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PubMedDate not supplied

Prevention of spinal cord ischemia by monitoring spinal cord perfusion pressure and somatosensory evoked potentials.

The pressure difference between mean distal aortic pressure (MDAP) and cerebrospinal fluid pressure (CSFP), defined as relative spinal cord perfusion pressure (SCPP), and somatosensory evoked potentials (SEP) were monitored intraoperatively to detect and prevent intraoperative ischemic spinal cord injury in 19 patients who required cross-clamping of the descending thoracic aorta. Temporary axillo-femoral shunt utilizing a 10 mm woven Dacron tube graft was employed in 10 patients and partial cardiopulmonary bypass in nine. Ischemic SEP changes were seen in five patients. Two patients, whose SCPPs were 32 and 35 mmHg, experienced the complete loss of SEP and developed paraplegia. In the other three cases, increase of MDAP and/or withdrawal of cerebrospinal fluid (CSF) were performed to increase the SCPP to more than 40 mmHg when ischemic SEP changes occurred. SEP gradually recovered in two cases. The other patient underwent reimplantation of intercostal arteries since the ischemic SEP changes did not revert. These three patients recovered without any neurological deficit. In the other 14 cases without ischemic SEP changes, SCPP was kept at more than 40 mmHg during aortic cross-clamping. We conclude that the maintenance of SCPP at more than 40 mmHg by increasing MDAP and/or withdrawing CSF is an effective procedure in preventing postoperative paraplegia.

Adult↗

PubMed1997

[Does intraoperative transcranial doppler monitoring improve results of carotid endarterectomy?].

UNLABELLED: We evaluated the role of intraoperative transcranial Doppler sonography in improvement of carotid endarterectomy results. We analyzed the outcome of 38 carotid endarterectomies (CEA) performed in 22 female and 16 male patients with symptomatic carotid stenosis, aged between 43 and 78 years (av. 61.8 years). Constant measurements of peak and average velocity (Va) were taken during following stages of CEA:-after anaesthesia--during 120 s crossclamp test, -after shunt insertion (5 patients),-immediately after and 5 min after crossclamp release. RESULTS: We obtained following values of Va in particular stages of CEA:-after anaesthesia 0.54 m/s (0.38-1.08),-during 120 s crossclamp test 0.25 m/s (0.12-0.58),-after shunt insertion 0.47 m/s (0.32-0.78),-immediately after crossclamping 0.72 m/s (0.51-1.40),-5 min. after crossclamp release 0.62 m/s (0.42-1.27). In 2 cases no blood flow velocity increase was found after shunt insertion. The immediate correction of shunt positioning was done. In 2 other patients no hemodynamic effect after CEA was detected (no blood flow velocity increase in MCA and at the same time, no neurological impairments were noticed). After quick investigation inferior carotid artery kinking above the arteriotomy site and its stenosis after suturing were found. Both of these abnormalities were removed and since that moment the blood flow velocity in MCA increased, in comparison with preoperative values. CONCLUSIONS: intraoperative transcranial doppler monitoring 1) allows to identify any kind of blood flow disturbance in MCA during each stage of CEA which appears before neurological impairment, 2) gives the possibility of shunt functioning evaluation, 3) enables to avoid intraoperatively unpredictable situations that may result in imminent cerebral ischemia, 4) 70% decrease of blood flow velocity in MCA is the indication for shunt insertion, 5) proved to be very helpful in (in 10% of our material) improving the results of all carotid endarterectomies.

Adult↗

PubMed1997

Does laser Doppler flowmetry aid the prevention of ischemic colitis in abdominal aortic aneurysm surgery?

