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PubMed1991

Intraoperative monitoring of somatosensory evoked potentials in patients with cerebral aneurysm--correlation between central conduction time and postoperative neurological status.

Somatosensory evoked potentials (SEPs) were monitored during 55 aneurysm procedures in 49 patients to investigate the relationship between central conduction time (CCT) and neurological status in the immediate postoperative period. Significant CCT prolongation was observed in 15 cases. The postoperative neurological status deteriorated in nine of the 15 cases, compared with three of 40 cases without appreciable CCT changes. This difference was significant at p less than 0.05. The CCT prolongation was ascribable to temporary vascular occlusion in half of the cases. Intraoperative SEP monitoring is useful in predicting neurological morbidities in the immediate postoperative period in patients with cerebral aneurysm.

Adult↗
PubMed2003

Palmar hyperhidrosis: intraoperative monitoring with laser Doppler blood flow as a guide for success after endoscopic thoracic sympathectomy.

OBJECTIVE: Video-assisted endoscopic thoracic sympathectomy is an effective surgical procedure for treating patients with palmar hyperhidrosis. An increase by more than 1 degrees C in palmar temperature has been observed to be predictive of good outcome. In this study, we investigated the use of palmar laser Doppler flowmetry as an intraoperative assessment of the efficacy of the operation. METHODS: One hundred sixty-six patients underwent a total of 330 endoscopic thoracic sympathectomy procedures from March 1996 to June 2001. We studied 17 patients (15 men, 2 women) who underwent a total of 33 procedures. The patients' mean age was 27.07 +/- 7.92 years, and the mean hospital stay was 2.23 +/- 0.66 days. RESULTS: Mean baseline laser Doppler blood flow was 2.63 +/- 2.56 ml/min/100 g. After the procedure, mean blood flow increased significantly to 7.24 +/- 5.88 ml/min/100 g (r = 0.768, P < 0.000, 95% confidence limit, -6.1060, -3.0946), a 232.18 +/- 219.12% increase. Mean palmar temperature increased to 1.44 +/- 1.44 degrees C. All patients experienced relief after the operation. Compensatory hyperhidrosis occurred in 10 (58.8%) of 17 patients. CONCLUSION: Monitoring of palmar laser Doppler blood flow changes is a useful adjunct during endoscopic thoracic sympathectomy surgery, and, when coupled with the established methods of endoscopic visualization and palmar temperature, it can predict the success of the procedure accurately.

Adolescent↗
PubMed1988

Intraoperative monitoring of auditory and brain-stem function.

Extensive clinical experience has demonstrated that intraoperative brain stem auditory evoked potentials (BAEPs) are a reliable method of monitoring auditory and brain stem function during posterior fossa surgery. An intraoperative BAEP change identifies possible neurophysiologic compromise and allows adjustment of the surgical approach in an attempt to avoid permanent neurologic injury. The use of BAEPs intraoperatively has been associated with a significant decline in postoperative auditory morbidity. Supplementation of this technique with direct eighth nerve recordings and/or upper extremity somatosensory evoked potentials offers further improvement in identifying possible surgical threat to auditory or brain stem function.

Brain Diseases↗
PubMed2004

The refractory period of fast conducting corticospinal tract axons in man and its implications for intraoperative monitoring of motor evoked potentials.

