The effects of mean arterial pressure during a critical window following acute traumatic brain injury - a survival analysis in the ProTECT cohort Open Access

Hatefi, Dustin (2011)

Permanent URL: https://etd.library.emory.edu/concern/etds/08612n598?locale=en
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Abstract


Abstract
The effects of mean arterial pressure during a critical window following acute
traumatic brain injury - a survival analysis in the ProTECT cohort

By Dustin Hatefi
Secondary insults following traumatic brain injury (TBI) are recognized as
important determinants of prognosis. The association between early systolic hypotension
and poor outcome has been established, but the role of low mean arterial pressure (MAP)
has not been well defined.
This retrospective cohort study is aimed at characterizing the effects of low MAP
expressed as proportion of total blood pressure recordings (pMAP) during a critical
window of peak edema post-TBI (days 2 and 3). Data were collected from the ProTECT
cohort, a clinical trial analyzing the safety of intravenous progesterone in the acute post-
TBI period. The pMAP data on 98 subjects were dichotomized three ways: 1) by
comparing subjects experiencing hypotension <80 mm Hg to those who did not 2) by
dividing the study population using the median as the cutoff, and 3) by evaluating the
persons in the upper tertile relative to the remainder of the sample. Data were collected
on vital status after follow up, duration of follow up, age, sex, race, Glasgow coma scale
score, injury severity score, early moderate to severe MAP hypotension (<65 mm Hg),
and progesterone allocation. Descriptive information was compiled on all variables to
evaluate for significant differences across pMAP exposure groups. Univariate analysis
was performed using Kaplan-Meier survival curves for categorical data and unadjusted
proportional hazards models for continuous data. Three multivariate proportional
hazards models for each pMAP dichotomization scheme were created, adjusting for study
covariates to obtain hazard ratios (HRs) and 95% confidence intervals (CIs). The main
outcome of interest was survival time (days).
The only significant differences were observed for early hypotension, as high
pMAP groups tended to have lower early MAPs. After adjustment, Cox regression
analysis did not reveal any significant association between pMAP and survival with HR
ranging from 1.11 to 1.45, depending on the dichotomization scheme. In contrast,
progesterone significantly decreased mortality by 81-82% in all three models.
In conclusion, the data failed to show any significant effect of cumulative mean
arterial hypotension during the two- to four-day interval post-TBI on survival in the
ProTECT cohort. Progesterone, however, did significantly improve survival.


The effects of mean arterial pressure during a critical window following acute
traumatic brain injury - a survival analysis in the ProTECT cohort

By
Dustin Hatefi
M.D., Georgetown University, 2011
B.S., Boston College, 2006
Thesis Committee Chair: Michael Goodman, MD
A thesis submitted to the Faculty of the
Rollins School of Public Health of Emory University
in partial fulfillment of the requirements for the degree of
Master of Public Health
in Epidemiology
2011

Table of Contents

I. Introduction....................................................1

II. Methods.........................................................3

III. Results..........................................................7

IV. Discussion......................................................9

V. Conclusion.....................................................11

VI. Acknowledgments..........................................12

VII. References...................................................12

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