The prevention and treatment of secondary insults to the brain of systemic origin in severely head injured patients remain of utmost importance. Head injury remains the leading cause of traumatic death, being responsible for 50-60% of fatalities. Head-injured patients not only suffer from the primary injury at the time of trauma, but also from the secondary, largely ischaemic, brain damage that occurs later. Some of these insults are of extracranial origin (or systemic), such as arterial hypotension, hypoxaemia, hypercarbia and anaemia. Their impact on mortality and morbidity is extremely high and requires greater efforts in improving the care of head-injured patients. Systemic insults occur either before the patient reaches hospital or during interfacility transfer or, in a surprisingly large number of cases, within hospital during emergency procedures, intrahospital transport or during their stay in intensive care units. Hypoxaemia, although quite easy to treat, is still common. This calls for better and earlier protection of the airway, more systematic administration of oxygen to trauma patients and wider use of pulse oximetry. Arterial hypotension has even more dramatic consequences in severe head injury. Recent studies indicate that short episodes of hypotension may induce severe brain ischaemia, that will be present even after complete systemic haemodynamic restoration. The treatment of hypotensive episodes should be immediate and aggressive. In some circumstances, restoration of an adequate cerebral perfusion pressure may not be obtained sufficiently rapidly with fluids alone and may require early use of vasopressors. Optimal haemodynamic resuscitation of the trauma patient with haemorrhagic hypotension and severe head injury remains a special challenge.(ABSTRACT TRUNCATED AT 250 WORDS)