Kenneth R. Moran

Anesthesia and evoked responses in neurosurgery

Intraoperative evoked potential (EP) monitoring has become a routine part of operative neurosurgical procedures. The theoretical, technical, and clinical aspects of various EPs have been extensively characterized and significant clinical experience has been accumulated with this modality of neuromonitoring. Successful EP monitoring requires an adequate understanding of how anesthetic drugs and physiological variations affect EP signals and how to improve the sensitivity of neuromonitoring through appropriate drug selection and administration. Unlike intraoperative electroencephalography (EEG), EP signals are much smaller in amplitude (0.1–20 mcV) and indistinguishable from background noise. In order to extract the EP signal from the underlying EEG noise, multiple stimulations with summation and frequency filtering are necessary (Freye, 2005; Moller, 2011). EPs are highly sensitive to fluctuations in physiological parameters such as peripheral and core body temperature, arterial blood pressure, hematocrit etc. They are also susceptible to various general anesthetic agents and other drugs frequently given during surgery. The effects of general anesthetics on intraoperative EP depend on the mode of evoked response and the pharmacological characteristics of administered anesthetic drugs. Evoked responses that travel via polysynaptic pathways, such as visual EP are significantly more susceptible to the anesthesia and surgery when compared to EPs with fewer synapses in their pathway. In general, inhalational anesthetics are more potent suppressants of EP than intravenous agents (Banoub et al., 2003; Moller, 2011). Combinations of inhalational agents, as occurs with the addition of nitrous oxide, potentiate the suppressive effects of anesthesia even further. Despite their suppressive effects on EPs, inhalational anesthetics have obvious advantages for use during neurosurgery because they are easily titratable to provide stable anesthetic conditions. Lower doses of inhalational anesthetics (0.5–0.8 MAC depending on type of the evoked response) have been successfully applied during neurosurgical interventions and neurophysiological monitoring without compromising the quality of monitoring. Balanced general anesthesia with low doses of inhalational agents combined with low-dose constant infusions of remifentanil (0.05 mcg/kg/min), propofol (50 mcg/kg/min), or dexmedetomidine (0.003–0.005 mcg/kg/min) may be recommended when EP monitoring is anticipated. Such an approach will provide stable anesthesia and reduce the incidence of adverse events encountered occasionally during total intravenous anesthesia such as patient movement and awareness. Sevoflurane has low solubility compared with other inhalation anesthetics and thus is eliminated rapidly, minimizing its effects during monitoring later in the case (Sloan T, as cited in Fulkerson et al., 2011). Using sevoflurane as an induction agent, Fulkerson and colleagues were able to successfully monitor the intraoperative motor EPs in young children (less than 3 years) undergoing neurosurgical spinal procedures (Fulkerson et al., 2011). We believe that other inhalational anesthetics with low blood solubility (desflurane) may uneventfully be used for anesthesia induction and will be compatible with intraoperative neurophysiological monitoring. Anesthetics used for intravenous anesthesia, with a few exceptions, produce a dose-dependent suppressive effect on EP. Unlike the other intravenous hypnotics, etomidate, and ketamine tend to increase the SSEP amplitudes (Banoub et al., 2003). Further studies will be required to evaluate whether the use of various concentrations of these anesthetics during neurosurgical interventions suppress EP equally when different modalities of EP are being monitored. Opioids, in general, do not affect the quality of intraoperative EP monitoring. However, their mild suppressive effects are proportional to lipophilicity. When infused at higher doses, remifentanil causes a 20–80% decline in P37 peak amplitude of SSEP and a mild (<10%) increase in latency (Asouhidou et al., 2010). Midazolam and other benzodiazepines moderately suppress the intraoperative EP (Banoub et al., 2003), and their use, whenever possible, should be avoided. Benzodiazepine-induced EP suppression is less pronounced compared to inhalational agents. Dexmedetomidine, a relatively new hypnotic characterized by selective alpha-2 adrenergic antagonism, can be safely used to supplement general anesthesia during EP monitoring (Tobias et al., 2008). Intravenous lidocaine (1.5 mg/kg/h) is also a useful adjunct to general anesthesia with EP monitoring due to its ability to reduce anesthetic requirements, stabilize the cardiovascular parameters and decrease the incidence of patient movement during surgery (Sloan et al., 2014). Monitoring of motor EPs during surgery requires special caution, as they are more sensitive to anesthetics and muscle relaxants (Kunisawa et al., 2004; Lotto et al., 2004). Anesthetic conditions optimized for motor EP monitoring are suitable for SSEP registration as well (Pajewski et al., 2007). Although, partial muscle relaxation can be used for motor EP monitoring during surgery (Moller, 2011; Kim et al., 2013), most practitioners refrain from using muscle relaxants after tracheal intubation. In addition to selection of the most suitable anesthetics, their mode of administration is also an important factor that influences the quality of EP monitoring. During procedures requiring EP monitoring, steady infusion rates and stable concentrations of inhalational agents are preferred. Administration of drugs in bolus doses and variations in anesthesia level can negatively impact the quality of signal and cause EP suppression indistinguishable from changes triggered by surgical trauma (van Dongen et al., 1999; Lotto et al., 2004; Pajewski et al., 2007; Tobias et al., 2008; Deipolyi et al., 2011). During lengthy neurosurgical procedures, gradual attenuation of the EP signal may occur. This signal degradation is not related to the dose of anesthetics and is proportional to the length of anesthesia. This phenomenon is more frequently seen in younger patient populations and those with spinal cord pathology (Yang et al., 2012; Macdonald et al., 2013). The exact mechanisms underlying signal degradation are currently not well understood. Intraoperative monitoring of evoked responses can be successfully utilized to reduce the rate of inadvertent trauma to the nervous structures during neurosurgical procedures. Their interpretation requires profound knowledge of neurophysiology, comprehension of the surgical procedure and an understanding of the effects that general anesthesia and physiological changes may have on signal quality. Intraoperative neuromonitoring is one of the areas of medicine where team approach is a crucial prerequisite to obtain meaningful results. During neurosurgical procedures, a variety of general and local anesthetics are used, and many of them can substantially affect or even completely eliminate the EP signal. The possibility of anesthesia-related signal suppression and the influence of physiological changes on EP must be considered in order to avoid such effects. Drugs with minimal interference on neurophysiological monitoring should be used preferentially, and attempts made to keep the anesthetic concentrations, temperature, and other physiological variables constant. Maintaining steady state concentrations of an appropriately selected balanced anesthetic will reduce the incidence of false positive results and assist in the prevention of surgical trauma and ischemic damage during neurosurgical interventions. Appropriate drug selection, meticulous drug administration and minimization of physiological variation can improve patient safety by optimizing EP signal monitoring in patients undergoing neurological surgery.

