Effect of furosemide on cerebrospinal fluid composition

Area of Science:

• Neuroscience
• Physiology
• Biochemistry

Background:

• Cerebrospinal fluid (CSF) electrolyte balance is crucial for central respiratory control.
• Chloride ([Cl-]) and bicarbonate ([HCO3-]) concentrations in CSF are key to maintaining this balance.

Purpose of the Study:

• To investigate how furosemide, a sodium-coupled chloride transport inhibitor, affects CSF electrolyte homeostasis.
• To examine these effects under both normocapnic and hypercapnic conditions in anesthetized dogs.

Main Methods:

• Administered furosemide intravenously (IV) or directly into the lateral cerebral ventricles (CV).
• Monitored CSF and arterial partial pressure of carbon dioxide (PCO2), pH, and electrolyte concentrations ([K+], [Cl-], [HCO3-], [NA+]).
• Utilized normocapnia and induced hypercapnia (5% CO2 breathing).

Main Results:

• IV furosemide during normocapnia decreased CSF [NA+] but did not alter other measured CSF parameters.
• IV furosemide during hypercapnia yielded results similar to hypercapnia alone.
• Cerebral ventricular (CV) furosemide during hypercapnia significantly reduced CSF [Cl-] without changing CSF [HCO3-].

Conclusions:

• Direct administration of furosemide into the CSF during hypercapnia alters CSF chloride levels.
• Sodium-coupled chloride transport appears to play a role in regulating CSF acid-base homeostasis during hypercapnia.