Summary

Objective

To investigate the incidence of systemic inflammatory response syndrome (SIRS) on emergency department admission and the prognostic significance of SIRS in patients undergoing emergency surgery.

Methods

This is a retrospective study of 889 adults who were admitted as emergency cases and were operated on within 24 hours of admission. Data on patient demography, clinical information including comorbidities, categories of surgery, American Society of Anesthesiologists physical status, SIRS score, postoperative outcomes including duration of mechanical ventilation, intensive care unit (ICU) and hospital lengths of stay, and mortality were collected.

Results

SIRS occurred in 43% of the patients and was associated with a significantly worse outcome in terms of duration of ventilator use (10.5 ± 15.4 vs. 3.5 ± 4.4 days, p < 0.001), ICU stay (11.2 ± 13.6 vs. 5.0 ± 5.4 days, p < 0.001), hospital length of stay (19.4 ± 22.4 vs. 7.1 ± 7.6 days, p < 0.001) and mortality (12.7% vs. 0.4%, p < 0.001). After adjusting for covariates (including age, gender, American Society of Anesthesiologists physical status, comorbid conditions, and surgery categories), SIRS was independently associated with higher mortality (adjusted odd ratio, 21.5; 95% confidence interval (CI), 4.9–93.2), longer ventilator duration (adjusted coefficient, 7.8; 95% CI, 3.2–12.5), longer ICU stay (adjusted coefficient, 6.2; 95% CI, 2.6–9.8) and longer hospital stay (adjusted coefficient, 9.7; 95% CI, 7.5–11.9).

Conclusion

The presence of SIRS at admission in patients receiving emergency surgery predicted worse outcomes and higher mortality rates.

Keywords

American Society of Anesthesiologists physical status;emergency surgery;postoperative outcome;systemic inflammatory response syndrome

1. Introduction

Compared with planned elective surgery, emergency surgery carries a higher risk of morbidity and mortality.1; 2; 3 ;  4 When a patient requires an emergency operation, it is important to identify which subgroups of patients are at high risk of developing complications. The American Society of Anesthesiologists (ASA) physical status is routinely used to provide a patients overall preoperative health status.5 Anesthesiologists worldwide use ASA physical status to predict operative risk. However, it has been criticized because of the inconsistent rating of the status by different anesthesiologists.6 ;  7

Systemic inflammatory response syndrome (SIRS) is a clinical response to an inflammatory, infectious, or tissue traumatic stimulus. The concept of SIRS was developed by the American College of Chest Physicians/Society of Critical Care Medicine Committee in 1992.8 SIRS occurs if at least two of the following criteria are present: (1) hyperthermia >38°C or hypothermia <36°C, (2) heart rate >90/min, (3) respiratory rate >20/min or PaCO2 <32 mmHg, (4) white cell count >12,000/μL or <4000/μL, or >10% immature white cells. With these clear definitions, clinicians can easily assess whether SIRS is present in these patients. Our purposes were to investigate the incidence of SIRS upon emergency department (ED) admission and the prognostic significance of the SIRS score in patients who were operated on within 24 hours of admission.

2. Materials and methods

The study protocol (200804029R) was approved by the institutional review board of the National Taiwan University hospital, Taipei, Taiwan. We included all patients 18 years of age or older who were admitted between February 2007 and January 2008 to the ED of this tertiary-care university hospital and who were operated on within 24 hours of admission. Parturients in need of emergency cesarean section and in-hospital patients requiring emergency surgery were excluded. A total of 889 patients were included in the final analysis. Demographic data, preexisting medical conditions, and information about surgical procedures were retrieved from medical records. Comorbid diseases were recorded only if documented by a physician in the medical records. The ASA physical status was obtained from the anesthetic charts. The SIRS criteria were retrieved retrospectively from the immediate data upon the ED arrivals. The SIRS scores were obtained by calculating the presence of the SIRS criteria. The severity of SIRS was gauged on a 0 to 4 scale (from 0 point to 4 points), with 1 point added for each SIRS criterion present. The outcomes of interest included in-hospital mortality, intensive care unit (ICU) admissions, ICU length of stay (LOS), hospital LOS, and duration of postoperative mechanical ventilation.

