Most authorities in the field of trauma recommend that seriously injured patients be transported directly to a regional trauma center, even if it requires bypassing nearby community hospitals. The purpose of our study was to examine the relationship between the survival rates of patients with presumed hemorrhagic shock due to penetrating injuries and the total prehospital time required to manage and deliver those patients to a single regional trauma center in a large urban area. During a 30-month-period, 498 consecutive victims of penetrating injury, presenting in the field with a systolic blood pressure of 90 mm Hg or less and transported to a single regional trauma center, were prospectively evaluated in terms of age; initial prehospital trauma score; injury severity score (ISS); TRISS probability of survival; response, scene, transport, and total prehospital times; and survival (discharge from hospital). All patients were managed and transported by a single urban paramedic service that has a fairly uniform response time (5.3 +/- 3 min) throughout its entire service area. The response area is spread out over an approximately 1,000 square-mile region, and transport times to the regional trauma center can exceed a half hour. The total prehospital time (TPT) was calculated as the time elapsed from the receipt of the emergency call to the time of arrival at the regional trauma center. Patients arbitrarily were categorized into four subsets according to the initial prehospital trauma score (1, 2 to 6, 7 to 11, 12 to 15). Patients also were analyzed in terms of four incremental groups of increasing TPT (0-20, 21-30, 31-40, greater than 40 min).(ABSTRACT TRUNCATED AT 250 WORDS)