A New Measure for Monitoring Intraoperative Somatosensory Evoked Potentials

OBJECTIVE: To propose a new measure for effective monitoring of intraoperative somatosensory evoked potentials (SEP) and to validate the feasibility of this measure for evoked potentials (EP) and single trials with a retrospective data analysis study. METHODS: The proposed new measure (hereafter, a slope-measure) was defined as the relative slope of the amplitude and latency at each EP peak compared to the baseline value, which is sensitive to the change in the amplitude and latency simultaneously. We used the slope-measure for EP and single trials and compared the significant change detection time with that of the conventional peak-to-peak method. When applied to single trials, each single trial signal was processed with optimal filters before using the slope-measure. In this retrospective data analysis, 7 patients who underwent cerebral aneurysm clipping surgery for unruptured aneurysm middle cerebral artery (MCA) bifurcation were included. RESULTS: We found that this simple slope-measure has a detection time that is as early or earlier than that of the conventional method; furthermore, using the slope-measure in optimally filtered single trials provides warning signs earlier than that of the conventional method during MCA clipping surgery. CONCLUSION: Our results have confirmed the feasibility of the slope-measure for intraoperative SEP monitoring. This is a novel study that provides a useful measure for either EP or single trials in intraoperative SEP monitoring.

Impact of Cardio-Pulmonary and Intraoperative Factors on Occurrence of Cerebral Infarction After Early Surgical Repair of the Ruptured Cerebral Aneurysms

OBJECTIVE: Delayed ischemic deficit or cerebral infarction is the leading cause of morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH). The purpose of this study is to reassess the prognostic impact of intraoperative elements, including factors related to surgery and anesthesia, on the development of cerebral infarction in patients with ruptured cerebral aneurysms. METHODS: Variables related to surgery and anesthesia as well as predetermined factors were all evaluated via a retrospective study on 398 consecutive patients who underwent early microsurgery for ruptured cerebral aneurysms in the last 7 years. Patients were dichotomized as following; good clinical grade (Hunt-Hess grade I to III) and poor clinical grade (IV and V). The end-point events were cerebral infarctions and the clinical outcomes were measured at postoperative 6 months. RESULTS: The occurrence of cerebral infarction was eminent when there was an intraoperative rupture, prolonged temporary clipping and retraction time, intraoperative hypotension, or decreased O2 saturation, but there was no statistical significance between the two different clinical groups. Besides the Fisher Grade, multiple logistic regression analyses showed that temporary clipping time, hypotension, and low O2 saturation had odds ratios of 1.574, 3.016, and 1.528, respectively. Cerebral infarction and outcome had a meaningful correlation (gamma=0.147, p=0.038). CONCLUSION: This study results indicate that early surgery for poor grade SAH patients carries a significant risk of ongoing ischemic complication due to the brain's vulnerability or accompanying cardio-pulmonary dysfunction. Thus, these patients should be approached very cautiously to overcome any anticipated intraoperative threat by concerted efforts with neuro-anesthesiologist in point to point manner.

Effect of Temporary Clipping on the Cerebral Infarction in Middle Cerebral Artery Aneurysm Surgery / 대한뇌혈관외과학회지

OBJECTIVE: This study evaluated the effects of temporary clipping on an infarction after middle cerebral artery aneurysmal surgery. METHODS: Three hundreds and seventeen patients with a middle cerebral artery aneurysm were treated surgically at our department. Among them, the patients who had an intracerebral hematoma or a cerebral infarction prior to surgery or poor clinical mental state (Hunt and Hess grade V) on admission were excluded from the analysis. Two hundreds and twenty nine patients were selected in this study. An acute cerebral infarction, which had no any evidence of retraction injury or vasospasm and occurred on the same side of the surgical site within 3 days after the operation, was regarded as the cerebral infarction as a result of the temporary clipping. RESULTS: Twenty out of 229 patients (8.7%) developed a new acute cerebral infarction after surgery. The causes of the infarction were as follows: 13 patients related to the temporary clipping, 5 patients to the vasospasm and 2 patients to the brain retraction injury. The incidence of an acute cerebral infarction according to the frequency of temporary clippings was 5.5% (3 of 55 patients) of those who underwent a single temporary clipping, 6.7% (4 of 60 patients) of those who underwent two or three temporary clipping and 20.7% (6 of 29 patients) of those who underwent more than 4 temporary clippings. The incidence of an acute cerebral infarction was significantly higher when the temporary clip had been applied more than 4 times (P<0.021). However, the clipping time didn't show statistically significance. CONCLUSION: The incidence of acute cerebral infarction after a surgery for a middle cerebral artery aneurysm was related to the frequency of temporary clippings during surgery. It was significantly higher in the cases where more than 4 temporary clipping had been applied.

