Shock indices as predictors in blunt trauma patients in the emergency department

ABSTRACT

Aims

To evaluate the effectiveness of Shock Index (SI), Modified Shock Index (MSI), and Age Shock Index (Age SI) in predicting blood transfusion need, surgical intervention, hospital outcomes, and injury severity in blunt trauma patients.

Methods

This retrospective study included 267 adult patients admitted with blunt trauma to the emergency department of a tertiary university hospital between 1 December 2018, and 1 December 2019. Patients with isolated hand/foot trauma, isolated traumatic brain injury, isolated spinal injuries, or minor trauma (AIS ≤2) were excluded. SI, MSI, and Age SI were calculated and analyzed.

Results

SI (p < 0.001), Age SI (p = 0.001), and MSI (p < 0.001) were significantly associated with blood transfusion and mortality. SI > 0.933 and MSI > 1.159 showed good predictive accuracy for blood transfusion; Age SI > 30.945 showed moderate accuracy. For mortality, SI > 1.015, MSI > 1.333, and Age SI > 67.065 demonstrated good predictive power (all p < 0.001). SI and MSI correlated moderately with injury severity (p < 0.001), with SI > 0.905 and MSI > 1.181 indicating significant predictive value.

Conclusion

SI, MSI, and Age SI can predict early blood transfusion and mortality in blunt trauma patients. SI and MSI appear more reliable than Age SI, particularly in predicting transfusion need and injury severity.

1. Introduction

Trauma is the most common cause of death in young people and is a major financial problem worldwide. Bleeding accounts for approximately 50% of deaths within 24 hours of trauma and is the leading preventable cause of death [1]. Identification of patients with severe bleeding is of utmost importance as they are at risk of developing hemorrhagic shock leading to high morbidity and mortality [2], so patients requiring bleeding control as well as those who may require intensive transfusion need to be rapidly identified [3].

Delays in trauma resuscitation are associated with increased morbidity and mortality. Traditional vital signs have a high specificity when grossly abnormal, but are relatively insensitive as early diagnostic markers of compensated hemorrhagic shock [4].

Recent studies have found that the “Shock Index” (SI), defined as heart rate (HR) divided by systolic blood pressure (SBP), predicts trauma outcomes better than vital signs, Glasgow Coma Scale (GCS) or injury mechanism alone [2,5–7]. The shock index (SI) is sensitive to even small changes in circulating blood volume and has been found to be useful in predicting the need for intervention and massive transfusion. However, SI does not reflect diastolic blood pressure (DBP) and age. “Modified shock index” (MSI) and “Age-related shock index” (age SI) include mean arterial pressure (MAP) and age, and have recently been used in the prognosis of critically ill patients. MSI is calculated by dividing the heart rate by the mean arterial pressure, providing an assessment of the diastolic blood pressure (DBP) compared to the traditional shock index. MSI has been proposed as a potentially more accurate predictor of clinical outcomes in trauma patients compared to traditional SI. This index has been found to provide valuable insights into the patient’s hemodynamic status, particularly in terms of predicting the need for early intervention such as blood transfusions and surgeries [2]. It is well known that in elderly patients, physiological reserves are reduced, and mortality is more pronounced. Accordingly, the ‘age SI’ is calculated by multiplying the patient’s age by the SI. In the literature, these indices have been shown to be more effective than HR, SBP, DBP or SI alone in predicting mortality [8].

The aim of this study was to determine the relationship between shock index values and the need for blood transfusion, surgical intervention, hospital outcomes, and injury severity in patients presenting with blunt trauma to the emergency department (ED).

2. Methods

2.1. Study design

The data obtained from patients admitted to the ED of a university hospital providing tertiary health care services were analyzed retrospectively. Approval for the study was obtained from xxx University Clinical Research Ethics Committee dated 30 June 2020 and numbered 2020/680. As a retrospective study, informed consent forms were not required to be obtained from the patients.

2.2. Inclusion criteria

The study population consisted of adult patients (≥18 years) with blunt trauma who were hospitalized between 1 December 2018, and 1 December 2019, and for whom complete data were available.

