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We present a system of intraoperative continuous monitoring of intraocular pressure (IOP) consisting of a sterilizable pressure sensor attached to a digital monitor and an analogic recording instrument. Used in conjunction with an anterior-chamber maintainer, IOP may be accurately maintained at a specific and desired level.
Paraplegia remains to be one of the most dangerous complications following thoracoabdominal aortic surgery with an incidence of 0.5 to 40%. Therefore, intraoperative monitoring of spinal cord function is very important when choosing the appropriate surgical technique. Early detection of spinal cord injury continues to be a crucial problem, moreover, the currently applied electrophysiological methods appear to be inaccurate. The aim of the study was to detect prospective spinal cord injury intraoperatively by monitoring the biochemical parameters of the cerebrospinal fluid (CSF). The authors studied the reversible aerobic/anaerobic metabolic changes by monitoring CSF lactate levels, moreover S-100 protein and neuron-specific enolase (NSE) concentrations--specific for neuroglia and neuronal injury, respectively. One of the important methods to prevent paraplegia is the intraoperative CSF drainage, which may improve spinal cord perfusion. Between 1996-1998 51 patients underwent reconstructive thoracic or thoracoabdominal aortic aneurysm operation. The continuously drained CSF was collected in 10 ml fractions during the preparation, whereas during aortic cross-clamping and de-clamping 10 minute fractions were used. All CSF samples were immediately analysed intraoperatively for pH, pCO2, HCO3, potassium and lactate levels, S-100 protein and NSE were analysed by immunoluminescence. CSF lactate levels increased slightly during aortic clamping and a moderate, but non-significant increase was found in the hyperemic phase (reperfusion) in patients without spinal cord ischemia. Spinal cord injury was detected in 7 cases. These patients exhibited a significant CSF-lactate increase (control vs aortic cross-clamping: 1.9 vs 5.3 mmol/l), moreover CSF-lactate remained elevated throughout the whole operation. Paraplegia did not occur, Tarlov 2 paraparesis developed in four cases and three patients displayed cerebral damage. Intraoperative CSF--especially CSF-lactate--monitoring may help the operating team to detect early anaerobic changes of the metabolism the spinal cord.
PURPOSE: To report transesophageal echocardiographic (TEE) findings consistent with intraoperative acute diastolic dysfunction in a series of patients undergoing thoracoabdominal aortic aneurysm (TAAA) repair. METHODS: A series of nine consecutive patients underwent TAAA repair with intraoperative TEE monitoring. Surgical repair was performed with the adjunct of a left atrio-femoral bypass. Invasive arterial and venous pressures were monitored. Intraoperative TEE was utilized to assess the diastolic function before, and during aortic cross clamping. Diastolic dysfunction was defined as a mitral inflow pulsed wave Doppler (E: A ratio) < 1. RESULTS: All patients demonstrated an E: A ratio > 1 (1.3 +/- 0.08) before aortic cross clamping. During cross clamp, the E: A ratio decreased to < 1 (0.75 +/- 0.05) in six of nine patients consistent with diastolic dysfunction. The three patients who did not develop E: A changes were receiving ss-blockers pre-operatively. Patients with diastolic dysfunction were treated with nitroglycerin infusions, which resulted in restoration of their E: A ratios > 1 (1.2 +/- 0.09). Three of the patients with intraoperative diastolic dysfunction developed postoperative myocardial infarction. CONCLUSIONS: Chronic diastolic dysfunction is a well-known entity. This report describes acute diastolic dysfunction, which was observed frequently in patients undergoing TAAA during aortic cross clamp. Further research is required to confirm this phenomenon and determine its possible association with increased postoperative cardiac morbidity.
OBJECTIVE: To assess the efficacy of three intraoperative auditory monitoring techniques: auditory brainstem response (ABR), electrocochleography (ECoG), and direct eight nerve monitoring (DENM). STUDY DESIGN: A retrospective review of the intraoperative recordings of ABR, ECoG, and DENM was performed. SETTING: A private, neurotologic practice. PATIENTS: Sixty-six patients with usable preoperative hearing underwent intraoperative auditory monitoring with ABR, ECoG, or DENM. INTERVENTIONS: Intraoperative auditory monitoring. MAIN OUTCOME MEASURES: Postoperative pure-tone hearing threshold and word recognition scores. RESULTS: Of the 66 patients, 16 (24%) had postoperative serviceable hearing. Five (18%) of the 28 with ABR monitoring, 3 (17%) of the 18 with ECoG monitoring, and 8 (40%) of the 20 with DENM monitoring had serviceable hearing after surgery. CONCLUSIONS: This study suggests that DENM may be more effective than ABR or ECoG, although the differences in hearing preservation rates are not statistically significant.
