Transportability Assessment Scale (TAS) and transportation associated mortality (TAS–mortality) critical patients and patients with emergency-related injuries

Abstract

Relevance. The existing traditional tools (scales) to assess severity of the patient’s condition and death probability do not take into account a set of crucial parameters for the upcoming medical evacuation.The objective is to develop the Transportability Assessment Scale (TAS) and transportability-associated mortality (TAS-mortality) tool to evaluate critical patients and patients injured in emergency situations (ES) of all age groups at different stages of medical evacuation using all types of transportation, followed by inpatient treatment.Methods. In total, we analyzed N=217 clinical cases of medical evacuation using different types of transportation in combination with either traditional intensive care (n=149, control group) or ECMO (n=68, trial group) due to refractory respiratory and/or circulatory insufficiency in all age groups. Once the patients embarked on medical evacuation, they were immediately split in groups to assess their condition while transportation and within the next 72 hours (associated period). A new scale (formula) to assess patient’s transportability and probability of mortality, including in the ECMO setting, was formulated based on the following statistical techniques: one-factor forecasting, risk classes of disorder development and logistic regression modeling applied to such target indicators as “death”, “transportation negative impact on patient’s condition” and other factors. Most significant factors were further embedded in the new transportability and probability of death assessment scale (formula).Results and discussion. The Transportability Assessment Scale (TAS) was developed using logistic regression model measuring the impact of transportation on the patient’s condition: y = exp(37∙ x1 + 6∙ x2 + 20∙ x3 +16∙ x4 + 21∙ x5 + 27∙ x6 – 27∙ x7) / 1+ exp(37∙ x1 + 6∙ x2 + 20∙ x3 +16∙ x4 + 21∙ x5 + 27∙ x6 – 27∙ x7), where: у – transportability assessment of patient; x1 (PaO2/FiO2 ≤ 110); x2 (Age ≥ 65 years); x3 (VIS ≥ 4 points); x4 (PaCO2 ≥ 55 mm Hg); x5 (SvO2 ≤ 60 %); x6 (HR∙ ≥ 127 beats per minute); x7 (ECMO application). Depending on the evacuation conditions, correction factors were as follows: x1 – 0.75 if the patient is to be transported by plane, x6 – 0.65 if the patient’s body weight is less than 10 kg. The results were translated into a 100-point scoring system: patients scoring up to 30 points were available for evacuation; 30 to 70 indicated evacuation to be performed in ongoing intensive care setting; over 70 indicated impossibility of evacuation until the patient is stabilized and subcompensated. We also developed the new TAS-mortality 100-point scale: y = exp(29∙ x1 + 16∙ x2 + 11∙ x3 + 10∙ x4 + 9∙ x5 + 7∙ x6 + 7∙ x7 + 6∙ x8 + 4∙ x9 + 1∙ x10,) / 1+ exp(29∙ x1 + 16∙ x2 + 11∙ x3 + 10∙ x4 + 9∙ x5 + 7∙ x6 + 7∙ x7 + 6∙ x8 + 4∙ x9 + 1∙ x10), where: y – probability of outcome – death; x1 (lactate ≥ 8 mmol/L), x2 (age ≥ 65 лет), x3 (creatinine ≥ 300 µmol/L), x4 (duration of mechanical ventilation ≥ 7 days), x5 (bilirubin ≥ 102 µmol/L), x6 (PaO2/FiO2 ≤ 110), x7 (CPR), F8 (VIS ≥ 4 points), x9 (PaCO2 ≥ 70 mm Hg), x10 (SvO2 ≤ 50 %). TAS-mortality scale complemented by the ROC analysis program (AuROC = 0.83; p < 0.001), showed higher sensitivity, specificity and efficacy in comparison with traditional scales APACHE-IV & Mortality Rate, SOFA & Mortality Rate, Scale of Assessment of Vital System (ShOVS).Conclusion. The proposed Transportability Assessment Scale (TAS) and transportation associated mortality (TAS-Mortality) scale have better sensitivity, efficiency and ROC-curve than traditional scales, and therefore could be actively recommended to describe the state of emergency victims or critical patients of all age categories, as well as to make decisions regarding medical evacuation, including ECMO and medical jets.