2.3. Exclusion criteria

Patients presenting with burns, pregnant women, isolated hand and foot trauma, patients with isolated traumatic brain injury and isolated spinal and spinal injuries, patients with minor injuries, patients under 18 years of age and patients with missing data were excluded.

Patients with penetrating injuries (sharps and gunshot wounds), underwent prehospital intubation and cases of cardio-pulmonary arrest were also excluded because of the possibility of hemodynamic instability and considering that it would affect the results of the study.

2.4. Data analysis

Shock index was defined as HR divided by SBP, modified SI was defined as HR divided by MAP; and Age SI was defined as age multiplied by SI. Blood transfusion requirement was defined as the need for any blood product replacement (erythrocyte, fresh frozen plasma (FFP), platelet transfusion) in the first 24 hours; massive transfusion was defined as the need for ten or more units of erythrocyte transfusion in the first 24 hours after injury or more than 4 units in 1 hour; and intervention requirement was defined as the need for interventional radiology and surgery. Mechanisms of injury were classified as motorcycle accident, vehicular traffic accident, pedestrian injury, simple fall, fall from height and other injuries. Injuries were defined as extremity, thorax, abdomen, pelvis and multiple sites according to anatomical regions.

Demographic information, GCS values, injury sites and mechanisms, laboratory parameters, blood transfusion and surgical needs, duration of hospitalization, hospital outcomes, shock indices (SI, MSI and age SI), Injury Severity Score (ISS) values calculated together with AIS were recorded on the data forms prepared in advance. In determining the severity of injury, an ISS of ≤ 15 was considered as mild and moderate injury, while an ISS of > 15 was classified as severe and profound injury.

The primary outcomes were the need for blood product transfusion and surgical intervention, while the secondary outcomes included in-hospital mortality (hospital outcomes) and the determination of injury severity.

2.5. Statistical analysis

The distribution of the data was checked by Shapiro Wilk test. Since the distribution assumption was not met, numerical variables were summarized as median and categorical variables were summarized as number and percentage. Mann-Whitney U test was used to compare two independent groups and Kruskal-Wallis test was used to compare more than two independent groups. When a significant difference was found, Dunn’s test was used as a post hoc test. Chi-square test was used to investigate the relationship between categorical variables, and exact tests were used when the expected frequency percentage less than 5 was more than 20%. Pairwise ratio comparisons were made for significant relationships. Spearman correlation coefficient was used for the relationship between continuous variables. In order to find the appropriate cutoff point for the continuous variable in assignment to the risky group, the ROC curve was drawn and the area under the curve was calculated. When performing a post-hoc power analysis, the power of the study was found to be 99% based on the AUC values, given the current sample size. p < 0.05 was considered statistically significant.

Data analysis was performed using IBM Corp. Released 2013, IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp. (Free trial version)

3. Results

In our study, 2250 patients with blunt trauma were admitted to the ED, 953 of them were hospitalized with any diagnosis, and a total of 267 patients who met the inclusion criteria were included in the study (Figure 1).

Figure 1.

Patient flow chart.

The majority of the patients (76%) were male, with a mean age of 47.34 ± 20.99 years. Comorbidities were identified in 32.6% of the patients. The most common mechanism of injury was motorcycle accident (32.6%). While the proportion of patients who received blood transfusion in the first 24 hours was 25.1%, 3% of the patients needed massive blood transfusion (MBT). It was observed that 32.6% of the patients had comorbid diseases. It was determined that 64.4% of the injuries occurred at multiple anatomical sites. Surgery was required in 61.8% of patients and emergency surgery was required in 10.5%. In-hospital mortality rate was 7.1%.

At admission, the median SBP was 120 mmHg, DBP was 73 mmHg, heart rate (HR) was 90/min, blood hemoglobin (hgb) was 13.3 g/dL, and GCS mean value was 14 ± 2.76. The median length of stay in the ED was four hours, the median length of stay in intensive care unit (ICU) was one day, and the median length of total hospitalization was five days. The median value of SI was 0.74; the median value of Age SI was 32; the median value of MSI was 0.99; and the median value of ISS scores was 9.

