Intraoperative Monitoring Tool Research Articles

N°196 – High voltage electrical stimulation as an intraoperative monitoring tool in musculoskeletal tumor surgeries

N°196 – High voltage electrical stimulation as an intraoperative monitoring tool in musculoskeletal tumor surgeries

Classification of Acoustic Hearing Preservation After Cochlear Implantation Using Electrocochleography.

The objective to preserve residual hearing during cochlear implantation has recently led to the use of intracochlear electrocochleography (ECochG) as an intraoperative monitoring tool. Currently, a decrease in the amplitude of the difference between responses to alternating-polarity stimuli (DIF response), predominantly reflecting the hair cell response, is used for providing feedback. Including other ECochG response components, such as phase changes and harmonic distortions, could improve the accuracy of surgical feedback. The objectives of the present study were (1) to compare simultaneously recorded stepwise intracochlear and extracochlear ECochG responses to 500 Hz tone bursts, (2) to explore patterns in features extracted from the intracochlear ECochG recordings relating to hearing preservation or hearing loss, and (3) to design support vector machine (SVM) and random forest (RF) classifiers of acoustic hearing preservation that treat each subject as a sample and use all intracochlear ECochG recordings made during electrode array insertion for classification. Forty subjects undergoing cochlear implant (CI) surgery at the Oslo University Hospital, St. Thomas' Hearing Implant Centre, or the University Hospital of Zurich were prospectively enrolled. In this cohort, DIF response amplitude decreases did not relate to postoperative acoustic hearing preservation. Exploratory analysis of the feature set extracted from the ECochG responses and preoperative audiogram showed that the features were not discriminative between outcome classes. The SVM and RF classifiers that were trained on these features could not distinguish cases with hearing loss and hearing preservation. These findings suggest that hearing loss following CI surgery is not always reflected in intraoperative ECochG recordings.

C-Arm a Useful Tool for Surgeons in Reduction of Zygomatic Complex Fracture: A Comparative Study: Article Type-Original Research.

Reduction of zygomaticomaxillary (ZMC) fracture is often difficult to evaluate intraoperatively because of it peculiar anatomy and limited accessibility. The purpose of this study is to evaluate the efficacy of use of C-arm as a tool for intraoperative monitoring of ZMC fracture reduction. Group I (C-Arm) and Group II (control group) comprised of patients with isolated unilateral displaced Zygomatic complex (ZMC) fractures and having orbital volume change. The efficacy of use of C-arm intra-operatively was evaluated to analyse the reduction of fracture. It was observed that mean change in ocular volume was around 1.07cm2 for Group I and 1.51cm2 in Group II. Thus post-operative eye volume was near to normal in Group I than Group II. The change in ocular volume post-operatively was observed to be statistically significant (p-value < 0.05) in both the groups. Post HOC Tukey statistical analysis determined the intergroup relation in change in eye volume between normal, pre- and post-operative and was found to be statistically significant (p-value < 0.05). The intergroup comparison between Group I and Group II was done using ANOVA statistical analysis and was found to be statistically significant (p-value < 0.05). Our study revealed that C-arm is definitively an effective tool in the oral and maxillofacial surgery armamentarium, giving better results with minimal surgical exposure and by eliminating operator related error. The online version contains supplementary material available at 10.1007/s12070-022-03221-y.

TH-295. High voltage electrical stimulation as an intraoperative monitoring tool in musculoskeletal tumor surgeries

TH-295. High voltage electrical stimulation as an intraoperative monitoring tool in musculoskeletal tumor surgeries

Utility of Intraoperative Cortico-Cortical Evoked Potentials for the Evaluation of Language Function During Brain Tumor Resection

