[Prehospital ultrasound in emergency medicine]. / Prähospitaler Ultraschall in der Notfallmedizin.

Small, portable hand-held ultrasound devices nowadays enable a widespread use of prehospital point-of-care ultrasound (pPOCUS), which has so far only been used hesitantly, especially in ground-based emergency services. Many critical or even life-threatening conditions or internal injuries can often be better diagnosed or ruled out using pPOCUS, which can enable faster and more suitable goal-directed treatment and hospital transport. This article critically discusses relevant data, clinical benefits, limitations and challenges to be overcome when using pPOCUS for the most important life-threatening situations and aims to call for intensifying training and the extensive use of pPOCUS.

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.

Automated 3D thorax model generation using handheld video-footage.

PURPOSE: For the visualization of pulmonary ventilation with Electrical Impedance Tomography (EIT) most devices use standard reconstruction models, featuring common thorax dimensions and predetermined electrode locations. Any discrepancies between the available model and the patient in terms of body shape and electrode position lead to incorrectly displayed impedance distributions. This work addresses that problem by presenting and evaluating a method for 3D model generation of the thorax and any affixed electrodes based on handheld video-footage. METHODS: Therefore, a process was developed, providing users with the ability to capture a patient's chest and the attached electrodes via smartphone. Once data is collected, extracted images are used to generate a 3D model with a structure from motion approach and locate electrodes with ArUco markers. For the evaluation of the developed method, multiple tests were performed in laboratory environments, which were compared with manually created reference models and differences quantified based on mean distance, standard deviation, and maximum distance. RESULTS: The implemented workflow allows for automated model reconstruction based on videos or selected images captured with a handheld device. It generates sparse point clouds from which a surface mesh is reconstructed and returns relative coordinates of any identified ArUco marker. The average value for the mean distance error of two model generations was 5.4 mm while the mean standard deviation was 6.0 mm. The average runtime of twelve reconstructions was 5:17 min, with a minimal runtime of 3:22 min and a maximal runtime of 7:29 min. CONCLUSION: The presented methods and results show that model reconstruction of a patient's thorax and applied electrodes at an emergency site is feasible with already available devices. This is a first step toward the automated generation of patient-specific reconstruction models for Electrical Impedance Tomography based on images recorded with handheld devices.

Individualized versus Fixed Positive End-expiratory Pressure for Intraoperative Mechanical Ventilation in Obese Patients: A Secondary Analysis.

BACKGROUND: General anesthesia may cause atelectasis and deterioration in oxygenation in obese patients. The authors hypothesized that individualized positive end-expiratory pressure (PEEP) improves intraoperative oxygenation and ventilation distribution compared to fixed PEEP. METHODS: This secondary analysis included all obese patients recruited at University Hospital of Leipzig from the multicenter Protective Intraoperative Ventilation with Higher versus Lower Levels of Positive End-Expiratory Pressure in Obese Patients (PROBESE) trial (n = 42) and likewise all obese patients from a local single-center trial (n = 54). Inclusion criteria for both trials were elective laparoscopic abdominal surgery, body mass index greater than or equal to 35 kg/m2, and Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) score greater than or equal to 26. Patients were randomized to PEEP of 4 cm H2O (n = 19) or a recruitment maneuver followed by PEEP of 12 cm H2O (n = 21) in the PROBESE study. In the single-center study, they were randomized to PEEP of 5 cm H2O (n = 25) or a recruitment maneuver followed by individualized PEEP (n = 25) determined by electrical impedance tomography. Primary endpoint was Pao2/inspiratory oxygen fraction before extubation and secondary endpoints included intraoperative tidal volume distribution to dependent lung and driving pressure. RESULTS: Ninety patients were evaluated in three groups after combining the two lower PEEP groups. Median individualized PEEP was 18 (interquartile range, 16 to 22; range, 10 to 26) cm H2O. Pao2/inspiratory oxygen fraction before extubation was 515 (individual PEEP), 370 (fixed PEEP of 12 cm H2O), and 305 (fixed PEEP of 4 to 5 cm H2O) mmHg (difference to individualized PEEP, 145; 95% CI, 91 to 200; P < 0.001 for fixed PEEP of 12 cm H2O and 210; 95% CI, 164 to 257; P < 0.001 for fixed PEEP of 4 to 5 cm H2O). Intraoperative tidal volume in the dependent lung areas was 43.9% (individualized PEEP), 25.9% (fixed PEEP of 12 cm H2O) and 26.8% (fixed PEEP of 4 to 5 cm H2O) (difference to individualized PEEP: 18.0%; 95% CI, 8.0 to 20.7; P < 0.001 for fixed PEEP of 12 cm H2O and 17.1%; 95% CI, 10.0 to 20.6; P < 0.001 for fixed PEEP of 4 to 5 cm H2O). Mean intraoperative driving pressure was 9.8 cm H2O (individualized PEEP), 14.4 cm H2O (fixed PEEP of 12 cm H2O), and 18.8 cm H2O (fixed PEEP of 4 to 5 cm H2O), P < 0.001. CONCLUSIONS: This secondary analysis of obese patients undergoing laparoscopic surgery found better oxygenation, lower driving pressures, and redistribution of ventilation toward dependent lung areas measured by electrical impedance tomography using individualized PEEP. The impact on patient outcome remains unclear.

