Alteration in the lower limit of autoregulation with elevations in cephalic venous pressure

AbstractObjectives:Recent studies suggest that elevated intracranial pressure (ICP), created by hydrocephalus, can alter the lower limit of cerebrovascular autoregulation (LLA). Our objective in the present study was to determine if ICP elevation from cerebral venous outflow obstruction would result in comparable alterations in the LLA.Methods:Anesthetized juvenile pigs were assigned to one of two groups: naive ICP (n  =  15) or high ICP (>20 mmHg; n  =  20). To elevate ICP through venous obstruction, a modified 5F esophageal balloon catheter was inserted via the right external jugular vein into the superior vena cava (SVC) and inflated to maintain an ICP of >20 mmHg. To calculate the LLA, gradual hypotension was induced by continuous hemorrhage from a catheter in the femoral vein. The LLA was determined by monitoring cortical laser Doppler flux (LDF).Results:The naive and high ICP groups had LLAs of 45 mmHg (95% CI: 41–49 mmHg) and 71 mmHg (95% CI: 66–77 mmHg) respectively by LDF. The LLA was significant...