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At least 235 records · Page 13Linked to original sources
PubMed2003

Intraoperative monitoring of cochlear nerve compound action potential in cerebellopontine angle tumour removal.

Cochlear nerve compound action potential (CNAP) provides a real-time auditory evoked potential. Because of technical difficulty, CNAP monitoring has not been popular during the removal of cerebellopontine angle (CPA) tumour. To clarify the efficiency of intraoperative CNAP monitoring, we designed an intracranial electrode for CNAP monitoring and performed the simultaneous monitoring of CNAP and auditory brainstem response (ABR) in 10 patients undergoing CPA tumour removal in an attempt to preserve hearing. ABR recordings during microsurgical tumour removal were unsatisfactory in 6 patients because of severe artifacts. Reliable CNAP recordings were obtained without artifacts in all 10 patients throughout surgery. Eight patients preserved useful hearing after tumour removal, and the CNAP amplitude reflected the postoperative hearing. The newly designed intracranial electrode enables CNAP monitoring predicting the postoperative hearing more reliably than ABR. CNAP monitoring is efficient to improve the hearing preservation rate following CPA tumour removal.

Action Potentials↗
PubMed1988

[Transcranial Doppler sonography as an intraoperative monitoring procedure. Initial experiences in aortocoronary bypass operations].

Changes in blood velocity in the middle cerebral artery (MFV) were investigated by transcranial Doppler sonography (TCD) in 24 patients undergoing aortocoronary bypass grafting before, during, and after extracorporeal circulation (ECC). Simultaneously, mean arterial blood pressure (MABP), PaCO2, PaO2, and hematocrit were recorded. During ECC, an increase in MFV could be observed that was most pronounced during the early bypass stages. After ECC, MFV decreased slightly but was significantly higher than before ECC. No linear relationship between MFV and MABP could be registered except for the early bypass stage. Neither duration of ECC nor aortic clamping time showed any correlation with MFV augmentation. Mean PaCO2 was held constant (36 mmHg) with PaO2 being at least 120 mmHg. After removal of the aortic clamp, high-frequency Doppler signals probably caused by air or fragment embolization were detected in some patients. Our data support previous observations of increased cerebral blood flow during nonpulsatile ECC. During short episodes of low-pressure perfusion after initiation of ECC, cerebral autoregulation seemed impaired. However, our results do not support the concept of complete loss of autoregulation during ECC. Compared to the xenon technique of measuring cerebral blood flow, TCD allows noninvasive and continuous evaluation of cerebral hemodynamics, thus offering new possibilities of monitoring cerebral blood supply intraoperatively.

Adult↗
PubMed1982

Intraoperative monitoring of brain-stem auditory evoked potentials.

Intraoperative brain-stem auditory evoked potentials (BAEP's) were monitored in 46 patients undergoing intracranial surgery for a variety of pathological conditions to determine whether this technique was capable of providing useful information to the operating surgeon. Intraoperative BAEP's were unchanged throughout surgery in 34 patients (74%), and these individuals had no postoperative hearing deficits. Four patients (9%) developed an abrupt ipsilateral loss of all waveform components beyond Wave I and had postoperative evidence of a pronounced hearing loss in the affected ear. An additional patient demonstrated BAEP loss contralateral to the side of surgery, and this was associated with subsequent signs of severe brain-stem dysfunction. Seven patients (15%) developed intraoperative delays of BAEP waveform latency values, but maintained recognizable waveforms beyond Wave I. Postoperatively, their hearing was either normal or mildly impaired, and there were no indications of other brain-stem abnormalities. This group represents the individuals who may have been benefited by evoked potential monitoring, since corrective surgical measures were taken when latency delays were observed. Intraoperative BAEP's can be reliably and routinely recorded in an operating room environment. They provide a good predictor of postoperative auditory status, and may have prevented permanent neurological deficits in a small segment of patients by alerting the surgeon to potentially reversible abnormalities.

Brain Diseases↗
PubMed2005

[Intraoperative monitoring in vascular surgery].

Despite the variety of possibilities to evaluate hemodynamics, ultrasound-in particular duplex sonography-is the method of choice. With an increasing number of endovascular procedures, intraoperative angiograms will remain indispensable. The method of angioscopy is reserved for individual cases. Indirect monitoring in carotid surgery will keep its significance. This includes measuring somatic evoked potentials as well as transcranial duplex sonography, with regard to the increasing importance of plaque morphology and possible neurological consequences. The general recommendation of applying at least one intraoperative control method is necessary in carotid surgery, even if intraluminal shunts are routinely implanted. In addition, quality control of the peripheral vascular system should be sufficiently documented by using one or more methods of examination. So far, in prospective randomized trials, results have not improved by applying intraoperative monitoring methods. Nevertheless, they are indispensable for the careful vascular surgeon and can help to avoid complications and revision with worse prognosis in some cases.

Aneurysm, Ruptured↗
PubMed1999

What intraoperative monitoring makes sense?

