Sublingual Capnometry and Indexes of Tissue Perfusion in Patients With Circulatory Failure

To examine the relationship between sublingual Pco2 (Pslco2) and other indexes of tissue perfusion. Prospective observational study. Medical and coronary ICUs in a tertiary-care teaching hospital. Twenty-five patients with circulatory failure, 19 patients with sepsis, and 6 patients with cardiac failure. Pslco2, gastric intramucosal Pco2 (Pico2), arterial lactate concentration, systemic oxygen delivery, and systemic oxygen consumption were measured at baseline and at 1, 3, 6, 12, and 24 h after the beginning of the study. Pslco2 and the Pslco2-Paco2 gradient were increased but not significantly different in nonsurvivors compared to survivors at baseline. At 24 h, the mean (± SE) Pslco2 was 45 ± 4 mm Hg in survivors and 61 ± 4 mm Hg in nonsurvivors (p = 0.06), while the Pslco2-Paco2 gradient was 14 ± 3 mm Hg in survivors and 29 ± 4 mm Hg in nonsurvivors (p < 0.05). No other significant differences in survivors and nonsurvivors were observed in any other index of perfusion. For all patients, the correlations between Pslco2 and Pico2 (r = 0.459; p < 0.05) and cardiac index (r = 0.285; p < 0.05) were observed. The Pslco2-Paco2 gradient also was correlated with the Pico2-Paco2 gradient (r = 0.323; p < 0.05). When patients were placed into subsets of sepsis and cardiac failure, the strength of the correlations increased in the patients with cardiac failure (Pslco2 vs lactate, r = 0.611 and p < 0.05; Pslco2 vs Pico2, r = 0.613 and p < 0.05; Pslco2 vs Pico2-Paco2 gradient, r = 0.648 and p < 0.05). Pslco2 correlated best with Pico2 and arterial lactate concentration in patients with cardiac failure. Pslco2 and the Pslco2-Paco2 gradient may be useful as indexes of the severity of perfusion failure.