3.1. Data of patients evaluated for blood transfusion

Patients who received blood transfusion within the first 24 hours had statistically significant differences in SBP (p < 0.001), DBP (p = 0.019), HR (p < 0.001), HGB values (p < 0.001), duration of ICU stay (p < 0.001) and hospital stay (p = 0.002) on admission compared to patients who did not receive blood transfusion. Similarly, a statistically significant correlation was found between the blood transfusion administration and the mechanism of injury (p = 0.032), need for surgery (p = 0.005), ED (p < 0.001) and hospital outcomes (p < 0.001) (Table 1).

Table 1.

Data of patients with and without need for blood transfusion in the first 24 hours.

		Blood transfusion in the first 24 hours
ItemMedian [25–75%ile values]		Absent (n = 200)	Present (n = 67)	p
Age		47 [28–64,75]	40 [27–63]	0,410
Systolic Blood Pressure (mmHg)		120 [110–136]	102 [90–120]	< 0,001
Diastolic Blood Pressure (mmHg)		73,5 [70–85]	70 [60–82]	0,019
Heart Rate (/min)		85 [80–97]	103 [94–120]	< 0,001
Glasgow Coma Scale		15 [15]	1[5 12,13,14,15]	< 0,001
Hemoglobin (g/dL)		13,65 [12,2,-14,9]	12,1 [10–14,2]	< 0,001
Length of Stay in ED (hour)		4 [3–6]	4 [3–5]	0,071
Length of Stay in ICU (day)		0 0–2]	3 [1–6]	< 0,001
Length of Hospital Stay (day)		5 [3–7]	6 [4–12]	0,002
Type of injury (n,%)	Motorcycle crash	59 (29,5%)	28 (41,8%)	0,032
	Vehicular traffic accident	41 (20,5%)	8 (11,9%)
	Pedestrian injury	18 (9%)	10 (14,9%)
	Simple fall	49 (24,5%)	7 (10,4%)
	High fall	25 (12,5%)	10 (14,9%)
	Other injuries	8 (4%)	4 (6%)
Need for surgery (n,%)	Absent	86 (43%)	16 (23,9%)	0,005
	Present	114 (57%)	51 (76,1%)
Anatomical injury site (n,%)	Multiple	125 (62,5%)	47 (70,1%)	0,098
	Limb	61 (30,5%)	17 (25,4%)
	Thorax	10 (5%)	0
	Abdomen	3 (1,5%)	1 (1,5%)
	Pelvic	1 (0,5%)	2 (3%)
ED outcome (n,%)	Hospitalization in ICU or ward	190 (95%)	49 (73,1%)	< 0,001
	Need for emergency surgery	10 (5%)	18 (26,9%)
Hospital outcome (n,%)	Survival	194 (97%)	54 (80,6%)	< 0,001
	Death	6 (3%)	13 (19,4%)

Abbreviations for Table 1: ED; Emergency department, ICU; Intensive care unit, SI; Shock index, Age SI; Age shock index, MSI; Modified shock index, ISS; Injury Severity Score.

Bold values indicate statistically significant results (p < 0.05).

When the ROC analyses of the indices in our study were compared, it was observed that all three indices could predict the need for blood transfusion in the first 24 hours. The area under the curve for SI was 0.783 (0.728–0.831 95%CI), and blood transfusion was performed in patients with a cutoff value higher than 0.933 (p < 0.001). The AUC value for MSI was 0.747 (0.690–0.798 95%CI) and blood transfusion was administered in patients with a cutoff value higher than 1.159 (p < 0.001). The AUC value for age SI was 0.641 (0.580–0.698 95%CI) and blood transfusion was administered in patients with a cutoff value higher than 30.945 (p < 0.001). The discriminative power of SI and MSI was good, while the discriminative power of Age SI was moderate and statistically significant. The area under the curve for ISS was 0.695 (0.636–0.749 95%CI) and blood transfusion was performed in patients with a cutoff value higher than 13 (p < 0.001). The discriminative power of ISS was moderate and statistically significant (Figure 2, Table 2).

Figure 2.

ROC analysis for blood transfusion administration in the first 24 hours, hospital outcome and injury severity.

Table 2.

Indices to assess clinical outcomes of patients presenting to the emergency department with blunt trauma.

