Effects of hypercapnia versus normocapnia during general anesthesia on outcomes: a systematic review and meta-analysis.

BACKGROUND: The effect of mild changes in CO2 levels to organ perfusion and tissue inflammation are well known, whereas an influence of hypercapnia under general anesthesia on adverse events as nausea and vomiting, or length of hospital stay is barely examined. The goal of our meta-analysis was to identify possibly positive effects of hypercapnia versus normocapnia in general anesthesia in adult patients. METHODS: We conducted a systematic review of parallel-arm randomised controlled trials comparing hypercapnia versus normocapnia in adult patients undergoing general anesthesia. In July 2018 and September 2019 we searched "CENTRAL‿, "MEDLINE‿, and "Embase‿, checked reference lists of all included studies and relevant systematic reviews for additional references to trials. Two review authors independently assessed trials for inclusion, extracted data, and completed a "Risk of bias‿ assessment for all included studies. RESULTS: Our search identified 297 records after abstract screening 30 full-text papers remained for further examination. Ten publications met our inclusion criteria and were used for narrative description of this systematic review. Three studies were eligible for the meta-analysis normocapnia versus hypercapnia with the outcomes: time to extubation and adverse events. On average, time to extubation was significantly reduced in the hypercapnia group with a mean difference 3.78 (95% CI 0.85 to 6.71). No difference was found regarding adverse events. CONCLUSIONS: The findings of our study do not enable us to produce evidence of a positive influence of increased CO2 partial pressure levels during general anesthesia. A well-planned, adequately powered randomized controlled trial would be desirable in the future.

In Vitro and In Vivo Feasibility Study for a Portable VV-ECMO and ECCO2R System.

Extracorporeal membrane oxygenation (ECMO) is an established rescue therapy for patients with chronic respiratory failure waiting for lung transplantation (LTx). The therapy inherent immobilization may result in fatigue, consecutive deteriorated prognosis, and even lost eligibility for transplantation. We conducted a feasibility study on a novel system designed for the deployment of a portable ECMO device, enabling the physical exercise of awake patients prior to LTx. The system comprises a novel oxygenator with a directly connected blood pump, a double-lumen cannula, gas blender and supply, as well as control and energy management. In vitro experiments included tests regarding performance, efficiency, and blood damage. A reduced system was tested in vivo for feasibility using a novel large animal model. Six anesthetized pigs were first positioned in supine position, followed by a 45° angle, simulating an upright position of the patients. We monitored performance and vital parameters. All in vitro experiments showed good performance for the respective subsystems and the integrated system. The acute in vivo trials of 8 h duration confirmed the results. The novel portable ECMO-system enables adequate oxygenation and decarboxylation sufficient for, e.g., the physical exercise of designated LTx-recipients. These results are promising and suggest further preclinical studies on safety and efficacy to facilitate translation into clinical application.

Validation of RESP and PRESERVE score for ARDS patients with pumpless extracorporeal lung assist (pECLA).

BACKGROUND: RESP score and PRESERVE score have been validated for veno-venous Extracorporeal Membrane Oxygenation in severe ARDS to assume individual mortality risk. ARDS patients with low-flow Extracorporeal Carbon Dioxide Removal, especially pumpless Extracorporeal Lung Assist, have also a high mortality rate, but there are no validated specific or general outcome scores. This retrospective study tested whether these established specific risk scores can be validated for pumpless Extracorporeal Lung Assist in ARDS patients in comparison to a general organ dysfunction score, the SOFA score. METHODS: In a retrospective single center cohort study we calculated and evaluated RESP, PRESERVE, and SOFA score for 73 ARDS patients with pumpless Extracorporeal Lung Assist treated between 2002 and 2016 using the XENIOS iLA Membrane Ventilator. Six patients had a mild, 40 a moderate and 27 a severe ARDS according to the Berlin criteria. Demographic data and hospital mortality as well as ventilator settings, hemodynamic parameters, and blood gas measurement before and during extracorporeal therapy were recorded. RESULTS: Pumpless Extracorporeal Lung Assist of mechanical ventilated ARDS patients resulted in an optimized lung protective ventilation, significant reduction of PaCO2, and compensation of acidosis. Scoring showed a mean score of alive versus deceased patients of 3 ± 1 versus - 1 ± 1 for RESP (p < 0.01), 3 ± 0 versus 6 ± 0 for PRESERVE (p < 0.05) and 8 ± 1 versus 10 ± 1 for SOFA (p < 0.05). Using receiver operating characteristic curves, area under the curve (AUC) was 0.78 (95% confidence interval (CI) 0.67-0.89, p < 0.01) for RESP score, 0.80 (95% CI 0.70-0.90, p < 0.0001) for PRESERVE score and 0.66 (95% CI 0.53-0.79, p < 0.05) for SOFA score. CONCLUSIONS: RESP and PRESERVE scores were superior to SOFA, as non-specific critical care score. Although scores were developed for veno-venous ECMO, we could validate RESP and PRESERVE score for pumpless Extracorporeal Lung Assist. In conclusion, RESP and PRESERVE score are suitable to estimate mortality risk of ARDS patients with an arterio-venous pumpless Extracorporeal Carbon Dioxide Removal.