ERPs obtained with the auditory oddball paradigm in coma and altered states of consciousness: clinical relationships, prognostic value, and origin of components.

Objective: To study the event related potentials (ERPs) in coma and altered states of consciousness, their relationship with the clinical status and coma outcome.

Methods: ERPs were recorded with a passive auditory oddball paradigm in 103 patients. Their probability of occurrence and the peak latencies and amplitudes were studied as a function of the Glasgow Coma Score (GCS).

Sensitivity, specificity, and surgical impact of somatosensory evoked potentials in descending aorta surgery.

Background: We evaluate the efficiency of multilevel somatosensory evoked potential (SEP) monitoring for intraoperative re-establishment of blood flow to the spinal cord in 63 patients undergoing descending aorta repair.

Methods: The presence of critical vessels in a cross-clamped aortic segment was ascertained by a 15 minute SEP observation period while the segment between the clamps was vented to drain out the collateral flow.

Results: SEPs influenced the surgical strategy in 17 cases (27%): use of the Biomedicus in 1 traumatic rupture; critical vessel reimplantation or distal clamp replacement in 13 cases of segmental spinal ischemia; and hastening the procedure or proximal clamp replacement in 3 cases of left carotid ischemia.

Somatosensory evoked potential monitoring in carotid surgery. I. Relationships between qualitative SEP alterations and intraoperative events.

This paper presents the results of intraoperative median nerve SEP monitoring in 205 successive patients undergoing isolated carotid endarterectomy (CE) (N = 172) or CE followed by coronary bypass (CBP) and/or vascular replacement (VR) (N = 33). The left and right median nerves were alternately stimulated and recordings performed on 4 channels: cervical, ipsi- and contralateral parietal, and frontal. SEPs were qualitatively rated in terms of mild, moderate, or severe ipsilateral, contralateral, or bilateral abnormalities.

Somatosensory evoked potential monitoring in carotid surgery. II. Comparison between qualitative and quantitative scoring systems.

This paper compares the respective yields of our SEP scoring system ('qualitative' criteria), based on the subdivision of SEP abnormalities into mild, moderate, and severe abnormalities, and a quantitative one ('classical' criteria), based on a more than 1 ms CCT increase or 50% decrease of N20 amplitude, for the detection of brain ischemia justifying shunt placement during carotid endarterectomy (CE). For that purpose, we examine the sensitivities of several neurophysiological parameters (the ipsilateral and contralateral CCT, the amplitudes of the ipsilateral and contralateral frontal and parietal SEPs) to carotid cross-clamping or to a drop of blood pressure. Our data first confirm that shunted patients developed a CCT increase and a decrease of N20 amplitude on the ipsilateral hemisphere.

The usefulness of the spinal and subcortical components of the posterior tibial nerve SEPs for spinal cord monitoring during aortic coarctation repair.

This study examines how the recording of the lumbar and subcortical components of the posterior tibial nerve (PTN) SEPs may usefully replace that of cortical components in situations in which these components cannot be reliably obtained (infants, high concentrations of halogenated gasses). Lumbar, brain-stem, and cortical PTN SEPs were intraoperatively monitored in 7 patients undergoing repair of aortic coarctation under variable isoflurane concentration (up to 1.2%).