	Blood transfusion in the first 24 hours
Item Median [25–75%ile values]	Absent (n = 200)	Present (n = 67)	p
SI	0,71 [0,63–0,79]	1,02 [0,78–1,22]	< 0,001
Age SI	30,23 [21,64–41,64]	36,47 [28,26–59,56]	0,001
MSI	0,95 [0,84–1,07]	1,25 [0,97–1,62]	< 0,001
ISS	9 [9–13]	14 [9–19]	< 0,001
	Surgical application		p
	Absent (n = 102)	Present (n = 165)
SI	0,73 [0,64–0,87]	0,74 [0,64–0,89]	0,897
Age SI	30,41 [22,46–42,7]	32,64 [23, 06–45,42]	0,417
MSI	0,99 [0,88–1,2]	1 [0,84–1,18]	0,737
ISS	9 [8–14]	9 [9–16]	0,064
	Hospital outcome		p
	Survival (n = 248)	Death (n = 19)
SI	0,73 [0,64–0,86]	1,18 [0,86–2]	< 0,001
Age SI	31,34 [22,65–42,17]	70,87 [34,95–94,5]	< 0,001
MSI	0,97 [0,85–1,15]	1,5 [1,34–2,45]	< 0,001
ISS	9 [9–14]	18 [14–22]	< 0,001
	Injury severity		p
	Mild-Moderate (n = 200)	Severe-Profound (n = 67)
SI	0,72 [0,63–0,83]	0,91 [0,69–1,15]	< 0,001
Age SI	32,07 [23,14–43,16]	31,5 [22,57–60,05]	0,350
MSI	0,95 [0,84–1,11]	1,18 [0,93–1,5]	< 0,001

Abbreviations for Table 2: SI; Shock index, Age SI; Age shock index, MSI; Modified shock index, ISS; Injury Severity Score.

Bold values indicate statistically significant results (p < 0.05).

3.2. Data of patients evaluated for the need for surgery

Hemoglobin values at admission (p = 0.045) and length of stay in the ED (p = 0.001) were lower in patients who needed surgery, which was statistically significant. The length of hospital stay was higher in these patients (p = 0.026). There is a statistically significant correlation between the need for surgery and anatomical site of injury (p < 0.001), and survival (p < 0.001). Patients with multiple trauma and isolated extremity injuries were more likely to need surgery. There was no significant difference between patients with and without surgical need for SI, age SI, MSI and ISS (Tables 2 and 3).

Table 3.

Data of patients with and without surgical need.

		Surgical application		p
Item Median [25–75%ile values]		Absent (n = 102)	Present (n = 165)
Age		44 [29–61,5]	46 [27–65]	0,573
Systolic Blood Pressure (mmHg)		120 [110–130]	118 [108–137]	0,859
Diastolic Blood Pressure (mmHg)		73 [65–83]	74 [65,5–85]	0,405
Heart Rate (/min)		90 80–100,25]	90 [80–101,5]	0,908
Glasgow Coma Scale		15 [15]	15 [15]	0,075
Hemoglobin (g/dL)		13,9 [12,15]	13,1 [11,65–14,45]	0,045
Length of Stay in ED (hour)		5 [3–7]	4 [3–6]	0,001
Length of Stay in ICU (day)		2 [0–3]	1 [0–4]	0,490
Length of Hospital Stay (day)		4,5 [2–7,25]	5 [3–9]	0,026
Type of injury (n,%)	Motorcycle crash	30 (29,4%)	57 (34,5%)	0,395
	Vehicular traffic accident	23 (22,5%)	26 (15,8%)
	Pedestrian injury	10 (9,8%)	18 (10,9%)
	Simple fall	17 (16,7%)	39 (23,6%)
	High fall	16 (15,7%)	19 (11,5%)
	Other injuries	6 (5,9%)	6 (3,6%)
Massive blood transfusion (n,%)	Absent	99 (97,1%)	160 (97%)	1,000
	Present	3 (2,9%)	5 (3%)
Anatomical injury site (n,%)	Multiple	88 (86,3%)	84 (50,9%)	< 0,001
	Limb	2 (2%)	76 (46,1%)
	Thorax	9 (8,8%)	1 (0,6%)
	Abdomen	2 (2%)	2 (1,2%)
	Pelvic	1 (1%)	2 (1,2%)
Hospital outcome (n,%)	Survival	93 (91,2%)	155 (93,9%)	< 0,001
	Death	9 (8,8%)	10 (6,1%)

Abbreviations for Table 3: ED; Emergency department, ICU; Intensive care unit, SI; Shock index, Age SI; Age shock index, MSI; Modified shock index, ISS; Injury Severity Score.