Topography and evidence of a separate "fascia plate" for the femoral nerve inside the iliopsoas - A dorsal approach.

The femoral nerve stretch test is an essential part of clinical neurological examinations. This test is performed alongside Magnetic Resonance Imaging (MRI) to determine if there is any evidence of nerve root irritation, usually as a consequence of disc prolapse. The test occasionally gives false positive results. Why such false positives can occur, is subject to continued research, however, no obvious reason has yet emerged. We hypothesize that connectives of the femoral nerve may explain such a phenomenon. To see these connectives, we approached the femoral nerve from dorsal in 12 cases. With the use of ink injection into the subparaneural compartment of the femoral nerve and dissections, a thin transparent structure can clearly be seen that is separate from the epineurium, perineurium, and a paraneural sheath. A continuation of the paraneural sheath produces a fascia plate approximately 1.5 cm in width and with a thickness of around 3 mm, which not only circumnavigates the nerve but projects into the surrounding tissues. Our qualitative observations show that not only does this femoral nerve fascia plate exists, but it also contains nerves and vessels. Furthermore, we show that the femoral nerve is connected to the myofascial complex of the iliopsoas, and in a separate fascia plate from the iliopsoas fascia. This plate is a hitherto neglected connective which extends as far as the spinal dura mater. Evidence from our plastinates and histological sections suggests that when tension is applied to the femoral nerve during the femoral nerve stretch test, tension is also applied to the femoral nerve fascia plate. The femoral nerve fascia plate could be a specific factor that contributes to pain resulting in a false positive femoral nerve stretch test.

Differential lung ventilation assessed by electrical impedance tomography in ultrasound-guided anterior suprascapular nerve block vs. interscalene brachial plexus block: A patient and assessor-blind, randomised controlled trial.