Acute ischemic colitis is noted as a rare but lethal complication of abdominal aortic aneurysm (AAA) surgery. Because of its high mortality a reliable method of monitoring colonic blood perfusion to predict the possible occurrence of ischemic colitis is highly desirable for AAA surgery. We have tested the use of a laser Doppler flowmeter placed on the surface of the sigmoid colon for intraoperative monitoring in 31 patients with AAA. Although most of the patients showed the same flow levels after aorto-iliac or aorto-femoral grafting (at least unilaterally the internal iliac artery was perfused), in 6 cases poor colonic perfusion (below 50% of the basal flow) was observed and inferior mesentric arterial reconstruction was performed. In these 6 patients, sigmoid colonic blood perfusion returned from 37% to 82% of preoperative value after the reconstructions. No ischemic colitis was noted in this series of patients. We suggest that monitoring of serosal blood flow in the sigmoid colon using a laser Doppler flowmeter is useful for the management of patients during abdominal aortic aneurysm surgery.

Acute Disease↗

PubMed1994

Intraoperative cardiac output monitoring: comparison of impedance cardiography and thermodilution.

Impedance cardiography (IC) is a noninvasive, simple to use method of cardiac output (CO) determination. A prospective evaluation of IC monitoring was performed in 50 patients undergoing noncardiac surgery. IC CO measurements (NC-COM3-Revision 7, BoMed Manufacturing) were compared to simultaneous measurements of thermodilution (TD) CO to assess the validity of this technique for intraoperative cardiac monitoring. Adequate impedance signals could not be obtained in 7 of the 50 patients. IC CO measurements were highly correlated to TD CO (P < .005), with a correlation coefficient r = 0.84. Bias analysis, however, indicated clinically significant disagreement between the two techniques. IC CO tended to underestimate TD CO (mean bias = -0.41 L/min) and the SD of the bias was 1.0 L/min (95% level of agreement 1.6 to -2.4 L/min). Trending data showed IC to accurately track the direction of TD CO changes but to underestimate their magnitude (r = 0.60, intercept -0.7 L/min, slope 0.47). Factors that may have impaired the performance of IC in this study include the high prevalence of cardiac disease in the study population and electrical noise in the operative setting. Further development of IC appears warranted if it is to prove useful as an intraoperative cardiac monitor.

Aged↗

PubMed2002

Radioguidance is not necessary during parathyroidectomy.

BACKGROUND: Improvements in the accuracy of preoperative localization and the availability of the rapid parathyroid hormone assay have permitted minimally invasive parathyroidectomy in patients with primary hyperparathyoidism. HYPOTHESIS: The use of intraoperative radioguidance is beneficial during targeted parathyroid operations. DESIGN: A retrospective analysis of a prospective database of patients. SETTING: Tertiary care referral center. PATIENTS: During a 2(1/2)-year period, 130 patients underwent minimally invasive, targeted parathyroidectomy with intraoperative monitoring of the parathyroid hormone level. Of these, 60 patients underwent radioguided parathyroidectomy. Prior to surgery, a solitary parathyroid adenoma was visualized on technetium Tc 99m sestamibi scintigraphy in all patients selected for radioguided parathyroidectomy. A gamma probe was used to guide the surgical dissection. RESULTS: All patients were cured following radioguided parathyroidectomy. In 29 patients (48%), the probe provided confusing or inaccurate information; however, a unilateral neck exploration with excision of a parathyroid adenoma was successfully completed in each of these patients. Forty-three cases were completed under local anesthesia and 85% were discharged home on the same day of surgery. There was 1 temporary recurrent laryngeal nerve palsy. CONCLUSION: In the era of improved preoperative localization and intraoperative parathyroid hormone monitoring, the routine use of radioguidance is not recommended during parathyroidectomy.

Adenoma↗

PubMedDate not supplied

Acute deformity correction of lower extremities under SSEP-monitoring control.

