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PubMed1990

[Intraoperative cardiac output monitoring by the transtracheal Doppler method].

We investigated the cardiac output measured with a transtracheal doppler (TTD) tube in surgical patients and evaluated its usefulness during operations. This tube was located at the point where maximum velocity of blood flow was obtained in the ascending aorta. At this point the cross-sectional area of the ascending aorta was calculated and the cardiac output was obtained by multiplying this area with average blood flow velocity which had been ultrasonically determined. The cardiac output by the TTD method was compared with that of the thermodilution method in 10 patients. The results with both groups showed a direct linear correlation. We obtained the following linear equation: TTD C.O. = 0.61 Thermo C.O. + 1.3 C.O.: cardiac output. The direct correlation coefficient proved to be 0.85 at a risk factor of 0.01. The result suggests that this non-invasive TTD method is easily available and useful in monitoring the intraoperative cardiac output.

Aged↗
PubMed1992

Pure motor hemiparesis with stable somatosensory evoked potential monitoring during aneurysm surgery: case report.

We report a patient who sought treatment for an acute subarachnoid hemorrhage as a result of an intracranial aneurysm. Management included early surgical repair and intraoperative monitoring of evoked potentials. Pan-angiography revealed berry aneurysms of the communicating anterior artery and right middle cerebral artery. Surgery was uneventful, and the somatosensory evoked potential monitoring did not show any abnormalities. Nevertheless, the patient showed a neurological deficit due to a clip-related infarct in the right middle cerebral artery territory characterized by a right hemiparesis with no sensory deficit. This case report supports the possibility of false-negative results in single-mode intraoperative monitoring during aneurysm surgery.

Adult↗
PubMed1997

Intraoperative spinal cord monitoring for intramedullary surgery: an essential adjunct.

Intraoperative monitoring of the functional integrity of the spinal cord during removal of intramedullary spinal cord lesions is an aid in intraoperative decision making and a primary tool for the prediction of neurological outcome. Motor evoked potential monitoring has become the neurophysiological monitoring technique of choice for that purpose. In the senior author's experience with over 130 pediatric patients suffering from intramedullary spinal cord tumors, the neurophysiological data of both motor and sensory evoked potentials was utilized in an integrative fashion. Motor evoked potentials, elicited with single transcranial electrical stimuli and recorded directly from the spinal cord with an electrode in the spinal epidural space, reflect the functional integrity of the corticospinal tract. Motor evoked potentials, elicited with a short train of transcranial electrical stimuli and recorded from limb muscles, reflect the functional integrity of the motor system from the cerebral cortex/white matter to beyond the neuromuscular junction. Both epidural and muscle motor evoked potentials correlated closely with postoperative neurological function. Both techniques provide fast, practical and reliable information on the functional integrity of the motor tracts of the spinal cord. No complications attributable to stimulation or recording occurred. Over time both the technique's reliable power of predicting clinical outcome and its practical versatility have altered the surgical approach in that gross total resections are more readily attempted as long as motor evoked potential data indicate the intact functional integrity of the corticospinal tract. This monitoring technique unquestionably had a favorable impact on neurological outcome.

Adolescent↗
PubMed2000

Acoustic neuroma surgery as an interdisciplinary approach: a neurosurgical series of 508 patients.

OBJECTIVES: To evaluate an interdisciplinary concept (neurosurgery/ear, nose, and throat (ENT)) of treating acoustic neuromas with extrameatal extension via the retromastoidal approach. To analyse whether monitoring both facial nerve EMG and BAEP improved the functional outcome in acoustic neuroma surgery. METHODS: In a series of 508 patients consecutively operated on over a period of 7 years, functional outcome of the facial nerve was evaluated according to the House/Brackmann scale and hearing preservation was classified using the Gardner/Robertson system. RESULTS: Facial monitoring (396 of 508 operations) and continuous BAEP recording (229 of 399 cases with preserved hearing preoperatively) were performed routinely. With intraoperative monitoring, the rate of excellent/good facial nerve function (House/Brackmann I-II) was 88.7%. Good functional hearing (Gardner/Robertson 1-3) was preserved in 39.8%. CONCLUSION: Acoustic neuroma surgery via a retrosigmoidal approach is a safe and effective treatment for tumours with extrameatal extension. Functional results can be substantially improved by intraoperative monitoring. The interdisciplinary concept of surgery performed by ENT and neurosurgeons was particularly convincing as each pathoanatomical phase of the operation is performed by a surgeon best acquainted with the regional specialties.