BACKGROUND: Ultrasound-guided interscalene brachial plexus block (ISB) is used to control pain after shoulder surgery. Though effective, drawbacks include phrenic nerve block and motor block of the hand. The ultrasound-guided anterior approach to perform suprascapular nerve block (SSNB) may provide a good alternative. OBJECTIVE: To compare lung ventilation and diaphragmatic activity on the operated side in ISB and SSNB. DESIGN: Randomised, controlled patient-blinded and assessor-blinded trial. SETTING: Outpatient surgical clinic with recruitment from June 2017 to January 2018. PATIENTS: Fifty-five outpatients scheduled for arthroscopic shoulder surgery were allocated randomly to receive SSNB or ISB. Technical problems with monitoring devices unrelated to the intervention led to exclusion of seven patients. The remaining 48 (n=24 in each group) were followed up for 24 h without drop-outs. INTERVENTIONS: Patients received 10 ml of ropivacaine 1.0% wt/vol for both procedures. OUTCOME MEASURES: Percentage lung ventilation on the operated side was the primary endpoint as assessed with electrical impedance tomography (EIT). Secondary endpoints were hemidiaphragmatic motion on the operated side, pain, opioid use, hand strength and numbness, and patient satisfaction. RESULTS: Before regional anaesthesia, the lung on the operated side contributed a median [IQR] of 50 [42 to 56]% of the total lung ventilation. Postoperatively, it was 40 [3 to 50]% (SSNB) vs. 3 [1 to 13]% (ISB) for an adjusted difference of 23 (95% CI, 13 to 34)%, (P < 0.001). Hemidiaphragmatic motion was 1.90 (95% CI, 1.37 to 2.44 cm), (P < 0.001) lower in the ISB group compared with the SSNB group. Hand strength was 11.2 (95% CI 3.6 to 18.9), (P = 0.0024) kg greater for SSNB and numbness was observed in 0% (SSNB) vs. 46% (ISB) of patients, P < 0.001. Pain was low in the first 6 h after surgery in both groups with slightly, but not significantly, lower values for ISB. No meaningful or significant differences were found for opioid use or patient satisfaction. CONCLUSION: An ultrasound-guided anterior approach to SSNB preserves ipsilateral lung ventilation and phrenic function better than a standard ISB. TRIAL REGISTRATION: drks.de identifier: DRKS00011787.

Individualised positive end-expiratory pressure guided by electrical impedance tomography for robot-assisted laparoscopic radical prostatectomy: a prospective, randomised controlled clinical trial.

BACKGROUND: Robot-assisted laparoscopic radical prostatectomy requires general anaesthesia, extreme Trendelenburg positioning and capnoperitoneum. Together these promote impaired pulmonary gas exchange caused by atelectasis and may contribute to postoperative pulmonary complications. In morbidly obese patients, a recruitment manoeuvre (RM) followed by individualised PEEP improves intraoperative oxygenation and end-expiratory lung volume (EELV). We hypothesised that individualised PEEP with initial RM similarly improves intraoperative oxygenation and EELV in non-obese individuals undergoing robot-assisted prostatectomy. METHODS: Forty males (age, 49-76 yr; BMI <30 kg m-2) undergoing prostatectomy received volume-controlled ventilation (tidal volume 8 ml kg-1 predicted body weight). Participants were randomised to either (1) RM followed by individualised PEEP (RM/PEEPIND) optimised using electrical impedance tomography or (2) no RM with 5 cm H2O PEEP. The primary outcome was the ratio of arterial oxygen partial pressure to fractional inspired oxygen (Pao2/Fio2) before the last RM before extubation. Secondary outcomes included regional ventilation distribution and EELV which were measured before, during, and after anaesthesia. The cardiovascular effects of RM/PEEPIND were also assessed. RESULTS: In 20 males randomised to RM/PEEPIND, the median PEEPIND was 14 cm H2O [inter-quartile range, 8-20]. The Pao2/Fio2 was 10.0 kPa higher with RM/PEEPIND before extubation (95% confidence interval [CI], 2.6-17.3 kPa; P=0.001). RM/PEEPIND increased end-expiratory lung volume by 1.49 L (95% CI, 1.09-1.89 L; P<0.001). RM/PEEPIND also improved the regional ventilation of dependent lung regions. Vasopressor and fluid therapy was similar between groups, although 13 patients randomised to RM/PEEPIND required pharmacological therapy for bradycardia. CONCLUSION: In non-obese males, an individualised ventilation strategy improved intraoperative oxygenation, which was associated with higher end-expiratory lung volumes during robot-assisted laparoscopic prostatectomy. CLINICAL TRIAL REGISTRATION: DRKS00004199 (German clinical trials registry).

Individualized Positive End-expiratory Pressure and Regional Gas Exchange in Porcine Lung Injury.

