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PubMed1988

Intraoperative monitoring of evoked potentials with a spiral scalp electrode. Technical note.

Monitoring evoked potentials from the brain for prolonged periods during neurosurgical procedures ideally requires attached scalp electrodes that may be placed in a sterile field. The limitations of conventional surface and percutaneous electrodes in the operating room environment have led to the development of a disposable curved-needle electrode which is inherently self-retaining. Clinical results have demonstrated the advantages of this new electrode over other electrodes currently used for intraoperative neurophysiological monitoring.

Electrodes↗
PubMed1996

F-wave recordings from nasal muscle for intraoperative monitoring of facial nerve function.

The generation of the F-wave in muscle after peripheral motor nerve stimulation depends upon the functional integrity of the entire motoaxon between its axon hillock and the motor endplates. Cerebellopontine angle (CPA) surgery bears the risk of damaging the facial nerve in its root exit zone; functional degradation should therefore be reflected by changes of the nasal muscle F-wave. Constant current pulses supraliminal for direct (M) muscular responses were applied subcutaneously to the zygomatic branch of the facial nerve ipsilateral to the operated side, EEG needle electrodes were placed in the nasal muscle and referred to glabella for recording of myoelectric activity. Anesthesia was achieved by application of fentanyl, midazolame and N2O and low doses of short acting muscular relaxants; the above-mentioned narcotics did not influence F-wave recordings, whereas the administration of muscle relax ants was often deleterious to F-wave monitoring. 22 patients with different tumors in the CPA, the cerebellum or the vicinity of the brainstem were subject to this monitoring procedure up to now. F-wave monitoring was effective in 12/22 cases. In 7/12 patients the signal was stable without any resulting dysfunction postoperatively. In 3/12 cases changes in amplitude and/or latency were observed indicating a subsequent facial palsy of a moderate degree. In 2 cases the F-wave was lost-these suffered from a facial paralysis afterwards. As an illustrative case the course of one of these is pointed out. In 10/22 procedures F-wave monitoring was ineffective due to the prolonged administration of muscle relaxants. The F-wave appears to be a valid tool for intraoperative prognosis of postoperative facial nerve function in CPA surgery. The borderlines of F-wave changes indicating damage to neural function by surgical manipulation are to be defined next.

Adult↗
PubMed2001

[Transesophageal echocardiography as intraoperative monitoring for the resection of an intra-atrial tumor].

Fibrolamellar hepatocellular carcinomas (FLHCC) can grow into the inferior vena cava and the right atrium thus rendering it impossible to insert a pulmonary artery catheter or increasing the risk of tumor embolisation. We report of a young patient with intraatrial growth of a FLHCC where intraoperative transesophageal echocardiography (TEE) instead of a pulmonary artery catheter for continuous monitoring of hemodynamics was used. Hemodynamic parameters as well as the surgical result could easily be assessed.

Adolescent↗
PubMed2002

Noninvasive intraoperative monitoring of carbon dioxide in children: endtidal versus transcutaneous techniques.

BACKGROUND: The current study prospectively compares the accuracy of the intraoperative use of transcutaneous (Tc) and endtidal (PE) CO2 monitoring during surgical procedures in 30 paediatric patients, ranging in age from 6 months to 15 years (6.15 +/- 4.35 years) and in weight from 4.7 to 73 kg (24.9 +/- 18.2 kg). METHODS: Following calibration and an equilibration time for the TcCO2 monitor, arterial blood gas samples were obtained as clinically indicated. A total of 64 sample sets (PaCO2, PECO2 and TcCO2) were obtained from the 30 patients. RESULTS: The PECO2 to PaCO2 difference was 0.6-0.9 kPa (4.4 +/- 7.1 mmHg) while the TcCO2 to PaCO2 difference was 0.36-0.38 kPa (2.8 +/- 2.9 mmHg) (P=NS). The difference between the PaCO2 and PECO2 was 0.4 kPa (3 mmHg) or less in 37 of 64 sample sets while the difference between the PaCO2 and TcCO2 was 0.4 kPa (3 mmHg) or less in 49 of 64 sample sets (P=0.038). Linear regression analysis of PECO2 vs. PaCO2 revealed a slope of 0.434, r=0.8761, r2=0.7676. Linear regression analysis of TcCO2 vs. PaCO2 revealed a slope of 0.914, r=0.9472, r2=0.8972. CONCLUSIONS: Although in most circumstances, both noninvasive monitors of PCO2 provided a clinically acceptable estimate of PaCO2, TCCO2 provided a slightly more accurate estimate of PaCO2 during intraoperative anaesthetic care in children.

