Date Published: April 25, 2019
Publisher: Public Library of Science
Author(s): Shao-Chun Wu, Cheng-Shyuan Rau, Spencer C. H. Kuo, Shiun-Yuan Hsu, Hsiao-Yun Hsieh, Ching-Hua Hsieh, Wisit Cheungpasitporn.
The shock index (SI) is defined as the ratio of heart rate/systolic blood pressure. This study aimed to determine the performance of delta shock index (ΔSI), a difference between SI upon arrival at the emergency room (ER) and that in the field, in predicting the need for massive transfusion (MT) among adult trauma patients with stable blood pressure.
This study included registered data from all trauma patients aged 20 years and above who were hospitalized from January 1, 2009 to December 31, 2016. Only patients who were transferred by emergency medical service from the accident site with a systolic blood pressure ≥ 90 mm Hg at the ER were included. The 7,957 enrolled trauma patients were divided into 2 groups, those who had received blood transfusion ≥ 10 U (MT, n = 82) and those who had not (non-MT, n = 7,875). The odds ratios with 95% confidence intervals for the need for MT by a given ΔSI were measured. The plot of specific receiver operating characteristic (ROC) curves was used to evaluate the best cutoff point of ΔSI that could predict the patient’s probability of receiving MT.
ROC curve analysis showed that a ΔSI of 0.06 as the cutoff point had the highest AUC of 0.61, with a sensitivity of 0.415 and specificity of 0.841. Patients with a ΔSI ≥ 0.00 had a significant 1.8-fold increase in need for MT than those patients with a ΔSI less than 0.00 (1.4% vs. 0.8%, p = 0.01). The larger the ΔSI, the higher the odds of need for an MT. Using the cutoff point of ΔSI of 0.06, patients with a ΔSI ≥ 0.06 had a significant 3.7-fold increase in need for MT than those patients with a ΔSI less than 0.06 (2.7% vs. 0.7%, p < 0.001). This study indicated that, in trauma patients with stable blood pressure at the ER, the accuracy of prediction of the requirement for MT by ΔSI is low. However, the size of the delta is significantly associated with need for MT and a lack of improvement in the patient’s SI at the ER compared to that in the field significantly increases the odds of a need for MT.
Massive transfusion (MT) in trauma is defined as the transfusion of ten or more units of whole blood or packed red blood cells within the first twenty-four hours of arrival to the hospital . Early recognition of the need for MT is important but still presents a challenge in trauma patients. Vital signs alone have proven insufficient in reliably predicting need for MT [2, 3]. The shock index (SI), the ratio of heart rate (HR)/ systolic blood pressure (SBP), has been considered as a marker for significant injury in trauma patients with hypovolemic shock , requirement for transfusion , and need for MT [3, 6, 7]. The dynamic change in the ratio of HR to SBP reflect the physiological response of an individual to the trauma injury [8–12]. Previous work has shown that SI is moderately accurate in predicting the need for MT. An SI ≥ 0.95 predict the need for MT with an AUC of 0.760 (sensitivity, 0.563, and specificity, 0.876) .
This study revealed that the accuracy with which the ΔSI predicted a requirement for MT was not satisfactory. However, it is noted that patients had a significant higher need for MT when the patients had a ΔSI ≥ 0.00 and, as the ΔSI increased, the odds of a need for MT in patients with ΔSI ≥ a given value significantly increased. This result may also imply that an increase in HR under same value of SBP of the patients suggests a higher odd of need for MT. In this study, a higher SI at the ER compared to the SI in the field significantly increased the odds of a need for MT. In addition, the size of the delta is significantly associated with need for MT. The larger the gap between the SI at the ER and that in the field, the higher the odds of need for MT.
This study indicated that, in trauma patients with stable blood pressure at the ER, the accuracy of prediction of the requirement for MT by ΔSI is low. However, the size of the delta is significantly associated with need for MT and a lack of improvement in the patient’s SI at the ER compared to that in the field significantly increases the odds of a need for MT.