We have used and studied intraoperative cerebral monitoring in order to prevent intraoperative and early postoperative cerebral ischaemia. The techniques examined have included stump pressure measurement, the evaluation of somatosensory evoked potentials (SEPs) and completion intraoperative angiography. Stump pressure was measured in 920 patients and a safety level of 50 mmHg confirmed. Below this value, non-shunted patients were three times more likely to have cerebrovascular accident (CVA). SEPs were prospectively monitored in 72 patients and a mean decrease of N20-P25 in complex amplitude was seen in patients with a positive CT scan. In particular, pathological SEPs were found in 53% of patients with a positive CT scan, and in 54% of those with a contralateral carotid occlusion. In these patients, the N20-P25 amplitude fell progressively in the first 4 min. Using SEPs, the indication for shunting was 42% lower than with the measurement of back pressure and no patient with normal SEPs had a postoperative neurological deficit. The data obtained under local anaesthesia in 25 patients monitored by stump pressure and SEPs did not give better results. Intraoperative completion angiography performed routinely since 1978 has made it possible to reduce the need for immediate reoperation from 10-2%.
Until recently, the presence of a ventriculoperitoneal shunt (VPS) was considered an absolute contraindication to laparoscopy. In some cases, intraabdominal insufflation causes a rapid, sustained increase in intracranial pressure (ICP). Such intracranial hypertension may result in hindbrain herniation. To prevent this, the use of lower abdominal pressures, intraoperative ICP monitoring, intraoperative ventricular drainage, and distal shunt catheter clamping/externalization has been reported in some studies. However, other studies show that laparoscopy is safe even without VPS catheter clamping and with only routine anesthetic monitoring. Moreover, the risk of retrograde failure of the valve system has been shown to be minimal even with intraabdominal pressures as high as 80 mm Hg. We report how we managed a hydrocephalic adult with a VPS shunt undergoing laparoscopic cholecystectomy in the hope that our experience contributes to the successful management of such patients in the future.
Intraoperative auditory brainstem response (ABR) monitoring was performed in 27 patients undergoing C-P angle surgery (12: hemifacial spasm, 10: trigeminal neuralgia, 2: glossopharyngeal neuralgia, 3: C-P angle tumor, 2 epidermoid, 1 meningioma). Because of the introduction of this method, no patient suffered from postoperative hearing disturbance in this series. During C-P angle surgery, the wave V of ABR changes according to the retraction of the cerebellum and the manipulation of the eighth cranial nerve. Many authors have discussed this change, however the timing and the mechanism of disappearance of wave V is unclear. Accordingly, the authors discussed the correlation between the prolongation of wave V latency and its amplitude. The wave V amplitude was measured from the positive peak of wave V to the next negative peak. Then, the correlation between the prolongation of wave V latency and its reduction ratio (%) of amplitude was represented as a parabola. The wave V reduces its amplitude when the prolongation of the latency is from 1.5 ms to 2.0 ms. Once the prolongation of the latency is over 1.5 ms, the amplitude of wave V seems to be reduced suddenly, because it takes over 1'30'' to finish each record. But the authors demonstrated the gradual reduction of the amplitude of wave V in Figure 3. As mentioned above, the prolongation of wave V latency must be less than 1.5 ms, and the neurosurgeon must recognize this turning point during C-P angle surgery.
Electrodiagnostic testing of the facial nerve has evolved beyond prognostic and topognostic testing to include preoperative assessment and intraoperative monitoring. The state of the art in facial nerve testing is herein reviewed. Electroneurography is described as a means of preoperative assessment to detect subclinical neural degeneration for temporal bone tumors, malignant external otitis, and recurring facial paralysis. Techniques of intraoperative facial nerve monitoring are presented with clinical correlation of the facial evoked responses. Finally, recent advances in electrodiagnostic testing, including antidromic recording and transtemporal magnetic stimulation of the facial nerve, are discussed.
Transcranial cerebral oximetry based on the principle of near-infrared spectroscopy has been successfully used in a variety of neurosurgical conditions, primarily those associated with disturbed cerebral circulation. The non-invasive technique of cerebral oximetry provides valuable information about brain oxygenation in patients with cerebral ischemia (due to occlusion or stenosis of the internal carotid artery). It is also used in intraoperative monitoring of carotid endarterectomy and surgical procedures performed under deep hypothermia and circulatory arrest, during neuroendovascular procedures, and in critical care settings (in patients with arterial vasospasm and during the terminal period). This article describes our preliminary clinical experience with the use of this new technique and summarizes the current literature on clinical and experimental use of transcranial cerebral oximetry.
