High positive end-expiratory pressure ventilation mitigates the progression from unilateral pulmonary contusion to ARDS: An animal study.

BACKGROUND: Pulmonary contusion (PC) is common in severely traumatized patients and can lead to respiratory failure requiring mechanical ventilation (MV). Ventilator-induced lung injury (VILI) might aggravate lung damage. Despite underrepresentation of trauma patients in trials on lung-protective MV, results are extrapolated to these patients, potentially disregarding important pathophysiological differences. METHODS: Three MV protocols with different positive end-expiratory pressure (PEEP) levels: ARDSnetwork lower PEEP (ARDSnet-low), ARDSnetwork higher PEEP (ARDSnet-high), and open lung concept (OLC) were applied in swine for 24 hours following PC. Gas exchange, lung mechanics, quantitative computed tomography, and diffuse alveolar damage (DAD) score were analyzed. Results are given as median (interquartile range) at 24 hours. Statistical testing was performed using general linear models (group effect) over all measurement points and pairwise Mann-Whitney U tests for DAD. RESULTS: There were significant differences between groups: PEEP ( p < 0.0001) ARDSnet-low (8 [8-10] cmH 2 O), ARDSnet-high (12 [12-12] cmH 2 O), OLC (21 [20-22] cmH 2 O). The fraction of arterial partial pressure of oxygen and inspired oxygen fraction ( p = 0.0016) was lowest in ARDSnet-low (78 (73-111) mm Hg) compared with ARDSnet-high (375 (365-423) mm Hg) and OLC (499 (430-523) mm Hg). The end-expiratory lung volume (EELV) differed significantly ( p < 0.0001), with highest values in OLC (64% [60-70%]) and lowest in ARDSnet-low (34% [24-37%]). Costa's surrogate for mechanical power differed significantly ( p < 0.0001), with lowest values for ARDSnet-high (73 [58-76]) compared with OLC (105 [108-116]). Diffuse alveolar damage was lower in ARDSnet-high compared with ARDSnet-low (0.0007). CONCLUSION: Progression to ARDS, 24 hours after PC, was mitigated by OLC and ARDSnet-high. Both concepts restored EELV. ARDSnet-high had the lowest mechanical power surrogate and DAD. Our data suggest, that ARDSnet-high restored oxygenation and functional lung volume and reduced physiological and histological surrogates for VILI. ARDSnet-low generated unfavorable outcomes, such as loss of EELV, increased mechanical power and DAD after PC in swine. The high respiratory rate in the OLC may blunt favorable effects of lung recruitment.

Bedside estimation of nonaerated lung tissue using blood gas analysis.

OBJECTIVES: Studies correlating the arterial partial pressure of oxygen to the fraction of nonaerated lung assessed by CT shunt yielded inconsistent results. We systematically analyzed this relationship and scrutinized key methodological factors that may compromise it. We hypothesized that both physiological shunt and the ratio between PaO2 and the fraction of inspired oxygen enable estimation of CT shunt at the bedside. DESIGN: : Prospective observational clinical and laboratory animal investigations. SETTING: ICUs (University Hospital Leipzig, Germany) and Experimental Pulmonology Laboratory (University of São Paulo, Brazil). PATIENTS, SUBJECTS AND INTERVENTIONS: Whole-lung CT and arterial blood gases were acquired simultaneously in 77 patients mechanically ventilated with pure oxygen. A subgroup of 28 patients was submitted to different Fio2. We also studied 19 patients who underwent repeat CT. Furthermore we studied ten pigs with acute lung injury at multiple airway pressures, as well as a theoretical model relating PaO2 and physiological shunt. We logarithmically transformed the PaO2/Fio2 to change this nonlinear relationship into a linear regression problem. MEASUREMENTS AND MAIN RESULTS: We observed strong linear correlations between Riley's approximation of physiological shunt and CT shunt (R = 0.84) and between logarithmically transformed PaO2/Fio2 and CT shunt (R = 0.86), allowing us to construct a look-up table with prediction intervals. Strong linear correlations were also demonstrated within-patients (R = 0.95). Correlations were significantly improved by the following methodological issues: measurement of PaO2/Fio2 during pure oxygen ventilation, use of logarithmically transformed PaO2/Fio2 instead of the "raw" PaO2/Fio2, quantification of nonaerated lung as percentage of total lung mass and definition of nonaerated lung by the [-200 to +100] Hounsfield Units interval, which includes shunting units within less opacified lung regions. CONCLUSION: During pure oxygen ventilation, logarithmically transformed PaO2/Fio2 allows estimation of CT shunt and its changes in patients during systemic inflammation. Relevant intrapulmonary shunting seems to occur in lung regions with CT numbers between [-200 and +100] Hounsfield Units.

