Gastrointestinal blood loss associated with running a marathon.

Gastrointestinal bleeding has been observed in long-distance runners. We prospectively studied participants of the Eighth Annual Marine Corps Marathon to determine the incidence of gastrointestinal blood loss associated with long-distance running. Of 600 runners contacted, 125 (21%) returned a questionnaire as well as pre- and postmarathon stool specimens. Stool specimens converted from Hemoccult negative to positive in 29/125 (23%) of the participants, indicating that running the marathon was associated with gastrointestinal blood loss (P less than 0.001). The incidence of this conversion (negative to positive) was significant for both males (N = 68, P less than 0.001) and females (N = 57, P less than 0.05). Gastrointestinal bleeding appeared to be independent of age, race time, abdominal symptoms, and the recent ingestion of aspirin, vitamin C, or steak.

Functional injury of vein graft endothelium. Role of hypothermia and distention.

The cause of endothelial injury during vein harvesting and preservation is complex. Hypothermia is thought necessary to preserve cell viability but has been implicated in morphologic injury to the endothelium. This study explored the effect of temperature on preserving endothelial function using prostacyclin production as a metabolic marker. Canine veins were atraumatically excised and matched segments were stored at three temperatures using either nutrient medium or heparinized saline. After storage, endogenous production of prostacyclin by the luminal surface of each vein was collected in a closed perfusion system at 37 degrees C and assayed by radioimmunoassay. Optimal prostacyclin production was observed in veins stored in tissue culture medium at normothermia. Preservation of normal endothelial function may require revision of traditional vein graft-harvesting techniques.