Lashmi Venkatraghavan

Anesthesia considerations for patients with an implanted deep brain stimulator undergoing surgery: a review and update.

PurposeDeep brain stimulation (DBS) can be an effective treatment option for patients with essential tremor and Parkinson’s disease. This review provides an overview on the functioning of neurostimulators and recent advances in this technology and presents an updated guide on the anesthetic management of patients with an implanted neurostimulator undergoing surgery or medical intervention.SourceA search was conducted on MEDLINE®, EMBASE™, and Cochrane Database of Systematic Reviews databases to identify studies published in English from 1974 to December 2015. Our search also included relevant and available incident reports from the manufacturers, Health Canada, the United States Food and Drug Administration, and the European Medicines Agency. Thirty of 232 articles identified were found to be relevant to this review.Principal findingsDeep brain stimulation systems now offer a range of options, including pulse generators with dual-channel capabilities, rechargeable batteries, and current-control modes. Preoperatively, the anesthesiologist should ascertain the indications for DBS therapy, identify the type of device implanted, and consult a DBS specialist for specific precautions and device management. The major perioperative concern is the potential for interactions with the medical device resulting in patient morbidity. Neurostimulators should be turned off intraoperatively to minimize electromagnetic interference, and precautions should be taken when using electrosurgical equipment. Following surgery, the device should be turned on and checked by a DBS specialist.ConclusionThe anesthesiologist plays an important role to ensure a safe operating environment for patients with an implanted DBS device. Pertinent issues include identifying the type of device, involving a DBS-trained physician, turning off the device intraoperatively, implementing precautions when using electrosurgical equipment, and checking the device postoperatively.RésuméObjectifLa stimulation cérébrale profonde (SCP) peut constituer une option thérapeutique efficace pour les patients atteints de tremblement essentiel ou de la maladie de Parkinson. Ce compte rendu propose un aperçu du fonctionnement des neurostimulateurs et des progrès récents de cette technologie et présente un guide mis à jour de la prise en charge anesthésique des patients ayant un neurostimulateur implanté et devant subir une chirurgie ou une intervention médicale.SourceNous avons réalisé des recherches dans les bases de données MEDLINE®, EMBASE™ et la base de données Cochrane de comptes rendus méthodiques (Cochrane Database of Systematic Reviews) afin d’identifier les études publiées en anglais entre 1974 et décembre 2015. Nos recherches ont également inclus les rapports d’incident pertinents et disponibles des fabricants, de Santé Canada, de la FDA (Food and Drug Administration) américaine, et de l’Agence européenne des médicaments. Au total, trente des 232 articles identifiés ont été jugés pertinents à ce compte rendu.Constatations principalesLes dispositifs de stimulation cérébrale profonde proposent aujourd’hui une vaste gamme d’options, notamment des générateurs d’impulsions capables d’utiliser deux canaux, des piles rechargeables, et des modes de contrôle du courant. Avant l’opération, l’anesthésiologiste devrait vérifier les indications thérapeutiques d’une SCP, identifier le type de dispositif implanté, et consulter un spécialiste de la SCP pour connaître les précautions spécifiques et la prise en charge du système. La préoccupation périopératoire majeure est le potentiel d’interactions avec le dispositif médical, ce qui pourrait provoquer une morbidité pour le patient. Les neurostimulateurs devraient être éteints pendant l’opération afin de minimiser les interférences électromagnétiques, et des précautions doivent être prises lors de l’utilisation de matériel électrochirurgical. Après la chirurgie, le dispositif devrait être rallumé et vérifié par un spécialiste de la SCP.ConclusionL’anesthésiologiste joue un rôle important pour garantir un environnement opératoire sécuritaire pour les patients munis d’un dispositif de SCP implanté. Les questions pertinentes sont l’identification du type de dispositif, la consultation d’un médecin formé en SCP, la mise hors tension du dispositif pendant l’opération, la mise en œuvre de précautions lors du recours à du matériel électrochirurgical, et la vérification postopératoire du dispositif.

Sumatriptan improves postoperative quality of recovery and reduces postcraniotomy headache after cranial nerve decompression

BACKGROUND Microvascular decompression (MVD) is a surgical treatment for cranial nerve disorders via a small craniotomy. The postoperative pain of this procedure can be classified as surgical site somatic pain and postcraniotomy headache similar in nature to a migraine, including its association with photophobia, nausea, and vomiting. This headache can be difficult to treat and can impact on postoperative recovery. Sumatriptan is used to treat migraine-like headaches in various settings. This single-centre randomized controlled trial investigated whether postoperative administration of sumatriptan after MVD surgery impacts the quality of postoperative recovery. METHODS Fifty patients who complained of postoperative headache after MVD were randomized to receive an s.c. injection of sumatriptan (6 mg) or saline. The primary outcome was quality of recovery as measured by the Quality of Recovery-40 (QoR-40) score at 24 h. RESULTS The QoR-40 scores were significantly higher in the sumatriptan group (median 184; interquartile range 169-196) than in the placebo group (133; 119-155; P<0.01), suggesting higher quality of recovery. The sumatriptan group also had significantly lower headache scores at 4, 12, and 24 h. There were no significant differences in other secondary outcomes. CONCLUSIONS Use of sumatriptan improved the quality of recovery as measured by the QoR-40 and reduction of headache at 24 h after surgery. Sumatriptan is a useful alternative treatment for postcraniotomy headache. The mechanism remains unknown but could be related to reduction in headache, mood modulation, or both, mediated by a serotonin effect. CLINICAL TRIAL REGISTRATION NCT01632657.

