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.

The Frontal Bone Window for Transcranial Doppler Ultrasonography in Critically Ill Patients: Validation of a New Approach in the ICU.

BACKGROUND AND OBJECTIVE: The temporal bone window (TBW) for transcranial Doppler (TCD) often fails to insonate the anterior cerebral artery (ACA). The frontal bone window (FBW) has never been evaluated in intensive care units (ICU). The main objective was to determine the ability of the FBW to assess ACA velocities in critically ill patients. METHODS: A prospective study was conducted in two ICUs of the Montpellier University Hospital (France), between November 2014 and September 2016. Adult patients admitted to ICU for brain injury, with a Glasgow Coma Scale score ≤ 13, were enrolled within 3 days after admission. A first TCD examination was carried out bilaterally through the TBW and FBW by an intensivist expert in TCD, repeated by the same examiner, and 15 min later by an intensivist certified in TCD, designated as non-expert, blinded. The success of the FBW examinations was defined by the ability to measure the ACA velocities. Intra- and interobserver agreements were analyzed according to the Bland and Altman method. RESULTS: A total of 147 patients were analyzed. The FBW succeeded in insonating the ACA in 66 patients [45%, CI (37-53)], 45 bilaterally and 21 unilaterally. For 16 patients (11%), the FBW was the only way to measure ACA velocities. By combining the two techniques, the ACA success rate increased from 62% CI (54-70) to 73% CI (65-79) (P = 0.05). Intra- and interobserver mean biases and 95% limits of agreement for ACA systolic velocity measurements through the FBW were 1 (- 33 to 35) and 2 (- 34 to 38) cm s-1, respectively. For paired TBW and FBW measures of ACA velocities, mean biases (± SD) for ACA systolic, and mean and diastolic velocities were relatively close to zero, but negatives (- 7 ± 33, - 2 ± 19, - 1 ± 15 cm s-1, respectively), highlighting that ACA velocities were lower with the FBW (A2 segment) than TBW (A1 segment). The correlation coefficient for ACA systolic velocities measured by the FBW and TBW was R = 0.47, CI (0.28-0.62). No risk factors for failure of the FBW were identified. CONCLUSIONS: In ICU, the FBW was able to insonate the ACA in 45% of patients admitted for brain injury, without the use of contrast agents. The FBW could improve the detection of ACA vasospasms.

Cervical anaerobic vertebral osteomyelitis following surgical tracheotomy: a case report.

BACKGROUND: We report a rare case of anaerobic vertebral osteomyelitis associated with surgical tracheotomy which has never been reported to the best of our knowledge. CASE PRESENTATION: A healthy 39-year-old man was admitted to intensive care for a severe brain trauma injury where a surgical tracheotomy was performed. He was discharged to a rehabilitation centre after 54 days hospital stay. During rehabilitation, he developed progressive and febrile tetraplegia associated with cervical pain, requiring an intensive care readmission. A polymicrobial anaerobic bloodstream infection was revealed and magnetic resonance imaging diagnosed cervical vertebral osteomyelitis. Both the type of anaerobic micro-organisms found and the timing of the symptoms strongly suggest that the surgical tracheotomy was responsible for this rare case of cervical vertebral osteomyelitis. The patient was successfully treated by a prolonged antimicrobial therapy and by surgical laminectomy. CONCLUSIONS: Tracheotomy may generate anaerobic bacteraemia and related osteomyelitis in the specific setting of severe trauma patients. Clinicians should consider anaerobic vertebral osteomyelitis when they are confronted with a febrile tetraplegia after tracheotomy.

Prevalence of large and occult pneumothoraces in patients with severe blunt trauma upon hospital admission: experience of 526 cases in a French level 1 trauma center.

BACKGROUND: Occult pneumothoraces (PTXs), which are not visible on chest x-ray, may progress to tension PTX. The aim of study was to establish the prevalence of large occult PTXs upon admission of patients with severe blunt trauma, according to prehospital mechanical ventilation. METHODS: Patients with severe trauma consecutively admitted to our institution for 5 years were retrospectively analyzed. All patients with blunt thoracic trauma who had undergone computed tomographic (CT) within the first hour of hospitalization were included. Mechanical ventilation was considered as early if it was introduced in the prehospital period or on arrival at the hospital. Occult PTXs were defined as PTXs not visible on chest x-ray. All PTXs were measured on CT scan (largest thickness and vertical dimension). Large occult PTXs were defined by a largest thickness of 30 mm or more. RESULTS: Of the 526 patients studied, 395 (75%) were male, mean age was 37.9 years, mean Injury Severity Score was 22.2, and 247 (47%) received early mechanical ventilation. Of 429 diagnosed PTXs, 296 (69%) were occult. The proportion of occult PTXs classified as large was 11% (95% confidence interval, 8%-15%). The overall prevalence of large occult PTXs was 6% (95% confidence interval, 4%-8%). Both CT measurements and proportion of large occult PTXs were found statistically comparable in patients with or without mechanical ventilation. CONCLUSIONS: Six percent of studied patients with severe trauma had a large and occult PTX as soon as admission despite a normal chest x-ray result. The observed sizes and rates of occult PTX were comparable regardless of the initiation of early mechanical ventilation.