The routine practice of monitoring oxygenation, ventilation, circulation, and temperature during surgery is now the standard of care. However, with the possible exception of pulse oximetry and capnography, extensive physiologic monitoring has not been shown to reduce the incidence of adverse anesthetic-related events. Monitors are useful adjuncts, but they alone cannot replace careful observation by a vigilant anesthesiologist.

Anesthesia↗
PubMed2000

Intraoperative monitoring for hearing preservation and restoration in acoustic neuroma surgery.

The present article reports on our experience with hearing preservation during 158 acoustic neuroma (AN) operations via the retrosigmoid-transmeatal (RS-TM) approach with the aid of intraoperative auditory monitoring. Several auditory monitoring methods are described. Of these, the bipolar cochlear nerve action potential (CNAP) was found to be the most helpful in preserving hearing. Of 106 patients with useful hearing preoperatively, more than 50% had useful hearing after surgery. Electrical auditory brainstem responses were useful in the placement of an auditory brain stem implant (ABI) in 4 patients with neurofibromatosis type 2 (NF2). All 4 reported speech perception benefit and use their ABIs regularly in their lives. It is our firm belief that intraoperative auditory monitoring has a pivotal role in the preservation and restoration of hearing in AN surgery.

Journal Article↗
PubMed1989

Real-time intraoperative monitoring during neurosurgical and neuroradiological procedures.

A real-time intraoperative evoked potential (EP) monitoring system is described and evaluated. Unique features include (1) online artifact rejection to reduce noise contamination, (2) optimum digital filtering to improve the signal-to-noise ratio of the EP signal, (3) statistically defined confidence intervals to determine significant EP peak latency deviations, and (4) sliding windows of EP subaverages of various sizes to minimize feedback time to the surgeon. The reliability and validity of this system were determined by comparison with conventional intraoperative EP averaging and by examining the correlation of EP parameter changes with concurrent surgical and radiological manipulations. This system was clearly superior to conventional averaging systems. Reliable EPs could be obtained from neurologically compromised patients within the electrically hostile operating room environment, in cases in which conventional averaging failed to extract a stable EP signal. EP update times of 10-20 s were quite common and allowed direct moment-to-moment correlations with surgical and radiological events. Case histories are presented that show the utility of this system for aiding in the prevention of neurological complications. This utility is examined for neurosurgical and neuroradiological procedures involving spinal cord, brainstem, midbrain, and cortical structures, and affecting the somatosensory, motor, auditory, and visual system pathways.

Adult↗
PubMed2006

Prevention of ischemic neurologic injury with intraoperative monitoring of selected cardiovascular and cerebrovascular procedures: roles of electroencephalography, somatosensory evoked potentials, transcranial Doppler, and near-infrared spectroscopy.

All neuromonitoring techniques, although imperfect, provide useful information for monitoring cardiothoracic and carotid vascular operations. They may be viewed as providing complementary information, which may help surgical technique and, as a result, possibly improve clinical outcomes. As of this writing, the efficacy of TCD and NIRS monitoring during cardiothoracic and vascular surgery cannot be considered established. Well designed, prospective, adequately powered, double-blind, and randomized outcome studies are needed to determine the optimal neurologic monitoring modality (or modalities), in specific surgical settings.

Brain↗
PubMed1993

[Intraoperative monitoring for spinal cord tumor by spinal cord evoked potential following unilateral spinal cord stimulation].

We described our experiences with intraoperative spinal cord monitoring in 6 cases of spinal cord tumor. During the operation, spinal cord evoked potential following unilateral spinal cord stimulation was recorded from subdural monitoring electrodes. This series included two cases of intradural extramedullary tumor (one case each of neurinoma and of meningioma) and four cases of intramedullary tumor (2 cases of cavernous angioma, one case each of ependymoma, and of glioblastoma multiforme). Before the removal of the tumor, the spinal cord evoked potential showed lower amplitude or no response on the more affected side in all 6 cases. During the operation, the different intraoperative changes were shown on each side. The authors think that the detection of unilateral damage to the spinal cord is possible in spinal cord evoked potential using unilateral spinal cord stimulation.

Adult↗
PubMed1992

Method of intraoperative monitoring of neuromuscular function and residual blockade in the recovery room.

We evaluated the method used intraoperatively to assess the degree of neuromuscular blockade prior to pharmacologic reversal to determine its role in preventing residual blockade in the postanesthesia care unit (PACU). We studied 38 patients who received a nondepolarizing muscle relaxant during general anesthesia for carotid endarterectomy or thoracotomy. The anesthesiologist assessed the degree of neuromuscular blockade intraoperatively prior to pharmacologic reversal either by the standard method of visually counting the number of evoked thumb twitches elicited by supramaximal train-of-four stimulation of the ulnar nerve (i.e., thumb train-of-four count), or by an alternative method such as 1) visually counting the number of evoked orbicularis oculi muscle twitches elicited by supramaximal train-of-four stimulation of the facial nerve, or 2) observing the patient for clinical evidence of partial recovery (e.g., swallowing or attempts to breathe). Residual blockade in the PACU was defined as 1) a train-of-four ratio less than 0.70 (measured by a mechanomyograph), or 2) the inability of the patient to perform clinical tests of neuromuscular function (e.g., a sustained head lift for 5 seconds) and evidence of neuromuscular weakness that was resolved following administration of edrophonium. Five of the 22 patients (23%) in whom one of the alternative methods was used had residual blockade in the PACU; none of the 16 patients with a thumb train-of-four count of 3 or 4 before pharmacologic reversal of NMB had residual blockade in the PACU (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia Recovery Period↗
PubMed1994

[Wall stress in the assessment of left ventricular function in surgery of abdominal aortic aneurysm. Validity and importance of transesophageal echocardiography (TEE) in intraoperative monitoring].