Hemoadsorption in the critically ill-Final results of the International CytoSorb Registry.

The aim of the current paper is to summarize the results of the International CytoSorb Registry. Data were collected on patients of the intensive care unit. The primary endpoint was actual in-hospital mortality compared to the mortality predicted by APACHE II score. The main secondary endpoints were SOFA scores, inflammatory biomarkers and overall evaluation of the general condition. 1434 patients were enrolled. Indications for hemoadsorption were sepsis/septic shock (N = 936); cardiac surgery perioperatively (N = 172); cardiac surgery postoperatively (N = 67) and "other" reasons (N = 259). APACHE-II-predicted mortality was 62.0±24.8%, whereas observed hospital mortality was 50.1%. Overall SOFA scores did not change but cardiovascular and pulmonary SOFA scores decreased by 0.4 [-0.5;-0.3] and -0.2 [-0.3;-0.2] points, respectively. Serum procalcitonin and C-reactive protein levels showed significant reduction: -15.4 [-19.6;-11.17] ng/mL; -17,52 [-70;44] mg/L, respectively. In the septic cohort PCT and IL-6 also showed significant reduction: -18.2 [-23.6;-12.8] ng/mL; -2.6 [-3.0;-2.2] pg/mL, respectively. Evaluation of the overall effect: minimal improvement (22%), much improvement (22%) and very much improvement (10%), no change observed (30%) and deterioration (4%). There was no significant difference in the primary outcome of mortality, but there were improvements in cardiovascular and pulmonary SOFA scores and a reduction in PCT, CRP and IL-6 levels. Trial registration: ClinicalTrials.gov Identifier: NCT02312024 (retrospectively registered).

Computed tomographic assessment of lung weights in trauma patients with early posttraumatic lung dysfunction.

INTRODUCTION: Quantitative computed tomography (qCT)-based assessment of total lung weight (Mlung) has the potential to differentiate atelectasis from consolidation and could thus provide valuable information for managing trauma patients fulfilling commonly used criteria for acute lung injury (ALI). We hypothesized that qCT would identify atelectasis as a frequent mimic of early posttraumatic ALI. METHODS: In this prospective observational study, Mlung was calculated by qCT in 78 mechanically ventilated trauma patients fulfilling the ALI criteria at admission. A reference interval for Mlung was derived from 74 trauma patients with morphologically and functionally normal lungs (reference). Results are given as medians with interquartile ranges. RESULTS: The ratio of arterial partial pressure of oxygen to the fraction of inspired oxygen was 560 (506 to 616) mmHg in reference patients and 169 (95 to 240) mmHg in ALI patients. The median reference Mlung value was 885 (771 to 973) g, and the reference interval for Mlung was 584 to 1164 g, which matched that of previous reports. Despite the significantly greater median Mlung value (1088 (862 to 1,342) g) in the ALI group, 46 (59%) ALI patients had Mlung values within the reference interval and thus most likely had atelectasis. In only 17 patients (22%), Mlung was increased to the range previously reported for ALI patients and compatible with lung consolidation. Statistically significant differences between atelectasis and consolidation patients were found for age, Lung Injury Score, Glasgow Coma Scale score, total lung volume, mass of the nonaerated lung compartment, ventilator-free days and intensive care unit-free days. CONCLUSIONS: Atelectasis is a frequent cause of early posttraumatic lung dysfunction. Differentiation between atelectasis and consolidation from other causes of lung damage by using qCT may help to identify patients who could benefit from management strategies such as damage control surgery and lung-protective mechanical ventilation that focus on the prevention of pulmonary complications.

Detection of posttraumatic pneumothorax using electrical impedance tomography-An observer-blinded study in pigs with blunt chest trauma.

