 (p < 0.05).
The levels of T3 and T4 in burn patients with severe SIRS were lower than patients with non-severe SIRS (nmol/L: T3, 0.51 ± 0.25 vs 1.45 ± 0.50, p < 0.01; T4, 168.4 ± 72.5 vs 85.0 ± 10.5, p<0.01).

The role of SIRS in the development of the multiple organ dysfunction syndrome (MODS) has been documented in several studies, and no one doubts the deleterious effects of SIRS on organ functionality. It is also true that in severely burned patients the longer patients present a state of SIRS the more chance they have of developing organ dysfunction. However, the duration of SIRS corresponding to ACCP/SNIMC standards was 28 days within a month in burn patients with over 50% burned TBSA, as in the analyses described in this article, and some patients were in a stable condition even though they were in a state of SIRS. In these circumstances, we considered how it might be possible to use the ACCP/SMMC definitions of SIRS to describe the progressive pathophysiological disarrangement thought to be associated with the development of MODS and thus give an indicator for earlier therapeutic intervention and the standardization of research protocols. The analysis of our data demonstrated that different elements made different contributions to the development of MODS, and that it was wrong to give each element the same weight in the diagnosis of SIRS. The respiratory rate should be taken very much in consideration. An increase in the respiratory rate indicates the body's need of oxygen and/or respiratory insufficiency. Patients with SIRS usually display a hypermetabolic rate, which presents the symptoms of anabolism, negative nitrogen balance, and high~ventilation volume. All these have deleterious effects on the power of the oxygen supply in the tissue of severely burned patients, in whom respiratory insufficiency is always a sign of organic damage in multiple organ failure.
One of the interesting findings in this study was the role of the white cell count in the diagnosis of SIRS. The white cell count had no relation to organ dysfunction. Chitnis has demonstrated that the life span of neutrophils from burr) patients is longer than that in healthy persons.` This is because the presence of GM cerebrospinal fluid in the serum of burn patients inhibits the apoptosis of polymorphonuclear neutrophils, and even more markedly the stem cells differentiated into white blood cells under the stimulation of inflammation. In some patients the white cell count was therefore high. Conversely, the body's reaction to the same stimulation was minimal in some patients, which caused a lower white blood cell count in the circulation, while the patients were in fact severely ill. The factors of body temperature and heart rate contributed to organ dysfunction, the former to a lesser extent than the latter.
On the basis of these analyses, we concluded that the four elements for the diagnosis of SIRS play different roles in the development of organ dysfunction. When we used SIRS to predict the occurrence of organ dysfunction, it was found to be inappropriate to regard each of four elements of SIRS as playing the same role. We found that burn patients with severe SIRS presented lower T3 and T4 serum concentrations than patients with SIRS. This was confinnation of the previous observation that T3 and T4 concentrations were significantly lower and persisted during unstable clinical conditions.
It is therefore necessary to use the SIRS score in evaluating the gravity of the disease in seriously burned patients.

RESUME. Pour évaluer la contribution de quatre facteurs (rythme respiratoire, rythme cardiaque, température corporelle, taux leucocytaire) dans le diagnostic du syndrome de la résponse inflammatoire systémique (sigle anglais, SIRS), les Auteurs ont effectué une analyse de régression multiple entre le score du SIRS et le score de la dysfonction organique. Ils ont aussi analysé le rapport entre les journées de la présence du SIRS et les divers critères de la dysfonction organique. Selon les critères des patients atteints d'un SIRS grave, ils ont évalué la concentration de T3 et T4 avec la technique du radioimmunoessai. Les résultats ont indiqué les contributions différentes des quatre facteurs à la manifestation de la dysfonction organique. L'ordre décroissant d'importance était: rythme respiratoire, rythme cardiaque, température corporelle, taux leucocytaire. Le SIRS sévère était responsable de la dysfonction organique. La concentration de T3 et de T4 dans les patients brûlés atteints de SIRS grave était significativement plus bas de celle des patients atteints de SIRS non grave. Le score du SIRS peut donc être utilisé comme pronostiqueur de la fonction organique.