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Results for “Monitoring, Intraoperative”

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At least 541 records · Page 30Linked to original sources

PubMed1992

Hepatic venous hemoglobin oxygen saturation predicts liver dysfunction after hepatectomy.

A fiberoptic flow-directed catheter inserted into the hepatic vein continuously measures hepatic venous oxygen hemoglobin saturation (ShvO2). This study determined whether intraoperatively measured ShvO2 could predict postoperative serum activities of aminotransferases and patient outcome in 83 patients undergoing hepatectomy. The duration of intraoperative ShvO2 less than or equal to 10, 20, 30, 40, and 50% was calculated in each case. Significant increases in postoperative serum aminotransferases were associated with more than 1, 11, 31, 51, and 181 min of duration of ShvO2 less than or equal to 10, 20, 30, 40, and 50%, respectively. The incidence of postoperative liver failure significantly increased when the duration of ShvO2 less than or equal to 20, 30, and 40% exceeded 11, 31, and 51 min, respectively. The mortality from liver failure was significantly higher when the duration of ShvO2 less than or equal to 30 and 40% exceeded 31 and 51 min, respectively. Therefore, intraoperative monitoring of ShvO2 may predict not only the increase in postoperative serum aminotransferases but also patient outcome in terms of postoperative liver failure after hepatectomy.

Adult↗

PubMed1995

Improved amplitude of myogenic motor evoked responses after paired transcranial electrical stimulation during sufentanil/nitrous oxide anesthesia.

BACKGROUND: Measurement of motor evoked responses to transcranial stimulation (tc-MER) is a technique for intraoperative monitoring of motor pathways in the brain and spinal cord. However, clinical application of tc-MER monitoring is hampered because most anesthetic techniques severely depress the amplitude of motor evoked responses. Because paired electrical stimuli increase tc-MER responses in awake subjects, we examined their effects in anesthetized patients undergoing surgery. METHODS. Eleven patients whose neurologic condition was normal and who were undergoing spinal or aortic surgery were anesthetized with sufentanil-N20-ketamine. Partial neuromuscular blockade (single-twitch height 25% of baseline) was maintained with vecuronium. Single and paired electrical stimuli were delivered to the scalp, and compound action potentials were recorded from the tibialis anterior muscle. The amplitude and latency of the tc-MERs were measured as the interval between paired stimuli was varied between 0 (single stimulus) and 10 ms. All recordings were completed before spinal manipulation or aortic clamping. RESULTS: Median amplitude of the tc-MER after a single stimulus was 106 microV (10th-90th percentiles: 23-1,042 microV), and the latency to onset was 33.2 +/- 1.4 ms (SD). With paired stimuli (interstimulus interval 2-3 ms), tc-MER amplitudes increased to 285 (79-1,605) microV, or 269% of the single-pulse response (P < 0.01). Reproducibility of individual responses increased with paired stimulation. Onset latency decreased to 31.4 +/- 3.2 ms (P < 0.05). Maximum amplitude augmentation was observed with interstimulus intervals between 2 and 5 ms and in patients with low-amplitude responses after single-pulse stimulation. CONCLUSIONS: Application of paired transcranial electrical stimuli increases amplitudes and reproducibility of tc-MERs during anesthetic-induced depression of the motor system. The effect may represent temporal summation of stimulation at cortical or spinal sites. The results of this study warrant further clinical evaluation of paired transcranial stimulation.

Action Potentials↗

PubMedDate not supplied

Gastric intramucosal pH during lower body circulatory arrest under open distal anastomosis with selective cerebral perfusion in aortic arch repair.

