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IntroductionElectroconvulsive Therapy may be utilized in as many as 76,000 cases annually in the US, with the majority of cases employing succinylcholine. The reported dose spans the range of 0.29 - 2.1 mg/kg, and while motor seizures only last 36 ± 6 seconds, the duration of paralysis extends to 310 ± 38 seconds. While a model of succinylcholine pharmacokinetics/pharmacodynamics exists, this has not been employed to facilitate dose selection in clinical practice. Probability ramp control was investigated for this purpose.MethodsTwo approaches to dose finding were implemented. The first was an optimized Up-Down Method (UDM) that utilized an initial bolus, an adjustment dose, and a decrement to decrease the adjustment when crossing the target of 95% twitch depression. The second utilized probability ramp control (PRC) comprised of an infusion sequence that stopped when 95% twitch depression was obtained, a model that mapped the times for onset and offset of blockade to a subsequent bolus, and an adjustment dose to refine this dose when needed. Two populations of 10000 randomly parameterized models were developed from published data to train and evaluate the performance. Performance was assessed with a fuzzy classifier that segmented outcomes into three sets – LOW, HIGH, and SUCCESS. A loss function was developed that determined the number of sessions required to bring all models to SUCCESS. The probability distributions were compared using the Kolmogorov-Smirnov 2 sample test, with PResultsOptimal values for the UDM parameters BOLUS, ADJUSTMENT, and DECREMENT were 0.7834 mg/kg, 0.3334 mg/kg, and 0.4056. Optimal values for the PRC SEQUENCE were 0.2663 mg/kg/min for 3 minutes followed by 0.7028 mg/kg/min. A fourth order polynomial MODEL produced estimates of the bolus that brought 99% of models to SUCCESS on the second session, while UDM required 6 sessions to achieve 99% SUCCESS. The probability distributions were distinct with P

A wealth of information about respiratory system is encoded in the airflow signal. While direct measurement of airflow via spirometer with an occlusive seal is the gold standard, this may not be practical for ambulatory monitoring of patients. Advances in sensor technology have made measurement of motion of the thorax and abdomen feasible with small inexpensive devices, but estimating airflow from these time series is challenging due to the presence of complicated nonstationary oscillatory signals. To properly extract the relevant oscillatory features from thoracic and abdominal movement, a nonlinear-type time-frequency analysis tool, the synchrosqueezing transform, is employed; these features are then used to estimate the airflow by a locally stationary Gaussian process regression. It is shown that, using a dataset that contains respiratory signals under normal sleep conditions, accurate airflow out-of-sample predictions, and hence the precise estimation of an important physiological quantity, inspiration respiration ratio, can be achieved by fitting the proposed model both in the intra- and inter-subject setups. The method is also applied to a more challenging case, where subjects under general anesthesia underwent transitions from pressure support to unassisted ventilation to further demonstrate the utility of the proposed method.

Provide a practical update on drug-induced sleep endoscopy (DISE) for anesthesia providers, which can also serve as a reference for those preparing to establish a DISE program.New developments in surgical approaches to OSA and the growing global incidence of the condition have stimulated increased interest and demand for drug-induced sleep endoscopy. New techniques include transoral robotic surgery and hypoglossal nerve stimulation. Recent DISE literature has sought to address numerous debates including relevance of DISE findings to those during physiologic sleep and the most appropriate depth and type of sedation for DISE. Propofol and dexmedetomidine have supplanted midazolam as the drugs of choice for DISE. Techniques based on pharmacokinetic models of propofol are superior to empiric dosing with regard to risk of respiratory compromise and the reliability of dexmedetomidine to achieve adequate conditions for a complete DISE exam is questionable.The role of DISE in surgical evaluation and planning for treatment of OSA continues to develop. Numerous questions as to the optimal anesthetic approach remain unanswered. Multicenter studies that employ a standardized approach using EEG assessment, pharmacokinetic-pharmacodynamic modelling, and objectively defined clinical endpoints will be helpful. There may be benefit to undertaking DISE studies in non-OSA patients.

BACKGROUND Anesthesia and sedation are associated with paradoxical breathing. Respiratory inductance plethysmography (RIP) permits measurement of respiratory motion in clinical settings not conducive to spirometry, but correlation of RIP volume changes and spirometer flow in the time domain is degraded by the development of paradoxical breathing. The Hilbert-Huang transform (HHT) is a nonlinear signal analysis method that permits the instantaneous magnitude and phase of nonstationary signals to be estimated in the frequency domain. We hypothesized that these frequency domain estimates would provide higher correlation between RIP and spirometer signals than time domain signals during the transition between normal and paradoxical breathing. METHODS From 51 patients undergoing sevoflurane anesthesia for minor procedures, a 5-minute epoch containing transitions between pressure support ventilation and spontaneous ventilation was selected for analysis. Pearson correlation for models based on HHT magnitude and phase was compared with models based on time domain signals. Bland-Altman analysis was performed to assess deviation from linearity in the models. RESULTS For the 51 patients analyzed, the modulation of tidal volume over the epoch ranged from 30% to 215% of epoch mean. The coefficient of determination for time domain analysis was 0.62 ± 0.2 compared with 0.93 ± 0.07 for the HHT model incorporating phase. This improvement of 0.31 (99% confidence interval, 0.24-0.37) was significant (P < 0.0001). No trend was observed in prediction residuals. CONCLUSIONS Under conditions of changing ventilation, HHT-derived magnitude and phase measures provide higher correlation with spirometry than those obtained with traditional time domain methods.

