Irene Rozet

Dexmedetomidine sedation during awake craniotomy for seizure resection: effects on electrocorticography.

Patients with refractory seizures may undergo awake craniotomy and cortical resection of the seizure area, using intraoperative functional mapping and electrocorticography (ECoG). We used dexmedetomidine in 6 patients, transitioning successively from the asleep-awake-asleep method, through a combined propofol/dexmedetomidine sedative infusion, to dexmedetomidine as the only sedation. Initial experience with the asleep-awake-asleep method in 2 patients was successful with the replacement of propofol/laryngeal mask anesthesia, 20 to 30 minutes before ECoG testing, by dexmedetomidine infusion, maintained at 0.2 mcg kg−1 h−1 throughout neurocognitive testing. Propofol anesthesia was reintroduced for resection. One patient received combined dexmedetomidine (0.2 mcg kg−1 h−1) and propofol (200 mcg kg−1 min−1) infusions for sedation. Both infusions were stopped 15 minutes before ECoG. Subsequently, they were restarted and the epileptic foci resected. Three patients received dexmedetomidine as the sole sedative agent, together with scalp block local anesthesia, and incremental boluses totaling 150 to 175 mcg of fentanyl per case. Dexmedetomidine was started with 0.3 mcg kg−1 boluses and maintained with 0.2 to 0.7 mcg kg−1 h−1 for craniotomy, testing, and resection. The infusion was paused for 20 minutes in 1 patient to allow improvement in neurocognitive testing. This occurred within 10 minutes. All patients enjoyed good hemodynamic control, with blood pressure maintained within 20% of initial values, and made uneventful recoveries. The surgical conditions were all reported as favorable. Dexmedetomidine can be used singly for sedation in awake craniotomy requiring ECoG. Individual dose ranges vary, but a bolus of 0.3 mcg kg−1 with an infusion of 0.2 mcg kg−1 min−1 is a good starting point, allowing accurate mapping of epileptic foci and subsequent resection.

Clinical experience with dexmedetomidine for implantation of deep brain stimulators in Parkinson's disease

The pharmacologic profile of the α-2 agonist dexmedetomidine (Dex) suggests that it may be an ideal sedative drug for deep brain stimulator (DBS) implantation. We performed a retrospective chart review of anesthesia records of patients who underwent DBS implantation from 2001 to 2004. In 2003, a clinical protocol with Dex sedation for DBS implantation was initiated. Demographic data, use of antihypertensive medication, and duration of mapping were compared between patients who received Dex (11 patients/13 procedures) and patients who did not receive any sedation (controls: 8 patients/9 procedures). There were no differences in severity of illness between the two groups. Dex provided patient comfort and surgical satisfaction with mapping in all cases, and significantly reduced the use of antihypertensive medication (54% in the Dex group, versus 100% in controls, P = 0.048). In DBS implantation, sedation with Dex did not interfere with electrophysiologic mapping, and provided hemodynamic stability and patient comfort. Routine use of Dex in these procedures may be indicated.

Anesthesia for functional neurosurgery: the role of dexmedetomidine.

Purpose of review The purpose of this review is to summarize current approaches to the anesthetic management of functional neurosurgery and to describe the application of an α-2-adrenergic agonist dexmedetomidine in the anesthetic management of functional neurosurgical procedures. Recent findings Dexmedetomidine, an α-2-adrenergic agonist, causes a unique kind of sedation, acting on the subcortical areas, which resembles natural sleep without respiratory depression. Experimental data demonstrate both cerebral vasoconstriction and vasodilatation, depending on the model and dose studied. At the clinically relevant doses, dexmedetomidine decreases cerebral blood flow and cerebral metabolic rate of oxygen in healthy volunteers. Clinical experience of dexmedetomidine use in functional neurosurgery is limited to small case-series. Nevertheless, these reports indicate that use of dexmedetomidine does not interfere with electrophysiologic monitoring, thus allowing brain mapping during awake craniotomy and microelectrode recording during implantation of deep-brain stimulators. Summary Dexmedetomidine has been demonstrated to provide a successful sedation without impairment of electrophysiologic monitoring in functional neurosurgery. Prospective randomized studies are warranted to delineate an optimal regimen of dexmedetomidine sedation and any dose-related influence on neurophysiologic function.

