title: Carbon dioxide dialysis in a swine model utilizing systemic and regional anticoagulation.
abstract: BACKGROUND
  Extracorporeal carbon dioxide removal (ECCO2R) has been gaining interest to potentially facilitate gas transfer and equilibrate mild to moderate hypercapnic acidosis, when standard therapy with non-invasive ventilation is deemed refractory. However, concern regarding the effectiveness of low-flow CO2 removal remains. Additionally, the prospect to steadily reduce hypercapnia via low-flow ECCO2R technique is limited, especially with regional anticoagulation which potentially reduces the risk of bleeding. Therefore, an in vivo study was conducted to determine the efficacy of CO2 removal through a modified renal dialysis unit during the carbon dioxide dialysis study using systemic and regional anticoagulation.
  
  
  METHODS
  The acute study was conducted for 14 h in landrace pigs (51 ± 3 kg). CO2 removal using a diffusion membrane oxygenator substituting the hemoconcentrator was provided for 6 h. Blood and gas (100 % O2) flows were set at 200 and 5 L/min, respectively. Anticoagulation was achieved by systemic heparinization (n = 7) or regional trisodium citrate 4 % (n = 7).
  
  
  RESULTS
  The CO2 transfer was highest during the initial hour and ranged from 45 to 35 mL/min, achieving near eucapnic values. Regional and systemic anticoagulation were both effective in decreasing arterial pCO2 (from 8.9 ± 1.3 kPa to 5.6 ± 0.8 kPa and from 8.6 ± 1.0 kPa to 6.3 ± 0.7 kPa, p < 0.05 for both groups, respectively). Furthermore, pH improved (from 7.32 ± 0.08 to 7.47 ± 0.07 and from 7.37 ± 0.04 to 7.49 ± 0.01, p < 0.05) for both regional and systemic anticoagulation groups, respectively. Upon ceasing CO2 dialysis, hypercapnia ensued. The liver and kidney function test results were normal, and scanning electron microscopy analysis revealed only some cellular and fibrin adhesion on the oxygenator fibre in the heparin group.
  
  
  CONCLUSIONS
  CO2 dialysis utilizing either regional or systemic anticoagulation showed to be safe and effective in steady transfer of CO2 and consequently optimizing pH.
authors.affiliation: Department of Cardiothoracic Surgery, CARIM, Maastricht University Medical Center, PO box 5800, 6202 AZ, Maastricht, the Netherlands. ajay.sharma@maastrichtuniversity.nl.
authors.forename: A S
authors.initials: AS
authors.lastname: Sharma
authors.affiliation: Department of Cardiothoracic Surgery, CARIM, Maastricht University Medical Center, PO box 5800, 6202 AZ, Maastricht, the Netherlands.
authors.forename: P W
authors.initials: PW
authors.lastname: Weerwind
authors.affiliation: Department of Clinical Chemistry, Maastricht University Medical Center, Maastricht, the Netherlands.
authors.forename: O
authors.initials: O
authors.lastname: Bekers
authors.affiliation: Department of Respiratory Medicine, NUTRIM, Maastricht University Medical Center, Maastricht, the Netherlands.
authors.forename: E M
authors.initials: EM
authors.lastname: Wouters
authors.affiliation: Department of Cardiothoracic Surgery, CARIM, Maastricht University Medical Center, PO box 5800, 6202 AZ, Maastricht, the Netherlands.
authors.forename: J G
authors.initials: JG
authors.lastname: Maessen
keywords: Acute-on-chronic hypercapnic respiratory failure; Animal model; Low-flow CO2 removal; Regional anticoagulation; Systemic anticoagulation