Bold values indicate statistically significant results (p < 0.05).

3.3. Data of patients in terms of hospital outcomes

SBP (p < 0.001), DBP (p < 0.001) and GCS (p < 0.001) were statistically significant and lower in the deceased patient group. HR (p < 0.001) and length of stay in ICU (p < 0.001) were higher in deceased patients. There was a statistically significant correlation between MBT administration and hospital outcome (p < 0.001), and the rate of death was significantly higher in patients who underwent MBT (Table 4).

Table 4.

Data of patients in terms of hospital outcomes.

		Hospital outcome		p
Item Median [25–75%ile values]		Survival (n = 248)	Death (n = 19)
Age		44 [28–63]	61 [27–81]	0,256
Systolic Blood Pressure (mmHg)		120 [110–135,75]	98 [65–108]	< 0,001
Diastolic Blood Pressure (mmHg)		75 [70–85]	60 [45–72]	< 0,001
Heart Rate (/min)		89,5 [80–100]	110 [100–128]	< 0,001
Glasgow Coma Scale		15 [15]	8 [6–15]	< 0,001
Hemoglobin (g/dL)		13,4 [12–14,68]	13,1 [9,6-14,7]	0,105
Length of Stay in ED (hour)		[4 3,4,5,6]	[3 2,3,4]	< 0,001
Length of Stay in ICU (day)		1 [0–3]	3 [2–13]	< 0,001
Length of Hospital Stay (day)		5 [3–8]	3 [2–13]	0,736
Type of injury (n,%)	Motorcycle crash	80 (32,3%)	7 (36,8%)	p = 0,827
	Vehicular traffic accident	47 (19%)	2 (10,5%)
	Pedestrian injury	25 (10,1%)	3 (15,8%)
	Simple fall	51 (20,6%)	5 (26,3%)
	High fall	33 (13,3%)	2 (10,5%)
	Other injuries	12 (4,8%)	0
Massive blood transfusion (n,%)	Absent	246 (99,2%)	13 (68,4%)	< 0,001
	Present	2 (0,8%)	6 (31,6%)

Abbreviations for Table 4: ED; Emergency department, ICU; Intensive care unit, SI; Shock index, Age SI; Age shock index, MSI; Modified shock index, ISS; Injury Severity Score.

Bold values indicate statistically significant results (p < 0.05).

The discriminative power of all three indices in terms of hospital outcome was good and statistically significant. When the indices of the deceased patients were compared; AUC for SI was 0.858 (0.810–0.897 95%CI, cutoff > 1.015, p < 0.001), AUC for Age SI was 0.807 (0.754–0.852 95%CI, cutoff > 67.065, p < 0.001), AUC for MSI was 0.869 (0.822–0.907 95%CI, cutoff value > 1.333, p < 0.001). The AUC for ISS was 0.846 (0.797–0.887 95%CI) and patients with ISS > 13 had a higher rate of death (p < 0.001) (Figure 2, Table 2).

3.4. Data of patients evaluated according to injury severity

In the group with ISS > 15 (severe and profound) injuries, SBP was lower (p = 0.003) and HR (p < 0.001), ICU (p < 0.001) and length of hospital stay (p < 0.001) were higher. The rate of blood transfusion in the first 24 hours was higher in the group with severe and profound injuries (p < 0.001). There was a statistically significant correlation between the need for emergency surgery and the severity of injury (p = 0.001) and the proportion of these patients was higher in the group with severe and profound injuries (Table 5).

Table 5.

Data of patients evaluated according to severity of injury.