OBJECTIVE: To demonstrate the role of intraoperative multichannel electromyographic (EMG) monitoring to reduce postoperative deterioration and achieve full untethering of complex occult dysraphisms. METHODS: A retrospective analysis was performed on 66 patients who underwent operation for lumbosacral lipomas. Twenty recent cases were submitted to EMG monitoring and stimulation. RESULTS: All patients presented symptoms at the time of surgery, and 74% exhibited progressive deterioration during the lengthy preoperative period. Postoperative surgery-related deterioration was observed in 6% of patients. This number was reduced to zero with the introduction of intraoperative EMG monitoring. CONCLUSION: Intraoperative multichannel EMG monitoring can be carried out and requires only minimal changes to anesthetic procedures. With this method, it is possible to better identify the neural structures of complex malformations, reducing the risks of surgical damage and incomplete detethering.
An instrument for intraoperative sensing of surgeons' hand tremor during vitreoretinal microsurgery has been developed. The instrument uses inertial sensing to detect tremor in six degrees of freedom. Instrument tip velocity is computed using the sensor data. The displacement amplitude of the tremor is then approximated analytically by modeling the velocity as sinusoidal. The instrument presently estimates oscillations at physiological tremor frequencies with error of less than 7%.
OBJECTIVE: To investigate the value of intraoperative auditory monitoring techniques in acoustic neuroma surgery. METHODS: Ten cases with acoustic neuroma were resected with retrosigmoid approach. Continuous hearing monitoring of auditory brainstem responses (ABR) and transtympanic electrocochleography (ECochG) was performed during operation. RESULTS: Before surgery, 3 patients had class A hearing, 4 had class B hearing, and 3 had class C hearing. With ABR monitoring, 5 patients had waves I , III and V, 5 had only waves I preoperation. After anesthesia,only 2 cases had waves I, III and V, 6 had wave I (Compound action potential, CAP N1 is equivalent to wave I of ABR) and 2 had no waves. The hearing was preserved in 2 cases, which had class A hearing post operation with tumor size <2 cm. With continuous hearing monitoring, the waves of I , III and V could be evoked in one case. In another case, the waves of I, III could be evoked after the tumor resection with the disappearance of wave V. The hearing was not preserved in 8 cases. The 6 out of 8 cases showed up CAP (waves I ) waveform. The CAP amplitudes decreased significantly in 4 cases and even dropped to zero while dissecting the tumor at the lateral end of the internal auditory canal (IAC) or clamping the internal auditory artery (IAA) during operation. After surgery, the CAP amplitudes were recovered to 50%-60% of normal level or normal. In one case, although the cochlear nerve was cut down, the CAP could still be recorded after the tumor resection. However, the CAP amplitudes was dropped to zero while pressurized and pulled cochlea nerve of brainstem lateral and the wave disappeared post-operation in another cases. The waves had not been recorded in two cases after anesthesia. One of them showed low amplitude of CAP wave when the tumor partially removed. The others had no wave all the time. CONCLUSIONS: In combination with ABR monitoring, ECochG proved to be a useful supplementary tool for hearing preservation in acoustic neurinoma surgery. Drilling of the IAC and tumor removal at the lateral end of the IAC were the most critical steps for achieving hearing preservation. The surgeon's experience are the most significant factors influencing the hearing outcome after removal of acoustic neuroma.
We treated 20 cases of acoustic neuromas in the last 2 1/2 years using the suboccipital approach with intraoperative monitoring of eighth nerve function in an attempt to preserve hearing. Total tumor removal was accomplished in 18 cases. Three tumors were small (less than 2 cm in size); 3 tumors were moderate sized (2 to 3 cm) and 14 tumors were large (greater than 3 cm). In 15 cases, all BAER components were lost during surgery. These patients had no postoperative hearing. In five patients there was intraoperative preservation of some or all BAER components. These included the three patients with small tumors and two other patients with moderate sized tumors. One patient with a moderate size tumor had preservation of wave 1 only, and had no postoperative speech discrimination. One patient with a small tumor retained all 5 BAER components, but had no postoperative hearing. Three patients in our series retained functional hearing after surgery, including 3 of 5 patients with tumors 2 cm or smaller. Intraoperative BAER monitoring appears to be useful in predicting postoperative hearing. Tumor size seems to be the primary factor in preservation of hearing following acoustic neuroma surgery.
