Maryam Dosani

Defining the reliability of sonoanatomy identification by novices in ultrasound-guided pediatric ilioinguinal and iliohypogastric nerve blockade.

BACKGROUND: The ilioinguinal (II)/iliohypogastric (IH) nerve block is a safe, frequently used block that has been improved in efficacy and safety by the use of ultrasound guidance. We assessed the frequency with which pediatric anesthesiologists with limited experience with ultrasound-guided regional anesthesia could correctly identify anatomical structures within the inguinal region. Our primary outcome was to compare the frequency of correct identification of the transversus abdominis (TA) muscle with the frequency of correct identification of the II/IH nerves. We used 2 ultrasound machines with different capabilities to assess a potential equipment effect on success of structure identification and time taken for structure identification. METHODS: Seven pediatric anesthesiologists with <6 mo experience with ultrasound-guided regional anesthesia performed a total of 127 scans of the II region in anesthetized children. The muscle planes and the II and IH nerves were identified and labeled. The ultrasound images were reviewed by a blinded expert to mark accuracy of structure identification and time taken for identification. Two ultrasound machines (Sonosite C180plus and Micromaxx, both from Sonosite, Bothell, WA) were used. RESULTS: There was no difference in the frequency of correct identification of the TA muscle compared with the II/IH nerves (&khgr;2 test, TA versus II, P = 0.45; TA versus IH, P = 0.50). Ultrasound machine selection did show a nonsignificant trend in improving correct II/IH nerve identification (II nerve &khgr;2 test, P = 0.02; IH nerve &khgr;2 test, P = 0.04; Bonferroni corrected significance 0.17) but not for the muscle planes (&khgr;2 test, P = 0.83) or time taken (1-way analysis of variance, P = 0.07). A curve of improving accuracy with number of scans was plotted, with reliability of TA recognition occurring after 14–15 scans and II/IH identification after 18 scans. CONCLUSIONS: We have demonstrated that although there is no difference in the overall accuracy of muscle plane versus II/IH nerve identification, the muscle planes are reliably identified after fewer scans of the inguinal region. We suggest that a reliable end point for the inexperienced practitioner of ultrasound-guided II/IH nerve block may be the TA/internal oblique plane where the nerves are reported to be found in 100% of cases.

Spontaneous respiration during intravenous anesthesia in children.

Purpose of review Maintaining spontaneous respiration during intravenous anesthesia for investigative and surgical procedures may avoid the need for airway instrumentation and reduce the risk of desaturation. In addition, when performing airway endoscopic procedures in children, maintaining spontaneous respiration while using intravenous anesthesia can reduce the need for endotracheal intubation. This facilitates improved access to the smaller airway, allows assessment of the dynamic function of the airway, and reduces exposure of personnel to inhaled anesthetic agents. Recent findings Anesthetic hypnotic and analgesic agents are potent dose-dependent depressants of respiration. Infants have historically been considered to be at a higher risk of respiratory depression, especially from opioid analgesics. However, recent evidence suggests that infants and younger children outside the neonatal period are more resistant to the effects of remifentanil, even when combined with propofol. Spontaneous respiration can be maintained at doses adequate to suppress somatic responses to painful procedures. The large inter-individual variation in respiratory depressant effects necessitates individualized dose titration. The drug dose is more linearly related to variation in the respiratory rhythm and respiratory rate than to minute volume or end-tidal carbon dioxide. Apneic episodes are less likely when respiratory depressant drugs are administered slowly, as this allows time for the end-tidal carbon dioxide level to rise to a new apneic threshold. Hypnotic anesthetics and opioid analgesics act synergistically to cause respiratory depression and suppression of the somatic response. Summary Spontaneous respiration can be maintained when anesthetizing children using intravenous anesthesia.

Slower administration of propofol preserves adequate respiration in children

Background:  Propofol is a versatile anesthetic agent used in pediatric practice to facilitate investigational and interventional procedures. Propofol can cause significant respiratory depression, the management of which may require advanced airway management skills. This investigation aimed to increase the safety of propofol administration by developing a dosing schedule that would preserve spontaneous respiration in at least 95% of subjects.