Procedural sedation is commonly employed in endoscopic procedures, and increasingly uses propofol. The use of propofol is commonly restricted to anesthesia providers, and this may increase the cost of care. Administration of propofol requires a special set of skills to deal with the variability of patient response and the consequences of improper dosing. This has stoked interest in the use of automated systems to reduce manpower costs associated with propofol. This article examines why propofol poses challenges for human control, and how various automated systems have been used to address these challenges. We examine target-controlled infusions, patient-controlled sedation, the SEDASYS System, and optimized ramp induction. The article emphasizes on how the various approaches deal with the range of variability in propofol response. No single system is capable of dealing with all patients without some human supervision and intervention.

PURPOSE OF REVIEW Sedation for nonoperating room procedures is experiencing a considerable increase in demand. Respiratory compromise is one of the most common adverse events seen in sedation. Capnography is a modality that has been widely adopted in this area, but may not be well suited to the special demands of nonoperating room sedation. This review is an assessment of new technologies that may improve outcomes beyond those achievable with capnography. RECENT FINDINGS New devices for detecting the onset of apnea and for assessing respiratory depression have emerged which have advantages over conventional capnography for detecting apnea without excessive false positive and false negative rates. In addition, monitors that assess respiratory drive have become available, and these may prove useful in regulating depth of sedation. SUMMARY No single monitor is ideal for all settings. During brief endoscopic sedation, detection of apnea is paramount, while during longer procedures, avoiding excessive respiratory depression is more critical. The clinician must choose the appropriate monitor based on an understanding of the challenges of the particular environment.

The electrophysiology suite is a foreign location to many anesthesiologists. The initial experience was with shorter procedures under conscious sedation, and the value of greater tailoring of the sedation/anesthesia by anesthesiologists was not perceived until practice patterns had already been established. Although better control of ventilation with general anesthesia may be expected, suppression of arrhythmias, blunting of the hemodynamic adaptation to induced arrhythmias, and interference by muscle relaxants with identification of the phrenic nerve may be seen. We review a range of electrophysiology procedures and discuss anesthetic approaches that balance patient safety and favorable outcomes.

Accurate monitoring of respiratory rate may be useful for the early detection of patient deterioration. Monitoring of respiratory rate in the operating room under general anesthesia by spirometry is technically straightforward and demonstrates high fidelity. Accurate measurement of the respiratory rate of an unattended patient outside the operating room is fraught with challenges. Monitors such as capnometry and thoracic impedance pneumography have significant drawbacks. Respiratory acoustic monitoring (RRa™) is a new technology for respiratory rate monitoring, which has been demonstrated to provide accurate respiratory rates in patients recovering from anesthesia, but the performance of this RRa-enabled monitor under conditions of major respiratory rate variation has not been evaluated.We enrolled 53 patients undergoing urologic procedures in the operating room under general anesthesia with a laryngeal mask airway, spontaneous ventilation, and no muscle relaxation in an observational study. Respiratory signals (RRa and in-circuit pneumotachograph) were stored for later analysis. Artifacts were excluded based on visual inspection of the raw respiratory waveforms. Instantaneous respiratory rates were obtained from the pneumotachograph signal using the Hilbert-Huang Transform. Instantaneous rate estimates (IREs) were compared with RRa by 3 methods. First, the mean delay between IREs and RRa was determined. Second, precision was obtained by Bland-Altman analysis for repeated measures. Third, for all disparities in rates exceeding 4 breaths per minute (bpm), the probability of persistent error was determined as a function of time, with 95% confidence intervals estimated by bootstrap analysis.Data were collected from 53 patients. Three patients were excluded due to missing data. There were no adverse events related to RRa monitoring. RRa demonstrated a median delay of 45 seconds (interquartile range 20 seconds) to detect a 1- bpm change in IREs. Bland-Altman revealed 95% limits of agreement of -2.1 to 2.2 bpm across the range of 7 to 48 bpm. Disparities in respiratory rate4 bpm between the 2 methods did not persist beyond 160 seconds, and 90% of these differences resolved within 33 seconds (95% confidence interval 23-48 seconds).The data demonstrate that, under conditions of general anesthesia with a laryngeal mask airway and spontaneous ventilation, the RRa rapidly detects changes in respiratory rate, demonstrates minimal bias, and when errors in rate occur, these do not persist. The utility of this monitoring technology in detecting rate changes in unattended patients will require further study.

