Am. J. Respir. Crit. Care Med., Vol 150, No. 1, Jul 1994, 78-82.
Quantitative cerebrospinal fluid acid-base balance in acute respiratory alkalosis
S Javaheri, W Corbett, K Wagner and JM Adams
Department of Veterans Affairs Medical Center, University of Cincinnati College of Medicine, Ohio 45220.
Data on canine cisternal cerebrospinal fluid (CSF) ions in acute
respiratory alkalosis are limited and fragmentary. We hypothesized that
with the fall in arterial PCO2 (PaCO2) and in the face of normal
osmoregulation, CSF [Na+] remains relatively constant and CSF [Na+-Cl-]
narrows to account in part for the fall in CSF [HCO3-]. We therefore
measured blood and CSF acid-base variables and ions of two groups of
pentobarbital-anesthetized, mechanically ventilated dogs (n = 10 in each
group). In the control group, PaCO2 was kept constant and changes in serum
and CSF ions were minimal. In Group II (acute respiratory alkalosis), both
PaCO2 and cisternal CSF PCO2 decreased by 10 mm Hg. Five hours after
induction of respiratory alkalosis, mean CSF [HCO3-] decreased
significantly by 4.4 +/- 1.2 mEq/L (mean +/- SD). The fall in CSF [HCO3-]
was similar to changes in CSF strong ion difference (SID =
Na(+)+K(+)+Ca(2+)+Mg(2+)-CL(-)-lactate), which decreased 4.4 +/- 1.9 mEq/L.
Concentrations of the four major CSF cations did not change significantly.
Cisternal CSF lactate rose significantly by 1.2 +/- 0.9 mEq/L, accounting
for 25% of the change in CSF [HCO3-]. The remaining (75%) change in CSF
[HCO3-] was accounted for by changes in CSF [Cl-].
