Altered Neurocritical Care Management of Patients with Severe Traumatic Brain Injury Following Changed Positions of the Zero-Reference Points for Intracranial and Arterial Pressure Measurement.

Background: Many traumatic brain injury (TBI) treatment protocols, including the Lund concept, advocate the highest point of the subarachnoid space (typically the vertex) as the zero-reference point for intracranial pressure (ICP) and the level of the right atrium as the zero-reference point for mean arterial blood pressure (MAP). In 2017, at the Department of Neurosurgery in Lund, Sweden, the zero-reference points for ICP and MAP were both changed to the external auditory meatus (EAM), thus altering the calculated cerebral perfusion pressure (CPP) levels. We hypothesized that the ICP and MAP levels obtained from the different zero-reference points resulted in altered neurocritical care management and/or patient outcome.

Methods: We conducted a retrospective analysis of ICP, CPP, MAP, medical management, mortality, and outcome in two different patient cohorts with severe TBI treated at the Department of Neurosurgery, Skåne University Hospital, Lund, Sweden, between 2013 and 2016 and 2018 and 2022.

Results: We collected more than 31,000 measurements from 49 patients between 2013 and 2016 and 53 patients between 2018 and 2022. Age and injury severity were similar in both groups. Mortality and treatment outcome according to the Glasgow Outcome Scale - Extended were similar. Mean ICP levels were higher (p < 0.0001) after the reference point was changed to the EAM. The use of clonidine (65% vs. 49%; p = 0.17) and metoprolol (50% vs. 13%; p = 0.0002) decreased, and the use of norepinephrine increased (42% vs. 98%; p < 0.0001) after changing the reference points.

Conclusions: Higher ICP levels were observed when the reference point was changed to the EAM. The use of metoprolol was reduced, and there was a significant increase in the use of norepinephrine. These results show the impact of zero-reference point placement, which should be reported in TBI studies analyzing ICP and CPP management.