Infusion systems are complicated electromechanical systems that are used to deliver anesthetic drugs with moderate precision. Four types of systems are described-gravity feed, in-line piston, peristaltic, and syringe. These systems are subject to a number of failure modes-occlusion, disconnection, siphoning, infiltration, and air bubbles. The relative advantages of the various systems and some of the monitoring capabilities are discussed. A brief example of the use of an infusion system during anesthetic induction is presented. With understanding of the functioning of these systems, users may develop greater comfort.

AF Triggers During General Anesthesia Introduction The autonomic nervous system exerts important effects upon atrial fibrillation (AF) initiation. The strategy of anesthesia used during AF ablation may impact the provocation of AF triggers. We hypothesized that the use of general anesthesia (GA) would reduce the incidence of provokable AF triggers in patients undergoing AF ablation compared to patients studied while receiving only conscious sedation (CS). Methods and Results We performed a prospective, case control study comparing the incidence of provokable AF triggers in a consecutive series of patients undergoing AF ablation under GA using a standard trigger induction protocol. We compared the frequency and distribution of AF triggers to a second cohort of historical controls (matched for age, gender, left atrial dimension, and AF phenotype) who underwent ablation while receiving CS. We calculated that 44 total subjects (22 patients in each group) were required to detect a 50% reduction in the incidence of AF triggers in the GA cohort. There was no difference between the 2 groups in the rate of AF trigger inducibility (77% vs. 68%, P = 0.26) or the number of triggers provoked per patient (1.2 ± 0.8 vs. 1.3 ± 0.8, P = 0.38). Patients ablated under GA required higher doses of phenylephrine during the trigger induction protocol (408.3 mg [52–600] vs. 158.3 mg [0–75]; P = 0.003), and tended to require higher doses of isoproterenol to initiate triggers (92.8 mg [20–111] vs. 63.6 mg [6–103]; P = 0.25). Conclusion AF trigger induction during GA is both safe and efficacious.

Infusion pumps are commonly used for infusion of drugs for physiologic control, and infusion rate has been demonstrated to affect the parameters of pharmacokinetic models. In attempting to develop a model that explained this behavior, we examined the behavior of the Graseby 3400 syringe pump under a range of flow conditions and with variations in syringe characteristics. Two issues were identified: start-up loss (the difference between actual and ideal delivery on initial infusion) and update loss (the difference between actual and ideal delivery when transmitting a command to change infusion rate). Under worst-case conditions, this may result in a 20-second period of zero delivery during start-up, and when updating infusion rates once per second, zero output. These effects are influenced by syringe characteristics and vary sufficiently as to make it impossible to isolate this effect from the pharmacokinetic process being controlled. The implications of this for previous published results and clinical application of target-controlled infusions are discussed.

A field-usable sleepiness tester could reduce sleepiness related accidents. 15 subjects' postural steadiness was measured with a Nintendo(®) Wii Fit balance board every hour for 24 h. Body sway was quantified with complexity index, CI, and the correlation between CI and alertness predicted by a three-process model of sleepiness was calculated. The CI group average was 8.9 ± 1.3 for alert and 7.9 ± 1.4 for sleep deprived subjects (p < 0.001, ρ = 0.94). The Wii Fit board detects the impairment of postural steadiness. This may allow large scale sleepiness testing outside the laboratory setting.

Study Objective To characterize respiratory dynamics during emergence from propofol-remifentanil anesthesia using noninvasive respiratory inductance plethysmography (RIP). Design Observational pilot study. Setting Operating room in a university-affiliated teaching hospital. Patients 50 ASA physical status 1, 2, and 3 patients scheduled for microdirect laryngoscopy or bronchoscopy using total intravenous anesthesia (TIVA) with high-frequency jet ventilation. Interventions Patients were fitted with plethysmography bands around the chest and abdomen prior to induction. Following completion of surgery in patients undergoing brief airway procedures using propofol-remifentanil general anesthesia, the anesthetic infusions were stopped and ventilation suspended until resumption of spontaneous ventilation or desaturation below 90%. During this period of apnea, abdominal and thoracic girth was assessed with noninvasive RIP. Measurements Cross-sectional area of the thorax and abdomen during emergence were measured. Main Results Useful data were obtained from 41 patients, with stable apnea lasting 404 ± 193.1 seconds; of these, 34 exhibited a slow and significant decrease in abdominal girth over a period of 267.8 ± 128.5 seconds. Resumption of spontaneous ventilation generally coincided with the end of this abdominal relaxation. Conclusion Slow expiration is the initial step in the resumption of spontaneous ventilation during apnea induced with TIVA using propofol-remifentanil.

