Chest
Volume 138, Issue 5, November 2010, Pages 1062-1070
Journal home page for Chest

Original Research
Critical Care Medicine
Cutaneous Ear Lobe Pco2 at 37°C To Evaluate Microperfusion in Patients With Septic Shock

https://doi.org/10.1378/chest.09-2690Get rights and content

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.

Section snippets

Study Population

The study was conducted between March and November 2008 in a 20-bed ICU of a university hospital after approval by our institutional comité de protection des personnes (No. IRB0006477). Patients were enrolled after written informed consent was obtained from the patient or the next of kin. Forty-six patients ≥ 18 years were studied within 24 h after the onset of septic shock, which was defined according to classic criteria.23 The diagnosis of infection was established by the presence of bacteria

Comparison Between Patients With Septic Shock and Patients in the Control Group

Baseline characteristics of patients with septic shock and patients in the control group are described in Table 1. The baseline levels of Pc-aco2 and Pc-etco2 were significantly higher in patients with septic shock than in patients 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 (Fig 1). The areas under the ROC curve for Pc-aco2 and Pc-etco2 were 0.94 (0.85–0.98) and 0.96 (0.86–0.99), respectively. A threshold of 9 mm Hg for Pc-aco2

Discussion

This study shows four things. First, when measuring at 37° at the ear lobe, a cutoff value of 9 mm Hg for the gradient Pc-aco2 discriminated patients with septic shock from the patients in the control group in the ICU with a sensitivity of 86% and a specificity of 93%. Second, the noninvasive gradient, Pc-etco2, also discriminated patients with septic shock from the patients in the control group in the ICU with a cutoff value of 16 mmHg. Third, in patients with septic shock, the evolution of

Acknowledgments

Author Contributions: Dr Vallée: contributed to collecting the data, performing the statistical analysis, and writing the manuscript.

Dr Mateo: contributed to collecting the data, performing the statistical analysis, and writing the manuscript.

Dr Dubreuil: contributed to collecting the data.

Dr Poussant: contributed to collecting the data.

Dr Tachon: contributed to collecting the data.

Dr Ouanounou: contributed to collecting the data.

Dr Payen: contributed to designing the study and correcting the

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    Funding/Support: This study was supported in part by a research grant from the University of Paris 7, Plan Quadriennal Ministère de la Recherche.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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