Current Status of Blood Transfusion and Antifibrinolytic Therapy in Orthopedic Surgeries

1 Department of Anesthesiology, Wexner Medical Center, Ohio State University, Columbus, OH, USA 2 Department of Neurological Surgery, Wexner Medical Center, Ohio State University, Columbus, OH, USA 3 Department of Neuroscience, Ohio State University, Columbus, OH, USA 4 Drexel University College of Medicine, Philadelphia, PA, USA 5 Temple University School of Medicine, Philadelphia, PA, USA 6 College of Medicine, Wexner Medical Center, Ohio State University, Columbus, OH, USA 7 Orthopedic One, Columbus, OH, USA *Correspondence: nicoleta.stoicea@osumc.edu

Perioperative Outcome of Dyssomnia Patients on Chronic Methylphenidate Use

Methylphenidate is frequently prescribed for attention deficit hyperactivity disorder, narcolepsy, and other sleep disorders requiring psychostimulants. Our report is based on 2 different clinical experiences of patients with chronic methylphenidate use, undergoing general anesthesia. These cases contrast different strategies of taking versus withholding the drug treatment on the day of surgery. From the standpoint of anesthetic management and patient safety, the concerns for perioperative methylphenidate use are mainly related to cardiovascular stability and possible counteraction of sedatives and anesthetics.

Lateral Position for Cesarean Delivery Because of Severe Aortocaval Compression in a Patient with Marfan Syndrome: A Case Report.

Prompt recognition and management of hypotension resulting from aortocaval compression syndrome are essential to optimize the maternal and fetal outcomes. Management involves increasing leftward uterine displacement and sometimes full lateral positioning, although lateral position during cesarean delivery is typically considered to be impractical. We report an obstetric patient case of severe aortocaval compression syndrome resulting in hypotension and loss of consciousness that ultimately underwent cesarean delivery under general anesthesia in the lateral position. Performing cesarean delivery in the lateral position is virtually unreported, and this unique strategy prevented further symptoms of aortocaval compression and enabled safe delivery.

