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 sepsis, and 6 patients with cardiac failure.

Measurements And Main Results: PslCO(2), gastric intramucosal PCO(2) (PiCO(2)), 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. PslCO(2) and the PslCO(2)-PaCO(2) gradient were increased but not significantly different in nonsurvivors compared to survivors 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 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 PslCO(2) and PiCO(2) (r = 0.459; p < 0.05) and cardiac index (r = 0.285; p < 0.05) were observed. The PslCO(2)-PaCO(2) gradient 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 failure (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: PslCO(2) correlated best with PiCO(2) and arterial lactate concentration in patients with cardiac failure. PslCO(2) and the PslCO(2)-PaCO(2) gradient may be useful as indexes of the severity of perfusion failure.