Alterações do pH, da P O2 e da P CO2 arteriais e da concentração de lactato sangüíneo de cavalos da raça Arabe durante exercício em esteira de alta velocidade / Changes in arterial pH, P O2, P CO2 and blood lactate concentration in Arabian horses during exercise on a high-speed treadmill

Avaliaram-se as alterações do pH, da P O2 e da P CO2 do sangue arterial e da concentração de lactato sangüíneo de 11 cavalos adultos da raça Arabe, submetidos a exercício progressivo em esteira de alta velocidade. Antes do exercício, no intervalo dos 15 segundos finais de cada mudança de velocidade e aos 1, 3 e 5 minutos após o término do exercício foram coletadas amostras de sangue arterial e venoso para a mensuração dos gases sangüíneos e da concentração de lactato. O exercício resultou em diminuição do pH, da pressão parcial de O2 (P O2) e da pressão parcial de CO2 (P CO2). A concentração de lactato sangüíneo elevou-se exponencialmente a partir da velocidade de 8,0m/s até os momentos após término do exercício.

Changes in arterial blood pH, P O2 and P CO2, and blood lactate concentration in Arabian horses during exercise on a high-speed treadmill were investigated. Eleven horses were submitted to a conditioning period as well as to the incremental exercise test. The arterial and venous blood samples were obtained to evaluate the blood gas values and lactate concentration, prior to the beginning of the exercise, on the last 15 final seconds between every change of speed and at the 1, 3 and 5 minutes after the exercise. A decrease in pH, partial pressure of oxygen (P O2), and partial pressure of carbon dioxide (P CO2) and the blood lactate levels exponentially increase beyond the speed of 8m/s, during the incremental exercise test.

Repercussöes da hipercapnia sobre a hemodinâmica renal do cäo / Effect of hypercapnia on renal haemodynamics

Hypercapnia is not deliberately used nowadays even in the anesthetic management of carotid endarterectomy. Nevertheless, high PaCO2 level may occur during anesthetic procedures. Such altered carbon dioxide concentration trigger important changes in cardiovascular and renal function. This paper was designed to study some effects of hypercapnia upon the renal function in dogs. Twelve dogs fasted overnight were anesthetized with intravenous sodium pentobarbital (30 mg.kg elevado a menos um). The animals were intubated with a cuffed endotracheal tube, and ventilated with a takoaka respirator, using room air at the respiratory rate of 12 - 14 min elevado a menos um. Pancuronium bromide (0,08 mg.kg elevado a menos um) was injected to facilitate the ventilation. Cannulation of artery and vein was performed for blood sampling and fluid administration. In six dogs it was added CO2 to the room air at a concentration betwen 10 and 15 per cents. The following parameters were analized: mean arterial pressure (MAP), renal plasmatic flow (RPF), renal blood flow (RBF), glomerular filtration rate (GFR), urine output, carbon dioxide partial pressure (PaCO2), and oxygen partial pressure (PaO2). In the control group there was not any significant change in the analized parameters. In the group of dogs with high PaCO2 a MAP progressive decrease was observed from the begining of the experiment, that coned be explained by the direct action of CO2 on the peripheral vascular bed. The RBF values increased initially and decreased thereafter. This last result can be explained by the release of catecholamines due to hypercapnia, or by other factors such as interaction with the renin-angiotensin system, or acid-base imbalance. The decreased urinary output variedconversely to the PaCO2 remained unchanged throughout the experiment. This study shows that renal hemodynamic changes do not occur until PaCO2 level achieves 6,66 kPa (50 mm Hg). At the PaCO2 level of 9,33 kPa (70 mm Hg) slight elevation of the RPF and of the RBF is observed possibly due to the direct action of CO2 on the smooth muscles of the vessels. When 9,33 kPa is achieved, significant changes do occur in renal hemodynamics