Abstract 11551: Posterior Cerebral Autoregulation is More Vulnerable to Hypotension as Compared to Anterior Cerebral Autoregulation in Older Adults
Differences in regional cerebral autoregulation (CA) may be responsible for localized vulnerability of cerebral ischaemia. This study was aimed to assess the anterior and posterior CA seperately and compare them in older adults. Twenty-five healthy older subjects (13 females, 68 ± 6 yr) participated. Mean arterial pressure (MAP) was decreased stepwise by intravenous infusion of sodium nitroprusside and then increased by phenylephrine. Cerebral blood flow (CBF) in the internal carotid and vertebral arteries (ICA and VA) was measured using color-coded duplex ultrasonography. Cerebrovascular resistance (CVR) was calculated as MAP/CBF. All measurements were normalized as percentage changes from baseline (Δ, %), and CA was assessed by linear regression analysis of changes [[Unable to Display Character: ▵]]CBF and [[Unable to Display Character: ▵]]CVR in response to [[Unable to Display Character: ▵]]MAP. The range of [[Unable to Display Character: ▵]]MAP induced by drug infusion was from -26% to 36% relative to baseline. During hypertension, the linear regression slopes of [[Unable to Display Character: ▵]]CBF and [[Unable to Display Character: ▵]]CVR to [[Unable to Display Character: ▵]]MAP showed no difference between ICA and VA (CBF slope, ICA -0.136 ± 0.101 vs. VA -0.299 ± 0.152, P > 0.05; CVR slope, ICA 1.238 ± 0.131 vs. VA 1.605 ± 0.240, P > 0.05), indicating intact CA. However, during hypotension, CA was less effective in VA as compared to ICA (CBF slope, VA 0.654 ± 0.184 vs. ICA 0.074 ± 0.193, P < 0.05; CVR slope, VA 0.394 ± 0.206 vs. ICA 0.970 ± 0.182, P < 0.05) (Figure 1). In older adults, cerebral autoregulation in the anterior cerebral territory (supplied mainly by the ICA) is intact during both hypo and hypertension. However, cerebral autoregulation in the posterior cerebral territory (supplied mainly by the VA) appears to be less effective during hypotension, which may make older adults more prone to vertebro-basilar ischaemia.
Figure 1. Scatter plots and linear regressions of ΔCBF (upper row) and ΔCVR (bottom row) relative to baseline during decreases and increases in mean arterial pressure (MAP) at the internal carotid artery (ICA, left column) and vertebral artery (VA, right column) .
- © 2013 by American Heart Association, Inc.