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PubMed1992

Monitoring for myocardial ischemia during noncardiac surgery. A technology assessment of transesophageal echocardiography and 12-lead electrocardiography. The Study of Perioperative Ischemia Research Group.

OBJECTIVE: Transesophageal echocardiography (TEE) and 12-lead electrocardiography (ECG) are sophisticated techniques that are increasingly being used to monitor for myocardial ischemia during noncardiac surgery. We examined whether the routine use of these techniques has incremental clinical value in identifying patients at high risk for perioperative ischemic outcomes when compared with preoperative clinical data and intraoperative monitoring using continuous two-lead bipolar ECG. DESIGN: Cohort study. SETTING: Veterans Affairs medical center. PATIENTS: A total of 332 men undergoing noncardiac surgery who had or were at high risk for coronary artery disease. INTERVENTIONS: TEE, 12-lead ECG, and two-lead ECG were performed continuously during noncardiac surgery (47% vascular, 53% nonvascular). Monitoring results were not available to anesthesiologists or surgeons, and data were blindly analyzed after surgery. MAIN OUTCOME MEASURE: Perioperative ischemic outcomes (cardiac death, nonfatal myocardial infarction, unstable angina). RESULTS: In a subset of 285 patients who were adequately studied by all three techniques, 111 patients (39%) were identified as having intraoperative myocardial ischemia (by one or more monitoring techniques). By univariate analysis, intraoperative ischemia was associated with all perioperative cardiac outcomes, including ischemic outcomes, congestive heart failure, and ventricular tachycardia (P less than or equal to .02 for each of the three monitoring techniques). However, when monitoring results for TEE and 12-lead ECG were added to a multivariate model that included preoperative clinical data and continuous two-lead ECG results, the incremental value of TEE was small (odds ratio, 2.6; 95% confidence interval [CI], 1.2 to 5.7; P = .02) and that of 12-lead ECG was not significant (odds ratio, 1.5; 95% CI, 0.6 to 3.8). Furthermore, when the multivariate analysis was repeated with only ischemic outcomes, neither TEE nor 12-lead ECG retained significant associations (odds ratio, 2.2; 95% CI, 0.5 to 9.4, and odds ratio, 1.1; 95% CI, 0.2 to 6.1, respectively). CONCLUSION: When compared with preoperative clinical data and intraoperative monitoring using two-lead ECG, routine monitoring for myocardial ischemia with TEE or 12-lead ECG during noncardiac surgery has little incremental clinical value in identifying patients at high risk for perioperative ischemic outcomes.

Aged↗
PubMed2005

Hemodynamic changes during laparoscopic gastric bypass procedures.

HYPOTHESIS: Significant detrimental intra-operative hemodynamic and respiratory changes occur in the morbidly obese during laparoscopic gastric bypass. DESIGN: Case series. SETTING: Tertiary care university hospital. PATIENTS: Thirteen patients, 10 women and 3 men, undergoing uncomplicated laparoscopic gastric bypass for morbid obesity. INTERVENTIONS: Using a pulmonary artery catheter and an arterial line, we intraoperatively monitored hemodynamic and respiratory parameters. Parameter values were recorded at set points of the procedure, and the changes were statistically analyzed. RESULTS: Significant hemodynamic and respiratory changes, mostly unfavorable, occur in the morbidly obese when creating the pneumoperitoneum in preparation for laparoscopic gastric bypass. The hemodynamic changes are attenuated when the patient is placed in the reverse Trendelenburg position and almost completely corrected when the abdomen is deflated at the completion of the procedure. The respiratory changes are more persistent. CONCLUSIONS: Laparoscopic gastric bypass surgery for morbid obesity leads to a number of predominantly detrimental, if temporary, respiratory and hemodynamic changes, which are most pronounced at the time of creation of the pneumoperitoneum. In the presence of significant cardiopulmonary comorbidities, the use of invasive intra-operative hemodynamic monitoring of the morbidly obese undergoing laparoscopic gastric bypass appears therefore justified.

Adult↗
PubMed1986

Intraoperative spinal somatosensory evoked potential monitoring.

The relationship of intraoperative monitoring of spinal cord somatosensory evoked potentials and postoperative deficit in 220 cases (121 with scoliosis, 41 with neoplasms, and 58 others) is reported. Bilateral posterior tibial nerve stimulation was used in 181 cases and unilateral median nerve stimulation in 39. Spinal cord (interspinous ligament needles), subcortical (neck surface), and cortical (scalp surface) SEP's were monitored. Seven patients had worsening of neurological function after surgery, three of whom demonstrated significant changes in SEP's monitored. In an additional four cases, there was more than a 50% decrease in amplitude of subcortical/cortical SEP's during monitoring, but no change in neurological status postoperatively. Combined monitoring of spinal cord, subcortical, and cortical SEP's enhanced the certainty of detecting spinal cord dysfunction even though there was a significant number of false-negative and false-positive results. A marked change in the SEP's indicated a high chance of developing a neurological deficit (three or 43% of seven cases), and if there was no change the chance of any neurological postoperative deficit was extremely low (four or 1.87% of 213 cases). These data justify the use of intraoperative SEP monitoring.

