Joshua H. Atkins

Recent advances in patient-controlled sedation.

Purpose of review 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. Recent findings 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. Summary 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.

A Review of Perioperative Glucose Control in the Neurosurgical Population

Significant fluctuations in serum glucose levels accompany the stress response of surgery or acute injury and may be associated with vascular or neurologic morbidity. Maintenance of euglycemia with intensive insulin therapy (IIT) continues to be investigated as a therapeutic intervention to decrease morbidity associated with derangements in glucose metabolism. Hypoglycemia is a common side effect of IIT with potential for significant morbidity, especially in the neurologically injured patient. Differences in cerebral versus systemic glucose metabolism, the time course of cerebral response to injury, and heterogeneity of pathophysiology in neurosurgical patient populations are important to consider in evaluating the risks and benefits of IIT. While extremes of glucose levels are to be avoided, there are little data to support specific use of IIT for maintenance of euglycemia in the perioperative management of neurosurgical patients. Existing data are summarized and reviewed in this context.

Safety and efficacy of drug-induced sleep endoscopy using a probability ramp propofol infusion system in patients with severe obstructive sleep apnea.

BACKGROUND: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. METHODS: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. RESULTS:The subject population was characterized by a median body mass index of 32.1 (interquartile range [IQR] 6.8) kg/m2 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], P < 0.0001). 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. CONCLUSIONS: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.

Global health outreach during anesthesiology residency in the United States: a survey of interest, barriers to participation, and proposed solutions ☆

STUDY OBJECTIVE To assess the interest in and barriers to pursuing global health outreach (GHO) experiences for anesthesiology residents in the United States. DESIGN Survey instrument. SETTING Academic department of anesthesiology. SUBJECTS Anesthesiology residents who were members of the American Society of Anesthesiologists (ASA). MEASUREMENTS An online survey was administered to residents in anesthesiology via the ASA membership database. Descriptive statistics, including means, frequencies, and percentages were calculated. MAIN RESULTS 91% of participants indicated an interest in GHO, of whom fewer than half (44%) had done a GHO medical mission. Seventy-nine percent reported that GHO affected their current practice or education; 33% commented they were now less wasteful with supplies and resources. Permission from work or obtaining work coverage were the primary barriers for both those with and without previous GHO participation. Of all respondents, 78% agreed that the availability of a GHO residency track would influence their ranking of that program for training, and 71% would pursue a GHO fellowship if available. CONCLUSIONS Anesthesiology residents have an interest in residency and fellowship GHO programs. Formalization of GHO programs during training may reduce work-related barriers associated with GHO participation and broaden academic program recruitment.

Technologies to shape the future: proteomics applications in anesthesiology and critical care medicine.

Broadly speaking, proteomics is concerned with the simultaneous characterization of the features (for example, the concentration or activity) of the many different proteins that are typically found in biological or clinical specimens. The field is being driven forward both by innovative biotechnology companies and by academicians who are introducing the technology required for the parallel identification of individual proteins. The technology currently relies heavily on two-dimensional gel electrophoresis combined with mass spectrometry, but protein microarray chips are rapidly becoming a reality. Protein biomarkers are increasingly being recognized as crucially important for the study of disease processes, both from diagnostic and prognostic points of view. Proteome level studies will therefore be used increasingly both to identify and follow the course of various pathological conditions. In the specialty of anesthesiology, this technology will allow an improved understanding of the mechanisms of action of many of the drugs that are routinely administered in the operating room and also the effects of these therapeutic drugs on protein expression. In addition, proteomic studies will increasingly be used for both diagnostic and prognostic purposes in the intensive care unit and the chronic pain clinic.

Performance of Masimo rainbow acoustic monitoring for tracking changing respiratory rates under laryngeal mask airway general anesthesia for surgical procedures in the operating room: a prospective observational study.

BACKGROUND: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. METHODS: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. RESULTS: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 rate >4 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). CONCLUSIONS: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.

Anesthetic considerations and surgical caveats for awake airway surgery.