Clinical evaluation of algorithms for context-sensitive physiological monitoring in children

BACKGROUND Subtle changes in monitored physiological signals might be used to guide clinical actions and give early warning of potential adverse events. Automated early warning systems could enhance the clinicians interpretation of data by instantaneously processing new information and presenting it within the context of previous observations. In this study, we tested algorithms for tracking the behaviour of dynamic physiological systems and automatically detecting key events over time. METHODS Algorithms were activated in real-time during anaesthesia to run context-sensitive monitoring of six variables (end-tidal PCO(2), heart rate, exhaled minute ventilation, non-invasive arterial pressure, respiratory rate, and oxygen saturation), alongside standard physiological monitors. The clinical evaluation included real-time feedback on each change point (change in the physiological trend) detected by the algorithms and the completion of a usability questionnaire. RESULTS Fifteen anaesthetists completed the evaluation during paediatric surgical cases. A total of 38 cases were evaluated, with a mean duration of 103 (102) min. The mean number of change points per case was 22.8 (23.4). Sixty-one per cent of all rated change points were considered clinically significant, and <7% were due to artifacts. CONCLUSIONS The algorithms were able to detect a range of clinically significant physiological changes during paediatric anaesthesia, and were considered useful by participating anaesthetists. These findings indicate that automated detection of context-sensitive changes is possible and could be used by early warning systems during physiological monitoring. Further investigations are required to assess how this information can best be communicated to the anaesthetist.

Defining rules for the identification of critical ventilatory events

Purpose: The automated recognition of critical clinical events by physiological monitors is a challenging task exacerbated by a lack of standardized and clinically relevant threshold criteria. The objective of this investigation was to develop consensus for such criteria regarding the identification of three ventilatory events: disconnection or significant leak in the anesthesia circuit, decreased lung compliance or increased resistance, and anesthetic overdose from inhaled anesthetics.Methods: We individually administered a structured interview to five expert anesthesiologists to gain insight into the cognitive processes used by clinicians to diagnose ventilatory events and to determine the common heuristics (rules of thumb) used in clinical practice. We then used common themes, identified from analysis of the structured interviews, to generate questions for a series of web-based questionnaires. Using a modified Delphi technique, iterative questionnaire administration facilitated rapid consensus development on the thresholds for the specific rules used to identify ventilatory events.Results: A threshold for 75% agreement was described for each scenario in a healthy ventilated adult. A disconnection or significant leak in the anesthesia circuit is diagnosed with peak airway pressure (<5 cm H2O or change of 15 cm H2O), ETCO2 (0 mmHg, 40% drop, or value below 10 mmHg for a duration of 20 sec), and inspired-expired volume difference (300 mL). Increased resistance or decreased lung compliance is diagnosed with high peak airway pressure (40 cm H2O or a 20 cm H2O change), asymmetry of capnogram, and changes in measured compliance or resistance. Anesthetic overdose from inhaled anesthetics is diagnosed with high end-tidal anesthetic agent concentration (2 MAC in a patient less than 60 yr of age or 1.75 MAC in a patient over 60 yr of age), low systolic blood pressure (below 60 mmHg), and low modified electroencephalogram (bispectral index or entropy).Conclusion: This investigation has provided a set of consensus-based criteria for developing rules for the identification of three critical ventilatory events and has presented insight into the decision heuristics used by clinicians.RésuméObjectif: La reconnaissance automatisée des événements cliniques critiques par des moniteurs physiologiques constitue un défi rendu difficile par le manque de critères de seuils standardisés et pertinents d’un point de vue clinique. L’objectif de cette étude était de parvenir à un consensus par rapport aux critères nécessaires à l’identification de trois événements respiratoires : une déconnexion ou une fuite considérable du circuit anesthésique, une compliance pulmonaire diminuée ou une résistance accrue, et une overdose anesthésique résultant des anesthésiques inhalés.Méthode: Nous avons individuellement mené des entretiens structurés de cinq anesthésiologistes experts afin d’avoir un aperçu des processus cognitifs utilisés par les cliniciens pour dépister les événements respiratoires et de déterminer les connaissances heuristiques communes (règle empirique) utilisées dans la pratique clinique. Ensuite, nous nous sommes servis des thèmes communs identifiés par l’analyse des entretiens structurés afin de générer des questions pour une série de questionnaires en ligne. À l’aide d’une méthode de Delphi modifiée, l’administration itérative des questionnaires a permis le développement rapide d’un consensus concernant les seuils pour les règles spécifiques utilisées dans l’identification des événements respiratoires.Résultats: Pour chaque scénario chez un adulte sain ventilé, un seuil de concordance de 75 % a été décrit. Une déconnexion ou fuite considérable du circuit anesthésique est diagnostiquée lors d’une pression maximale du conduit aérien (< 5 cm H2O ou changement de 15 cm H2O), ETCO2 (0 mmHg, chute de 40 %, ou valeur en dessous de 10 mmHg pour une durée de 20 sec), et d’une différence de volume inspiré-expiré (300 mL). Une résistance accrue ou une compliance pulmonaire réduite est diagnostiquée lors d’une pression maximale du conduit aérien élevée (40 cm H2O ou un changement de 20 cm H2O), un capnogramme asymétrique, et de changements dans la compliance ou la résistance mesurées. Une overdose anesthésique provoquée par les anesthésiques inhalés est diagnostiquée lors d’une concentration d’anesthésique télo-expira-toire élevée (2 MAC chez un patient de moins de 60 ans ou 1,75 MAC chez un patient de plus de 60 ans), de pression systolique basse (inférieure à 60 mmHg) et d’électroencéphalogramme modifié bas (index bispectral ou moniteur entropy).Conclusion: Cette étude a permis de déterminer un ensemble de critères basés sur un consensus pour le développement de règles permettant l’identification de trois événements respiratoires critiques et a donné un aperçu des connaissances heuristiques utilisés par les cliniciens pour prendre des décisions cliniques.

