Transnasal Humidified Rapid-Insufflation Ventilatory Exchange for Deep Sedation in a Lung Transplant Candidate With Severe Cystic Fibrosis: A Case Report.

Transnasal humidified rapid-insufflation ventilatory exchange is a recently described technique for safer management of difficult airways and a novel ventilation technique under anesthesia. Its full potential in patient safety and benefits are still being investigated. We describe the use of transnasal humidified rapid-insufflation ventilatory exchange for deep sedation during dental extractions in a patient with severe cystic fibrosis as a precondition for lung transplantation. Patient wanted to have the procedure under general anesthesia with intubation due to extreme anxiety. However, we advocated deep IV sedation with transnasal humidified rapid-insufflation ventilatory exchange. Oxygenation was maintained without airway obstruction and pulmonary complications during the entire procedure of 110 minutes.

Determining the amount of training needed for competency of anesthesia trainees in ultrasonographic identification of the cricothyroid membrane.

BACKGROUND: Airway guidelines recommend the use of ultrasound to localize the cricothyroid membrane prior to airway manipulation in difficult airways. In this study, we aimed to determine the amount of training anesthesia trainees would need to achieve competence in bedside ultrasound to identify the cricothyroid membrane. METHODS: This is a prospective non-randomized cohort study in the Department of Anesthesia at Mount Sinai Hospital (Toronto, Ontario, Canada). Following institutional ethics approval, six anesthesia trainees consisting of four residents and two fellows underwent a 2-h training session on neck ultrasound to identify neck landmarks and the cricothyroid membrane. The trainees had no previous airway ultrasound experience. One-two weeks later, each trainee performed consecutive neck ultrasound scans on 20 healthy volunteers to identify the cricothyroid membrane. Cumulative sum (CUSUM) learning curves were constructed for each trainee. Primary outcome was the number of ultrasound examinations required to achieve competence, defined as 90% success rate in a series of 20 ultrasound scans. Secondary outcomes were the overall success rate, the time (sec.) required to perform the task, and 3-month skills assessment. RESULTS: CUSUM analysis showed four trainees achieved competence with a mean [range] success rate of 94.0% [90-100%] and a median [range] number of attempts of 14 [9-18]. Two trainees did not achieve competence, but obtained a success rate of 75.0 and 80.0% each. Overall (number of attempts) success rate was 88.3% (106/120) with a mean (SD) time of 36.9 (9.0) sec. Three months after training, ultrasound of five consecutive neck scans showed a mean success rate of 86.7% (26/30) and mean (SD) time of 47.7 (16.0) sec. CONCLUSIONS: After a short 2-h training session, most anesthesia trainees (n = 4/6) achieved competence in ultrasound-identification of the cricothyroid membrane with less than 20 scans in a mean time less than 60 s., and that they remain reasonably competent 3 months later. The learning curve for ultrasound identification of the cricothyroid membrane seems to be short even without prior airway ultrasound experience.

Role of contextualizing a crisis scenario on the performance of a cricothyrotomy procedural task.

PURPOSE: Simulation is an important alternative to evaluate cricothyrotomy, a rare life-saving procedure. This crossover study aimed to determine whether contextualization of a crisis scenario would impact the performance of a cricothyrotomy procedural task. METHODS: Sixty-five anesthesia assistants and emergency medicine and anesthesia residents underwent a teaching session in surgical cricothyrotomy using one of two sets of cricothyrotomy kits: the Portex 6.0 and Melker 3.5 (n = 32) or the Portex 6.0 and Melker 5.0 (n = 33). Within six weeks following the session, the participants performed cricothyrotomies on a full-body patient mannequin simulator coupled with a porcine larynx (tissue-mannequin simulator) using the assigned two kits in a "cannot intubate, cannot ventilate" (CICV) contextualized scenario (CS) and in a CICV verbalized non-contextualized scenario (NCS). Each participant performed a total of four cricothyrotomies using the two kits in the two scenarios. The primary outcome measure was insertion time, and secondary outcome measures were severity of injuries and failure rate. Outcome measures were compared between scenarios for each kit. RESULTS: Mean (SD) insertion time for a successful cricothyrotomy was not significantly different between NCS and CS for the Melker 3.5 [83.0 (45.0) sec vs 63.3 (36.1) sec, respectively; P = 0.96; mean difference (MD), 19.7 sec; 95% confidence interval (CI), -1.9 to 41.3], the Melker 5.0 [86.5 (36.8) sec vs 107.1 (55.6) sec, respectively; P = 0.11; MD, -20.6 sec; 95% CI, -44.9 to 3.7], and the Portex 6.0 [59.5 (35.5) sec vs 59.0 (35.0) sec, respectively; P = 0.95; MD, 0.5 sec; 95% CI, -13.2 to 14.2]. Failure rate and severity of injuries, measured as mean average injury score for each kit, were also similar between scenarios. CONCLUSIONS: Contextualization of a crisis scenario did not affect the performance of a cricothyrotomy procedural task on a tissue-mannequin simulator. These findings may have implications when considering the feasibility and cost-effectiveness for assessing the performance of cricothyrotomy procedural tasks.

Task- versus ego-oriented feedback delivered as numbers or comments during intubation training.

