TY - JOUR
T1 - Influence of baroreflex-mediated tachycardia on the regulation of dynamic cerebral perfusion during acute hypotension in humans
AU - Ogoh, S.
AU - Lucas, S.J.
AU - Tzeng, Y.-C.
AU - Galvin, S.D.
AU - Ainslie, P.N.
PY - 2010/1/1
Y1 - 2010/1/1
N2 - The effect of acute arterial baroreflex dysfunction on cerebral autoregulation (CA) in otherwise healthy humans is unknown. We identified dynamic CA with and without arterial baroreflex-mediated tachycardia and consequent changes in cardiac output during acute hypotension whilst continuously monitoring changes in middle cerebral artery mean blood velocity (MCA V). Acute hypotension was induced in nine healthy subjects (mean ±s.d.; 26 ± 3 years) by releasing bilateral thigh cuffs after 6 min of supra-systolic resting ischaemia. Hypotension was induced before and after sympathetic blockade (β-1 receptors), and combined sympathetic-cholinergic blockade. That sequential bolus injections of sodium nitroprusside (50 μg), followed 60 s later by phenylephrine hydrochloride (50 μg), elicited <5 beats min change in heart rate was verified to confirm that full cardiac autonomic blockade was achieved. Thigh cuff release elicited a transient drop in mean arterial pressure and resultant tachycardia. This tachycardic response was diminished in full cardiac blockade (vs. control, P= 0.029; vs.β-1 adrenergic blockade, P= 0.031). Dynamic CA was also attenuated in the full blockade condition compared to both control (P= 0.028) and β-1 adrenergic blockade conditions (P= 0.015), and was related with the attenuated tachycardia response (P= 0.015). These data indicate an important role of the cardiac baroreflex in dynamic CA.
AB - The effect of acute arterial baroreflex dysfunction on cerebral autoregulation (CA) in otherwise healthy humans is unknown. We identified dynamic CA with and without arterial baroreflex-mediated tachycardia and consequent changes in cardiac output during acute hypotension whilst continuously monitoring changes in middle cerebral artery mean blood velocity (MCA V). Acute hypotension was induced in nine healthy subjects (mean ±s.d.; 26 ± 3 years) by releasing bilateral thigh cuffs after 6 min of supra-systolic resting ischaemia. Hypotension was induced before and after sympathetic blockade (β-1 receptors), and combined sympathetic-cholinergic blockade. That sequential bolus injections of sodium nitroprusside (50 μg), followed 60 s later by phenylephrine hydrochloride (50 μg), elicited <5 beats min change in heart rate was verified to confirm that full cardiac autonomic blockade was achieved. Thigh cuff release elicited a transient drop in mean arterial pressure and resultant tachycardia. This tachycardic response was diminished in full cardiac blockade (vs. control, P= 0.029; vs.β-1 adrenergic blockade, P= 0.031). Dynamic CA was also attenuated in the full blockade condition compared to both control (P= 0.028) and β-1 adrenergic blockade conditions (P= 0.015), and was related with the attenuated tachycardia response (P= 0.015). These data indicate an important role of the cardiac baroreflex in dynamic CA.
UR - http://www.scopus.com/inward/record.url?partnerID=yv4JPVwI&eid=2-s2.0-74549166037&md5=1eb523bbac7c9226d1c2e175dcf19044
U2 - 10.1113/jphysiol.2009.180844
DO - 10.1113/jphysiol.2009.180844
M3 - Article
AN - SCOPUS:74549166037
SN - 0022-3751
VL - 588
SP - 365
EP - 371
JO - The Journal of Physiology
JF - The Journal of Physiology
IS - 2
ER -