Monitoring and interpretation of intracranial pressure after head injury

Abstract

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. 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. 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. 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.