Cardiopulmonary effects of apneustic anesthesia ventilation in anesthetized pigs: a new mode of ventilation for anesthetized veterinary species.

Objective: To compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in anesthetized pigs and to describe a new mode of ventilation for anesthetized veterinary species. Study design: Randomized, crossover design without washout. Animals: Twelve healthy, female white Landrace pigs. Methods: Following ketamine-midazolam premedication and anesthetic induction with propofol, the trachea was intubated, and each pig was positioned in dorsal recumbency. Anesthesia was maintained with propofol and sufentanil infusions. Pigs were instrumented and their lungs were sequentially ventilated with each mode, in random order, for 1 h according to predefined criteria [fraction of inspired oxygen (FiO2) = 0.21, 10 mL kg-1 tidal volume (VT), and arterial carbon dioxide tension (PaCO2) within 40-45 mmHg]. Cardiopulmonary data were collected at baseline, 30 and 60 min. In 8 pigs, thoracic computed tomography (CT) was performed following the 60 min time point for each mode of ventilation and images were analyzed to quantify lung aeration. The effects of ventilation mode, time, and order were analyzed using repeated measures ANOVA. Paired t-tests were used to compare lung aeration between modes. Significance was defined as p < 0.05. Results: Data from 12 pigs were analyzed. A significant effect of mode was found for heart rate, mean arterial pressure (MAP), pulmonary artery occlusion pressure, cardiac index (CI), stroke volume index, systemic vascular resistance, pulmonary vascular resistance, oxygen delivery index (DO2I), oxygen extraction ratio (O2ER), VT, arterial oxygen tension, arterial hemoglobin saturation, PaCO2, end-tidal carbon dioxide tension, alveolar dead space (VDalv/VTalv), venous admixture ( Q . s / Q . t ), mean airway pressure, and dynamic compliance index (CRSI). Order effects were also observed for some cardiovascular and respiratory variables. For the eight pigs that underwent thoracic CT, AAV resulted in significantly larger proportions of normally and hyperaerated lung while CMV resulted in larger proportions of hypoaerated and atelectatic lung. Conclusions: In dorsally recumbent anesthetized pigs, ventilated with FiO2 = 0.21, both modes of ventilation supported adequate oxygenation while AAV resulted in higher CRSI, and lower VDalv/VTalv and Q . s / Q . t , compared with CMV. AAV was also associated with lower MAP, CI, and DO2I and higher O2ER compared with CMV. Further investigation of AAV in anesthetized animals is warranted.

Apneustic anesthesia ventilation improves pulmonary function in anesthetized bottlenose dolphins (Tursiops truncatus).

Introduction: Use of mechanical ventilation during general anesthesia is a necessary practice in the anesthetization of small cetaceans as spontaneous ventilation fails to provide adequate gas exchange. Currently available methods of ventilation do not account for the intermittent breathing strategy of representative species within this infraorder of fully aquatic mammals and may have a significant effect on cardiac and respiratory physiology. Methods: To understand the impact of mechanical ventilation on cardiopulmonary function in one small species of cetacean, the bottlenose dolphin (Tursiops truncatus), we compared controlled mechanical ventilation (CMV) to a novel ventilation method known as apneustic anesthesia ventilation (AAV). AAV simulates the normal inspiratory breath-hold pattern of dolphins. Ten anesthetic procedures (dental procedure, n = 9; bronchoscopy, n = 2) were performed on nine dolphins (age range: 10-42 years; mean = 32 years; median = 37 years; female = 3, 40%; male = 6, 60%). In a cross-over study design, dolphins were instrumented and randomly assigned to AAV or CMV as the initial mode of ventilation, then switched to the alternate mode. Baseline cardiopulmonary data were collected and again after 30 min on each mode of ventilation. Cardiac index, stroke volume index, systemic vascular resistance, alveolar dead space, alveolar-arterial oxygen tension gradient, arterial oxygen content, oxygen delivery index, and dynamic respiratory system compliance index were calculated at each of the four time points. Results: During AAV, dolphins had higher arterial oxygen tension, higher mean airway pressure, reduced alveolar dead space ventilation and lower alveolar-arterial oxygen difference. Cardiovascular performance was not statistically different between the two modes. Discussion: Our study suggests AAV, which more closely resembles the conscious intermittent respiratory pattern phenotype of dolphins, improves ventilation and pulmonary function in the anesthetized dolphin. Future studies should evaluate the cardiopulmonary effects of neutral buoyancy and cardiopulmonary sparing drug protocols to reduce the need for hemodynamic support of current protocols.