Intraoperative electrophysiological recordings are gradually becoming part of standard medical practice, mainly because they offer an objective and effective way to assess the functional integrity of the nervous system of a patient during the course of an orthopedic, neurological, or vascular surgery. Continuous monitoring of spontaneous and triggered bioelectrical activity not only can avert damage of neurological structures that are at risk during certain surgical maneuvers, but also allows identification of specific neuronal structures and landmarks that cannot be easily recognized on anatomical grounds only. This series on neurophysiological monitoring will introduce various techniques of monitoring available today, the rationale for their intraoperative use, and the main principles on which they are based. Recommendations for proper implementation and troubleshooting will also be given. The present article gives a general overview of the procedures.
The purpose of intraoperative monitoring is to preserve function and prevent injury to the nervous system at a time when clinical examination is not possible. Cranial nerves are delicate structures and are susceptible to damage by mechanical trauma or ischemia during intracranial and extracranial surgery. A number of reliable electrodiagnostic techniques, including nerve conduction studies, electromyography, and the recording of evoked potentials have been adapted to the study of cranial nerve function during surgery. A growing body of evidence supports the utility of intraoperative monitoring of cranial nerve nerves during selected surgical procedures.
BACKGROUND: Intraoperative cranial nerve monitoring has been applied for the preservation of nerve function during skull base surgery. However, its usefulness is controversial because clinical results reported are limited. METHODS: We evaluated the usefulness of intraoperative electrophysiologic monitoring of the third to seventh cranial motor nerves in 15 patients undergoing skull base surgery. Intracranial bipolar electrical stimulation of each nerve was performed, and compound muscle action potentials (CMAP) were recorded from the innervated muscles. RESULTS: CMAPs were successfully recorded from 23 of the innervated muscles. The loss of the CMAP response during the manipulation of lesions or high stimulus intensity at the end of manipulation seem to be related to the postoperative deficits of nerve function. CONCLUSIONS: The results suggest that intraoperative electrophysiologic monitoring of cranial motor nerves is useful for prediction of postoperative nerve function.
Under conditions of ischemia, the hydrogen ion [H+] accumulates in the myocardial tissue in proportion to the magnitude of the ischemic insult. The accumulation of [H+] is the result of both increased anaerobic production of [H+] secondary to decreased substrate and decreased washout of [H+] secondary to decreased coronary perfusion. The Khuri tissue pH electrode/monitoring system has been developed and validated over the past two decades. Its scientific basis and correlates have been established, and it is the only system that has been approved for use in humans. Myocardial tissue pH has been monitored in the anterior and posterior walls of the left ventricle in more than 700 patients undergoing major cardiac surgery. An understanding of the relationship between pH and temperature and between the pH and [H+] in tissues is important for the proper interpretation of the myocardial pH data generated in the course of an operation. Intraoperative monitoring of myocardial pH is the only modality available to the cardiac surgeon for online assessment and improvement of the adequacy of myocardial protection. By defining myocardial protection in terms of protection from myocardial tissue acidosis, this technology provides a new tool with which the comparative efficacy of the various myocardial protection techniques can be assessed. It also provides an online tool for assessing the adequacy of coronary revascularization, and has the potential of improving procedures and outcomes for off-pump coronary artery bypass grafting.
BACKGROUND: Perioperative stroke rates with carotid endarterectomy are 3.4% for asymptomatic and 5.2% for symptomatic patients. Several methods are used to limit perioperative stroke. METHODS: A retrospective chart review of consecutive carotid endarterectomies from January 1, 2000 to February, 28, 2003, was performed. Data were collected on patient demographics, operative procedure, intraoperative monitoring, and outcome. Comparative analysis of intraoperative monitoring and outcome was performed. RESULTS: Two hundred twenty-nine patients underwent 251 carotid endarterectomies. In 196 procedures decision to shunt was based on intraoperative monitoring, 129 by electroencephalogram (EEG), and 67 by stump pressures. Sixteen neurologic events occurred perioperatively, one transient ischemic attack and 15 strokes. The EEG group had 12 strokes, with a 38% event rate in procedures with EEG changes without shunting. The stump pressure group had one stroke. Stroke rate for intraoperative EEG monitoring was elevated (P = 0.02). CONCLUSIONS: Intraoperative EEG based decision to shunt may not be as effective as other methods for prevention of perioperative neurologic events. When EEG changes occur, shunting is necessary.