Non-opioid anesthetic drug abuse among anesthesia care providers: a narrative review.

PurposeThe objective of this narrative review is to provide an overview of the problem of non-opioid anesthetic drug abuse among anesthesia care providers (ACPs) and to describe current approaches to screening, therapy, and rehabilitation of ACPs suffering from non-opioid anesthetic drug abuse.SourceWe first performed a search of all literature available on PubMed prior to April 11, 2016. The search was limited to articles published in Spanish and English, and the following key words were used: anesthesiology, anesthesia personnel, AND substance-related disorders. We also searched Ovid MEDLINE® databases from 1946-April 11, 2016 using the following search terms: anesthesiology OR anesthesia, OR nurse anesthetist OR anesthesia care provider OR perioperative nursing AND substance-related disorders.Principal findingsDespite an increased awareness of drug abuse among ACPs and improvements in preventive measures, the problem of non-opioid anesthetic drug abuse remains significant. While opioids are the most commonly abused anesthesia medications among ACPs, the abuse of non-opioid anesthetics is a significant cause of morbidity, mortality, and professional demise.ConclusionEarly detection, effective therapy, and long-term follow-up help ACPs cope more effectively with the problem and, when possible, resume their professional activities. There is insufficient evidence to determine the ability of ACPs to return safely to anesthesia practice after rehabilitation, though awareness of the issue and ongoing treatment are necessary to minimize patient risk from potentially related clinical errors.RésuméObjectifL’objectif de ce compte rendu est de présenter une vue d’ensemble du problème d’abus de médicaments anesthésiques non opioïdes parmi le personnel d’anesthésie et de décrire les approches de dépistage, de traitement et de réhabilitation actuellement à la disposition du personnel d’anesthésie souffrant d’un abus de médicaments anesthésiques non opioïdes.SourceNous avons commencé par réaliser une recherche de toute la littérature disponible sur PubMed avant le 11 avril 2016. La recherche se limitait aux articles publiés en espagnol et en anglais, et les mots clés suivants ont été utilisés: anesthésiologie, personnel d’anesthésie, ET troubles liés à l’abus de substance. Nous avons également effectué une recherche dans les bases de données Ovid MEDLINE® entre 1946 et le 11 avril 2016 à l’aide des termes de recherche suivants: anesthésiologie OU anesthésie, OU infirmière anesthésiste OU personnel d’anesthésie OU soins infirmiers périopératoires ET troubles liés à l’abus de substances (soit: ‘anesthesiology’ ou ‘anesthesia’, ou ‘nurse anesthetist’ ou ‘anesthesia care provider’ ou ‘perioperative nursing’ et ‘substance-related disorders’).Constatations principalesMalgré une meilleure prise de conscience de l’abus de médicaments parmi le personnel d’anesthésie et les progrès en matière de mesures préventives, le problème qu’est l’abus de médicaments anesthésiques non opioïdes demeure considérable. Bien que les opioïdes soit les médicaments les plus fréquemment rencontrés dans les problèmes d’abus de médicaments anesthésiques chez le personnel d’anesthésie, l’abus de médicaments anesthésiques non opioïdes constitue néanmoins une importante cause de morbidité, de mortalité et de terminaison de carrière.ConclusionLe dépistage précoce, un traitement efficace et un suivi à long terme peuvent aider le personnel d’anesthésie à mieux gérer le problème et, lorsque cela est possible, reprendre leurs activités professionnelles. Les données probantes ne sont pas suffisantes pour attester que le personnel d’anesthésie peut revenir en toute sécurité à la pratique de l’anesthésie après réhabilitation, mais la prise de conscience du problème et un traitement continu sont nécessaires afin de minimiser le risque encouru par les patients d’erreurs cliniques potentiellement liées à ces abus.