BACKGROUND: In acute respiratory failure elevated intraabdominal pressure aggravates lung collapse, tidal recruitment, and ventilation inhomogeneity. Low positive end-expiratory pressure (PEEP) may promote lung collapse and intrapulmonary shunting, whereas high PEEP may increase dead space by inspiratory overdistension. The authors hypothesized that an electrical impedance tomography-guided PEEP approach minimizing tidal recruitment improves regional ventilation and perfusion matching when compared to a table-based low PEEP/no recruitment and an oxygenation-guided high PEEP/full recruitment strategy in a hybrid model of lung injury and elevated intraabdominal pressure. METHODS: In 15 pigs with oleic acid-induced lung injury intraabdominal pressure was increased by intraabdominal saline infusion. PEEP was set in randomized order: (1) guided by a PEEP/inspired oxygen fraction table, without recruitment maneuver; (2) minimizing tidal recruitment guided by electrical impedance tomography after a recruitment maneuver; and (3) maximizing oxygenation after a recruitment maneuver. Single photon emission computed tomography was used to analyze regional ventilation, perfusion, and aeration. Primary outcome measures were differences in PEEP levels and regional ventilation/perfusion matching. RESULTS: Resulting PEEP levels were different (mean ± SD) with (1) table PEEP: 11 ± 3 cm H2O; (2) minimal tidal recruitment PEEP: 22 ± 3 cm H2O; and (3) maximal oxygenation PEEP: 25 ± 4 cm H2O; P < 0.001. Table PEEP without recruitment maneuver caused highest lung collapse (28 ± 11% vs. 5 ± 5% vs. 4 ± 4%; P < 0.001), shunt perfusion (3.2 ± 0.8 l/min vs. 1.0 ± 0.8 l/min vs. 0.7 ± 0.6 l/min; P < 0.001) and dead space ventilation (2.9 ± 1.0 l/min vs. 1.5 ± 0.7 l/min vs. 1.7 ± 0.8 l/min; P < 0.001). Although resulting in different PEEP levels, minimal tidal recruitment and maximal oxygenation PEEP, both following a recruitment maneuver, had similar effects on regional ventilation/perfusion matching. CONCLUSIONS: When compared to table PEEP without a recruitment maneuver, both minimal tidal recruitment PEEP and maximal oxygenation PEEP following a recruitment maneuver decreased shunting and dead space ventilation, and the effects of minimal tidal recruitment PEEP and maximal oxygenation PEEP were comparable.

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.

Mechanical Ventilation Strategies Targeting Different Magnitudes of Collapse and Tidal Recruitment in Porcine Acid Aspiration-Induced Lung Injury.

Reducing ventilator-associated lung injury by individualized mechanical ventilation (MV) in patients with Acute Respiratory Distress Syndrome (ARDS) remains a matter of research. We randomly assigned 27 pigs with acid aspiration-induced ARDS to three different MV protocols for 24 h, targeting different magnitudes of collapse and tidal recruitment (collapse&TR): the ARDS-network (ARDSnet) group with low positive end-expiratory pressure (PEEP) protocol (permissive collapse&TR); the Open Lung Concept (OLC) group, PaO2/FiO2 >400 mmHg, indicating collapse&TR <10%; and the minimized collapse&TR monitored by Electrical Impedance Tomography (EIT) group, standard deviation of regional ventilation delay, SDRVD. We analyzed cardiorespiratory parameters, computed tomography (CT), EIT, and post-mortem histology. Mean PEEP over post-randomization measurements was significantly lower in the ARDSnet group at 6.8 ± 1.0 cmH2O compared to the EIT (21.1 ± 2.6 cmH2O) and OLC (18.7 ± 3.2 cmH2O) groups (general linear model (GLM) p < 0.001). Collapse&TR and SDRVD, averaged over all post-randomization measurements, were significantly lower in the EIT and OLC groups than in the ARDSnet group (collapse p < 0.001, TR p = 0.006, SDRVD p < 0.004). Global histological diffuse alveolar damage (DAD) scores in the ARDSnet group (10.1 ± 4.3) exceeded those in the EIT (8.4 ± 3.7) and OLC groups (6.3 ± 3.3) (p = 0.16). Sub-scores for edema and inflammation differed significantly (ANOVA p < 0.05). In a clinically realistic model of early ARDS with recruitable and nonrecruitable collapse, mechanical ventilation involving recruitment and high-PEEP reduced collapse&TR and resulted in improved hemodynamic and physiological conditions with a tendency to reduced histologic lung damage.

