title: Cutaneous ear lobe Pco₂ at 37°C to evaluate microperfusion in patients with septic shock.
abstract: 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.
authors.affiliation: Département d'Anesthésie- Réanimation-SMUR, Hôpital Lariboisière, 75010, Paris, France. vallee.fabrice@gmail.com
authors.forename: Fabrice
authors.initials: F
authors.lastname: Vallée
authors.forename: Joaquim
authors.initials: J
authors.lastname: Mateo
authors.forename: Guillaume
authors.initials: G
authors.lastname: Dubreuil
authors.forename: Thomas
authors.initials: T
authors.lastname: Poussant
authors.forename: Guillaume
authors.initials: G
authors.lastname: Tachon
authors.forename: Ingrid
authors.initials: I
authors.lastname: Ouanounou
authors.forename: Didier
authors.initials: D
authors.lastname: Payen
mesh_terms: D000368:Aged; D001785:Blood Gas Monitoring, Transcutaneous / Q000295:instrumentation; D019296:Capnography / Q000295:instrumentation*; D002245:Carbon Dioxide / Q000097:blood*; D004423:Ear; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012772:Shock, Septic / Q000097:blood* / Q000175:diagnosis / Q000503:physiopathology; D012867:Skin / Q000098:blood supply*; D013696:Temperature
chemical_list: D002245:Carbon Dioxide