Pediatric Adjusted Shock Index as a Predictor of Mortality by Sex Disparity in Pediatric Trauma: A Pan-Asian Trauma Outcome Study (PATOS)

Abstract

Background

There are no reports of sex-specific, pediatric age-adjusted shock index (PASI) for pediatric trauma patients in previous studies. We aimed to determine the association between PASI and in-hospital mortality of pediatric trauma patients and whether this association differs depending on sex.

Methods

This is a prospective, multinational, and multicenter cohort study using the Pan-Asian Trauma Outcome Study (PATOS) registry in the Asia-Pacific region, conducted in pediatric patients who visited the participating hospitals. The main exposure of our study was abnormal (elevated) PASI measured in an emergency department (ED). The main outcome was in-hospital mortality. We performed a multivariable logistic regression analysis to estimate the association between abnormal PASI and study outcomes after adjusting for potential confounders. An interaction analysis between PASI and sex was also conducted.

Results

Of 6,280 pediatric trauma patients, 10.9% (686/6,280) of the patients had abnormal PASI. In multivariable logistic regression analysis, abnormal PASI was significantly associated with increased in-hospital mortality (aOR, 1.71; 95% confidence interval [CI], 1.16—2.53). Abnormal PASI had interaction effects with sex for in-hospital mortality (aOR, 1.86; 95% CI, 1.18—2.92 and aOR, 1.38; 95% CI, 0.64—2.95 for male and female, respectively) (p < 0.01).

Conclusions

Abnormal PASI is associated with increased in-hospital mortality in pediatric trauma patients. The prediction power of PASI for in-hospital mortality was maintained only in male patients. Further studies with sex- and age-specific shock index and age-specific are warranted.

Introduction

Traumatic injury is the leading cause of mortality in pediatric patients (1). Rapid and accurate identification of severe trauma patients and appropriate triage are important in reducing mortality (2). In recent years, research studies have focused on evidence-based criteria for determining trauma team activation or treatment direction of trauma patients; these criteria help optimize the classification of such patients and efficiently distribute trauma-related resources (3).

The shock index (SI), defined as the heart rate (HR) divided by systolic blood pressure (SBP), has been used to identify mortality, the need for massive transfusions, and as a marker, even in the presence of severe trauma (4–6). However, because limitations have been reported in applying the SI equally to all age groups, pediatric age-adjusted shock index (PASI) values have subsequently been defined to account for variations in physiologically normal ranges displayed in pediatric populations (2). PASI has been validated in pediatric trauma patients by demonstrating its utility in predicting the severity of injury, need for blood transfusion, surgical procedures, and mortality (2, 7, 8).

Although there are no reports of sex-specific SI or PASI, a previous report on the sex-specific normal value of SI stated that the SI of females patients tended to be higher than those of male patients of all ages (9). Therefore, changing patterns of physiological indicators, including SBP and HR after trauma, may differ according to age and sex at the same age (10).

Studies on the prediction utility of PASI are limited in pediatric trauma patients, and no study has considered physiological differences according to sex. Therefore, we hypothesized that the PASI can predict the mortality of pediatric trauma patients and that these prediction utilities would differ according to sex.

Our study aimed to determine the association between PASI and mortality in pediatric trauma patients and whether this association differs depending on sex.

Methods

Results

Discussion

Using a prospective international multicenter registry of injury in the Asia-Pacific region, the results of this study showed that elevated PASI was associated with a higher probability of in-hospital mortality and poor functional recovery in pediatric trauma patients. In the interaction analysis, elevated PASI was associated with increased in-hospital mortality only in males but not in females. This research contributes to a better understanding of the usefulness of PASI in predicting the clinical outcome of pediatric trauma patients who visit the ED. Furthermore, it shows a limit to applying the previously suggested cut-off value of PASI to predict mortality regardless of sex.

