Early Goal-directed Therapy During Endovascular Coiling Procedures Following Aneurysmal Subarachnoid Hemorrhage: A Pilot Prospective Randomized Controlled Study.

BACKGROUND: Maintenance of euvolemia and cerebral perfusion are recommended for the prevention of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). We conducted a pilot randomized controlled study to assess the feasibility and efficacy of goal-directed therapy (GDT) to correct fluid and hemodynamic derangements during endovascular coiling in patients with aSAH. METHODS: This study was conducted between November 2015 and February 2019 at a single tertiary center in Canada. Adult patients with aSAH within 5 days of aneurysm rupture were randomly assigned to receive either GDT or standard therapy during endovascular coiling. The incidence of dehydration at presentation and the efficacy of GDT were evaluated. RESULTS: Forty patients were allocated to receive GDT (n=21) or standard therapy (n=19). Sixty percent of all patients were found to have dehydration before the coiling procedure commenced. Compared with standard therapy, GDT reduced the duration of intraoperative hypovolemia (mean difference 37.6 [95% confidence interval, 6.2-37.4] min, P=0.006) and low cardiac index (mean difference 30.7 [95% confidence interval, 9.5-56.9] min, P=0.035). There were no differences between the 2 treatment groups with respect to the incidence of vasospasm, stroke, death, and other complications up to postoperative day 90. CONCLUSIONS: A high proportion of aSAH patients presented at the coiling procedure with dehydration and a low cardiac output state; these derangements were more likely to be corrected if the GDT algorithm was used. Compared with standard therapy, use of the GDT algorithm resulted in earlier recognition and more consistent treatment of dehydration and hemodynamic derangement during endovascular coiling.

Continuous bilateral subomohyoid suprascapular nerve blocks for postoperative analgesia for bilateral rotator cuff repair: a case report.

PURPOSE: Blocking the suprascapular nerve under the inferior belly of the omohyoid muscle is a novel regional anesthesia technique that has been proposed for shoulder analgesia. We describe the use of and our experience with bilateral indwelling suprascapular catheters for pain management via continuous infusions in a patient undergoing bilateral shoulder surgery. CLINICAL FEATURES: Bilateral subomohyoid suprascapular catheters were inserted prior to surgery for postoperative analgesia in a patient undergoing bilateral rotator cuff tear repair. The catheters were placed 0.5-1 cm beyond the needle tip, and low local anesthetic infusion rates (ropivacaine 0.2% at 5 mL·hr-1 on each side) were used. CONCLUSIONS: Judicious use of preoperatively placed bilateral suprascapular catheters added to a comprehensive multimodal analgesic regimen provided excellent analgesia without respiratory compromise throughout the perioperative course.

RéSUMé: OBJECTIF: Une nouvelle technique d'anesthésie régionale proposée pour l'analgésie de l'épaule consiste à bloquer le nerf suprascapulaire sous la partie inférieure du muscle omohyoïdien. Nous décrivons l'utilisation et notre expérience avec des cathéters suprascapulaires bilatéraux pour la prise en charge de la douleur par l'intermédiaire de perfusions continues chez un patient subissant une chirurgie bilatérale des épaules. ÉLéMENTS CLINIQUES: Des cathéters suprascapulaires sous-omohyoïdiens bilatéraux ont été insérés avant la chirurgie pour l'analgésie postopératoire d'un patient subissant une réparation bilatérale de rupture de la coiffe des rotateurs. Les cathéters ont été positionnés 0,5-1 cm au-delà de l'extrémité de l'aiguille, et de faibles quantités d'anesthésique local (ropivacaine 0,2 % à 5 mL·h−1 de chaque côté) ont été utilisées. CONCLUSION: L'utilisation judicieuse de cathéters suprascapulaires bilatéraux installés en période préopératoire, ajoutée à un régime analgésique multimodal exhaustif, a procuré une excellente analgésie sans atteinte respiratoire tout au long de la période périopératoire.

The Effects of Intraoperative Sedation on Surgical Outcomes of Deep Brain Stimulation Surgery.