A vibro-tactile display for clinical monitoring: real-time evaluation.

BACKGROUND: Vibro-tactile displays use human skin to convey information from physiological monitors to anesthesiologists, providing cues about changes in the status of the patient. In this investigation, we evaluated, in a real-time clinical environment, the usability and wearability of a novel vibro-tactile display belt recently developed by our group, and determined its accuracy in identifying events when used by anesthesiologists. METHODS: A prospective observational study design was used. During routine anesthesia, a standard physiological monitor was connected to a software tool that used algorithms to automatically identify changing trends in mean noninvasive arterial blood pressure, expired minute ventilation, peak airway pressure, and end-tidal carbon dioxide partial pressure. The software was wirelessly interfaced to a vibro-tactile belt worn by the anesthesiologist. Each physiological variable was mapped to 1 of 4 tactor locations within the belt. The direction (increase/decrease) and 2 levels of change (small/large) were encoded in the stimulation patterns. A training session was completed by each anesthesiologist. The system was activated in real-time during anesthesia alongside routine physiological monitors. When the algorithms detected changes in the patient, the belt vibrated at the appropriate location with the pattern corresponding to the level and direction of change. Using a touch screen monitor the anesthesiologist was to enter the vibro-tactile message by first identifying the variable, then identifying the level and direction of change. Usability and wearability questionnaires were to be completed. The percentage of correct identification of the physiological trend, the direction of change, and the level of change were primary outcome variables. The mean usability score and wearability results were secondary outcome variables. We hypothesized that anesthesiologists would correctly identify the events communicated to them through the vibro-tactile belt 90% of the time, and that anesthesiologists would find the vibro-tactile belt usable and wearable. RESULTS: Seventeen anesthesiologists evaluated the display during 57 cases. The belt was operational for a mean (SD) duration of 75 (41) minutes per case. Seven cases were excluded from analysis because of technical failures. Eighty-one percent (confidence interval [CI], 77% to 84%) of all stimuli were decoded. The physiological trend, the direction of change, and the level of change were correctly identified for 97.7% (CI 96%–99%), 94.9% (CI 92%–97%), and 93.5% of these stimuli (CI, 91%–96%), respectively. Fourteen anesthesiologists completed the usability and wearability questionnaires. The mean usability score was 4.8 of a maximum usability score of 7. CONCLUSIONS: Anesthesiologists found a vibro-tactile belt to be wearable and usable and could accurately decode vibro-tactile messages in a real-time clinical environment.