OBJECTIVE: To verify the applicability and the clinical significance of left ventricular wall stress determinations by intraoperative transesophageal echocardiography (TEE) during resections of abdominal aortic aneurysms. DESIGNS: Prospective comparison of changes in left ventricular wall stress between two groups of patients with and without coronary artery disease. SETTING: Operatory room of Universitary Institute. PATIENTS: Twenty-three patients with abdominal aortic aneurysms; 8 had clinically evident coronary artery disease (CAD+); 15 patients did not have clinical or electrocardiographic evidence of coronary artery disease (CAD-). INTERVENTIONS: Resection of the aortic aneurysm and insertion of a synthetic prosthesis. MEASUREMENTS AND MAIN RESULTS: During operation transesophageal monitoring of left ventricular volumes and wall stress was performed during induction of anesthesia (T1), for two minutes after aortic clamping (T2), at the end of the proximal anastomosis (T3), for two minutes after aortic declamping (T4) and at the end of the procedure (T5). Circumpherential stress at end systole (sES) and end diastole (sED) was more sensitive than hemodynamic and volumetric parameters in detecting changes i function of the ischemic myocardium. In detail we observed: a significant increase of sES in CAD+versus CAD- at T2: 98 (sd 18) vs 83 (sd 14) 10(3) dyne/cm2. a significant increase of sED in CAD + versus CAD- at T2: 28.5 (sd 6) vs 22 (sd 4.5) 10(3) dyne/cm3. a similar trend of sES and sED at T4: 73 (sd 20.5) vs 46 (sd 15) 10(3) dyne/cm2 and 31 (sd 12) vs 16 (sd 7.7) 10(3) dyne/cm2 respectively. a significant increase of sED in CAD + at T5 (about 20' after T4): 26.5 (sd 9.5) vs 16 (sd 5.2) 10(3) dyne/cm2 which is expression of a persistent reduction of ventricular compliance in the ischemic patients. CONCLUSIONS: Wall stress modifies MVO2 and subsequently is sensitive in detecting changes in myocardial performance. TEE could valuably integrate routine hemodynamic monitoring of patients with coronary heart disease who undergo surgical resection of abdominal aortic aneurysms.

Aged↗
PubMed1995

Intraoperative monitoring of median nerve somatosensory evoked potentials in cervical syringomyelia: analysis of 28 cases.

Intraoperative median nerve somatosensory evoked potentials (SEP) were monitored in 28 patients undergoing surgery for cervical or cervicothoracic syringomyelia. Analysis was focused on SEP components N13 (spinal cord), P14 (brain stem), and N20 (cortex). N13 was lacking in nearly 87% of the patients (due to a combined effect of syringomyelia and general anesthesia) and never recovered. P14 showed a significant (> 10%) intraoperative latency increase in two patients; this was irreversible in one patient who had a postoperative worsening of sensory function. N20 showed no relevant alterations. Pure motor deficits after surgery were not predicted by SEP monitoring. In conclusion, intraoperative P14 recording helped to identify harm to the dorsal columns and probably prevented the cord from irreversible damage in one case, whereas N13 recording did not contribute to the monitoring of spinal cord function during surgery for syringomyelia.

Adult↗
PubMed1991

Intraoperative monitoring of the somatosensory evoked potentials and cerebral blood flow during aneurysm surgery--safety evaluation for temporary vascular occlusion.

Somatosensory evoked potentials (SEPs) and cerebral blood flow (CBF) were monitored during temporary vascular occlusion in 67 aneurysm operations to evaluate the usefulness of SEP as an indicator for cerebral ischemia. The SEP N20 component completely disappeared during temporary vascular occlusion in 24 cases, 23 of which demonstrated complete recovery following recirculation and had no postoperative neurological sequelae. The only one with postoperative sequelae demonstrated rapid, within 1 minute, loss of N20 followed by no recovery. Another eight cases showed prolongation of central conduction time during vascular occlusion and had no postoperative sequelae. The SEP N20 attenuation reflected the CBF reduction in the middle cerebral artery (MCA) territory during MCA occlusion. However, CBF changes in the internal carotid artery (ICA) territory during ICA occlusion greatly varied. No detectable changes in SEP were found during anterior cerebral artery occlusion for anterior communicating artery aneurysms. This study indicates that intraoperative SEP monitoring is useful to detect ischemia in the MCA territory and that rapid disappearance of the N20 component is a danger signal.

Brain Ischemia↗