Extracorporeal Membrane Oxygenation Decrease Rate Of Relaxation In Rat Skeletal Muscle

PURPOSE: Extracorporeal membrane oxygenation (ECMO) is the life-saving strategy for patients with severe respiratory or circulatory failure. ECMO induces non-physiological respiratory and circulatory changes in the whole body, which may induce functional changes in skeletal muscles. This study aimed to compare the skeletal muscle functions between ECMO and sham intervention. METHODS: The ECMO group was anesthetized with isoflurane and mechanically ventilated (FiO2 1.0). Venous and arterial lines were prepared in jugular vein and carotid artery, respectively. The right tibialis anterior (TA) muscle was excised, and the terminal tendon was connected to a strain gauge to measure muscle tension. Stimulation was performed at 5 V, 2 ms, 1 Hz, for 180 s via an electrode implanted on the muscle surface. The obtained muscle tension was sampled at 1000 Hz, and a total of 180 tension waveforms were analyzed. The rate of force development (RFD) and peak values were calculated from the tension waveforms. The maximum relaxation rate (MRR) was calculated after the peak tension was reached. Phosphorescent quenching was used to measure the partial pressure of oxygen (pO2is) in the interstitium of the TA in real-time, simultaneously with muscle tension. RESULTS: The arterial blood gas analysis results showed that the arterial oxygen pressure in the ECMO group did not differ from that in the Sham group (473 ± 33 vs. 424 ± 41 mmHg, Sham vs. ECMO). The hemoglobin level was significantly lower in the ECMO than Sham group (14.6 ± 0.4 vs. 10.5 ± 0.6 g/dL, p < 0.01). The RFD and Peak values in the ECMO group did not differ from those in the Sham group (RFD, 63.5 ± 3.2 vs. 64.5 ± 2.8 g/mg/s; Peak 0.102 ± 0.001 vs. 0.104 ± 0.001 g/mg), but MRR in the ECMO group significantly lower compared to Sham (38.0 ± 11.5 vs. 18.8 ± 5.9 g/mg/s, p < 0.01, Sham vs. ECMO). The pO2is during contraction was significantly lower in the ECMO group compared to Sham (1.2 ± 1.6 vs. 0.1 ± 0.2 mmHg, p < 0.01). CONCLUSION: These results suggest that ECMO decreased the relaxation rate of rat skeletal muscle, partially due to anemia and hypoxia.