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.

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.