Anesthesia, General↗
PubMed1997

Management of vestibular schwannomas (acoustic neuromas): the value of neurophysiology for intraoperative monitoring of auditory function in 200 cases.

OBJECTIVE: The present study investigated the significance of the presence or absence of auditory brain stem response (ABR) Waves I, III, and V as functional representatives of the cochlea, the nucleus cochlearis, and the colliculus inferior, respectively, and attempted to identify the microsurgical maneuvers that were especially likely to cause isolated or combined component losses and subsequent hearing losses. METHODS: Based on the previously described ABR classification system, 201 patients with preserved Waves I, III, and V or Waves I and V were investigated for the peak latencies and amplitudes of the waves at 15 defined microsurgical stages. Analysis was performed with respect to the presence or absence of ABR components during specific microsurgical actions and the related danger of deafness. RESULTS: Temporary or permanent losses of Waves V, I, and III occurred with 21, 27, and 29% of surgical actions, respectively, leading to deafness in 65 to 78% of the patients. Wave III disappearance was identified as the earliest and most sensitive sign. Wave V loss was usually preceded by disappearances of Waves I and III. During the most dangerous actions (drilling, pulling downward, medially, or laterally, and direct nerve manipulation), special attention ws paid to deterioration of Wave-III and then Wave I; if impairment was seen, intermittent breaks or changes in the type or site of microsurgical action were used to enable wave recovery. Acute, simultaneous, and permanent loss of all waves occurred in 27.5% of postoperatively deaf patients, whereas stepwise wave deterioration and losses occurred in 72.5%. CONCLUSION: Useful (in-time) recognition of significant waveform changes is possible and enables a change of microsurgical maneuvers to favor ABR recovery.

Audiometry, Pure-Tone↗
PubMed2004

Measurement of parathyroid hormone and application of parathyroid hormone in intraoperative monitoring.

There has been a clear progression in assays for the analysis of PTH and its clinical applications. This includes the innovative use of PTH as a point-of-care assay as an intraoperative measure of the success of parathyroid surgery. The rapid PTH assay has served as a model for the development of other rapid hormone assays, such as for adrenocorticotropic hormone,although the clinical usefulness of these other applications is less well established. Knowledge of the circulating forms of PTH continues to progress. Information about the biologic and immunologic activities of these forms will aid in the interpretation and clinical use of current assays and in the development of new assays with improved specificities. The clinical laboratory will continue to play a vital role in providing testing and support for this important mediator of mineral metabolism.

Biomarkers↗
PubMed1996

Intraoperative monitoring of the potassium-activity and pH- value on the myocardial surface during coronary bypass surgery.