Selective cerebral perfusion (SCP) and open distal anastomosis (OD) with hypothermia has been used as a popular means for circulatory assistance in aortic arch surgery. Although SCP has become accepted for brain protection, the influence of OD accompanying circulatory arrest on lower body ischemia is not known. We studied gastric tonometry (gastric intramucosal pH [pHi]) to estimate splanchnic ischemia during OD, and its relationship to postoperative organ function. In five patients (pts) (range, 65-78 years; mean, 71 years; group OD) who underwent arch replacement using SCP and OD with moderate hypothermia (25 degrees C) during the period from March to August of 1999, pHi was measured precardiopulmonary bypass (pre-CPB), 30 min of CPB (CPB30), 10 min after OD (OD10), at end of CPB, and post-CPB. Eight pts (range, 52-78 years; mean; 66 years) who underwent standard CPB (33 degrees C) during the same period (coronary artery bypass surgery in six and valve surgery in two) served as controls (group C). In group OD, pHi was significantly decreased at OD10 (7.35 +/- 0.03 at CPB30 vs. 7.23 +/- 0.07 at OD10, p < 0.05) but recovered by the end of CPB (7.32 +/- 0.02). Creatinine clearance on the first postoperative day (1POD) was significantly (p < 0.05) lower in group OD (82 +/- 40 ml/min) than in group C (126 +/- 25 ml/min), although there was no significant difference in preoperative values between the two groups. The pHi at OD10 did not correlate with the duration of OD (range, 30-47 min; mean, 38 min), whereas pHi at OD10 significantly correlated with BUN (r = -0.973, p = 0.0054), Cr(r = -0.977, p = 0.0043), and CCr (r = 0.908, p = 0.0328) on 1POD. One patient in group OD developed paraplegia and renal failure postoperatively. His pHi at OD10 was severely decreased to 7.11. These results suggest that intraoperative monitoring of pHi may be useful for the evaluation of visceral organ ischemia during OD in arch replacement and may contribute to improved technique for circulatory assistance in aortic surgery.

Aged↗

PubMed1995

Intraoperative end-tidal carbon dioxide values and derived calculations correlated with outcome: prognosis and capnography.

OBJECTIVE: To determine how much information concerning resuscitation and outcome is provided by the end-tidal CO2 and derived variables obtained during surgery. DESIGN: Retrospective chart review. SETTING: Emergency hospital operating room. PATIENTS: One hundred critically ill or injured patients requiring major surgery and having a mortality rate of 41%. INTERVENTIONS: Standard intraoperative monitoring, including continuous capnography, plus arterial blood gas analyses every 1 to 1.5 hrs during surgery. MEASUREMENTS AND MAIN RESULTS: There was only a fair correlation between the PaCO2 and end-tidal CO2 (r2 = .14). The mortality rates in these patients were highest in those patients who had the lowest end-tidal CO2 values, the highest arterial to end-tidal CO2 differences, and the highest estimated alveolar deadspace fraction. A persistent end-tidal CO2 of < or = 28 torr (< or = 3.8 kPa) was associated with a mortality rate of 55% (vs. 17% in those patients with a higher end-tidal CO2). The mortality rate was also increased in patients with a persistent arterial to end-tidal CO2 difference of > or = 8 torr (> or = 1.1 kPa) (58% vs. 23%). CONCLUSIONS: End-tidal CO2 and derived values should be monitored closely in critically ill or injured patients. Efforts should be made--by increasing cardiac output and core temperature and by adjusting ventilation as needed--to maintain the end-tidal CO2 at > or = 29 torr (> or = 3.9 kPa) and the arterial to end-tidal CO2 difference at < or = 7 torr (< or = 1.0 kPa).

Adult↗

PubMed2002

Mechanisms of intraoperative brainstem auditory evoked potential changes.