		Injury severity		p
Item Median [25–75%ile values]		Mild-Moderate (n = 200)	Severe-Profound (n = 67)
Age		46,5 [31,25–67]	41 [26–57]	0,073
Systolic Blood Pressure (mmHg)		120 [110–134]	110 [98–130]	0,003
Diastolic Blood Pressure (mmHg)		73,5 [70–84]	70 [60–85]	0,103
Heart Rate (/min)		86 [80–97,75]	101 [90–113]	< 0,001
Glasgow Coma Scale		15 [15]	[[15 8,9,10,11,12,13,14,15]	< 0,001
Hemoglobin (g/dL)		13,3 11,73-[14,48]	13,8 [12-15]	0,058
Length of Stay in ED (hour)		4 [3–6]	4 [3–6]	0,537
Length of Stay in ICU (day)		0 [0–2]	4 [2–8]	< 0,001
Length of Hospital Stay (day)		4 [3-,6,75]	8 [4–13]	< 0,001
Blood transfusion in the first 24 hours (n,%)	Absent	162 (81%)	38 (56,7%)	< 0,001
	Present	38 (19%)	29 (43,3%)
Need for surgery (n,%)	Absent	79 (39,5%)	23 (34,3%)	0,451
	Present	121 (60,5%)	44 (65,7%)
ED outcome (n,%)	Hospitalization in ICU or ward	186 (93%)	53 (79,1%)	0,001
	Need for emergency surgery	14 (7%)	14 (20,9%)
Hospital outcome (n,%)	Survival	195 (97,5%)	53 (79,1%)	< 0,001
	Death	5 (2,5%)	14 (20,9%)

Abbreviations for Table 5: ED; Emergency department, ICU; Intensive care unit, SI; Shock index, Age SI; Age shock index, MSI; Modified shock index, ISS; Injury Severity Score.

Bold values indicate statistically significant results (p < 0.05).

The discriminative power of SI and MSI was moderate and statistically significant. In patients with high injury severity; AUC value for SI was 0.686 (0.606–0.767 95%CI) with a cutoff value > 0.905 (p < 0.001); while AUC value for MSI was 0.683 (0.602–0.764 95%CI) with a cutoff value > 1.181 (p < 0.001). Age SI was not statistically significant [AUC 0.538 (0.454–0.622 95%CI), with a cutoff value > 58.461] in determining injury severity (p = 0.350) (Figure 2, Table 2).

4. Discussion

Our study provides important information about shock indices in terms of predicting prognosis and intervention in blunt trauma patients.

We found that most of the patients with trauma exposure in our study were male, which is consistent with the literature [9]. Although the discriminative power of GCS was not calculated in our study, the mean value of GCS was found to be lower in deceased patients, which is consistent with the literature [10,11].

In the study by Faisal et al. it was argued that the clinically ideal SI value threshold was 1 and it was found that patients with prehospital SI > 1 had a higher need for surgery or ICU hospitalization compared to patients with prehospital SI < 1. It was observed that patients with a prehospital SI > 1 had a higher need for blood products in the first 4 hours and during the 24-hour resuscitation period, a higher length of stay in ICU units and hospitalization, and higher mortality [3].

In a study by El-Menyar et al., it was argued that when the SI cutoff value was 0.8, physicians could better recognize traumatic patients who would benefit from massive blood transfusion and early surgical intervention. In addition, it was mentioned that as SI has a good correlation with clinical markers such as pulse pressure, injury severity scores (GCS, AIS and ISS), base deficit and blood unit quantity and can be used as an independent predictor for transfusion and mortality [2]. There are also studies reporting that SI is sensitive even to small changes in circulating blood volume and is a useful index in predicting the need for intervention and massive transfusion in patients [12].

Data from the literature suggest a correlation between ISS and SI, and an increase in SI has been found to be associated with more severe injuries [13,14]. Higher SI is an indicator of higher mortality in trauma patients, and a subsequent increase in SI from the prehospital to the emergency department setting has been associated with adverse clinical outcomes [15,16]. In many studies SI have been used to predict prognosis in patients with hypovolemia, sepsis, myocardial infarction and pneumonia [17–19]. Rady et al. showed that SI was superior to traditional vital signs in predicting the need for ICU in critically ill patients with ED [20].