INTRODUCTION: Ischemic periods very often occur a dysfunction of the heart. In this series the intraoperative changes of potassium-activity and pH- value on the heart undergoing cardioplegic induced cardiac arrest were studied. Furthermore, the sensitivity of the system in diagnostic fields of ischemic periods and reperfusion damages were investigated. METHODS: In eight patients (7 male and 1 female pts.) undergoing elective cardiosurgical procedures (aortocoronary bypass grafts) the ion activity of potassium and hydrogen ions were monitored on the heart, intraoperatively. By ion-selective electrodes the superficial cardiac ion activities were evaluated on definitive time periods on the left (LV) and right ventricle (RV). RESULTS: Preliminary results suggest: In the reperfusion-period different pH-values result on the ventricles. In the end of reperfusion the pH-values return to the starting points. Though the evaluated parameters are too alcaline in comparison to physiological intervals. The time course of epicardial potassium-concentrations is not different between the RV and LV. Initially, only low concentrations were found during perfusion and reperfusion, in the last interval of reperfusion period an increase of potassium on both ventricles were evaluated. In the end of the operations the superficial ion concentrations approximate to the values evaluated at the starting points. CONCLUSION: These results suggests, that the dynamics of ion-exchange-processes in the myocardium can be monitored with the help of ion-selective probes. This new technique opens new strategies in the qualitative check-up of myocardial protective procedures during cardioplegic cardiac arrest.

Coronary Artery Bypass↗
PubMed2004

Multimodality intraoperative monitoring during complex lumbosacral procedures: indications, techniques, and long-term follow-up review of 61 consecutive cases.

OBJECT: The purpose of this study was to examine the neurological outcomes after complex lumbosacral surgery in patients undergoing multimodality neurophysiological monitoring. METHODS: Sixty-one patients were consecutively enrolled in this study. These patients underwent complex intra- and extradural lumbosacral procedures with concomitant intraoperative electromyography (EMG) monitoring of the lower-limb muscles, external anal and urethral sphincters (EAS and EUS), and lower-limb somatosensory evoked potentials (SSEPs). Long-term (minimum 2-year) clinical follow-up data were obtained in all cases. Most patients were treated for spinal/spinal cord tumors (61%) or adult tethered cord syndrome (25%). Recordable lower-extremity SSEPs were reported in 54 patients (89%). New postoperative neurological deficits occurred in only three patients (4.9%), and remained persistent in only one patient (1.6%) at long-term follow-up examination. In only one of these cases was a significant decrease in SSEP amplitude detected. Spontaneous EMG activity was observed in the lower-extremity muscles and/or EAS and EUS in 51 cases (84%). Intraoperatively, EMG demonstrated activity only in the EUS in 5% of patients and only in the EAS in 28%. In seven patients (11%) spontaneous intraoperative EMG activity was observed in both the EAS and the EUS; however, in only three of these cases was EMG activity recorded in both sphincters simultaneously. In addition to spontaneously recorded EMG activity, electrically evoked EMG activity was also used as an intraoperative adjunct. A bipolar stimulating electrode was used to identify functional neural tissue before undertaking microsurgical dissection in 58 individuals (95%). In the majority of these patients, evoked EMG activity occurred either in one (33%) or in two muscles (9%) simultaneously. The presence of electrically evoked EMG activity in structures encountered during microdissection altered the plan of treatment in 24 cases (42%). CONCLUSIONS: The authors conclude that the combined SSEP and EMG monitoring of lower-limb muscles, EAS, and EUS is a practical and reliable method for obtaining optimal electrophysiological feedback during complex neurosurgical procedures involving the conus medullaris and cauda equina. Analysis of the results indicates that these intraoperative adjunctive modalities positively influence decision making with regard to microsurgery and reduce the risk of perioperative neurological complications. Validation of the clinical value of these approaches, however, will require further assessment in a larger prospective cohort of patients.

Adolescent↗
PubMed2002

Intraoperative monitoring of myogenic motor-evoked potentials from the external anal sphincter muscle to transcranial electrical stimulation.