48: Referral Pattern and Outcome of Patients Receiving Palliative Radiotherapy to Spinal Metastases Based on the Spinal Instability Neoplastic Score

S19 _________________________________________________________________________________________________________ positive margins [OR 4.15(3.15-5.47); p < 0.0001], ECE [OR 5.78(4.41-7.58); p < 0.0001], SVI [OR 4.10(2.88-5.85); p < 0.0001], and Gleason score 8-10 [OR 2.90(1.97-4.26); p < 0.0001]. Cancer centre was also predictive of referral rates (range 5.68% to 65.63% p < 0.0001). Patients seen by RO post-RP were almost twice as likely to have seen RO prior to RP [OR 1.94(1.51-2.49); p < 0.0001]. Patient age, distance from an RT facility, neighbourhood income quintile, RP centre surgical volume, and affiliation of RP hospital with a cancer centre were not associated with the likelihood of RO consultation. On multivariate analysis of determinants of receiving ART, younger age [OR 1.029(1.004-1.054); p = 0.024] and adverse pathologic features, including positive margins [OR 4.34(3.09-6.11); p < 0.0001], ECE [OR 8.13(5.26-12.50); p < 0.0001], SVI [OR 3.33(2.32-4.81); p < 0.0001], and Gleason score 8-10 [OR 2.53(1.68-3.82); p < 0.0001] remained strongly associated with the use of ART. The use of ART varied significantly across cancer centre regions (range 1.14% to 19.37% of all RP patients, p = 0.0002). Conclusions: Over 40% of patients have high-risk features following RP and may benefit from ART, but many do not receive early RO referral. Cancer Centre is strongly predictive of both referral and ART use. An effort should be made to understand and reduce large inter-centre variations in access to RT post-RP for patients with high-risk prostate cancer.

Inter-feature Transfer Of Aftereffects: Evidence of Adaptation in Whole Face Representations

DISCUSSION • Inter-feature transfer can (but does not reliably) occur in the adaptation of identity in representations of upright faces, consistent with representations in which upper and lower faces are integrated. • Insufficient evidence regarding transfer for inverted faces (within-feature adaptation too weak) • Facial expression did not show any evidence of interfeature transfer of aftereffects. This raises the question as to whether expression information is more part-based. METHODS & RESULTS Original (unmorphed) half-faces used as adapting stimuli. Fantamorph 3.0 (www.fantamorph.com) generated morphed faces between two identities, for test stimuli. All adapting and test face stimuli segmented into upper and lower halves.

Monitor-decoupled pharmacodymamics of propofol in children using State Entropy as the clinical end point

This paper presents two alternative approaches to characterize the pharmacodynamics of propofol anesthesia in children, using State Entropy as a clinical end point. The first approach is the traditional approach where the pharmacodynamic model is described in terms of an effect-site equilibration rate constant and the Hill equation. In the second approach (the monitor-decoupled approach) the dynamics of the Entropy monitor is identified and added to the traditional pharmacodynamic model. The traditional approach resulted in mean ke0 values of 2.08min−1 and 1.27min−1 for the Paedfusor and Kataria pharmacokinetic models, respectively. The monitor-decoupled approach resulted in significantly larger values (mean ke0 values of 2.57min−1 and 1.71min−1) than the traditional approach. The differences between ke0 values suggest that the dynamic effect of the Entropy monitor must be accounted for when identifying the “true” pharmacodynamics of the patient, without the bias caused by the monitors processing characteristics. The values of ke0 obtained in this study were larger than those values previously published for the Bispectral Index. This is likely due to the different processing characteristics of the Entropy and Bispectral Index monitors, as well as the use of different pharmacokinetic models.