Gender Differences in Cerebral Blood Flow Velocity and Autoregulation between the Anterior and Posterior Circulations in Healthy Children

There is little information on gender differences in cerebral autoregulation. The purpose of this study was to compare autoregulation of the anterior and posterior circulations using the tilt test method in healthy boys and girls who were 10–16 y of age. Transcranial Doppler was used to measure middle cerebral artery and basilar artery flow velocities (Vmca and Vbas). Cerebral autoregulation (ARI) of the middle cerebral (ARImca) and basilar arteries (ARIbas) was examined using the tilt test method. An ARI <0.4 indicates impaired autoregulation. Among the 13 boys and 13 girls, Vmca and Vbas were higher in girls. All children demonstrated intact autoregulation, but boys had higher ARImca than girls, whereas girls had higher ARIbas than boys. Girls demonstrated greater autoregulation in the basilar artery, whereas boys demonstrated greater autoregulation in the middle cerebral artery. Girls had higher flow velocities in both vessels. This study provides normative data on cerebral autoregulation of the posterior circulation in healthy, awake boys and girls.

Effect of Equiosmolar Solutions of Mannitol versus Hypertonic Saline on Intraoperative Brain Relaxation and Electrolyte Balance

Background:The purpose of the study was to compare the effect of equiosmolar solutions of mannitol and hypertonic saline (HS) on brain relaxation and electrolyte balance. Methods:After institutional review board approval and informed consent, patients with American Society of Anesthesiologists physical status II–IV, scheduled to undergo craniotomy for various brain pathologies, were enrolled into this prospective, randomized, double-blind study. Patients received 5 ml/kg 20% mannitol (n = 20) or 3% HS (n = 20). Partial pressure of carbon dioxide in arterial blood was maintained at 35–40 mmHg, and central venous pressure was maintained at 5 mmHg or greater. Hemodynamic variables, fluid balance, blood gases, electrolytes, lactate, and osmolality (blood, cerebrospinal fluid, urine) were measured at 0, 15, 30, and 60 min and 6 h after infusion; arteriovenous difference of oxygen, glucose, and lactate were calculated. The surgeon assessed brain relaxation on a four-point scale (1 = relaxed, 2 = satisfactory, 3 = firm, 4 = bulging). Appropriate statistical tests were used for comparison; P < 0.05 was considered significant. Results:There was no difference in brain relaxation (mannitol = 2, HS = 2 points; P = 0.8) or cerebral arteriovenous oxygen and lactate difference between HS and mannitol groups. Urine output with mannitol was higher than with HS (P < 0.03) and was associated with higher blood lactate over time (P < 0.001, compared with HS). Cerebrospinal fluid osmolality increased at 6 h in both groups (P < 0.05, compared with baseline). HS caused an increase in sodium in cerebrospinal fluid over time (P < 0.001, compared with mannitol). Conclusion:Mannitol and HS cause an increase in cerebrospinal fluid osmolality, and are associated with similar brain relaxation scores and arteriovenous oxygen and lactate difference during craniotomy.

The neuroprotective effects of oxaloacetate in closed head injury in rats is mediated by its blood glutamate scavenging activity: evidence from the use of maleate.

Introduction Treatment with oxaloacetate after traumatic brain injury has been shown to decrease blood glutamate levels and protect against the neurotoxic effects of glutamate on the brain. A number of potential mechanisms have been suggested to explain oxaloacetate-induced neuroprotection. We hypothesize that the primary mechanism by which intravenous oxaloacetate provides neuroprotection is by activation of the blood glutamate-scavenging enzyme glutamate-oxaloacetate transaminase, increasing thereby the driving force for the efflux of excess glutamate from brain interstitial fluids into blood. If so, coadministration of maleate, a glutamate-oxaloacetate transaminase-blocker is expected to prevent the neuroprotective effects of oxaloacetate. Materials and Methods A neurological severity score (NSS) was measured 1 hour after closed head injury (CHI) in rats. Then, rats received 30 μL/min/100 g infusion of saline, or 1 mmol/100 g solution of oxaloacetate, maleate, or a mixture of oxaloacetate and maleate. NSS was reassessed at 24 and 48 hour after CHI. Blood glutamate and glucose levels were measured at 0, 60, 90, and 120 minutes. Results NSS improved significantly at 24 hour (P<0.001) and 48 hour (P<0.001) only in the rats treated with oxaloacetate. Blood glutamate decreased significantly in the oxaloacetate-treated group at 90 minute (at the conclusion of oxaloacetate administration) (P<0.00001), but not in the control, maleate or oxaloacetate+maleate groups. A strong correlation r2=0.86 was found to exist between the percent decrease in blood glutamate levels and percent improvement in NSS. Discussion The results of this study demonstrate that the primary mechanism by which oxaloacetate provides neuroprotective activity after CHI is related to its blood glutamate scavenging activity. Management of blood glutamate concentration may have important implications in the treatment of acute brain conditions, including CHI and stroke.