Intraoperative somatosensory evoked potential (SSEP) monitoring was performed in eight children who had undergone an acute deformity correction in the lower extremities using external fixation. Five patients showed stable evoked potentials during surgery and had no neurologic complications postoperatively. Three patients experienced evoked potential abnormalities. In one patient, 60 degrees external rotation of the foot produced significant SSEP changes. The reduction of rotation to 40 degrees resulted in tibial but not peroneal SSEP recovery. Peroneal nerve deficit was noted postoperatively. The second patient showed substantial SSEP attenuation after 45 degrees correction of distal tibial valgus. However, spontaneous recovery of the response occurred, which allowed maintenance of the achieved correction. In a third patient, significant SSEP changes occurred after 90 degrees external rotation and 10 mm medial translation of the distal femur. Total release of translation allowed 75 degrees external rotation without SSEP abnormalities. Neither of the latter two patients had peripheral nerve deficits postoperatively. Intraoperative SSEP monitoring thus helps to define a neurologically safe limit of acute deformity correction.

Adolescent↗

PubMed1996

Intraoperative transcranial Doppler sonography monitoring during carotid surgery under locoregional anaesthesia.

OBJECTIVES: Studies comparing transcranial Doppler ultrasonography (TCD) with other intraoperative monitoring techniques for detecting clamping ischaemia during carotid endarterectomy under general anaesthesia suggest that a reduction of > two-thirds in the mean middle cerebral artery velocity (mMCAv) or a reduction of > 0.4 in the preclamping mMCAv: clamping mMCAv ratio warrants cerebral protection. Our aim was to study the relationship between mMCAvs and clamping ischaemia during carotid endarterectomy in awake patients. MATERIALS AND METHODS: In a consecutive series of 57 patients undergoing carotid endarterectomy under locoregional anaesthesia 51 were monitored by intraoperative TCD, continuous EEG, and neurologic awake testing. RESULTS: Five of the 51 (9.8%) patients had transient clamping ischaemia, which carotid shunting reversed. TCD showed that these five patients had significant lower mean mMCAvs than the other 46 patients, who had no deficits (1.8 +/- 1.1 cm/s vs. 26.2 +/- 8.5, p = 0.0003). Current TCD criteria indicated that four other patients (7.8%) should have been shunted. All four had significantly higher clamping mMCAvs than the five shunted patients (11.5 +/- 1.9 vs. 1.8 +/- 1.1, p = 0.0012). CONCLUSIONS: Intraoperative TCD detected cerebral ischaemia and yielded no false-negative. An mMCAv of 10 cm/s or less may indicate the risk of clamping ischaemia better than the higher threshold currently proposed. This would avoid unnecessary shunting due to false-positives.

Aged↗

PubMed1989

Intraoperative brainstem auditory evoked potentials: significant decrease in postoperative morbidity.

Evoked potentials are commonly used for intraoperative monitoring of neural tissue under surgical threat despite the lack of unequivocal evidence demonstrating its effectiveness in preventing neural injury. This study retrospectively compares the auditory morbidity of posterior fossa microvascular decompressive surgery before and after the introduction of intraoperative brainstem auditory evoked potentials (BAEPs). All patients underwent a similar operative procedure performed by a single surgeon. The two groups were comparable with regards to age, sex, and indications for surgery. In the nonmonitored group, auditory morbidity had not declined with increasing experience of the surgeon. Ten of 152 patients (6.6%) suffered a profound hearing loss in the nonmonitored group. In the monitored group, none of 70 patients suffered a profound hearing loss. We attribute this significant decline (p = 0.02) in morbidity to the introduction of intraoperative BAEPs. We believe this to be the first demonstration of a significant decrease in operative morbidity directly associated with the use of intraoperative evoked potential monitoring.

Audiometry↗

PubMed1999

Reoperative parathyroid surgery in the era of sestamibi scanning and intraoperative parathyroid hormone monitoring.

