title: Changes in cerebral hemodynamics after a single dose of clonidine in severely head-injured patients.
abstract: alpha 2-Adrenergic agonists induce cerebral vasoconstriction, reduce intracranial pressure (ICP) in experimental animals and may be useful in the hemodynamic management of head-injured patients. We studied the effects of the alpha 2 agonist clonidine on the cerebral circulation in 12 head-injured patients (Glasgow Coma Scale score < 8). Middle cerebral artery flow velocity (MCAV), ICP, mean arterial pressure (MAP), and cerebral perfusion pressure (CPP), were continuously recorded before (T0), at the end (T1), and 30 min after (T2) a 10-min intravenous (i.v.) infusion of 2.5 micrograms/kg clonidine. The cerebral arteriovenous oxygen content difference (AVDO2) and Paco2 were sequentially obtained. ICP, Paco2, AVDO2, and MCAV did not change after clonidine administration. In contrast, MAP and CPP decreased (P < 0.05 and P < 0.05, respectively, at T1 and T2). Three subjects displayed a transient increase in ICP (> 10 mm Hg) at T1; this increase was concomitant with the decrease in MAP. Clonidine administered as an i.v. infusion may induce a critical but transient increase in ICP in some severely head-injured patients. This effect may result from cerebral autoregulatory vasodilation and increased cerebral blood volume as a response to the hypotensive effects of clonidine.
authors.affiliation: Surgical Intensive Care Unit, Hôpital Henri Mondor, Creteil, France.
authors.forename: A
authors.initials: A
authors.lastname: ter Minassian
authors.forename: L
authors.initials: L
authors.lastname: Beydon
authors.forename: P
authors.initials: P
authors.lastname: Decq
authors.forename: F
authors.initials: F
authors.lastname: Bonnet
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage* / Q000494:pharmacology; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001930:Brain Injuries / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D002245:Carbon Dioxide / Q000097:blood; D002536:Cerebral Arteries / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D003000:Clonidine / Q000008:administration & dosage* / Q000494:pharmacology; D006801:Humans; D007262:Infusions, Intravenous; D007427:Intracranial Pressure / Q000187:drug effects; D010100:Oxygen / Q000097:blood; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D000316:Adrenergic alpha-Agonists; D002245:Carbon Dioxide; D003000:Clonidine; D010100:Oxygen