Li and colleagues note that SI may vary with time and changing medical condition; therefore, a single SI may not accurately reflect a patient’s condition. We fully agree that a single SI represents only a ‘snapshot’ depending partly on actual treatment. However, previous independent reports have demonstrated that SI correlated best with the transfusion of ≥4 blood units within the first 48 hours after hospital admission [5, 6] and that patients with a SI between 0.7 and 0.9 had a two-fold increased risk for massive transfusion . Li and colleagues further criticize that SI may lead to an undertriage of patients and cite a corresponding study . In this study, however, the low sensitivity of the SI was observed only in healthy individuals with low tolerance to artificial progressive lower-body negative-pressure. The mortality and multi-organ failure/sepsis rates in our ‘no shock’ group may be attributable to initial trauma load (Injury Severity Score group I 19.3 (±12.0)), including relevant (Abbreviated Injury Scale ≥3) brain (45.9%) and thoracic injuries (36.1%). Lastly, Li and colleagues criticize that SI may not be accurate in the elderly. The cited study, however, suggests that the number of blood products transfused in patients aged between 16 and 80 years correlates significantly with the SI . The authors acknowledge that SI is inferior to direct perfusion measurements and should not be used inconsiderately in clinical routine. However, SI may serve as a fast and easy alternative to assess the extent of hypovolemia in trauma patients when advanced technology is unavailable.