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.

Acquisition of extended-spectrum cephalosporin-resistant Gram-negative bacteria: epidemiology and risk factors in a 6-year cohort of 507 severe trauma patients.

OBJECTIVES: Severe trauma patients are at higher risk of infection and often exposed to antibiotics, which could favor acquisition of antimicrobial resistance. In this study, we aimed to assess prevalence, acquisition, and factors associated with acquisition of extended-spectrum cephalosporin-resistant Gram-negative bacteria (ESCR-GNB) in severe trauma patients. METHODS: We conducted a retrospective monocentric cohort study in a French level one Regional Trauma Centre between 01 January 2010and 31 December 2015. Patients admitted for ≥ 7 days, with an Injury Severity Score ≥ 15, and ≥ 1 microbiological sample were included in the analysis. Prevalence and acquisition rate of ESCR-GNB were determined then, factors associated with ESCR-GNB acquisition were assessed using a Cox model. RESULTS: Of 1873 patients admitted during the study period, 507 were included (median Injury Severity Score = 29 [22-34] and median intensive care unit length of stay = 16 days [10-28]). Most of them (450; 89%) had an antimicrobial therapy. Prevalence of ESCR-GNB increased from 13% to 33% during intensive care unit stay, bringing the ESCR-GNB acquisition rate to 29%. Acquisition of ESCR-GNB was mainly related to AmpC beta-lactamase Enterobacterales and was independently associated with mechanical ventilation needs (hazard ratio [HR] = 6.39; 95% confidence interval [CI] [1.51-27.17]; P = 0.01), renal replacement therapy needs (HR = 2.44; 95% CI [1.24-4.79]; P = 0.01), exposure to cephalosporins (HR = 1.06; 95% CI [1.01-1.12]; P = 0.02), and/or combination therapy with non-beta-lactam antibiotics such as vancomycin, linezolid, clindamycin, or metronidazole (HR = 1.03; 95% CI [1.01-1.06]; P = 0.02). CONCLUSIONS: Acquisition of ESCR-GNB was prevalent in severe trauma patients. Our results suggest selecting antibiotics with caution, particularly in the most severely ill.

Influence of a temporary stabilization device on respiratory status in patients with severe trauma with a femoral shaft fracture treated by damage control strategy.

BACKGROUND: There are few studies on the safety and respiratory consequences of the use of a skeletal traction (ST) device in the management of femoral shaft fractures with damage control orthopaedics (DCO) strategy, particularly in cases of prolonged use. The aim of this study was to assess the influence of ST compared with an external fixator (EF) on respiratory complications and mechanical ventilation requirements in patients with severe trauma with a femoral shaft fracture managed by DCO strategy. METHODS: We retrospectively reviewed all patients with severe trauma patients with a unilateral femoral shaft fracture admitted to our institution from 2010 to 2015. Patients who did not undergo definitive osteosynthesis during the first 24 h were included and divided into two groups: DCO-ST group and DCO-EF group. In addition to trauma severity, global management of respiratory complications, the incidence of acute respiratory distress syndrome (ARDS) and mechanical ventilation requirements and outcome were compared. RESULTS: Fifty-five patients were managed with DCO strategy (mean Injury Severity Score, 28.4); there were 31 in the DCO-ST group and 24 in the DCO-EF group. No significant difference in terms of the main characteristics, initial severity and associated injuries was observed between the two groups. In contrast, ARDS was found more frequently in the DCO-ST group (81% versus 54%; P = 0.035). Number of ventilation days also tended to be higher in the DCO-ST group (9 days [IQR 3-15 days] versus 7 [IQR 2-16 days]; P = 0.24). No difference was found for mortality and hospitalization duration between the DCO-ST and DCO-EF groups. CONCLUSION: The prolonged use of an ST device in the present cohort was associated with a higher incidence of impaired respiratory function. Therefore, our findings suggest that EF is preferable to ST in the DCO setting for femoral shaft fracture, especially in trauma patients at high risk of developing delayed respiratory failure.

Influence of late fluid management on the outcomes of severe trauma patients: A retrospective analysis of 294 severely-injured patients.

