Acute hypercarbia increases the lower limit of cerebral blood flow autoregulation in a porcine model

Objectives: In the present study, our objective was to determine if hypercarbia would alter cerebral blood flow (CBF) autoregulation and reduce the ability of cerebrovascular reactivity monitoring to identify the lower limit of cerebrovascular autoregulation (LLA). Methods: Anaesthetised juvenile pi...

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Bibliographic Details
Published in:Neurological research (New York) 2016-03, Vol.38 (3), p.196-204
Main Authors: Nusbaum, Derek M., Brady, Kenneth M., Kibler, Kathleen K., Blaine Easley, Ronald
Format: Article
Language:English
Subjects:
Animals
Blood Flow Velocity - drug effects
Blood Gas Analysis
Blood Pressure - drug effects
Carbon Dioxide - pharmacology
Cerebral Blood Volume - drug effects
Cerebrovascular Circulation - drug effects
Cerebrovascular Circulation - physiology
Cerebrovascular reactivity
Homeostasis - drug effects
Homeostasis - physiology
Hypercarbia
Intracranial pressure
Intracranial Pressure - drug effects
Laser-Doppler Flowmetry
Lower limit
Models, Animal
Monitoring, Physiologic
Near-infrared spectroscopy
ROC Curve
Static rate of autoregulation
Swine
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Summary:Objectives: In the present study, our objective was to determine if hypercarbia would alter cerebral blood flow (CBF) autoregulation and reduce the ability of cerebrovascular reactivity monitoring to identify the lower limit of cerebrovascular autoregulation (LLA). Methods: Anaesthetised juvenile pigs were assigned between two groups: normocarbia (control group, n = 10) or hypercarbia [high carbon dioxide (CO 2 ) group, n = 8]. Normocarbia subjects were maintained with an arterial CO 2 of 40 Torr, while the hypercarbia subjects had an increase of inspired CO 2 to achieve an arterial pCO 2 of >80 Torr. Gradual hypotension was induced by continuous haemorrhage from a catheter in the femoral vein, and the LLA was determined by monitoring cortical laser Doppler flux (LDF). Vascular reactivity monitoring was performed using the pressure reactivity index (PRx) and haemoglobin volume index (HVx). Results: There were no sustained differences in ICP between groups. Autoregulation was present in both groups, despite elevation in pCO 2 .The control group had an average LLA of 45 mmHg (95% CI: 43-47 mmHg) and the high CO 2 group had a LLA of 75 mmHg (95% CI: 73-77 mmHg). The detected LLA for each subject correlated with the level of pCO 2 (spearman R = 0.8243, P 
ISSN:0161-6412
1743-1328
DOI:10.1179/1743132815Y.0000000094