Pediatric Age-adjusted Shock Index (SIPA): From Injury to Outcome in Blunt Abdominal Trauma

ABSTRACT

Purpose:

The Shock Index Pediatric Age-Adjusted (SIPA) score is a useful tool for identifying pediatric trauma patients at a risk of poor outcomes and for triaging. We are studying the relationship between elevated SIPA score and specific outcomes in pediatric trauma patients.

Materials and Methods:

A retrospective study was conducted in which case records of 58 pediatric patients with blunt abdominal trauma were evaluated and tabulated for their SIPA scores only at the time of their initial presentation and categorized into two groups – normal SIPA and elevated SIPA. The primary outcomes were need for blood transfusion, need for any intervention, and need for emergency surgery, and the secondary outcomes were need for computed tomography (CT) scan, need for a ventilator, intensive care unit (ICU) stay, length of hospital stay, and mortality. Statistical methods were applied to find a relationship between elevated SIPA score and the primary and secondary outcomes.

Results:

An elevated SIPA score was noted in 27 (46%) patients. There was a significant relationship between elevated SIPA scores and patients needing blood transfusion (68.75%, n = 11) and length of hospital stay (10.48 ± 7.54 days). A significant relationship between elevated SIPA score and need for emergency surgery (54.54%, n = 6), need for a CT scan (56%, n = 14), and ICU stay (50%, n = 2) was not found.

Conclusion:

We have seen in our study that elevated SIPA scores at presentation are significantly related to need for blood transfusion and length of hospital stay. In more than half of the patients, elevated SIPA was associated with need for emergency surgery and requirement of CT scan, but it was statistically not significant. Therefore, assessment of this parameter can help in identifying such poor outcomes.

INTRODUCTION

Blunt abdominal trauma is an important cause of acute abdomen in pediatric age group. The presentation is variable and often depends on the severity, which can be assessed clinically, radiologically as well as using other objective methods of evaluation and scoring systems. The assessment and significance of trauma in a child and adult differ due to various reasons: inability to communicate, availability of a pediatric surgeon or a trauma surgeon trained in the pediatric specialty, anatomic and physiologic differences in an adult and in pediatric age group, and long-lasting consequences of injury in a developing child. Among the various methods used in the past to assess and grade the severity of injury in children, various scoring systems have been identified, which are applicable in an emergency setting including the Glasgow Coma Score, Injury Severity Score, Pediatric Trauma Score (PTS), and Shock Index (SI). Some of these scores have subjective parameters; like in PTS, any extent of wound may not be categorized well with severity. There is also a possibility of missing out few injuries with the Injury Severity Score. With each score having its limitations and being derived from the adult literature, no score has been uniformly adopted for the pediatric population.

SI has well-established use in adult trauma. First described in 1967 by Allgöwer and Burri, this index which is based on screening vitals was subsequently extended to pediatric age group.[1] SI Pediatric Adjusted (SIPA) (heart rate/systolic blood pressure), first proposed by Acker et al.,[2] acknowledges age-specific variation in vital signs to define different thresholds for “elevated” values based on the age-accepted ranges for the patient.

The SIPA score can possibly identify patients who are likely to have worse outcomes, based on their presenting hemodynamic conditions. The significance of this is less well understood in the setting of a resource-challenged nation, where most patients are referred to larger referral centers after significant delay. We studied the SIPA score in pediatric blunt abdominal trauma patients to determine their relationship with clinical outcomes.

MATERIALS AND METHODS

A retrospective review was conducted from January 2017 to April 2021 after approval from the Institutional Ethics Committee (F.1/IEC/MAMC/92/04/2022/No 419). Pediatric patients (age ≤12 years) presenting with blunt abdominal trauma and with or without other system injuries to the Department of Pediatric Surgery were included in the study. In the study, past medical records were reviewed, and demographics along with the clinical data were collected including age at presentation, gender, mechanism of injury, type of injury, need for blood transfusion, clinical stability, need for any intervention or surgery as per standard protocol, requirement and length of intensive care unit (ICU) stay, and length of hospital stay. We included those patients who were solely managed in our department with blunt trauma abdomen irrespective of severity. Children presenting with penetrating trauma and isolated head or chest injury were excluded from the analysis. The documented screening vital signs (blood pressure and heart rate) recorded upon arrival to the initial level of care were noted. The SIPA score was calculated by dividing the heart rate by systolic blood pressure and compared to the age-adjusted cutoff values, as described in Table 1.[2] For every patient, SIPA was calculated upon arrival to the emergency, only once and not at frequent intervals.

Table 1.