OBJECTIVE: To determine the absolute and relative refractory period (RRP) of fast conducting axons of the corticospinal tract in response to paired high intensity (HI or supramaximal) and moderate intensity (MI or submaximal) electrical stimuli. The importance of the refractory period of fast conducting corticospinal tract axons has to be considered if repetitive transcranial electrical stimulation (TES) is to be effective for eliciting motor evoked potentials (MEPs) intraoperatively. METHODS: Direct (D) waves were recorded from the epidural space of the spinal cord in 14 patients, undergoing surgical correction of spinal deformities. To assess the absolute and RRPs of the corticospinal tract, paired transcranial electrical stimuli at interstimulus intervals (ISI) from 0.7 to 4.1 ms were applied. Recovery of conditioned D wave at short (2 ms) and long (4 ms) ISI was correlated with muscle MEP threshold. The refractory period for peripheral nerve was tested in comparison to that for the corticospinal tract. In four healthy subjects sensory nerve action potentials of the median nerve were studied after stimulation with paired stimuli. RESULTS: HI TES revealed a mean duration of 0.82 ms for the absolute refractory period of the corticospinal tract, while MI stimulation resulted in a mean refractory period duration of 1.47 ms. Stimuli of HI produced faster recovery of D wave amplitude during the RRP. Furthermore, short trains of transcranial electrical stimuli did not elicit MEPs when D wave showed incomplete recovery. A similar influence of stimulus intensity on recovery time was found for the refractory period of peripheral nerve. CONCLUSIONS: The recovery of D wave amplitude is dependent upon stimulus intensity. High intensity produces fast recovery. This is an important factor for the generation of MEPs. When HI TES is used to elicit MEPs, short and long ISIs are equally effective. When MI TES is used to elicit MEPs, only a long ISI of 4 ms is effective.

Action Potentials↗
PubMed2003

Monitoring intraoperative effectiveness of caudal analgesia through skin temperature variation.

BACKGROUND/PURPOSE: A reliable noninvasive intraoperative marker of caudal analgesia effectiveness remains elusive. Caudal analgesia causes sympathetic inhibition resulting in vasodilatation, increased blood flow, and a resultant increase in temperature in the affected dermatomes. The authors hypothesize that this change in temperature between the affected and unaffected dermatomes is measurable and may represent a noninvasive method of monitoring effectiveness of caudal analgesia. METHODS: Children undergoing lower abdominal surgery participated in the caudal or noncaudal (control) analgesia arm of the study. After induction of general anesthesia, 0.25% bupivicaine (1 mL/kg) was infiltrated for a field block in control patients or a caudal block in the experimental group. Temperature was measured at the C4 and L2 dermatomes starting after induction and 5 minutes before the caudal or field block and every 5 minutes after. T(o) is defined as the difference between the C4 and L2. Delta T (DeltaT) is the temperature variation between T(o). A change in the DeltaT is defined by an increase in the L2 temperature. RESULTS: Forty-six families enrolled (36 experimental, 10 control). The DeltaT for controls was 0.2+/-0.09 degrees C (SEM). Each child in the experimental group had 2 temperature measurements before the caudal with an average DeltaT of 0.3+/-0.07 degrees C (SEM), thus, were internal controls. A marked increase in DeltaT at 5 minutes 0.5+/-0.06 degrees C (SEM) and at 10 minutes 0.6+/-0.07 degrees C (SEM; P <.05) was noted in the experimental group. CONCLUSION: A significant transient change in temperature is observed after caudal analgesia and maybe a noninvasive marker of effectiveness. Further study may clarify its clinical utility.

Abdomen↗
PubMed1994

Intraoperative monitoring of parathyroid procedures by a 15-minute parathyroid hormone immunochemiluminometric assay.

OBJECTIVE: To report the recent development and validation of a sensitive 15-minute immunochemiluminometric assay (ICMA) of parathyroid hormone (PTH). DESIGN: The characteristics and applications of a new "rapid" PTH ICMA are described, and the advantages in comparison with other assays are discussed. MATERIAL AND METHODS: The 15-minute PTH ICMA was achieved by using a higher incubation temperature (45 degrees C rather than room temperature) and a concentration of tracer antibodies that was 5 times that in the regular 18-hour assay. The sensitivity, recovery, and linearity of dilution of the rapid ICMA were assessed, as was its ability to reflect intraoperative changes in PTH concentration after parathyroidectomy in patients with hyperparathyroidism. RESULTS: The sensitivity of the ICMA was 0.3 pmol/L in comparison with 0.08 pmol/L for the regular 18-hour assay (normal range, 1.0 to 5.0). The recovery of added PTH was 84% by using ethylene-diaminetetraacetic acid-plasma as the specimen. Moreover, the linearity of specimens after dilution was good. The assay demonstrated a rapid response to parathyroid gland removal. In most patients, PTH levels declined precipitously (to less than 30% of basal values) within 5 minutes after parathyroid resection. PTH levels remained low to undetectable at 10 and 20 minutes after excision. CONCLUSION: This rapid PTH ICMA may be of assistance to endocrine surgeons in the monitoring of PTH function after both parathyroid and thyroid surgical procedures.