CONTEXT: Learners can focus on mastery (i.e. task orientation) or on learning relative to others (i.e. ego orientation). Previous research suggests task orientations are optimal for learning, a benefit usually linked to the suggestion that qualitative comments are better for learning than quantitative comparisons (i.e. grades). Yet, it is not clear if the observed effects are attributable to the feedback orientation (i.e. task versus ego), feedback format (i.e. comments versus numerical scores), or an interaction between the two. Here, we aimed to clarify the effects of feedback orientation and feedback format during simulation-based training in endotracheal intubation. METHODS: Forty-one medical students were randomly assigned to four feedback conditions: Task-oriented Numerical; Ego-oriented Numerical; Task-oriented Comment, and Ego-oriented Comment. Participants performed a total of 20 trials of endotracheal intubation. Pre-test, post-test and retention test assessments included the use of hand motion analysis and a global rating scale (GRS). Participants rated feedback credibility, self-assessment and self-confidence using Likert-type scales. Analyses of variance were used to examine group differences. RESULTS: Participants' performance did not differ significantly on the easiest (p > 0.2) or two complex variations of intubation (p > 0.3). For the moderately difficult variation, analyses of hand motion and GRS data revealed significant group differences at post-test (p < 0.05), but no differences on the retention test. Analysis of participants' perceptions showed significant interactions whereby the Ego-oriented Numerical group rated feedback credibility (p < 0.01) higher than the Task-oriented Numerical group; the two Comment groups did not differ. Some participants recounted negative experiences with the feedback they received. CONCLUSIONS: Medical students responded to feedback in ways that challenge previous education research. Specifically, students preferred and improved more in the short term (but not at retention) when receiving Ego-oriented feedback in Numerical form. Although learning retention did not differ significantly across feedback conditions, students' perceptions of themselves and of the teacher and training environment did differ and the implications for trainees' future learning must be considered.

Teaching lifesaving procedures: the impact of model fidelity on acquisition and transfer of cricothyrotomy skills to performance on cadavers.

BACKGROUND: A decline in emergency surgical airway procedures in recent years has resulted in a decreased exposure to cricothyrotomy. Consequently, residents have very little experience or confidence in performing this intervention. In this study, we compared cricothyrotomy skills acquired on a simple inexpensive model to those learned on a high fidelity simulator using valid evaluation instruments and testing on cadavers. METHODS: First and second year anesthesiology residents were recruited. All subjects performed a videotaped pretest cricothyrotomy on cadavers. Subjects were randomized into two groups: The high fidelity group (n = 11) performed two cricothyrotomies on a full-scale simulator with an anatomically accurate larynx. The low fidelity group (n = 11) performed two cricothyrotomies on a low fidelity model constructed from corrugated tubing. Within 2 wk all subjects performed a posttest. Two blinded examiners graded and timed the performances using a checklist and a global rating scale. RESULTS: There was no significant difference in the change from pretest to posttest performance between the model groups as evaluated by all three measures (all: P = NS). Training on both models significantly improved performance on all measures (all: P < 0.001). Inter-rater reliability was strong (checklist: r = 0.90; global rating scale: r = 0.89). CONCLUSIONS: Our study shows that a simple inexpensive model achieved the same effect on objectively rated skill acquisition as did an expensive simulator. The skills acquired on both models transferred effectively to cadavers. Training for this life-saving skill does not need to be limited by simulator accessibility or cost.

Selective enhancement of tonic GABAergic inhibition in murine hippocampal neurons by low concentrations of the volatile anesthetic isoflurane.

Volatile (inhaled) anesthetics cause amnesia at concentrations well below those that cause loss of consciousness and immobility; however, the underlying neuronal mechanisms are unknown. Although many anesthetics increase inhibitory GABAergic synaptic transmission, this effect occurs only at high concentrations (>100 microm). Molecular targets for low concentrations of inhaled anesthetics have not been identified. Here, we report that a tonic inhibitory conductance in hippocampal pyramidal neurons generated by alpha5 subunit-containing GABA(A) receptors is highly sensitive to low concentrations of the volatile anesthetic isoflurane (ISO) (25 and 83.3 microm). The alpha5 subunit is necessary for enhancement of the tonic current by these low concentrations of isoflurane because potentiation is absent in neurons from alpha5-/- mice. Furthermore, ISO (25 microm) potentiated recombinant human alpha5beta3gamma2L GABA(A) receptors, whereas this effect was not seen with alpha1beta3gamma2L GABA(A) receptors. These studies suggest that an increased tonic inhibition in the hippocampus may contribute to amnestic properties of volatile anesthetics.

Tonic inhibition in mouse hippocampal CA1 pyramidal neurons is mediated by alpha5 subunit-containing gamma-aminobutyric acid type A receptors.

The principal inhibitory neurotransmitter in the mammalian brain, gamma-aminobutyric acid (GABA), is thought to regulate memory processes by activating transient inhibitory postsynaptic currents. Here we describe a nonsynaptic, tonic form of inhibition in mouse CA1 pyramidal neurons that is generated by a distinct subpopulation of GABA type A receptors (GABA(A)Rs). This tonic inhibitory conductance is predominantly mediated by alpha5 subunit-containing GABA(A)Rs (alpha5GABA(A)Rs) that have different pharmacological and kinetic properties compared to postsynaptic receptors. GABA(A)Rs that mediate the tonic conductance are well suited to detect low, persistent, ambient concentrations of GABA in the extracellular space because they are highly sensitive to GABA and desensitize slowly. Moreover, the tonic current is highly sensitive to enhancement by amnestic drugs. Given the restricted expression of alpha5GABA(A)Rs to the hippocampus and the association between reduced alpha5GABA(A)R function and improved memory performance in behavioral studies, our results suggest that tonic inhibition mediated by alpha5GABA(A)Rs in hippocampal pyramidal neurons plays a key role in cognitive processes.