title: Central venous-to-arterial carbon dioxide partial pressure difference in early resuscitation from septic shock: a prospective observational study.
abstract: BACKGROUND
  Central venous-to-arterial carbon dioxide partial pressure difference (ΔPCO2) can be used as a marker for the efficacy of venous blood in removing the total CO2 produced by the tissues. To date, this role of ΔPCO2 has been assessed only in patients after resuscitation from septic shock with already normalised central venous oxygen saturation (ScvO2 ≥70%). There are no reports on the behaviour of ΔPCO2 and its relationship to cardiac index (CI) and clinical outcome before normal ScvO2 has been achieved.
  
  
  OBJECTIVE
  To investigate the behaviour of ΔPCO2 and its relationship to CI, blood lactate concentration and 28-day mortality during resuscitation in the very early phase of septic shock. To examine whether patients who normalise both ΔPCO2 and ScvO2 during the first 6  h of resuscitation will have a greater percentage decrease in blood lactate concentration than those who only achieve normal ScvO2.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Intensive Care Unit (ICU) in a university hospital.
  
  
  METHODS
  Eighty patients with septic shock were consecutively recruited.
  
  
  METHODS
  Patients were resuscitated in accordance with the recommendations of the Surviving Sepsis Campaign.
  
  
  METHODS
  Blood lactate concentrations, and haemodynamic and oxygen-derived variables were obtained at ICU admission (T0) and 6  h after admission (T6). Lactate decrease was defined as the percentage decrease in lactate concentration from T0 to T6. All cause 28-day mortality was also recorded.
  
  
  RESULTS
  Data are presented as median (interquartile range). At T0, there were significant differences (P < 0.0001) between normal (ΔPCO2 ≤0.8 kPa) and high ΔPCO2 groups for CI (3.9 [3.3 to 4.7] vs. 2.9 [2.3 to 3.1] l min m) and ScvO2 (73 [65 to 80] vs. 61 [53 to 63]%). The correlation between changes in CI and ΔPCO2 was r  =  -0.62, P < 0.0001. Patients who reached a normal ΔPCO2 at T6 had larger decreases in blood lactate concentration and Sequential Organ Failure Assessment scores on day 1. The lactate decrease was greatest in the subgroup achieving both normal ScvO2 and ΔPCO2 at T6. Lactate decrease, unlike ΔPCO2 and ScvO2, was an independent predictor of 28-day mortality.
  
  
  CONCLUSIONS
  Monitoring ΔPCO2 may be a useful tool to assess the adequacy of tissue perfusion during resuscitation. The normalisation of both ΔPCO2 and ScvO2 is associated with a greater decrease in blood lactate concentration than ScvO2 alone. The lactate decrease is an independent predictor of 28-day mortality. Further research is needed to confirm this hypothesis.
authors.affiliation: From the Intensive Care Unit, Centre Hospitalier du Dr Schaffner de Lens, Lens (JM, FP, ML, GG, NV, LT, DT), Department of Anaesthesiology and Critical Care Medicine, University Hospital of Lille, Univ Nord de France, Lille, France (BV).
authors.forename: Jihad
authors.initials: J
authors.lastname: Mallat
authors.forename: Florent
authors.initials: F
authors.lastname: Pepy
authors.forename: Malcolm
authors.initials: M
authors.lastname: Lemyze
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Gasan
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vangrunderbeeck
authors.forename: Laurent
authors.initials: L
authors.lastname: Tronchon
authors.forename: Benoit
authors.initials: B
authors.lastname: Vallet
authors.forename: Didier
authors.initials: D
authors.lastname: Thevenin
mesh_terms: D000368:Aged; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006785:Hospitals, University; D006801:Humans; D007362:Intensive Care Units; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D011446:Prospective Studies; D012151:Resuscitation / Q000379:methods; D012772:Shock, Septic / Q000097:blood / Q000401:mortality / Q000628:therapy*; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D019344:Lactic Acid; D010100:Oxygen