The cortico-cortical evoked potentials (CCEP) are a relatively recent intraoperative monitoring tool that has shown high reliability in detecting the functional language area and its connections. In this work we describe a patient with a tumor located in the language area who underwent tumor resection. A neurophysiological intraoperative mapping of the frontal and posterior language area with the anesthetized patient was carried out. Then the patient was awaked. To demonstrate the relationship between language function and CCEP, the Ojemann’s stimulation technique was used in the same electrodes were CCEPs were obtained. An alteration in the emission of language had been found on the electrodes where CCEP was obtained and in adjacent electrodes. During tumor resection we used a double check for language function: neurological evaluation and CCEPs. We obtained a biunivocal relationship between warning criteria in the CCEP and immediate language impairment on neurological examination. We always observed a significant decrease in the CCEP associated with language impairment. The CCEP are able to obtain information in real time with a good spatial resolution of the language function. Future studies should be carried out in order to analyse the robustness of this technique to perform it in anesthetized patients.

Intraoperative Troponin Elevation in Liver Transplantation Is Independently Associated With Mortality: A Prospective Observational Study.

Intraoperative factors implicated in postoperative mortality after liver transplantation (LT) are poorly understood. Because LT is a particularly demanding procedure, we hypothesized that intraoperative myocardial injury may be frequent and independently associated with early postoperative outcomes. We aimed to determine the association between intraoperative high-sensitivity troponin (hsTn) elevation during LT and 30-day postoperative mortality. A total of 203 adult patients undergoing LT were prospectively included in the cohort and followed during 1 year. Advanced hemodynamic parameters and serial high-sensitivity troponin T (hsTnT) measurements were assessed at 6 intraoperative time points. The optimal hsTnT cutoff level for intraoperative troponin elevation (ITE) was identified. Patients were classified into 2 groups according to the presence of ITE. Independent impact of ITE on survival was assessed through survival curves and multivariate Cox regression analysis. Intraoperative cardiac function was compared between groups. Troponin levels increased early during surgery in the ITE group. Troponin values at abdominal closure were associated with 30-day mortality (area under the receiver operating caracteristic curve, [AUROC], 0.73; P=0.005). Patients with ITE showing values of hsTnT ≥61ng/L at abdominal closure presented higher 30-day mortality (29.6% versus 3.4%; P<0.001). ITE was independently associated with 30-day mortality (hazard ratio, 3.8; 95% confidence interval, 1.1-13.8; P=0.04) and with worse overall intraoperative cardiac function. The hsTnT upper reference limit showed no discriminant capacity during LT. Intraoperative myocardial injury identified by hsTn elevation is frequently observed during LT, and it is associated with myocardial dysfunction and short-term mortality. Determinations of hsTn may serve as a valuable intraoperative monitoring tool during LT.

Transcranial Doppler for Eagle Syndrome: Rare Presentation of Unilateral Internal Carotid Artery Compression by the Stylohyoid Ligament With Provocative Maneuvers

Eagle syndrome is a rare condition caused by compression of the internal carotid artery (ICA) or cranial nerves by an elongated styloid process or calcified stylohyoid ligament. This patient is a 56 year-old woman who presented with episodes of positional syncope for 8 years. Transcranial Doppler (TCD) demonstrated abnormally decreased flow in the left middle cerebral artery (MCA) during the syncopal episodes. The patient was evaluated by TCD, transcranial imaging (TCI), and carotid duplex (CD). First, a baseline CD and TCI were performed with the patient in a neutral position. TCD was then used during symptomatic provocative maneuvers to monitor the bilateral MCAs. Intraoperative TCD monitoring was also done during bilateral stylohyoid ligament resection, and postoperatively during the same provocative maneuvers. The baseline CD examination revealed normal extracranial carotid anatomy; TCD and TCI showed normal mean velocities and a normal anatomic variant of fetal origin of the left posterior cerebral artery. During provocative maneuvers, TCD showed abnormally dampened to absent flow in the left MCA, consistent with compression of the left extracranial ICA. CT scan confirmed elongated stylohyoid ligaments bilaterally. The MCA mean velocities were monitored intraoperatively and postoperatively by TCD and showed no changes with head positioning immediately following resection of the stylohyoid ligaments. The patient reported no syncopal episodes at follow-up 6 days after surgery. Although rare, Eagle syndrome should be considered as a cause of positional syncope. TCD can serve as a diagnostic test, an intraoperative monitoring tool, and a method for documenting the surgical outcome.

