Simultaneous measurements of subcutaneous and intramuscular tissue pO₂ in critically ill patients

The primary goal in the treatment of patients with shock is to restore the tissue perfusion and oxygenation. Clinical endpoints of resuscitation (i.e. bloodpressure, heart rate, urine output and oxygen saturation) give an incomplete or even misleading picture. Tissue oxygen tension (ptO₂) reflecting tissue oxygenation may be a useful endpoint; however, in the clinical setting ptO₂ measurements subcutaneously (ptO₂sc) and in muscle (ptO₂im) are both used, although a comparative study has never been performed.

In 18 critically ill patients ptO2sc and ptO2im were simultaneously and continuously measured using polarographic Clark-type electrodes (LICOX Catheter Measurement System, GMS), placed subcutaneously and in the m. biceps brachii of the upper arm.

Eighteen men and two women with septic shock (n = 8), severe sepsis (n = 5), sepsis (n = 1), polytrauma (n = 3) and nonseptic acute respiratory distress syndrome (ARDS) (n = 1) were included. The median age was 60 years (range 22–80 years), and the median APACHE score on admission was 18 (range 10–31). The median duration of tissue oxygen measurements was 5 days (range 2–8 days). Median ptO₂ values of different groups are presented in Table 1. Wilcoxon's signed rank test was used to compare changes within the group and a one-way analysis of variance (ANOVA) was used for comparison between the variation of ptO2 values within groups. Although differences between ptO₂sc and ptO₂im were found in individual patients and between goups, a clear pattern could not be established. Measurement of tissue oxygenation can be performed in subcutaneous tissue as well as in muscle tissue.

Table 1