Adolescent↗
PubMed1998

Monitoring for intraoperative awareness.

Despite advances in anesthetic technique and technology, intraoperative awareness continues to occur with alarming regularity. The psychological effects on patients and the medicolegal consequences to providers have created the need for a reliable monitor of the hypnotic component of anesthesia. A new technology known as bispectral analysis (BIS) has the potential to put an end to the devastating occurrence of intraoperative awareness, as well as improve the overall effectiveness of anesthetic delivery and the surgical experience. Applicable to almost any situation requiring sedation or general anesthesia, BIS's reliability is a real-time measure of hypnosis levels.

Anesthesia↗
PubMed2005

Brainstem auditory evoked potential monitoring: when is change in wave V significant?

BACKGROUND: The probability of hearing loss during cerebellopontine angle (CPA) surgery can be reduced by using brainstem auditory evoked potential (BAEP) intraoperative monitoring (IOM). A wave V latency prolongation of 1.0 milliseconds or amplitude decrement of greater than 50% is arbitrarily considered the point when damage to hearing occurs. OBJECTIVE: To determine the accuracy of wave V changes in predicting hearing impairment. METHODS: Patients undergoing BAEP IOM for surgery in the CPA region were evaluated. The greatest wave V latency and amplitude change was determined. Patients were divided into four groups depending on degree of change of wave V: Group 1 consisted of minimal change, whereas Group 4 was permanent loss of wave V. The frequency of hearing loss in each group was compared. RESULTS: Data from 156 patients were reviewed. When all patients were analyzed, the frequency of hearing loss was not significantly different between the groups. When patients with CPA tumor were excluded, a significantly higher number of patients in Group 4 had hearing loss. Analysis of the patients with CPA tumor showed no difference in the frequency of hearing loss in any of the groups; even a large number (50%) of Group 1 patients had hearing impairment. CONCLUSIONS: During brainstem auditory evoked potential intraoperative monitoring, the type of surgery is important when interpreting significance of changes of wave V. For non-cerebellopontine angle tumor surgery, hearing loss occurs usually only with permanent loss of wave V; much smaller changes may be important in cerebellopontine angle tumor surgery.

Acoustic Stimulation↗
PubMed1991

Usefulness of epidurally evoked cortical potential monitoring during cervicomedullary glioma surgery.

This report describes a patient with an intramedullary ependymoma at the region of the cervicomedullary junction in whom there was an abolition of somatosensory evoked potentials following median nerve stimulation. During intraoperative monitoring of cortical potentials elicited by epidural cervical cord stimulation, the tumor was removed. Posterior epidural stimulation appeared to depolarize more ascending fibers than did stimulation of a single peripheral nerve. We recommend that, in cases of operations in this vital area, epidurally evoked cortical potentials be monitored intraoperatively.

Evoked Potentials, Somatosensory↗
PubMed1988

Routine intraoperative facial nerve monitoring during otologic surgery.

We have used intraoperative monitoring and stimulation of facial nerve function routinely in 301 consecutive otologic and neurotologic cases. The device has been safe, simple to use, and practical. Facial contraction is detected by a strain-gauge sensor in the corner of the mouth and is signalled audibly to the surgeon. Electrical stimulation of the facial nerve can be delivered through a sterile probe, which produces a constant-current-square-wave impulse. The device has several advantages: it signals unintentional mechanical stimulation of the facial nerve during surgery; it allows mapping of the nerve through soft tissue, tumor, and bone; it predicts dehiscences in the bony covering of the nerve; and it allows confirmation of the electrical integrity of the nerve before and after surgery. In this paper we present a technical description of the device, relevant intraoperative electrical measurements, and illustrative case examples. Although the device does not replace anatomic knowledge and surgical ability, it provides a margin of security during ear surgery. This system for intraoperative facial monitoring is practical, and the authors encourage its routine use.

Adolescent↗
PubMed1999

Are obstetrical personnel required for intraoperative fetal monitoring during nonobstetric surgery?