High-frequency jet ventilation is a novel technique for providing mechanical ventilation in the out of operating room (OOR) setting. Case reports and a small series of patients have shown it to be useful in patients undergoing cardiac arrhythmia ablations, interventional radiology procedures, and extracorporeal shock wave lithotripsy. Recently, interest in the technique has grown tremendously as the ability to provide superior surgical conditions may lead to improved efficiency and less side-effects in a variety of procedures.Atrial fibrillation ablation procedures, liver tumor ablations, and extracorporeal shock wave lithotripsy are all the procedures that benefit from minimal movement of the heart, liver, and kidney, respectively, during the procedure. Although randomized controlled trials are lacking, increasing data suggest that by maintaining the thoracic and abdominal structures relatively immobile throughout the respiratory cycle, the efficiency and safety of these procedures may be improved.Technological advances are allowing an increasing number of surgical procedures to be performed in the OOR setting. Such procedures often depend on the precise application of ablation catheters or shock waves. High-frequency jet ventilation facilitates the improved accuracy of catheter and shock wave placement, as well as efficiency of a variety of procedures. Improved efficiency, with fewer side-effects, has tremendous implications for the growth of such procedures in the OOR setting.

Objectives The aim of this study was to describe anesthetic management and perioperative complications in patients undergoing pulmonary vein isolation for the treatment of atrial fibrillation under general anesthesia using high-frequency jet ventilation. The authors also identified variables associated with longer ablation times in this patient cohort. Design A retrospective observational study. Setting The electrophysiology laboratory in a major university hospital. Participants One hundred eighty-eight consecutive patients undergoing pulmonary vein isolation under general anesthesia with high-frequency jet ventilation. Interventions High-frequency jet ventilation was used as the primary mode of ventilation under general anesthesia. Measurements and Main Results High-frequency jet ventilation was performed successfully throughout the ablation procedure in 175 cases of the study cohort. The remaining 13 patients had to be converted to conventional positive-pressure ventilation because of high PaCO 2 or low PaO 2 on arterial blood gas measurements. Variables associated with a shorter ablation time included a higher ejection fraction ( p = 0.04) and case volume performed by each electrophysiologist in the study group ( p = 0.001). Conclusions High-frequency jet ventilation is generally a safe technique that can be used in catheter ablation treatment under general anesthesia.

BACKGROUND: When using a target-controlled infusion of propofol to produce sedation, the operator assumes that the individual patient's pharmacokinetic parameters match those in the control system so that the specified effect-site target is achieved, and that the specified target is appropriate for the individual patient's sensitivity. These inaccuracies cascade, and this produces error in the desired level of sedation, termed "target error." To address this issue, we designed a control system that incorporates the operator's observation of loss of responsiveness to determine patient sensitivity. Our hypothesis was that this control system would reduce the impact of pharmacokinetic parameter error and uncertainty in sensitivity on the system's target error. METHODS: A novel control system was implemented that produces a slow transition in the probability of loss of responsiveness, providing the operator with greater resolution to observe the time of this transition. The system uses the time of this transition to infer the effect-site concentration associated with loss of responsiveness, and the infusion sequence necessary to maintain this concentration. We used computer simulation to generate a population of 10,000 patients with randomly distributed pharmacokinetic parameters and sensitivity to propofol, and compared the target error of our system with that of a target-controlled infusion system targeting the effect-site concentration associated with 50% probability of loss of responsiveness. RESULTS: Our system exhibited a target error of -0.75% ± 8.96%, compared with 0% ± 27.6% for target-controlled infusion, reducing the variability in achieving the specified target by a factor of 3.1 compared with target-controlled infusion, which was significant at P < 0.0001. CONCLUSIONS: Our system reduces the impact of biological variability by including the operator in the control loop. The utility of this approach in clinical practice will require further evaluation.

Laryngeal lesions with difficult visualization and access require an alternative approach. Patients with difficult anatomy, anterior glottis, subglottic and upper tracheal lesions can present challenges for the anesthesiologist and surgeon. We describe a technique of ventilating patients through a laryngeal mask airway and passing a flexible bronchoscope with a potassium-titanyl phosphate fiber laser through the laryngeal mask airway for laryngeal and tracheal surgery. There are several advantages to this method, including ease of visualization of airway lesions, wide access for therapeutic interventions, and minimal vocal cord trauma. This technique is an important tool in the management of difficult laryngotracheal lesions.

High frequency jet ventilation (HFJV) is a technique that is most frequently used in the intensive care unit and during tracheal and otorhinolaryngologic surgery. The utility of HFJV for procedures performed outside of the intensive care unit and operating room is currently being explored. The ability of HFJV to provide mechanical ventilation, yet achieve near static conditions of the chest and abdomen, makes it a very appealing technique for procedures such as pulmonary vein isolation and ablation for atrial fibrillation, targeted radiation therapy for lung and liver tumors, and certain diagnostic imaging techniques.

The use of laryngeal mask airway (LMA) and its variants in ear, nose, and throat procedures have been extensively described in case reports, retrospective reviews, and randomized clinical trials. The LMA has developed a considerable following because of its lack of tracheal stimulation, which can be a considerable advantage in ear, nose, and throat (ENT) procedures. The incidence of coughing on emergence has been shown to be lower with the LMA than with the endotracheal tube (ETT). Although other approaches to smooth emergence have been described, few would argue that it is as easy to achieve a smooth emergence with an ETT as with an LMA. Although patients certainly exist for whom the LMA is contraindicated, many will experience better results with the LMA because of the features delineated in this article.