HYPOTHESIS: Results of reoperative parathyroid surgery (RPS) have improved with the advent of sestamibi parathyroid subtraction scanning and intraoperative parathyroid hormone (IOPTH) monitoring. DESIGN: Retrospective review of patient histories, preoperative localization studies, operative data, including IOPTH monitoring, and outcomes for patients undergoing recent RPS at a single institution. Follow-up was complete (mean, 20 months). SETTING: Tertiary care referral center. PATIENTS: All patients undergoing RPS for benign persistent or recurrent primary hyperparathyroidism during the period 1989 to 1997. MAIN OUTCOME MEASURES: Overall cure rate and operative morbidity from RPS; sensitivity and accuracy of preoperative localization studies; and prediction of cure from IOPTH monitoring. RESULTS: The study group included 124 patients (87 women and 37 men). Hypercalcemia was corrected in 109 patients (88%). Permanent recurrent laryngeal nerve injury occurred in 0.8% and permanent hypoparathyroidism in 13% of patients. Test sensitivities and accuracies, respectively, were as follows: ultrasound with biopsy, 90% and 82%; sestamibi parathyroid subtraction scanning, 82% and 67%; and ultrasound alone, 75% and 65%. Level of IOPTH was predictive of cure in all patients with a 70% or greater fall from baseline at 20 minutes after excision. Persistent multigland disease was the major cause for reoperative failure (73%). CONCLUSIONS: Neither cure rates nor operative morbidity have changed appreciably over the past 2 decades, despite the introduction of sestamibi parathyroid subtraction scanning and IOPTH monitoring. Multigland disease continues to represent the principal cause of failure in RPS despite the routine use of preoperative localization studies. Thus far, increasing the stringency of IOPTH monitoring from a 50% to 70% decline from baseline levels has been predictive of cure, even in multigland disease. Most missed abnormal glands reside in normal anatomic locations, and the need for multiple operations, not just the reoperation, results in the increased morbidity seen with RPS.

Adolescent↗

PubMed1990

Role of transcranial Doppler in carotid surgery.

Transcranial Doppler is a method for visualizing the intracranial circulation that has applications to the preoperative investigation of cerebrovascular disease. Estimations of the adequacy of collateral circulation around the circle of Willis may be made. In addition, the method may be used for intraoperative monitoring during carotid, cardiac, or neurosurgical procedures.

Arterial Occlusive Diseases↗

PubMedDate not supplied

Monitoring arterial surgery: a comparison of pulse volume recording and electromagnetic flowmetering in aortofemoral reconstruction.

Intraoperative monitoring of aortofemoral reconstruction using Pulse Volume Recordings (PVR) and Doppler ankle systolic pressure indices (ASPI) is compared with volume blood flow obtained by electromagnetic flowmetering (EMF). Twenty-five patients aged 45-78 with limb ischaemia or abdominal aortic aneurysm were studied before and 20 minutes after reconstruction. Reconstruction of isolated iliac occlusions (25 limbs) produced immediate improvement in PVR results. PVR waveform pulsatility (upstroke time shortened; 249-183 msec, p = less than .001) was more sensitive than amplitude which was restored to pre-reconstruction levels (16.1 to 17.5 mm). Similar trends were seen in multisegment disease. PVR transit time was not as sensitive. EMFlow was increased in both groups (229-600 and 160-308 mls/min). ASPI was not useful. Both PVR amplitude and pulsatility were significantly correlated with EMF volume flow, but pulsatility was more sensitive and was a superior predictor of successful arterial revascularisation. Technical errors were detected and corrected, and 94% of grafts were patent on discharge. These results show a correlation between PVR pulse waveform shape and EMFlow to such an extent that PVR results may be taken as a useful indicator of successful arterial reconstruction.

Aged↗

PubMed1999

A complication of intraoperative facial nerve monitoring: facial skin burns.