OBJECTIVE: To determine if the scientific literature supports the practice of electronic monitoring of the fetal heart rate (FHR) during nonobstetric surgery. STUDY DESIGN: A search of the literature from 1966 to 1995 was performed using MEDLINE. RESULTS: No fetal hypoxic mortality or morbidity has been documented from nonobstetric surgery without occurrence of a maternal hypoxic complication regardless of the use of FHR monitoring or whether alterations of the FHR occurred. CONCLUSIONS: Fetal monitoring is an indirect assessment of maternal anesthetic and surgical management that is not as specific or effective as direct assessment of the maternal parameters to detect respiratory compromise. Current clinical evidence obtained does not substantiate the need for obstetric personnel to monitor FHR changes during surgical procedures because no change in fetal outcome has been documented.

Female↗
PubMed1986

Role of preoperative hemodynamic monitoring in intraoperative fluid management.

In this study the hemodynamic factors which contribute to postoperative mortality and morbidity were evaluated in 41 patients. Preoperative data were prospectively collected over a 5-year period. The patients underwent vascular and general surgical operative procedures. Among them, 23 patients had minor or no postoperative complications (group 1) and 18 patients suffered serious complications or died (group 2). Preoperative cardiac function was better in group 1, but both groups achieved their best cardiac index (CI) with fluids or pharmacologic manipulation preoperatively. Group 2 patients had longer operations, more blood loss, and were significantly hypovolemic postoperatively as indicated by lower pulmonary arterial wedge pressure (PAWP) and CI in comparison to the best preoperative values. When postoperative PAWP was higher than or within 3 mm Hg of the best preoperative level, complication rate was 14 per cent (3 of 21). In 15 of the 19 or 79 per cent of the patients, postoperative complications developed when PAWP decreased by 4 mm Hg or more. The difference in complications was significant (P less than 0.01). However, commonly measured parameters such as the amount of fluid infused, urine output, immediate postoperative heart rate, blood pressure, central venous pressure, and hemoglobin failed to reveal hemodynamically significant hypovolemia or lacticacidemia in group 2. The authors were unable to demonstrate a reduction in mortality or morbidity in group 2 patients in whom serious technical operative difficulties were also encountered.

Aged↗
PubMed1995

Use of sensory-evoked potentials recorded from the human occiput for intraoperative physiologic monitoring of the spinal cord.

STUDY DESIGN: This is a report of a prospective case series. OBJECTIVE: The purpose of this study was to determine whether evoked potential activity recorded from occipital scalp electrodes in humans is similar to that recorded in animals, and to evaluate the independence of this activity from the classical somatosensory-evoked potential. SUMMARY OF BACKGROUND DATA: Intraoperative somatosensory-evoked potentials can be of limited usefulness in predicting spinal cord injury because they are transmitted primarily through the dorsal columns, and therefore do not reflect integrity of important ventral pathways. It recently has been shown in animal studies that a sensory-evoked potential recorded from the cerebellum is mediated via ventral tracts and is useful as an adjunct to the somatosensory-evoked potential in spinal cord monitoring. METHODS: Twenty-five patients undergoing spinal or posterior fossa surgery were consecutively entered into the study. Evoked responses were recorded transcranially from over the cerebellar hemispheres and from the vertex. Recordings were made directly from the surface of the cerebellar hemispheres in seven of these patients. RESULTS: Waveforms could be recorded and reproduced in all but one of the patients. The overall appearance of the occipital recordings was similar to the appearance of responses obtained in animals. The mean latency of the first negative peak recorded from the ipsilateral occiput was 33.0 msec (standard deviation, 3.7 msec) compared with 52.4 msec (standard deviation, 6.1 msec) for the somatosensory-evoked potential. In addition, the amplitude of this response (0.35 microV; standard deviation, 0.20 microV) was independent of the amplitude of the somatosensory-evoked potential (0.76 microV; standard deviation, 0.69 microV). In five cases, one evoked potential could be recorded in the absence of the other. Recordings from the surface of the cerebellum were of the same morphology, but of greater amplitude than the transcranial recordings. CONCLUSION: Evoked responses can be reliably recorded from over the occiput and show characteristics independent of the classical somatosensory-evoked potential. These responses are very similar to the cerebellar-evoked potential recently characterized in animals and may provide a method for assessing the physiologic integrity of the ventral tracts of the spinal cord in humans.

Animals↗
PubMed2003

Intraoperative urodynamics in spinal cord surgery: a study of feasibility.