Anesthesia providers increasingly find their services requested in endoscopy suites. There are numerous reasons, but the single most common factor is the increasing use of propofol. Despite clear trends indicating a greater demand for services, the safety record of out-of-operating room (OR) locations falls short of that in the OR. A variety of skills are required in the endoscopy suite, some of which are found in the core material of anesthesia training programs, and others that are not stressed in importance. The purpose of this article is to examine the methods of training that might be useful in producing anesthesia providers prepared for the challenges of the endoscopy suite and other out-of-OR locations, and speculate on how anesthesia training directors might address these needs.

The control of administration of drugs such as propofol is a task that is difficult to master. Two approaches to this task have emerged—target-controlled infusion, and patient-controlled sedation. In the first, a set point for drug in a hypothetical effect site is specified, and the controller delivers drug to hold the predicted concentration at that level. In the second, the patient administers small boluses of drug to maintain comfort. The theoretical basis of these approaches will be reviewed, available technology presented, and practical use of these devices discussed.

Respiratory obstruction is a frequent consequence of sedation due to the collapsibility of the velopharynx. Several approaches are available to eliminate this obstruction, including CPAP, mandibular advancement, nasal airways, and laryngeal mask airways. Practical approaches to the use of these measures are described.

BACKGROUND: Patient-controlled sedation (PCS) with propofol has been advocated as a method for dealing with the narrow therapeutic window for moderate sedation, but previous studies have methodologic limitations. We hypothesized that, by using remifentanil in conjunction with propofol and using PCS in both arms of the study, we could demonstrate marked improvements in facility use compared with fentanyl plus midazolam. METHODS: Fifty patients undergoing elective colonoscopy were randomized (with concealed allocation) to midazolam/fentanyl (group MF) or propofol/remifentanil (group PR) administered via PCS. Time intervals for sedation and recovery, perceptions by patient, nurse, and gastroenterologist, and need for anesthesiologist intervention were assessed. RESULTS: Group PR patients were sedated and recovered significantly more rapidly than did group MF (P 0.0001). In the group PR, recovery room time was actually shorter than procedure room time. Patient, nurse, and gastroenterologist perceptions were equivalent between the groups. Two patients in group PR required anesthesiologist intervention for arterial desaturation exceeding the primary safety end point. CONCLUSIONS: PCS with propofol/remifentanil yields superior facility throughput compared with midazolam/fentanyl when used in an appropriate care setting. (Anesth Analg 2008;106:434‐9)

Drug-induced sleep endoscopy (DISE) uses sedative-hypnotics to induce moderate obstruction in sleep apnea patients, thereby facilitating anatomic assessment of obstructive physiology. Implementation of DISE with propofol requires a dosing strategy that reliably and efficiently produces obstruction while minimizing oxygen desaturation.The surgeon in a prospective study of transoral robotic resection of the tongue base enrolled 97 patients with obstructive sleep apnea confirmed by polysomnography who failed continuous positive airway pressure. All patients were screened by DISE. Propofol dose was determined using custom software written in MATLAB, which has been previously described. Studies were performed in an operating room with standard monitors and resuscitation equipment. No topical anesthesia was used, and no IV drugs other than propofol were used. All patients received 2 L/min supplemental oxygen via a nasal cannula placed in the mouth. After initiation of propofol sedation, a pediatric bronchoscope was positioned via the naris to observe the velopharynx. The sedation sequence was continued until the clinical end point of obstruction onset was noted. Observation of the pharynx was performed for a sufficient period to obtain images of the anatomic site(s) of obstruction. The infusion was then terminated. Statistical analysis was performed with MATLAB (MathWorks, version 2012b). Comparison of saturation nadirs between DISE and subject sleep studies was performed with both the paired and unpaired Student t test.The subject population was characterized by a median body mass index of 32.1 (interquartile range [IQR] 6.8) kg/m and apnea-hypopnea index of 48 (IQR 32). All patients demonstrated obstruction within the design variables. Obstruction was observed after 236 (±57.9) seconds at an estimated effect-site concentration of 4.2 ± 1.3 mcg/mL. The median saturation nadir during DISE was significantly higher (91.4% (IQR 5.1)) than that during standard sleep studies (81.0% [IQR 11.2], P0.0001). Ninety-five percent confidence intervals for correlations between DISE saturation nadir and body mass index, age, apnea-hypopnea index, or administered propofol dose included zero in all cases.A propofol infusion strategy that requires limited experience with propofol dose selection and only 1 pump dosing change reliably produced airway obstruction in patients with severe sleep apnea. Clinical obstruction was achieved faster than target-controlled infusion-based systems for similar procedures reported in the literature. The observed degree of oxygen desaturation in the model system was within a clinically acceptable range.