Measurement of Cerebrovascular Reactivity as Blood Oxygen Level-Dependent Magnetic Resonance Imaging Signal Response to a Hypercapnic Stimulus in Mechanically Ventilated Patients

BACKGROUND Impaired cerebrovascular reactivity (CVR) is an important prognostic marker of stroke. Most measures of CVR lack (1) a reproducible vasoactive stimulus and (2) a high time and spatial resolution measure of cerebral blood flow (CBF), particularly for mechanically ventilated patients. The aim of our study was to investigate the feasibility of measuring CVR using sequential gas delivery circuit and gas blender for precise targeting of end-tidal PCO2 (PetCO2), and blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) signal as a surrogate of CBF, in mechanically ventilated patients. METHODS Four patients with known moyamoya disease requiring preoperative CVR measurements under general anesthesia were studied. All patients had standard anesthesia induction and maintenance with intravenous propofol and rocuronium. Patients were intubated and manually ventilated with a self-inflating bag connected to a sequential breathing circuit. A computer-controlled gas blender supplied the gas mixture in proportions to attain target PetCO2. BOLD-MRI was performed at 3.0 Tesla magnet. Changes in signal per change in PetCO2 were calculated, and their magnitude color-coded and mapped onto the anatomic scan to form CVR maps. RESULTS CVR studies were successfully performed on all patients, and the CVR values were lower in both gray and white matter bilaterally when compared with healthy volunteers. In addition, CVR maps in 3 patients showed intracerebral steal phenomenon in spite of having had cerebral revascularization procedures, indicating that they are still at risk of cerebral ischemia. CONCLUSIONS BOLD-MRI CVR studies are feasible in mechanically ventilated patients anesthetized with propofol.

Long-term changes in cerebrovascular reactivity following EC-IC bypass for intracranial steno-occlusive disease

The purpose of this retrospective observational study is to investigate the long-term changes in cerebrovascular reactivity (CVR) as a measure of cerebral hemodynamics in patients with intracranial steno-occlusive disease (IC-SOD) after they have undergone an Extracranial-intracranial (EC-IC) bypass. Twenty-six patients suffering from IC-SOD were selected from our CVR database. Nineteen patients underwent unilateral and 7 underwent bilateral revascularization. CVR measurements were done using BOLD-MRI and precisely controlled CO2 and expressed as ΔBOLD (%)/Δ PETCO2 (mmHg). Trends in CVR over time were compared in both vascularized and non-vascularized hemispheres. Repeated measures analysis of variance with Greenhouse-Geisser correction was used to determine CVR changes within the grey matter MCA for longitudinal assessments. Overall, re-vascularized hemisphere showed a significant increase in CVR at the first follow-up, followed by a slight decrease at the second follow-up that significantly increased compared to the pre-bypass. However, the changes in the postoperative CVR were quite variable across the patients. Similar variability was seen in subsequent follow-ups, with a slight overall decline in the long term CVR as compared with first post-operative CVR. Our study demonstrates that EC-IC bypass has a beneficial long-term effect on cerebral hemodynamics and this effect varies between patients probably due to the variability in the underlying vascular pattern receiving the bypass. Hence, in the postoperative follow-up of patients routine functional imaging to monitor cerebral hemodynamics may be useful as the risk of stroke and cognitive decline remain present with impaired CVR.

Cerebrovascular Resistance: The Basis of Cerebrovascular Reactivity

The cerebral vascular network regulates blood flow distribution by adjusting vessel diameters, and consequently resistance to flow, in response to metabolic demands (neurovascular coupling) and changes in perfusion pressure (autoregulation). Deliberate changes in carbon dioxide (CO2) partial pressure may be used to challenge this regulation and assess its performance since CO2 also acts to change vessel diameter. Cerebrovascular reactivity (CVR), the ratio of cerebral blood flow (CBF) response to CO2 stimulus is currently used as a performance metric. However, the ability of CVR to reflect the responsiveness of a particular vascular region is confounded by that region’s inclusion in the cerebral vascular network, where all regions respond to the global CO2 stimulus. Consequently, local CBF responses reflect not only changes in the local vascular resistance but also the effect of changes in local perfusion pressure resulting from redistribution of flow within the network. As a result, the CBF responses to CO2 take on various non-linear patterns that are not well-described by straight lines. We propose a method using a simple model to convert these CBF response patterns to the pattern of resistance responses that underlie them. The model, which has been used previously to explain the steal phenomenon, consists of two vascular branches in parallel fed by a major artery with a fixed resistance unchanging with CO2. One branch has a reference resistance with a sigmoidal response to CO2, representative of a voxel with a robust response. The other branch has a CBF equal to the measured CBF response to CO2 of any voxel under examination. Using the model to calculate resistance response patterns of the examined branch showed sigmoidal patterns of resistance response, regardless of the measured CBF response patterns. The sigmoid parameters of the resistance response pattern of examined voxels may be mapped to their anatomical location. We show an example for a healthy subject and for a patient with steno-occlusive disease to illustrate. We suggest that these maps provide physiological insight into the regulation of CBF distribution.