Humans↗
PubMed1985

[Detection of venous embolism during intraoperative monitoring by two-dimensional transesophageal echocardiography].

12 patients (mean age: 81 +/- 9 years) undergoing total hip replacement because of transcervical femoral fractures were studied intraoperatively by two-dimensional transoesophageal echocardiography (TEE). The purpose of this study was to evaluate the ability of this new technique for detection of embolic events in the right heart by intraoperative 2D-TEE monitoring during hip surgery. In all patients (pts) we observed a transient increase of contrast intensity in the right atrium immediately after insertion of the acetabulum prosthesis ("snow flurry"). Contrast was maximal 15-20 seconds after insertion and persisted for approximately 2 min. While contrast intensity decreased in the minutes thereafter, in 3 pts contrast became more heterogeneous:we detected structures like "flakes" passing the right heart, sometimes circulating for some seconds in the right atrium respectively the right ventricle. Detected embolism was followed by a transient decrease of arterial pO2 (greater than 10 mmHg) in 5 pts. However, haemodynamic responses occurred infrequently; 4 pts experienced no changes at this moment. During insertion of the femoral prosthesis the contrast events were even more pronounced and persistent. In all pts we observed the appearance of "flake"-like structures passing the right atrium and the right ventricle, some measuring up to 6 cm in length. This was accompanied in 10 pts with a decrease (greater than 10 mmHg) of arterial pO2 and in 8 pts with a decrease (greater than 5 mmHg) of endtidal CO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1997

Intraoperative monitoring of substrate delivery during aneurysm and hematoma surgery: initial experience in 16 patients.

The effects of proximal occlusion of the parent artery during aneurysm surgery in humans are not fully understood, although this method is widely used. The reduction in substrate that can be tolerated by normal and subarachnoid hemorrhage (SAH)-affected brain is unknown. Therefore, the authors measured brain oxygen tension (brain PO2), carbon dioxide tension (brain PCO2), pH, and hemoglobin oxygen (HbO2) saturation before and after temporary occlusion in 12 patients with aneurysms. The effect of removal of a traumatic intracranial hematoma on cerebral oxygenation was also studied in four severely head injured patients. A multiparameter sensor was placed in the cortex of interest and locked by means of a specially designed skull bolt. The mean arterial blood pressure, inspired O2 fraction, and end-tidal PCO2 were analyzed. Brain PO2 and HbO2 saturation data were collected every 10 seconds. Descriptive and nonparametric analyses were used to analyze the data. A wide range in baseline PO2 was seen, although a decrease from baseline in brain PO2 was found in all patients. During temporary occlusion, brain PO2 in patients with unruptured aneurysm (seven patients) dropped significantly, from 60 +/- 31 to 27 +/- 17 mm Hg (p < 0.05). In the SAH group (five patients), the brain PO2 dropped from 106 +/- 74 to 87 +/- 73 mm Hg (not significant). Removal of intracranial hematomas in four severely head injured patients resulted in a significant increase in brain PO2, from 13 +/- 9 to 34 +/- 13 mm Hg (p < 0.05). The duration of safe temporary occlusion could not be determined from this group of patients, because none developed postoperative deterioration in their neurological status. However, the data indicate that this technique is useful to detect changes in substrate delivery during intraoperative maneuvers. This study also reemphasizes the need for emergency removal of intracranial hematomas to improve substrate delivery in severely head injured patients.

Adult↗
PubMed1993

[Monitoring intraoperative processing of acoustic stimuli with auditory evoked potentials].

