The synergistic effect of sympathectomy and hyperbaric oxygen exposure on transcutaneous Po-2 in healthy volunteers

The benefit of hyperbaric oxygen (HBO2) exposure is dependent on the oxygen delivery. Such benefit may be limited by the fact that hyperoxia causes va soconstriction and decreases blood flow. The aim of this study was to deter mine whether regional sympathectomy attenuates this vasoconstriction respon se and thus improves oxygen delivery. In a double-blinded manner, healthy v olunteers were subjected to HBO2 in a monoplace chamber on two occasions se parated by at least 1 wk. Transcutaneous oxygen (tcPO(2)) and carbon dioxid e (tcPCO(2)) on the forearm were monitored continuously, and blood flow in the axillary artery was measured using angiodynography before and after exp osure to HBO2. During one visit, each volunteer received a sympathetic bloc k to the upper extremity by an injection of lidocaine into the brachial ple xus at the axilla. During a second visit, the volunteer received a placebo injection of isotonic sodium chloride solution into the brachial plexus of the same side. Skin temperature was recorded on the back of the hand. All s ubjects exhibited a small but significant increase in skin temperature (2.5 %) and in upper limb blood flow (23%) (P < 0.05%) after sympathectomy, but not after isotonic sodium chloride solution injection. Sympathectomy increa sed tcPO(2) marginally while in room air. However, during HBO,, tcPO(2) was substantially and significantly higher (409.8 +/- 98.8 mm Hg) after sympat hectomy compared with that after isotonic sodium chloride solution injectio n (171.3 +/- 38.1 mm Hg). tcPCO(2) did not change significantly after sympa thectomy or during HBO2. Thus, sympathectomy presumably improved oxygen del ivery by preventing vasoconstriction during hyperoxia. The results suggest that sympathectomy may be a useful adjunct to HBO2 therapy in patients in w hom vascular resistance is increased because of sympathetic tone or hyperox ia. Implications: Sympathetic nerve block of the extremities markedly enhan ces tissue oxygen delivery during hyperbaric oxygen treatment. Sympathectom y may be a beneficial adjunct treatment to hyperbaric oxygen in peripheral vascular insufficiency.