2.1. Statistics

The baseline characteristics of the study participants were reported as mean ± standard deviation or proportions, as appropriate. Univariate analysis was performed to evaluate the differences between SIRS and non-SIRS patients on age, gender, comorbidity, ASA physical status, and types of surgery. Results were expressed as odds ratios with their 95% confidence intervals. One-way analysis of variance was used to compare continuous variables across different SIRS scores, and linear contrasts analysis of variance was used to test the trend. Chi-square test or t-test was used to test the correlation between SIRS and ventilator duration, ICU admission and LOS, hospital LOS, and mortality. The results were considered statistically significant when the p value was <0.05 in two-tailed test. Statistical calculations were performed using SAS, version 9.13 (SAS Institute, Cary, NC, USA) and R, version 2.8 (The R foundation for Statistical Computing).

3. Results

The study comprised 483 males and 406 females. The mean age of the studied patients was 48.9 ± 19.7 years (range 18–97 years). The main categories of surgery performed in our sample were as follows: gastrointestinal (n = 310), orthopedic (n = 146), neurosurgical (n = 102), gynecologic (n = 81), plastic (n = 67), and cardiovascular (n = 60 cases) surgical procedures. Less frequently, patients required ear, nose, and throat, ophthalmologic, thoracic, or urology procedures. In this study, the number of patients assigned with ASA physical status I, II, III, IV, and V were 123, 348, 266, 137, and 15, respectively. A total of 357 (40.2%) patients showed at least one comorbid disease, with the three most common being hypertension (23.6%), diabetes mellitus (12.4%), and heart disease (8.9%). The mean hospital LOS was 12.7 ± 17.2 days. The overall mortality rate for the entire study population was 5.7% (51/889).

3.1. Incidence and characteristics of SIRS patients

SIRS occurred in 386 (43.4%) patients upon ED admission. Compared with patients without SIRS, patients with SIRS were mainly male, were older (age ≥ 65 years), had a significantly higher ASA physical status (ASA ≥ III), had a comorbid disease, and were undergoing emergency gastrointestinal surgery, cardiovascular surgery, or neurosurgery (Table 1).

Table 1. General characteristics of patients with and without SIRS.
Variables Non-SIRS SIRS OR p
(n = 503) (n = 386)
Sex
 Male (%) 248 (49.30) 235 (60.88) 1
 Female (%) 255 (50.70) 151 (39.12) 0.62 (0.48–0.82) <0.001*
Age, mean ± SD 46.37 ± 19.05 52.23 ± 20.07 <0.001*
 <65 y 403 (80.12) 257 (66.58) 1
 ≥65 y 100 (19.88) 129 (33.42) 2.02 (1.49–2.74) <0.001*
ASA
 I 99 (19.68) 24 (6.22) 1 <0.001*
 II 249 (49.50) 99 (25.65) 1.64 (0.99–2.71) 0.05
 III 125 (24.85) 141 (36.53) 4.65 (2.80–7.72) <0.001*
 IV 30 (5.96) 107 (27.72) 14.71 (8.06-26.87) <0.001*
 V 0 (0.00) 15 (3.89) Inf 0.96
Type of surgery (%)
 Gastrointestinal 126 (25.05) 184 (47.67) 1 <0.001*
 Orthopedic 114 (22.66) 32 (8.29) 0.19 (0.12–0.30) <0.001*
 Neurosurgical 56 (11.13) 46 (11.92) 0.56 (0.36–0.88) 0.012*
 Gynecologic 66 (13.12) 15 (3.89) 0.16 (0.08–0.28) <0.001*
 Plastic 45 (8.95) 22 (5.44) 0.33 (0.19–0.58) <0.001*
 Cardiovascular 16 (3.18) 44 (11.40) 1.88 (1.04–3.58) 0.043*
 Ear–nose–throat 28 (5.57) 17 (4.40) 0.42 (0.21–0.70) 0.007*
 Ophthalmologic 28 (5.57) 6 (1.55) 0.15 (0.05–0.34) <0.001*
 Thoracic 14 (2.78) 13 (3.37) 0.63 (0.29–1.40) 0.26
 Urologic 10 (1.99) 7 (1.81) 0.48 (0.17–1.28) 0.14
Comorbidity
 Hypertension 96 (19.09) 114 (29.53) 1.78 (1.30–2.43) <0.001*
 Diabetes mellitus 34 (6.76) 76 (19.69) 3.38 (2.22–5.25) <0.001*
 Heart disease 28 (5.57) 51 (13.21) 2.58 (1.60–4.18) <0.001*
 Malignancy 18 (3.58) 40 (10.36) 3.12 (1.78–5.65) <0.001*
 Stroke 19 (3.78) 18 (4.66) 1.25 (0.65–2.41) 0.51
 Lung disease 9 (1.79) 24 (6.22) 3.64 (1.73–8.36) 0.001*
 Renal disease 9 (1.79) 21 (5.44) 3.16 (1.43–6.97) 0.004*
 Liver disease 4 (0.80) 14 (3.63) 4.69 (1.63–16.67) 0.006*
  • p < 0.05.