Vitals according to age and their corresponding Pediatric Age-Adjusted Shock Index values[2]

Age (years)	Heart rate (beats/min)	Systolic blood pressure (mm/Hg)	SIPA cutoff value
1–3	70–110	90–110	1.2
4–6	65–110	90–110	1.2
7–12	60–100	100–120	1.0
>12	55–90	100–135	0.9

SIPA: Shock Index Pediatric Age-Adjusted

The patients were subsequently classified into two groups – normal SIPA score and elevated SIPA score. Elevated SIPA was defined as the score greater than the SIPA cutoff value of that age [Table 1]. The primary outcome variables evaluated were need for emergency surgery and blood product transfusion within 24 h. The secondary outcome variables evaluated were mortality, need for ICU monitoring, length of hospital stay, and requirement of computed tomography (CT) scan/advanced radiological investigations. Outcome measures were compared between the two subgroups.

The collected data were transformed into variables, coded, and entered into Microsoft Excel (version 16.7)(Redmond, Washington). The data were analyzed and statistically evaluated using SPSS-PC-25 version (Chicago, Illinois). Quantitative data (nonparametric) were expressed in mean with standard deviation or median with interquartile range. Qualitative data were expressed in frequency and percentage, and statistical differences between the proportions were tested by the Chi-square test or Fisher’s exact test. P <0.05 was considered statistically significant.

RESULTS

A total of 58 patients of blunt abdominal trauma in pediatric age group presenting over the study period duration of 4 years and 4 months were included for analysis. The patient demographics are described in Table 2.

Table 2.

Description of demographic and clinical data of patients presenting with blunt abdominal trauma

General characteristics of patients with blunt abdominal trauma	n
Total number of patients	58
Mean age of presentation (years)	6.9±3.03
Median age at presentation (years) (IQR)	5.2 (4–6)
Duration since injury (range)	1.5 days (2 h–48 h)
Male: female ratio	1.9:1
Mechanism of injury
RTA	35
Missing	2
Others%	21
Number of patients with e-FAST positive, n (%)	43 (74.13)
Number of patients with requirement of CT scan, n (%)	35 (60.34)
Spectrum of injury
Abdominal injury	30
Hollow viscera only	5
Solid organ injury (liver, renal, and pancreatic injury)	24
Hollow viscera + solid organ injury	1
Abdominal + chest	7
Limb fracture	9
Abdominal + head injury	2
Urogenital injury	3
Number of patients needing ICU admission, n (%)	4 (6.9)
Number of patients needing blood transfusion, n (%)	16 (27.6)
Number of patients needing emergency surgery, n (%)	11 (18.96)
Mean duration of hospital stay (days)	10.48±7.54

^%Mechanisms of injuries defined as “others” included fall from height, assault, fall at level, fall of a blunt object on the abdomen, and cycle handle injury. RTA: Road traffic accident (hit by a motor vehicle), e-FAST: Extended focused assessment with sonography in trauma, ICU: Intensive care unit, CT: Computed tomography, IQR: Interquartile range

An elevated SIPA score was noted in 27 (46%) patients, as described in Table 3. As SIPA values are standardised and age adjusted [Table 1], patients in our study were categorized according to age and we noted that significantly higher number of patients with normal SIPA scores were found between 4-6 years interval and with elevated SIPA scores were found between 7-12 years age interval. More males presented with elevated SIPA score, but this difference was not statistically significant.

Table 3.

Categorization of children with normal and elevated Pediatric Age-Adjusted Shock Index score

	Normal SIPA (n=31)	Elevated SIPA (n=27)	P
Age category (years)
0–3 (n=7)	5	2	0.43
4–6 (n=19)	17	2	<0.001
7–12 (n=32)	9	23	<0.001
Gender
Male (n=38)	18	20	0.20
Female (n=20)	13	7	0.20
Mechanism of injury
Missing (n=2)	1	1	1.0
RTA (n=35)	20	15	0.48
Others (n=21)	10	11	0.50
Traumatic brain injury
Yes (n=2)	1	1	1.0
No (n=56)	30	26	1.0
Type of injury
Fracture (n=9)	4	5	0.72
Chest (n=7)	4	3	1.0
Urogenital (n=3)	0	3	0.09
Gastrointestinal tract (n=30)	14	16	0.30

RTA: Road traffic accident, SIPA: Pediatric Age-Adjusted Shock Index

The most common mode of injury was road traffic accident, of which an elevated SIPA score was observed in 15 (42.85%) cases. Road traffic accident injuries included pedestrian injuries and bicycle injuries. Elevated SIPA scores were noted in 53.3% of patients with abdominal injury.

Upon outcome evaluation, we observed a significant 68.75% of patients with elevated SIPA score who required blood transfusion. Emergency surgery was required in 18.96% of cases with elevated SIPA; however, the difference between the two subgroups was not statistically significant. Fifty-six percent of patients requiring a CT scan and 50% of patients with requirement of ICU stay had an elevated SIPA score. However, this was not statistically significant. The length of hospital stay in patients with normal SIPA value was 5.77 ± 2.98 days and 10.48 ± 7.54 days with elevated SIPA values, which was noted to be statistically significant (P < 0.01) [Table 4]. Thus, a patient presenting with an elevated SIPA score was likely to have a significantly higher need for blood transfusion and a more likely requirement for emergency surgery, radiological evaluation, and ICU stay. However, in our study, requirement of emergency surgery and radiological evaluation was not significant, which can be attributed to small sample size.

