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At least 127 records · Page 7Linked to original sources
PubMed1997

[Intraoperative monitoring for functional neurosurgery during intravenous anesthesia with propofol].

We studied the effects of propofol on electrophysiologic monitoring for functional neurosurgery. In six patients with intractable epilepsy, electrocorticograms (ECoGs) were monitored for epilepsy surgery, and in two of them, somatosensory evoked potentials (SEPs) were monitored because of the focus adjacent to the central sulcus. In four patients with hemifacial spasm, brain stem auditory evoked potentials (BAEPs) and abnormal muscle responses (AMRs) were monitored during microvascular decompression (MVD). In two patients with Parkinson's disease and in one patient with post-traumatic tremor, neural noise levels were recorded from microelectrodes during posteroventral pallidotomy and Vim thalamotomy. In each case of epilepsy surgery, during intravenous anesthesia with propofol, spike activity was recordable enough to identify the resective area and the residual spikes. SEP phase reversal was obtained in two patients and an exact determination of the central sulcus was possible. BAEPs and AMRs were obtained in all MVDs. To record neural noise levels, the infusion of propofol was decreased in two cases of posteroventral pallidotomy, and it was stopped in one case of Vim thalamotomy. In these patients, neural noise levels were recorded and were useful for identifying the target. Propofol is a potentially useful anesthetic agent for electrophysiologic monitoring during functional neurosurgery.

Adult↗
PubMed1996

[Intraoperative monitoring of gastric intramucosal pH].

BACKGROUND: Gastric mucosal pH may be a good indicator of splanchnic tissue oxygenation. AIM: To study the effects of abdominal surgical procedures on gastric mucosal pH. PATIENTS AND METHODS: Eighteen patients subjected to abdominal surgery were studied. All patients received general anesthesia and hemodynamic parameters were maintained within 20% of basal values. A tonometer was placed in the stomach after induction of anesthesia. Arterial blood gases and samples from the tonometer were obtained 30 minutes after induction and at 2 hours of surgery. Intramucosal pH was calculated using Henderson-Haselbach equations. RESULTS: Basal gastric mucosal pH was 7.4 +/- 0.1 and did not change during surgery. Two patients had a pH persistently below 7.35 without hemodynamic alterations or systemic acidosis. CONCLUSIONS: Gastric mucosal pH is not modified by abdominal surgery and some patients have low values despite the absence of hemodynamic derangement.

Abdomen↗
PubMed1997

Intraoperative monitoring of spinal cord function using motor evoked potentials via transcutaneous epidural electrode during anterior cervical spinal surgery.

Because false-positive results are not infrequent when monitoring somatosensory evoked potentials during surgery, monitoring of motor evoked potentials (MEPs) has been proposed and successfully used during the removal of spinal cord tumors. However, this often requires direct visual placement of an epidural electrode after a laminectomy. We evaluated the use of MEPs, recorded via a transcutaneously placed epidural electrode, to monitor motor pathway functional integrity during surgery on the anterior cervical spine. Sixteen patients underwent anterior cervical vertebral decompression and fusion for cervical myelopathy and/or radiculopathy. Before surgery, an epidural monitoring electrode was placed transcutaneously at the midthoracic level and was used to record MEPs after transcranial cortical electrical stimulation. Electrode placement was successful in all patients but one, and satisfactory baseline spinal MEPs were obtained except for one patient who had cerebral palsy with significant motor dysfunction. Patients showed no significant changes in spinal MEPs during surgery, and all had baseline or better motor function postoperatively. None had complications from epidural electrode placement or electrical stimulation. We conclude that motor pathways can be monitored safely during anterior cervical spinal surgery using spinal MEPs recorded via a transcutaneously placed epidural electrode, that MEP preservation during surgery correlates with good postoperative motor function, and that cerebral palsy patients may possess too few functional motor fibers to allow MEP recording.

Adolescent↗
PubMed1997

Intraoperative monitoring.

This article discusses some of the routine as well as more specialized monitoring devices available. In thoracic surgery monitoring may be even more challenging because the surgery itself may involve manipulation of the airways, the pulmonary as well as cardiovascular systems. The anesthesiologist must have a full understanding of the required monitoring devices and decide which if any special techniques are needed depending on the surgical procedure and the patient's preoperative condition.

