Hypothermia does not improve cerebral autoregulation after traumatic brain injury (TBI) in rats

Eric A. Bedell, Douglas Dewitt, Donald Prough

Research output: Contribution to journalArticle

Abstract

Introduction: Mild hypotension worsens outcome after human TBI (1), perhaps because of unpaired cerebral pressure autoregulation (2). Hypothermia improved outcome after TBI in animals (3) and humans (4), but the mechanisms are unclear. We evaluated the effects of hypothermia on autoregulation after fluid percussion injury (FPI) in rats. Methods: In an approved protocol, 24 Sprague-Dawley rats were mechanically ventilated with isoflurane in air: O2 and prepared for lateral FPI and cerebral laser Doppler flowmetry (LDF) (5). The abdominal aorta was cannulated and connected to a reservoir. PaCO2 was maintained at 38mmHg. Under 1% isoflurane, autoregulation was assessed before or 30 and 60 min after FPI by measuring LDF at randomly ordered blood pressures of 100, 80, 60, and 40 mm Hg. After baseline measurements at 37°C (temporalis), animals were randomized to 37°C without FPI (Control 37; n=7), 37°C with FPI of 1.8 atm (FPI 37; n=7), 32°C without FPI (Control 32; n=7), 32°C with FPI (Pre-FPI 32; n=7), or 37°C with FPI and immediate cooling to 32°C (Post-FPI 32, n=7). Results: PaCO2, PaO2, pH, hematocrit, and temperature were controlled as planned. No significant difference in %CBF change was seen between trauma groups with normothermia or hypothermia at 30 and 60 min. (Figure Presented) Conclusions: Hypothermia before or after brain trauma does not improve autoregulation after FPI. Better outcomes after FPI with hypothermia appear to be related to mechanisms other than improved cerebral circulatory control.

Original languageEnglish (US)
JournalCritical Care Medicine
Volume27
Issue number1 SUPPL.
StatePublished - 1999

Fingerprint

Percussion
Hypothermia
Homeostasis
Wounds and Injuries
Laser-Doppler Flowmetry
Isoflurane
Traumatic Brain Injury
Abdominal Aorta
Hematocrit
Hypotension
Sprague Dawley Rats

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

Cite this

Hypothermia does not improve cerebral autoregulation after traumatic brain injury (TBI) in rats. / Bedell, Eric A.; Dewitt, Douglas; Prough, Donald.

In: Critical Care Medicine, Vol. 27, No. 1 SUPPL., 1999.

Research output: Contribution to journalArticle

@article{79abad1bc8e444b7a563845fece35f2e,
title = "Hypothermia does not improve cerebral autoregulation after traumatic brain injury (TBI) in rats",
abstract = "Introduction: Mild hypotension worsens outcome after human TBI (1), perhaps because of unpaired cerebral pressure autoregulation (2). Hypothermia improved outcome after TBI in animals (3) and humans (4), but the mechanisms are unclear. We evaluated the effects of hypothermia on autoregulation after fluid percussion injury (FPI) in rats. Methods: In an approved protocol, 24 Sprague-Dawley rats were mechanically ventilated with isoflurane in air: O2 and prepared for lateral FPI and cerebral laser Doppler flowmetry (LDF) (5). The abdominal aorta was cannulated and connected to a reservoir. PaCO2 was maintained at 38mmHg. Under 1{\%} isoflurane, autoregulation was assessed before or 30 and 60 min after FPI by measuring LDF at randomly ordered blood pressures of 100, 80, 60, and 40 mm Hg. After baseline measurements at 37°C (temporalis), animals were randomized to 37°C without FPI (Control 37; n=7), 37°C with FPI of 1.8 atm (FPI 37; n=7), 32°C without FPI (Control 32; n=7), 32°C with FPI (Pre-FPI 32; n=7), or 37°C with FPI and immediate cooling to 32°C (Post-FPI 32, n=7). Results: PaCO2, PaO2, pH, hematocrit, and temperature were controlled as planned. No significant difference in {\%}CBF change was seen between trauma groups with normothermia or hypothermia at 30 and 60 min. (Figure Presented) Conclusions: Hypothermia before or after brain trauma does not improve autoregulation after FPI. Better outcomes after FPI with hypothermia appear to be related to mechanisms other than improved cerebral circulatory control.",
author = "Bedell, {Eric A.} and Douglas Dewitt and Donald Prough",
year = "1999",
language = "English (US)",
volume = "27",
journal = "Critical Care Medicine",
issn = "0090-3493",
publisher = "Lippincott Williams and Wilkins",
number = "1 SUPPL.",

}

TY - JOUR

T1 - Hypothermia does not improve cerebral autoregulation after traumatic brain injury (TBI) in rats

AU - Bedell, Eric A.

