Hemodynamic, Fluid, and Electrolyte Changes during Sodium Depletion in Conscious Dogs

Abstract

Hemodynamic, fluid and electrolyte changes were studied during Na depletion and repletion in 6 conscious dogs. Blood pressure (BP), plasma renin activity (PRA), heart rate (HR), cardiac output (CO), stroke volume (SV) and plasma volume (PV) were determined on 3 separate days in Na replete conscious animals, similarly during Na depletion and again after Na repletion. During Na depletion, HR increased from 73-91 beats/min (P < 0.01). CO fell from 2.32 to 1.87 l/min (P < 0.01). SV decreased from 32.6 to 21.7 ml (P < 0.01). Peripheral resitance (PR) increased from 41.5 to 49.2 mm Hg (l/min)-1 (P < 0.01). BP was unchanged. PRA increased from 0.83 to 7.51 ng angiotensin I/ml per h (P < 0.01). During the 8 days of Na depletion, H2O intake was elevated on 6 days, urine volume was elevated on 5 days and water balance was positive on 3 days. With Na and volume repletion, all functions returned to control levels. Na depletion produced significant decreases in CO and PV with BP maintained by increased PR and HR. Whole body autoregulation failed to occur during the Na and volume repletion and expansion of the recovery period.