[The role of metabolic acidosis in alphathesin-induced tachypnea in dogs].

In the dog anaesthetized with Althesin, tachypnea has been observed under light anaesthesia. There was also a metabolic acidosis which might be responsible for the increase of the respiratory rate. The ventilatory effects of the correction of the metabolic acidosis were studied in five dogs anaesthesized with Althesin administered at a constant rate of infusion (6.06 +/- 2.67 microliters X kg-1 X min-1). The ventilatory pattern (duration of inspiration, TI; duration of expiration, TE; duration of the respiratory cycle, Ttot; respiratory rate, f; ratio TI/Ttot, tidal volume (VT), minute ventilation (VE), mean inspiratory flow (VT/TI) and blood gases, pHa, PaCO2, PaO2, were measured before and after administration of 42 p milli sodium bicarbonate (495 mmol X l-1). Arterial pH increased from 7.27 +/- 0.10 to 7.44 +/- 0.20 (p less than 0.05). There was no statistically significant change of other values, particularly for respiratory rate which varied from 41 +/- 10.5 to 43.3 +/- 17.2 per minute. Metabolic acidosis does not explain the tachypnea. Mechanisms of tachypnea, particularly the role of histamine, are discussed.