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PubMed1985

Spinal cord monitoring: current status and new developments.

A review of current techniques and results of monitoring spinal cord function by the intraoperative testing of somatosensory evoked potentials is given. The criteria for an ideal monitoring method are defined: (1) potential alterations occur before the lesion is irreversible, (2) monitoring itself does not harm the patient, (3) there are no false-positive or false-negative results, (4) warning criteria are defined by objective and quantifiable parameters. In recording and stimulation, two different approaches are applied: cortical or spinal recording and peripheral or spinal stimulation. Spinal stimulation techniques are considered more invasive, but an averaged potential is obtained quicker and more reliably by spinal methods. Failure rates in establishing useful monitoring procedures vary between 2.85 and 5%. The N2O-analgesic-relaxant-type of anesthesia is recommended. A precise definition of criteria indicating spinal cord damage has been difficult because of the natural variability of intraoperative evoked potentials. Wide ranges of physiologic, anesthesiologic, and technical and surgical factors have been found to influence intraoperative potential monitoring adversely. The so-called warning criteria drawn from evoked potential changes have so far been set arbitrarily: amplitude reductions of 30-50% for several recordings or at least 15 minutes have mostly been used. It has become clear, however, that warning criteria should be different for healthy or impaired spinal cord function and for cortical and spinal recordings. The value of a lesion-specific spinal cord potential for monitoring remains to be clarified. SEPs are sensitive for demonstrating ischemic changes to the spinal cord, but the limited experience with these lesions does not allow firm conclusions regarding the reversibility of clinical and evoked potential changes in spinal cord ischemia in man. The limited experience with multilevel recording, i.e., simultaneously recording at spinal and cortical level, indicates that epidural recordings are less variable and less failure-prone than cortical recording. Simultaneous multilevel recording also gives more information and allows easier recognition of false-positive or false-negative results. Poor preoperative SEP nearly always preclude useful monitoring. The results obtained so far point out areas where further development is necessary in order to increase the efficacy of this method. Major unsolved problems are (1) definition of warning criteria, (2) incidence of false-positive and false-negative findings, and (3) improvement of data acquisition.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthetics↗
PubMed1987

Medical monitoring. What is it, how can it be improved?

Little has been published about optimizing medical monitoring protocols, although monitoring accounts for over half of all medical laboratory tests. Monitoring is a form of surveillance consisting of repeated testing intended to detect a specified change in a patient indicating a change in his prognosis, need for treatment or need for a change in treatment. The concept of monitoring overlaps with those of screening and diagnosis. One may monitor a physiologic or pathologic process, a therapeutic or noxious agent, comparing results with the patient's previous results or with a group reference range. Pertinent questions include: what are the indications, what is to be monitored, which tests are to be used, when to start, how frequently to test, when to stop. Preliminary improvement of monitoring protocols may be achieved by applying common sense guidelines for medical decision making; using best estimates of test characteristics, of possible risks and benefits of testing, not testing, treating and not treating. Sensitivity analysis may help determine when further clinical research is needed.

Decision Making↗
PubMed1988

Evaluation of the Dinamap continuous blood pressure monitor.

The validity of the Dinamap automated oscillometric blood pressure monitor, an instrument frequently used for continuous monitoring in intensive care settings, was evaluated in comparison to two standard methods of blood pressure measurement. Oscillometric monitoring was compared to random-zero sphygmomanometry in 28 ambulatory subjects, using the instruments in a random order. The oscillometric monitor overestimated random-zero systolic pressure (mean difference = 5.7 mm Hg; P less than 0.001), but did not differ in diastolic pressure (difference = 1.3 mm Hg, P greater than 0.3). Correlation (r) between methods was 0.94 for systolic pressure and 0.83 for diastolic pressure. Repeatability of sequential measures did not differ between methods. To evaluate the oscillometric monitor in the intraoperative setting, it was used simultaneously with a radial artery catheter to measure blood pressure in 14 patients undergoing peripheral vascular or other major surgery. The oscillometric monitor underestimated intra-arterial systolic pressure (mean difference = -9.4 mm Hg; P less than 0.002), but overestimated intraarterial diastolic pressure (difference = 5.7 mm Hg; P less than 0.005). There was no difference in mean arterial pressure (P greater than 0.1). Correlation between methods was 0.88 for systolic, 0.71 for diastolic, and 0.79 for mean arterial pressure. The oscillometric instrument had a sensitivity of 63% and specificity of 97% in detecting intraarterial systolic pressures of 160 mm Hg or greater, and a sensitivity of 89% and specificity of 89% in detecting intraarterial systolic pressures of 100 mm Hg or less. These findings demonstrate differences between the oscillometric monitor and other standard methods of blood pressure measurement.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗
PubMed2004