STUDY DESIGN: Motor-evoked potentials from the external anal sphincter were analyzed using transcranial electrical stimulation during spinal surgery in patients under general anesthesia. OBJECTIVE: To investigate whether motor-evoked potentials from the external anal sphincter could be elicited by transcranial electrical stimulation under general anesthesia. SUMMARY OF BACKGROUND DATA: Lumbosacral surgery often places nerve rootlets at risk for injury during operative dissection. Specifically, injury for sacral rootlets can result in bowel and bladder dysfunction, but the techniques for monitoring bowel and bladder function are limited. METHODS: Thirty patients who underwent elective spinal surgery were studied. Patients were anesthetized with 50% nitrous oxide in oxygen, fentanyl, and 4 mg/kg/h of propofol (n = 19) or 1 mg/kg/h of ketamine (n = 11). The level of neuromuscular blockade, assessed by recording the M-response from the right abductor pollicis brevis muscle, was maintained at an M-response amplitude of 40-50% of control. Motor-evoked potentials in response to a multipulse transcranial electrical stimulation at stimulus sites of C3-C4 or Fz-Cz were recorded from the skin over the subcutaneous part of the external anal sphincter using a plug-type electrode probe. The success rate of motor-evoked potentials' recording and peak-to-peak amplitude and the onset latency of motor-evoked potentials were evaluated. RESULTS: Success rates of motor-evoked potentials from the external anal sphincter were 73% and 53% after transcranial stimulation at stimulus sites of C3-C4 and Cz-Fz, respectively. Amplitudes of motor-evoked potentials after C3-C4 stimulation were significantly greater than those after Cz-Fz stimulation. Motor-evoked potential latency from the external anal sphincter was 18.6 +/- 1.5 and 19.0 +/- 2.7 msec after C3-C4 and Cz-Fz stimulation, respectively. CONCLUSIONS: The results suggest that, using a transcranial multipulse stimulation, monitoring of motor-evoked potentials from the external anal sphincter is feasible during ketamine- and propofol-based anesthesia. However, further improvement of techniques would be required for intraoperative elicitation of motor-evoked potentials from the external anal sphincter.

Adolescent↗
PubMed1998

Intraoperative monitoring with stimulus-evoked electromyography during placement of iliosacral screws. An initial clinical study.

A consecutive series of twenty-seven patients who had thirty acute unstable (type-C) fractures of the pelvic ring was studied prospectively to evaluate the use of stimulus-evoked electromyography to decrease the risk of iatrogenic nerve-root injury during the insertion of iliosacral screws. A prerequisite for inclusion in the study was a normal neurological status preoperatively; somatosensory evoked potentials were monitored to further document the neurological status both before and after insertion of the screw or screws. A total of fifty-one iliosacral screws were inserted, and a current threshold of more than eight milliamperes was selected as the level that indicated that the drill-bit was a safe distance from the nerve root. Four of the fifty-one screws were redirected because of information obtained with stimulus-evoked electromyography. Postoperatively, all patients had a normal neurological status. Computerized tomography, although not accurate for detailed measurements, demonstrated that all of the screws were in a safe, intraosseous position. Monitoring with stimulus-evoked electromyography appears to provide reliable data and may decrease the risk of iatrogenic injury to the nerve roots during operations on the pelvic ring.

Adolescent↗
PubMed1993

Acoustic tumour volume and the prediction of facial nerve functional outcome from intraoperative monitoring.

The long-term facial function in 26 patients undergoing surgery to remove an acoustic neuroma has been related to the tumour volume (ml) estimated by computerized tomogram (CT) reconstruction techniques. Analysis of data allowed accurate categorization into 'small' (= < 5 ml) and 'large' (> 5 ml) tumours, which gave the maximum prognostic distinction between two groups for facial recovery. Thus, of the 14 patients with small volume tumours, 11 achieved a good (House grade I or II) facial outcome compared with 1 out of 12 patients with large tumours. Combined with the information derived from the assessment of intraoperative facial nerve electrical integrity using a combined nerve stimulator and EMG monitor, long-term facial function was predictable for all small tumours defined by volume. This represented a 15% improvement in prediction of facial recovery when defining tumour size by maximum linear dimension (small = < 2.5 cm, large > 2.5 cm). The calculations of volume obtained using a simplified ellipsoidal model compared well with CT reconstructed values (r2 = 0.85), and gave identical prediction and outcome comparisons.