In our study, we found a significant correlation between SI and blood transfusion within the first 24 hours, mortality, and injury severity. These findings are consistent with the results of previously published studies. While SI demonstrated strong discriminative power for predicting early transfusion and mortality, it did not significantly predict the need for surgical intervention. This may be explained by the heterogeneity of surgical decision-making in trauma care, including both emergent and elective procedures in our study cohort. Moreover, surgical decisions are influenced not only by hemodynamic instability but also by imaging findings, injury patterns, and clinical judgment, which limits the predictive capacity of shock indices alone. Future studies may improve predictive accuracy by integrating physiological markers such as SI or MSI with anatomical scoring systems (e.g., AIS, ISS) or point-of-care imaging. Although establishing a standard cutoff value for SI remains challenging, most values in the literature range between 0.8 and 1. Our three separate analyses confirmed that SI is consistent with prior research in predicting adverse clinical outcomes.

In the study by Wang et al. investigating the accuracy of prehospital SI and MSI in predicting the need for MBT in trauma patients, it was reported that both indices showed moderate accuracy and MSI did not have a higher predictive power than SI. In terms of mortality prediction, SI and MSI showed low accuracy and no significant difference was found between them [1]. Sharma et al. found that the performance of MSI was equal to SI in predicting the need for MBT in patients with war injuries [21]. In a prospective study, MSI alone was shown to be a better predictor of mortality than HR, SBP, DBP or SI [8]. In another study comparing shock indices in sepsis patients, it was shown that MSI value higher than 1.3 was associated with many clinical outcomes including sepsis, hyperlactatemia, ICU admission and 28-day mortality [22].

In our study, the discriminative power of MSI for blood transfusion administration and mortality prediction was high, and the discriminative power for injury severity was moderate. Previous studies have also generally addressed the relationship between MSI and blood transfusion and similar findings to our study were obtained in terms of clinical outcomes. In the literature review, a standard cutoff value for MSI in terms of clinical outcomes was not determined, and it was observed that the cutoff value was 1.3 in a study [22] examining indices in septic patients. Our study demonstrated that MSI is a valuable predictor of blood transfusion and mortality in trauma patients. When compared to traditional SI, MSI provided additional value in predicting adverse clinical outcomes in patients with multiple trauma. The cutoff values we determined for MSI in our study showed results close to the literature, and it is clear that more studies should be conducted in this regard.

Zarzaur et al. found that the index they created by multiplying SI by the patient’s age, which they would later call Age SI, performed better than traditional vital signs or SI in the group over 55 years of age, significantly improved the discriminatory ability of SI by adjusting Age SI for the patient’s age because aging reduces physiologic reserve, and was a better predictor of 48-hour mortality, especially when compared with HR, SBP or SI. Although Age SI was recommended in these studies to predict the need for transfusion of 4 units or more in 48 hours, it was shown that this index performed worse than SI alone in predicting the need for transfusion, but was effective only when applied to patients over 55 years of age [23,24]. According to another study, the Age SI was able to accurately identify the most severely injured children after blunt trauma [25].

Shibahashi et al. found that the discriminatory power of SI in predicting clinical outcomes was significantly lower in elderly patients and Age SI was not found to be a reliable predictor of early mortality [26]. On the contrary, there are many studies in which age SI was found to be superior to SI and MSI in predicting adverse clinical outcomes. Lee et al. showed that age SI was superior to SI and MSI in predicting hypotension after intubation in ED [27]. Kim et al. examined geriatric trauma patients and found that the performance of age SI was better than SI and MSI in predicting in-hospital mortality [28]. Yu et al. compared these three indices in predicting mortality in patients with acute myocardial infarction and found that age SI was more significant than SI and MSI [29]. Another study comparing shock indices to determine adverse clinical outcomes in patients with gastrointestinal bleeding showed that age SI was superior to SI and MSI [30].

Although no statistically significant results were found in the comparison between age SI and surgical intervention and severity of injury, the results of our study support the studies in the literature that SI is more valuable than age SI in predicting the need for blood transfusion. Studies have shown that ISS is useful in determining hemodynamic stabilization and survival in patients when used together with SI. In our study, SI and ISS together had high values in patients who needed blood transfusion within the first 24 hours and the performance of SI was better than ISS in predicting the need for blood transfusion.