Clinical Analysis of Factors Influencing the Development of Delayed Ischemic Neurologic Deficit after Aneurysm Surgery

OBJECTIVE: This study shows the factors influencing the development of postoperative delayed ischemic neurologic deficit. METHODS: The authors analyzed 120 patients had performed aneurysmal neck clipping. Eleven variables were examined as to relationship to delayed ischemic neurologic deficit and classified as non- surgical and surgical variables. Data were analyzed by the univariate analysis and significant variables were entered into multiple logistic regression model in order to draw out Odds ratio. RESULTS: Delayed ischemic neurologic deficit after aneurysm surgery developed in 23 patients(19.2%). Significant non-surgical variables were clinical grade at admission(p=0.032), CT grade(p=0.005), and degree of preoperative angiographic vasospasm. Surgical variables were timing of surgery, brain retraction time, and duration of temporary clip application. The application time of temporary clip was significant (p=0.032) in development of delayed ischemic neurologic deficit. However, in multiple logistic regression analysis, duration of temporary clip application was excluded. With the clinical grade I - II and the CT grade I - II as the reference, the Odds ratio were 2.358(95% CI 0.87-6.37) and 4.041(95% CI 1.06-15.37), respectively. CONCLUSION: Delayed ischemic neurologic deficit after aneurysm surgery developed in poor clinical grade and high CT grade with high risk. The effect of surgery on the development of post-operative vasospasm was not significant.

The Clinical Experiement to Develop the Brain Protection Protocol in Cerebral Ischemia Using Compressed Spectral Array

OBJECTIVE: The clinical experiment to establish the cerebral protection protocol for hemodynamically vulnerable patients from ischemic insult during surgery is presented. METHODS: The experiment divided in two parts, one is to analyze the effect of intravenous anesthetics and inhalation anesthetics on EEG activity in neurologically intact 81 patients. The others is to develop the stepwise cerebral protection protocol during aneurysm surgery which required temporary clipping, carotid endarterectomy and extracranial intracranial arterial bypass surgery in 61 patients. The cerebral protection protocol included the use of intraoperative compressed spectral array(CSA) monitoring, induced hypertension, thiopental induced burst suppression and moderate hypothermia. RESULTS: With the efforts of brain protection protocol, 59 of the 61 patients recovered without any newly developed neurological deficit from the surgery. One patient had carotid stenosis with multiple untreated aneurysms, and therefore, induced hypertension was not applied. This patient developed significant postoperative neurological deficits correlated well with the CSA changes. In one patient who has cerebral aneurysm, thiopental bolus injection was used. This patient has reduction of EEG activity during temporary clipping and developed the relatively well correlated neurologic deficit postoperatively. Among 28 carotid endarterectomy cases, three patients has definite reduction of EEG activities within 7 to 15 seconds of interval carotid artery(ICA) test clamping before endarterectomy. But, these patients recovered from surgery without any neurological deficit inspite of 28 to 35 minutes ICA clamping with the effort of thiopental induced burst suppression, induced hypertension and moderate hypothermia. CONCLUSION: Cerebral protection protocol under CSA monitoring could prevent ischemic insults from circulatory disruption on vulnerable ischemic hemisphere.

An Experimental Study for the Effect of Interrupted(Intermittently-Repeated) versus Continuous Temporary Clipping on the Change of Arterial Wall of Rat / 대한뇌혈관학회지

The benefits of the use of temporary clipping for intracerebral aneurysm surgery were proved through many experimental and clinical studies. There are two techniques of temporary clipping which are interrupted and continuous clipping. In the study of cerebral perfusion, interrupted clipping reduced ischemic damage to the brain. However, the comparison of histological changes in the arterial wall between them is not reported yet. Temporary clipping on the iliac artery of 80 rats was performed using Yasargil temporary mini clip. The specimens were divided into two groups; Group I (intermittently repeated clipping for 5 minutes was done 3 times on the same site with resting interval for 5 minutes: total clipping time was 15 minutes) and Group II (continuous clipping for 15 minutes). Under the light microscope, the histological findings were examined in the specimens, which were obtained at each time-interval after clipping (0 hr, 3 hrs, 6 hrs, 12 hrs, 3 days, and 3 months). The histological changes of the arterial wall of rat by two techniques for temporary clipping were observed. Although there is no significant difference between two temporary clippings, there is a trend of milder and more delayed arterial change in intermittently-repeated temporary clipping.