Whole-Body CT in Multiple Trauma Patients: Clinically Adapted Usage of Differently Weighted CT Protocols. / Polytrauma-Ganzkörper-CT: Klinisch adaptierter Einsatz unterschiedlich gewichteter CT-Untersuchungsprotokolle.

PURPOSE: Whole-body CT (wbCT) has been established as an internationally accepted diagnostic modality in multiple trauma. Until 2011, a uniform CT scanning protocol was used for all multiple trauma patients (pat.) at our hospital (OLD protocol = OP). In 2011, 2 new differently weighted protocols were introduced: TIME protocol (TP) for hemodynamically unstable pat. and DOSE protocol (DP) for pat. with stable vital parameters. The aim of this study was to compare the original "One-fits-all-concept" with the new, clinically oriented approach to wbCT. MATERIALS AND METHODS: This study retrospectively evaluated 3 distinct wbCT protocols, looking at automatic exposure control variation (AEC; OP/TP) and arm positioning close to the body/overhead (TP/DP). The analysis included waist circumference (WC, cm), injury severity score (ISS), examination time (ET, min), image noise (IN), and effective dose (E, mSv). Normality of distribution was assessed with the Kolmogorov-Smirnov test. Data are given as median and range. Test of significance with Kruskal-Wallis test or Mann-Whitney-U-test. Level of significance: 0.05. RESULTS: 308 pat. were included in the study (77 % m; age: 46 a, 18 - 90 a; WC: 93 cm, 66 - 145 cm). ISS was 14 (OP; n = 104; 0 - 75), 18 (TP; n = 102; 0 - 75) and 9 (DP; n = 102; 0 - 50). ET was 3.9 min (OP; 3.3 - 5.6 min), 4.1 min (TP; 2.8 - 7.2 min) and 7.7 min (DP; 6 - 10 min). IN showed no significant differences when comparing OP/TP but was significantly reduced in DP. For a wbCT (vertex to ischium), E could be reduced from 49.7 mSv to 35.4 mSv by optimizing AEC (OP/TP). Through the overhead repositioning of the arms in DP, a further reduction to 28.2 mSv was achieved. CONCLUSION: AEC and arm repositioning have a crucial influence on image quality and dose. The presented clinical approach is superior to the original concept. KEY POINTS: · The use of 2 differently weighted wbCT protocols allows a more flexible approach to the patient's clinical presentation.. · The clinically adapted concept presented in this study allows trauma care centers to reduce the collective dose.. · Whole-body CT is leading to exposure to relevant radiation doses - further multicenter research is required.. CITATION FORMAT: · Reske SU, Braunschweig R, Reske AW et al. Whole-Body CT in Multiple Trauma Patients: Clinically Adapted Usage of Differently Weighted CT Protocols. Fortschr Röntgenstr 2018; 190: 1141 - 1151.

Anterior Suprascapular Nerve Block Versus Interscalene Brachial Plexus Block for Shoulder Surgery in the Outpatient Setting: A Randomized Controlled Patient- and Assessor-Blinded Trial.