Emergence Delirium: Revisiting a Clinical Enigma

A. “Disturbance in level of awareness and reduced ability to direct, focus, sustain, and shift attention (this represents a minor change from: Disturbance of consciousness (i.e., reduced clarity of awareness of the environment) with reduced ability to focus, sustain or shift attention). B. A change in cognition (such as deficits in orientation, executive ability, language, visuoperception, learning and memory). • Cannot be assessed in face of severely reduced level of awareness • Should not be better accounted for by a preexisting neurocognitive disorder (A minor change from a change in cognition or the development of a perceptual disturbance that is not better accounted for by a preexisting, established or evolving dementia.) C. There is evidence from the history, physical examination, or laboratory findings that the disturbance is caused by the direct physiologic consequences of a general medical condition (no change from DSM IV). D. The disturbance develops over a short period of time (usually hours to a few days) and tends to fluctuate in severity during the course of a day (no change from DSM IV).”

Dermal tattooing following intravenous methylene blue for refractory hypotension after coronary artery bypass grafting

The authors present an image of a middle-aged male after coronary artery bypass grafting who received intravenous methylene blue for refractory hypotension that resulted in dermal tattooing/staining of the venous vasculature of his left shoulder and left upper chest. Republished with permission from: Bhatt AM, Tripathi RS, Moran KR, Papadimos TJ. Dermal tattooing following intravenous methylene blue for refractory hypotension after coronary artery bypass grafting. OPUS 12 Scientist 2012;6(1):11.

Perioperative Management of a Patient with Cold Urticaria

Cold urticaria consists of an allergic immune response to cold temperatures with symptoms ranging from pruritic wheals to life-threatening angioedema, bronchospasm, or anaphylactic shock. Adequate planning to maintain normothermia perioperatively is vital due to impaired hypothalamic thermoregulation and overall depression of sympathetic outflow during deep sedation and general anesthesia. This case report describes the successful perioperative management of a 45-year-old female with a history of cold urticaria undergoing a laparoscopic Nissen fundoplication for refractory gastroesophageal reflux disease and discusses how to appropriately optimize the care of these patients.

Diagnosis and Rescue of a Kinked Pulmonary Artery Catheter

Invasive hemodynamic monitoring with a pulmonary catheter has been relatively routine in cardiovascular and complex surgical operations as well as in the management of critical illnesses. However, due to multiple potential complications and its invasive nature, its use has decreased over the years and less invasive methods such as transesophageal echocardiography and hemodynamic sensors have gained widespread favor. Unlike these less invasive forms of hemodynamic monitoring, pulmonary artery catheters require an advanced understanding of cardiopulmonary physiology, anatomy, and the potential for complications in order to properly place, manage, and interpret the device. We describe a case wherein significant resistance was encountered during multiple unsuccessful attempts at removing a patients catheter secondary to kinking and twisting of the catheter tip. These attempts to remove the catheter serve to demonstrate potential rescue options for such a situation. Ultimately, successful removal of the catheter was accomplished by simultaneous catheter retraction and sheath advancement while gently pulling both objects from the cannulation site. In addition to being skilled in catheter placement, it is imperative that providers comprehend the risks and complications of this invasive monitoring tool.

Acromegaly,Endocrine Dysfunction and Polyostotic Fibrous Dysplasia Associated With Mccune-Albright Syndrome: Anesthetic Considerations Case

McCune-Albright Syndrome is a rare disorder affecting the skin, bones and endocrine tissues. It is characterized by the presence of cafe au lait spots, polyostotic fibrous dysplasia, and autonomous endocrine hyperfunction. Perioperative management of patients with this syndrome is frequently complex, as they are prone to a large array of comorbidities including pathologic fractures and spinal instability, acromegaly, hyperthyroidism, hypophosphatemia, Cushings syn- drome and chronic systemic hypertension, liver disease, and arrythmias. Anesthesiologists are faced with a spectrum of challenges in the perioperative management of these patients. Macroglossia and macrognathia can result in airways which are difficult to visualise and secure. Frail bones and spinal instability often complicate positioning, and endocrinopathies may result in an increased propensity for cardiac arrhythmias perioperatively. The objective of this paper is to report the case of a 36 year-old male with McCune-Albright Syndrome presenting for a T10-11 laminectomy due to spinal cord compression and to discuss our management of this complicated patient with a history of hypophosphatemia, scolio- sis, multiple long bone fractures, non-ischemic cardiomyopathy, atrial fibrillation, and severe acromegaly from a growth hormone-secreting pituitary adenoma.