Intraoperative Transcranial Ultrasonic Monitoring for Cardiac and Vascular Surgery

Abstract

The brain is the only organ not routinely monitored by any direct method during the administration of anesthesia. Anesthesiologists rely primarily on indirect physiologic evidence provided by blood pressure, peripheral pulse oximetry, heart rate, and respiratory and anesthetic gas concentrations to determine that brain blood flow and oxygenation are adequate. The reasons for this practice are that: (1) after millions of anesthetics significant numbers of adverse neurologic outcomes have not occurred, (2) the interpretation of transcranial Doppler, electroencephalogram, and near-infrared cerebral oximetry requires experienced personnel, and (3) the evidence of cost-benefit to support monitoring is limited. Brain monitoring generally has been confined to procedures where the brain is exposed to unique insults and risks specific to the procedures and where reliance on indirect physiologic evidence of cerebral integrity has been proven to be unreliable. Transcranial Doppler monitoring is valuable in the assessment of established surgical techniques, refinement of recent surgical techniques, and development of new techniques and instrumentation. Brain monitoring with transcranial Doppler is of particular value when deviations from established surgical or anesthetic techniques may place the brain at risk for cerebral hyper- or hypoperfusion, gaseous or particulate embolization, or their combined effects. This paper discusses applications of transcranial Doppler in coronary artery bypass surgery, aortic arch procedures, pediatric cardiac surgery, carotid endarterectomy, and a few other special cases. The insight into cerebral physiology is unique to the continuous window on the brain that transcranial Doppler provides.

Transcranial Doppler Ultrasound: A Review of the Physical Principles and Major Applications in Critical Care

“…(Discussion of peri-procedural TCD applications, including the evaluation of extracranial carotid disease [11, 36, 42], intracranial stenosis [6, 43–45] and monitoring in carotid endarterectomy [14, 35, 46–51] and other neurovascular [52–55] and cardiac procedures [56–58] are beyond the scope of this paper and the reader is directed to the referenced articles. )…”

Neuromonitoring in der Kardioanästhesie

“…Manche Autoren schlagen eine Flussgeschwindigkeit von 25 [80] oder 30 cm/s [96] in der A. cerebri media als Grenzwert vor, andere einen Abfall der Flussgeschwindigkeit um mindestens 50% [80], 60% [97] oder 80% [98]. Als einziges Neuromonitoring-Verfahren ist die TCD in der Lage, eine zerebrale Embolie von Luft (z.…”

Einfluss der Kardioanästhesie auf das Patientenoutcome

“…Auch sind akute embolische Ereignisse gut mittels TCD nachweisbar. Die Methode ist nicht invasiv und perioperativ recht einfach anwendbar, wenn der Schallkopf in akkurater Position gehalten werden kann [55].…”