Role of Transesophageal Echocardiography in General Anesthesia

Transesophageal echocardiography (TEE), a relatively non-invasive method, is an ideal intraoperative monitoring tool. In this review, we evaluated all potential applications of TEE in general anesthesia. The uses of intraoperative TEE have expanded over the years. TEE’s main application is in the intraoperative assessment and monitoring of the cardiac function. Its impact in clinical decision making has been demonstrated in non-cardiac surgery in the operating room and as a rescue in case of hemodynamic instability and cardiac arrest. TEE may also provide more complete quantitative hemodynamic monitoring of intracardiac pressures as the pulmonary artery catheter. Newer intraoperative TEE application includes imaging of extra-cardiac structures such as the kidney, the intrahepatic inferior vena cava, the lungs, the pleura space, and the epidural space. Several scanning protocols have been proposed ranging from a focused to a comprehensive cardiac assessment. Current guidelines for intraoperative use of TEE include basic and advanced TEE exam. Intraoperative TEE is a very powerful tool in the hands of the TEE trained anesthesiologist. It has a positive safety profile but requires a significant initial manpower and financial investment. While less expensive equipment has become available, specific training is necessary and requires a significant time commitment.

Biochemical mechanisms of pallidal deep brain stimulation in X-linked dystonia parkinsonism.

Invasive techniques such as in-vivo microdialysis provide the opportunity to directly assess neurotransmitter levels in subcortical brain areas. Five male Filipino patients (mean age 42.4, range 34-52 years) with severe X-linked dystonia-parkinsonism underwent bilateral implantation of deep brain leads into the internal part of the globus pallidus (GPi). Intraoperative microdialysis and measurement of gamma aminobutyric acid and glutamate was performed in the GPi in three patients and globus pallidus externus (GPe) in two patients at baseline for 25/30 min and during 25/30 min of high-frequency GPi stimulation. While the gamma-aminobutyric acid concentration increased in the GPi during high frequency stimulation (231 ± 102% in comparison to baseline values), a decrease was observed in the GPe (22 ± 10%). Extracellular glutamate levels largely remained unchanged. Pallidal microdialysis is a promising intraoperative monitoring tool to better understand pathophysiological implications in movement disorders and therapeutic mechanisms of high frequency stimulation. The increased inhibitory tone of GPi neurons and the subsequent thalamic inhibition could be one of the key mechanisms of GPi deep brain stimulation in dystonia. Such a mechanism may explain how competing (dystonic) movements can be suppressed in GPi/thalamic circuits in favour of desired motor programs.

Measuring the Femoral Head Size — An Additional Real-Time Intraoperative Monitoring Tool for the Accuracy of the Preoperative Process and Implant Selection

The purpose of this study was to examine the correlation between the implanted cup’s outer diameter and the actual femoral head diameter removed during surgery. Seventy-five patients with primary total hip arthroplasty were evaluated. The difference between the implanted cup diameter and the femoral head diameter was calculated for each patient. The mean±SD actual femoral head diameter that was removed and measured during surgery was 48.5±3.7mm. The mean±SD cementless implanted cup outer diameter was 51.8±3.5mm. A high correlation was found between the implanted cup diameter and the actual femoral head diameter (r=0.923). A cut-off point of 4mm of the measured femoral head diameter should be considered as an additional monitoring indicator.