Adolescent↗
PubMed1992

Facial nerve outcome in acoustic neuroma surgery.

Patients consider facial paralysis the most concerning sequelae following acoustic tumor resection. Surgical and anesthetic refinements have lowered operative mortality to allow the surgeon to focus on preserving facial nerve function. Tumor size, microsurgical technique, and intraoperative monitoring are the most important factors that define the risk of postoperative facial paralysis. A protocol for uniform surgical reporting is proposed.

Facial Nerve↗
PubMed1998

Anesthetic effects on electrophysiologic recordings.

With the increased use of intraoperative monitoring of the central nervous system (CNS) has come a need for better understanding of the effects of anesthetic agents on intraoperative recordings. The commonly used anesthetic agents and their effects on intraoperative electroencephalography (EEG) and evoked potentials (EP) are discussed. Halogenated inhalational anesthetics produce dose-related reduction in EEG amplitude and frequency after an initial activation. They also produce dose-related decreases in amplitude and increases in latency of sensory evoked potentials (SEP) that are most marked in cortically generated components. Subcortical, spinal, and peripheral evoked responses are less affected. Responses in the motor pathways are recordable in the epidural space; however, the relative contributions of sensory and motor tracts may be changed when both are present. Muscle responses are easily suppressed after spinal and motor cortex stimulation, probably by anesthetic effect at the anterior horn cells of the spinal cord. Intravenous analgesic agents (opioids, ketamine) are associated with less marked changes in EEG and evoked responses, with some increases in amplitude of cortically generated SEP caused by ketamine. Intravenous sedative-hypnotic drugs (droperidol, barbiturates, benzodiazepines, etomidate, propofol) produce dose-related depression of the EEG after initial activation and dose-related depression of evoked responses to a lesser extent than do the inhalation agents. Etomidate is associated with amplitude enhancement of EEG and cortically generated SEP. Muscle relaxants have minimal effect on the EEG and SEP. Their use, however, may alter muscle recordings from motor tract stimulation. These effects and their relevance to the choice of agents for specific monitoring techniques are discussed.

Anesthesia, General↗
PubMed1990

Neurophysiologic monitoring during surgery of peripheral and cranial nerves, and in selective dorsal rhizotomy.

Physiologic monitoring may warn of impending neural damage and intraoperative assessment may provide critical information used to direct the surgical procedure itself. Intraoperative techniques utilize methods modified from the diagnostic neurophysiologic laboratory. Simultaneous multimodality recording of different signal sources is of particular value for several types of procedures. Intraoperative studies must be tailored to each patient's clinical condition and to the specific surgical risks. Since studies have supported the benefits of intraoperative monitoring for peripheral nerve and cranial nerve surgery, monitoring is not likely to be subjected to the rigors of a randomized controlled study for these procedures.

Action Potentials↗
PubMed1996

Is transcranial Doppler effective in avoiding the hazards of carotid surgery?

The middle cerebral artery flow velocities were measured to test the hypothesis that transcranial Doppler is a useful technique for intraoperative monitoring in 50 consecutive carotid endarterectomies which were performed under local anaesthesia. The patients' neurological status was continuously monitored. The peak middle cerebral artery velocities were measured before clamping, during clamping and after restoration of flow, and again 24 h and 4 weeks later. Clamping produced a decrease in the velocity of the middle cerebral artery, from 97 to 45 cm/s (P < 0.001). Neurological manifestations occurred in eight patients; one patient lost consciousness, and seven experienced transient focal deficits during the procedure. Another three (6%) developed minor strokes postoperatively. The velocity changes were similar in those who developed complications to those who did not. These results do not support the view that transcranial Doppler monitoring is helpful in deciding whether to use a shunt during carotid endarterectomy. Further data are needed to evaluate the importance of transcranial Doppler monitoring during carotid surgery.

Adult↗
PubMed2001

Venous air embolism during endoscopic strip craniectomy for repair of craniosynostosis in infants.