INTRODUCTION: Posttraumatic pneumothorax (PTX) is often overseen in anteroposterior chest X-ray. Chest sonography and Electrical Impedance Tomography (EIT) can both be used at the bedside and may provide complementary information. We evaluated the performance of EIT for diagnosing posttraumatic PTX in a pig model. METHODS: This study used images from an existing database of images acquired from 17 mechanically ventilated pigs, which had sustained standardized blunt chest trauma and had undergone repeated thoracic CT and EIT. 100 corresponding EIT/CT datasets were randomly chosen from the database and anonymized. Two independent and blinded observers analyzed the EIT data for presence and location of PTX. Analysis of the corresponding CTs by a radiologist served as reference. RESULTS: 87/100 cases had at least one PTX detected by CT. Fourty-two cases showed a PTX > 20% of the sternovertebral diameter (PTXtrans20), whereas 52/100 PTX showed a PTX>3 cm in the craniocaudal diameter (PTXcc3), with 20 cases showing both a PTXtranscc and a PTXcc3. We found a very low agreement between both EIT observers considering the classification overall PTX/noPTX (κ = 0.09, p = 0.183). For PTXtrans20, sensitivity was 59% for observer 1 and 17% for observer 2, with a specificity of 48% and 50%, respectively. For PTXcc3, observer 1 showed a sensitivity of 60% with a specificity of 51% while the sensitivity of observer 2 was 17%, with a specificity of 89%. By programming a semi-automatized detection algorithm, we significantly improved the detection rate of PTXcc3, with a sensitivity of 73% and a specificity of 70%. However, detection of PTXtranscc was not improved. CONCLUSION: In our analysis, visual interpretation of EIT without specific image processing or comparison with baseline data did not allow clinically useful diagnosis of posttraumatic PTX. Multimodal imaging approaches, technical improvements and image postprocessing algorithms might improve the performance of EIT for diagnosing PTX in the future.

Image reconstruction affects computer tomographic assessment of lung hyperinflation.

OBJECTIVES: Lung hyperinflation may be assessed by computed tomography (CT). As shown for patients with emphysema, however, CT image reconstruction affects quantification of hyperinflation. We studied the impact of reconstruction parameters on hyperinflation measurements in mechanically ventilated (MV) patients. DESIGN: Observational analysis. SETTING: A University hospital-affiliated research Unit. PATIENTS: The patients were MV patients with injured (n = 5) or normal lungs (n = 6), and spontaneously breathing patients (n = 5). INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Eight image series involving 3, 5, 7, and 10 mm slices and standard and sharp filters were reconstructed from identical CT raw data. Hyperinflated (V(hyper)), normally (V(normal)), poorly (V(poor)), and nonaerated (V(non)) volumes were calculated by densitometry as percentage of total lung volume (V(total)). V(hyper) obtained with the sharp filter systematically exceeded that with the standard filter showing a median (interquartile range) increment of 138 (62-272) ml corresponding to approximately 4% of V(total). In contrast, sharp filtering minimally affected the other subvolumes (V(normal), V(poor), V(non), and V(total)). Decreasing slice thickness also increased V(hyper) significantly. When changing from 10 to 3 mm thickness, V(hyper) increased by a median value of 107 (49-252) ml in parallel with a small and inconsistent increment in V(non) of 12 (7-16) ml. CONCLUSIONS: Reconstruction parameters significantly affect quantitative CT assessment of V(hyper) in MV patients. Our observations suggest that sharp filters are inappropriate for this purpose. Thin slices combined with standard filters and more appropriate thresholds (e.g., -950 HU in normal lungs) might improve the detection of V(hyper). Different studies on V(hyper) can only be compared if identical reconstruction parameters were used.

Complications and adverse effects associated with continuous peripheral nerve blocks in orthopedic patients.

