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At least 343 records · Page 19Linked to original sources
PubMed1989

[Intraoperative monitoring: visual evoked potentials in surgery of the sellar region].

During 18 sellar and perisellar operations the optic tract was monitored by visual evoked potentials (VEP). Deteriorations of the cortical responses were recorded in 73%. In this patients there was no close correlation between the intraoperative findings and the postoperative visual function. Only in those patients who showed no remarkable intraoperative changes VEP seemed to be of reliable prognostic value.

Adenoma↗
PubMed1982

Intraoperative monitoring of brain-stem auditory evoked potentials.

Brain-stem auditory evoked potentials (BAEP) were monitored during 545 neurosurgical operations in the cerebellopontine angle. The BAEP were irreversibly obliterated in five patients who required deliberate section of the auditory nerve. Technical difficulties interfered with monitoring in three cases, and three patients had deafness and absent BAEP preoperatively. Reversible alterations in BAEP were seen during 32 operations, with recovery after as long as 177 minutes of virtually complete obliteration. Changes in BAEP were associated with surgical retraction, operative manipulation, positioning of the head and neck for retromastoid craniectomy, and the combination of hypocarbia and moderate hypotension. In 19 cases, waveforms improved after specific interventions made by the surgeon or anesthesiologist because of deteriorating BAEP. In 13 other cases, BAEP recovered after maneuvers not specifically related to the electrophysiological monitoring, most often completion of operative manipulation. Whenever BAEP returned toward normal by the end of anesthesia, even after transient obliteration, hearing was preserved. Irreversible loss of BAEP occurred only when the auditory nerve was deliberately sacrificed. The authors conclude that monitoring of BAEP may help prevent injury to the auditory nerve and brain stem during operations in the cerebellopontine angle.

Adult↗
PubMed1989

[Intraoperative monitoring of cerebral function and carotid hemodynamics during carotid endarterectomy].

The authors investigated the hemodynamics and monitored the cerebral function to perform the carotid endarterectomy (CEA) safely. The hemodynamics were investigated by measurements of carotid arterial blood flow by an electromagnetic flow meter before and after CEA. And a doppler flow meter applied directly to the carotid arteries to analyze the flow parameters such as peak frequencies (PF), mean frequencies (MF), mode frequencies (Mo F) and % window. We used routinely our specially designed shunt system during surgery, by which stump pressure of the ICA could be measured easily. The cerebral function was evaluated by the amplitude of N20-P25 component of somatosensory evoked potential (SEP). Flow parameters of doppler sounds demonstrated significant changes such as inversion of MF and Mo F, decrease in % window at the poststenotic ICA in the severe stenosis group. By these doppler sounds the extension of stenotic lesion could be detected clearly. The ICA flow showed evidently low values in patients with more than 80% stenosis, which was improved by CEA. With our specially designed T-tube shunt system, stump pressure, side pressure and direct pressure of the ICA could be monitored easily. The mean stump pressure was 52 mmHg and systemic arterial blood pressure was 99 mmHg on the average. SEP revealed evident changes during temporary occlusion in 10 out of 41 patients, which improved following the reflow with the shunt system. Mean stump pressure in the 11 patients was 33 mmHg, and that in the remaining patients were 59 mmHg on the average.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Continuous intraoperative monitoring of hepatic blood perfusion using a noninvasive surface electrode.

Continuous noninvasive measurement of local blood flow at one or more chosen sites will be useful during experiments on the liver, during liver surgery, or after hepatic transplantation. We have compared a Clark-type flow-dependent oxygen electrode having a 3-mm-diameter cathode applied to the surface of rabbit liver to an electromagnetic flowmeter (EMF) on the portal vein. Reduction in portal flow (ranging from 4 to 100% and maintained over 2 min), correlated with reduction in electrode output (r = 0.944, P less than 0.001). Electrode output was independent of systemic arterial PO2 (ranging from 85 to 340 mm Hg) (P greater than 0.99) and thus of oxygen in inspired gases. These results indicate that this electrode gives a continuous indication of portal venous inflow when hepatic central inflow is undisturbed and may thus prove to be a useful tool in the clinical assessment of liver perfusion.

Animals↗
PubMed1988

Effect of click-polarity on abnormality of intraoperatively monitored brainstem acoustic evoked potentials.

The configuration of brainstem acoustic evoked potentials (BAEP) is influenced by the type of click stimuli used and may thus affect detectability of abnormalities. In a group of 19 patients with lesions in the posterior fossa BAEP were recorded pre- and intraoperatively. Repeat recordings were performed in each patient in two alternating series with rarefaction and condensation click stimuli. The findings demonstrated that intraoperative potential changes in latency and amplitude were different between the two stimulation modes, but did not vary significantly in their incidence. It was also not possible to predict from the preoperative BAEP which click polarity would demonstrate intraoperative changes more markedly, taking latency and amplitude as parameters. Two conclusions are drawn from this study: None of the two stimulation modes is superior in detecting intraoperative changes and therefore no recommendation can be made which click polarity to use. When working with only one click polarity it is recommended to use occasional control recordings with the other click polarity.