Brainstem auditory evoked potential (BAEP) changes during intraoperative monitoring may reflect damage to or potentially reversible dysfunction of the ear, the eighth nerve, or the brainstem auditory pathways up to the level of the mesencephalon. They may also be caused by other physiologic mechanisms such as anesthesia, hypothermia, and acoustic masking from drilling noise, or they may result from technical factors that prevent proper stimulus delivery or recording of an evoked potential that is actually present. Cochlear ischemia or infarction resulting from compromise of the internal auditory artery and inner ear damage during temporal bone drilling will affect all BAEP components, including wave I. Direct mechanical or thermal trauma to the eighth nerve will delay, attenuate, and possibly eliminate waves III and V, but wave I, which is generated at the cochlear end of the eighth nerve, may be preserved. During scraping of tumor off the eighth nerve, force applied in an ear-toward-brainstem direction can avulse the fragile fibers of the distal eighth nerve at the area cribrosa. Prolonging the I-to-III interpeak interval during retraction of the cerebellum and brainstem reflects stretching of the eighth nerve, and is often reversible. Vasospasm within the eighth nerve can cause similar, potentially reversible BAEP changes. Damage to the brainstem auditory pathways at or below the level of the mesencephalon will delay and attenuate or eliminate wave V. Wave III is affected similarly if the damage is at or caudal to the region of the superior olivary complex. These BAEP changes may reflect direct mechanical or thermal damage to the brainstem, brainstem compression, or ischemia or infarction resulting from vascular compromise. During BAEP monitoring, examination of the pattern of BAEP changes, analysis of their correlation with surgical maneuvers, and investigation for possible contributory technical factors can help to determine the cause of the BAEP changes and provide the appropriate information to the rest of the surgical team.

Anesthesia↗

PubMed1996

Transcranial high-frequency repetitive electrical stimulation for recording myogenic motor evoked potentials with the patient under general anesthesia.

OBJECTIVE: To demonstrate the feasibility of transcranial high-frequency electrical stimulation with the patient under general anesthesia with propofol and alfentanil. This method may be a useful tool for intraoperative monitoring of the motor pathways during cerebral and spinal operations. METHODS: A short train from one to eight monopolar anodal electrical pulses was applied transcranially to the motor cortex with a frequency from 100 to 500 Hz in 10 patients. Myogenic motor evoked potentials (MEPs) were recorded from forearm flexor muscles, thenar, and hypothenar. Amplitude and latency of MEPs were evaluated after different stimulation parameters. This combination of anesthetic and transcranial stimulation technique allows recording of myogenic MEPs during general anesthesia, which was found not to be possible with single pulse transcranial stimulation. RESULTS: To elicit myogenic MEPs from the target muscles, stimulation had to be applied within the following parameters: minimum threshold intensity was 60 mA for forearm flexor and thenar and 80 mA for hypothenar; minimum number of pulses was two for forearm flexor muscles and thenar and three for hypothenar; minimum stimulation frequency was 200 Hz for thenar and hypothenar and 100 Hz for forearm flexor muscles. CONCLUSION: Transcranial high-frequency repetitive electrical stimulation seems to be a new method for monitoring the motor tract. With this method, it is possible to monitor the motor function without interfering with the surgical team or with the surgical treatment of infratentorial and spinal lesions. Monitoring of relaxation is necessary to compare the amplitude of MEPs.

Adolescent↗

PubMed1999

Comparative study of propofol and midazolam effects on somatosensory evoked potentials during surgical treatment of scoliosis.

OBJECTIVE: Studies of the effects on lower-limb cortical somatosensory evoked potentials (CSEP) during total intravenous anesthesia are sparse for propofol and are lacking for midazolam. This study was designed to compare the effects of propofol and midazolam on CSEP under total intravenous anesthesia during intraoperative monitoring for surgical treatment of scoliosis. METHODS: CSEPs were recorded in two groups of 15 patients during posterior instrumentation for treatment of idiopathic scoliosis. The anesthesia used the combination of atracurium, alfentanil, and an hypnotic agent (propofol for Group I or midazolam for Group II). The main characteristics of the CSEPs (P40 latency and N34-P40 and P40-N50 amplitudes) were recorded using ankle posterior tibial nerve stimulation. The CSEPs were recorded before induction, 10, 70, 100, 130, and 160 minutes after induction, and before the wake-up test. The statistical analysis involved analysis of variance for repeated measures. Both groups were homogeneous before induction. RESULTS: Neither CSEP deterioration during risk-associated surgical procedures nor postoperative clinical abnormalities were observed. Both propofol and midazolam induced increases in P40 latencies, with the increases being greater and more regular for the propofol-treated group. The amplitude values changed with time for both groups, decreasing mainly after induction; in the midazolam-treated group, the amplitudes were smaller but more stable. Propofol modified the morphological characteristics of the response by decreasing the late P60 component amplitude; the W-shaped CSEP morphological pattern was maintained with midazolam. CONCLUSION: This study demonstrates the appropriate use of either propofol or midazolam in scoliosis monitoring. Preoperative small-amplitude CSEPs might favor the use of propofol anesthesia.