130 Patients undergoing elective intra-abdominal, gynaecological, urological or cardiac surgery were studied after institutional approval and informed consent. In all patients auditory-evoked potentials (AEP) were recorded in the awake state and during general anaesthesia. Latencies of the peaks V, Na, Pa, Nb and P1 were measured. V belongs to the brainstem-generated potentials, which demonstrates that auditory stimuli were correctly transduced. Na, Pa, Nb, P1 are generated in the primary auditory cortex of the temporal lobe. During anaesthesia with isoflurane, enflurane, thiopentone, etomidate and propofol the peak V remains unchanged, whereas the mid-latency auditory-evoked potentials (MLAEP) show marked increases in latencies and decreases in amplitudes or are even completely suppressed. This indicates a successful stimulus transmission up to the level of the brainstem and midbrain. However, stimulus processing in the primary auditory cortex is blocked. Under increasing end-expiratory concentrations of isoflurane MLAEP show a dose-dependent increase of latencies and decrease of amplitudes. Under surgical anaesthesia with 1.2 vol%, MLAEP are nearly completely suppressed. A different picture can be seen when MLAEP were recorded during anaesthesia with the receptor-specific anaesthetics midazolam, flunitrazepam, diazepam, fentanyl and ketamine. During anaesthesia with receptor-specific anaesthetics, the brainstem peak V as well as the mid-latency components remain nearly unchanged compared with AEP from awake patients. This indicates that auditory stimuli reach the primary auditory cortex and are processed at a primary cortical level. With increasing doses of fentanyl one can observe only a significant decrease of amplitudes for the late component P1.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1988

Use of somatosensory evoked potentials for intraoperative monitoring of cerebral and spinal cord function.

EPs can be used in the operating room for monitoring the integrity of many levels of the central nervous system. SEPs can monitor the spinal cord, brain stem, and cerebral hemispheres. Such monitoring can alert the surgical team to the presence of complications, allowing prompt correction in some cases so as to prevent postoperative neurologic deficits. Monitoring can be done from stimulation of either the lower or upper extremity. Recordings can be taken over the scalp or can be made from electrodes put into the surgical site itself. Monitoring of the spinal cord is most often done for surgery involving scoliosis, spinal tumors, or arteriovenous malformations, and during crossclamping of the thoracic aorta. Animal models and human surgical experience has shown that monitoring the posterior columns is an effective way to assess the status of the motor pathways of the spinal cord, because the two pathways are both affected in almost all acute circumstances. Monitoring can also assess the functional status of the cerebral hemispheres. This is most often applied during carotid endarterectomy or repair of aneurysms of the carotid artery and its branches. Occasionally, this has also been applied to monitoring the cortex during cardiopulmonary bypass. Such EP monitoring does not cover the wide areas of cortex that can be monitored using EEG, but the EPs do tend to change and disappear at a level of ischemia nearer to the true critical level. Intraoperative median nerve EPs can also be used to identify the hand level of the motor and somatosensory cortex. Such identification of motor cortex can help guide neurosurgeons in their choice of how or where to perform a biopsy, excision, and the like. Overall, intraoperative evoked potential monitoring is becoming widespread because it is a practical way to help avoid neurologic complications, and it can be carried out using equipment already available in many hospitals. A substantial further review in this field can be found in Evoked Potential Monitoring in the Operating Room.

Brain Diseases↗
PubMed1986

[Importance of intraoperative monitoring of ABR and compound action potential of the eighth cranial nerve during microvascular decompression surgery].