BACKGROUND: Intraoperative sedation is often used to facilitate deep brain stimulation (DBS) surgery; however, these sedative agents also suppress microelectrode recordings (MER). To date, there have been no studies that have examined the effects of differing sedatives on surgical outcomes and the success of DBS surgery. METHODS: We performed a retrospective study to evaluate the effect of differing sedative agents on postoperative surgical outcomes at 6 months in parkinsonian adult patients who underwent DBS surgery, from January 2004 through December 2014, at one academic center. Surgical outcomes of DBS were evaluated using a simplified Unified Parkinson Diseases Rating Score-III and levodopa dose equivalent reduction at baseline and 6 months postoperatively. RESULTS: We analyzed data from 121 of 124 consecutive parkinsonian patients. Propofol, dexmedetomidine, remifentanil, and midazolam were used individually or in combination. All sedatives were routinely discontinued 20 to 30 minutes before MER, in accordance with our institutional protocol. We found no statistically significant association between the use of individual agent or combination of sedative agents and surgical outcomes at 6 months, the success of DBS, duration of MER, duration of stage 1 procedure, and perioperative complications. CONCLUSIONS: Our study showed that the choice of sedative agent was not associated with poor surgical outcomes after DBS surgery using MER and macrostimulation techniques in parkinsonian patients.

An update on the prone position: Continuing Professional Development.

PURPOSE: The purpose of this Continuing Professional Development module is to provide information needed to prepare for and clinically manage a patient in the prone position. PRINCIPAL FINDINGS: Prone positioning is required for surgical procedures that involve the posterior aspect of a patient. We searched MEDLINE(®) and EMBASE™ from January 2000 to January 2015 for literature related to the prone position and retrieved only original articles in English. We reviewed the advantages and disadvantages of various equipment used in prone positioning, the physiological changes associated with prone positioning, and the complications that can occur. We also reviewed strategies for the safe conduct and management of position-related complications. CONCLUSION: Increased age, elevated body mass index, the presence of comorbidities, and long duration of surgery appear to be the most important risk factors for complications associated with prone positioning. We recommend a structured team approach and careful selection of equipment tailored to the patient and surgery. The systematic use of checklists is recommended to guide operating room teams and to reduce prone position-related complications. Anesthesiologists should be prepared to manage major intraoperative emergencies (e.g., accidental extubation) and anticipate postoperative complications (e.g., airway edema and visual loss).

Anestesia para Neurocirugía Mínimamente Invasiva / Anesthesia for minimally invasive neurosurgery

Introduction: Advances in imaging, computing and optics have encouraged the application of minimally invasive surgical approach to a variety of neurosurgical procedures. The advantages include accurate localization of lesions usually inaccessible to conventional surgery, less trauma to healthy brain, blood vessels and nerves, shorter operating time, reduced blood loss, and early recovery and discharge. Nevertheless minimally invasive neurosurgical (MIN) procedures still have potential intra-and post-operative complications that can cause morbidity and mortality. Objectives: The aim of this study was to review and analyze published literature describing experiences in the anesthetic management of the most commonly performed MIN procedures. Materials and methods: Neurosurgical and neuroanesthesia literature (1990-2013) was reviewed and description of anesthetic technique/management and perioperative morbidity/mortality was reported. We also compared the different authors' experience with MIN procedures. Results: The neurosurgical literature dealing with MIN has expanded, but there are few references in relation to anesthetic management. Anesthesia goals remain the same: careful pre-operative assessment and planning, and meticulous cerebral hemodynamic control to ensure adequate cerebral perfusion pressure. The degree of postoperative care depends on local practice, patient factors and postoperative brain imaging.

Introducción: Los avances en la formación de imágenes, la computación y la óptica han alentado la aplicación del enfoque quirúrgico mínimamente invasivo a una variedad de procedimientos neuroquirúrgicos. Las ventajas incluyen la localización exacta de las lesiones generalmente inaccesibles a la cirugía convencional, menos trauma al cerebro sano, vasos sanguíneos y nervios, más corto el tiempo de funcionamiento, la reducción de la pérdida de sangre, la recuperación temprana y el alta. Sin embargo los procedimientos neuroquirúrgicos mínimamente invasivos (NMI) todavía tienen potencial complicaciones intra y post-operatorias que pueden causar morbilidad y mortalidad. Objetivos: El objetivo de este estudio fue revisar y analizar la literatura publicada que describe las experiencias en el manejo anestésico de los procedimientos más comúnmente realizados en NMI. Materiales y métodos: Literatura sobre neurocirugía y neuroanestesia (1990-2013). Revisión y descripción de la técnica anestésica/gestión y morbilidad perioperatoria/mortalidad notificada. Comparación de la experiencia de los diferentes autores en procedimientos de NMI. Resultados: La literatura sobre NMI se ha expandido, pero hay pocas referencias en relación con el manejo anestésico. Las metas anestésicas siguen siendo las mismas: la evaluación preoperatoria cuidadosa y la planificación, el meticuloso control de hemodinámica cerebral para asegurar la presión de perfusión cerebral adecuada. El grado de cuidado postoperatorio depende de la práctica local, factores del paciente y de imagen cerebral postoperatoria.