Acoustic Stimulation↗
PubMed1985

Limitations of brain stem auditory evoked potentials for intraoperative monitoring during a posterior fossa operation: case report and technical note.

We have encountered an example of the insensitivity of brain stem auditory evoked potentials (BAEPs) for monitoring the brain stem during a posterior fossa operation. The addition of somatosensory evoked potential recording to conventional BAEP protocols is readily accomplished and is likely to improve the sensitivity of intraoperative electrophysiological assessment of brain stem function.

Brain Stem↗
PubMed1989

Considerations after intraoperative monitoring of somatosensory evoked potentials during carotid endarterectomy.

Somatosensory evoked potentials (SEPs) following median nerve stimulation were used to monitor cerebral function during 26 carotid endarterectomies. The patients with minor SEP variations had no neurological deficits on regaining consciousness while the one with more serious SEP variations had a transient deficit. The method thus seems useful in the early detection of ischemic brain impairment.

Aged↗
PubMed1986

Intraoperative monitoring in vascular surgery.

Doppler ultrasound and real-time B-mode ultrasonic imaging are useful techniques to monitor the technical success of reconstructive vascular operations. Gas-sterilized CW or pulsed Doppler probes permit audible or spectral detection of normal and abnormal blood velocity patterns associated with intimal flaps, thrombotic or platelet aggregates, retained venous valve cusps or arteriovenous fistulas. Real-time ultrasonic B-mode imaging allows detection of technical defects or thrombotic debris which is of particular importance in minimizing stroke or recurrent lesions following carotid endarterectomy. These ultrasonic techniques should become routine adjuncts for surgeons interested in defining localized pathology and hemodynamics, assuring technical integrity, detecting intraoperative defects, and predicting favorable outcome of vascular reconstruction procedures.

Endarterectomy↗
PubMedDate not supplied

Intraoperative monitoring of ischiatic nerve function with sensory evoked potentials.

Serial recordings of sensory evoked potentials (SEP) generated in response to stimulation of each tibial nerve were obtained from 23 anesthetized dogs. Five dogs were anesthetized for 3 hours to evaluate changes in serial SEP during general anesthesia. Nonsurgical and surgical manipulations were performed on one hind limb of five dogs to determine the effects of limb positioning and nerve retraction on SEP. In 13 dogs, the ischiatic nerve was exposed surgically and retracted until the SEP deteriorated and disappeared, to determine the relationship between amount of tension on the nerve and the time to complete deterioration of the SEP. Sensory evoked potential waveforms, which consisted of two to five peaks, were stable throughout the anesthetic period. The first two peaks were the most stable. Latency of the first two peaks was the easiest and most reliable parameter to evaluate. Although the peak latency in recordings from the superior hind limb was always slightly longer, SEP recordings from the inferior limb were good controls to monitor nerve function. There was considerable variation in sensitivity to nerve retraction. The technique proved to be a reliable way to monitor nerve function in normal anesthetized dogs.

Anesthesia, General↗
PubMed1986

[Intraoperative monitoring in artificial respiration of premature and newborn infants. II. Monitoring of arterial oxygenation].

Monitoring of adequate arterial oxygenation serves to avoid periods of hypoxaemia and hyperoxaemia with potentially life threatening or organ-damaging sequelae. Basic clinical monitoring, i.e., inspection and auscultation, is mandatory. In all infants, paO2 may be continuously and indirectly monitored by measurement of transcutaneous pO2 (tcpO2). The use of pulse oximetry for non-invasive measurement of arterial oxygen saturation (SaO2) is still undergoing clinical testing. Invasive monitoring of gas exchange is essential in prolonged or intrathoracic interventions as well as in neonates with cardiopulmonary problems. paO2 can be estimated by capillary blood gas analysis; arterial blood gas analysis, however, is required for exact determination of paO2 and of the arterio-cutaneous pO2 gradient (atcDO2). Intraarterial fibre optic determination of oxygen saturation or determination of paO2 with an intraarterial Clark electrode does not appear to be well suited for intraoperative conditions.

Anesthesia, General↗
PubMed1987

Are flash-evoked visual potentials useful for intraoperative monitoring of visual pathway function?