BACKGROUND AND OBJECTIVES: The interscalene brachial plexus block (ISB), a potent option to control pain after shoulder surgery, has notable adverse effects. The anterior suprascapular nerve block (SSNB) might provide comparable analgesia and cause less grip-strength impairment. These characteristics were studied in this randomized controlled patient- and assessor-blinded trial. METHODS: Outpatients were randomized to single-shot ultrasound-guided SSNB (10 mL ropivacaine 1%) or ISB (20 mL ropivacaine 0.75%) before general anesthesia for arthroscopic shoulder surgery. Pain (Numerical Rating Scale, 0-10), grip strength, degree of satisfaction, and strength of recommendation were assessed. RESULTS: We randomized 168 patients to each group and analyzed 164 in the SSNB group and 165 in the ISB group. Nerve blocks were successful in 98% of the patients from each group. Both procedures provided good postoperative analgesia, and the mean pain level for SSNB was slightly but significantly lower by 0.32 units (95% confidence interval, 0.18-0.46; P < 0.001) and noninferior given a margin of 1.1 units; P < 0.001. Within the first 24 hours, 162 (99%) of SSNB patients had unimpaired grip strength compared to 81 (49%) of ISB patients (P < 0.001). The multiple primary outcome, superior unimpaired grip strength, and noninferior pain control was significant; P < 0.001. Compared to ISB patients (n = 130 [79%]), significantly more SSNB patients (n = 150 [91%]) were satisfied/highly satisfied. Patients in the SSNB group were more likely to recommend the procedure highly. CONCLUSIONS: For outpatients undergoing arthroscopic shoulder surgery under general anesthesia, the SSNB seems preferable to ISB. It provides excellent postoperative analgesia without exposing patients to impaired mobility and to risks of the more potent but also more invasive ISB.

Mapping Regional Differences of Local Pressure-Volume Curves With Electrical Impedance Tomography.

OBJECTIVES: Lung-protective mechanical ventilation aims to prevent alveolar collapse and overdistension, but reliable bedside methods to quantify them are lacking. We propose a quantitative descriptor of the shape of local pressure-volume curves derived from electrical impedance tomography, for computing maps that highlight the presence and location of regions of presumed tidal recruitment (i.e., elastance decrease during inflation, pressure-volume curve with upward curvature) or overdistension (i.e., elastance increase during inflation, downward curvature). DESIGN: Secondary analysis of experimental cohort study. SETTING: University research facility. SUBJECTS: Twelve mechanically ventilated pigs. INTERVENTIONS: After induction of acute respiratory distress syndrome by hydrochloric acid instillation, animals underwent a decremental positive end-expiratory pressure titration (steps of 2 cm H2O starting from ≥ 26 cm H2O). MEASUREMENTS AND MAIN RESULTS: Electrical impedance tomography-derived maps were computed at each positive end-expiratory pressure-titration step, and whole-lung CT taken every second steps. Airway flow and pressure were recorded to compute driving pressure and elastance. Significant correlations between electrical impedance tomography-derived maps and positive end-expiratory pressure indicate that, expectedly, tidal recruitment increases in dependent regions with decreasing positive end-expiratory pressure (p < 0.001) and suggest that overdistension increases both at high and low positive end-expiratory pressures in nondependent regions (p < 0.027), supporting the idea of two different scenarios of overdistension occurrence. Significant correlations with CT measurements were observed: electrical impedance tomography-derived tidal recruitment with poorly aerated regions (r = 0.43; p < 0.001); electrical impedance tomography-derived overdistension with nonaerated regions at lower positive end-expiratory pressures and with hyperaerated regions at higher positive end-expiratory pressures (r ≥ 0.72; p < 0.003). Even for positive end-expiratory pressure levels minimizing global elastance and driving pressure, electrical impedance tomography-derived maps showed nonnegligible regions of presumed overdistension and tidal recruitment. CONCLUSIONS: Electrical impedance tomography-derived maps of pressure-volume curve shapes allow to detect regions in which elastance changes during inflation. This could promote individualized mechanical ventilation by minimizing the probability of local tidal recruitment and/or overdistension. Electrical impedance tomography-derived maps might become clinically feasible and relevant, being simpler than currently available alternative approaches.

Experimental blunt chest trauma--cardiorespiratory effects of different mechanical ventilation strategies with high positive end-expiratory pressure: a randomized controlled study.

