The relationship between intracranial pressure, cerebral perfusion pressure and survival in paediatric head injured patients: what does the first 24 hours tell us?

Aim

To determine whether there is a relationship between cerebral perfusion pressure (CPP), intracranial pressure (ICP) and survival in children with severe traumatic brain injury (sTBI) in the first 6 and 24 hours after ICP monitoring.

Methods

We retrospectively reviewed the case notes of all children under the age of 16 years who were admitted to the Paediatric Intensive Care Unit in Southampton General Hospital following a head injury in whom intracranial pressure monitoring was undertaken over a 4-year period. ICP, CPP and mean arterial pressure were evaluated hourly and means were calculated for the first 6 and 24 hours after ICP monitoring. The primary outcome measure was survival and children were categorised into three groups; Group 1, overall functioning within the normal range; Group 2, survival but with some neurological impairment; and Group 3, died as a result of their injuries.

Results

Of 102 children admitted to the unit during the period of the study, following a head injury, 59 had intracranial monitors placed within the first 24 hours. Nearly two-thirds (64.7%) were male and all 59 suffered sTBI with mean (SD) admitting Glasgow Coma Scores of 8 (3). The crude mortality rate was 10.2%. When comparing the mean ICP over the first 6 hours we found a significant difference between all three groups. The mean ICPs (SD) at 6 hours were as follows; Group 1, 10.61 mmHg (5.43); Group 2, 18.57 mmHg (7.34) and Group 3, 42.88 mmHg (23.64) The mean (95% confidence interval [CI]) ICP was 7.96 mmHg (CI 1.05–14.87) lower in Group 1 than Group 2 (P < 0.05), and 24.31 mmHg (CI 13.90–34.71) lower in Group 2 than Group 3 (P < 0.05). This difference between groups was maintained at 24 hours. Mean ICPs (SD) at 24 hours; Group 1, 12.61 mmHg (5.12); Group 2, 20.35 mmHg (5.07) and Group 3, 44.69 mmHg (25.70). The mean (95% CI) ICP was 7.74 mmHg (CI 1.3–33.16) lower in Group 1 than in Group 2 (P < 0.05), and 24.34 mmHg (CI 14.31–34.35) lower in Group 2 than Group 3 (P < 0.05) at this time. There was also a significant difference in the CPP between Groups 1 and 3, and Groups 2 and 3 at both 6 and 24 hours, although no significant difference was detected between Groups 1 and 2.

Conclusion

This study suggests that in children a low ICP, in the first few hours after a sTBI, is crucial to intact survival and helps to differentiate this from a poor outcome (neurological impairment or death). CPP did not help stratify those patients who survived (Group 1 and Group 2). The question remains whether we can improve outcome with aggressive measures to reduce the ICP or increase the CPP.