Please see Bibliography of References for a list of abstracts, manuscripts and posters.

Microvascular Dysfunction

Can near infrared spectroscopy detect functional microcirculation abnormalities in septic patients?

Georger JF, Chaari A, Richard C, Teboul JL. Int Care Med. 2007;33(Supp 2):S254. Abstract 0987.

Introduction: The near infrared spectrometry (NIRS) assesses the haemoglobin saturation in the tissue (StO₂). Performance of a dynamic test resulting in a transient regional ischemia can provide additional information on the functional integrity of the local microcirculation (washout effect) through the analysis of the slope of the StO₂ re-ascension after occlusion release.

Objective: To examine whether 1) baseline StO₂ and the StO₂ re-ascension slope are altered in severe sepsis and septic shock patients in comparison with healthy volunteers, and 2) these new regional perfusion variables correlate with classical systemic perfusion variables.

Methods: We included 27 patients in severe sepsis (n=3) and septic shock (n=24) within the first 48 hours after ICU admission. Cardiac index (CI) was obtained from a transpulmonary thermodilution device (PiCCO™, Pulsion Germany). The thenar muscle StO₂ was continuously measured whit Inspectra™ StO₂ model 640 (Hutchinson Technology) and after transient forearm ischemia induced by pneumatic cuff inflation (220 mmHg) until StO₂ went down to 40%. The rate of StO₂ re-ascension after cuff deflation was calculated. We also compared the first measurements of StO₂ and the rate of StO₂ re-ascension in the septic patients with those collected in 9 healthy volunteers.

Results: Overall, 115 sets of measurements were obtained in the 27 patients. The mean SAPS2, CI and MAP were 57 ± 21, 3.48 ± 1.31L/min/m² and 76 ± 18mmHg, respectively. In comparison with healthy subjects StO₂was not different in septic patients (79 ± 5%) and in healthy subjects (80 ± 12%). In contrast, the StO₂re-ascension slope was lower in septic patients (0.77 ± 0.91%.sec^-1) than in controls (1.95 ± 0.34%.sec^-1) (p=0.004). StO₂ weakly correlated with CI (r²=0.13, p<0.001) and with MAP (r²=0.05, p<0.005 ). StO₂ re-ascension slope weakly correlated with CI (r²=0.15, p<0.001) and with MAP (r²=0.21, p<001). However, CI was lower (p< 0.0001) in cases of StO₂<70 % (n=28) (CI= 2.58 ± 1.01 L/min. m2) than in cases of StO₂>70 % (n=87) (CI= 3.76 ± 1.23 L/min.m2).

Conclusion: On average, septic patients are not characterized by lower than normal StO₂. Low values of StO₂ are generally associated with low CI. Slow StO₂ re-ascension slopes after inducing transient regional using forearm cuff inflation seem to better detect functional microcirculation abnormalities in particular when StO₂ is in the normal range.