Secondary insults in severe head injury--do multiply injured patients do worse?

Abstract

Objectives: To study the occurrence of secondary insults and the influence of extracranial injuries on cerebral oxygenation and outcome in patients with closed severe head injury (Glasgow Coma Scale score < or =8).

Design: Two-year prospective, clinical study.

Setting: Two intensive care units in a level III trauma center.

Patients: We studied 119 patients. Eighty patients had severe head injury and were divided into two categories: "isolated" severe head injury patients (n = 36, Injury Severity Score <30), and severe head injury patients with associated extracranial injuries (n = 44, Injury Severity Score >29). Thirty-nine patients with extracranial injuries and no head injury served as the control group.

Interventions: After patients were admitted to the intensive care unit, we began continuous multimodal cerebral monitoring of intracranial pressure, mean arterial blood pressure, cerebral perfusion pressure, end-tidal Co2, brain tissue Po2 (Licox), jugular bulb oxyhemoglobin saturation in severe head injury patients, and mean arterial blood pressure in the control group. Targets of management included intracranial pressure <20 mm Hg, cerebral perfusion pressure >60 mm Hg, Paco2 > 30 mm Hg, control of cerebral oxygenation, and delayed surgery for non-life-threatening extracranial lesions.

Measurements and main results: Data were analyzed for critical thresholds. The occurrence of secondary insults (intracranial pressure >20 mm Hg, mean arterial blood pressure <70 mm Hg, cerebral perfusion pressure <60 mm Hg, end-tidal Co2 <30 torr, brain tissue Po2 <10 torr, jugular bulb oxyhemoglobin saturation <50%) was comparable in patients with isolated severe head injury and those with severe head injury with associated extracranial lesions (Abbreviated Injury Scale score < or =5). The duration of intracranial hypertension and arterial hypotension significantly correlated with an unfavorable outcome, independent of the Injury Severity Score. In patients with severe head injury, 1-yr outcome was 29% dead or vegetative, 17% severely disabled, and 54% moderate or good outcome. This was similar to patients with severe head injury and extracranial injuries (31% dead or vegetative, 14% severely disabled, and 56% moderate or good outcome) and was independent of the Injury Severity Score. Patients with no head injury had less secondary insults (mean arterial blood pressure <70 mm Hg, p <.01) and a better outcome compared with both severe head injury groups (p <.044).

Conclusions: In patients with severe head injury who have targeted management including intracranial pressure- and cerebral perfusion pressure-guided therapy and delayed surgery for extracranial lesions, the occurrence of secondary insults in the intensive care unit and long-term neurological outcome were comparable and independent of the presence of extracranial lesions (Abbreviated Injury Severity level < or =5). A severe head injury is still a major contributor predicting an unfavorable outcome in multiply injured patients.