ASHP national survey of pharmacy practice in hospital settings: monitoring and patient education--2003.

PURPOSE: Results of the 2003 ASHP national survey of pharmacy practice in hospital settings that pertain to monitoring and patient education are presented. METHODS: A stratified random sample of pharmacy directors at 1173 general and children's medical-surgical hospitals in the United States was surveyed by mail. SMG Marketing Group, Inc., supplied data on hospital characteristics; the survey sample was drawn from SMG's hospital database. RESULTS: The response rate was 47.1%. Virtually all hospitals (95.3%) had pharmacists regularly monitoring medication therapy in some capacity. Patient monitoring has improved since 2000; fewer respondents reported monitoring less than 25% of patients in the hospital, and most hospitals reported an increase in the amount of time pharmacists devoted to monitoring activities. Pharmacists were provided computer access to laboratory information in 78% of hospitals to facilitate this function. Detection and reporting of adverse drug events (ADEs) have substantially increased since 1999, with an increase of 42% in events reported internally. Strategies to improve ADE reporting were in place in 84% of hospitals, indicating that pharmacists are adopting the widely recommended philosophy of learning from errors. Errors were less widely reported externally, limiting the value of aggregated data for improving the medication-use process. Most hospitals (85.5%) had an interprofessional infrastructure in place to discuss and learn from voluntary reports of ADEs. Medication counseling continued to be relatively infrequent, with nearly three fourths of hospitals reporting fewer than 26% of inpatients received medication education. Pharmacist staffing in hospitals has risen significantly, from an average of 8.6 full-time equivalents (FTEs) in 2002 to 9.4 FTEs per hospital. Vacancy rates for pharmacists decreased from 7.3% in 2002 to 43%. It is now estimated that there are 1846 vacancies in hospital pharmacies. CONCLUSION: Notable improvements in hospital pharmacy practice have been made. The percentage of patients whose medication therapy is monitored by pharmacists has increased, and most hospitals reported that the amount of time pharmacists spent monitoring patients' medication therapy had increased. Internal and external reporting of ADEs has increased, and pharmacist vacancies have decreased from 2002. Staffing has also improved, suggesting an abatement of the critical shortage of pharmacists in the hospital setting.

Adverse Drug Reaction Reporting Systems↗
PubMed2006

Assessment of personal direct-reading dust monitors for the measurement of airborne inhalable dust.