Table 4.

Primary and secondary outcomes among children with normal and elevated Pediatric Age-Adjusted Shock Index score

	Normal SIPA (n=31)	Elevated SIPA (n=27)	P
Need for blood transfusion	5	11	0.04 (significant)
Need for emergency surgery	5	6	0.55
Need for minor intervention	2	4	0.40
Need for CT scan	11	14	0.0
ICU stay	2	2	1.0
Length of hospital stay	5.77±2.98	10.48±7.54	<0.01 (significant)
Mortality	0	0	-

CT: Computed tomography, ICU: Intensive care unit, SIPA: Pediatric Age-Adjusted Shock Index

DISCUSSION

Triage is a core and very effective principle in managing pediatric and adult trauma, which helps us select patients requiring inpatient management and intervention, and aids in timely referral. Signs and symptoms in children are often not as obvious as they are in adults; therefore, a system appropriate for pediatric patients must be adopted. Rapid assessment and intervention are crucial in preventing potentially life-threatening complications. McFadyen et al. emphasize the importance of early recognition and management of hypovolemia and shock in pediatric trauma patients.[3]

Our study probably represents the first work examining the utility of SIPA in evaluation of blunt abdominal trauma in India. The goal of our study was to analyze the correlation of SIPA score at the time of presentation in blunt abdominal trauma patients with outcome measures. We reviewed 58 patients with blunt abdominal trauma, out of which 31 had a normal SIPA score and 27 presented with an elevated SIPA score. We evaluated both primary outcomes (need for blood transfusion; need for any intervention, like intercostal drain; and need for emergency surgery) and secondary outcomes (need for CT scan, need for ventilator, ICU stay, length of hospital stay, and mortality) with respect to the SIPA scores. When comparing patients who presented with elevated versus normal SIPA scores, those with elevated SIPA scores were more likely to require blood transfusion and have longer hospitalizations. This highlights the importance of early identification of patients needing admission and inpatient management. We did not find any significant correlation between elevated SIPA scores and mechanism or type of injury, need for any surgical intervention or radiological investigation, and ICU stay.

Acker et al.,[2] in their study of 559 children, concluded that SIPA score was more accurate than age-adjusted hypotension values for trauma team activation. They further extended the comparison between SIPA score and age-adjusted hypotension values for the need of three emergency interventions – intubation, blood transfusion, and operative intervention. They noted an increased SIPA score was associated with a longer hospital and ICU stay. Increased SIPA scores were also helpful in segregating the cases who required early surgical intervention and thus helped in effective triaging. They had also demonstrated that increased SIPA serves as a marker for severity of injury and is associated with a greater mortality rate. Nordin et al.[4] noted that longer hospital and ICU stay and mortality were associated with elevated SIPA. Patients with prehospital elevated SIPA had a higher mean duration of hospital stay, as also noted in our study.

However, most of the trauma scoring systems in use for pediatric trauma are derived from experience with adult trauma, which underscores the importance of variability of pediatric physiology in comparison to adults. In addition, anatomical scoring systems like the Injury Severity Score (ISS) are subjective and physiological derangements are not included. Various studies have highlighted these shortcomings. In a study by Reppucci et al., they noted that an ISS <16 in traumatic brain injury in a pediatric patient needs more attention than ISS <14 in a long bone fracture in an adult.[5]

Thus, comparing or triaging pediatric trauma in a manner like an adult with a common score may not be justifiable and highlights the need for better pediatric scores.

Reppucci et al. highlight the potential clinical implications of using the SIPA as a tool for predicting outcomes compared to traditional vital signs such as heart rate and blood pressure. The finding underscores the importance of using the SIPA in the initial assessment of pediatric trauma patients, as it can provide valuable information that may not be immediately apparent based on traditional vital signs alone.[5]

SI is a simple clinical tool which is used to identify patients who might be at a risk of shock. The SI is calculated by dividing the heart rate by the systolic blood pressure. The Pediatric Age-Adjusted SI (SIPA) adjusts the calculation for age, as children have a higher heart rate and lower blood pressure than adults.[6]

Another scoring system used in pediatric trauma is PTS. A study has compared the utility of PTS and SIPA. PTS is a scoring system that considers various physiological and anatomical parameters to assess the severity of trauma and predict patient outcomes. In contrast, SIPA is a clinical tool that calculates the adjusted SI in pediatric patients to help identify those at risk of shock. The article concluded that PTS is useful in more “high-risk” settings, although both are reliable indicators. However, the calculation of PTS also requires more variables, unlike SIPA, making SIPA an effective scoring tool when resources are limited or during triage.[7] A retrospective study has also concluded that the SIPA could serve as a dynamic trend for predicting shock in pediatric patients in warzone settings.[8]