OBJECTIVE: To report on three cases of severe facial skin burns resulting from intraoperative facial nerve monitoring in patients undergoing parotidectomies. STUDY DESIGN: This study is a retrospective case review. SETTING: A tertiary referral center. PATIENTS: This study includes three patients who underwent parotidectomies with concurrent facial nerve monitoring. RESULTS: Facial skin burns were proven to result from a technical defect of the intraoperative facial nerve monitoring device. Burns were sustained at electrode insertion sites and their extent was related to the duration of monitoring. The most probable explanation of these burns is electrolysis. CONCLUSIONS: Successful retracing of technical defaults with biomedical engineers at the device manufacturer have led to the upgrade of the facial nerve monitor apparatus. The benefits of facial nerve monitoring largely outweigh the fortuitous occurrence of skin burns reported in this study. Therefore, this complication should not represent a drawback to the use of facial nerve monitoring.

Adult↗

PubMed1986

Real-time monitoring of brainstem auditory evoked response (BAER) during cerebellopontine angle (CPA) surgery.

The signal-to-noise ratio of brainstem auditory evoked responses (BAER) can be greatly enhanced by use of optimal digital filtering before averaging. This permits accurate assessment of auditory nerve status every 5 to 10 seconds, making real-time intraoperative monitoring possible. The major advantages yielded by real-time monitoring--in our experience thus far--have been identification of potentially adverse functional consequences of apparently uneventful surgical maneuvers, reducing postoperative dysfunction, early indication of potential for improved clinical function, and potential identification and localization of neural tissue in the face of absent surgical landmarks. Examples of these advantages will be provided from case studies, and the possibility that real-time monitoring may improve ability to preserve hearing will be discussed.

Cerebellar Neoplasms↗

PubMed1988

Spinal cord monitoring during posterior spinal instrumentation and fusion.

Two hundred seventy-five consecutive patients who were treated by posterior spinal instrumentation and fusion with iliac crest bone graft were intraoperatively monitored using cortical somatosensory-evoked potentials without a planned wake-up test. The monitoring was performed using a TECA TE-4 system that included an electromyograph, a nerve stimulator, and a digital averager. Intraoperatively, six patients (2%) demonstrated significant changes in evoked potentials, consisting of either marked increase in latency or a loss of wave form during instrumentation of the spine. The instrumentation was removed immediately and the evoked potentials returned to base-line tracing within 15-30 minutes in all six cases. Five patients who had instruments refitted to maintain a lesser amount of correction had no subsequent change in the evoked potentials. One patient had spinal fusion without instrumentation. Postoperatively, all patients are neurologically normal.

Adult↗

PubMed1999

Intraoperative motor evoked potentials monitoring in spinal neurosurgery.

Neurological damage may follow even a technically accurate spinal surgery. The intraoperative monitoring of neurological functions put at risk by the operation is a method utilized to correctly identify the topography of neural structures and to avoid surgical insults. SEPs monitoring is 20 year old, and only recently direct motor tract monitoring has become possible. Transcranial electrical motor cortex stimulation with single pulses or with short trains of stimuli and recording of the evoked responses from the spinal epidural space (D-waves) and from limb muscles is a reliable and safe technique for monitoring corticospinal tract activity even under general anesthesia. The method has a solid theoretical experimental background. Its clinical application has demonstrated high sensitivity and specificity. Intraoperative MEPs monitoring is nowadays considered indispensable during spinal neurosurgery.

Animals↗

PubMed2000

Ischemia after carotid endarterectomy: comparison between transcranial Doppler sonography and diffusion-weighted MR imaging.