The performances of five portable direct-reading dust monitors were investigated in a wind tunnel for a range of industrial dusts and three sizes of aluminium oxide test dust to mainly determine their suitability for measuring the inhalable fraction of airborne dust in workplaces. The instruments tested were Split 2 (SKC Ltd), Sidepak (TSI Inc.), Dataram (Thermo Electron Ltd), PDS-2 (Sibata Scientific Technology Ltd) and the Respicon TM (Hund Ltd). The instruments' responses were compared with reference dust samplers. These were the IOM sampler for the inhalable fraction and the Casella cyclone sampler for the respirable fraction. All instruments are predominantly responsive to and are designed to measure particles in the respirable size range, although two of the instruments, the Split 2 and Respicon TM, are claimed to be capable of measuring inhalable-sized particles. For the purpose of the tests, major modifications to an existing wind tunnel dust injection system were made to facilitate the generation of uniform concentrations of large inhalable-sized dust particles at low air velocities. Each monitor greatly underestimated the measurement of inhalable concentration for all the dusts tested, although the linearity was good over a wide range of concentrations for any particular size distribution of dust. However, their calibration factors, defined as the ratio of reference inhalable concentration to monitor concentration, were especially sensitive to changes in particle size as the response of the instruments decreased rapidly with increasing particle size. The monitors generally overestimated the measurement of respirable dust concentration by up to a factor of about 2, apart from the PDS-2, which underestimated it by a factor of up to 3. There was, however, a great deal more scatter in the reference respirable concentration measurements owing to the collection of small dust samples. Therefore, monitor linearity and effects of monitor response to changes in particle size could not be accurately investigated for the respirable fraction. The sampling head of the Split 2 monitor incorporates an IOM inlet and filter to gravimetrically collect the inhalable fraction of airborne dust. This can give a concurrent reference measure of inhalable airborne dust concentration. However, poor sealing within the sampling head resulted in some of the sampled dust not reaching the backup filter. This resulted in the Split 2 underestimating the reference inhalable dust concentration, which meant that it could not be accurately used as a calibration standard. Communications with the manufacturers have since revealed that the sampling head has recently been redesigned in order to improve the seal and eliminate leakage. The Respicon sampler gravimetrically underestimated the inhalable dust concentration, and did so increasingly as the particle size increased.

Air Pollutants, Occupational↗
PubMed2002

Development of an automated shielded chair whole-body monitor.

A standard shielded chair whole-body monitor has been developed as a computer controlled, unattended, walk-in-type of whole-body monitor for internal dosimetry of radiation workers. A radiation worker enters his personal computer code through the attached computer terminal and follows a few instructions on the screen. The chair door then opens automatically and after the worker has positioned himself into the counting geometry in the chair, the door closes. At the end of the whole-body monitoring for a pre-set time, the chair door opens again and the worker moves out. The monitoring data acquired on a 4K-MCA is saved in the computer memory automatically and the chair door closes again making it available for monitoring the next worker. The system also gives audio instructions to the worker to occupy the chair and to move out after the counting is over. A system supervisor can come at any convenient time and get a print out of the monitoring report in the standardised format or carry out any detailed analysis if required. The system has the software for calculating intakes and the committed effective doses using the latest ICRP methodologies, from the measured retained activities of the various important fission and activation products like 137Cs, 131I, 60Co, 125Sb etc. This type of system with trained staff is also expected to be of value in case of emergencies as a quick monitoring system.

Automation↗
PubMed2003

Design and implementation of monitoring programmes for internal exposure (project OMINEX).

The costs of monitoring for internal exposure in the workplace are usually significantly greater than the equivalent costs for external exposure. Therefore, there is a need to ensure that resources are employed with maximum effectiveness. The EC-funded OMINEX (optimisation of monitoring for internal exposure) project is developing methods for optimising the design and implementation of internal exposure monitoring programmes. Current monitoring programmes are being critically reviewed, the major sources of uncertainty in assessed internal dose investigated, and guidance formulated on factors such as programme design, choice of method/techniques, monitoring intervals, and monitoring frequency. OMINEX will promote a common, harmonised approach to the design and implementation of internal dose monitoring programmes throughout the EU.

Body Burden↗
PubMed2006

Influence of environmental changes on continuous radon monitors. Results of a Spanish intercomparison exercise.

The first Spanish intercomparison exercise for continuous radon monitors was carried out with the participation of nine monitoring systems from eight laboratories. The exposures were carried out in the radon and thoron chambers at the Institute of Energy Techniques (INTE) of the Technical University of Catalonia (UPC), which is considered to be the Spanish reference chamber. The monitors were exposed to three different temperatures (13, 20 and 30 degrees C), relative humidities (30, 45 and 80%) and radon concentrations (450, 2000 and 9000 Bq m(-3)). Exposures in the thoron chamber were carried out at concentrations of approximately 450 Bq m(-3). The response of the ionisation chambers and scintillation monitors was acceptable. However, the response of monitors based on electrostatic collection was found to be influenced by external climatic conditions. Moreover, all radon monitors were sensitive to thoron concentration, which was especially significant for scintillation monitors.

