Sublingual capnometry and indexes of tissue perfusion in patients with circulatory failure

Objective: To examine the relationship between sublingual Pco(2) (Pslco(2)) and other indexes of tissue perfusion. Design: Prospective observational study. Setting: Medical and coronary ICUs in a tertiary-care teaching hospital. Subjects: Twenty-five patients with circulatory failure, 19 patients with s epsis, and 6 patients with cardiac failure. Measurements and main results: Pslco2, gastric intramucosal Pco(2) (Pico(2) ), arterial lactate concentration, systemic oxygen delivery, and systemic o xygen consumption were measured at baseline and at 1, 3, 6, 12, and 24 h af ter the beginning of the study. Pslco2 and the Pslco(2)-Paco(2) gradient we re increased but not significantly different in nonsurvivors compared to su rvivors at baseline. At 24 h, the mean (+/-SE) Pslco(2) was 45 +/- 4 mm Hg in survivors and 61 +/- 4 mm Hg in nonsurvivors (p = 0.06), while the Pslco (2)-Paco(2) gradient was 14 +/- 3 mm Hg in survivors and 29 +/- 4 nun Hg in nonsurvivors (p < 0.05). No other significant differences in survivors and nonsurvivors were observed in any other index of perfusion. For all patien ts, the correlations between Pslco(2) and Pico(2) (r = 0.459; p < 0.05) and cardiac index (r = 0.285; p < 0.05) were observed. The Pslco2-Paco2 gradie nt also was correlated with the Pico(2)-Paco(2) 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 fai lure (Pslco(2) vs lactate, r = 0.611 and p < 0.05; Pslco(2) vs Pico(2), r = 0.613 and p < 0.05; Pslco(2) vs Pico(2)-Paco(2) gradient, r = 0.648 and p < 0.05). Conclusion: Pslco2 correlated best with Picot and arterial lactate concentr ation in patients with cardiac failure. Pslco2, and the Pslco2-Paco2 gradie nt may, be useful as indexes of the severity of perfusion failure.