Adolescent↗

PubMed1993

Incomplete spinal cord evoked injury potential in man.

Intraoperative monitoring of spinal cord evoked potentials (SCEP) evoked by tibial nerve stimulation was performed in six patients who underwent junctional coagulation lesion of the dorsal root entry zone for relief of intractable pain. The pain was secondary to complete brachial plexus avulsion. Normal spinal cord evoked potentials showed an initial positive wave and two negative waves, then a group of high frequency conducted waves. On the avulsion side, incomplete spinal cord evoked injury potentials were recorded in all cases and in one on the normal side also. The incomplete spinal cord evoked injury potential consisted of a high-amplitude positive wave with a sharp rising phase and slower falling phase that led to a long lasting, low-amplitude, negative deflection. Several high-frequency components were superimposed onto the monophasic positive wave. The duration of these superimposed components was approximately the same as the duration of the normal spinal cord evoked potentials, but the incomplete spinal cord evoked injury potentials were longer than normal spinal cord evoked potentials for the negative afterwave. Incomplete spinal cord evoked injury potential amplitude was 3-11 times higher than the normal spinal cord evoked potentials. Our results suggest two possible sources of incomplete spinal cord evoked injury potential: the chronic subclinical spinal cord injury produced by the avulsion and the effect of subpial placement of the recording electrodes.

Adult↗

PubMed1993

Idiopathic scoliosis in children.

Idiopathic scoliosis is a common developmental spinal deformity that usually begins to develop from midchildhood to early adolescence. Although its etiology remains unknown, current research focuses on growth and dysfunction of the central nervous system. Radiography remains the standard of documentation of curve progression. Orthosis and surgical treatment are the only two methods that can alter the condition's natural history. Improved surgical techniques include the use of stronger fixation systems that attach dual rods to the posterior spinal elements at multiple vertebral locations. Improved techniques for blood loss control and replacement and for intraoperative monitoring of spinal cord function have increased the safety of surgical treatment.

Blood Loss, Surgical↗

PubMed1999

Influence of fentanyl, alfentanil, and sufentanil on motor evoked potentials.

The effects of the opioids fentanyl, alfentanil, and sufentanil on motor pathways were studied in a total of 30 rabbits. Compound muscle action potentials (CMAP) were recorded from the extensor muscles of the upper extremity as well as evoked spinal cord potentials (ESCP) from the thoracic epidural space in response to electrical stimulation of the motor cortex. After establishing stable baseline values, an equipotent intravenous bolus of one of the three opioids was applied that abolished reflex motor response to noxious stimulation. Motor evoked potentials (MEP) were recorded from the time of bolus administration until recovery of MEP amplitudes and latencies. Afterwards, the opioids were administered continuously with cumulative dosage up to total absence of motor evoked response. Our results show a dose-dependent suppression of the CMAP: When reflex movement to noxious stimulation was extinguished, we found a significant (P < .001) reduction of the amplitudes to 34+/-18% (mean +/- SD) in the fentanyl group, to 43+/-24% in the alfentanil group, and to 53+/-20% of baseline values in the sufentanil group. Increasing opioid plasma levels were associated with complete extinction of the CMAP. We hypothesize that the descending volleys within motor pathways are mainly inhibited at a spinal level, because ESCP, particularly the number of spinal I-waves, are not severely affected even when CMAP are completely suppressed. In conclusion, intraoperative monitoring of descending pathways by means of MEP during anesthesia with opioids is feasible at anesthetic plasma concentrations maintaining a surgical level of analgesia. Even with high opioid plasma levels, a valid MEP monitoring could be performed evaluating neural activity of spinal MEP.

Action Potentials↗

PubMed2005

QEEG changes during carotid clamping in carotid endarterectomy: spectral edge frequency parameters and relative band power parameters.