In their study, Zhu et al. showed that mortality rate was high in trauma patients who were brought to the trauma center following injury and required serious blood transfusion, and mortality tendency was higher in elderly patients and patients with blunt trauma. The high mortality rate observed despite short transport times indicates the need for early prehospital intervention [31]. In our study, a significant relationship was found between MBT application and hospital outcome. More MBT was performed in patients who died and our results are compatible with the literature.

5. Limitations

This study has several limitations. First, it was designed as a retrospective and single-center study, which may limit the generalizability of the findings. Second, prehospital interventions may have influenced initial shock index values, and decisions regarding blood transfusion and emergency surgery were based on the clinical judgment of the attending physicians, which may introduce variability. In addition, the study population was limited to adult patients with blunt trauma, and those with penetrating or mixed injury mechanisms were excluded.

Furthermore, the absence of age-stratified subgroup analyses may have restricted the ability to fully assess the prognostic value of Age SI, particularly in older individuals. Due to the retrospective nature of the study, key clinical variables such as serum lactate levels, comorbidity severity scores, and medication history (e.g., beta-blockers) were not available, which may have limited the comprehensiveness of the predictive analyses.

Considering these limitations, there is a need for larger-scale, prospective, multicenter studies that incorporate these clinical parameters and evaluate index performance across different age groups. Such studies would help validate our findings and allow for a more comprehensive assessment of the prognostic utility of shock indices in diverse patient populations and clinical settings.

6. Conclusion

SI, MSI, and age-based SI effectively predict the need for blood transfusion and mortality within the first 24 hours in blunt trauma patients admitted to the ED. SI and MSI appear to be more advantageous than age-based SI in predicting blood transfusion needs, mortality, and injury severity. MSI emerges as a more reliable predictor of clinical outcomes such as mortality compared to traditional SI, and its enhanced performance in predicting injury severity and the need for surgical intervention underscores its potential to improve patient triage and resuscitation, particularly in resource-limited settings. Therefore, we conclude that shock indices may provide valuable information during the triage and resuscitation of trauma patients, and could be particularly useful in accelerating the care of blunt trauma patients in resource-constrained environments.

Funding Statement

No funding received.

Abbreviations

SI

Shock index,

GCS

Glasgow Coma Scale,

DBP

Diastolic blood pressure,

MSI

Modified shock index,

Age SI

Age shock index,

MAP

Mean arterial pressure,

SBP

Systolic blood pressure,

ED

Emergency department,

AIS

Abbreviated injury scale,

HR

Heart rate, Hgb; Hemoglobin,

ICU

Intensive care unit,

MBT

Massive blood transfusion.

Article highlights

The Role of Shock Indices in Predicting Trauma Outcomes (Results)

SI and MSI effectively predict the need for blood transfusion and mortality in patients with blunt trauma.

SI vs. MSI in Clinical Decision-Making (Results)

MSI demonstrates superior performance compared to traditional SI in predicting mortality among blunt trauma patients and may enhance clinical decision-making processes.

Limited Predictive Value of Age-Adjusted SI (Results)

While Age SI may be beneficial in elderly populations, it shows inferior predictive capacity compared to SI and MSI in forecasting adverse clinical outcomes in blunt trauma patients.

Association Between Shock Indices and Injury Severity (Results)

SI and MSI showed a moderate correlation with injury severity, whereas Age SI did not demonstrate clinical significance in this context.

Enhanced Triage and Resuscitation in Resource-Limited Settings (Conclusion)

MSI may serve as a valuable tool for improving patient triage and resuscitation strategies, particularly in resource-constrained environments such as emergency departments.

Potential for Improved Triage at Trauma Centers (Conclusion)

Wider use and further investigation of shock indices may facilitate earlier intervention and optimal patient management in blunt trauma cases, supporting more effective triage protocols.

Author contribution

Study concept & design (OUD, AK); data acquisition (OUD, CSB, AY, SB, CÖ); data analysis (DDY), drafting and critical revision of the manuscript (CSB, AK,AY, CÖ); approval of final manuscript (all authors approved the final manuscript)

Disclosure statement

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosure

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose

Writing disclosure

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval Approval for the study was obtained from (Mersin University Clinical Research Ethics Committee dated 30 June 2020 and numbered 2020/680) and/or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved