Central venous-to-arterial carbon dioxide difference and the effect of venous hyperoxia: A limiting factor, or an additional marker of severity in shock?
Central venous-to-arterial carbon dioxide difference (PcvaCO2) has demonstrated its prognostic value in critically ill patients suffering from shock, and current expert recommendations advocate for further resuscitation interventions when PcvaCO2is elevated. PcvaCO2combination with arterial-venous oxygen content difference (PcvaCO2/CavO2) seems to enhance its performance when assessing anaerobic metabolism. However, the fact that PCO2values might be altered by changes in blood O2content (the Haldane effect), has been presented as a limitation of PCO2-derived variables. The present study aimed at exploring the impact of hyperoxia on PcvaCO2and PcvaCO2/CavO2during the early phase of shock. Prospective interventional study. Ventilated patients suffering from shock within the first 24 h of ICU admission. Patients requiring FiO2≥ 0.5 were excluded. At inclusion, simultaneous arterial and central venous blood samples were collected. Patients underwent a hyperoxygenation test (5 min of FiO2100%), and arterial and central venous blood samples were repeated. Oxygenation and CO2variables were calculated at both time points. Twenty patients were studied. The main cause of shock was septic shock (70%). The hyperoxygenation trial increased oxygenation parameters in arterial and venous blood, whereas PCO2only changed at the venous site. Resulting PcvaCO2and PcvaCO2/CavO2significantly increased [6.8 (4.9, 8.1) vs. 7.6 (6.7, 8.5) mmHg, p 0.001; and 1.9 (1.4, 2.2) vs. 2.3 (1.8, 3), p < 0.001, respectively]. Baseline PcvaCO2, PcvaCO2/CavO2and ScvO2correlated with the magnitude of PO2augmentation at the venous site within the trial (ρ -0.46, p 0.04; ρ 0.6, p < 0.01; and ρ 0.7, p < 0.001, respectively). Increased PcvaCO2/CavO2values were associated with higher mortality in our sample [1.46 (1.21, 1.89) survivors vs. 2.23 (1.86, 2.8) non-survivors, p < 0.01]. PcvaCO2and PcvaCO2/CavO2are influenced by oxygenation changes not related to flow. Elevated PcvaCO2and PcvaCO2/CavO2values might not only derive from cardiac output inadequacy, but also from venous hyperoxia. Elevated PcvaCO2/CavO2values were associated with higher PO2transmission to the venous compartment, suggesting higher shunting phenomena.
Critical Care Department, Hospital de Sabadell, Corporació Sanitària Universitària Parc Taulí, Universitat Autònoma de Barcelona, Parc Tauli, 1, 08208, Sabadell, Spain.
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Saludes
Critical Care Department, Hospital de Sabadell, Corporació Sanitària Universitària Parc Taulí, Universitat Autònoma de Barcelona, Parc Tauli, 1, 08208, Sabadell, Spain.|Serviço de Medicina Interna, Hospital Prof. Dr. Fernando Fonseca, Amadora, Portugal.
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Proença
Critical Care Department, Hospital de Sabadell, Corporació Sanitària Universitària Parc Taulí, Universitat Autònoma de Barcelona, Parc Tauli, 1, 08208, Sabadell, Spain.
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Gruartmoner
Critical Care Department, Hospital de Sabadell, Corporació Sanitària Universitària Parc Taulí, Universitat Autònoma de Barcelona, Parc Tauli, 1, 08208, Sabadell, Spain.
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Enseñat
Critical Care Department, Hospital de Sabadell, Corporació Sanitària Universitària Parc Taulí, Universitat Autònoma de Barcelona, Parc Tauli, 1, 08208, Sabadell, Spain.
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Pérez-Madrigal
Critical Care Department, Hospital de Sabadell, Corporació Sanitària Universitària Parc Taulí, Universitat Autònoma de Barcelona, Parc Tauli, 1, 08208, Sabadell, Spain.
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Espinal
Critical Care Department, Hospital de Sabadell, Corporació Sanitària Universitària Parc Taulí, Universitat Autònoma de Barcelona, Parc Tauli, 1, 08208, Sabadell, Spain. jmesquida@tauli.cat.
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http://orcid.org/0000-0003-3670-5021
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Mesquida
D000368:Aged; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000737:chemistry*; D005260:Female; D006801:Humans; D018496:Hyperoxia; D000860:Hypoxia / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D010100:Oxygen / Q000737:chemistry; D011379:Prognosis; D011446:Prospective Studies; D015203:Reproducibility of Results; D012151:Resuscitation; D012769:Shock / Q000097:blood* / Q000175:diagnosis*; D016896:Treatment Outcome; D014680:Veins / Q000473:pathology*
D002245:Carbon Dioxide; D010100:Oxygen
Circulatory shock; Hemodynamic monitoring; Tissue hypoxia; Venous-to-arterial carbon dioxide difference