title: Cerebral response to haemodilution during cardiopulmonary bypass in dogs: the role of nitric oxide synthase.
abstract: During cardiopulmonary bypass, haemodilution is standard practice and is accompanied by increases in cerebral blood flow (CBF). We investigated if changes in cerebral vascular resistance (CVR) during cardiopulmonary bypass-haemodilution are dependent on nitric oxide synthase. The cerebral response to haemodilution in nine dogs treated with the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), was compared with a control group (n = 8). Both groups underwent serial isovolaemic haemodilution (target packed cell volumes 0.39, 0.26, 0.19 and 0.14) using 6% dextran 70. CBF, CVR and cerebral metabolic rate for oxygen (CMRO2) were measured. While initial CVR was different in the two groups, haemodilution-dependent reductions in CVR were equivalent and the curves describing the packed cell volume-CVR relationship were parallel in control and nitric oxide synthase inhibition groups. Our data indicate that nitric oxide synthase does not play a primary role in the cerebral response to haemodilution.
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: W
authors.initials: W
authors.lastname: Plöchl
authors.forename: B L
authors.initials: BL
authors.lastname: Liam
authors.forename: D J
authors.initials: DJ
authors.lastname: Cook
authors.forename: T A
authors.initials: TA
authors.lastname: Orszulak
mesh_terms: D000818:Animals; D002315:Cardiopulmonary Bypass; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006400:Hematocrit; D006438:Hemodilution; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000502:physiology*; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester