Aortic input impedance during hypovolemic shock and after hyperosmotic solution infusion.
Aortic input impedance (Zin) was determined in 7 chloralose-urethane-anesthetized dogs. Flow and pressure were recorded in the ascending aorta during random cardiac pacing. These signals were processed on a spectrum analyzer utilizing the Fast Fourier Transform. Measurements were made 1) under control conditions; 2) every 5 min throughout 1 hr of hypovolemic shock; 3) every 5 min for 30 min after ending infusion of hyperosmotic solution (7.5% NaCl, 4.5 ml/kg body weight). We conclude that the determination of characteristic impedance (Zc) (average value of Zin from 4 to 10 Hz) can be useful for determining the initial phase of vascular decompensation in hypovolemic shock. After hyperosmotic solution infusion we observed a reduction in peripheral resistance, Zin, Zc, frequency of minimal Zin and frequency of phase crossover. These data strongly suggest a decrease in arterial vascular tonus.
Garcia
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AC
Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Brasil.
Fonseca-Costa
A
A
Rocha
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ES
Peixoto
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PC
D000818:Animals; D001011:Aorta / Q000502:physiology* / Q000503:physiopathology; D001794:Blood Pressure; D004285:Dogs; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D012769:Shock / Q000503:physiopathology; D014655:Vascular Resistance / Q000187:drug effects
D012462:Saline Solution, Hypertonic