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Clinical Trial
. 2019 Jun 17;20(1):222.
doi: 10.1186/s12882-019-1378-y.

CO2 and O2 removal during continuous veno-venous hemofiltration: a pilot study

Joop Jonckheer  1 , Herbert Spapen  2 , Aziz Debain  3 , Joy Demol  4 , Marc Diltoer  2 , Olivier Costa  5 , Katrien Lanckmans  5 , Taku Oshima  6 , Patrick M Honoré  7 , Manu Malbrain  2 , Elisabeth De Waele  2   4
Affiliations
Clinical Trial

CO2 and O2 removal during continuous veno-venous hemofiltration: a pilot study

Joop Jonckheer et al. BMC Nephrol. .

Erratum in

Abstract

Background: Carbon dioxide (CO2) accumulation is a challenging issue in critically ill patients. CO2 can be eliminated by renal replacement therapy but studies are scarce and clinical relevance is unknown. We prospectively studied CO2 and O2 behavior at different sample points of continuous veno-venous hemofiltration (CVVH) and build a model to calculate CO2 removal bedside.

Methods: In 10 patients receiving standard CVVH under citrate anticoagulation, blood gas analysis was performed at different sample points within the CVVH circuit. Citrate was then replaced by NaCl 0.9% and sampling was repeated. Total CO2 (tCO2), CO2 flow (V̇CO2) and O2 flow (V̇O2) were compared between different sample points. The effect of citrate on transmembrane tCO2 was evaluated. Wilcoxon matched-pairs signed rank test was performed to evaluate significance of difference between 2 data sets. Friedman test was used when more data sets were compared.

Results: V̇CO2 in the effluent (26.0 ml/min) correlated significantly with transmembrane V̇CO2 (24.2 ml/min). This represents 14% of the average expired V̇CO2 in ventilated patients. Only 1.3 ml/min CO2 was removed in the de-aeration chamber, suggesting that CO2 was almost entirely cleared across the membrane filter. tCO2 values in effluent, before, and after the filter were not statistically different. Transmembrane tCO2 under citrate or NaCl 0.9% predilution also did not differ significantly. No changes in V̇O2 were observed throughout the CVVH circuit. Based on recorded data, formulas were constructed that allow bedside evaluation of CVVH-attributable CO2 removal.

Conclusion: A relevant amount of CO2 is removed by CVVH and can be quantified by one simple blood gas analysis within the circuit. Future studies should assess the clinical impact of this observation.

Trial registration: The trial was registered at https://clinicaltrials.gov with trial registration number NCT03314363 on October 192,017.

Keywords: Carbon dioxide removal; Citrate; Continuous renal replacement therapy; Continuous veno-venous hemofiltration; Oxygen removal.

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Conflict of interest statement

Dr. Jonckheer and Prof. Dr. De Waele have received a grant from Baxter as a replacement fee and for logistic support.

Figures

Fig. 1
Fig. 1
Schematic representation of CVVH set-up with location of sampling points and ports of fluid infusion. Pre = predilution fluid, Post = postdilution fluid, AC = de-aeration chamber
Fig. 2
Fig. 2
Evolution of CO2 flow in the extracorporeal blood circuit during NaCl 0.9% postdilution. Sample point 4 was not included as it is not situated in the extracorporeal blood circuit and is not suited to represent evolution of V̇CO2 in the blood. When difference between data was statistical significant different, this was marked with an asterisk
Fig. 3
Fig. 3
Expected CO2 flow in sample place 5 versus CO2 flow at sample place 5 during bicarbonate containing Prismocal B22® postdilution. When difference between data was statistical significant different, this was marked with an asterisk
Fig. 4
Fig. 4
Evolution of tCO2 at different sample points in all series of blood gas analysis. Sample point 5 was not included as it is influenced by bicarbonate Prismocal B22 postdilution fluid. When difference between data was statistical significant different, this was marked with an asterisk
Fig. 5
Fig. 5
Distribution of pCO2 and HCO3- at different sample points in all series of blood gas analysis. Sample point 5 was not included as it is influenced by bicarbonate Prismocal B22 postdilution fluid
Fig. 6
Fig. 6
Effect of citrate on transmembrane tCO2
Fig. 7
Fig. 7
Evolution of O2 flow in the extracorporeal blood circuit in all series of blood gas analysis. Sample point 4 was not included as it is not situated in the extracorporeal blood circuit and is not suited to represent evolution of V̇O2 in the blood
See this image and copyright information in PMC

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