ASA = American Society of Anesthesiologists; OR = odds ratio; SIRS = systemic inflammatory response syndrome.

3.2. SIRS and associated clinical outcomes

Analyses were conducted to evaluate the association between SIRS and clinical outcomes. The clinical outcomes of the SIRS score in the entire study population are depicted in Table 2. Compared with patients without SIRS, those who developed SIRS before emergency surgery required postoperative ventilator more frequently and had longer mechanical support (10.5 ± 15.4 vs. 3.5 ± 4.4 days, p < 0.001); therefore, they were more likely to be admitted to an ICU after surgery (51.0% vs. 10.1%, p < 0.001), they stayed longer in the ICU (11.2 ± 13.6 vs. 5.0 ± 5.4 days, p < 0.001), their hospital LOS was also longer (19.5 ± 22.4 vs. 17.1 ± 7.6 days, p < 0.001), and their mortality rate was higher (12.7% vs. 10.4%, p < 0.001). Table 2 shows that there is a significant trend of linear increase in resource utilization and mortality with increasing SIRS scores.

Table 2. Clinical outcomes according to the SIRS score.
SIRS score (patient number) 0 points (224) 1 point (279) 2 points (211) 3 points (131) 4 points (44) p p for trend
Mechanical ventilation day 3.06 ± 3.94 3.85 ± 4.77 5.14 ± 6.66 13.5 ± 19.02 13.37 ± 15.30 <0.001* <0.001*
ICU admission, % 8.93 11.11 35.07 64.89 86.36 <0.001* <0.001*
ICU LOS, mean ± SD 4.65 ± 5.06 5.29 ± 5.68 6.53 ± 6.73 13.6 ± 15.65 15.08 ± 16.18 <0.001* <0.001*
Hospital LOS, mean ± SD 7.23 ± 7.78 7.01 ± 7.59 12.67 ± 13.89 27.49 ± 27.38 28.20 ± 27.97 <0.001* <0.01*
Mortality, % (number) 0.00 (0) 0.72 (2) 5.69 (12) 12.21 (16) 47.73 (21) <0.001* <0.001*
  • p < 0.05.

ICU = intensive care unit; LOS = length of stay.

The results of univariate analyses had identified a high-risk group of patients with poor clinical outcomes: patients with SIRS, aged 65 years or above, classified as ASA class III or above, and who required an emergency major surgery, such as general, cardiovascular, or neurosurgical surgery. Therefore, it was interesting to investigate the effects of SIRS after controlling for other factors associated with the clinical outcomes. Table 3 shows that patients with SIRS had an adjusted risk of requiring ventilator support that was sevenfold as high as those who did not develop SIRS. The presence of SIRS in patients was associated with a sixfold and a 10-fold increase in risk of remaining in the ICU and the hospital after emergency surgery, respectively. The mortality in SIRS patients was even more striking: a 21-fold increase in risk of death after controlling for age, gender, ASA physical status, comorbidity, and surgical category.