α-Adrenergic effects on low-frequency oscillations in blood pressure and R-R intervals during sympathetic activation.

The present study was designed to address the contribution of α-adrenergic modulation to the genesis of low-frequency (LF; 0.04-0.15 Hz) oscillations in R-R interval (RRi), blood pressure (BP) and muscle sympathetic nerve activity (MSNA) during different sympathetic stimuli. Blood pressure and RRi were measured continuously in 12 healthy subjects during 5 min periods each of lower body negative pressure (LBNP; -40 mmHg), static handgrip exercise (HG; 20% of maximal force) and postexercise forearm circulatory occlusion (PECO) with and without α-adrenergic blockade by phentolamine. Muscle sympathetic nerve activity was recorded in five subjects during LBNP and in six subjects during HG and PECO. Low-frequency powers and median frequencies of BP, RRi and MSNA were calculated from power spectra. Low-frequency power during LBNP was lower with phentolamine versus without for both BP and RRi oscillations (1.6 ± 0.6 versus 1.2 ± 0.7 ln mmHg(2), P = 0.049; and 6.9 ± 0.8 versus 5.4 ± 0.9 ln ms(2), P = 0.001, respectively). In contrast, the LBNP with phentolamine increased the power of high-frequency oscillations (0.15-0.4 Hz) in BP and MSNA (P < 0.01 for both), which was not observed during saline infusion. Phentolamine also blunted the increases in the LBNP-induced increase in frequency of LF oscillations in BP and RRi. Phentolamine decreased the LF power of RRi during HG (P = 0.015) but induced no other changes in LF powers or frequencies during HG. Phentolamine resulted in decreased frequency of LF oscillations in RRi (P = 0.004) during PECO, and a similar tendency was observed in BP and MSNA. The power of LF oscillation in MSNA did not change during any intervention. We conclude that α-adrenergic modulation contributes to LF oscillations in BP and RRi during baroreceptor unloading (LBNP) but not during static exercise. Also, α-adrenergic modulation partly explains the shift to a higher frequency of LF oscillations during baroreceptor unloading and muscle metaboreflex activation.

Anaesthesia for endoscopic neurosurgical procedures.

PURPOSE OF REVIEW: Endoscopic neurosurgical procedures are becoming more frequent and popular in the treatment of intracranial disease. When endoscopy involves the intraventricular structures, irrigating solutions are required and may contribute to sudden and sharp increases in intracranial pressure. More recently, nasal endoscopic approach has been used to perform skull base surgery for aneurysms and tumours. We have analysed published articles in order to detect anaesthesia management and perioperative complications. RECENT FINDINGS: Sudden and dangerously low decreases in cerebral perfusion pressures do not provoke the 'traditional Cushing's response' usually associated with significantly high intracranial pressure. It is important to note that tachycardia (not bradycardia) and/or hypertension are the most frequent haemodynamic complications during neuroendoscopic procedures. With the transnasal approach severe intraoperative haemorrhage is the most important complication to consider followed by direct injury to surrounding neural structures. SUMMARY: Invasive arterial blood pressure and intracranial pressure should be measured continuously during neuroendoscopies to detect early intraoperative cerebral ischaemia instead of waiting for the appearance of bradycardia which may be a late sign. General anaesthesia remains the technique of choice. Intracranial haemorrhage increases the likelihood of perioperative complications. Close postoperative monitoring is required to diagnose and treat complications such as convulsions, persistent hydrocephalus, haemorrhage or electrolytic imbalance.

Neurogenic-nitric oxide interactions affecting brachial artery mechanics in humans: roles of vessel distensibility vs. diameter.