Cerebral Autoregulation and Co2 Reactivity in Anterior and Posterior Cerebral Circulation During Sevoflurane Anesthesia

The purpose of the study was to compare cerebral autoregulation (CA) and CO2 reactivity (CO2R) between the anterior and posterior circulation under sevoflurane anesthesia. We studied 9 adult ASA physical status I patients (22–47 yr) scheduled for elective orthopedic surgery. Blood flow velocity in the middle cerebral artery (Vmca) and in the basilar artery (Vba) were measured using transcranial Doppler ultrasonography. For CA testing, arterial blood pressure was increased using phenylephrine infusion. CA was quantified with the autoregulatory index (ARI). CO2R was investigated at Paco2 of 30 ± 2.8 mm Hg, 39.4 ± 2.6 mm Hg, and 48.7 ± 2.8 mm Hg. Linear regression analysis was used for CO2R. We found ARI was preserved in both arteries: ARImca (middle cerebral artery) = 0.72 ± 0.2; ARIba (basilar artery) = 0.66 ± 0.2; P = 0.5. With regard to CO2R, Vmca increased with slope of 1.7 cm/s/mm Hg Paco2, Vba increased with slope of 1.5 cm/s/mm Hg Paco2; P = 0.83. Absolute Vmca was higher compared with Vba; P < 0.05. We conclude that in healthy individuals under 0.5 MAC of sevoflurane and small-dose remifentanil: 1) mean flow velocities of BA are less than those of MCA; 2) autoregulation and CO2R are preserved in the basilar artery and are similar to those of MCA.

Preoperative opioid use is associated with early revision after total knee arthroplasty a study of male patients treated in the veterans affairs system

Background: Opioid use is endemic in the U.S. and is associated with morbidity and mortality. The impact of long-term opioid use on joint-replacement outcomes remains unknown. We tested the hypothesis that use of opioids is associated with adverse outcomes after total knee arthroplasty (TKA). Methods: We performed a retrospective analysis of patients who had had TKA within the U.S. Veterans Affairs (VA) system over a 6-year period and had been followed for 1 year postoperatively. The length of time for which an opioid had been prescribed and the morphine equivalent dose were calculated for each patient. Patients for whom opioids had been prescribed for >3 months in the year prior to the TKA were assigned to the long-term opioid group. A natural language processing-based machine-learning classifier was developed to classify revisions due to infectious and non-infectious causes on the basis of the postoperative note. Survival curves for the time to knee revision or manipulation were used to compare the long-term opioid group with the patients who did not take opioids long-term. Hazard and odds ratios for knee revision and manipulation were obtained as well. Results: Of 32,636 patients (94.4% male; mean age [and standard deviation], 64.45 ± 9.41 years) who underwent TKA, 12,772 (39.1%) were in the long-term opioid group and 734 (2.2%) had a revision within a year after the TKA. Chronic kidney disease, diabetes, and long-term opioid use were associated with revision within 1 year—with odds ratios (95% confidence intervals [CIs]) of 1.76 (1.37 to 2.22), 1.11 (0.93 to 1.31), and 1.40 (1.19 to 1.64), respectively—and were also the leading factors associated with a revision at any time after the index TKA—with odds ratios (95% CIs) of 1.61 (1.34 to 1.92), 1.21 (1.08 to 1.36), and 1.28 (1.15 to 1.43), respectively. Long-term opioid use had a hazard ratio of 1.19 (95% CI = 1.10 to 0.24) in the analysis of its relationship with knee revision, but the hazard was not significant in the analysis of its association with knee manipulation. The accuracy of the text classifier was 0.94, with the area under the receiver operating characteristic curve being 0.99. There was no association between long-term use of opioids and the specific cause for knee revision. Conclusions: Long-term opioid use prior to TKA was associated with an increased risk of knee revision during the first year after TKA among predominantly male patients treated in the VA system. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Prolonged opioid use after knee arthroscopy in military veterans