Intraoperative monitoring (IOM) of bladder function in spinal cord surgery is a challenging task due to vegetative influences, multilevel innervation and numerous supraspinal modulating factors. Despite routine use of urodynamics in neurosurgery for implantation of bladder stimulators or denervation of nerve fibres in spastic reflex bladders, application of IOM in patients with spinal cord tumours or tethered-cord syndrome is not widespread. Combining urodynamics with sphincter electromyography (EMG) in IOM enables identification of bladder efferents responsible for contraction and continence. We monitored four patients with ependymoma of the Cauda equina, one patient with tethered-cord syndrome and two patients with cervical intramedullary tumours. In all patients undergoing operations of the Cauda equina, identification of bladder efferents responsible for detrusor contraction was possible. There was good correlation between preoperative bladder dysfunction, preoperative urodynamics and intraoperative pressure increase by bladder contraction or latency between stimulation and contraction. This method proved unsuitable for intramedullary tumours where no contraction of the bladder could be observed while stimulating the spinal cord. Intraoperative monitoring of urodynamics is an effective tool for identifying bladder efferents in the Cauda equina. Intraoperative conclusions on bladder dysfunction through registration of pressure increase and latency are possible.

Adult↗
PubMed1994

[Neuromonitoring in carotid surgery: possibilities and limits of transcranial Doppler ultrasound].

In order to evaluate the suitability of transcranial Doppler sonography as an intraoperative monitor in carotid surgery, we compared measurements of mean blood flow velocity in the ipsilateral middle cerebral artery with the cortical response of somatosensory evoked potentials in a prospective study of 176 carotid operations. SEP recording was readily feasible during all procedures and by means of SEP loss all patients at risk for critical cross-clamp related cerebral ischemia were reliably identified. In contrast, TCD could not be used for assessment of cerebral hemodynamics in more than 40% of patients. What is more, in high risk patients with intraoperative loss of SEP, TCD could not be performed in 74% of cases. This high rate of failure limits the usefulness of TCD as an intraoperative monitor and detracts from the additional benefit of identifying cerebral embolism and hyperperfusion as potential causes of neurological deficits. In contrast to SEP recording, TCD cannot be recommended as a routine monitor in carotid surgery.

Aged↗
PubMed1989

Neurophysiologic monitoring in posterior fossa surgery. I. Technical principles, applicability and limitations.

In 135 cases of posterior fossa surgery almost exclusively in the cerebellopontine angle (CPA) intraoperative monitoring of brain-stem acoustic evoked potentials (BAEP) and partly somatosensory evoked potentials (SEP) was performed. The series consisted of 20 microvascular decompressions, 63 acoustic neurinomas, 7 vascular lesions and 45 other space occupying lesions, mostly in the CPA. BAEP monitoring alone was employed in 76 cases, combined BAEP and SEP monitoring less frequently. The technique of anaesthesia and intraoperative monitoring is presented in detail including an analysis of technical problems (17 in 135 = 13% of cases) and technical failures (11 of 135 = 8%). The results of monitoring brainstem pathways contralateral to the lesion are detailed. It is concluded that the technical principles of evoked potential monitoring in posterior fossa surgery are well established. The applications and limits of this technique including its modifications are described.

Cranial Fossa, Posterior↗
PubMedDate not supplied

Intraoperative SSEP monitoring during external fixation procedures in the lower extremities.

The efficacy of somatosensory evoked potentials (SSEPs) to detect acute peripheral nerve injury during external-fixator application in the lower extremities was evaluated in 40 children with 42 Ilizarov surgical procedures. The study included patients who were either clinically normal or who had preexisting neuropathy but consistent and reliable SSEP responses preoperatively. SSEPs were recorded from the popliteal fossa and lumbar regions after alternating stimulation of the peroneal and posterior tibial nerves at the ankle. SSEP changes due to anesthesia, Ilizarov apparatus application, and other intraoperative variables are described. Significant deterioration or total loss of SSEP response during surgery occurred in four cases. Two of these patients were normal preoperatively and had symptoms of neurologic deficit postoperatively; the other two had exacerbations of pre-existing neuropathy. In general, the peroneal nerve was at greater risk for injury during surgery. SSEP monitoring proved to be technically feasible in external-fixation procedures on the lower extremities and may be a practical tool for detection of intraoperative nerve compromise.

Acute Disease↗