Air Pollutants, Radioactive↗
PubMed2001

Noninvasive monitoring of carbon dioxide during mechanical ventilation in older children: end-tidal versus transcutaneous techniques.

UNLABELLED: We prospectively compared the accuracy of end-tidal CO(2) (ETCO(2)) and transcutaneous CO(2) (TCCO(2)) monitoring in older pediatric patients (4 yr or older) receiving mechanical ventilation for respiratory failure. ETCO(2) and TCCO(2) were simultaneously monitored and compared with arterial CO(2) (PaCO(2)) values when arterial blood gas analysis was performed. Eighty-two sample sets were compared. The ETCO(2) to PaCO(2) difference was 6.4 +/- 6.3 mm Hg, whereas the TCCO(2) to PaCO(2) difference was 2.6 +/- 2.0 mm Hg (P < 0.0001). The absolute difference of ETCO(2) and PaCO(2) was 5 or less in 47 of 82 measurements, whereas the absolute TCCO(2) to PaCO(2) difference was 5 or less in 76 of 82 measurements (P < 0.00001). Regression analysis of ETCO(2) and PaCO(2) values revealed a correlation coefficient of 0.5418 and an r value of 0.8745. Regression analysis of TCCO(2) and PaCO(2) values revealed a correlation coefficient of 1.0160 and an r value of 0.9693. Bland-Altman analysis revealed a bias of -5.68 with a precision of +/-6.93 when comparing ETCO(2) with PaCO(2) and a bias of 0.02 with a precision of +/-3.27 when comparing TCCO(2) and PaCO(2) (P < 0.00001). TCCO(2) monitoring provided an accurate estimation of PaCO(2) over a wide range of CO(2) values and was superior to ETCO(2) monitoring in older pediatric patients with respiratory failure. TCCO(2) monitoring may be considered as a useful adjunct to monitoring of ventilation in this patient population. IMPLICATIONS: The authors report on the accuracy of noninvasive, transcutaneous CO(2) monitoring during mechanical ventilation in children 4 yr or older. Application of this technique should be useful by decreasing the need for repeated, costly, and sometimes painful arterial blood gas analysis, and the continuity of assessment should facilitate proactive, rather than reactive, ventilator manipulations.

Adolescent↗
PubMed2002

The neuromuscular transmission module versus the relaxometer mechanomyograph for neuromuscular block monitoring.

UNLABELLED: The neuromuscular transmission module (M-NMT) is an integrated piezoelectric motion sensor module incorporated in the AS/3(TM) anesthesia monitor. We compared the neuromuscular block of 0.6 mg/kg rocuronium (twice the 95% effective dose) monitored by the M-NMT with that monitored by the Relaxometer mechanomyograph (MMG). The two monitors were alternately allocated to the left or right hands of 20 patients. T(1)%, the first twitch of the train-of-four (TOF), and the TOF ratio (T(4)/T(1)) were used for evaluating the neuromuscular block. There was no significant difference in the mean (min) plus minus SD onset time or time to 0.8 TOF ratio recovery measured by the M-NMT (1.5 plus/minus 0.3, 49.4 plus/minus 8.1) compared with MMG (1.8 plus/minus 0.6, 50.9 plus/minus 9.9), respectively. However, the time (min) to 25% T(1) recovery was significantly longer when monitored by the M-NMT (25.6 plus/minus 8) than by the MMG (20.2 plus/minus 6.3). During recovery from neuromuscular block, the difference between the TOF ratios measured by the two monitors showed a bias of -0.031, and the limits of agreement (bias plus/minus 1.96 SD) were -0.281 and +0.22. The M-NMT monitor could determine the time to tracheal intubation as well as full recovery from neuromuscular block, but it lagged behind the MMG in determining the time to rocuronium repeat dose administration. IMPLICATIONS: Compared with the Relaxometer mechanomyograph, the neuromuscular transmission module could equally indicate time to tracheal intubation and full recovery from 0.6 mg/kg rocuronium neuromuscular block. Its small quick-fit sensor has the advantage, in an often crowded and busy operating room, of being incorporated in the AS/3(TM) anesthesia workstation.

