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World J Crit Care Med. Feb 4, 2016; 5(1): 47-56
Published online Feb 4, 2016. doi: 10.5492/wjccm.v5.i1.47
Use of venous-to-arterial carbon dioxide tension difference to guide resuscitation therapy in septic shock
Jihad Mallat, Malcolm Lemyze, Laurent Tronchon, Benoît Vallet, Didier Thevenin
Jihad Mallat, Malcolm Lemyze, Laurent Tronchon, Benoît Vallet, Didier Thevenin, Department of Anesthesiology and Critical Care Medicine, Centre Hospitalier du Dr. Schaffner de Lens, 62300 Lens, France
Author contributions: Mallat J contributed to conception, designed and wrote the paper; Lemyze M, Tronchon L, Vallet B and Thevenin D revised the manuscript critically for important intellectual content.
Conflict-of-interest statement: Authors declare no conflicts of interests for this article.
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: Jihad Mallat, MD, Department of Anesthesiology and Critical Care Medicine, Centre Hospitalier du Dr. Schaffner de Lens, 99 route de La Bassée, 62300 Lens, France. mallatjihad@gmail.com
Telephone: +33-321-691088 Fax: +33-321-691839
Received: August 5, 2015
Peer-review started: August 6, 2015
First decision: September 16, 2015
Revised: October 12, 2015
Accepted: December 3, 2015
Article in press: December 4, 2015
Published online: February 4, 2016
Processing time: 171 Days and 11.5 Hours
Abstract

The mixed venous-to-arterial carbon dioxide (CO2) tension difference [P (v-a) CO2] is the difference between carbon dioxide tension (PCO2) in mixed venous blood (sampled from a pulmonary artery catheter) and the PCO2 in arterial blood. P (v-a) CO2 depends on the cardiac output and the global CO2 production, and on the complex relationship between PCO2 and CO2 content. Experimental and clinical studies support the evidence that P (v-a) CO2 cannot serve as an indicator of tissue hypoxia, and should be regarded as an indicator of the adequacy of venous blood to wash out the total CO2 generated by the peripheral tissues. P (v-a) CO2 can be replaced by the central venous-to-arterial CO2 difference (ΔPCO2), which is calculated from simultaneous sampling of central venous blood from a central vein catheter and arterial blood and, therefore, more easy to obtain at the bedside. Determining the ΔPCO2 during the resuscitation of septic shock patients might be useful when deciding when to continue resuscitation despite a central venous oxygen saturation (ScvO2) > 70% associated with elevated blood lactate levels. Because high blood lactate levels is not a discriminatory factor in determining the source of that stress, an increased ΔPCO2 (> 6 mmHg) could be used to identify patients who still remain inadequately resuscitated. Monitoring the ΔPCO2 from the beginning of the reanimation of septic shock patients might be a valuable means to evaluate the adequacy of cardiac output in tissue perfusion and, thus, guiding the therapy. In this respect, it can aid to titrate inotropes to adjust oxygen delivery to CO2 production, or to choose between hemoglobin correction or fluid/inotrope infusion in patients with a too low ScvO2 related to metabolic demand. The combination of P (v-a) CO2 or ΔPCO2 with oxygen-derived parameters through the calculation of the P (v-a) CO2 or ΔPCO2/arteriovenous oxygen content difference ratio can detect the presence of global anaerobic metabolism.

Keywords: Venous-to-arterial carbon dioxide tension difference; Carbon dioxide production; Oxygen supply dependency; Cardiac output; tissue hypoxia; Anaerobic metabolism; Oxygen consumption; Resuscitation; Septic shock

Core tip: Early recognition and correction of tissue hypoperfusion are cornerstones in the management of septic shock patients. The venous-to-arterial carbon dioxide tension difference, which is a marker of the adequacy of cardiac output to global metabolic demand, is a helpful additional means to detect patients who stay under-resuscitated after optimization of O2-derived parameters. In this regard, its monitoring should help the clinicians for the decision of giving therapy targeting at increasing cardiac output.