Anesthesia↗
PubMedDate not supplied

Impact of continuous intraoperative monitoring on outcomes in open fetal surgery.

OBJECTIVES: There are shifts in fetal hemodynamics during open fetal surgery that were not appreciated until the use of intraoperative fetal echocardiography. We have developed an intraoperative monitoring strategy to continuously assess fetal hemodynamics. We hypothesized that this approach would enhance intraoperative management and survival. METHODS: Medical records of open fetal surgery patients were reviewed since the implementation of this approach. Intraoperative fetal monitoring was accomplished by continuous echocardiography, pulse oximetry, establishment of intravenous access, and arterial blood gas and hemoglobin measurement. Overall survival was compared to fetal surgeries performed prior implementation of this monitoring strategy. RESULTS: Resections of a congenital cystic adenomatoid malformation or a sacrococcygeal teratoma in nine hydropic fetuses were performed while using this monitoring strategy. Intraoperative echocardiography resulted in a change of management in 7 of 9 fetuses. The main observations on fetal echocardiography resulting in intraoperative intervention were decreased ventricular filling, bradycardia, and decreased ventricular contractility. Therapy included administration of volume expanders and/or inotropic agents. Overall fetal survival was 78% compared to a survival of 42% prior to the implementation of this approach. CONCLUSION: Continuous intraoperative fetal monitoring provides real time assessment of fetal hemodynamics which results in changes in intraoperative management. The overall outcomes in these critically ill fetuses have been improved.

Echocardiography↗
PubMed1999

Intraoperative monitoring during surgery for acoustic neuroma: benefits of an extratympanic intrameatal electrode.

OBJECTIVES: To assess the utility of an extratympanic intrameatal electrode for intraoperative monitoring during acoustic neuroma and other cerebellopontine angle tumour surgery and to define the neurophysiological and surgical factors which influence hearing preservation. METHODS: Twenty two patients, 18 with acoustic neuromas and four with other cerebellopontine angle tumours, underwent intraoperative monitoring during tumour excision. The extratympanic intrameatal electrode (IME) was used to record the electrocochleogram (ECoG) and surface electrodes to record the brainstem auditory evoked response (ABR). RESULTS: The compound action potential (CAP) of the ECoG was two and a half times greater in amplitude than wave I of the ABR and was easily monitored. Virtually instant information was available as minimal averaging was required. Continuous monitoring was possible from the commencement of anaesthesia to skin closure. The IME was easy to place, non-invasive, and did not interfere with the operative field. Operative procedures which affected CAP or wave V latency or amplitude were drilling around the internal auditory meatus, tumour dissection, nerve section, and brainstem and cerebellar retraction. Hearing was achieved in 59% of patients. CONCLUSIONS: The IME had significant benefits in comparison with other methods of monitoring. The technique provided information beneficial to preservation of hearing.

Action Potentials↗
PubMed1992

Intraoperative monitoring of an unusual brachial plexus tumor.

This case illustrates the importance of intraoperative monitoring of neuronal function to help separate tumor tissue from neural tissue in a 54-year-old patient with left shoulder pain resulting from a desmoid tumor. Preoperative nerve conduction and electromyographic studies showed a lesion in the lateral cord of the brachial plexus, which was found to be intimately involved with the tumor mass and was splayed into a very thin effaced sheet of neural tissue. Stimulation of the tumor/nerve tissue mass proximal to the lesion was impossible due to the invasion of the brachial plexus by the tumor. The technique that was adapted for this unusual presentation was to stimulate the tumor/nerve tissue mass itself and record compound muscle action potentials distally. With the technique described, a subtotal resection of an aggressive fibromatosis enmeshed in the proximal brachial plexus was possible, and excellent relief of pain symptoms and retention of functional capabilities of the involved extremity were achieved.

Action Potentials↗
PubMed2000

Low dose propofol as a supplement to ketamine-based anesthesia during intraoperative monitoring of motor-evoked potentials.