Intraoperative monitoring is needed to identify accurately those patients in need of a shunt during carotid endarterectomy. EEG can be used for this purpose, but there is no consensus on the variables to use. Using a database consisting of 149 EEGs recorded from patients during carotid endarterectomy under isoflurane (n=61) or propofol (n=88) anesthesia and who did or did not receive a shunt, the authors investigated which of 16 derivations (common reference, Cz) and 12 parameters (relative and absolute powers and spectral edge frequencies [SEFs]) singly or in combination could best distinguish between the shunt and the nonshunt groups for the two anesthesia regimens. Receiver operating characteristic curves were used to select derivation/parameter combinations for three types of trend computation: (1) values of relative powers and SEFs during clamping (C) only, (2) clamp minus preclamp (baseline) differences (C-B), and (3) C-B differences in absolute logarithmic power (DeltalogP). For both anesthesia regimens, C-B computation distinguished best between the shunt and nonshunt groups. For isoflurane anesthesia, SEF parameters were the best, and for propofol anesthesia the relative power parameters. Discriminant analysis, in which additional derivation/parameter combinations were added, increased the discriminative power of the DeltalogP computation but not of the C or C-B computations. For isoflurane anesthesia, SEF 90% was the best single parameter for distinguishing between patients who did and did not need a shunt and the four best derivations were F3-Cz, P4-Cz, C4-Cz, and F7-Cz. For the propofol anesthesia, the relative power (C or C-B computations) of the delta band was the best and the four best derivations were F8-Cz, T4-Cz, C4-Cz, and F4-Cz.

Anesthetics, Inhalation↗

PubMed1996

Current status of tumescent liposuction in the United States. National survey results.

BACKGROUND: Tumescent liposuction is an extremely safe method of liposuction that can be performed entirely under local anesthesia. OBJECTIVE: To determine evolving trends in the current practice of tumescent liposuction in 15,336 patients treated by 66 dermatologic surgeons. METHODS: A survey questionnaire was sent to 1,778 Fellows of the American Society for Dermatologic Surgery in February 1994. The comprehensive questionnaire requested information on the number of patients treated with tumescent liposuction, complications, and various practice issues. RESULTS: Sixty-six dermatologic surgeons provided data on 15,336 patients; 44,014 body areas were treated. The complications that developed were infrequent and minor and have been reported previously. The average amount of fat removed per patient was 1,276 cc. An average of 33 cc of blood was lost per patient per procedure. Cannulas of 4.0 mm or less in diameter were commonly used. The abdomen and outer thighs were the most common areas treated in women. The flanks/love handles and abdomen were the most common areas treated in men. Intraoperative monitoring of vital signs was common. CONCLUSIONS: Tumescent liposuction is an evolving technique that has virtually eliminated blood transfusions and the major complications of liposuction under general anesthesia. Large amounts of fat can be removed using small diameter cannulas. The fat can be safely removed with a minimum risk of minor complications.

Abdomen↗

PubMed1999

Mechanically elicited nerve root discharge: mechanical irritation and waveform.

OBJECTIVE: Intraoperative monitoring is very important for protecting nerve roots during lumbar surgery for spinal degeneration. Our objective was to evaluate the correlation between the type of mechanical irritation and waveform by mechanically elicited EMGs during the surgery. METHOD: Mechanically elicited EMGs were recorded bilaterally on muscle groups innervated by the lumbar nerve roots in the area of surgery in 24 consecutive patients with lumbar spinal degenerative disease. RESULTS: It was confirmed that surgical irritation produced 3 types of waveforms as discharges from nerve roots; short, waning and continuous discharges. Each waveform was easily elicited mechanically and was sensitively related to the type and strength of mechanical stimulation. CONCLUSION: It was indicated that the mechanical irritation on the root could elicit the nerve root discharge with no post-operative nerve root deficit. It may be useful to monitor the mechanically elicited EMGs during the surgery for spinal degeneration.

Adult↗

PubMed1997

Ultrasonic bruits in the circle of Willis due to a large nonfunctioning pituitary adenoma.