The autonomic nervous system exerts important effects upon atrial fibrillation (AF) initiation. The strategy of anesthesia used during AF ablation may impact the provocation of AF triggers. We hypothesized that the use of general anesthesia (GA) would reduce the incidence of provokable AF triggers in patients undergoing AF ablation compared to patients studied while receiving only conscious sedation (CS).We performed a prospective, case control study comparing the incidence of provokable AF triggers in a consecutive series of patients undergoing AF ablation under GA using a standard trigger induction protocol. We compared the frequency and distribution of AF triggers to a second cohort of historical controls (matched for age, gender, left atrial dimension, and AF phenotype) who underwent ablation while receiving CS. We calculated that 44 total subjects (22 patients in each group) were required to detect a 50% reduction in the incidence of AF triggers in the GA cohort. There was no difference between the 2 groups in the rate of AF trigger inducibility (77% vs. 68%, P = 0.26) or the number of triggers provoked per patient (1.2 ± 0.8 vs. 1.3 ± 0.8, P = 0.38). Patients ablated under GA required higher doses of phenylephrine during the trigger induction protocol (408.3 mg [52-600] vs. 158.3 mg [0-75]; P = 0.003), and tended to require higher doses of isoproterenol to initiate triggers (92.8 mg [20-111] vs. 63.6 mg [6-103]; P = 0.25).AF trigger induction during GA is both safe and efficacious.

Sedative drugs decrease postural steadiness and increase the risk of injury from falls and accidents. The recovery rate is individual, making it hard to predict the patient's steadiness and hence safe discharge time. 103 outpatients sedated with midazolam and fentanyl were measured posturographically, before (PRE) and after (POST) endoscopy. The ability of conventional and nonlinear sway measures to separate the PRE and POST conditions were compared, and the area under the receiver operating characteristics curve (AUC) was used to quantify the significance of the separation. A nonlinear measure, fuzzy sample entropy, scored the largest AUC (AUCFSE = 0.83, p < 0.0001). While the AUCFSE was not significantly larger than the AUCs of conventional sway measures which offer easy quantification of postural steadiness, nonlinear measures provide more insight into the structure of postural control, which may help understand the effect of sedation on postural steadiness. This study is a step toward developing a tester that indicates a safe discharge time.

Anesthesiologists play a critical role in facilitating a positive perioperative experience and early recovery for patients. Depending on the kind of procedure or surgery, a wide variety of agents and techniques are currently available to anesthesiologists to administer safe and efficacious anesthesia. Notably, the fast-track or ambulatory surgery environment requires the use of agents that enable rapid induction, maintenance, and emergence combined with minimal adverse effects. Short-acting opioids demonstrate a safe and rapid onset/offset of effect; that short effect is both predictable and precise. It also ensures easier titration and reduced or rapidly reversed side effects. Due to their distinct pharmacokinetic and pharmacodynamic properties, and, in one case, rapid extra-hepatic clearance of remifentanil, these agents have several applications in general anesthesia.

Multidetector ECG-gated CT angiography permits imaging of structures such as the coronary arteries and pulmonary veins with peripheral administration of contrast media. Respiratory motion artifact limits the applicability of this technique in critically ill patients due to an inability to cooperate with prolonged breath holds necessary for quality images. A case in which high-frequency jet ventilation via an uncuffed tracheostomy tube in an unmedicated patient permitted respiratory immobilization sufficient to acquire diagnostic images, is presented.

We describe a 61-year-old female who underwent KTP laser ablation and CRE balloon dilatation of symptomatic idiopathic subglottic stenosis (50% obstruction). The procedure was conducted, using our standard approach for such cases, under total intravenous general anesthesia with subglottic high-frequency jet ventilation (HFJV) via Lindholm laryngoscope. The patient was enrolled in an ongoing investigational protocol in which respiratory inductance plethysmography (RIP; Ambulatory Monitoring Inc., Ardsley, N.Y., USA) bands were used to monitor ventilation in addition to pulse oximetry and visual inspection. HFJV instituted with an Acutronic Monsoon jet ventilator (Acutronic Medical, Hirzel, Switzerland) resulted in a rapid increase in RIP signal amplitude consistent with breath stacking and inadequate expiratory flow around the tight stenosis. High pressure alarms sounded and automatic cessation of jet ventilation ensued. After successful tracheal dilation under intermittent apnea, subsequent jet ventilation produced only modest RIP amplitude changes. RIP may be an important safety monitor during jet ventilation for patients with obstructive tracheal lesions to lessen the risk of both barotrauma and hypoventilation. RIP remains under active study by our group for this purpose.

Blunt laryngeal trauma is an uncommon injury associated with high prehospital mortality. Conventional airway management consists of awake tracheostomy. A case of laryngeal trauma associated with air bag deployment managed with tubeless suspension laryngoscopy with high frequency transglottic jet ventilation is presented. The advantages of this technique in the management of patients who are not good candidates for awake tracheostomy are discussed.