BACKGROUND: Various studies have reported an incidence of venous air embolism (VAE) as high as 82.6% during surgical procedures for craniosynostosis. There has been an increase in the use of minimally invasive, endoseopie surgical procedures, including applications for endoscopic strip craniectomy. The current study prospectively evaluated the incidence of VAF during endoscopic strip craniectomy. METHODS: Continuous, intraoperative monitoring for VAE was performed using precordial Doppler monitoring. A recording was made of the Doppler tones and later reviewed to verify its accuracy. RESULTS: The cohort for the study included 50 consecutive neonates and infants ranging in age from 3.5 to 36 weeks and ranging in weight from 3 to 9 kg. Surgical time varied from 31 to 95 min for a total of 2,701 mm of operating time, during which precordial Doppler tones were auscultated. In 46 patients, there was no evidence of VAE. In four patients, there was a single episode of VAE. Two of the episodes of VAE were grade I (change in Doppler tones), and two were grade H (change in Doppler tones and decrease in end-tidal carbon dioxide). No grade III (decrease in systolic blood pressure by 20% from baseline) VAF was noted. CONCLUSION: In addition to previously reported benefits of decreased blood loss, decreased surgical time, and improved postoperative recovery time, the authors noted a low incidence of VAF during endoscopic strip craniectomy in neonates and infants.

Craniosynostoses↗
PubMed1997

[Transtracheal monitoring of the recurrent laryngeal nerve. Prototype of a new tube].

A new sensing device for the continuous intraoperative monitoring of the recurrent laryngeal nerve is presented. It is based on a double ballooned endotracheal tube including stimulating and tracing electrodes. The system is characterised by three advantages: 1) it is atraumatic, 2) it is operating completely outside the operating field (extraterritorially), 3) nerve function is being monitored continuously from the time of intubation to the time of extubation. The presented system has been evaluated in piglets. First results in humans will be available shortly.

Animals↗
PubMedDate not supplied

[Anesthesiological problems in the obese patient. Clinical experience in the treatment of 54 cases].

Obesity its complications and its surgical treatment is important for the anaesthesiologist. The pathophysiological and clinical consequences of obesity involve mainly respiratory, cardiovascular and metabolic functions so that the anaesthesia and postoperative care may affect surgical outcome of these patients. The preoperative, the anesthetic management and the postoperative complications of 54 grossly obese patients undergoing weight-reducing abdominal surgery (bilio-pancreatic diversion) have been studied. According to the Authors' experience, careful preoperative evaluation, intraoperative monitoring, postoperative intensive care, are enough to reduce the haemodynamic, respiratory and metabolic complications.

Adult↗
PubMed1996

Temporary loss of intraoperative motor-evoked potential and permanent loss of somatosensory-evoked potentials associated with a postoperative sensory deficit.

We describe a case of the temporary loss of right popliteal fossa intraoperative neurogenic motor-evoked potential and the permanent loss of right median and ulnar somatosensory-evoked potentials (SSEPs) with retention of posterior tibial (SSEPs) during intramedullary spinal cord surgery in a 28-year-old man. Postoperatively, the patient had preserved motor function in all extremities and loss of proprioception, two-point discrimination, and vibration in his right upper extremity. The complementary and beneficial use of intraoperative monitoring of both motor-evoked potentials and SSEPs during spinal cord surgery is discussed.

Adult↗
PubMed1997

Influence of nitrous oxide on motor-evoked potentials.

STUDY DESIGN: Rabbits were used as an experimental model in the study of motor-evoked potentials. OBJECTIVES: To evaluate the effect of nitrous oxide on motor-evoked potentials while monitoring direct muscle and spinal cord responses. SUMMARY OF BACKGROUND DATA: Motor-evoked potential monitoring provides a promising tool for intraoperative assessment of descending pathways function. However, to date, this technique is still at an experimental stage, since its routine use is mainly limited because of intraoperative recording difficulties caused by the influence of anesthesia. METHODS: Eight male rabbits weighing between 3000 g and 3500 g were studied. Motor-evoked potentials were recorded from the extremity muscles and from the epidural space of the thoracic cord in response to electrical stimulation of the motor cortex at baseline conditions and at increasing nitrous oxide concentrations (10-70 vol%). RESULTS: The authors found a major suppressive effect of high nitrous oxide concentrations on the electromyographic responses. With 50 vol% nitrous oxide, electromyographic amplitudes were suppressed to 46% (fore leg) and 14% (hind leg) of the baseline values, whereas latencies did not change significantly. In contrast to muscular activity, spinal evoked responses representing neural activity were not affected by any concentration of nitrous oxide. CONCLUSIONS: Intraoperative monitoring of descending pathways by means of motor-evoked potentials during anesthesia of the rabbits based on nitrous oxide is feasible when neural activity is evaluated. Higher doses of nitrous oxide, however, are not compatible with recording of muscular activity.

Anesthetics, Inhalation↗
PubMed2004

Continuous laryngoscopic vocal cord monitoring for vascular malformation surgery in the medulla oblongata: technical note.

