Splanchnic organ blood flow during calcitonin gene-related peptide-inducedhypotension with or without propranolol in dogs

Propranolol has been used to attenuate reflex tachycardia during induced hy potension. The purpose of the current study was to determine whether propra nolol can modify splanchnic organ blood flow during calcitonin gene-related peptide (CGRP)-induced hypotension in dogs anesthetized with 1.3% isoflura ne in oxygen. After surgical preparation and hemodynamic stabilization, sal ine as a control, 0.5 mg/kg and 2.0 mg/kg propranolol (n = 10, each) were a dministered in a bolus injection 20 min before hypotension was induced. Mea n arterial pressure was reduced to 60 mm Hg during 60 min of CGRP infusion. Renal blood flow (RBF), hepatic blood flow (HBF), and pancreatic blood flo w (PBF) were measured using the hydrogen clearance method. Cardiac index di d not change in all three groups, and heart rate in the control group remai ned unchanged. In the propranolol groups, however, heart rate decreased (P < 0.01). Plasma norepinephrine (NE), but not epinephrine (E), increased (P < 0.05) after propranolol administration. The NE and E increased (P < 0.01) during induced hypotension in all three groups. NE was higher in the 0.5 m g/kg propranolol group than in the control group. RBF in the control group remained unchanged throughout observation. RBF, HBF, and PBF decreased (P < 0.01) after propranolol and remained decreased during and after induced hy potension. The degrees of decreased HBF and PBF in the control group were l ess than those in the 2.0 mg/kg propranolol group. In conclusion, pretreatm ent with propranolol decreases splanchnic organ blood flow further during C GRP-induced hypotension, due in part to increased plasma catecholamine conc entrations.