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At least 91 records · Page 5Linked to original sources
PubMed1994

Intraoperative monitoring of the visual evoked potential during endoscopic sinus surgery.

Iatrogenic blindness resulting from conventional and endoscopic sinus surgery continues to be a major concern to the head and neck surgeon. A new electrophysiologic monitoring technique has been developed that can help avoid damage to the optic nerve and visual system. The approach involves monitoring the visual evoked potential with presentation of flash stimuli to the eyes. Thirty patients with chronic sinusitis underwent endoscopic sinus surgery with visual evoked potential monitoring. The procedures were carried out with patients under intravenous general anesthesia. Needle cortical electrodes were placed in the scalp. A modified light-emitting diode array/goggle was positioned in front of the patient's closed eyes. A triggered flash of 2 Hz was delivered through the goggle to stimulate the patient's retina. Cortical responses were amplified and averaged for 100 trials. Amplitude and peak-latency changes were monitored to alert the surgeon to any change in the visual response during the surgical dissection. Although no changes in response were noted during dissection, cold-water irrigation and reflected telescopic light could produce variations in the recorded responses, as will be discussed. Visual evoked potential monitoring may prevent a surgeon from continuing a bilateral procedure when there is indication of iatrogenic visual loss from dissection on the first side. Visual evoked potential also reassures the operator that no damage has occurred to the visual pathway at the conclusion of a case. Methods, case selection, operative technique, and documentation of monitoring will be discussed.

Blindness↗
PubMed1996

Intraoperative monitoring of motor evoked potentials: a review of 116 cases.

We reviewed the results of motor evoked potential (MEP) and somatosensory evoked potential (SEP) monitoring during 116 operations on the spine or spinal cord. We monitored MEPs by electrically stimulating the spinal cord and recording compound muscle action potentials from lower extremity muscles and monitored SEPs by stimulating posterior tibial or peroneal nerves and recording both cortical and subcortical evoked potentials. We maintained anesthesia with an N2O/O2/opioid technique supplemented with a halogenated inhalational agent and maintained partial neuromuscular blockade using a vecuronium infusion. Both MEPs and SEPs could be recorded in 99 cases (85%). Neither MEPs nor SEPs were recorded in eight patients, all of whom had preexisting severe myelopathies. Only SEPs could be recorded in two patients, and only MEPs were obtained in seven cases. Deterioration of evoked potentials occurred during nine operations (8%). In eight cases, both SEPs and MEPs deteriorated; in one case, only MEPs deteriorated. In four cases, the changes in the monitored signals led to major alterations in the surgery. We believe that optimal monitoring during spinal surgery requires recording both SEPs and MEPs. This provides independent verification of spinal cord integrity using two parallel but independent systems, and also allows detection of the occasional insults that selectively affect either motor or sensory systems.

Evoked Potentials, Motor↗
PubMed1992

Intraoperative monitoring of tibialis anterior muscle motor evoked responses to transcranial electrical stimulation during partial neuromuscular blockade.

We studied the feasibility of recording motor evoked responses to transcranial electrical stimulation (tce-MERs) during partial neuromuscular blockade (NMB). In 11 patients, compound muscle action potentials were recorded from the tibialis anterior muscle in response to transcranial electrical stimulation during various levels of vecuronium-induced NMB. The level of NMB was assessed by accelerometry of the adductor pollicis muscle after train-of-four stimulation of the ulnar nerve. The compound muscle action potential was also recorded from the tibialis anterior muscle after direct stimulation of the peroneal nerve (M-response) as an alternative means of assessing the degree of NMB. In all patients, tce-MERs could be recorded reliably during anesthesia with N2O and a continuous infusion of sufentanil (0.5 micrograms.kg-1.h-1). An intact train-of-four was present in all patients, and the amplitude of the first twitch was recorded and designated as the control value. Before administration of vecuronium, the M-response amplitude was 9.6 +/- 3.6 (mean +/- SD) mV, and the tce-MER amplitude was 1.21 +/- 0.66 mV. Although administration of vecuronium (0.05 mg/kg) resulted in loss of the mechanical adductor pollicis response in 8 of the 11 patients, the M-response and the tce-MER remained recordable. Subsequently, during an infusion of vecuronium, adjusted to maintain one or two mechanical responses to train-of-four stimulation, the average M-response to peroneal nerve stimulation was 5.2 +/- 2.5 mV (53% of the control value), and tce-MER amplitude was 0.59 +/- 0.36 mV (59% of the control value).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Intraoperative monitoring of ulnar nerve function during replacement of the rheumatoid elbow via the lateral approach.

