We aimed to examine the utility and cutoff of points for SBP and SI, as determined at the injury scene and in the ED, for predicting MT and 30-day mortality in geriatric trauma patients and patients taking antihypertensives. In geriatric trauma patients taking antihypertensives, a prehospital SBP lower than 110 mmHg was the cutoff value for the prediction of MT in multivariable logistic regression analyses. There was no significant value in multivariable logistic regression analyses of prehospital SI for predicting MT and 30-day mortality. ED SI greater than 1.0 was the cutoff value for predicting MT in patients who were older than 65 years and who were not taking antihypertensives.
The European guideline on the management of major bleeding and coagulopathy after trauma recommends that physicians clinically assess the extent of traumatic hemorrhage using a combination of patient physiology, anatomical injury pattern, mechanism of injury, and patient response to initial resuscitation. Isolated vital signs, such as HR or SBP, are unreliable in the assessment of hypovolemic shock. HR alone does not predict the need for MT [11, 22]. In contrast, SI has been shown to better risk-stratify patients for critical bleeding, increased transfusion requirements and early mortality [11, 23]. SI is an effective tool that can be implemented in a prehospital setting for the triage of geriatric trauma patients and is superior to HR and SBP for predicting mortality in geriatric trauma patients. Geriatric trauma patients with an SI of 1 or greater should be transferred to a Level 1 trauma center . Bruijns et al reported that the difference between ED and prehospital SBP, respiratory rate, and SI are good predictor of 48-hours mortality in trauma and may supplement decisions on trauma treatment . Fligor et al reported that MT in geriatric trauma patients can be reliably and simply predicted by the arrival vital signs of SBP, pulse pressure, diastolic blood pressure, and SI . Most studies have assessed predictive properties of SI for requiring at least 10 units of PRBC in the first 24 hours. It would be useful to conduct more studies evaluating the estimation and recording of the SI at earlier time-points, including the prehospital phase .
MT in older trauma patients should be considered based on anatomical factors, pre-injury anticoagulant or antiplatelet agent use, lactate level and SI even if traditional vital signs are normal . Studies have suggested that advanced age and the presence of comorbidities such as hypertension, diabetes, use of anticoagulation medications can affect the prognosis of trauma patients based on SBP and SI, and therefore the cutoff value should be different. Kristensen et al reported that SI is independently associated with 30-day mortality in a broad population of ED patients, and an SI of 1 or more is associated with an adjusted OR of 10.5 (95% CI, 9.3–11.7) for 30-day mortality. However, age, hypertension, and β- or calcium channel blockers weaken the association between SI and mortality . Additionally, Brown et al  noted that formally substituting an SBP of less than 110 mmHg for the current SBP of less than 90 mmHg is beneficial in geriatric patients and may be potentially valuable in all adult patients at field triage. Geriatric patients with SBP of 90 to 109 mmHg had odds of mortality similar to those of geriatric patients with SBP of less than 90 mmHg . SBP of less than 110 might represent shock in patients older than 65 years .
Prehospital trauma triage ensures proper transport of patients at risk of severe injury to hospitals with an appropriate level of trauma care. Incorrect triage results in under-triage and over-triage . According to the National Trauma Triage Protocol guideline , GCS, SBP and respiratory rate are involved in Step 1 of field triage. Next, the anatomy of injury is considered in Step 2; the mechanism of injury is considered in Step 3; and older age, anticoagulant use, and bleeding disorders are considered in Step 4. Studies of trauma patients have suggested an upward review of the SBP cutoff value to less than 90 mmHg in elderly patients older than 65 years [8, 16, 27]. The above are reflected in the National Trauma Triage Protocol guideline in Step 4, and the presence or absence of antihypertensive use is not considered. Based on this and other studies, it is advisable to include antihypertensive use as a consideration in field triage and to consider it at an earlier stage along with older age . For example, we recommend that “SBP < 110 might represent shock after age 65 years” is eliminated on Step 4 and “SBP < 110 might represent shock after age 65 years taking antihypertensives” is added on Step 2.
SBP, HR and SI, the main analysis variables we used, are continuous variables, and some results may be different depending on the interval classification method. When they were used as a continuous variable instead of an interval for MT prediction, SI at ED arrival [odds ratio 257 (95% CI 8.36–791) in elderly patients taking antihypertensives, odds ratio 20.9 (95% CI 4.04–108) in elderly patients not taking antihypertensives] was analyzed as a statistically significant factor along with ISS and RTS. However, in this case, the influence of SI unit, which is a variable smaller than SBP unit, increase in the unit and interval characteristics of the continuous variable seen in regression analysis. So unit correction is required. And we assumed that presenting the cut-off value is familiar to clinician and more useful for interpretation.
We analyzed both the patients’ medical history and prehospital vital signs and indicators, which were not fully covered in previous studies, and performed multivariable logistic regression analysis including in-hospital mortality and MT. In addition, we were able to present a more accurate understanding of the underlying condition and flexible cutoff by stratifying the associations of vital signs and SI on clinical prognosis according to age and whether the patient was taking antihypertensives. In the group of patients who were younger than 65 years and not taking antihypertensives, RTS, ISS and ED SI were strongly associated with prediction of MT. Prehospital SBP was the only significant predicting factor in elderly trauma patients taking antihypertensives. However, SI measured at the time of ED admission and RTS were significant in the elderly patients who were not taking antihypertensives. These results could suggest that the uncritical application by cutoff values of SI and SBP in any aged trauma patients is inaccurate.
Our study had several limitations. Because this was an observational study, there was a potential selection bias from excluding many patients who were missing or did not have SBP and HR measured in the emergency medical services setting (n = 898, Fig. 1). These were 684 patients not transported by EMS or direct visits (including patients under the age of 14), 269 patients under the age of 14, and 26 cases of refusal to measure vital sign because of self-harm, etc. Instead, their ED vital signs are all recorded (95% CI of ED SBP 120-156 mmHg, ED HR 74-98 bpm). Second, these contradictory results included a potential bias in that no transfusion was recorded if a patient died before receiving a transfusion, despite being a severe trauma patient requiring transfusion. Therefore, although MT is the main interest, we also studied the 30-day-mortality as a primary outcome. Finally, we did not exclude traumatic brain injury, which may confound the data due to the classic Cushing reflex whereby SBP increases and HR decreases. However, the predictive effect of SI and SBP was not changed in the primary outcome for the remaining 1853 patients excluding 96 severe traumatic brain injury (TBI) patients.