SI predicts hemodynamic instability more sensitively than traditional vital signs such as SBP and HR. In a prospective study evaluating hypovolemia detection, SI was a more accurate predictor of acute changes in the blood volume than was SBP or HR alone (17). Furthermore, in studies of geriatric patients, SI predicted the overall mortality better than did traditional vital signs (18). A study of pediatric patients with sepsis reported a higher mortality risk with increasing SI, although there was no clear cut-off value (19). Studies to predict mortality in adult trauma patients have used abnormal SI, defined as SI > 0.9 to 1, as a cut-off value for mortality prediction (20). However, it is not ideal to apply the cut-off value of adult physiological indicators to pediatric patients due to their unique anatomy and physiological differences compared to adults. Furthermore, the pattern and degree of changes in vital signs, such as SBP and HR, when bleeding from trauma occurs in pediatric patients are different from those in adults (21).

To increase the ability of SI to predict clinical outcomes in pediatric trauma patients, age-specific SI was applied to pediatric trauma patients in several studies (22–24). PASI was found to be a good predictor of mechanical ventilation or blood transfusion needs, increased intensive care unit hospitalization, and longer in-hospital stays (22–24). However, previous studies on PASI mainly focused on blunt injured pediatric patients; hence, studies on the generalizability of PASI to indicate negative clinical outcomes and the need for increased resources for pediatric patients who sustain injuries other than blunt injury are limited.

Our study targeted all pediatric trauma patients, and to our knowledge, is the first study to suggest the association between SI and functional outcome of pediatric trauma patients. In our study, although elevated SI and elevated PASI were associated with worse clinical outcomes, the associations with PASI in predicting worse clinical outcomes were stronger, similar to that in previous studies.

In the interaction analysis of our study, elevated PASI was associated with in-hospital mortality in males but not in females. However, regardless of sex, the SI of nonsurvivors was higher than that of survivors, suggesting that setting of the cut-off point requires sex-specific adjustment, and is not a functional limitation of the SI itself.

In previous studies, the SI of females was higher than that of males in all age groups, and in the study of SI components, although SBP did not show a clear difference according to sex, HR showed a significantly higher tendency in females than in males (9, 25). Although no sex-specific studies have reported changes in vital signs, including SBP and HR, after trauma, it can be expected that the male group with a low baseline SI would show a generally decreasing trend even after trauma. Hence, elevated PASI in males indicates a poorer physiological state compared to females, and this eventually leads to worse clinical results.

In our study, as in previous studies, the normal cut-off values for SI were 1.22, 1.0, and 0.9 for ages 4—6, 7—12, and 13—18 years, respectively. However, based on the results of our study, it would be more appropriate for the female cut-off value to be higher than the current value.

Although PASI is an important predictor of in-hospital mortality and poor functional recovery in pediatric trauma patients, the results of our study, which have different predictive powers according to sex, provide a theoretical basis that sex-specific and age-specific normal values of SI may be more effective in screening for trauma severity than a single-value threshold.

This study has several limitations that need to be addressed. First, although intentionality, activity at the time of the injury, location, and mechanism of injury were adjusted in the multivariable logistic regression analysis; hence, the effect of the characteristics of trauma itself on the study outcomes could not be completely excluded. Second, pediatric patients may have inaccurate measurements of vital signs at ED compared to adults, possibly affecting the study results. Third, although several age-specific cut-off values for SI have been suggested in previous studies, one of the values was taken and used in our study, which may have resulted in a bias. Fourth, investigators in the PATOS registry were not blinded to the study hypothesis, which could have led to biased data collection. Finally, since this was not a randomized controlled trial, there could have been some potential biases that were not controlled.

Conclusions

Abnormal PASI is associated with increased in-hospital mortality and poor functional recovery in pediatric trauma patients; however, the prediction power of mortality is significant only in male patients. More studies on sex- and age-specific cut-off value of SI are warranted to predict clinical outcomes in pediatric trauma patients.

Declarations

Data availability

The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request (Email: em.ryu.hyunho @gmail.com)

Author Contributions

Conceptualization: EJ, YSR

Data curation: EJ and SDS

Formal analysis: EJ

Funding acquisition: SDS

Investigation: EJ and HHR

Methodology: HHR

Software: EJ

Supervision: EJ and HHR

Validation: EJ and YSR

Visualization: EJ and YSR

Writing - original draft: EJ

Writing - review & editing: HHR

Approval of the final manuscript: all authors

Declaration of Interest

The authors have no potential conflict of interest to declare.

Funding

There was no funding for this study.

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