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World J Nephrol. Sep 6, 2016; 5(5): 429-436
Published online Sep 6, 2016. doi: 10.5527/wjn.v5.i5.429
Carbon dioxide: Global warning for nephrologists
Marco Marano, Anna D’Amato, Alessandra Cantone
Marco Marano, Anna D’Amato, Hemodialysis Unit, Maria Rosaria Clinic, Pompeii, 80045 Naples, Italy
Alessandra Cantone, Bayview Physicians Group, Suffolk, VA 23462, United States
Author contributions: Marano M designed the review and wrote the paper; D’Amato A contributed to intellectual content of the manuscript and made critical revisions; Cantone A contributed to intellectual content of the manuscript and revised English language.
Conflict-of-interest statement: The authors declare having no conflict of interest.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Marco Marano, MD, Hemodialysis Unit, Maria Rosaria Clinic, via Colle San Bartolomeo, 50, Pompeii, 80045 Naples, Italy. marano965@gmail.com
Telephone: +39-081-5359517 Fax: +39-081-8502821
Received: April 30, 2016
Peer-review started: May 3, 2016
First decision: July 6, 2016
Revised: August 2, 2016
Accepted: August 17, 2016
Article in press: August 19, 2016
Published online: September 6, 2016
Processing time: 123 Days and 10.9 Hours
Abstract

The large prevalence of respiratory acid-base disorders overlapping metabolic acidosis in hemodialysis population should prompt nephrologists to deal with the partial pressure of carbon dioxide (pCO2) complying with the reduced bicarbonate concentration. What the most suitable formula to compute pCO2 is reviewed. Then, the neglected issue of CO2 content in the dialysis fluid is under the spotlight. In fact, a considerable amount of CO2 comes to patients’ bloodstream every hemodialysis treatment and “acidosis by dialysate” may occur if lungs do not properly clear away this burden of CO2. Moreover, vascular access recirculation may be easy diagnosed by detecting CO2 in the arterial line of extracorporeal circuit if CO2-enriched blood from the filter reenters arterial needle.

Keywords: Acid-base assessment; Bicarbonate; Carbon dioxide; Hemodialysis; Metabolic acidosis; Mixed disorders; Ventilatory response; Expected pressure of carbon dioxide; Vascular access recirculation

Core tip: Partial pressure of carbon dioxide (pCO2) should be always taken into account for comprehensive assessment of acid-base imbalances of hemodialysis patients, also because respiratory disorders are very common in this population. To infer a respiratory disorder superimposing to metabolic acidosis, nephrologists should compute the expected pCO2 complying with the reduced bicarbonate concentration. Moreover, they have to take in account CO2 load from dialysis solution, because this burden may be harmful if ventilatory compensation does not properly occur. Finally, checking an increase of pCO2 in arterial line of extracorporeal circuit is an easy and reliable method to discover vascular access recirculation.