Mechanisms controlling the oxygen consumption in experimentally induced hypochloremic alkalosis in calves

Abstract

-The study was carried out on healthy Friesian calves (n = 10) aged between 10 and 30 days. Hypochloremia and alkalosis were induced by intravenous administration of furosemide and isotonic sodium bicarbonate. The venous and arterial blood samples were collected repeatedly. 2,3-diphosphoglycerate (2,3-DPG), hemoglobin and plasmatic chloride concentrations were determined. The red blood cell chloride concentration was also calculated. pH, PCO 2 and PO 2 were measured in arterial and mixed venous blood. The oxygen equilibrium curve (OEC) was measured in standard conditions. The correspondence of the OEC to the arterial and mixed venous compartments was calculated, taking blood temperature, pH and PCO 2 values into account. The oxygen exchange fraction (OEF%), corresponding to the degree of blood desaturation between the arterial and mixed venous compartments and the amount of oxygen released at the tissue level by 100 mL of blood (OEF Vol%) were calculated from the arterial and mixed venous OEC, combined with PO 2 and hemoglobin concentration. Oxygen delivery (DO 2 ) was calculated using the arterial oxygen content, the cardiac output measured by thermodilution, and the body weight of the animal. The oxygen consumption (VO 2 ) was derived from the cardiac output, OEF Vol% and body weight values. Despite the plasma hypochloremia, the erythrocyte chloride concentration was not influenced by furosemide and sodium bicarbonate infusion. Due to the alkalosis-induced increase in the 2,3-DPG, the standard OEC was shifted to the right, allowing oxygen to dissociate from hemoglobin more rapidly. These changes opposed the increased affinity of hemoglobin for oxygen induced by alkalosis. Moreover, respiratory 697 Vet. Res. 33 (2002) acidosis, hemoconcentration, and the slight decrease in the partial oxygen pressure in mixed venous blood (Pvo 2 ) tended to improve the OEF Vol% and maintain the oxygen consumption in a physiological range while the cardiac output, and the oxygen delivery were significantly decreased. It may be concluded that, despite reduced oxygen delivery, oxygen consumption is maintained during experimentally induced hypochloremic alkalosis in healthy 10-30 day old calves.blood oxygen binding / oxygen equilibrium curve / oxygen consumption / hypochloremic alkalosis / calf Résumé -Mécanismes contrôlant la consommation en oxygène lors d'alcalose hypochlorémique induite expérimentalement chez le veau. Ces études ont été menées chez des veaux sains de type laitier, de race Frisonne (n = 10), âgés de 10 à 30 jours. L'hypochlorémie et l'alcalose ont été induites par l'administration intraveineuse de furosémide et de bicarbonate de sodium isotonique. Des échantil-lons sanguins ont été prélevés, de manière répétée, au niveau artériel et veineux. Les concentrations en 2,3-diphosphoglycérate (2,3-DPG), en hémoglobine et en chlore plasmatique ont été déterminées. Les concentrations intra-érythrocytaires en chlore ont également été calculées. Les valeurs de pH, PCO 2 et PO 2 ont été déterminées dans le sang ar...

Stability of oxyhemoglobin affinity in patients with obstructive sleep apnea-hypopnea syndrome without daytime hypoxemia

“…The entire ODC on whole blood was traced under standard conditions (pH 7.40; PCO 2, 40 mmHg; temperature, 37°C) and was corrected to the in vivo ODC by using actual values of pH, PCO2, and temperature. The advantage of this method is that it describes the ODC at all levels of oxygen saturation and thereby gives the resulting function of oxygen loading and unloading (3). We report in this study the values of partial pressure of oxygen in blood associated to a Hb oxygen saturation of 50% and 90% (P50 and P90).…”