Innovations in Neuromonitoring in Vascular Surgery and Neurosurgery

Perioperative mortality in vascular surgery and neurosurgery has markedly been reduced by improvement in surgical and anaesthesiological techniques. Also perioperative complications have been reduced. It remains a major challenge to minimize second-ary complications following ischemia of the central nervous system (CNS) during operation to achieve a good postoperative outcome with a high quality of life.

Different techniques for neuromonitoring are used during vascular surgery and neurosurgery. Besides his major duty to control depth of anaesthesia and vital functions the anaesthesiologist often is in charge to apply and interpret CNS monitoring. When cortical or spinal ischemia is detected early, improvement of the collateral perfusion or a change of the surgical technique may avoid secondary damage of this structures.

During the session about clinical neuromonitoring of the “Hauptstadtkongress” (HAI) of anaesthesiology and intensive care in Berlin 2003 different aspects and controversies of neuromonitoring today were discussed. Rückert explained the surgical point of view with respect to surgery of the carotid artery and the thoracic aorta. Early detection of ischemia is very important for the surgeon in order to decide whether to change the surgical technique. Selective shunting in carotid endarterectomies is preferred by Rückert, because implanting a temporary shunt may increase the risk of intraoperative stroke. However, Rückert pointed out that acceptance of neuromonitoring differs among the centres.

Rundshagen discussed controversies in the anaesthesiological management during carotid endarterectomies. In some centres regional anaesthesia is preferred. During cervical epidural anaesthesia or cervical plexus block the patients remain co-operative and direct assessment of the neurological state is possible. In other hospitals general anaesthesia with intubation is preferred. For CNS monitoring frequently somatosensory evoked responses elicited by electrical stimulation of the contralateral median nerve are used. However, there is not enough evidence from randomized trials comparing carotid endarterectomy under local as opposed to general anaesthetic.

Neurosurgical procedures are performed in the awake patient when co-operation of the patient is needed to minimize risk of damage of neural structures during operation. Boemke explained the anaesthesiological management of neurosurgical patients scheduled for stereotactic procedures with brain mapping, as it is performed in the Charité Hospital in Berlin. It is a challenge for the anaesthesiologist to titrate an adequate level of analgosedation, allowing the patient to breathe spontaneously with intact reflexes, to lie immobilized for hours, but to be co-operative to perform cognitive tests. Psychological assistance during surgery is of major importance for the patient. Up till now none of the different neuromonitoring techniques have been validated during awake craniotomy.

The surgical and anaesthesiological management of the patient with a thoraco-abominal aortic aneurysma remains a challenge for the interdisciplinary team. Bischoff discussed recent studies, which showed that disturbances of regional spinal perfusion with ischemia is detected by monitoring somatosensory and motor evoked potentials. A re-implantation of segmental arteries can improve spinal perfusion. During aortic surgery the incidence of paraplegia due to ischemia has been reduced to 3 %.

In summary different techniques for neuromonitoring are available. They afford a close interdisciplinary co-operation. For a correct interpretation of the signal the distinct knowledge of the techniques and possible artifacts is essential. Then without doubt neuromonitoring increases safety for the patient despite an increase in technical and personal capacities.