Adolescent↗
PubMed2002

Intraoperative monitoring for safety of bilateral total knee replacement.

Cardiopulmonary hemodynamics in 79 consecutive patients who had one-stage bilateral total knee replacements were monitored prospectively with a pulmonary artery catheter. The pulmonary vascular resistance, wedge pressure, pulmonary artery pressure, and systemic vascular resistance were measured before skin incision, 5 to 10 minutes after implanting the first total knee replacement, and after the second knee replacement. The second knee replacement was cancelled in five patients because the pulmonary vascular resistance after the first knee replacement was more than double the baseline, or above 200 dyne/second/cm(5). No patient had clinical symptoms of fat embolism during the postoperative course. Patient predictive factors, or the use of pulse oximetry readings instead of a pulmonary artery catheter, were not predictive of intraoperative elevation of pulmonary vascular resistance. For this reason, the safety of this operation for the patient requires that intraoperative measurement of hemodynamic parameters of embolism be done.

Aged↗
PubMed2006

Significance of intraoperative monitoring of arterial blood flow velocity and hepatic venous oxygen saturation for performing minimally invasive surgery in a patient with multiple calcified pancreaticoduodenal aneurysms with celiac artery occlusion.

Even for patients with multiple pancreaticoduodenal aneurysms, successful treatment with noninvasive operative procedures can be employed, if intraoperative devices are considered. A 73-year-old man, without any symptoms, was admitted to our hospital and had computed tomography (CT) scanning to examine his liver for hepatitis C virus (HCV). Selective superior mesenteric artery (SMA) angiography confirmed multiple aneurysms in the anterior inferior pancreaticoduodenal artery (AIPDA), one aneurysm in the posterior inferior mesenteric artery (PIPDA), and another in the occluded celiac trunk, all with severe calcification. All of the aneurysms were thought to communicate with each other. With the celiac artery occlusion, the right hepatic artery (RHA) was revealed to be supplied by collateral arteries from the aneurysms in the AIPDA, and the left hepatic artery was shown to be supplied by collaterals from the left gastric artery. Intraoperative Doppler echography, at the time of the clamping of both IPDAs, demonstrated a marked decrease of blood velocity in all aneurysms (before clamping, >50 cm/s; after, <10 cm/s), although loss of pulsation and a marked decrease of flow in the RHA were inevitable. Therefore, each of these two IPDAs were ligated on the proximal side to the aneurysm, thus preserving the blood flow of the pancreas head fed by the PIPDA; bypass grafting from the AIPDA to the RHA, using the great saphenous vein, was done at the same time. After the creation of an anastomosis, the hepatic venous oxygen saturation (ShvO2) increased from 38% (at the time of ligation of the IPDAs) to 57% under ventilation. The patient's postoperative clinical course was uneventful. We describe and discuss our successful noninvasive operative management of multiple pancreaticoduodenal aneurysms, done while monitoring the blood flow and ShvO2, with some consideration of the literature.

Aged↗
PubMed2001

Recording nasal muscle F waves and electromyographic activity of the facial muscles: a comparison of two methods used for intraoperative monitoring of facial nerve function.