AU - Dewitt, Douglas

AU - Prough, Donald

PY - 1999

Y1 - 1999

N2 - Introduction: Mild hypotension worsens outcome after human TBI (1), perhaps because of unpaired cerebral pressure autoregulation (2). Hypothermia improved outcome after TBI in animals (3) and humans (4), but the mechanisms are unclear. We evaluated the effects of hypothermia on autoregulation after fluid percussion injury (FPI) in rats. Methods: In an approved protocol, 24 Sprague-Dawley rats were mechanically ventilated with isoflurane in air: O2 and prepared for lateral FPI and cerebral laser Doppler flowmetry (LDF) (5). The abdominal aorta was cannulated and connected to a reservoir. PaCO2 was maintained at 38mmHg. Under 1% isoflurane, autoregulation was assessed before or 30 and 60 min after FPI by measuring LDF at randomly ordered blood pressures of 100, 80, 60, and 40 mm Hg. After baseline measurements at 37°C (temporalis), animals were randomized to 37°C without FPI (Control 37; n=7), 37°C with FPI of 1.8 atm (FPI 37; n=7), 32°C without FPI (Control 32; n=7), 32°C with FPI (Pre-FPI 32; n=7), or 37°C with FPI and immediate cooling to 32°C (Post-FPI 32, n=7). Results: PaCO2, PaO2, pH, hematocrit, and temperature were controlled as planned. No significant difference in %CBF change was seen between trauma groups with normothermia or hypothermia at 30 and 60 min. (Figure Presented) Conclusions: Hypothermia before or after brain trauma does not improve autoregulation after FPI. Better outcomes after FPI with hypothermia appear to be related to mechanisms other than improved cerebral circulatory control.

AB - Introduction: Mild hypotension worsens outcome after human TBI (1), perhaps because of unpaired cerebral pressure autoregulation (2). Hypothermia improved outcome after TBI in animals (3) and humans (4), but the mechanisms are unclear. We evaluated the effects of hypothermia on autoregulation after fluid percussion injury (FPI) in rats. Methods: In an approved protocol, 24 Sprague-Dawley rats were mechanically ventilated with isoflurane in air: O2 and prepared for lateral FPI and cerebral laser Doppler flowmetry (LDF) (5). The abdominal aorta was cannulated and connected to a reservoir. PaCO2 was maintained at 38mmHg. Under 1% isoflurane, autoregulation was assessed before or 30 and 60 min after FPI by measuring LDF at randomly ordered blood pressures of 100, 80, 60, and 40 mm Hg. After baseline measurements at 37°C (temporalis), animals were randomized to 37°C without FPI (Control 37; n=7), 37°C with FPI of 1.8 atm (FPI 37; n=7), 32°C without FPI (Control 32; n=7), 32°C with FPI (Pre-FPI 32; n=7), or 37°C with FPI and immediate cooling to 32°C (Post-FPI 32, n=7). Results: PaCO2, PaO2, pH, hematocrit, and temperature were controlled as planned. No significant difference in %CBF change was seen between trauma groups with normothermia or hypothermia at 30 and 60 min. (Figure Presented) Conclusions: Hypothermia before or after brain trauma does not improve autoregulation after FPI. Better outcomes after FPI with hypothermia appear to be related to mechanisms other than improved cerebral circulatory control.

UR - http://www.scopus.com/inward/record.url?scp=33750810190&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33750810190&partnerID=8YFLogxK

M3 - Article

VL - 27

JO - Critical Care Medicine

JF - Critical Care Medicine

SN - 0090-3493

IS - 1 SUPPL.

ER -