OBJECTIVE: Resection of lesions located in the medulla oblongata may result in significant morbidity. The most lethal complications are swallowing disturbances, which can lead to aspiration pneumonia. To prevent this problem, the lower cranial nerves can be mapped with recording needles placed in the posterior pharyngeal wall and the tongue. However, mapping alone is not sufficient to preserve the lower cranial nerves and swallowing functions. To overcome this problem, we attempted to devise a method to intraoperatively monitor vocal cord movements with a laryngoscope. We used this method, in addition to other types of brainstem mapping, in three cases. METHODS: Recording needles were inserted into the posterior pharyngeal wall and the tongue, to record the responses of Cranial Nerves IX and XII. A laryngoscope was inserted orally, for direct observation of vocal cord movements, and was maintained until the end of the operation. The floor of the fourth ventricle was stimulated with a monopolar stimulator. Somatosensory evoked potentials, auditory evoked potentials, and motor evoked potentials were simultaneously monitored. RESULTS: We were able to confirm synchronized vocal cord adduction with stimulation of the expected vagal trigonum location and to monitor rhythmic vocal cord movements during spontaneous respiration. In all three cases, we removed the lesions without postoperative complications. CONCLUSION: In addition to intraoperative vocal cord monitoring with a laryngoscope, we could safely determine the optimal location for the first incision in the floor of the fourth ventricle. Potentially lethal postoperative complications can be avoided with brainstem mapping and vocal cord monitoring.

Brain Mapping↗
PubMedDate not supplied

[Cerebral oximetry in neurosurgical patients with cerebrovascular diseases. I. Analysis of causes of intraoperative changes in rSO2 values and its prognostic significance].

A total of 144 neurosurgical interventions were performed in 138 patients with cerebrovascular diseases (arterial aneurysms in the acute and cold periods after a subarachnoidal hemorrhage, arteriovenous malformations, and carotid-cavernous anastomoses). Intraoperative monitoring of regional saturation of hemoglobin with oxygen in the blood flowing in brain vessels was carried out by a cerebral oximeter INVOS 3100 for early intraoperative diagnosis of cerebral ischemia. This paper analyzes factors affecting changes in rSO2 parameter during surgery and discusses the prognostic significance of the detected shifts. Various factors affected the time course of rSO2: decrease in AP within the framework of controlled arterial hypotone and other causes, insertion of autosupported retractor spatulae, temporary clipping and embolism of cerebral arteries, vasospasm, aneurysm rupture, dissection of arteriovenous malformation, etc. Any intraoperative shift of rSO2 surpassing 5%, no matter of what direction (decrease or increase), deserves special attention of anesthesiologist, as it indicates development of cerebral ischemia with a high degree of probability.

Adolescent↗
PubMed1991

[Intraoperative computed EEG monitoring for evaluating the adequacy of general anesthesia].

The article analyses the possibilities of computed EEG monitoring for evaluation of the magnitude and adequacy of the modern methods of general anesthesia: NLA, NLA with halothane inhalation, NLA including Kalipsol bolus administration. An original coefficient, called the adequacy index (AI), was found, which reflects the percentage contribution of deep rhythms (delta and theta) to the total power of the EEG in the range of 0 to 20 Hz. It is shown that the dynamics of this index correlates with the degree of the blocking of entry of sensory nociceptive information into the CNS. The lower boundary of AI-70% was determined, below which the generally accepted signs of anesthesia inadequacy appear: hyperactivity develops, a shift of pH in the acid direction occurs, and the base deficiency increases. It is suggested that determination of AI is used as a highly sensitive and operative test for routine monitoring of the patient's intraoperative condition and express diagnosis of inefficacy of anesthesia.

Anesthesia, General↗
PubMed1996

[The value of differential recording of subcortical somatosensory evoked potentials (SEP) in neurosurgery].

The role of subcortical median nerve somatosensory evoked potential (SEP) testing is exemplified in neurosurgical patients with syringomyelia, coma, brain death, or undergoing intraoperative monitoring. Of special importance is the isolated recording of two components with similar latencies but different generator sites: N13 (lower cervical spinal cord) and P14 (caudal brain stem). These two potentials overlap in conventional neck-scalp recordings using a frontal reference. Theoretical implications and practical aspects of a differential recording of subcortical SEP in neurosurgery are discussed.

Brain Death↗
PubMed1997

Endoscopic monitoring of operative procedures during cardiac surgery.

Both intracardiac repair and fine anastomotic procedures are hard to visualize in the sterile operative field. To overcome this problem, we have recently developed an endoscope video system for intraoperative monitoring in open heart surgery. The endoscope can be introduced into the cardiac cavity in a sterile fashion and thus be used to visualize intracardiac lesions as well as the operative procedures. This endoscopic video monitoring system is considered to be useful not only for thoracic surgery but also for cardiac surgery as well.

Adolescent↗