BACKGROUND AND PURPOSE: Hyperintense signals on diffusion-weighted MR images (DWIs) are believed to correspond accurately with cerebral ischemic events. Intraoperative transcranial Doppler sonography (TCD) can reveal hemodynamic and embolic events during carotid endarterectomy (CEA). Our purpose was to determine whether the occurrence of hyperintense signals on postoperative DWIs corresponds to intraoperative embolic or hemodynamic events. METHODS: Seventy-seven CEAs were monitored intraoperatively with TCD to record blood flow velocity changes after cross clamping to ascertain the presence of adequate collateral flow and to record microembolic signals. DWI was used to classify the hemisphere ipsilateral to the CEA by type: 0, no lesions (n = 51); I, cortical lesions only (n = 2); II, subcortical white matter lesions only (n = 6); III, mixed type with cortical and subcortical lesions (n = 11); IV, large territorial infarcts (n = 6); and V, other types of lesions (n = 1). RESULTS: Neither the five clinical events (one transient ischemic attack, two minor strokes, and two major strokes) nor any DWI type (I-V) showed a relationship to blood velocity decreases after cross clamping or, in patients who were selectively shunted, to total ischemic time necessary for shunt insertion and removal. Total microembolic signal count was significantly higher in the five CEAs with clinical events than in those without. It was also higher on the DWIs showing a hyperintense lesion as compared with DWIs showing no lesion. CONCLUSION: Apart from lesions corresponding to clinical deficits, CEA is associated with a substantial number of small areas of brain tissue at risk for irreversible ischemia. The main cause of intraoperative stroke seems to be embolism, suggesting that microembolic signals in CEA are highly relevant events for brain tissue.

Brain Ischemia↗

PubMedDate not supplied

Intraoperative spinal cord monitoring during surgery for aortic aneurysm: application of spinal cord evoked potential.

Spinal cord evoked potentials elicited by direct stimulation of the spinal cord were monitored in 21 patients during thoracic or thoraco-abdominal aortic aneurysm surgery. Flexible catheter-type electrodes were used for both stimulating and recording. The basic pattern of the spinal cord evoked potential consisted of an initial spike and a subsequent polyphasic component. The earliest and most frequent alterations after cross-clamping of the aorta were changes in the configuration or amplitude of the polyphasic component. In 13 patients who exhibited no change except minor alterations of the polyphasic component during the initial test clamping for 15 or 20 min, subsequent graft replacements were safely performed without reimplantation of intercostal vessels. In 2 patients who had sudden cardiac arrests, the evoked potential completely disappeared. The polyphasic component disappeared first, followed by the initial spike. Another patient developed acute loss of the potential after the aneurysm was incised, presumably due to distal aortic hypoperfusion. In this case, prolonged distal hypotension resulted in flaccid paraplegia. Intraoperative monitoring of the spinal cord evoked potential is a useful method for the early detection of spinal cord ischemia during surgery requiring aortic occlusion.

Adult↗

PubMed1997

Prognostic factors in intraoperative facial nerve monitoring for acoustic neuroma.

OBJECTIVES: To determine the predictive value of intraoperative threshold stimulus for facial nerve outcome and the prevalence and prognostic value of persistent trains of activity and frequent spontaneous or mechanically induced contractions during acoustic neuroma surgery. STUDY DESIGN: Prospective recording and subsequent review of facial nerve activity. SETTING: Tertiary referral centre. PATIENTS AND METHODS: Consecutive patients undergoing acoustic neuroma surgery. Intraoperative facial nerve activity was digitised and stored on a personal computer for future analysis. Operative events were flagged. Recordings were available in 27 patients. MAIN OUTCOME MEASURES: Frequent mechanically induced contractions (< 20), prolonged trains of facial nerve activity (total time > 199 seconds), and facial nerve brainstem stimulus threshold were correlated with facial nerve outcome. RESULTS: A brainstem stimulus threshold > 0.1 mA was significantly associated with intermediate or poor facial nerve function (House-Brackmann grade > 2) on the sixth postoperative day, at 1 month and 6 months. Patients with normal or near-normal facial function on the first day and a threshold of > 0.1 mA were significantly more likely to develop a delayed facial nerve palsy. Frequent contractions were noted in 74% of patients and persistent train activity in 59%. Neither was predictive of facial nerve outcome. CONCLUSIONS: An elevated brainstem threshold is helpful in predicting delayed facial nerve palsy and suboptimal facial nerve outcome. Persistent train activity and frequent contractions, do not have major prognostic significance.

Adult↗