Performance of the decarboxylation index to predict CO2 removal and minute ventilation reduction under extracorporeal respiratory support.

BACKGROUND: The aim of this study was to assess the interdependence of extracorporeal blood flow (Qec) and gas flow (GF) in predicting CO2 removal and reduction of minute mechanical ventilation under extracorporeal respiratory support. METHODS: All patients who benefited from V-V ECMO and high-flow ECCO2 R in our intensive care unit over a period of 18 months were included. CO2 removal was calculated from inlet/outlet blood port gases during the first 7 days of oxygenator use. The relationship between the Qec × GF product (named decarboxylation index and expressed in L2 /min2 ) and CO2 removal or expired minute mechanical ventilation reduction (EC MV ratio) was studied using linear regression models. RESULTS: Eighteen patients were analyzed, corresponding to 24 oxygenators and 261 datasets. CO2 removal was 393 ml/min (IQR, 310-526) for 1.8 m2 oxygenators and 179 ml/min (IQR, 165-235) for 1.3 m2 oxygenators. The decarboxylation index was associated linearly with CO2 removal (R2  = 0.62 and R2  = 0.77 for the two oxygenators, respectively) and EC MV ratio (R2  = 0.72 and R2  = 0.62, respectively). The 20L2 /min2 value (considering Qec = 2 L/min and GF = 10 L/min) was associated with an EC MV ratio between 61% and 29% for 1.8 m2 oxygenators, and between 62% and 38% for 1.3 m2 oxygenators. CONCLUSION: The decarboxylation index is a simple parameter to predict CO2 removal and EC MV ratio under extracorporeal respiratory support.

Mathematical modelling of oxygenation under veno-venous ECMO configuration using either a femoral or a bicaval drainage.

BACKGROUND: The bicaval drainage under veno-venous extracorporeal membrane oxygenation (VV ECMO) was compared in present experimental study to the inferior caval drainage in terms of systemic oxygenation. METHOD: Two mathematical models were built to simulate the inferior vena cava-to-right atrium (IVC → RA) route and the bicaval drainage-to-right atrium return (IVC + SVC → RA) route using the following parameters: cardiac output (QC), IVC flow/QC ratio, venous oxygen saturation, extracorporeal pump flow (QEC), and pulmonary shunt (PULM-Shunt) to obtain pulmonary artery oxygen saturation (SPAO2) and systemic blood oxygen saturation (SaO2). RESULTS: With the IVC → RA route, SPAO2 and SaO2 increased linearly with QEC/QC until the threshold of the IVC flow/QC ratio, beyond which the increase in SPAO2 reached a plateau. With the IVC + SVC → RA route, SPAO2 and SaO2 increased linearly with QEC/QC until 100% with QEC/QC = 1. The difference in required QEC/QC between the two routes was all the higher as SaO2 target or PULM-Shunt were high, and occurred all the earlier as PULM-Shunt were high. The required QEC between the two routes could differ from 1.0 L/min (QC = 5 L/min) to 1.5 L/min (QC = 8 L/min) for SaO2 target = 90%. Corresponding differences of QEC for SaO2 target = 94% were 4.7 L/min and 7.9 L/min, respectively. CONCLUSION: Bicaval drainage under ECMO via the IVC + SVC → RA route gave a superior systemic oxygenation performance when both QEC/QC and pulmonary shunt were high. The VV-V ECMO configuration (IVC + SVC → RA route) might be an attractive rescue strategy in case of refractory hypoxaemia under VV ECMO.

Injury characteristics, initial clinical status, and severe injuries associated with spinal fractures in a retrospective cohort of 506 trauma patients.

BACKGROUND: Our aim was to describe the characteristics of vertebral fractures, the presence of associated injuries, and clinical status within the first days in a severe trauma population. METHODS: All patients with severe trauma admitted to our level 1 trauma center between January 2015 and December 2018 with a vertebral fracture were analyzed retrospectively. The fractures were determined by the AO Spine classification as stable (A0, A1, and A2 types) or unstable (A3, A4, B, and C types). Clinical status was defined as stable, intermediate, or unstable based on clinicobiological parameters and anatomic injuries. Severe extraspinal injuries and emergent procedures were studied. Three groups were compared: stable fracture, unstable fracture, and spinal cord injury (SCI) group. RESULTS: A total of 425 patients were included (mean ± SD age, 43.8 ± 19.6 years; median Injury Severity Score, 22 [interquartile range, 17-34]; 72% male); 72 (17%) in the SCI group, 116 (27%) in the unstable fracture group, and 237 (56%) in the stable fracture group; 62% (95% confidence interval [CI], 57-67%) had not a stable clinical status on admission (unstable, 30%; intermediate, 32%), regardless of the group (p = 0.38). This decreased to 31% (95% CI, 27-35%) on day 3 and 23% (95% CI, 19-27%) on day 5, regardless of the group (p = 0.27 and p = 0.25). Progression toward stable clinical status between D1 and D5 was 63% (95% CI, 58-68%) overall but was statistically lower in the SCI group. Severe extraspinal injuries (85% [95% CI, 82-89%]) and extraspinal emergent procedures (56% [95% CI, 52-61%]) were comparable between the three groups. Only abdominal injuries and hemostatic procedures significantly differed significantly (p = 0.003 and p = 0.009). CONCLUSION: More than the half of the patients with severe trauma had altered initial clinical status or severe extraspinal injuries that were not compatible with safe early surgical management for the vertebral fracture. These observations were independent of the stability of the fracture or the presence of an SCI. LEVEL OF EVIDENCE: Prognostic and epidemiological, level III.