Chapter

Intracranial Pressure and Brain Monitoring XIV

Volume 114 of the series Acta Neurochirurgica Supplementum pp 45-49

Date:

Trigger Characteristics of EUSIG-Defined Hypotensive Events

  • Rob DonaldAffiliated withSchool of Mathematics and Statistics, University of Glasgow Email author 
  • , Tim HowellsAffiliated withDepartment of Neurosurgery, Uppsala University Hospital
  • , Ian PiperAffiliated withDepartment of Clinical Physics, Institute of Neurological Sciences, Southern General Hospital, 1345 Govan Road
  • , I. ChambersAffiliated withDepartment of Medical Physics, James Cook University Hospital
  • , G. CiterioAffiliated withNeurorianimazione, Hospital San Gerardo
  • , P. EnbladAffiliated withDepartment of Neurosurgery, Uppsala University Hospital
  • , B. GregsonAffiliated withDepartment of Regional Medical Physics, Newcastle General Hospital
  • , K. KieningAffiliated withDepartment of Neurosurgery, Ruprecht-Karls-Universitat Hospital
  • , J. MatternAffiliated withDepartment of Neurosurgery, Ruprecht-Karls-Universitat Hospital
    • , P. NilssonAffiliated withDepartment of Neurosurgery, Uppsala University Hospital
    • , A. RagauskasAffiliated withHead of Telematics (Biomedical) Sc. Lab., Kaunas University of Technology
    • , Juan SahuquilloAffiliated withDepartment of Neurosurgery, Vall d’Hebron University Hospital
    • , R. SinnottAffiliated withDepartment of Information Systems, University of Melbourne
    • , A. StellAffiliated withNational eScience Centre, University of Glasgow

Abstract

Background: Hypotension is a recognized ­secondary insult after traumatic brain injury (TBI). There are many definitions of hypotension, an often cited example being the Brain Trauma Foundation’s current (2007) “Guidelines for the Management of Severe Traumatic Brain Injury,” which defines hypotension as systolic pressure <90 mmHg. However, this same document declares “The importance of mean arterial pressure, as opposed to systolic pressure should also be stressed, ….” Our work shows that when using the Edinburgh University Secondary Insult Grades (EUSIG) definitions, which require monitoring of both systolic and mean arterial pressures, that most hypotensive events are in fact triggered by a breach of the mean arterial level of 70 mmHg. We suggest that close monitoring of mean arterial pressure would enable clinical teams to avoid more potentially damaging hypotensive events.

Materials and Methods: An analysis of 100 patients from the Brain-IT database was performed. Using the EUSIG definitions, 2,081 events can be obtained by analyzing the systolic and mean blood pressures on a minute by minute basis. A software program was written to identify and classify the trigger pattern for each event. A categorical analysis of these triggering patterns has been carried out.

Key Results: Our analysis shows that most events are triggered by a drop in mean arterial pressure. In fact a large number of events (91%) occur where the mean arterial pressure is below the threshold limits whereas the systolic pressure does not cross the 90 mmHg limit at all.

Conclusion: We suggest that more emphasis should be placed on closely monitoring mean arterial pressure as well as systolic pressure when trying to guard against hypotensive problems in traumatically brain injured patients. In future work we will study the underlying physiological mechanisms and attempt to further classify concomitant conditions that may be contributing to the onset of a hypotensive event.

Keywords

Traumatic Brain Injury Hypotension Systolic Arterial Blood Pressure • Mean Arterial Blood Pressure Secondary Insults