At a glance
ClinicalIndex Comparison RecordStandardized by ClinicalIndex from the ClinicalTrials.gov record · verify against the source.
Effect of Sodium Nitroprusside on Cerebral Blood Flow
In Brief
A clinical study evaluating Hyperventilation, 6% CO2 breathing, and 1 other intervention for Healthy Male Subjects. Completed, enrolled 20 participants across 1 site.
Detailed Summary
The brain has a high energy demand and requires continuous blood flow. The blood flow to the brain appears to be unaffected by small changes in blood pressure, but brain blood flow may be reduced by a large reduction in blood pressure. Large reductions in blood pressure are common during anesthesia or bleeding. It is unclear, however, how a given reduction in blood pressure affects blood flow to the brain. In this study, medicine called sodium nitroprusside is used to dilate blood vessels and reduce blood pressure in twenty healthy young men. The study will evaluate whether blood flow to the brain is affected when sodium nitroprusside is used to induce a moderate and a large reduction in blood pressure. Blood flow to the brain is evaluated using ultrasound on the neck. During breathing, oxygen is inhaled and carbon dioxide is exhaled. Carbon dioxide increases brain blood flow whereby changes in respiration can affect the blood flow to the brain. Sodium nitroprusside causes mild hyperventilation, whereby more carbon dioxide is exhaled, which will contribute to a reduction in brain blood flow. Thus, the study will also evaluate how brain blood flow is affected by hyperventilation and by breathing a mix of air and carbon dioxide.
Study Details
Timeline
Interventions
The subject is instructed to hyperventilate for 6 min to provoke a 0.7-1.2 kPa reduction in PaCO2, and the evaluation is repeated if the reduction in PaCO2 is not within this interval. The order of hyperventilation and 6% CO2 breathing is randomized.
The subject breathes a mixture of 6% CO2 (with 21% O2 and 73% N2) from a bag and a face mask for 6 minutes. The order of hyperventilation and 6% CO2 breathing is randomized.
Using incremental intravenous infusion of sodium nitroprusside MAP is reduced by 20% (15%-25%) and then by 40% (35%-45%, MAP minimally at 50 mmHg).