BACKGROUND: The increasing popularity of continuous peripheral nerve blocks (CPNBs) warrants further study of their adverse effects and complications. METHODS: Anterior sciatic, femoral, and interscalene brachial plexus CPNBs were performed preoperatively using standardized catheter techniques in orthopedic patients prior to general or spinal anesthesia. Complications and adverse effects related to CPNBs were prospectively evaluated. RESULTS: We analyzed 1398 CPNBs in 849 consecutive patients (mean age 65 +/- 13 yr) between 2002 and 2004. Two-hundred-twenty-one patients received interscalene, 628 patients femoral, and 549 sciatic CPNBs, respectively. In all the latter patients, we performed both femoral and sciatic CPNBs. Overall, there were 9 cases of local inflammation at the insertion site (0.6%), and 3 local infections (pustule) (0.2%, all femoral CPNBs). In one patient undergoing a femoral technique, a retroperitoneal hematoma led to compression injury of the femoral nerve. Complete denervation of the quadriceps femoris muscle was confirmed by electroneuromyography. No other major neurological complications were noted. There was one case of methemoglobinemia associated with an interscalene CPNB. Vascular puncture occurred in approximately 6% of patients undergoing femoral and sciatic CPNBs. Catheter rupture was noted in one patient. CONCLUSIONS: Our results add to the evidence that major complications from CPNBs are rare. However, minor adverse effects associated with CPNBs may be more common.

[Fulminant MH crisis during the ninth general anaesthesia]. / Kasuistik: Fulminante Maligne Hyperthermie - Untypischer Verlauf während der 9. Allgemeinanästhesie.

Malignant hyperthermia (MH) is a rare, often life-threatening complication of general anaesthesia. The timely diagnosis of an MH crisis in onset, as a prerequisite for successful therapy, can be difficult for the anaesthetist because of the few and non-specific early symptoms. This is even more so in patients in whom anaesthesia with MH trigger substances has already been performed in the past without any particular complications so leading to a false sense of security with regard to MH sensitivity. The case presented is a healthy young man with a congenital cleft lip, jaw and palette who developed a fulminant MH crisis during his ninth general anaesthesia. Post-operative research into the course of the previous anaesthesias revealed signs of MH crises which however proceeded abortively and were therefore unnoticed. In the case presented, the diagnosis was additionally complicated by the untypical course of the early symptoms. Tachycardia which in 80 % of cases is described as the first symptom of an MH crisis in onset, was at first completely absent and was only moderately pronounced in the full clinical picture of MH. On the other hand, a steady increase in body temperature, a cardinal symptom which usually appears later, was registered early. The suspected diagnosis of MH was then finally confirmed in the fourth hour after start of anaesthesia on the basis of the repeatedly increased end expiratory CO(2) levels. These could not otherwise be explained although several respiratory corrections were performed. Despite immediate MH specific therapy, the crisis developed in the following hour into the full clinical picture: maximum temperature of 41.4 degrees C, end expiratory CO(2) 100mm Hg, consumptive coagulopathy, acute renal failure and shock (systolic blood pressure < 50mm Hg, heart rate 115/minute). After 2 hours of specific intensive therapy, the patient was finally stabilized and transfer to the intensive care unit was possible. 24 hours after the event, the patient was could be extubated without any complications and 2 days later, he was transferred to the normal ward. The intra-operative diagnosis of MH was confirmed 3 days later by means of genetic analysis. Two mutations of the RYR1 gene were identified.

Early recovery from post-traumatic acute respiratory distress syndrome.

BACKGROUND: To present and discuss the rationale and possible benefits of timely alveolar recruitment in early post-traumatic acute respiratory distress syndrome. METHODS: A 17-year-old patient who had sustained blunt thoracic trauma presented with severe hypoxaemia on admission and whole body computed tomography showed pulmonary contusion and substantial bilateral atelectasis. Oxygenation and lung mechanics did not improve with low tidal volume ventilation using high positive end-expiratory pressures (PEEPs). Therefore we applied an alveolar recruitment manoeuvre 7 h after admission. After alveolar recruitment, PEEP was titrated to the lowest level which prevented alveolar derecruitment. RESULTS: Oxygenation and lung compliance improved rapidly and aeration of the entire lung was confirmed by computed tomography 27 h after the recruitment manoeuvre. The patient recovered completely and was discharged after 17 days. CONCLUSION: Although robust evidence is still lacking, several lines of evidence suggest potential benefits of timely alveolar recruitment. Patients with early post-traumatic respiratory failure seem to most readily respond to alveolar recruitment manoeuvres and could thus benefit from the gain in functional lung volume and oxygenation. Moreover the probability of ventilator associated complications may be reduced.