Alterations on Arterial Blood Pressure Regulation (Baroreceptor Reflex Study) of Experimental and Human Portal Hypertension

pp 159-165

Abstract

Background

The experimental and human portal hypertension shows hemodynamic alterations, they are always iniciated by an increased vascular resistance to portal blood flow. The hyperdynamic splachnic circulation is accompanied by increased cardiac output together with reduced arterial pressure and splachnic and peripheral vascular resistance. The purpose of this work was to study baroreflex system in portal hypertensive patients and in experimental portal hypertensive rat model.

Material and method

A) Portal hypertensive and sham operated rats were studied. Heart rate and arterial blood pressure were recorded and baroreceptor reflex was evaluated by increasing arterial blood pressure with single doses of phenylephrine. Sigmoid curves relating systolic blood pressure and heart period were obtained. The slope of the regression line was considered the gain of the reflex. B) Portal hypertensive patients and control subjects were studied. Baroreflex system was evaluated by using different doses of phenylephrine. Gain of the reflex was calculated with similar experimental method as in rat model.

Results

Gain (msec/mmHg): A) Experimental model: sham operated = 1.29 ±0,10; portal hypertension = 0.62 ± 0.04 (p < 0.001). B) Controls = 8.2 ± 0.4; portal hypertensive patients = 4.1 ±0,6 (p < 0.001).

Conclusions

Both groups, experimental model and patients, showed a significant decreased in baroreceptor reflex response. The ressetting of the reflex observed in our study could occur, at least in part, through the interaction between arterial and cardiopulmonary baroreflex pathway at the central nervous system level.