Avaliação do fluxo arterial mesentérico em humanos durante o exercício

Abstract

Mesenteric artery blood flow was measured by Doppler ultrasound in eight healthy subjects (age 21-26 years, mean=25.8) submitted to incremental exercise. As cardiovascular responses change above the point at which blood lactate starts to accumulate, a protocol was designed to determine the velocity profile and mesenteric artery flow redistribution along incremental exercise. On the first part of the protocol all individuals were submitted to determinations of lactate thresholds by the enzimatic method modified by Ribeiro et al (1986). On the second test mesenteric artery blood flow and sistolic, reverse and diastolic velocities were measured at rest and immediately after 30 Watts, first lactate threshold, second lactate threshold and at peak exercise. In this way exercise intensities were adjusted for each individual independently of training and physical conditions. Total mesenteric artery blood flow was calculated using planimetric measurement of the velocities waves and area determinations. The Friedman test was used to analise de data. There was no significant change of sistolic velocities during incremental exercise. In the other hand there was a marked decrease of diastolic velocities; a linear decrease of initial diastolic velocities and an abrupt decrease of end-diastolic velocities after the first lactate threshold. At peak exercise a redution of 77% in end-diastolic velocities was observed. A linear reduction of mesenteric artery blood flow was observed and there was no correlation with lactate thresholds; at peak exercise a decrease of 34% was detected. Resting mesenteric blood flow was 1.034± 112 (SE), at 30 Watts 1.002± 124 (SE), at the first lactate threshold 869± 122 (SE), at the second lactate threshold 866± 127 (SE) and at peak exercise 689± 104 (SE).

O aumento da atividade simpática durante o exercício dinâmico progressivo associa-se à resposta da concentração de lactato sangüíneo. Com o objetivo de testar a hipótese de que a diminuição do fluxo da artéria mesentérica superior também tenha relação com a lactiacidemia, oito indivíduos saudáveis (idade de 21-26 anos) foram submetidos a exercício com incremento progressivo de cargas ajustadas para os limiares de lactato, sendo o fluxo da artéria mesentérica superior medido pelo EcoDoppler. O fluxo na artéria mesentérica superior, calculado por medidas planimétricas das velocidades e medidas da área de secção, foi avaliado em repouso, após carga de 30 Watts, no primeiro e segundo limiares de lactato e esforço máximo, O fluxo (média ± EP) no repouso foi de 1.034 ± 112 ml/min, de 1.002 ± 124 na carga de 30 Watts, de 869 ± 122 ml/min no primeiro limiar de lactato, de 866 ± 127 ml/min no segundo limiar de lactato e de 689 ± 104 ml/min logo após o esforço máximo, Ocorreu uma redução linear, sendo a redução média na carga máxima de 34% do fluxo de repouso, não havendo correlação com os limiares de lactato. Portanto, a redução do fluxo da artéria mesentérica superior apresenta uma resposta linear ao exercício progressivo.