State of the Art Cerebral Monitoring: Surgical Carotid Endarterectomy
Sagar Sutaria, D.O.
UCONN Hlth School of Med-Dept of Anes,
Farmington, CT, USA
Thomas C. Mort, M.D.
UCONN Hlth School of Med-Dept of Anes,
Hartford Hospital Department of Anesthesiology,
Hartford, CT, USA
Ensuring adequate blood flow to the brain during a surgical carotid endarterectomy is an imperative component of patient safety during the procedure.
This case describes the gold standard approach, awake cerebral monitoring, achieved by regional anesthesia techniques.
Alternative cerebral blood flow monitoring modalities such as EEG monitoring, somatosensory evoked potentials, and transcranial Doppler to monitor cerebral activity are also routinely practiced during this procedure.
In an effort to compare the outcomes of the different modalities, this case description will highlight the various modalities available for this surgical procedure and compare them to awake cerebral monitoring combined with regional anesthesia block.
Monitoring for cerebral ischemia during the carotid endarterectomy procedure (CEA) is of paramount importance. Several different techniques are currently used for cerebral monitoring. EEG monitoring, somatosensory evoked potentials, transcranial doppler, and an awake CEA are some of the techniques currently used in practice today.
The original and gold standard technique is performing an awake CEA by adjunct regional anesthesia techniques [1,2]. This technique, however, has been supplanted by many who prefer the more technical modalities. Despite the superiority the awake CEA technique offers, what are the primary factors that has led to the shift away from the awake approach being incorporated by the surgical-anesthesiology team?
This case presentation will highlight the successful use of the awake technique and illustrates the efficacy of this technique in practice today.
A 71 y/o male with a history of CAD, Type II DM, HLD, PVD and severe carotid artery stenosis, presented to Hartford Hospital for a CEA. The patient denied any TIA or stroke symptoms but had carotid Doppler studies which indicated severe right carotid stenosis (>85%) combined with a 50% stenosis on the left side. The surgical team deemed the patient a good candidate for CEA based on the extensive carotid stenosis in accordance to their current guidelines.
The surgical team requested anesthesia evaluation to determine if the patient was an appropriate candidate using regional anesthesia with minimal to no sedation so to afford patient participation and thus, valuable neurological assessment and feedback intra-operatively. A deep and superficial cervical plexus block was the primary anesthesia plan. Following administration of 2 mg IV midazolam, the block was executed successfully by the regional pain team.
Once transported to the operating room, standard ASA monitors were placed. A propofol infusion (25mcg/kg/min) was used briefly during patient positioning to assist with comfort. Narcotic supplementation (25 mcg fentanyl) was also administered during this time frame. To optimize neurological assessment and feedback during the procedure, the patient was instructed to squeeze a small, hand held “squeeze toy” to afford audible feedback to the surgical team at baseline as well as during critical times during vascular cross-clamping with disruption of cerebral blood flow.
Moreover, the patient’s verbal responsiveness to questions during the procedure were employed as a valuable adjunct for neurological assessment. The mean arterial pressure (MAP) was maintained in the range of 80-95 mmHg, reflecting the patient’s pre-operative MAP range. Carotid clamping time was less than 40 minutes.
At the end of the case the patient was taken to the PACU and then to the floor. Post operatively patient did have a minor soft hematoma at incision site that did not compress the airway or affect swallowing. Hematoma would resolve on its own. Patients post-operative course was uncomplicated, and patient was discharged from hospital POD
This case highlights the use of the awake technique for cerebral monitoring for a CEA. The current literature states the awake carotid approach is the most reliable approach for cerebral monitoring during a CEA.
The benefit of the awake technique is simple: any significant cerebral ischemia that occurs during vascular manipulation and is associated with rapid neurological alteration or deterioration, may be recognized immediately by the surgical team thus allowing the surgeon to rectify the situation as quickly as possible; e.g., shunt insertion.
The other available monitoring modalities, such as SSEPs offer unique feedback and are a reliable technique for cerebral monitoring, however, they can have limitations. Specially, studies have shown the techniques such as Trans-Cranial Doppler (TCD), and SSEP have been associated with technical difficulties,(difficulty with interpretation). Moreover, the use of inhalation agents can interfere with SSEP monitoring.
Particularly, there can be a delay between the changes in amplitude of the SEP to when it is detected. The TCD has also been associated with technical difficulties such as intraoperative probe dislocation. Between the three modalities: SSEP, TCD and EEG, the literature suggests that SSEP hold the edge as the most useful adjunct for cerebral monitoring. Contrary to the consistent support the literature offers to the awake CEA method being the most sensitive and specific cerebral monitoring modality, more anesthesiologists are choosing GA with one or more of the modalities listed above, instead of the awake approach using local anesthetic techniques. The awake approach does have its challenges.
First, patient cooperatively is required for the awake approach, therefore patients may not be comfortable or tolerate this technique. Also, the surgeon preference is another factor, as many surgeons prefer GA as it may offer better surgical exposure. Also, for patients with respiratory issues, some anesthesiologists may prefer a controlled airway.
However, despite its limitations, the awake approach is the most sensitive monitor for cerebral monitoring. Moreover, the literature states that CEA performed under local anesthesia has been associated with lower rates of perioperative stroke. [4,5].
Thus, when applied to the appropriate patient and surgical practitioner, one should appreciate that the consensus favors the awake approach as the superior approach.
Therefore, should the anesthesia team advocate for the awake approach for the CEA procedure?Figure 2
Technique for Superficial cervical Plexus block Block
Source: NYSORA Figure 1-
Anatomical Landmarks for Superficial Cervical Plexus Block
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