Effects of brief ischemia on oxygen consumption, tissue oxygenation, and blood flow during recovery from ischemia in rat skeletal muscle (674.13)

Abstract

The effects of brief ischemia (5, 15, 30, and 60 s duration; Isch) on interstitial PO2 (PISFO2), arteriolar PO2 (PaO2), blood flow (Q) and O2 consumption (VO2) during the recovery period was observed in exteriorized spinotrapezius muscles of 29 male Sprague‐Dawley rats (284 ± 20 g) for intravital microscopy. Phosphorescence quenching microscopy was used to obtain PISFO2, PaO2 and VO2. Arteriolar blood flow was calculated from arteriolar diameter and centerline RBC velocity obtained from an Optical Doppler Velocimeter. Ischemia was initiated by rapidly pressurizing an airbag attached to the microscope objective for a selected ischemic duration. The average baseline value of arteriolar blood flow was 5.8±0.8 µl/min; as expected, reactive hyperemia was observed during the recovery from Isch. Flow recovery (dQ/dt) was fastest [3.88±0.64 (µl·min‐1)/s] after 60 seconds of Isch. Average baseline PISFO2 was 62±4 mmHg; PISFO2 decreased to 75%, 34%, 10% and 2% of baseline following 5, 15, 30 and 60 s of Isch, respectively. Up to 30 s of ischemia, the rate of recovery of PISFO2 steadily increased as the ischemic duration increased; however, it dropped off following 60 s of ischemia. The drop in the rate of recovery of PISFO2 despite an increase in flow recovery following 60 s of ischemia is suggestive of a period of imbalance during which the rate at which the tissue was consuming oxygen temporarily exceed the rate at which it could be supplied. The rate of recovery of PISFO2 was fastest (4.2±0.7 mmHg/s) following 30 s of Isch. Average baseline VO2 was 120±19 nl O2/cm3·s and it increased above baseline during the early part of the recovery period. The time course of recovery of PISFO2 represented a balance between O2 delivery, proportional to local arteriolar blood flow, and local VO2. Grant Funding Source: NHLBI grant HL18292