The evolution of novel techniques for the treatment of laryngeal pathology has led to a significant expansion of the role of diagnostic assessment and the range of laryngeal procedures performed. These procedures typically benefit from an anesthetic approach that diverges from a standard general endotracheal or laryngeal mask airway-based inhalational anesthetic. The shared airway, need for intraoperative assessment of vocal cord function, risk of airway fire, and desire for rapid emergence and discharge are all important factors. In this article the authors undertake a collaborative anesthesia-surgical discussion of anesthetic management for airway procedures that are optimally performed with a spontaneously breathing, cooperative patient. An overview of pharmacologic approaches to airway anesthesia and cooperative sedation, followed by a discussion on the surgical requirements and anesthetic goals of commonly performed procedures, are presented.

Toxicities and early outcomes in a phase 1 trial of photodynamic therapy for premalignant and early stage head and neck tumors.

OBJECTIVES Management of early superficial lesions in the head and neck remains complex. We performed a phase 1 trial for high-grade premalignant and early superficial lesions of the head and neck using photodynamic therapy (PDT) with Levulan (ALA). MATERIALS AND METHODS Thirty-five subjects with high grade dysplasia, carcinoma in situ, or microinvasive (⩽1.5mm depth) squamous cell carcinoma were enrolled. Cohorts of 3-6 patients were given escalating intraoperative light doses of 50-200J/cm(2) 4-6h after oral administration of 60mg/kg ALA. Light at 629-635nm was delivered in a continuous (unfractionated) or fractionated (two-part) schema. RESULTS PDT was delivered to 30/35 subjects, with 29 evaluable. There was one death possibly due to the treatment. The regimen was otherwise tolerable, with a 52% rate of grade 3 mucositis which healed within several weeks. Other toxicities were generally grade 1 or 2, including odynophagia (one grade 4), voice alteration (one grade 3), and photosensitivity reactions. One patient developed grade 5 sepsis. With a median follow-up of 42months, 10 patients (34%) developed local recurrence; 4 of these received 50J/cm(2) and two each received 100, 150, and 200J/cm(2). Ten (34%) patients developed recurrence adjacent to the treated field. There was a 69% complete response rate at 3months. CONCLUSIONS ALA-PDT is well tolerated. Maximum Tolerated Dose appears to be higher than the highest dose used in this study. Longer followup is required to analyze effect of light dose on local recurrence. High marginal recurrence rates suggest use of larger treatment fields.

Laser ablation of a large tongue hemangioma with remifentanil analgosedation in the ORL endoscopy suite.

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.

Tracheostomy Complications as a Trigger for an Airway Rapid Response: Analysis and Quality Improvement Considerations.

Objective To analyze the subset of airway rapid response (ARR) calls related to tracheostomy identified over a 46-month period from August 2011 to May 2015 to determine proximate cause, intervention, and outcome and to develop process improvement initiatives. Design Single-institution multidisciplinary retrospective cohort study. Setting Tertiary care academic medical center in a large urban setting. Subjects Hospital inpatients with an in situ tracheostomy or laryngectomy who experienced an ARR. Methods Detailed review of operator, hospital, and patient records related to ARR system activations over a 46-month period. Results ARR was activated for 28 patients with existing tracheostomy. The cohort included open tracheostomy (n = 14), percutaneous tracheostomy (n = 8), laryngectomy stoma (n = 3), and indeterminate technique (n = 3). The most frequent triggers for emergency airway intervention were decannulation (n = 16), followed by mucus plugging (n = 4). The mean body mass index of ARR patients was higher than that of a comparator tracheostomy cohort (32.9 vs 26.3, P < .001). BMI was >40 in 9 ARR patients. There was 1 mortality in the series. Conclusions Tracheostomy is a major trigger for ARR with potential fatal outcome. Factors that may contribute to tracheostomy emergencies include high body mass index, surgical technique for open tracheostomy or percutaneous tracheostomy, tracheostomy tube size, and bedside tracheostomy management. Results have triggered a hospital-wide practice improvement plan focused on tracheostomy awareness and documentation, discrete process changes, and implementation of guidelines for emergency management.