Infusion of sodium bicarbonate in experimentally induced metabolic acidosis does not provoke cerebrospinal fluid (CSF) acidosis in calves

Abstract

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 (NaHCO(3)) 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.

Figure 1

Calves (n = 5) were infused intravenously with isotonic hydrochloric acid (HCl) intermittently over a 24-h period to maintain venous blood pH at approximately 7.1. Acidemia was then corrected with isotonic sodium bicarbonate (NaHCO₃) given intravenously, either rapidly (4 h) or slowly (24 h). BL, T0, T1, T2, T3, and T4 — abbreviations indicating time; BL — base line; T2, T3, and T4 — approximately 23 h, 24 h, and 25 h from T0.

Figure 2

Changes in blood and cerebrospinal fluid (CSF) acid-base parameters during the induction phase. Values are mean and 1S_x for all calves (n = 5) over 2 separate induction periods (total number of observations at each time point = 10). See Figure 1 for time markers.

Figure 3

Changes in blood and cerebrospinal fluid (CSF) acid-base parameters during the infusion of sodium bicarbonate. Values are means and 1 S_x. Time is measured from the beginning of sodium bicarbonate infusion (T4). □ — slow correction (24 h); ▴ — rapid correction (4 h).