Contemporary techniques to enhance anatomical detail and catheter contact during atrial fibrillation (AF) ablation include (1) the integration of preacquired tomographic reconstructions with electroanatomical mapping (3-dimensional image integration [I-EAM]), (2) the use of steerable introducers (SIs), and (3) high-frequency jet ventilation (HFJV).To prove that using these stabilizing techniques during AF ablation improves 1-year procedural outcome.We studied 300 patients undergoing AF ablation at our institution. Patients were divided into 3 equal treatment groups (100 patients each) on the basis of the tools utilized: (1) group 1: AF ablation performed without I-EAM, SI, or HFJV; (2) group 2: AF ablation performed using I-EAM and SI, but without HFJV; and (3) group 3: AF ablation performed with I-EAM, SI, and HFJV. The primary outcome was freedom from AF 1 year after a single ablation procedure. The burden of both acute and chronic pulmonary vein reconnection was also assessed.Patients from groups 2 and 3 had significantly more nonparoxysmal AF (17% vs 30% vs 39%; P = .002), larger left atria (4.2 ± 0.8 cm vs 4.4 ± 0.7 cm vs 4.5 ± 0.8 cm; P.001), and higher body mass index (BMI; 28.5 ± 5.8 kg/m² vs 29.1 ± 4.8 kg/m² vs 31.2 ± 5.4 kg/m²; P.001). Despite these differences, with adoption of I-EAM, SI, and HFJV we noted a significant improvement in 1-year freedom from AF (52% vs 66% vs 74%; P = .006) as well as fewer acute (1.1 ± 1.2 vs 0.9 ± 1.1 vs 0.6 ± 0.9; P = .03) and chronic (3.5 ± 0.9 vs 3.2 ± 0.9 vs 2.4 ± 1.0; P = .02) pulmonary vein reconnections.The incorporation of contemporary tools to enhance anatomical detail and ablation catheter stability significantly improved 1-year freedom from AF after ablation.

Objectives/Hypothesis: To quantitatively measure changes in airway caliber at multiple anatomical levels during drug-induced sleep endoscopy (DISE) for evaluation of sleep apnea. We hypothesize that patients undergoing DISE will show: 1) collapse at multiple upper airway regions (retropalatal, retroglossal, and retroepiglottic), with greater collapse in the retropalatal region; and 2) greater anterior-posterior dimensional narrowing than the lateral. Study Design: Case series. Methods: Patients underwent DISE employing propofol as part of a nonrandomized prospective trial assessing candidacy for transoral robotic surgery intervention for sleep apnea. Images of the retropalatal, retroglossal, and retroepiglottic regions were captured during an initial period of light sedation and again in a period of deep sedation. Images were analyzed using software to measure the percent change in regional airway measurements as a result of DISE. Results: Thirty-seven sleep endoscopy videos were analyzed from patients with obstructive sleep apnea (apnea-hypopnea index: 42.9 ± 27.0 events/hour). Analyzable images were in the retropalatal (n = 24), retroglossal (n = 27), and retroepiglottic (n = 29) regions. The patients demonstrated mean reductions in airway area in the retropalatal (84.1 ± 18.7%), retroglossal (39.3 ± 37.5%), and retroepiglottic region (44.6 ± 42.8%). No statistically significant differences were found between lateral and anterior-posterior airway dimensional changes. Conclusions: Patients undergoing DISE had significant reductions in airway area at multiple regions under deep sedation with propofol. We conclude that collapse in the retropalatal region is greater than the hypopharyngeal region. This method can be used to quantitatively measure DISE upper airway changes, which could potentially be used as a means for understanding surgical outcomes in patients with sleep apnea. Laryngoscope, 2012

High frequency jet ventilation (HFJV) is a technique that is most frequently used in the intensive care unit and during tracheal and otorhinolaryngologic surgery. The utility of HFJV for procedures performed outside of the intensive care unit and operating room is currently being explored. The ability of HFJV to provide mechanical ventilation, yet achieve near static conditions of the chest and abdomen, makes it a very appealing technique for procedures such as pulmonary vein isolation and ablation for atrial fibrillation, targeted radiation therapy for lung and liver tumors, and certain diagnostic imaging techniques.

We present a unique, practical, and safe approach to the clinical management of a young male with a large tongue hemangioma who presented for serial surgical treatment of the lesion. Laser ablation was undertaken in the operating room under topical anesthesia with remifentanil analgosedation without the use of supplemental oxygen. Significant involution of the hemangioma was achieved without complication while the patient was awake, cooperative, and able to protect his airway. The application of remifentanil infusion for analgosedation during airway surgery is described. The utility of pharmacokinetic modeling in these applications is discussed along with the use of non-invasive respiratory inductance plethysmography to monitor ventilation during opioid sedation. The concept of analgosedation for airway surgery is introduced and relative risk versus benefit considerations of the approach in comparison to general anesthesia are discussed. This approach can be conceived of as an ORL endoscopy suite model for limited airway procedures.

We present a patient who experienced airway obstruction during an elective esophagogastroduodenoscopy (EGD) under anesthesia secondary to previously undiagnosed tracheomalacia. Physiology of airway obstruction with forced breathing maneuvers is discussed along with the potential advantages of dexmedetomidine-ketamine sedation for management of patients with achalasia undergoing outpatient endoscopic procedures.

