The venous-arterial difference in CO2 should be interpreted with caution in case of respiratory alkalosis in healthy volunteers.

The venous-arterial difference in CO2 (ΔCO2) has been proposed as an index of the adequacy of tissue perfusion in shock states. We hypothesized that the variation in PaCO2 (hyper- or hypocapnia) could impact ΔCO2, partly through microcirculation adaptations. Fifteen healthy males volunteered to participate. For hypocapnia condition (hCO2), the subjects were asked to hyperventilate, while they were asked to breathe a gas mixture containing 8 % CO2 for hypercapnia condition (HCO2). The 2 conditions were randomly assigned. Blood gases were measured at baseline before each condition, and after 5-7 min of either hCO2 or HCO2 condition. Microcirculation was assessed by the muscle reoxygenation slope measured with near infrared spectroscopy following a vascular occlusion test and by skin circulation with in vivo reflectance confocal microscopy. ΔCO2 was significantly increased with hCO2 while it tended to decrease with HCO2 (non-significant). HCO2 induced a moderate increase of the resaturation slope of NIRS oxygenation. Skin microcirculatory blood flow significantly dropped with hCO2, while it remained unchanged with hypercapnia. Our results warrant cautious interpretation of ΔCO2 as an indicator of tissue perfusion during respiratory alkalosis.

Impact of a visual aid on discordance between physicians and family members about prognosis of critically ill patients.

OBJECTIVE: This study aimed to evaluate the impact of a visual aid on the discordance about prognosis between physicians and family members. METHODS: The study was performed in a general intensive care department with two 6-bed units. In the unit A, family members could consult a visual aid depicting day by day the evolution of global, hemodynamic, respiratory, renal and neurological conditions of the patient on a 10-point scale. In the unit B, they only received oral medical information. On day 7 of the ICU stay, the physician and family members estimated the prognosis of the patient among four proposals (life threatened; steady state but may worsen; steady state, should heal; will heal). Then we compared the rate of discordance about prognosis between physicians and family members in the two units. RESULTS: Seventy-nine consecutive patients admitted in the intensive care department and still present at day 7, their family members and physicians, were enrolled. Patients in the two units were comparable in age, sex ratio, reason for admission, SAPS II at admission and SOFA score at day 7. In the unit A, physician-family members discordance about prognosis occurred for 12 out of 39 patients (31%) vs. 22 out of 40 patients (55%) in the unit B (P=0.04). CONCLUSION: In our study, adding a visual aid depicting the evolution of the condition of critically ill patients day by day to classic oral information allowed the family to have an estimate of the prognosis less discordant with the estimate of the physician.