STUDY DESIGN: Motor-evoked potentials (MEPs) were analyzed using transcranial electrical stimulation during spinal surgery in patients under ketamine-based anesthesia, with and without propofol. OBJECTIVE: To investigate the effects of propofol on MEPs and ketamine-induced adverse effects during spinal surgery in patients under ketamine-based anesthesia. SUMMARY OF BACKGROUND DATA: Intraoperative monitoring of transcranial motor-evoked responses provides a method for monitoring the functional integrity of descending motor pathways. However, because these responses are sensitive to suppression by most anesthetic agents, anesthetic technique is limited during the monitoring of MEPs. Ketamine has been reported to have little effect on MEPs but may produce adverse effects such as psychedelic effect and hypertension. Recently, it has been reported that propofol may be able to inhibit ketamine-induced adverse effects. METHODS: Intraoperative monitoring of MEPs was performed in 58 patients who underwent elective spinal surgery. Anesthesia was maintained with nitrous oxide-fentanyl-ketamine without or with low-dose (1-3 mg/kg/hr) of propofol (K group; n = 34, KP group; n = 24, respectively). Transcranial stimulation with single or paired pulses or a train of three or five pulses (interstimulus interval, 2 msec) were delivered to the scalp, and compound muscle action potentials were recorded from the left and right tibialis anterior muscles. To investigate the dose effects of propofol on MEPs, propofol was administered at an infusion rate of 6, 4, and 2 mg/kg/hr and then discontinued in 14 patients. RESULTS: Results of MEPs were comparable between the K and KP groups. The incidence of postoperative psychedelic effect was significantly less in the KP group (14%) than in the K group (41%). Although propofol inhibited MEPs dose dependently, the use of a train of pulses for stimulation could overcome such inhibition. CONCLUSIONS: If a train of pulses were used for transcranial stimulation, low-dose propofol can be effectivelyused as a supplement to ketamine-based anesthesia during intraoperative monitoring of myogenic MEPs. Addition of propofol significantly reduced the ketamine-induced psychedelic effects.

Adolescent↗
PubMedDate not supplied

[Intraoperative monitoring of the spinal cord. Personal results and an inventory of the current status].

The concept of intraoperative monitoring as continuous surveillance of sensory pathways by intraoperative sensory evoked potentials is described. The need for intraoperative monitoring is derived from the morbidity of certain spinal operations. First experiences from 25 own cases are outlined and the advantages of different methods discussed. The current status of spinal cord monitoring is briefly reviewed.

Afferent Pathways↗
PubMed2004

Observations on intraoperative monitoring of visual pathways using steady-state visual evoked potentials.

BACKGROUND AND OBJECTIVE: Former studies revealed conflicting information on the usefulness of intraoperative monitoring of visual evoked potentials. This study was designed to evaluate the characteristics of visual evoked potential recording in surgically anaesthetized patients using the modality of steady-state visual evoked potentials. METHODS: In 30 cases with non-cranial surgery steady-state visual evoked potentials were recorded in the awake and surgically anaesthetized patient using total intravenous anaesthesia. For stimulation, goggles with red light-emitting diodes at a frequency of 8.5 Hz were used. A two-channel recording with silver cup electrodes at Oz to Fz and Oz to earlobe was used. All traces were analysed for the presence of the characteristically sinusoidal waveform and amplitudes and latencies of the main peaks were measured. RESULTS: Recordings during surgery demonstrated a minor latency prolongation of 16% and a more pronounced amplitude attenuation of 67% compared to the recordings in the awake patients. These differences were statistically significant (paired t-test, P < 0.001). In surgically anaesthetized patients steady-state visual evoked potentials showed a relatively high intra- and interindividual variability. In four of 30 patients completely stable recordings were obtained, whereas in 14 patients identifiable waves were recordable in only less than 50% of the intraoperative traces. Of the total 1360 traces recorded intraoperatively clearly identifiable steady-state visual evoked potentials patterns were present in 56% of the traces. There was no correlation between the magnitude of the evoked potential amplitude and its stability in intraoperative recordings. CONCLUSIONS: We conclude from this study, that steady-state visual evoked potential recordings in the surgically anaesthetized patient appeared to be more stable compared to our earlier findings using transient visual evoked potentials. However, further efforts are necessary to improve the stability of the recordings during surgery and thus allow for a more reliable intraoperative monitoring of visual pathways in routine clinical practice.

Adult↗