Fabrice Vallée, MD, Joaquim Mateo, MD, Guillaume Dubreuil, MD, Thomas Poussant, MD, Guillaume Tachon, MD, Ingrid Ouanounou, MD and Didier Payen, MD, PhD. Published online before print May 14, 2010, doi: 10.1378/chest.09-2690
CHEST November 2010 vol. 138 no. 5 1062-1070

Background: Tissue hypercarbia is related to hypoperfusion and microcirculatory disturbances in patients with septic shock. Transcutaneous Pco2 devices using a heated sensor to arterialize the tissue have been used as an alternative method for estimation of Paco2. This study investigates whether a cutaneous sensor attached to an ear lobe and regulated to 37°C could be used to measure cutaneous Pco2 (Pcco2) and evaluate microperfusion in patients with septic shock.

Methods: Fifteen stable patients in an ICU were studied as a control group. Forty-six patients with septic shock who were ventilated were enrolled as the study group. The difference of the gradients between Pcco2 and Paco2 (Pc-aco2) and between Pcco2 and end-tidal Pco2(Pc-etco2) were evaluated for 36 h. Variations of the Pc-aco2 and Pc-etco2 during fluid challenge were compared with microcirculatory skin blood flow (mBFskin) assessed by laser Doppler flowmetry.

Results: The baseline levels for Pc-aco2 and Pc-etco2 were significantly higher in the patients with septic shock than in the control group (14.8 [12.6] vs 6 [2.7] mm Hg and 25 [16.3] vs 9 [3.8] mm Hg, P < .0001, respectively). During the following 36 h, the Pc-aco2 and Pc-etco2 for the surviving patients with septic shock decreased significantly compared with the nonsurvivors (P < .01). The evolution of macrohemodynamic parameters showed no differences between survivors and nonsurvivors. At hour 24, a Pc-aco2 > 16 mm Hg and a Pc-etco2 > 26 mm Hg were related to poor outcome. Pc-aco2 and Pc-etco2 variations during fluid challenge were inversely correlated with changes in mBFskin (r2 = 0.7).

Conclusions: Ear lobe cutaneous Pco2 at 37°C represents a noninvasive technique to assess tissue Pco2 measurement. Pc-aco2 and Pc-etco2 were related to outcome and provide continuous information on microperfusion in patients with septic shock.

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