EPIDERMAL LIPIDS AND THE NATURAL-HISTORY OF HYDROFLUORIC-ACID (HF) INJURY

To explain several fortuitous observations, we hypothesized that there is a naturally occurring lipid 'barrier' to HF injury in guinea-pig s kin and sought to characterize both the barrier and its role in the na tural history of such injuries. Under anaesthesia, the dorsal trunk sk in of groups of guinea-pigs was gently clipped of hair, washed with ch loroform, soap and water, acetone or nothing (controls), and examined histologically for the presence of neutral lipid. Thereafter, in anima l groups similarly washed, 1.5 in x 1.5 in (38 mm x 38 mm)areas were e xposed to 40 percent HF for up to 50 min and. (a) mean percentages of exposed areas with gross necrosis 5 days postinjury plotted on dose-re sponse curves; or (b) more than 4 h after exposure to HF, intra-aortic India ink was injected and skin specimens examined to discern depth o f ischaemia and necrosis. In contrast to controls, washing reduced neu tral lipid in epidermis and significantly (at P < 0.001) increased sus ceptibility to injury by HF. With very rare (but interesting) exceptio ns, HF injury was found to be full thickness in depth with ischaemia a nd coagulative necrosis. In this study, development of guinea-pig skin necrosis due to HF was typically an 'all-or-nothing' 'barrier-penetra tion' phenomenon relating as much to the integrity of an epidermal lip id barrier as to the duration and intensity of noxious exposure.