Intramuskulares pO₂-monitoring des kompartmentsyndroms - Eine experimentelle studie

Hypothesis: Measuring intracompartimental pressure is a well accepted method in evaluating a compartment syndrome, which may occur after limb ischemia followed by reperfusion. As a compartment syndrome is paralleled by a decreased microcirculation it should be possible to evaluate a compartment syndrome also by measuring intramuscular pO₂. Methods: Anesthetized rats (spontaneous breathing via tracheotomy) were subjected to infrarenal ligation of the aorta. A pressure catheter was placed subfascial in the crural muscle group of one hind limb, whereas the contralateral side was prepared with a pO₂ catheter. Besides a sham operated group, three experimental groups were subjected to either 2 hrs, 4 hrs or 6 hrs of ischemia followed by 4 hrs of reperfusion. One further group was also subjected to 4 hrs of ischemia and 4 hrs of reperfusion but received a fasciotomy at the time of reperfusion. Compartment pressure and intramuscular pO₂ were recorded every 15 min. For histological examination muscle specimen were obtained after each experiment. Results: Two hours of ischemia followed by 4 hrs of reperfusion did not result in any morphological changes and also not in any significant change in compartment pressure during both phases, whereas pO₂ significantly dropped during ischemia (from 19.0 mmHg to 3.0-5.0 mmHg) and returned to normal during reperfusion. In prolonged ischemia (4hrs) morphologically a severe interstitial edema was evident, compartment pressure increased during reperfusion (from 2.0 mmHg to 8.8 mmHg) and pO₂ dropped during ischemia down to 3.0 mmHg and did not return to normal during reperfusion (10.5 mmHg versus 19.0 mmHg normal). In case of 6 hrs ischemia, partial necrosis and only little interstitial edema were found morhologically. There was no significant change in compartment pressure throughout the study, and pO₂ remained significantly decreased even during reperfusion (2.0-3.0 mmHg). Discussion: Normal compartment pressure could mislead to false negative interpretation of compartment syndrome, whereas pO₂ clearly identifies the microcirculatory state of the muscle. Thus, intramuscular pO₂ monitoring presents a valuable method in evaluating compartment syndrome, especially in case of suspect clinical signs but normal compartment pressure.