Pelvic limb anesthesia and analgesia in dogs undergoing tibial plateau leveling osteotomy (TPLO): A survey of board-certified anesthesiologists.

OBJECTIVE: To report the locoregional anesthesia and analgesia preferences of veterinary anesthesiologists for use in dogs undergoing a TPLO and determine any association with specialty college, time from board-certification, or employment sector. STUDY DESIGN: Cross sectional study. SAMPLE POPULATION: Diplomates of the American (ACVAA) and European (ECVAA) Colleges of Veterinary Anesthesia and Analgesia. METHODS: An electronic survey was distributed to diplomates and responses were used to determine associations between preferred methods. RESULTS: The survey response rate was 28% (141/500) with 69% (97/141) of ACVAA diplomates and 31% of diplomates with ECVAA (44/141) certification. Peripheral nerve block (PNB) was preferred by 79% (111/141) of all diplomates, lumbosacral epidural (LE) by 21% (29/141), and peri-incisional infiltration (PI) by <1% (1/141). There was no association (p = .283) with specialty college. There was an association (p < .001) with time from board-certification with increased preference for LE when >10-years from certification and PI preferred by only those board-certified >20-years ago. There was an association with employment sector (p = .003) with more academic diplomates preferring LE. Anesthesiologists reported that treatment decisions were affected by various factors including time pressure and surgeon influence. CONCLUSION: Diplomates of ACVAA and ECVAA prefer PNB as the locoregional method of pelvic limb anesthesia in dogs undergoing TPLO. A greater percentage of newer and private practice diplomates prefer PNB while a larger percentage of senior and academic diplomates prefer LE. Decision making is multifactorial and includes perceived time pressure and surgeon influence. CLINICAL SIGNIFICANCE: Veterinary anesthesiologists prefer and frequently use PNB in dogs undergoing TPLO and surgeon influence may affect their chosen treatment.

Arterial blood gas tensions during recovery in horses anesthetized with apneustic anesthesia ventilation compared with conventional mechanical ventilation.

OBJECTIVE: To compare PaO2 and PaCO2 in horses recovering from general anesthesia maintained with either apneustic anesthesia ventilation (AAV) or conventional mechanical ventilation (CMV). STUDY DESIGN: Randomized, crossover design. ANIMALS: A total of 10 healthy adult horses from a university-owned herd. METHODS: Dorsally recumbent horses were anesthetized with isoflurane in oxygen [inspired oxygen fraction = 0.3 initially, with subsequent titration to maintain PaO2 ≥ 85 mmHg (11.3 kPa)] and ventilated with AAV or CMV according to predefined criteria [10 mL kg-1 tidal volume, PaCO2 40-45 mmHg (5.3-6.0 kPa) during CMV and < 60 mmHg (8.0 kPa) during AAV]. Horses were weaned from ventilation using a predefined protocol and transferred to a stall for unassisted recovery. Arterial blood samples were collected and analyzed at predefined time points. Tracheal oxygen insufflation at 15 L minute-1 was provided if PaO2 < 60 mmHg (8.0 kPa) on any analysis. Time to oxygen insufflation, first movement, sternal recumbency and standing were recorded. Data were analyzed using repeated measures anova, paired t tests and Fisher's exact test with significance defined as p < 0.05. RESULTS: Data from 10 horses were analyzed. Between modes, PaO2 was significantly higher immediately after weaning from ventilation and lower at sternal recumbency for AAV than for CMV. No PaCO2 differences were noted between ventilation modes. All horses ventilated with CMV required supplemental oxygen, whereas three horses ventilated with AAV did not. Time to first movement was shorter with AAV. Time to oxygen insufflation was not different between ventilation modes. CONCLUSIONS: Although horses ventilated with AAV entered the recovery period with higher PaO2, this advantage was not sustained during recovery. Whereas fewer horses required supplemental oxygen after AAV, the use of AAV does not preclude the need for routine supplemental oxygen administration in horses recovering from general anesthesia.

