Monitoring and interpretation of intracranial pressure after head injury

Abstract

Objective: To investigate the relationships between long-term computer-assisted monitoring of intracranial pressure (ICP) and indices derived from its waveform versus outcome, age, and sex.

Materials and methods: From 1992 to 2002, 429 sedated and ventilated head-injured patients were continuously monitored. ICP and arterial blood pressure (ABP) were recorded directly and stored in bedside computers. Additional calculated variables included: 1) Cerebral perfusion pressure (CPP) = ABP - ICP; 2) a PRx calculated as a moving correlation coefficient between slow waves (of periods from 20 seconds to 3 minutes) of ICP and ABP.

Results: Fatal outcome was associated with higher ICP (p < 0.000002), worse PRx (p < 0.0006), and lower CPP (p < 0.001). None of these parameters differentiated severely disabled patients from patients with a favorable outcome. Higher average ICP, lower CPP, worse outcome, and worse pressure reactivity were observed in females than in males (age-matched). Worse outcome, lower mean ICP, worse PRx, and higher CPP were significantly associated with the older age of patients.

Conclusion: High ICP and low PRx are strongly associated with fatal outcome. There is a considerable heterogeneity amongst patients; optimization of care depends upon observing the time-trends for the individual patient.