The purpose of this investigation was to assess the interactive influence of sympathetic activation and supplemental nitric oxide (NO) on brachial artery distensibility vs. its diameter. It was hypothesized that 1) sympathetic activation and NO competitively impact muscular conduit artery (brachial artery) mechanics, and 2) neurogenic constrictor input affects conduit vessel stiffness independently of outright changes in conduit vessel diastolic diameter. Lower body negative pressure (LBNP) and a cold pressor stress (CPT) were used to study the changes in conduit vessel mechanics when the increased sympathetic outflow occurred with and without changes in heart rate (LBNP -40 vs. -15 mmHg) and blood pressure (CPT vs. LBNP). These maneuvers were performed in the absence and presence of nitroglycerin. Neither LBNP nor CPT altered brachial artery diastolic diameter; however, distensibility was reduced by 25 to 54% in each reflex (all P < 0.05). This impact of sympathetic activation on brachial artery distensibility was not altered by nitroglycerin supplementation (21-54%; P < 0.05), although baseline diameter was increased by the exogenous NO (P < 0.05). The results indicate that sympathetic excitation can reduce the distensibility of the brachial artery independently of concurrent changes in diastolic diameter, heart rate, and blood pressure. However, exogenous NO did not minimize or reverse brachial stiffening during sympathetic activation. Therefore, sympathetic outflow appears to impact the stiffness of this conduit vessel rather than its diastolic diameter or, by inference, its local resistance to flow.

Does hyperventilation improve operating condition during supratentorial craniotomy? A multicenter randomized crossover trial.

BACKGROUND: Hyperventilation has been an integral, but poorly validated part of neuroanesthetic practice. We conducted a two-period, crossover, randomized trial to evaluate surgeon-assessed brain bulk and measured intracranial pressure (ICP) in patients undergoing craniotomy for removal of supratentorial brain tumors during moderate hypocapnia or normocapnia. METHODS: Two-hundred and seventy-five adult patients with supratentorial brain tumors were randomized to one of two treatment sequences: hyperventilation (arterial carbon dioxide tension, PaCO2 = 25 +/- 2 mm Hg) followed by normoventilation (PaCO2 = 37 +/- 2 mm Hg) or normoventilation followed by hyperventilation. Ventilation and end-tidal CO2 tension were kept constant for 20 min. Patients were also randomly assigned to receive a propofol infusion or isoflurane anesthesia. At the end of each study period, subdural ICP was measured and the neurosurgeon, blinded to the treatment group, was asked to rate the brain bulk using a four-point scale. RESULTS: Using a generalized estimation equation model, we found that hyperventilation decreased the risk of increased brain bulk by 45%, P = 0.004, 95% confidence intervals 22% to 61%, and the number needed to treat was 8. The mean (+/-SD) ICP during hyperventilation, 12.3 +/- 8.1 mm Hg, was lower than that during normoventilation, 16.2 +/- 9.6 mm Hg, P < 0.001. Anesthetic regimen did not affect brain bulk assessment or ICP. CONCLUSIONS: In patients with supratentorial brain tumors, intraoperative hyperventilation improves surgeon-assessed brain bulk which was associated with a decrease in ICP.

Cervical spine motion: a fluoroscopic comparison of Shikani Optical Stylet vs Macintosh laryngoscope.

PURPOSE: The optimal technique to manage the airway in patients presenting with a potential or documented cervical spine (C-spine) injury remains unresolved. Using fluoroscopic video assessment, C-spine motion during laryngoscopy with a Shikani Optical Stylet (SOS) was compared to C-spine motion during intubation using a Macintosh blade. METHODS: Twenty-four healthy surgical patients gave written consent to participate in a crossover randomized controlled trial; all patients were subjected to both Macintosh and Shikani laryngoscopy with manual inline stabilization following induction of anesthesia. The C-spine motion was examined at four areas: the occiput-C1 junction, C1-C2 junction, C2-C5 motion segment, and C5-thoracic motion segment. The time required for laryngoscopy was also measured (duration > 120 sec was deemed a failure of the laryngoscopy technique). RESULTS: On average, C-spine motion was 52% less (P < 0.02) at three of the motion segments studied, occiput-C1, C2-C5, and C5-thoracic when comparing SOS vs Macintosh laryngoscopy. There was no difference between techniques at the C1-C2 segment. Laryngoscopy with SOS (28 +/- 17 sec) took longer than with Macintosh blade (17 +/- 7 sec), P < 0.01. There were two failures out of 23 using the SOS, vs none with the Macintosh blade. CONCLUSION: For patients in whom C-spine movement is undesirable, use of the SOS may limit neck movement, while modestly increasing the time required to intubate, and/or the risk of procedure failure.

