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

Microvascular Dysfunction

Effects of activated protein C on microcirculation assessed by near infrared spectroscopy

Georger JF, Chaari A, Richard C, Teboul JL. Int Care Med. 2008;34(Supp 1):S256. Abstract 1004.

Introduction: The near infrared spectroscopy (NIRS) assesses the haemoglobin saturation in the tissue (StO₂). Induction of transient ischemia followed by hyperaemia (forearm occlusion and release) provides additional information on the ability of microvessels to be recruited through the analysis of the StO₂ re-ascension slope. Activated protein C (APC) is an anti-thrombotic and anti-inflammatory agent used as an adjuvant therapy of patients with septic shock. One previous study showed an improved sublingual microperfusion with APC (1).

Objective: To examine if APC was able to affect microcirculation assessed by NIRS parameters in septic shock patients.

Methods: We included 11 patients with septic shock and at least two organs failures considered for administration of APC and equipped with a PiCCO’’ monitoring system. The thenar muscle StO₂ was continuously measured with Inspectra’’ model 650 (Hutchinson Technology) before and during pneumatic arm cuff inflation (until StO₂ by 40% is reached) and after deflation, which allowed calculating the StO₂ re-ascension slope. Mean arterial pressure (MAP), cardiac index (CI), central venous oxygen saturation (ScvO2), dose of norepinephrine (NE) and StO₂ measurements were performed before and 4 h after starting APC infusion (24 µg/kg/h). We also collected MAP, StO₂ and StO₂ re-ascension slope in 15 healthy volunteers.

Results: In healthy volunteers the MAP was 89 mmHg (68–101), StO₂ was 82% (75–90) and re-ascension slope was 2.29%/s (1.46–3.36). APC increased StO₂ from 77 (65–90) to 82% (67–92) (p<0.05) and the re-ascension slope from 1.5 (0.62–3.35) to 1.9 %/s (0.84–3.00) (p<0.05). APC decreased the NE dose from 2.5 (0.5–9.5) to 2 mg/h (0.5–8.0) (p\0.05). The other studied parameters were not changed by APC: PAM from 80 (73–87) to 86 mmHg (71–111), CI from 3.2 (1.0–5.3) to 3.0 L/min/m2 (1.3–5.3) and ScvO2 from 72 (50–81) to 70% (55–81).

Conclusion: In septic shock patients with at least two organs failures, the APC infusion resulted in an increase in StO₂ and in the StO₂ re-ascension slope (4 h after starting the infusion) despite the absence of any change in CI and MAP. This suggests a proper effect of APC on the thenar muscle microcirculation.

Reference(s): 1 De Backer D et al, Crit Care Med 2006.