Airway Management With a Stereotactic Headframe In Situ-A Mannequin Study.

Background: Stereotactic headframe-based imaging is often needed for target localization during surgery for insertion of deep brain stimulators. A major concern during this surgery is the need for emergency airway management while an awake or sedated patient is in the stereotactic headframe. The aim of our study was to determine the ease of emergency airway management with a stereotactic headframe in situ. Materials and Methods: We conducted an observational study using a mannequin. A Leksell stereotactic headframe was placed on a mannequin in the operating room and the frame was fixed to the operating room table. Anesthesia personnel were asked to insert a #4 laryngeal mask and then to intubate the mannequin, using both direct (DL) and video laryngoscopy (VL). In addition, participants were asked to perform the same airway techniques in the mannequin without the headframe. Data were analyzed for time taken for airway management using different devices with and without the headframe. In addition, we compared the time taken to secure the airway between different participant groups. Results: Thirty anesthesia personnel (7 residents, 12 fellows, and 11 consultants) participated in the study. With the headframe in situ, 97% of participants were able to insert a laryngeal mask on their first attempt; 93% and 97% of participants were able to intubate the mannequin using DL and VL respectively on their first attempt. Without the stereotactic headframe, all participants were able to insert the laryngeal mask and intubate on the first attempt. The average time taken to insert a laryngeal mask and intubate the mannequin using DL and VL with the headframe in situ was 39.3, 58.6, and 54.8 seconds, respectively. Conclusions: Our study showed that both laryngeal mask insertion and tracheal intubation can be performed with a stereotactic headframe in situ. A laryngeal mask is the quickest airway device to insert and can be inserted while the mannequin is in the standard surgical position. Further study is needed to validate the results in patients.

Comparison of General and Local Anesthesia for Deep Brain Stimulator Insertion: A Systematic Review

BACKGROUND Subthalamic nucleus deep brain stimulation (STN-DBS) has become a standard treatment for many patients with Parkinsons disease (PD). The reported clinical outcome measures for procedures done under general anesthesia (GA) compared to traditional local anesthetic (LA) technique are quite heterogeneous and difficult to compare. The aim of this systematic review and metaanalysis was to determine whether the clinical outcome after STN-DBS insertion under GA is comparable to that under LA in patients with Parkinsons disease. METHODS The databases of Medline Embase, Cochrane library and Pubmed were searched for eligible studies (human trials, English language, published between 1946 and January of 2016). The primary outcome of this study was to assess the postoperative improvement in the symptoms, evaluated using either Unified Parkinsons Disease Rating Scale (UPDRS) scores or levodopa equivalent dosage (LEDD) requirement. RESULTS The literature searches yielded 395 citations and six retrospective cohort studies with a sample size of 455 (194 in GA and 261 in LA) were included in the analysis. Regarding the clinical outcomes, there were no significant differences in the postoperative Unified Parkinsons disease rating scale and levodopa equivalent drug dosage between the GA and the LA groups. Similarly, the adverse events and target accuracy were also comparable between the groups. CONCLUSIONS This systematic review and meta-analysis shows that currently there is no good quality data to suggest equivalence of GA to LA during STN-DBS insertion in patients with PD, with some factors trending towards LA. There is a need for a prospective randomized control trial to validate our results.

In reply: Parkinsonism-hyperthermia syndrome and deep brain stimulation

To the Editor, We thank Dr. Caroff for his positive comments on our review and for bringing up the issue of Parkinsonismhyperthermia syndrome (PHS). We agree that PHS is a rare but potentially fatal condition seen in patients with Parkinson’s disease when their dopaminergic medications are abruptly reduced or stopped. It has also been described in patients with implanted deep brain stimulators after battery depletion or device malfunction. In our institution, we have witnessed a few patients with an implanted deep brain stimulator for Parkinson’s disease who presented with symptoms of PHS after complete depletion of the device’s battery. They often require urgent surgery for battery replacement. We did not include this point in our manuscript as it is a rare condition and unlikely to occur in patients who have the deep brain stimulator temporarily turned off during the intraoperative period. We agree, however, that it is an important differential diagnosis to consider in this group of patients.