Perioperative haemodynamic monitoring by oesophageal Doppler improves outcome of patients with abdominal aortic aneurysm repair

AAA repair is associated with high rate of mortality and morbidity. Oesophageal Doppler (OED) can offer a less invasive cost-effective tool for intraoperative monitoring of haemodynamic changes. The aim of the study was to confirm the benefits of haemodynamic optimisation in patients undergoing AAA repair using OED monitoring. We assumed that haemodynamic parameters of patients with OED would be better optimised; they would probably get more fluids during the operation, and their ICU and hospital stay would be shorter as a result of having fewer postoperative complications and lower mortality. Seventy patients (Doppler group) who underwent AAA operation in 2003-2008 were matched with 70 patients (control group) operated on AAA in 1998-2002. OED was used to estimate the cardiac output, its variations and fluid management. The administered fluids, length of ICU and hospital stay, frequency of postoperative complications and mortality were compared in Doppler and control groups (Mann-Whitney test, Fisher's exact test). No statistically significant difference was found in preoperative parameters. The Doppler group was administered significantly more crystalloids (p<0.001), colloids (p<0.001), sum-up of fluids (4000 ml vs. 3000 ml; p<0.001) in the perioperative period. The Doppler group had a lower incidence of major serious complications (8 vs. 21; p=0.034) and shorter ICU (4 vs. 6 days; p<0.001) and hospital stay (10 vs. 11 days; p=0.012). The haemodynamic monitoring by oesophageal Doppler can improve the outcome of patients with AAA repair (fewer major complications, shorter ICU and hospital stay) (Tab. 4, Fig. 4, Ref. 25).

Surgery for Ruptured Sinus of Valsalva Aneurysm into Right Ventricular Outflow Tract: Role of Intraoperative 2D and Real Time 3D Transesophageal Echocardiography

A major limitation of the 2D echocardiography during surgery for a complex cardiac lesion is its inability to provide an accurate spatial orientation of the structure. The real time 3D transesophageal echocardiography (RT-3D-TEE) technology available in Philips IE 33 ultrasound machine is relatively new to an operation suite. We evaluated its intraoperative utility in a patient, who was operated for repair of a ruptured sinus of Valsalva aneurysm (RSOVA) and closure of a supracristal ventricular septal defect. The VSD and RSOVA were visualized through different virtual windows in a more promising way on intraoperative RT-3D-TEE than on the 2D echocardiography. The acquired images could be virtually cropped and displayed in anatomical views to the operating surgeon for a clear orientation to the anatomy of the lesion. RT-3D-TEE is a potential intraoperative monitoring tool in surgeries for complex cardiac lesions.

Surgical Banding for Refractory Hemodialysis Access-Induced Distal Ischemia (HAIDI)

Hemodialysis patients may develop distal ischemia in an extremity harboring a functioning arteriovenous access (AVA). Surgery is indicated if conservative treatment including catheter-based therapies fails. The role of surgical banding for refractory hemodialysis access-induced distal ischemia (HAIDI) is systematically reviewed (n=39 articles). If banding is executed without an intraoperative monitoring tool ("blind"), or guided by finger pressures only, clinical success and access patency rates are low (<50%). In contrast, banding is clinically successful when access flow is monitored during the operative procedure, with excellent long-term patency of banded AVA's (97%, 17 +/- 3 months). Banding is the method of choice in HAIDI patients with a normal or high access flow (>1.2 l/min) provided that flow and distal perfusion are closely monitored intraoperatively.

Interference of anesthesia on intraoperative monitoring of spinal motor function with motor-evoked potentials

As a neurophysiological monitoring technique, motor-evoked potentials (MEPs) has been widely used for intraoperatively monitoring motor function of spinal cord. Myogenic MEPs elicited by transcranial electrical stimulation are commonly used to monitor spinal function. However, myogenic MEPs may be interfered by most anesthetic agents and hypothermia. Muhipulse electric stimulation is the recommended tool for intraoperative monitoring of spinal motor function. Key words: motor-evoked potentials; multipulse electric stimulation; anesthetic agents; hypothermia; spinal motor function monitoring

Optical topography can predict occurrence of watershed infarction during carotid endarterectomy: technical case report