Table 3. SIRS and clinical outcomes including ventilator duration, length of stay, and mortality.
Non-SIRS SIRS Adjusted p
(n = 503) (n = 386)
Ventilator duration
 Mean ± SD (d) 3.49 ± 4.40 10.52 ± 15.40
 Adjusted coefficient (95% CI) Reference 7.83 (3.19–12.49) <0.01*
ICU stay
 Mean ± SD (d) 5.04 ± 5.40 11.22 ± 13.60
 Adjusted coefficient (95% CI) Reference 6.26 (2.68–9.85) <0.001*
Hospital stay
 Mean ± SD (d) 7.10 ± 7.66 19.47 ± 22.40
 Adjusted coefficient (95% CI) Reference 9.76 (7.56–11.93) <0.001*
Mortality
 Rate, % (number) 3.92 (2) 12.69 (49)
 Adjusted OR (95%) Reference 21.58 (4.97–93.27) <0.001*
  • p < 0.05.

CI = confidence interval; ICU = intensive care unit; OR = odds ratio.

4. Discussion

The present study aims to shed more light on the prognostic significance of SIRS, particularly in patients admitted as emergency cases and who were operated on within 24 hours of admission. Sometimes, some patients who are undergoing emergency surgery are not afforded time for optimization of their health care needs, and the preoperative evaluation might have to be limited to simple and critical tests. Therefore, it is essential to have a tool that can use the available data to identify patients at risk of requiring postoperative intensive care and of developing complications.

SIRS can stem from an infectious or a noninfectious cause that activates an excessive immuno-inflammatory cascade.8 It is accepted that the overwhelming proinflammatory response may lead to the clinical manifestation of SIRS, organ failure, and even death.9 Several previous studies had examined SIRS criteria as a predictor of prognosis in certain patient groups. Asayama and Aikawa10 had reported the usefulness of SIRS criteria in predicting outcomes in patients who are hospitalized through emergency services. Their study showed that the requirement for hospital admission and the mortality rate were both significantly higher in patients with SIRS. Napolitano et al11 demonstrated that the presence of SIRS upon hospital admission following trauma was an independent predictor of mortality. Yoshimoto et al12 showed that admission SIRS was highly associated with the severity of subarachnoid hemorrhage. The presence of SIRS on admission also predicted a poor prognosis in patients with subarachnoid hemorrhage.12

Comparison of our study population with patients undergoing emergency abdominal surgery shows that they share similar results in that any degree of systemic inflammation predicted poor outcomes.13 ;  14 Our patients were more heterogeneous—an entire population of emergency patients requiring different kinds of surgeries. Our purpose was to examine whether the SIRS score could be used as an outcome predictor in a more generalized patient population, in an attempt to construct a real-life scenario of our daily work. In addition, the study demonstrated that the higher the SIRS score, the worse the outcomes of patients undergoing emergency surgery.

Our study has several limitations. First, our research was a retrospective study and was thus constrained by the limitations therein. Second, because the study was limited to a single center, the results might not apply to other patient populations. Third, our study was unable to target any preventable risk factors associated with the development of SIRS. We identified a group of patients who were most likely to develop SIRS: patients with male gender, older age, comorbidity, and high ASA physical status, and undergoing gastrointestinal, cardiovascular, or neurosurgical procedure. Since SIRS can progress downstream the continuum of sepsis to severe sepsis and to septic shock, the presence of SIRS alerts physicians to adopt the use of early goal-directed therapy.15; 16 ;  17 Early recognition and timely appropriate management would improve outcomes in patients with SIRS undergoing emergency surgery.

In conclusion, the admission SIRS score can serve as a simple and useful predictor of postoperative outcomes in patients undergoing emergency surgery. The presence of SIRS predicted poor outcomes and mortality.

Acknowledgments

None.

References

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