In a resource-limited setting, such as India, where this study has been conducted, since the services of a pediatric or trauma surgeon may not always be available, it becomes necessary to identify the most emergent cases for early referral to a higher center. In this situation, the utility of available resources to calculate a screening score based on vital parameters, like the SIPA score, can be immensely helpful. It can easily be calculated by any emergency team person present in the emergency using simple tools such as heart rate and blood pressure. A study conducted with 1648 participants found that SIPA score is superior to SI in both resource-abundant and resource-limited settings.[9] Another study concluded that SIPA score is a better predictor of severity than SI in cases of both blunt and penetrating trauma.[4]

CT scan is an expensive radiological method to assess abdominal trauma. A study conducted at a level 1 pediatric trauma center included a preintervention phase where patients received routine care and a postintervention phase where an evidence-based guideline significantly reduced the number of CT scans performed without missing any injuries that required intervention. The study concluded that the implementation of the evidence-based guideline can effectively reduce unnecessary CT scans in the assessment of blunt pediatric trauma. There were no differences in SIPA scores between the patients before or after guideline implementation.[10] Our study did not find a significant correlation between elevated SIPA score and requirement of a CT scan. Literature has also shown the importance of monitoring serial SIPA values in management of pediatric trauma patients. The development of an elevated SIPA during the first 12 h of care and the failure to normalize SIPA has been shown to be associated with worse outcomes by Vandewalle et al.,[11] with an increased need for transfusion and longer hospital stay. Subsequently, other studies have also validated these findings that SIPA could identify severe injury, transfusion needs, and mortality in pediatric trauma patients more accurately than “unadjusted” SI utilizing a single, uniform threshold.[12]

In a retrospective cohort study of 2651 patients, SIPA was calculated utilizing prehospital vital signs (EMS SIPA) and vital signs upon arrival at trauma bay (ED SIPA). The findings of this study are significant as they indicate that prehospital calculated SIPA can be an effective tool for identifying trauma patients who require the highest level of activation. This finding can have significant implications for EMS providers and can lead to improved patient outcomes. The study concluded that SIPA in trauma bay was better than EMS SIPA.[13]

Lerner et al. highlighted the importance of establishing a consensus-based definition of criteria for the activation of the highest level of pediatric trauma team. Having a clear and standardized set of criteria can help ensure that appropriate level of care is provided to pediatric trauma patients, regardless of where they receive care.[14] This is also what we are set out to do in our study.

Another retrospective study conducted in 2019 investigated the need for early surgeon presence in the setting of pediatric trauma. The study aimed to identify patients who require early surgical intervention. It predicted independent risk factors for defining NSP, and some of them were Injury Severity Score, SIPA, and SIPA combined with GCS. The Injury Severity Score has limitation of score calculation after accurate identification of all the injuries, which makes it a subjective criterion and may lead to over- and undertriage. ISS has a sensitivity of 61% for NSP. SIPA was predictive of NSP, independent of GCS. SIPA has been used in the past in prediction of severity of injury based on ISS.[15]

Thus, SIPA is a very effective evaluation for pediatric trauma. The score can be calculated by basic vital parameters by a doctor present in the emergency. It will further help in early referral and decision-making.

Limitations

Our results have shown that there was no significant difference in the patients with elevated SIPA and normal SIPA when role of surgical intervention, requirement of CT scan, and ICU stay was considered. The relationship between operative intervention and mortality with an elevated SIPA score has been noted in other studies such as Acker et al. and Nordin et al.[2,4] Relations to mortality could not be established due to lack of data.

Our study has found strong correlations with elevated SIPA scores, considering that it was an observational retrospective study because of which our study designs were limited, and that it was a single-center study, making the sample size small. A prospective study correlating various parameters and SIPA score should be conducted at a tertiary care center to derive more definite conclusions and at a larger scale.

Further, a comparison between PTS and SIPA scores can be done, both of which are severity assessment scores in case of pediatric trauma.

CONCLUSION

Our study has highlighted the importance of the use of SIPA score to identify pediatric blunt abdominal trauma patients that are at a higher risk of poor outcomes. Although, in our study, a significant correlation was found between an elevated SIPA with need for blood transfusion and length of hospital stay. It is also important to note that elevated SIPA was also associated with more than half of the patients requiring CT scan and emergency surgery, although not statistically significant. Hence, the key message is that, while evaluating patients with blunt abdominal trauma, SIPA may guide us in identifying children at high risk and predicting poor outcomes directly or indirectly, but more extended study needs to be done with requirement of more number of patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.