Background The major risk of CEA is perioperative stroke. NIRS can detect ischemic changes during CEA; however, possible watershed-type perfusion defects may not be detected by single-channel NIRS occurring at some distance from the light source. In the present case, we tested the usefulness of optical topography (ie, multichannel NIRS, OT) for this purpose. Case Description The patient (64-year-old man) exhibited nonsymptomatic 80% stenosis of the right ICA with normal cerebral perfusion. CEA was performed to prevent cerebral infarction. We used single-channel NIRS and OT for monitoring of perfusion changes during CEA. The optodes of OT were placed on the skull to cover the frontal and parietal lobes on the right side, whereas the sensor of the single-channel NIRS was placed on the right forehead. The single-channel NIRS detected no significant perfusion changes during surgery. However, the OT revealed occurrence of watershed-type perfusion defects in the border region between the right middle and posterior cerebral artery supply areas during cross-clamping of the right internal carotid artery. Postoperative MRI showed an ischemic region which corresponded to the area associated with the perfusion defects. Conclusion OT could detect watershed-type posterior perfusion defects which the single-channel NIRS failed to detect. OT may represent a useful tool for intraoperative monitoring during CEA.

Clinical Outcomes of Low-Risk Patients Undergoing Beating-Heart Surgery With or Without Pulmonary Artery Catheterization

For patients who undergo off-pump coronary artery bypass (OPCAB) surgery, pulmonary artery catheterization (PAC) has been proposed as a useful intraoperative monitoring tool. This study was designed to determine if the choice of PAC versus central venous pressure monitoring (CVP) had any effect on outcome after OPCAB. This study compared these 2 methods of hemodynamic monitoring in low-risk patients undergoing beating-heart surgery via a median sternotomy and evaluated their effect on morbidity and in-hospital mortality. Retrospective database and medical record review. Tertiary care teaching hospital. Low-risk patients who had coronary revascularization via a median sternotomy on the beating heart. None. A population of 2,414 low-risk patients who had beating-heart coronary revascularization between January 2000 and December 2003 was reviewed. Most patients (1,671 or 69.2%) received a PAC, whereas 743 (30.8%) had CVP monitoring. Risk-adjusted logistic regression analyses were performed to investigate the effect of each technique on clinical outcomes. The groups were comparable in both baseline characteristics and Parsonett's mortality risk (1.5 +/- 0.9, p = 0.58). Univariate analysis failed to show a difference in operative mortality (p = 0.76), on-pump conversion rate for completion of aortocoronary bypasses (p = 0.82), postoperative low cardiac output (p = 0.10), or prolonged inotropic agent use (p = 0.22). Similarly, in the multivariate analysis, both groups had a similar rate of conversion to an on-pump procedure for completion of coronary artery grafting (p = 0.91), intraoperative intra-aortic balloon pump use (p = 0.69), low cardiac output state (p = 0.16), or in-hospital mortality (p = 0.51). This single-institution, retrospective study suggests that in low-risk patients undergoing beating-heart surgery, CVP monitoring may be sufficient.

Esophageal Doppler (ODM II) Improves Intraoperative Hemodynamic Monitoring During Laparoscopic Surgery

Minimally invasive laparoscopic surgery has been expanded to the elderly and high-risk surgical patients with underlying cardiac and pulmonary disease. However, possible cardiovascular changes during CO2 pneumoperitoneum necessitate close intraoperative monitoring. In this prospective study, 55 patients (mean age 62.52 years, range 26-82) undergoing laparoscopic surgery were included. Patients were categorized into 3 groups of low (group A: 12 patients, mean age 55.5 years), moderate (group B: 22 patients, mean age 59.5 years), and high (group C: 21 patients, mean age 69.71 years) surgical risk according to ASA physical status classification. Similar anesthetic agents and anesthetic techniques were used in the above cases. An esophageal Doppler (ODM II, Abbott Laboratories) was used to measure aortic blood flow velocity and thereby estimating stroke volume (SVe) and cardiac output (COe) throughout anesthesia, in addition to traditional monitoring. After abdominal insufflation (peak intra-abdominal pressure: 13-15 mm Hg) COe values decreased from the initial value after induction of anesthesia by 22%, 20%, and 18% for groups A, B, and C, respectively (P < 0.05). The above values further deteriorated (25%, 28%, and 30% for groups A, B, and C, respectively) in the anti-Trendelenburg positioning of the patient. The peak aortic blood flow velocity (PV) followed the changes, thus indicating that heart muscle contractility is affected during the procedure. Stabilization of the above values was achieved after 20 minutes of CO(2) pneumoperitoneum and improvement was noted only after deflation of the abdomen. Heart rate and blood pressure essentially remained unchanged throughout the procedure, although the final values were increased compared with initial. Insufflation of the abdomen with CO(2) produces measurable effects on the cardiovascular system that require reappraisal of hemodynamic monitoring during anesthesia. ODM II offers a reliable, relatively noninvasive, cost-effective tool for intraoperative monitoring of the hemodynamic changes with a potential for future application for improvement of intraoperative hemodynamic status of patients.