Neurography of the ulnar nerve was performed pre-, intra- and postoperatively in 8 arms of 7 patients with rheumatoid arthritis operated on with total elbow replacement via the lateral approach. Ulnar nerve decompression was performed in 4 elbows before implantation. A reduction in the amplitude of compound muscle action potential (CMAP) recorded from the abductor digiti minimi on stimulation of the ulnar nerve in the axilla, was observed during elbow dislocation at surgery in all patients, in 5 cases transiently and in 3 cases until the end of surgery. The ulnar nerve had been decompressed in all patients with lasting amplitude reduction. One of them had a mild sensory ulnar nerve palsy, while the other 2 had normal nerve function at the postoperative clinical examination. All 3 had a reduction in the amplitude of compound sensory nerve action potential (SNAP) and 2 of them also in CMAP amplitude at the postoperative neurographic examination. In patients with transient reduction during surgery, the CMAP amplitude quickly normalized on relocation of the elbow and both the SNAP and the CMAP were preserved at the postoperative neurographic examination. The authors conclude that dislocation of the laterally approached elbow carries a risk of ulnar nerve injury, which is not prevented by decompression of the ulnar nerve, but frequent relocation of the elbow during surgery seems important. It is suggested that the ulnar nerve should not be decompressed routinely, and that the dislocated elbow should be frequently relocated.

Action Potentials↗
PubMed2002

[Intraoperative monitoring of pressure within saline-filled, endotracheal tube cuff in adult patients undergoing CO2 laser laryngomicrosurgery].

In laser laryngomicrosurgery, saline is injected into the endotracheal tube cuff to prevent airway fire. Utilizing regression analyses, we investigated the relation between the saline volume required to obtain optimal intracuff pressure and tracheal diameters in patients undergoing laser laryngomicrosurgery as well as in model tracheas. Although excellent linear correlations were found between the saline volume and the diameter of model tracheas, no significant linear or non-linear correlation was found between the saline volume and the patient's tracheal diameter. In the model tracheas, a rate of rise in the intracuff pressure caused by increments in the injected volume was far steeper when saline was injected into the cuff than when air was injected into the cuff. Addition of only 0.2 ml saline could result in large (> 50 mmHg) increases in the intracuff pressure. Also in patients, addition of 1 ml could result in notable (> 50 mmHg) increases in the intracuff pressure. These results suggest that the saline volume necessary to obtain optimal intracuff pressure is difficult to be predicted from the patient's tracheal diameter, and that slight increases in the saline volume may cause excessive increases in the intracuff pressure. The intracuff pressure should be tightly monitored in patients undergoing laser laryngomicrosurgery.

Adult↗
PubMedDate not supplied

Repetitive vs. single transcranial electrical stimulation for intraoperative monitoring of motor conduction in spine surgery.

We studied the effectiveness of single and repetitive transcranial electrical stimulation to activate motor tracts under partial neuromuscular blockade and total intravenous anesthesia. During spinal surgery, in 10 patients, the latency and amplitude of the evoked abductor pollicis brevis muscle response after cortical stimulation was calculated and compared. The number of responses evoked by the double (pair) pulse stimulation was significantly higher (p = 0.0191) than single pulse stimulation. Repetitive stimulation caused more responses than single (p = 0.0001) or double stimulation (p = 0.0253). An increase of interstimulus interval from 1-3 msec did not significantly increase the motor response with the double pulse or repetitive stimulations. Varying the number of electrical pulses per train stimulation from 3-9 did not significantly change latency (P > 0.05) or amplitude (P > 0.05) of the motor response. The findings suggest that use of repetitive stimulation of the motor cortex is an effective method to activate motor pathway during spinal surgery.

Adolescent↗