Androstanols↗
PubMed1994

Multisite evaluation of a continuous intraarterial blood gas monitoring system.

BACKGROUND: We compared the performance of a new, continuous intraarterial blood gas (CIABG) monitor with arterial values obtained periodically and analyzed by conventional equipment. METHODS: A CIABG monitoring system consisting of a sterile, disposable, fiberoptic sensor and a microprocessor-controlled monitor with a self-contained calibration unit and detachable display panel was used. The sensor was inserted through a 20-G radial artery cannula. Light was transmitted from the monitor to the sensor tip where it reacted with fluorescent dyes sensitive to oxygen or hydrogen ions (analytes). The change in the intensity of the photoluminescent radiation caused by the analytes was measured every 20 s and derived blood gas values were displayed. Twenty-nine sensors were evaluated in 29 surgical or intensive care unit patients at one of three institutions (Stanford University Hospital, Evanston Memorial Hospital, and the Palo Alto Veterans Administration Hospital). The duration of study averaged 6 h (5-8 h) in the operating room, and 46 h (7-121 h) in the intensive care unit. A total of 552 values were compared with those obtained at regular intervals and analyzed in the hospital blood gas laboratory. Average bias (mean difference between lab value and CIABG), precision (SD of difference), and drift (change in the bias with time were determined. RESULTS: At arterial oxygen tension (PO2) values of 32-528 mmHg, the average bias was -1% meaning that the average CIABG monitor values were 1% lower than those obtained by conventional equipment. The precision was 15%. At arterial PO2 values of 32-99 mmHg, average bias and precision were -0.3 +/- 8.9 mmHg. At arterial carbon dioxide tension (PCO2) values of 24-54 mmHg, average bias and precision were 1.3 +/- 3.3 mmHg, and at pHa values of 7.23-7.57, average bias and precision were 0.01 +/- 0.04. Observed drift per day was -1.2% for arterial PO2, 0.3 mmHg for arterial PCO2, and 0.01 for pH. Bias and precision for samples compared in two pairs of like-model in vitro blood gas analyzers were 0.4 +/- 4.6% for arterial PO2 over the full range, and 0.4 +/- 3.7 mmHg for values less than 100 mmHg, -0.5 +/- 1.8 mmHg for arterial PCO2, and 0.01 +/- 0.01 for pHa. Although the occasional marked discrepancies between one or more CIABG and in vitro values could sometimes be corrected by flushing the arterial catheter or repositioning the sensor, usually we could not determine the cause of the discrepancy or which values were the more accurate. CONCLUSIONS: Over the range of values and under the clinical conditions studied, CIABG monitoring provides immediate blood gas results and trend information with sufficient agreement with in vitro results to be reliable for decision making in most clinical circumstances. Generally, the differences in the values between the two methods of analysis were the result of the combination of the inherent errors of each method. Additional studies need to be undertaken to evaluate the performance of the CIABG monitor across wider ranges of blood gas values, especially for arterial PO2 values less than 60 mmHg and arterial PCO2 values greater than 50 mmHg.

Adult↗
PubMed1995

Monitoring the administration of neuromuscular blockade in critical care.

The future direction of neuromuscular blockade (NMB) in critical care will be characterized by prudent utilization and quality monitoring. With the potential for persistent paralysis and less than optimal outcomes, this direction makes sense. Prudent utilization can be further defined as exhausting other therapies prior to NMB utilization. When NMB is necessary, the agents should be titrated consistently according to a protocol, using the minimally effective dose to produce the least amount of NMB in order to facilitate patient management. Quality monitoring requires that peripheral nerve stimulator (PNS) monitoring become the standard for monitoring the administration of NMB agents and also that monitoring be accurate. Inherent to prudent utilization and quality monitoring is an adequate knowledge related to all aspects of NMB. The purpose of this article is to provide the necessary knowledge base for practitioners to understand normal and altered neuromuscular junction function, perform accurate PNS monitoring, and titrate NMB therapy according to the individual and desired response.