Imaging of somatotopic representation of sensory cortex with intrinsic optical signals as guides for brain tumor surgery

Intrinsic optical signals in response to somatosensory stimuli were intraoperatively recorded during brain tumor surgery. In the present study, the authors report on the use of this technique as an intraoperative guide for the safe resection of tumors adjacent to or within the sensorimotor cortex. In 14 patients with tumors adjacent to or within the sensorimotor cortex, intrinsic optical signals in response to somatosensory stimuli were recorded by illuminating the brain surface with Xe white light and imaging the reflected light passing through a bandpass filter (605 nm). Results were compared with intraoperative recordings of sensory evoked potentials in all 14 patients and with noninvasive mapping modalities such as magnetoencephalography and positron emission tomography in selected patients. In all but two patients, the somatosensory optical signals were recorded on the primary sensory cortex. Optical signals elicited by stimulation of the first and fifth digits and the three branches of the trigeminal nerve were recorded at different locations on the sensory strip. This somatotopic information was useful in determining the resection border in patients with glioma located in the sensorimotor cortex. Optical imaging of intrinsic signals is a useful technique with superior spatial resolution for delineating the somatotopic representation of human primary sensory cortex. Furthermore, it can be used as an intraoperative monitoring tool to improve the safety and accuracy of resections of brain tumors adjacent to or within the sensorimotor cortex.

Monitoring regional cerebral oxygen saturation using near-infrared spectroscopy during pulsatile hypothermic cardiopulmonary bypass in a neonatal piglet model.

Impairment of cerebral oxygenation in neonates and infants after hypothermic nonpulsatile cardiopulmonary bypass (CPB) support is well documented. The objectives of this study were: 1) using a neonatal piglet model to continuously monitor the regional cerebral oxygen saturation (rSO2) by near-infrared spectroscopy during pulsatile hypothermic CPB; and 2) to quantify the pulsatile flow in terms of energy equivalent pressure (EEP). After initiation of CPB, all piglets (n = 5) were subjected to 15 minutes of core cooling, reducing the rectal temperature to 25 degrees C, followed by 60 minutes of hypothermic CPB, then 10 minutes of cold reperfusion, and 30 minutes of rewarming. During CPB, mean arterial pressures (MAPs) and pump flow rates were maintained at 40-45 mm Hg and 150 ml/kg/min, respectively. During normothermic CPB, the rSO2 was significantly increased, compared with the pre-CPB level (56.8 +/- 5.2% vs. 41.8 +/- 5.5%, p < 0.01). At the end of cooling, the rSO2 level was 76.8 +/- 8.6% (p < 0.001 vs. pre-CPB). After 60 minutes of hypothermic CPB and 30 minutes of rewarming, the rSO2 level was decreased to 38.6 +/- 4.2%, which was not significantly different compared with the pre-CPB level. The average increase in pressure (from MAP to EEP) was 5 +/- 1%, and the average increase in extracorporeal circuit pressure (from ECCP to EEP) was 13 +/- 2%. This extra pressure may help to provide better regional cerebral oxygen saturation. During pulsatile CPB, there was no rSO2 deficiency in this high flow model. Near-infrared spectroscopy responded well to changes in rSO2 during different stages of these experiments and might be a helpful tool for intraoperative monitoring.

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

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. 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. 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. 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.