Continuous recording of middle cerebral artery blood velocity in clinical neurosurgery

Abstract

Intracranial pressure, arterial blood pressure, and middle cerebral artery blood velocity were monitored for periods from 1 to 10 days in 30 neurosurgical intensive care patients. The recordings revealed rapid changes in the cerebral perfusion and gave insight into individual cerebral haemodynamic states. Twenty patients consistently showed CO2 reactivity within normal limits, between 2.5 and 5% per mm Hg (19-38% per kPa). Severely impaired CO2 reactivity, considerably below 1% per mm Hg (7.5% per kPa) was observed in four patients. Three of these patients died, while the fourth patient survived in a persistent vegetative state. Seven patients demonstrated pressure-passive blood velocity changes throughout the observed CPP range. The four patients with severely impaired CO2 reactivity all belonged to this group. The recordings from three of the remaining 23 patients showed signs of MCA blood velocity autoregulation with a lower regulatory limit of about 40-45 mm Hg. This observation is in keeping with findings from electromagnetic flowmetry on brain arteries in the neurosurgical operating field, and supports blood velocity measurements as a relevant index of brain perfusion in clinical neurosurgery and neuro-intensive care settings.

Noninvasive Intracranial Cerebral Flow Velocity Evaluation in the Emergency Department by Emergency Physicians

“…It can be used to monitor cerebral vasospasm after subarachnoid hemorrhage, embolic phenomena during surgery, and the effects of pharmacologic agents on cerebral flow velocities. 8 Mean flow velocities have been found to be proportional to direct invasive flow measurements. 8 Head injury patients have been previously evaluated with TCD.…”

“…8 Mean flow velocities have been found to be proportional to direct invasive flow measurements. 8 Head injury patients have been previously evaluated with TCD. 9 However, these evaluations were performed in intensive care units some time after the initial injury.…”

Evaluation of hemodynamic responses in head injury patients with transcranial doppler monitoring

“…Continuous transcranial Doppler monitoring can also now be used to non-invasively monitor relative changes in CBF, by measuring relative blood flow velocity changes through the inflow vessels, under certain specific circumstances [4,5,8,29,32,33,55].…”

Spontaneous Low-Frequency Oscillations in Cerebral Vessels: Applications in Carotid Artery Disease and Ischemic Stroke

“…Various neurologic disorders exhibit changes in CA. 8–11 CA can be studied by static 12 and dynamic 5 interventional methods, but the use of these methods requires a certain level of compliance and can be stressful or even harmful to the patient. Over the last 10 years, an increasing number of studies have assessed CA by recording spontaneous oscillations in mean arterial blood pressure (MAP) and cerebral blood flow (CBF).…”