Carbon dioxide: Global warning for nephrologists

Figure 1 Risk of death and serum bicarbonate concentration in hemodialysis patients. Trend of risk inferred by data from Bommer et al[2] (A), Wu et al[3] (B), Tentori et al[4] (C), Yamamoto et al[5] (D). HCO₃: Bicarbonate concentration.

Figure 2 Relationship between pressure of carbon dioxide and bicarbonate concentration in chronic metabolic acidosis. The relationship between pCO₂ and HCO₃ during metabolic acidosis is graphically depicted as a curve. Two linear approximations (straight lines) equivalent to Winters’ formula (pCO₂ = 1.5 × HCO₃ + 8) and to the practical rule (pCO₂ = 1.2 × HCO₃ + 11.2) are also shown. HCO₃: Bicarbonate concentration; pCO₂: Pressure of carbon dioxide.

Figure 3 Example of gas analysis in on-line hemodiafiltration. Additional CO₂ load delivered via substitution fluid infusion during online hemodiafiltration. Reproduced with permission from Marano et al[30]. CO₂: Carbon dioxide.

Figure 4 Course of carbon dioxide in presence of vascular access recirculation. pCO₂ from dialyzer re-entering the extracorporeal circuit reveals vascular access recirculation. pCO₂: Pressure of carbon dioxide.

Figure 5 Performance of “RecirCO₂lation” test to detect vascular access recirculation. Receiver operating curves of pCO₂-increase (solid line) and pCO₂ at 5 min (dotted line) for diagnosis of vascular access recirculation using Glucose Infusion Test (> 0.3%) as reference. Reproduced with permission from Marano et al[32]. AUC: Area under curve; pCO₂: Pressure of carbon dioxide.