Cervical spine motion: a fluoroscopic comparison during intubation with lighted stylet, GlideScope, and Macintosh laryngoscope.

The question of which is the optimum technique to intubate the trachea in a patient who may have a cervical(C)-spine injury remains unresolved. We compared, using fluoroscopic video, C-spine motion during intubation for Macintosh 3 blade, GlideScope, and Intubating Lighted Stylet, popularly known as the Lightwand or Trachlight. Thirty-six healthy patients were randomized to participate in a crossover trial of either Lightwand or GlideScope to Macintosh laryngoscopy, with in-line stabilization. C-spine motion was examined at the Occiput-C1 junction, C1-2 junction, C2-5 motion segment, and C5-thoracic motion segment during manual ventilation via bag-mask, laryngoscopy, and intubation. Time to intubate was also measured. C-spine motion during bag-mask ventilation was 82% less at the four motion segments studied than during Macintosh laryngoscopy (P < 0.001). C-spine motion using the Lightwand was less than during Macintosh laryngoscopy, averaging 57% less at the four motion segments studied (P < 0.03). There was no significant difference in time to intubate between the Lightwand and the Macintosh blade. C-spine motion was reduced 50% at the C2-5 segment using the GlideScope (P < 0.04) but unchanged at the other segments. Laryngoscopy with GlideScope took 62% longer than with the Macintosh blade (P < 0.01). Thus, the Lightwand (Intubating Lighted Stylet) is associated with reduced C-spine movement during endotracheal intubation compared with the Macintosh laryngoscope.

Extracorporeal femoral to carotid artery perfusion in selective brain cooling for a giant aneurysm. Case report.

Giant partially thrombosed intracranial aneurysms are a challenge to treat surgically, and they are also unsuitable for coil embolization. The current options for treatment include extracranial-intracranial bypass followed by parent artery occlusion or direct surgical occlusion in which deep hypothermic circulatory arrest is used. The authors report the use of another approach in the treatment of a giant anterior circulation aneurysm: selective brain cooling accomplished by extracorporeal perfusion. This facilitated direct surgery on a 4.2-cm, partially thrombosed aneurysm of the middle cerebral artery (MCA). A brain temperature of 22 degrees C was achieved after 20 minutes of perfusion with blood cooled using an extracorporeal technique of femoral-common carotid artery perfusion. This was followed by a 20-minute period of surgical trapping of the MCA, then evacuation and clip occlusion of the aneurysm. During the period of selective brain cooling the patient's core body temperature was maintained above 35 degrees C. This technique of selective brain cooling may be a useful alternative to currently available surgical and endovascular methods of treatment for giant aneurysms.

The comparative effects of desflurane and isoflurane on lumbar cerebrospinal fluid pressure in patients undergoing craniotomy for supratentorial tumors.

UNLABELLED: We compared the effects of desflurane and isoflurane on cerebral perfusion pressure (CPP), lumbar cerebrospinal fluid pressure (LCSFP), and mean arterial blood pressure (MAP) in patients anesthetized with desflurane or isoflurane undergoing craniotomy for supratentorial mass lesions. Additionally, emergence from anesthesia was examined to determine if neurologic function could be assessed earlier after isoflurane or desflurane anesthesia. Thirty-six patients were randomized to receive either desflurane or isoflurane for maintenance of anesthesia at 1.2 minimum alveolar concentration (MAC). Patients were hyperventilated (PaCO(2), 30 +/- 2 mm Hg) after baseline LCSFP was obtained via the subarachnoid catheter. At a MAC of 1.2, mean LCSFP was not statistically different between the two study groups either before or after hyperventilation. Additionally, CPP was not significantly different between the two groups. Finally, patient's time to respond to commands was 50% shorter in the desflurane group (30 +/- 36 min) (mean +/- SD) when compared with the isoflurane group (72 +/- 126 min); however, this was not significant (P = 0.17). In patients undergoing craniotomy for supratentorial mass lesions, desflurane and isoflurane have similar effects on CPP and MAP. Additionally, desflurane in the setting of hyperventilation does not cause significant changes in LCSFP. IMPLICATIONS: This is the largest study to date comparing the effects of desflurane and isoflurane on patients undergoing craniotomy for supratentorial mass lesion with evidence of midline shift or edema. Neither desflurane nor isoflurane significantly altered lumbar cerebrospinal fluid pressure when moderate hypocapnia was maintained.

