In a crossover study, 5 calves were made acidotic by intermittent intravenous infusion of isotonic hydrochloric acid (HCl) over approximately 24 h. This was followed by rapid (4 h) or slow (24 h) correction of blood pH with isotonic sodium bicarbonate (NaHCO3) to determine if rapid correction of acidemia produced paradoxical cerebrospinal fluid (CSF) acidosis. Infusion of HCl produced a marked metabolic acidosis with respiratory compensation. Venous blood pH (mean +/- S-x) was 7.362 +/- 0.021 and 7.116 +/- 0.032, partial pressure of carbon dioxide (Pco(2), torr) 48.8 +/- 1.3 and 34.8 +/- 1.4, and bicarbonate (mmol/L), 27.2 +/- 1.27 and 11 +/- 0.96; CSF pH was 7.344 +/- 0.031 and 7.240 +/- 0.039, Pco(2) 42.8 +/- 2.9 and 34.5 +/- 1.4, and bicarbonate 23.5 +/- 0.91 and 14.2 +/- 1.09 for the period before the infusion of hydrochloric acid and immediately before the start of sodium bicarbonate correction, respectively. In calves treated with rapid infusion of sodium bicarbonate, correction of venous acidemia was significantly more rapid and increases in Pco(2) and bicarbonate in CSF were also more rapid. However, there was no significant difference in CSF pH. After 4 h of correction, CSF pH was 7.238 +/- 0.040 and 7.256 +/- 0.050, Pco(2) 44.4 +/- 2.2 and 34.2 +/- 2.1, and bicarbonate 17.8 +/- 1.02 and 14.6 +/- 1.4 for rapid and slow correction, respectively. Under the conditions of this experiment, rapid correction of acidemia did not provoke paradoxical CSF acidosis.
