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Biomedical subjects

M Dinkel

Publications and source records attributed to M Dinkel.

28 records · Page 2Linked to original sources
PubMed1994

[Neuromonitoring in carotid surgery: possibilities and limits of transcranial Doppler ultrasound].

In order to evaluate the suitability of transcranial Doppler sonography as an intraoperative monitor in carotid surgery, we compared measurements of mean blood flow velocity in the ipsilateral middle cerebral artery with the cortical response of somatosensory evoked potentials in a prospective study of 176 carotid operations. SEP recording was readily feasible during all procedures and by means of SEP loss all patients at risk for critical cross-clamp related cerebral ischemia were reliably identified. In contrast, TCD could not be used for assessment of cerebral hemodynamics in more than 40% of patients. What is more, in high risk patients with intraoperative loss of SEP, TCD could not be performed in 74% of cases. This high rate of failure limits the usefulness of TCD as an intraoperative monitor and detracts from the additional benefit of identifying cerebral embolism and hyperperfusion as potential causes of neurological deficits. In contrast to SEP recording, TCD cannot be recommended as a routine monitor in carotid surgery.

Aged↗
PubMed1992

Monitoring during carotid surgery: somatosensory evoked potentials vs. carotid stump pressure.

In the following prospective study of 125 carotid endarterectomies, we compared monitoring of somatosensory evoked potentials (SEPs) with carotid stump pressure (CSP) measurement in order to determine the efficacy of both methods in reliably predicting cerebral ischemia caused by cross-clamping of the carotid artery. A complete flattening of the cortical SEP was the sole criterion for selective shunting. Two patients suffered from transitory neurological deficits in the postoperative period. Both experienced complete disappearance of postcentral SEP components after carotid cross-clamping. In a further 10 cases, an intraoperative loss of SEP amplitudes occurred, but could be reversed by the insertion of a shunt or by induced hypertension. All of these patients showed a normal neurological examination postoperatively as did all of the patients with identifiable SEPs after cross-clamping. In all of the 12 patients with complete flattening of the cortical waveform, we found CSP levels less than 50 mm Hg. A further 61 patients had a CSP less than 50 mm Hg, but neither an intraoperative loss of SEP amplitudes nor postoperative neurological deficits were detected in any of these patients. We conclude that, in contrast to CSP, SEPs not only help to identify patients with insufficient collateral blood flow who benefit from specific cerebral protection, but also to avoid improper and hazardous application of these measures in patients with sufficient cerebral perfusion.

Aged↗
PubMed1991

Somatosensory-evoked potentials during carotid artery surgery: experience in 400 operations.

A prospective study was undertaken to determine the efficacy of monitoring somatosensory-evoked potentials (SEP) during carotid artery surgery in predicting a new ischemic neurologic deficit. Three hundred seventy-six patients underwent 400 reconstructions of the internal carotid artery. The mortality rate of the entire series was 0.8%. In 383 procedures, SEP amplitudes were always present during cross-clamping of the internal carotid artery. In spite of that, three neurologic deficits occurred, but all were associated with technical failures and not related to clamping ischemia. Complete loss of SEP amplitudes was noted in 17 procedures. Five of seven patients without an indwelling shunt showed a neurologic deficit after surgery, whereas shunt insertion in 10 resulted in three neurologic deficits. It is concluded that at present SEP recording is an accurate monitoring method in detecting clamping-related cerebral ischemia during carotid artery surgery.

Adult↗
PubMed1991

[Somatosensory evoked potentials in carotid surgery].

During carotid surgery a monitoring device that will identify patients with inadequate cerebral perfusion and impending cerebral damage after carotid clamping is desirable. Such patients may benefit from cerebral protective measures, which should be applied selectively as their use can also lead to complications. METHODS. In order to evaluate the reliability of somatosensory evoked responses as a means of detecting patients with insufficient collateral perfusion after carotid cross clamping, a prospective study involving 482 operations for reconstruction of supraaortic vessels was performed. Somatosensory evoked potentials (SEPs) were recorded from a cervical (C2-Fz) and a parietal (C3'/C4'-Fz) electrode above the ipsilateral hemisphere following stimulation of the contralateral median nerve. RESULTS. In 22 procedures (4.6%) complete flattening of the cortical SEP occurred after carotid cross clamping. In 7 of 9 cases in which no indwelling shunt was used despite electrical silence neurological deficits were found postoperatively. The SEP amplitude was restored in 12 of the remaining 13 patients with complete loss of the SEP after shunt insertion. Only 3 of these patients demonstrated neurological impairment. During 460 operations evoked potentials were always present. Nevertheless, 5 neurological sequelae were noticed despite unchanged SEP after carotid artery clamping. All deficits, however, were caused by embolization and were unrelated to reduced blood flow after carotid cross clamping. CONCLUSIONS. Our results confirm the reliability of SEP monitoring for the detection of significant cerebral ischemia after carotid clamping. In absence of the cortical SEP immediate shunt placement is necessary to avoid neurological deficits. On the other hand, the risks attendant on indiscriminate cerebral support (embolism after shunt placement, cardiac ischemia due to induced hypertension) can be avoided in the presence of cortical potentials. This allows protection of the heart and the brain by anesthetic management and enables the surgeon to perform endarterectomy with no hurry, to avoid technical failure. SEP data may also be helpful in decision making on reoperation to look for sources of embolization. In conclusion, advanced monitoring by somatosensory evoked responses may help to improve the outcome of carotid surgery.

Carotid Arteries↗