Critical Care↗
PubMed1981

The effect of transcutaneous Po2 monitoring on the frequency of arterial blood gas analysis in the newborn with respiratory distress.

Nineteen infants with respiratory distress and indwelling arterial lines were monitored with a transcutaneous O2 (PtcO2) monitor for 24 h each. These infants were matched with comparably sick newborns not monitored with PtcO2 and cared for in the intensive care nursery within the previous 18 months. The number of arterial blood gases (ABGs) drawn in each group was examined. Results showed that in all but 1 infant, the patients who had PtcO2 monitoring also had fewer ABGs drawn. The mean number of ABGs in the PtcO2 monitored infants was 12.5 + 2.9 (SD) and the mean number of ABGs in the non-PtcO2 monitored infants was 16.2 + 2.4. The authors conclude that supplementary O2 monitoring of sick infants with PtcO2 reduces the frequency of ABG analysis.

Age Factors↗
PubMed1987

Transcutaneous respiratory electromyographic monitoring.

The integrated diaphragm electromyogram (EMG) signal reflects function from the inspiratory centers to the neuromuscular junction. The feasibility and potential value of transcutaneous diaphragm electromyography (tcEMG) was confirmed in a group of infants using two prototype respiratory EMG monitors. Infants were monitored continuously for periods ranging from hours to days. One hundred were monitored for clinical reasons, looking for disordered respiratory behavior, while 47 were studied for technical/experimental reasons. Reliable measurements of diaphragm EMG activity were obtained, provided fully shielded electrode cables were used. Measurements in 28 ventilated infants and one adult confirmed that, unlike impedance and other non-electrophysiologic measures, tcEMG monitoring is not contaminated by ventilator-induced respiratory movements. The potential value of tcEMG monitoring in ventilated subjects is exemplified by illustrations of: diaphragmatic inactivity from phrenic nerve injury, inadequate central drive, and neuromuscular block; augmented expiratory muscle activity; and progressive increase in inspiratory diaphragmatic activity in the presence of a tension pneumothorax. TcEMG monitoring should prove a worthwhile addition to the available noninvasive respiratory monitoring techniques.

Diaphragm↗
PubMedDate not supplied

Infant monitoring resulting in burns-tissue damage: literature review and case report.

Noninvasive infant monitoring occasionally results in burns and tissue damage. The medical literature now contains 14 isolated reports that were summarized for this review. All 14 victims were less than 24 months of age, and of these 14, two died by electrocution. Burns and tissue damage resulted from infant respiratory monitors (six), pulse oximeters (four), electrocardiographic monitors (two), an anal myoneural junction monitor (one), and a fetal scalp monitor (one). Infant extremities were injured most often (40%), and the trunk was burned somewhat less frequently (23%). Infants were burned in the hospital (57%) only slightly more often than at home (43%). Household burns involved only infant cardiorespiratory monitors. The most common mechanism of injury was the misapplication or improper connection of electrode lead wires (57%). A full one third of infants with burns required a reconstructive surgical procedure, usually a skin graft. Risk factors related to monitor-induced burns and tissue damage have been identified and presented. Injury prevention principles are also outlined.

Burns, Electric↗
PubMed1993

Continuous EEG and evoked potential monitoring in the neuroscience intensive care unit.