Flash-evoked visual potentials (VEPs) recorded from the scalp were used in a series of 35 patients with tumors along the visual pathway: 3 orbital tumors, 25 perisellar tumors, 4 intraventricular tumors, and 3 occipital lesions. Preoperatively, various combinations of impaired visual fields and visual acuity were observed in over 90% of the patients. A postoperative decrease in visual function was observed in 3 cases. Of the 25 perisellar lesions, 13 were operated through a standard frontotemporal craniotomy and 12 were operated through a transnasal-transsphenoidal approach. VEPs were highly susceptible to volatile anesthetics, and there was a significant incidence of spontaneous latency increases and amplitude decreases in a large number of patients. There was an unacceptably high number of cases with significant VEP alteration occurring without concomitant visual function change. During trepanation or the transnasal approach, a reversible potential loss was observed in 11 patients, a profoundly altered wave form was seen in 8 cases, and a loss of single peaks was observed in 15 patients. During dissection of the tumor, a reversible potential loss or a potential with unidentifiable peaks was found in 25 cases; however, the VEPs recovered during closure or in the recovery room. There was no correlation between intraoperative VEP changes and the postoperative changes in visual function. In only 1 patient with an insignificant postoperative decrease in visual acuity from 0.4 to 0.3 was there a concomitant intraoperative potential loss. The major conclusion of our findings is that light-emitting diode flash-evoked VEPs demonstrate intraoperative changes that appear too early and too prominently to be caused solely by manipulation of the optic pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2003

Use of myocardial tissue Doppler imaging for intraoperative monitoring of left ventricular function.

BACKGROUND: Detection of myocardial ischaemia during surgery is usually by assessment of regional wall motion using two-dimensional transoesophageal echocardiography (TOE). Tissue Doppler imaging (TDI) may assist this assessment and improve its accuracy. METHODS: We measured peak myocardial velocities in the anterior mid-wall of the left ventricle by TOE and pulsed-wave TDI in addition to transmitral flow velocity, two-dimensional echocardiography and cardiovascular variables. We studied 42 patients before and after coronary bypass surgery with left internal mammary artery grafts. RESULTS: Peak systolic and early and late diastolic velocity measurements of the anterior mid-wall were obtained in all patients. Variation between and within observers was small (<6%). Peak systolic thickening velocity correlated with visual assessment of anterior wall motion score, fractional area change of the left ventricle and left ventricular systolic wall stress. Because of the wide overlap of systolic velocity between the segments with normal and abnormal wall motion, it was not possible to separate normal from abnormal segments on the basis of TDI-derived velocity alone. The diastolic velocity in the anterior wall reflected the transmitral filling pattern. After surgery, the peak systolic and late diastolic anterior wall velocities increased (from 4.2 (95% confidence interval 4.0, 4.7) to 5.7 (4.8, 6.3) cm s(-1) and from 3.5 (3.2, 3.9) to 6.0 (5.1, 6.9) cm s(-1) respectively), while the ratio of early to late diastolic velocity decreased from 1.5 (1.2, 1.7) to 1.0 (0.8, 1.2). TDI changes characteristic of new myocardial ischaemia were not seen in any patient. CONCLUSION: Intraoperative measurement of TDI in the anterior wall of the left ventricle is feasible and provides additional quantitative information on both regional and global systolic and diastolic function. We found changes in myocardial velocities indicating improvement in the systolic and impairment in the diastolic function of the anterior wall of the left ventricle immediately after mammary artery grafting.

Aged↗
PubMed1985

Observations on 100 patients with continuous intraoperative monitoring of intramyocardial pH. The adverse effects of ventricular fibrillation and reperfusion.

Intramyocardial pH and temperature data recorded in 100 patients undergoing cardiac operations were analyzed to elucidate the effects of ventricular fibrillation and reflow. All patients underwent a single period of aortic clamping. Systemic hypothermia (25 degrees C) and intermittent cold crystalloid K+ cardioplegia were employed for myocardial protection. Baseline myocardial pH was 6.88 +/- 0.03 at a temperature of 36.5 degrees +/- 0.2 degree C. During the period of hypothermic ventricular fibrillation prior to aortic clamping, ventricular fibrillation did not affect myocardial pH in 45 patients (Group 1). In 21 patients (Group 2), it caused a significant drop in intramyocardial pH despite cooling. Group 2 patients had a higher incidence of valvular heart disease and left ventricular hypertrophy. They also exhibited low intramyocardial pH values during the subsequent periods of aortic clamping and reflow, indicating inadequate myocardial protection. During the period of reflow, reperfusion acidosis (pH less than 6.8 at 32 degrees C) was encountered in 39 patients (Group B) as opposed to 37 patients (Group A) whose pH remained well above 6.8 during that period. Group B patients had a higher incidence of valvular heart disease and left ventricular hypertrophy, tended to have more ischemic anterior walls prior to cardiopulmonary bypass, sustained longer periods of aortic clamping, had intramyocardial pH evidence of suboptimal protection during aortic clamping, were affected more adversely by ventricular fibrillation during reflow, and tended to have a higher operative mortality. Thus: Depending on the underlying myocardial disease, the adequacy of protection during aortic clamping, and the conditions of reflow, intramyocardial pH in man can fall significantly during ventricular fibrillation and reflow. The metabolic correlate of injury with reflow is a reperfusion acidosis that can reach as low as pH 5.98. When encountered, reperfusion acidosis can be minimized by prompt defibrillation.