BACKGROUND: Liberal late fluid management (LFM) is associated with higher morbi-mortality in critically ill populations. The aim of the study was to assess the association between LFM and duration of mechanical ventilation in a severe trauma population. METHODS: A retrospective analysis of consecutive patients with an ISS≥16 and a length of stay in the intensive care unit (ICU)≥7 days was performed. The conservative LFM group included patients with at least 2 consecutive days with a negative fluid balance between day 3 and day 7; other patients were allocated to the liberal LFM group. RESULTS: 294 severely injured patients were included, 157 (53%) as conservative LFM and 137 (47%) as liberal LFM. The groups did not differ significantly in terms of baseline characteristics, severe injuries, severity criteria or transfusion needs. Liberal LFM was significantly associated with more ventilation days (11 vs 8.5days; P=0.02), less ventilator-free days at day 30 (19 vs 21days; P=0.03), longer ICU stay (19 vs 16days; P=0.03) and longer hospital stay (30 vs 25days; P=0.04). Mortality rates were comparable between groups (6%). Liberal LFM was significantly associated in multivariable analysis with a reduced number of ventilator-free days at day 30 (ß=-2.14 [95% CI, -4.2 to -0.08], P=0.042). CONCLUSIONS: Liberal LFM was associated with higher morbidity in severe trauma patients, longer duration of ventilation, and longer ICU and hospital stays. These results were observed despite similar severity on admission and early fluid management.

Thoracic Trauma Severity score on admission allows to determine the risk of delayed ARDS in trauma patients with pulmonary contusion.

BACKGROUND: Pulmonary contusion is a major risk factor of acute respiratory distress syndrome (ARDS) in trauma patients. As this complication may appear after a free interval of 24-48 h, detection of patients at risk is essential. The main objective of this study was to assess the performance of the Thoracic Trauma Severity (TTS) score upon admission in predicting delayed ARDS in blunt trauma patients with pulmonary contusion. METHODS: All blunt thoracic trauma patients admitted consecutively to our trauma centre between January 2005 and December 2009 were retrospectively included if they presented a pulmonary contusion on the admission chest computed tomography scan. Main outcome measure was the presence of moderate or severe ARDS (PaO2/FiO2 ratio≤200) for 48 h or more. The global ability of the TTS score to predict ARDS was studied by ROC curves with a threshold analysis using a grey zone approach. RESULTS: Of 329 patients studied (75% men, mean age 36.9 years [SD 17.8 years], mean Injury Severity Score 21.7 [SD 16.0]), 82 (25%) presented with ARDS (mean lowest PaO2/FiO2 ratio of 131 [SD 34]). The area under the ROC curves for the TTS score in predicting ARDS was 0.82 (95% CI 0.78-0.86) in the overall population. TTS scores between 8 and 12 belonged to the inconclusive grey zone. A TTS score of 13-25 was found to be independent risk factors of ARDS (OR 25.8 [95% CI 6.7-99.6] P<0.001). CONCLUSIONS: An extreme TTS score on admission accurately predicts the occurrence of delayed ARDS in blunt thoracic trauma patients affected by pulmonary contusion. This simple score could guide early decision making and management for a non-negligible proportion of this specific population.

A simple assessment of haemothoraces thickness predicts abundant transfusion: a series of 525 blunt trauma patients.

BACKGROUND: The goal of this study was to evaluate the performance of haemothorax quantification to predict an abundant transfusion in blunt thoracic trauma patients. METHODS: This study included all severe trauma patients admitted into our trauma centre from January 2005 to January 2010, who presented a blunt thoracic trauma (thoracic AIS ≥1) and had a CT scan within the first hour following admission. For each haemothorax, thickness of dominant side and the cumulated thicknesses of both sides (Dominant-t, Cumulated-t), as well as lengths (Dominant-l, Cumulated-l) and the calculated volumes (Dominant-v, Cumulated-v provided by a previously validated formula) were retrospectively measured by CT scan. A multiple logistic regression was performed to define the independent risk factors for an abundant transfusion (≥5 packed red blood cells in the first 24h). Finally, ROC curves have been drawn on an isolated thoracic trauma subgroup to predict abundant transfusion. The more specific cut-offs were extracted from this analysis. RESULTS: From the 525 blunt thoracic trauma patients (75% males, mean age 38.2 (SD18.7) years, mean ISS 22.5 (SD16.4)), 31% received an abundant transfusion. In multivariable analysis, Cumulated-t was significantly associated with an abundant transfusion (OR 1.3 [95% CI 1.1-1.4], P=0.002). In isolated thoracic trauma subgroup (n=251), the global abilities of different CT measurements to predict abundant transfusion were significantly comparable (AUCs 0.69-0.70). The more specific cut-offs were established at 28mm for Cumulated-t (specificity 92%, positive predictive value 47%) and at 24mm for Dominant-t (specificity 92%; positive predictive value 43%). CONCLUSION: The haemothorax quantification upon admission may help to predict transfusion needs. Cumulated-t was found independent risk factor for abundant transfusion in a large population of severe trauma patients. Beyond a Cumulated-t of 28mm or a Dominant-t of 24mm, abundant transfusion will be very frequently necessary. LEVEL OF EVIDENCE: Retrospective review, level III.