In a man with a histologically verified non-functioning pituitary adenoma with suprasellar extension, Doppler signals resembled those associated with bruits (ultrasonic bruits). These signals were detected in the anterior circulation of Willis both preoperatively and intraoperatively. The large tumor was resected subtotally via a right orbitozygomatic approach. The use of microvascular sonography for intraoperative monitoring can provide information on the potential cerebrovascular complications of surgery. No previous studies on the presence of ultrasonic bruits associated with pituitary adenomas have been reported. The clinical implications for the surgical treatment of pituitary adenomas are discussed.

Adenoma, Chromophobe↗

PubMed1994

A modified technique for nerve-sparing retroperitoneal lymph node dissection in stage II nonseminomatous germ cell tumors using intraoperative measurement of bladder neck pressure alterations following sympathetic nerve fiber electrostimulation.

We present a simplified method for nerve-sparing retroperitoneal lymph node dissection in patients with nonseminomatous testicular cancer. The sympathetic fibers involved in antegrade ejaculation are identified by intraoperative electrostimulation, resulting in an increase of bladder neck closure pressure. This increase is demonstrated by intraoperative monitoring of both the intravesical pressure and the pressure within the bladder neck by a two-channel microtip measuring catheter. 4 patients with stage I and 6 patients with stage II nonseminomatous testicular cancer were operated on with this modified technique. Ejaculation was preserved in all cases. Semen volume ranged from 2.2 to 4.0 ml. Sperm cell count ranged from 2 to 22 x 10(6)/ml with 20-50% motile spermatozoa, except for 2 of the 3 patients who initially presented with preoperative azoospermia following chemotherapy. In 1 of these 3 patients, postoperative semen analyses revealed a recovery of germ cell function demonstrated by oligoasthenozoospermia.

Adrenergic Fibers↗

PubMed1992

Clinical evaluation of a rapid parathyroid hormone assay.

Modifications to the incubation conditions of radioimmunoradiometric assay for whole molecule parathyroid hormone (PTH) permit accurate quantification of the hormone in the peripheral circulation within 1 h of sampling. We assessed the assay intraoperatively in 75 patients undergoing parathyroidectomy. Serum PTH concentration declined to less than 20% of its pre-operative value within 20 min of the successful completion of surgery provided that renal function was normal. In patients with chronic renal failure the rate of decline in serum PTH concentration after parathyroidectomy was slower in some cases. In four cases of unsuccessful parathyroidectomy, serum PTH concentration remained above 60% of its preoperative value. Intraoperative monitoring during parathyroidectomy using this rapid PTH assay offers considerable advantages to the surgeon over frozen section.

Adult↗

PubMed1993

Modification of cortical stimulation for motor evoked potentials under general anesthesia: technical description.

This pilot study presents a possible modification of direct cortical electrical stimulation technique for the recording of motor evoked potentials under general anesthesia. The exposed primary motor cortex was stimulated by a short train of anodal rectangular pulses at high frequency (300-500 Hz), while the compound muscle action potentials were recorded from the forearm and hand muscles. When compared with the traditional way of eliciting movement of the extremities by applying a train of pulses at lower frequency (50-60 Hz), muscle responses were obtainable at an intensity of much lower charge. It is suggested that this stimulation achieves a repetitive activation of the corticomotoneuronal tract. Responses could be continuously recorded throughout surgery and seemed to respond to surgical manipulation affecting the motor pathways. This technique seems to be applicable for intraoperative monitoring of motor pathways but requires further optimization of stimulation and recording parameters before wider clinical applications are possible.

Anesthesia, General↗

PubMed1993

The trigeminal evoked potential: Part I. Long-latency responses in awake or anesthetized subjects.

Trigeminal evoked potentials have been elicited with differing methodologies that render responses almost as numerous as the number of laboratories reporting them. Forty-six trigeminal nerves were studied to investigate trigeminal evoked potentials in 20 awake, normal subjects and 20 patients undergoing surgery with general anesthesia. A comparison was made between different methods of surface stimulation and subdermal stimulation. It was concluded that these techniques had no practical use in intraoperative monitoring.

Adolescent↗