Adult↗
PubMed1981

Carotid endarterectomy. The unreliability of intraoperative monitoring in patients having had stroke or reversible ischemic neurologic deficit.

We reviewed 125 patients who had had stroke or reversible ischemic neurologic deficits (RIND) and who underwent carotid endarterectomy, with follow-up extending to six years. Phase I patients (n = 36) had endarterectomy and shunt placement at operation by surgeons' preference. The rate of postoperative neurologic deficit was 8%. Phase II patients (n = 36) had endarterectomy monitored by EEG and stump pressures. Postoperative deficits occurred in 9%. The EEGs and stump pressures in these patients were "normal"; therefore, no shunt was used. Phase III patients (n = 41) had endarterectomy again monitored by EEG and stump pressure. Despite normal EEGs or stump by EEG and stump pressure. Despite normal EEGs or stump pressure, all patients underwent endarterectomy with a temporary indwelling shunt. No complications occurred. In 368 patients operated on for transient ischemic attacks alone, the operative stroke rate was 1.6%. Stump pressure and EEG are unreliable indicators of cerebral perfusion during carotid endarterectomy in patients who have suffered stroke or RIND. Use of a temporary shunt is indicated in all of these patients.

Adult↗
PubMed1988

Assessment of reversible cerebral ischaemia in man: intraoperative monitoring of the somatosensory evoked response.

Central conduction time (CCT) has been monitored in 37 patients undergoing temporary arterial occlusion in aneurysm surgery. 17 patients had internal carotid, 17 had middle cerebral, and 4 had basilar artery occlusion. Internal carotid or middle cerebral artery occlusion lasting less than 12 minutes has not been associated with postoperative morbidity, in any case without appreciable change in CCT after occlusion. Prompt prolongation of CCT was warned the surgeon, but CCT prolongation up to 10 ms could occur without permanent neurological deficit, except in one Grade 4 patient. 10 of 18 patients who lost the N 20 cortical potential showed postoperative neurological deficit, which was promptly recoverable in 7 patients. The speed of loss or recovery of N 20 enabled a patients's prognosis to be predicted. Irrecoverable postoperative deficit is unlikely if the N 20 takes longer than 4 minutes to disappear, to reappears within 20 minutes after recirculation.

Evoked Potentials, Somatosensory↗
PubMed1988

Intraoperative monitoring of the motor function: experimental and clinical study.

Manipulation of the lesions adjacent to the primary motor area or the motor pathway is troublesome for neurosurgeons because they lack an effective method to determine the primary motor area or to monitor motor function in the operative room. It will be of great value to establish a monitoring method of the corticospinal tract under general anaesthesia. We recorded the motor evoked potential (MEP) from direct motor cortex stimulation in cats and showed that it derives almost purely from the corticospinal tract. Then we used this technique during the operation of the resection of tumours near the primary motor area or the motor pathway. 1. Experimental study: Twenty adult cats were used in this study. Recording electrodes were flexible bipolar catheter electrodes inserted into the spinal epidural space. Stimulating electrodes were silver ball electrode on the cortex (anode) and needle electrode in the temporal muscle (cathode). Stimulation of 4-24 V, 5-10 Hz and 0.2 msec in duration were done and evoked potentials signals were averaged 60 to 512 times. MEP with multiple peaks was obtained that had a 112 msec conduction velocity in the spinal cord. We found the same signals from the stimulation of ipsilateral cerebral peduncle. Radiofrequency lesioning of ipsilateral cerebral peduncle produced a loss of MEP. These results show that MEP derives from the corticospinal tract. Significant wave form change, with components of short latency, was noted by the excessively intense stimuli. We supposed that superimposition of the signals from the extrapyramidal pathways, excited in the brain stem, results in this change.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Intraoperative monitoring of the electrocochleogram and the preservation of hearing during acoustic neuroma excision.

We have monitored the electrocochleogram (ECochG) of 24 patients, using a transtympanic electrode, during acoustic neuroma excision. All patients had unilateral tumours with good preoperative hearing and complete excision was achieved in each case. Of the 24 patients, seven retained some hearing, however, a further two patients had normal ECochG waveforms at the end of operation but were nevertheless deaf. Thus, there is not an invariable correlation between immediate preservation of the ECochG and hearing. As expected, tumour size was important in hearing preservation. Five of seven patients with tumours less than 1.5 cm in diameter retained some hearing after operation, whereas 15 of 17 patients with tumours greater than 1.5 cm in diameter were deaf.

Audiometry, Evoked Response↗