Role of mean arterial pressure in monitoring severe head injury patients at a tertiary hospital

Abstract

BACKGROUND: Maintenance of cerebral blood flow (CBF) depends on a balance between intracranial pressure (lCP) and mean arterial pressure (MAP). In traumatic head injury, ICP is raised interfering with normal-CBF. Invasive monitoring of ICP and MAP is the ideal tool for determining cerebral perfusion pressure (CPP) in severe traumatic head injury. This study aimed at establishing how noninvasive MAP measurement associated with outcome after severe traumatic brain injury and its possible role in monitoring. METHODS: This was a prospective analytical study carried out over ten month period (November 2007 to August 2008). It involved 73 patients admitted at Kenyatta National Hospital (KNH) with severe traumatic head injury (Glasgow Coma Scale scores 3-8).Their initial Blood Pressure, MAP, Injury Severity Score (lSS), plus physical and radiological / findings were recorded as were the interventions involved. They were followed up through the resuscitation phase in intensive care for 3 weeks, then wards and clinics for a maximum of 6 months. Their Glasgow Outcome Scores (GOS) were determined and associations with their MAPs determined. RESULTS: There were 6 females and 67 males all totaling to 73. Majority, 80.3% were in the age bracket 20-45 years. Most of the injuries were due to assaults followed by Road Traffic Accidents. x There was no significant association between admission MAP with age, gender, time from injury to admission, intracranial hematomas nor alcohol consumption. A low MAP «90rrunHg), low Glasgow Coma Score (3-4), and high ISS (>34 ± 2) associated with poor outcome (Severe Disability or death). Mean arterial pressure at admission did not have an association with outcome at end of follow up but there was a significant negative correlation between Injury Severity Score (lSS) and MAP. CONCLUSIONS: • Majority of our patients (over 60%) presented with low MAP «90rrunHg) hence need for intervention. Admission Glasgow coma score (GCS) and ISS were better predictors of outcome than MAP. • The longer the time to admission, the greater the likelihood to capture patients with a low MAP. • Improving GCS and GOS associated positively with increasing MAP although no threshold effect was observed. The role of non invasive MAP in monitoring severe head injury is evident when combined with ISS and GCS in our set up.