Intra-aneurysmal Pressure Changes according to Clippings on the Parent Artery and Aneurysm in Experimental Model of Rabbits: a Preliminary Study

Temporary clipping on parent artery is widely accepted as a useful method to prevent intraoperative aneurysmal rupture, to dissect the aneurysm safely, and to obtain the clear operation field during intraoperative aneyrysm rupture. However, the exact role and adequate technique of the temporary clipping has yet to be determined. The authors performed an experimental study to investigate the effect of temporary clipping on intra-aneurysmal pressure. The experimental aneurysms, using side-to-side anastomosis between common carotid artery and the jugular vein, were made in 24 rabbits. The intra-aneurysmal pressure was monitored through a catheter inserted in the aneurysm. The intra-aneurysmal pressure was significantly decreased to 31.8+/-4.39mmHg after temporary clipping on the proximal common carotid artery(p<.05). On the contrary, intra-aneurysmal pressure was increased to 73.3+/-4.39mmHg after the distal parent temporary clipping. In case of the temporary clipping on both proximal and distal parent artery, the intra-aneurysmal pressure was markedly increased to 81. 0+/-11.7mmHg(p=0.0036 on t-test). In conclusion, the temporary clipping on the parent artery should be performed only on the proximal site of the aneurysm. Temporary clipping on both proximal and distal site would be rather dangerous since it causes sharp increase in intra-aneurysmal pressure during the clipping of aneurysm itself.

Intra-aneurysmal Pressure Changes according to Clippings on the Parent Artery and Aneurysm in Experimental Model of Rabbits: a Preliminary Study

Temporary clipping on parent artery is widely accepted as a useful method to prevent intraoperative aneurysmal rupture, to dissect the aneurysm safely, and to obtain the clear operation field during intraoperative aneyrysm rupture. However, the exact role and adequate technique of the temporary clipping has yet to be determined. The authors performed an experimental study to investigate the effect of temporary clipping on intra-aneurysmal pressure. The experimental aneurysms, using side-to-side anastomosis between common carotid artery and the jugular vein, were made in 24 rabbits. The intra-aneurysmal pressure was monitored through a catheter inserted in the aneurysm. The intra-aneurysmal pressure was significantly decreased to 31.8+/-4.39mmHg after temporary clipping on the proximal common carotid artery(p<.05). On the contrary, intra-aneurysmal pressure was increased to 73.3+/-4.39mmHg after the distal parent temporary clipping. In case of the temporary clipping on both proximal and distal parent artery, the intra-aneurysmal pressure was markedly increased to 81. 0+/-11.7mmHg(p=0.0036 on t-test). In conclusion, the temporary clipping on the parent artery should be performed only on the proximal site of the aneurysm. Temporary clipping on both proximal and distal site would be rather dangerous since it causes sharp increase in intra-aneurysmal pressure during the clipping of aneurysm itself.

Continuous Monitoring of Regional Cortical Blood Flow in Aneurysm Surgery

OBJECTIVE: The tolerance and the safety of temporary arterial occlusion in aneurysm surgery are variable among patients because of individual variations of their collateral circulation. We recorded continuous intraoperative regional cortical blood flow(rCoBF) with thermal diffusion flowmetry(TDF) in patients with aneurysmal subarachnoid hemorrhage to determine a safe time limit for temporary occlusion in relation to rCoBF. PATIENTS AND METHODS: From Oct. '97 to Sep. '98, 40 patients with cerebral aneurysm at anterior cerebral artery(ACA) or middle cerebral artery(MCA) were included in this study. The TDF probe was placed over the cortex which was supplied by corresponding arteries. For data analysis, we included only the patients with Hunt-Hess grade I or II on admission. RESULTS: The total occlusion time of the proximal parent artery in 24 patients was on average 21.8 minutes, ranging between 9 minutes and 68 minutes. The lowest rCoBF in relation to temporary occlusion time in patient with excellent outcome was as follows: 0ml/100mg/min for 13 minutes and 6ml/100mg/min(11% of basal rCoBF) for 18 minutes in the middle cerebral artery and bilateral anterior cerebral arteries, respectively. The multiple regression equation regarding safe time for temporary clipping was as follows: safe time = 5.5 + 0.06 X rCoBF intra + 0.25 X rCoBF pre. And reperfusion time for the full recovery of rCoBF was within 4 minute in most cases, except some no-reflow cases. CONCLUSION: In our study with proper brain protection, a safe time limit for temporary occlusion was calculated 18 minutes even at 0ml/100mg/min in the MCA and this technique seems to be very useful to detect a continuous real time change of rCoBF during aneurysm surgery.