OBJECT: A comparison of two electrophysiological methods used to assess facial nerve function intraoperatively was conducted in 33 patients with tumors of the cerebellopontine angle. METHODS: All 33 patients had presented with normal facial nerve function preoperatively. After general anesthesia had been induced by a mixture of midazolam and fentanyl, continual online EMG recordings from the orbicularis oculi and oris muscles were alternated with nasal muscle F-wave recordings. Facial nerve outcomes, assessed using a modified House-Brackmann scale, varied among good (48%), moderate (18%), and poor (33%). Analysis of electromyographic (EMG) data resulted in a significant correlation between the finding of only transient manipulation-evoked activity and a good outcome, whereas in cases in which there was poor outcome, an increase in the amplitude or duration of ongoing activity was detected. A permanent loss of nasal muscle F waves specifically appeared to indicate a severe dysfunction of the facial nerve that was linked to a poor outcome. All patients with latency and/or amplitude changes or even a transient loss of the F wave achieved good or moderate facial nerve outcomes. A transient loss of the F wave, however, was detected significantly more frequently in patients with moderate outcomes. None of these patients exhibited normal facial function (House-Brackmann Grade I) postoperatively. CONCLUSIONS: Online EMG monitoring can provide some information on imminent or even present damage to the facial nerve intraoperatively. The diagnostic sensitivity, specificity, and positive predictive values of a permanent F-wave loss, however, are much higher than those of EMG monitoring. Additionally, this loss of the F wave is supposed to be transient if the surgical procedure is stopped until the F wave recovers. Therefore, F-wave monitoring serves to alert the surgeon that the facial nerve is about to receive a lesion.

Electromyography↗
PubMed2000

Brain tumor resection: intraoperative monitoring with high-field-strength MR imaging-initial results.

PURPOSE: To investigate the challenges and benefits of magnetic resonance (MR) imaging during brain tumor resection. MATERIALS AND METHODS: A short-bore 1.5-T MR system equipped with echo-planar-capable gradients was used in resection of brain tumors in 30 patients. MR sequences and need for contrast material enhancement were determined on the basis of the targeted lesion. MR images were acquired before, during, and after surgery. Tissue obtained at biopsy or excised as a result of intraoperative MR findings was examined histopathologically. RESULTS: MR images of enhancing lesions proved to be the most challenging to interpret intraoperatively, and relative enhancement at the resection cavity boundary was not specific for residual tumor. The ability to detect residual tumor intraoperatively resulted in a radiologically complete resection in 24 (80%) of 30 patients. The frequency of complications was low, and no untoward effects related to the MR environment were observed. CONCLUSION: Intraoperative MR imaging provided valuable information on the completeness of resection, and resection progress was well demonstrated during surgery.

Adolescent↗
PubMed2002

The use of readily available equipment in a simple method for intraoperative monitoring of recurrent laryngeal nerve function during thyroid surgery: initial experience with more than 300 cases.

HYPOTHESIS: An inexpensive and widely applicable technique to monitor recurrent laryngeal nerve (RLN) function during thyroid surgery can be safely implemented. DESIGN: Consecutive sample. SETTING: Single-surgeon academic practice. PATIENTS: Three hundred sixty-three consecutive patients undergoing surgery for thyroid disease in the 18 months from November 1, 1999, to May 31, 2001. INTERVENTIONS: Anesthetic management using laryngeal mask airway and spontaneous ventilation, combined with electrical RLN stimulation and fiberoptic video laryngoscopy to confirm vocal cord response. MAIN OUTCOME MEASURES: Vocal cord response to RLN stimulation, intraoperative anatomic findings, postoperative voice quality, and anesthetic complications. RESULTS: We used the laryngeal mask airway-based technique in 327 cases. Visualization of vocal cords was maintained throughout the surgery in 310 cases (95%). In 10 cases (3%), the branch of the RLN carrying vocal cord function could not be identified until electrical testing was performed. A single inadvertent RLN palsy was seen in 1 of the 17 cases in which vocal cord visualization was lost during the procedure (0.03% overall). Upper airway obstruction occurred in 16 (5%) of 327 attempted procedures, requiring tracheal intubation in 3 (1%). No further complications regarding airway management were seen. Pneumothorax was observed in 5 cases (2%), each of which resolved without chest tube placement. CONCLUSIONS: This technique can be applied to thyroid surgery as a safe means of managing the airway. It is associated with an ability to test RLN function at will in more than 95% of cases using readily available equipment.

Bronchoscopy↗