EXPERIMENTAL ISCHEMIC NEUROPATHY - SALVAGE WITH HYPERBARIC OXYGENATION

Hyperbaric oxygenation is effective in augmenting the delivery of oxyg en to tissue, but also causes oxidative stress. As part of our focus o n improving peripheral nerve salvage from ischemic fiber degeneration, we evaluated whether hyperbaric oxygenation rescues peripheral nerve, rendered ischemic by microembolization, from ischemic fiber degenerat ion. The supplying arteries of rat sciatic nerve were embolized with m icrospheres of 14 mu m diameter at moderate (2 x 10(6)) and high (5.6 x 10(6)) doses. Rats were randomized to receive hyperbaric oxygenation treatment (2.5 arm 100% oxygen for 2 hours/day for 7 days beginning w ithin 30 minutes of ischemia), or room air. End points for the emboliz ed limb were (If behavioral scores (0-11 in increasing levels of limb function), (2) nerve action potential of sciatic-tibial nerve, (3) ner ve blood flow, and (4) histological grade as percentage of fibers unde rgoing ischemic fiber degeneration (0 = <5%; 1 = 5-25%; 2 = 26-50%; 3 = 51-75%; 4 = >76%). Nerve blood flow and nerve action potential were uniformly absent and more than 90% of fibers had degenerated in both c ontrol and treatment groups receiving high doses. Control and treatmen t groups receiving moderate doses were well matched by level of ischem ia (8.5 +/- 0.3 [N = 18] vs 7.7 +/- 0.4 ml/100 gm/min [N = 18], p > 0. 05) but: were significantly different by behavior score (5.6 +/- 0.7 v s 9.2 +/- 0.5 [N = 19], p < 0.001), nerve action potential (1.4 +/- 1. 0 vs 3.9 +/- 0.5 [N = 6], p < 0.05), and histology (2.4 +/- 0.4 [N = 5 ] vs 0.8 +/- 0.5 [N = 4], p < 0.05). On single teased fiber evaluation , the predominant abnormality was E (axonal degeneration). We conclude that hyperbaric oxygenation will effectively rescue fibers from ische mic fiber degeneration, providing the ischemia is not extreme.