During the past decade, robotic surgery has been progressively incorporated into the mainstream of cardio-thoracic and abdominopelvic surgery. With the recent US Food and Drug Administration approval of transoral robotic surgery (TORS) for the treatment of all benign tumors and select malignant tumors of the head and neck, robotic surgery has established its place in otolaryngologic surgery. Given the multispecialty applications and widespread use of robotic surgery, there exists a need for anesthesiologists to familiarize themselves with robotic surgery. This article focuses on TORS and the goal of which is to provide the anesthesiologist with a foundation for caring for the TORS patient in the perioperative period.

Epicardial ablation of ventricular tachycardia (VT) presents multiple challenges for anesthetic management. General anesthesia lowers blood pressure, may interfere with arrhythmia mapping, and use of muscle relaxants precludes identification of the phrenic nerve. We describe a case in which remifentanil with minimal doses of midazolam was employed in a series of epicardial VT ablations and noninvasive programmed stimulations (NIPS), including 5 external cardioversions and discuss the advantages of this approach.

BACKGROUND: High-frequency jet ventilation is an optimal mode of ventilation for many surgical procedures of the trachea and larynx but has limited monitoring modalities to assess adequacy of oxygenation and/or ventilation. Respiratory inductance plethysmography is a noninvasive monitor of chest and abdominal wall movement with well-established applications in the sleep laboratory. We performed an observational pilot study of respiratory inductance plethysmography as a detector of jet ventilation. METHODS: Twenty-five patients underwent microdirect suspension laryngoscopy with high-frequency jet ventilation under general anesthesia with total IV anesthesia. Inductotrace ® bands (Ambulatory Monitoring Inc., Ardsley, NY) were applied to the chest and abdomen in all patients and data collected from oxygen administration through emergence at 50-Hz sampling frequency in the DC mode using a 12-bit A-D converter and custom programmed LabVIEW interface. The raw data were filtered and a detector was developed based on a type I, IIR peak comb filter to differentiate apnea, cardiogenic oscillations, and jet ventilation-associated respiratory excursion. The primary end point was the ability of the detector to identify the presence of jet ventilation. Receiver operating characteristic curves were generated for the aggregate data of all patients. RESULTS: Respiratory inductance plethysmography reliably detected jet ventilation. The data analysis program effectively extracted a relatively small amplitude jet ventilation signal from a baseline signal contaminated by cardiogenic noise. Sensitivity was in the range of 85%, with a filter bandwidth of 0.055 Hz. Increased sensitivity with increasing filter bandwidth was offset by a detection delay of 12.5 seconds. CONCLUSIONS: Respiratory inductance plethysmography was successfully used to detect high-frequency jet ventilation in patients undergoing laryngotracheal surgery. This pilot study demonstrates the feasibility of respiratory inductance plethysmography as a monitor for use during jet ventilation.

Advances in minimally invasive procedures have resulted in an increased demand for procedural sedation. Patient-controlled sedation (PCS) has been in clinical use for almost 20 years, but has not been reviewed in over 10 years.Advances in microprocessor technology, increased demand for procedural sedation in a cost-conscious environment, and the availability of readily titratable pharmacologic agents together stimulated the development of alternative sedation practices. Continued research into the neurobiology of pain perception and the placebo effect has also played a role. PCS and patient-maintained sedation, primarily with propofol, have emerged as intriguing clinical alternatives to traditional sedation based in part on extensions of traditional PCA models.PCS has been applied to a wide variety of procedures, but systems that can be applied 'off-the-shelf' are not easy to tune. New approaches to PCS may address these limitations. Better understanding of the psychology of sedation may lead to better patient acceptance of PCS.

Objectives: This pilot study was designed to 1) identify predictors of difficult laryngeal exposure in obese patients, 2) develop strategies for efficient intubation and intraoperative visualization of the glottis, and 3) devise perioperative protocols for difficult laryngoscopies. Methods: We undertook a retrospective study over a 1-year period of 14 consecutive patients with a body mass index of more than 30 kg/m2 who underwent elective direct laryngoscopy under general anesthesia. Measurements of height, weight, neck circumference, Mallampati score, and Cormack-Lehane classification of the airway were recorded. Problems encountered during anesthesia induction and emergence were also noted. The laryngologist recorded on a visual analog scale the degree of difficulty encountered in obtaining a binocular stereoscopic view and magnification, illumination, and suspension. Results: Anatomic challenges during difficult laryngoscopy included decreased neck extension, redundant folds of tissue in the oropharynx and hypopharynx, and upper airway collapsibility. Overall, there was an association between the incidence of difficult laryngeal exposure and the Cormack-Lehane score (r = .57; p = .03), but the Mallampati score was of limited utility to the laryngologist. Neck size in female patients correlated with the Cormack-Lehane score (p = .02). Neither weight nor body mass index were predictive of a difficult laryngeal exposure. Straight blade laryngoscopes with a distal flange allowed greater depth of insertion and provided the best visualization of the glottis. Conclusions: An appropriate clinical examination may help predict a difficult airway. However, further studies are warranted to fully characterize the anatomic predictors of a difficult laryngeal exposure.