As with other methods long used in intensive care units (ICU) and operating rooms (OR), the goal of neuroscience ICU continuous EEG (NICU-CEEG) and evoked potential (NICU-EP) monitoring is to extend our powers of observation to detect abnormalities at a reversible stage. EEG is an appropriate monitoring tool because it is linked to cerebral metabolism, is sensitive to ischemia and hypoxemia, correlates with cerebral topography, detects neuronal dysfunction at a reversible stage, and is the best method for detecting seizure activity. When applied systematically, it can impact medical decision-making in 81% of monitored patients. It is useful in monitoring precarious cerebral perfusion at the bedside, and it has revealed that nonconvulsive seizures, undetectable otherwise, occur in 34% of NICU patients. In convulsive status epilepticus, NICU-CEEG can help avoid undertreatment and overtreatment. In comatose patients, it can provide useful prognostic information as well as detect potentially treatable causes. Traditional impediments to its application are yielding to technological advances and educational efforts. Real-time digitized EEG in particular has been a major advance. Within limits, somatosensory evoked potential monitoring (ICU-SEP) is useful in the prognosis of coma, but it is less helpful in monitoring focal cerebral ischemia. Brainstem auditory evoked potential monitoring has a relatively restricted role in the NICU but is helpful in distinguishing structural from nonstructural causes of coma and can supplement ICU-SEP in predicting outcome.

Brain Damage, Chronic↗
PubMed2001

Facial nerve monitoring in middle ear and mastoid surgery.

HYPOTHESIS: Intraoperative electromyographic facial nerve monitoring, long accepted as the standard of care in surgery for acoustic neuroma and other cerebellopontine angle tumors, may be of aid in middle ear and mastoid surgery. STUDY DESIGN: Retrospective series of 262 cases of middle ear/mastoid surgery in which monitoring was performed by a neurophysiologist. METHODS: Neurophysiological monitoring events were classified as mechanical or electrical. The voltages producing facial nerve stimulation were compiled and compared with observed facial nerve dehiscence. RESULTS: The most common use of monitoring was localization of the facial nerve by electrical stimulation (60%) or identification of mechanically evoked activity (39%). In 57 cases (36%), the first electrical stimulation event evoked a facial nerve response at less than 1 V threshold, indicating little or no bony covering. The minimum stimulation threshold throughout each of these cases was less than 1 V in 88 of the 159 cases (55%) in which stimulation was attempted. In contrast, the facial nerve was visibly dehiscent in only 35 cases (13%). Neurophysiological monitoring confirmed aberrant facial nerve course through the temporal bone in four cases resulting in cancellation of surgical treatment in two cases. Postoperative facial nerve function was preserved in all cases when present preoperatively. CONCLUSIONS: An electrical stimulation threshold of less than 1 V is a more useful criterion of dehiscence than observation under the operating microscope. The absence of monitoring events allows safe dissection. Monitoring can help locate the facial nerve, guide the dissection and drilling, and confirm its integrity, thereby allowing more definitive surgical treatment while preserving neural function.

Adolescent↗
PubMed2001

Hemifacial spasm: intraoperative electromyographic monitoring as a guide for microvascular decompression.

OBJECTIVE: Microvascular decompression is the logical and well-accepted treatment of choice for hemifacial spasm (HFS). In experienced hands, good to excellent results can be obtained. However, sometimes the exact site of the vascular compression is unclear. The aim of this study was to analyze whether intraoperative monitoring by stimulated electromyography of the facial nerve may help to improve the results of vascular decompression for HFS. METHODS: In a series of 74 patients operated for HFS, the impact of intraoperative facial nerve monitoring on the surgical procedure was analyzed by use of the clinical and operative patient records. The role of this type of monitoring, with assessment of the so-called abnormal muscle response, was broken down into four categories: a guiding, a confirming, an indirect confirming, or an inconclusive role. The relationship between abnormal muscle response monitoring results and final surgical outcome was analyzed. RESULTS: The overall cure rate was 87.8%, including patients who had previously undergone unsuccessful operations. Complications were minor, and hearing impairment was found in 2.7% of patients. A guiding role of intraoperative monitoring was apparent in 33.8% of patients, and a confirming role was demonstrated in 52.7% of patients, which resulted in a positive contribution of approximately 87% for intraoperative facial monitoring in microvascular decompression for HFS. In patients defined as guiding cases, the cure rate was 92%. CONCLUSION: This study demonstrates the applicability and usefulness of intraoperative facial nerve monitoring in microvascular decompression operations for HFS.

Adult↗