Acute respiratory acidosis: large-dose furosemide and cerebrospinal fluid ions.

NaCl cotransport carrier is known to be involved in transepithelial fluid absorption and secretion in various tissues. Recent studies indicate that Na-K-2Cl cotransport carrier also exists in the choroid plexus cells and that inhibition of the carrier decreases cerebrospinal fluid (CSF) production. In this study, we used large-dose intravenous furosemide, an inhibitor of Na-K-2Cl carrier, to determine the effects on cisternal CSF ionic composition in acute respiratory acidosis. In pentobarbital-anesthetized mechanically ventilated dogs, renal pedicles were ligated to prevent furosemide-induced diuresis. The experimental group (group II, n = 7) received 400 mg/kg of furosemide intravenously, and group I (control group, n = 7) received the vehicle. In group II, serial serum and CSF furosemide concentrations were approximately 10(-3) and 10(-5) mol/l, respectively. During 5 h of acute respiratory acidosis in both groups, the mean arterial PCO2 increased approximately 25 Torr, with comparable changes in CSF PCO2. In both groups, CSF [HCO3-] and [H+] rose approximately 3 meq/l and 20 neq/l, respectively. Changes in CSF [Na+], [K+], [Cl-], and [Na(+)-Cl-] were also similar and were not significantly different from each other when the two groups were compared. These data show that furosemide at the dose that inhibits NaCl cotransport carrier does not significantly alter ionic composition of cisternal CSF.