Advanced supportive therapy at the site of the accident, associated with direct transfer to a trauma centre increases survival and reduces morbidity rates. Patients with severe head injury, especially those with multiple injuries, often arrive in the emergency department with potentially causes of serious secondary systemic insults to the already injured brain, such as acute anemia (Hematocrit < or = 30%), hypotension (systolic arterial pressure (Pasys) < or = 95 mmHg, 12.7 kPa), hypercapnia (Paco2 > or = 45 mmHg, 6 kPa) and/or hypoxemia (Pao2 < or = 65 mmHg, 8.7 kPa). The incidence of such insults and their impact on mortality were studied in a group of 51 consecutive adults suffering from non penetrating severe head injury (Glasgow score < or = 8, mean age 31 +/- 17 yrs) rescued by a medicalized helicopter. Each patient received medical care on the site of the accident by an anaesthesiologist of a university hospital (UH) complying with an advanced trauma life support protocol including intubation, hyperventilation with FiO2 = 1, restoration of an adequate Pasys and direct transportation to the UH. Mean delay from call to arrival of the rescue team on the site was 15 +/- 5 min. Mean scene time was 32 +/- 10 min in cases not requiring extrication. Nineteen patients (Group I) were admitted without secondary systemic insults to the brain, 13 with isolated head injury, and 6 with multiple injuries, with a low Glasgow Outcome Score (GOS 1-3) of 42% at 3 months. In 32 patients (Group II), despite advanced supportive measures at the scene of the accident and during transportation, one or more secondary systemic insults to the brain were detected upon arrival at the emergency room, one with isolated head injury, 31 with multiple injuries, with a bad GOS of 72% at 3 months. We conclude that: 1) advanced trauma life support prevents from secondary systemic insults in the great majority of isolated severe head injured patients. 2) secondary systemic insults to the already injured brain are frequent in patients with multiple injuries and are difficult to avoid despite rapid aeromedical trauma care, 3) secondary systemic insults to the brain have a catastrophic impact on the outcome of severely head injured patients.