BACKGROUND: Uncertainty persists regarding the optimal ventilatory strategy in trauma patients developing acute respiratory distress syndrome (ARDS). This work aims to assess the effects of two mechanical ventilation strategies with high positive end-expiratory pressure (PEEP) in experimental ARDS following blunt chest trauma. METHODS: Twenty-six juvenile pigs were anesthetized, tracheotomized and mechanically ventilated. A contusion was applied to the right chest using a bolt-shot device. Ninety minutes after contusion, animals were randomized to two different ventilation modes, applied for 24 h: Twelve pigs received conventional pressure-controlled ventilation with moderately low tidal volumes (VT, 8 ml/kg) and empirically chosen high external PEEP (16 cmH2O) and are referred to as the HP-CMV-group. The other group (n = 14) underwent high-frequency inverse-ratio pressure-controlled ventilation (HFPPV) involving respiratory rate of 65 breaths · min(-1), inspiratory-to-expiratory-ratio 2:1, development of intrinsic PEEP and recruitment maneuvers, compatible with the rationale of the Open Lung Concept. Hemodynamics, gas exchange and respiratory mechanics were monitored during 24 h. Computed tomography and histology were analyzed in subgroups. RESULTS: Comparing changes which occurred from randomization (90 min after chest trauma) over the 24-h treatment period, groups differed statistically significantly (all P values for group effect <0.001, General Linear Model analysis) for the following parameters (values are mean ± SD for randomization vs. 24-h): PaO2 (100% O2) (HFPPV 186 ± 82 vs. 450 ± 59 mmHg; HP-CMV 249 ± 73 vs. 243 ± 81 mmHg), venous admixture (HFPPV 34 ± 9.8 vs. 11.2 ± 3.7%; HP-CMV 33.9 ± 10.5 vs. 21.8 ± 7.2%), PaCO2 (HFPPV 46.9 ± 6.8 vs. 33.1 ± 2.4 mmHg; HP-CMV 46.3 ± 11.9 vs. 59.7 ± 18.3 mmHg) and normally aerated lung mass (HFPPV 42.8 ± 11.8 vs. 74.6 ± 10.0 %; HP-CMV 40.7 ± 8.6 vs. 53.4 ± 11.6%). Improvements occurring after recruitment in the HFPPV-group persisted throughout the study. Peak airway pressure and VT did not differ significantly. HFPPV animals had lower atelectasis and inflammation scores in gravity-dependent lung areas. CONCLUSIONS: In this model of ARDS following unilateral blunt chest trauma, HFPPV ventilation improved respiratory function and fulfilled relevant ventilation endpoints for trauma patients, i.e. restoration of oxygenation and lung aeration while avoiding hypercapnia and respiratory acidosis.

Circulatory Arrest due to Retrograde Embolization of a Transapically Implanted Aortic Valve Prosthesis with Subsequent Inversion and Left Ventricular Outflow Occlusion.

An 82-year-old man required aortic valve replacement because of aortic stenosis. A transapical approach was chosen to reduce surgical mortality. Initially, echocardiography and fluoroscopy confirmed correct valve positioning. Shortly thereafter, progressive paravalvular leakage, embolization of the valve prosthesis into the ventricle, and subsequent inversion of the prosthesis with complete left ventricular outflow occlusion were observed by echocardiography. Left ventricular outflow occlusion resulted in immediate circulatory arrest. We immediately converted to on-pump surgical aortic valve replacement. Cardiac output was restored once the valve was replaced. The patient fully recovered. This case report highlights the importance of periprocedural transesophageal echocardiography, which instantly detected the malpositioned valve and guided emergency management of this severe complication.

Intracorporeal knotting of a femoral nerve catheter.

Peripheral nerve catheters are effective and well-established tools to provide postoperative analgesia to patients undergoing orthopedic surgery. The performance of these techniques is usually considered safe. However, placement of nerve catheters may be associated with a considerable number of side effects and major complications have repeatedly been published. In this work, we report on a patient who underwent total knee replacement with spinal anesthesia and preoperative insertion of femoral and sciatic nerve catheters for postoperative analgesia. During insertion of the femoral catheter, significant resistance was encountered upon retracting the catheter. This occurred due to knotting of the catheter. The catheter had to be removed by operative intervention which has to be considered a major complication. The postoperative course was uneventful. The principles for removal of entrapped peripheral catheters are not well established, may differ from those for neuroaxial catheters, and range from cautious manipulation up to surgical intervention.