Subjective and physiological responses to the 35% carbon dioxide challenge in healthy and non-clinical control populations: a meta-analysis and systematic review

Abstract Background and study aims Carbon dioxide (CO2) insufflation has been suggested to be an ideal alternative to room air insufflation to reduce trapped air within the bowel lumen after balloon assisted enteroscopy (BAE). We performed a systematic review and meta-analysis to assess the safety and efficacy of utilizing CO2 insufflation as compared to room air during BAE. Patients and methods The primary outcome is mean change in visual analog scale (VAS; 10 cm) at 1, 3, and 6 hours to assess pain. Secondary outcomes include insertion depth (anterograde or retrograde), adverse events, total enteroscopy rate, diagnostic yield, mean anesthetic dosage, and PaCO2 at procedure completion. We searched MEDLINE and the Cochrane Central Register of Controlled Trials (CENTRAL) from inception until May 2015. Multiple independent extractions were performed, the process was executed as per the standards of the Cochrane collaboration. Results Four randomized controlled trials (RCTs) were included in the meta-analysis. VAS at 6 hours favored CO2 over room air (MD 0.13; 95 % CI 0.01, 0.25; p = 0.03). Anterograde insertion depth (cm) was improved in the CO2 group (MD, 58.2; 95 % CI 17.17, 99.23; p = 0.005), with an improvement in total enteroscopy rate in the CO2 group (RR 1.91; 95 % CI 1.20, 3.06; p = 0.007). Mean dose of propofol (mg) favored CO2 compared to air (MD, – 70.53; 95 % CI – 115.07, – 25.98; P = 0.002). There were no differences in adverse events in either group. Conclusions Despite the ability of CO2 to improve insertion depth and decrease amount of anesthesia required, further randomized control trials are needed to determine the agent of choice for insufflation in balloon assisted enteroscopy.

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Venovenous Extracorporeal CO2 removal to support ultraprotective ventilation in moderate-severe ARDS: A systematic review and meta-analysis of the literature

10.1101/2021.10.26.21265546 ◽

2021 ◽

Author(s):

Elliott Worku ◽

Daniel Brodie ◽

Ryan Ruiyang Ling ◽

Kollengode Ramanathan ◽

Alain Combes ◽

...

Keyword(s):

Carbon Dioxide ◽

Systematic Review ◽

Acute Respiratory Distress Syndrome ◽

Distress Syndrome ◽

Meta Analysis ◽

Protective Ventilation ◽

Driving Pressure ◽

List Type ◽

Extracorporeal Carbon Dioxide Removal ◽

Ultraprotective Ventilation

AbstractBackgroundA strategy that limits tidal volumes and inspiratory pressures, improves outcomes in patients with the acute respiratory distress syndrome (ARDS). Extracorporeal carbon dioxide removal (ECCO2R) may facilitate ultra-protective ventilation. We conducted a systematic review and meta-analysis to evaluate the efficacy and safety of venovenous ECCO2R in supporting ultra-protective ventilation in moderate-to-severe ARDS.MethodsMEDLINE and EMBASE were interrogated for studies (2000-2021) reporting venovenous ECCO2R use in patients with moderate-to-severe ARDS. Studies reporting ≥10 adult patients in English language journals were included. Ventilatory parameters after 24 hours of initiating ECCO2R, device characteristics, and safety outcomes were collected. The primary outcome measure was the change in driving pressure at 24 hours of ECCO2R therapy in relation to baseline. Secondary outcomes included change in tidal volume, gas exchange, and safety data.ResultsTen studies reporting 421 patients (PaO2:FiO2 141.03mmHg) were included. Extracorporeal blood flow rates ranged from 0.35-1.5 L/min. Random effects modelling indicated a 3.56 cmH2O reduction (95%-CI: 3.22-3.91) in driving pressure from baseline (p<0.001) and a 1.89 ml/kg (95%-CI: 1.75-2.02, p<0.001) reduction in tidal volume. Oxygenation, respiratory rate and PEEP remained unchanged. No significant interactions between driving pressure reduction and baseline driving pressure, partial pressure of arterial carbon dioxide or PaO2:FiO2 ratio were identified in metaregression analysis. Bleeding and haemolysis were the commonest complications of therapy.ConclusionsVenovenous ECCO2R permitted significant reductions in ΔP in patients with moderate-to-severe ARDS. Heterogeneity amongst studies and devices, a paucity of randomised controlled trials, and variable safety reporting calls for standardisation of outcome reporting.Prospective evaluation of optimal device operation and anticoagulation in high quality studies is required before further recommendations can be made.Key MessagesWhat is the Key Question?In adult patients with moderate-to-severe acute respiratory distress syndrome (ARDS), can venovenous extracorporeal carbon dioxide removal (ECCO2R) support ultraprotective lung ventilation beyond the current standard for protective ventilation in ARDS?What is the bottom line?Systematic review of available data on venovenous ECCO2R shows that it can reduce driving pressure in ventilated patients with moderate-to-severe ARDS, supporting ultraprotective ventilation. Prospective measurement of mechanical power, and greater emphasis on safety and patient-centred outcomes is needed.Why read on?This is the first systematic review to exclusively address venovenous ECCO2R use in the moderate-to-severe ARDS cohort. We report the degree of lung protection achieved with venovenous ECCO2R devices, along with factors potentially limiting widespread adoption.

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