Clinical Analysis of Surgically Treated 134 Cases of Anterior Communicating Artery Aneurysms

This study is a retrospective clinical analysis of 134 cases of anterior communicating artery aneurysms surgically treated in the Department of Neurosurgery, Chungnam National University Hospital from January 1990 to December 1996. The results of analysis were summarized as follows; 1) Peak age incidence was in the sixth decade and male to female ratio was 1: 1.2, showing female predominancy. 2) There was no statistically significant relationship between direction of aneurysm and Fisher's grade, and occurrence of hydrocephalus, and also between the direction, size and shape of aneurysm and preoperative Hunt-Hess grade. 3) There was statistically significant relationship between the shape of aneurysm and angiographic vasospasm; there was high incidence of vasospasm in lobulated and oval shape of aneurysm. But there was no statistically significant relationship between the direction, size of aneurysm and angiographic vasospasm. 4) The correlations between outcome and preoperative Hunt-Hess grade, and occurrence of angiographic vasospasm, and temporary clipping were statistically significant; the outcome was good in cases of no vasospasm, temporay clipping and better preoperative Hunt-Hess grade. 5) The direction, shape and size of aneurysm, existence or not of abnormality in circle of willis, timing of surgery and operative procedure had no statistically significant relationship with outcome. 6) Postoperative complications were vasospasm and infarction(18.7%), brain edema, hydrocephalus, in order of frequency, and the mortality rate was 3%.

Temporary Clipping and Induced Hypotension in Cerebral Aneurysm Surgery

In order to find out the effect of induced hypotension and temporary clipping during aneurysmal surgery on postoperative patients, we analysed 143 cases who had received surgery from September, 1982 to April, 1988. We divided these surgical cases into two groups, those without temporary clipping and those with temporary clipping during surgery, excluding cases of definite surgical complications. Of the patients in the non-temporary clipping group, we evaluated the relationship between the degree of the mean blood pressure(MBP) during surgery with the postoperative conduction of the patients according to the preoperative clinical grade. Of those in the temporary clipping group, we also evaluated the relationship between the degree of the MBP, site and duration of the temporary clipping during surgery with the postoperative condition of the patients according to preoperaitve clinical grades. The rate of temporary deterioration, delayed sequela and death, possibly from induced hypotension or the temporary clipping procedure, was higher in those whom the MBP was lowered to 60 mmHg during surgery than in those whom the MBP was maintained at 80 mmHg and 70 mmHg(temporary deterioration : 27.3% vs. 23.1% vs. 13.3%, delayed sequela : 4.5% vs. 0.0% vs. 0.0%, and death : 9.1% vs. 0.0% vs. 3.3%, respectively in non-temporary clipping group and temporary deterioration : 33.3% vs. 22.2% vs. 21.1%, and death : 22.2% vs. 0.0% vs. 10.5%, respectively in temporary clipping group). In the non-temporary clipping group, preoperative clinical grades 1,2 and 3 patients did not deteriorate until after 20 minutes of hypotension(MBP : < or = 60 mmHg). However, patients of preoperative clinical grade 4 and 5 showed temporary deterioration after 10 minutes of hypotension(MBP : < or = 60 mmHg). There was no deterioration in patients whom the duration of the temporary clipping was within 15 minutes at an intracranial internal carotid artery and a middle cerebral artery at various MBP's, but, in the cases who had a temporary clipping at the anterior cerebral artery, the safety duration of the temporary clipping was 15 minutes at 80 mmHg, 7 minutes at 70 mmHg and 3 minutes at 60 mmHg of the MBP. Induced hypotension during aneurysmal surgery had some risk and it increased in hypertensive, poor clinical grade patients, and when the MBP was lowered to 60 mmHg. The safety duration of a temporary clipping might be increased with the raising of the MBP or administration of a brain protective agent at the time of the temporary clipping during surgery.