Pulmonary venoconstriction caused by elevated cerebrospinal fluid pressure in the dog

Area of Science:

• Cardiovascular Physiology
• Pulmonary Circulation
• Neuroendocrinology

Background:

• Elevated cerebrospinal fluid pressure (PCSF) has been previously linked to pulmonary vasoconstriction.
• Adrenal catecholamines are implicated as mediators in this response.
• The precise location of pulmonary vasoconstriction due to increased PCSF remains to be fully elucidated.

Purpose of the Study:

• To localize the site of pulmonary vasoconstriction induced by elevated cerebrospinal fluid pressure.
• To differentiate between arterial and venous contributions to pulmonary vascular resistance changes.
• To confirm the role of adrenal catecholamines in this response.

Main Methods:

• Utilized the outflow occlusion technique in denervated canine lung lobes perfused at constant flow.
• Divided the pulmonary arteriovenous pressure gradient into upstream and downstream pressure drops.
• Measured pressure changes in response to artificially raised cerebrospinal fluid pressure and catecholamine infusions.

Main Results:

• Increasing cerebrospinal fluid pressure (PCSF) significantly elevated the pulmonary arteriovenous pressure gradient (Pa-v).
• The majority of this pressure increase (83%) was attributed to the downstream pressure drop, indicating venoconstriction.
• Infusion of norepinephrine and epinephrine mimicked the effects of elevated PCSF on pressure gradients.

Conclusions:

• Elevated cerebrospinal fluid pressure primarily induces pulmonary venoconstriction.
• Adrenal catecholamines mediate the observed pulmonary vasoconstriction in response to increased PCSF.
• Findings localize the vascular effects to the venous side of the pulmonary circulation.