BACKGROUND:Chronic postoperative pain occurs with an appreciable incidence after elective surgery. Known risk factors include perioperative pain and posttraumatic stress disorder (PTSD). Military veterans are a population at particular risk for PTSD and hence may be at increased risk for chronic pain after surgery. Our goal was to identify risk factors for chronic postoperative pain in young veterans after minor elective surgery, including the contribution of PTSD. METHODS:We reviewed the medical and pharmacy records of veterans (18–50 years old), undergoing elective knee arthroscopy from 2007 to 2010 at the Veteran’s Administration Puget Sound Health Care System. The data included demographics, ASA physical status class, comorbidities, anesthesia medications, and opioid prescriptions starting 3.5 months before surgery and ending 3.5 months after surgery. We documented the presence of PTSD based on either the patient’s problem list or the clinical notes. We used prolonged postoperative opioid prescription longer than 3 months after surgery as a surrogate for chronic postoperative pain. RESULTS:We identified 145 patients who met inclusion criteria. The median age was 39 ± 8 years old. Eighty-seven percent of the patients were men. The prevalence of PTSD was 32% (95% confidence interval, 25%–41%). PTSD was associated with increased incidence of smoking (P = 0.009) and preoperative opioid use (P = 0.0006). Preoperative opioids were prescribed in 44% (63 of 145) of the patients: in 64% (30 of 47) of patients with PTSD, compared with 34% (33 of 98) in patients without PTSD (P = .0006). Chronic postoperative pain was identified in 30% (43 of 145) of patients. The strongest independent predictor of chronic postoperative pain was an opioid prescription before surgery (odds ratio = 65.3; 95% confidence interval, 014.5–293.0). In patients older than 27.5 years who did not receive opioids before surgery, PTSD may also have been a risk factor for chronic postoperative pain. CONCLUSIONS:This single-center retrospective study suggests that the most important predictor of chronic postoperative pain is preoperative opioid use. For patients not taking opioids preoperatively, PTSD may increase the risk of prolonged postoperative opioid prescriptions and chronic postoperative pain, potentially related to patient age.

Subarachnoid lumbar drains: A case series of fractured catheters and a near miss

PurposeLumbar subarachnoid catheters for cerebrospinal fluid (CSF) drainage (lumbar drains) are indicated for several medical and surgical conditions. A number of complications can occur from the placement of this type of catheter, including catheter breakage from excessive traction or shearing over the Tuohy needle.Clinical featuresFive cases of lumbar subarachnoid catheter breakage/shearing and catheter fragment retention, as well as one near miss, were identified over a one-year period at a single institution. All (n = 6) patients were undergoing neurosurgical procedures. Four patients required surgical retrieval of the catheter fragments. No patient experienced log-term neurological sequelae.DiscussionFrom these experiences, the following risks factors for catheter rupture are identified: 1) intentional or accidental retraction of the catheter through the needle during placement; 2) faulty use of the guidewire; or 3) use of excessive force during removal of the catheter. Methods to prevent such complications are suggested, including minimal use, or complete avoidance of a guidewire.RésuméObjectifLes cathéters lombaires sous-arachnoïdiens pour le drainage (drains lombaires) du liquide céphalorachidien (LCR) sont indiqués pour de nombreuses conditions médicales et chirurgicales. Un nombre de complications peut survenir lors du positionnement de ce type de cathéter, y compris un bris de cathéter dû à une traction excessive ou à un cisaillement de l’aiguille Tuohy.Éléments cliniquesCinq cas de brisldsaillement de cathéter lombaire sous-arachnoïdien et de rétention de fragment de cathéter, ainsi qu’un « near miss», ont été identifiés au cours d’une période d’une année dans une seule institution. Tous les patients (n = 6) subissaient des procédures neurochirurgicales. Quatre patients ont nécessité une récupération chirurgicale des fragments de cathéter. Aucun patient n’a souffert de séquelles neurologiques a long terme.DiscussionNous avons pu identifier les facteurs de risque suiv-ants pour le bris de cathéter suite à ces expériences : 1) rétraction intentionnelle ou accidentelle du cathéter à travers l’aiguille pendant le positionnement; 2) mauvais usage du fil guide; ou 3) utilisation de force excessive pendant l’extraction du cathéter. Certaines méthodes afin de prévenir de telles complications sont suggérées, y compris une utilisation minimale, voire nulle, du fil guide.