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.