An intraoperative recording of a direct compound action potential of the 8th cranial nerve with pre, intra and postoperative monitorings of auditory brainstem evoked response (ABR) was carried out for the purpose of clarifying mechanism and prevention of postoperative hearing dysfunction following microvascular decompression surgery as a treatment for hyperdysfunction syndrome of cranial nerves. In 221 patients with hemifacial spasm and tic douloureux out of 510 patients operated on by microvascular decompression surgery, ABR was monitored before, during and after surgery and furthermore, in the recent 94 patients among them, an intraoperative direct recording of a compound action potential of the acoustic nerve was performed simultaneously. Among these 94 patients, postoperative mild hearing dysfunction was encountered in 11 patients and severe reduction of hearing acuity in 2. As a result of our studies of monitoring action potential of the 8th cranial nerve and ABR, the following conclusions were drawn. When a latency of component V of ABR was delayed by more than 1.5-2.0 msec during surgery, and delay of latency of main negative peak (N1) of an action potential of the acoustic nerve exceeded by more than 1.0 msec, the occurrence rate of postoperative hearing dysfunction became positively high. There were two different types of changes in both ABR and action potentials; one type was a delay of an action potential in combination with that of ABR latencies and the other one was merely a delay in ABR components without following a remarkable change in action potentials. The former change might due to be an insult of whole neural pathways of the 8th cranial nerve including a cochlear nucleus and the latter change may due to be functional changes of the structures proximal to the cochlear nucleus. The delay of latencies in ABR and action potentials could be imposed either by a traction of the 8th cranial nerve or by a compression of the region of cochlear nucleus by a blain spatula as well as a vascular insufficiency of the tiny vessels which supplied these neural structures. To avoid the surgical insult to the acoustic nerve itself and more proximal neural pathways, the traction of any neural structures by a brain spatula should be lasted less than 5 minutes with more than 2 minutes intervals when judged from the results of our monitoring studies and the pressure of the compression on the cerebellar cortex is much preferable to be less than 20 mmHg for the safety throughout whole surgical procedures.

Adult↗
PubMed1985

[Sonographically monitored intraoperative fine-needle aspiration cytology in pancreatic diseases].

Intraoperative fine needle aspiration cytology of the suspected pancreatic region was carried out in 14 patients with a preoperatively confirmed tumour of the pancreas. Sonographic assessment revealed a malignoma in six cases and chronic pancreatitis in eight cases. All sonographic findings were confirmed by puncture cytology; there was no false negative or false positive diagnosis. Fine needle aspiration cytology monitored via sonography can help to further reduce the incidence of false negative findings in intraoperative cytology and can exercise a decisive influence on surgical procedure by intraoperative sonography-monitored staging.

Biopsy, Needle↗
PubMed1998

Intraoperative monitoring with somatosensory evoked potentials in carotid artery surgery--less reliable in patients with preoperative neurologic deficiency?

BACKGROUND: In a retrospective analysis of intraoperative somatosensory evoked potential (SEP) results during carotid artery surgery we found some cases with postoperative neurologic deficits, surprisingly without significant SEP changes. METHODS: Median nerve SEP were monitored as usual. Indication for selective shunting was a complete loss of amplitude N20/P25 in the first period of the investigation, later on a 50% reduction, or a prolongation of the central conduction time (CCT) of about 1.5 ms after cross-clamping. Anaesthesia was maintained with isoflurane in N2O/O2, fentanyl and atracurium. RESULTS: Over a 3-year period 146 patients were monitored. Indications were: transient ischaemic attacks (TIA) (n=51), stroke (n=23), stroke with residuals (n=39), asymptomatical stenosis (n=29), subclavian steal syndrome (n=4). Twenty-four patients received an intraluminal shunt following SEP alterations. Postoperatively, 5 patients (3.4%) had symptoms of intraoperative brain ischaemia (stroke n=2, TIA n=3), 4 of them showing only minor intraoperative SEP alterations; 1 received a shunt because of CCT prolongation. Four of these 5 patients had cerebral neurologic deficiency preoperatively. CONCLUSION: Since some authors have found a 100% sensitivity of intraoperative SEP, it is remarkable, that 1 patient with postoperative stroke and 3 patients with TIA had no significant SEP changes intraoperatively. We suppose there was an association with preoperative neurological deficits resulting from previous strokes. In such cases, regional critical ischaemia may apparently occur outside the sensory pathway monitored with SEP.

Aged↗
PubMed1981

Simple technique for monitoring intraoperative spinal cord function.

Interference with normal spinal cord functioning is an important, although uncommon, complication of spinal surgery. Spinal evoked potentials have been advocated as a means of monitoring spinal cord transmission during operative procedures. We have developed a simple technique using electrodes inserted into the interspinal ligaments for monitoring purposes. This has produced stable and reproducible recordings with obvious clinical benefit in the first 50 cases in which it has been used.

Evoked Potentials, Somatosensory↗