Endoscopic and stereotactic neurosurgery.

PURPOSE OF REVIEW: Review of the anesthetic considerations for neuroendoscopy and stereotactic procedures. RECENT FINDINGS: Minimally invasive procedures are increasingly applied in novel ways in the diagnosis and treatment of neurological pathologies. Endoscopic third ventriculostomy, endoscopic shunt revisions and drainage of intraventricular hematoma using a neuroendoscope have become routine neurosurgical procedures. Stereotaxis has expanded its scope from simple brain biopsy to functional neurosurgery and psychiatry. While these procedures are 'minimally invasive', perioperative critical events may still occur. SUMMARY: Vigilance in preoperative assessment and intraoperative monitoring is essential in minimizing perioperative morbidity and mortality in patients undergoing neuroendoscopic and stereotactic procedures.

Anaesthesia for minimally invasive neurosurgery.

Technological advances in imaging, computing and surgical instrumentation have encouraged the application of minimally invasive surgical techniques to various neurosurgical disorders. This chapter discusses the wide application of neurosurgery and the implications for anaesthesia, focusing on the specific anaesthetic considerations for neuroendoscopy, stereotactic procedures and radiosurgery.

Cerebral blood volume and blood flow responses to hyperventilation in brain tumors during isoflurane or propofol anesthesia.

UNLABELLED: Using computerized tomography, we measured absolute cerebral blood flow (CBF) and cerebral blood volume (CBV) in tumor, peri-tumor, and contralateral normal regions, at normocapnia and hypocapnia, in 16 rabbits with brain tumors (VX2 carcinoma), under isoflurane or propofol anesthesia. In both anesthetic groups, CBV and CBF were highest in the tumor region and lowest in the contralateral normal tissue. For isoflurane, a significant decrease in both CBV and CBF was observed in all tissue regions with hyperventilation (P < 0.05), but without accompanying changes in intracranial pressure. However, the percent reduction in regional CBF with hypocapnia was two times larger than that observed in the CBV response (P < 0.01). In contrast, there were no significant changes in CBV and CBF in the Propofol group with hyperventilation for all regions (P > 0.10). In addition, there were no differences between CBV values for isoflurane at hypocapnia when compared with CBV values for propofol at normo- or hypocapnia (P > 0.34 and P > 0.35, respectively, in the tumor regions). Our results indicate that propofol increases cerebral vascular tone in both neoplastic and normal tissue vessels compared with isoflurane. CBV and CBF during normocapnia were significantly greater in all regions (tumor, peri-tumor, and contralateral normal tissue) with isoflurane than with propofol. CBV and CBF remained responsive to hyperventilation only with isoflurane. IMPLICATIONS: In rabbits with brain tumors, brain blood flow and volume were significantly larger in all regions (tumor, peri-tumor, and contralateral normal tissue) with isoflurane than with propofol during normocapnia, and remained responsive to a reduction in PaCO(2). Consequently, during hypocapnia, brain blood flow and volume values with isoflurane were similar to values with propofol.

Sedative doses of remifentanil have minimal effect on ECoG spike activity during awake epilepsy surgery.

The use of remifentanil for sedation during awake epilepsy surgery has been described in a case report. However, little information is available regarding the effect of remifentanil on the quality of intraoperative electrocorticography (ECoG). This study was designed to investigate the effect of sedative doses of remifentanil on ECoG interictal spike activity among patients undergoing awake anterior temporal lobectomy for refractory epilepsy. Ten adult patients were studied prospectively. After baseline EcoG recordings were obtained, remifentanil was administered as a continuous infusion at 0.1 microg/kg/min and the ECoG recorded continuously for 15 minutes. Recordings obtained before and during the administration of remifentanil were compared with respect to spike frequency and location. A trend toward a small decrease in spike frequency was observed as patients became increasingly somnolescent and background ECoG activity slowed. The difference was not statistically significant. Blood pressure and heart rate were not adversely affected by the administration of remifentanil. Respiratory rates decreased in all patients (mean decrease, 8 breaths/min) and one patient transiently developed a respiratory rate of 4 breaths per minute that elicited a decrease in the rate of remifentanil administration. Remifentanil administered at sedation doses does not adversely affect intraoperatively recorded interictal spike activity. Further investigation of the use of this drug during awake epilepsy surgery is warranted.