Comparison of four endotracheal tube cleaning protocols in anesthetized dogs.

OBJECTIVE: To compare the efficacy of 4 cleaning protocols applied to endotracheal tubes (ETTs) collected from anesthetized dogs. SAMPLE: 100 ETTs (25 per protocol). PROCEDURES: A 10-question survey designed to determine ETT reuse and cleaning practices was distributed via email to a sample of veterinary anesthesiologists. Informed by survey results, 4 ETT cleaning protocols were selected for use in a prospective clinical study. Dogs were intubated with sterile polyvinyl chloride ETTs. At extubation, each ETT was cultured for bacterial growth, randomly assigned to 1 of 4 protocols [water scrub (P1), detergent scrub (P2), detergent scrub and chlorhexidine gluconate (CHG) soak (P3), or detergent scrub and bleach soak (P4)], and cultured again after drying. Bacterial genera were identified using mass spectrometry and 16s rRNA sequencing. Proportions of ETTs exhibiting no post-cleaning growth were compared between protocols using the Fisher exact test with Bonferroni correction. RESULTS: Half of survey respondents that reused ETTs did not sterilize them before reuse, cleaning methods varied widely, and no reported methods were evidence-based. After use, the number of ETTs exhibiting no post-cleaning bacterial growth were 15/25 (60%), 14/25 (56%), 20/25 (80%), and 17/25 (68%) for protocols P1, P2, P3, and P4, respectively. Pairwise comparisons did not reveal any statistically significant differences between protocols. CLINICAL RELEVANCE: In small animal patients, some veterinary anesthesiologists reuse ETTs without sterilization and cleaning protocols vary widely. No differences between the studied protocols were identified. Further research is necessary to identify a safe, efficacious ETT cleaning protocol for use in small animal practice.

An implementation of apneustic anesthesia ventilation in the horse: comparison with conventional mechanical ventilation.

OBJECTIVE: To compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in dorsally recumbent anesthetized horses. STUDY DESIGN: Randomized, crossover design. ANIMALS: A total of 10 healthy adult horses from a university-owned herd. METHODS: Following xylazine, midazolam and ketamine administration, horses were orotracheally intubated and positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen [inspired oxygen fraction (FiO2) = 0.3 initially, with subsequent titration to maintain PaO2 ≥ 85 mmHg (11.3 kPa)]. Horses were instrumented and ventilated with AAV or CMV for 1 hour according to predefined criteria [10 mL kg-1 tidal volume (VT), PaCO2 of 40-45 mmHg (5.3-6.0 kPa) during CMV and <60 mmHg (8.0 kPa) during AAV]. Dobutamine was administered to maintain mean arterial pressure (MAP) >65 mmHg. Cardiopulmonary data were collected at baseline, 30 and 60 minutes. The effects of ventilation mode and time were analyzed using repeated-measures anova with significance defined as p < 0.05. RESULTS: Data from nine horses were analyzed. A significant effect of mode at one or more time points was found for respiratory rate, arterial and end-tidal CO2 tensions, arterial pH, mean airway pressure (Paw), respiratory system dynamic compliance index (CrsI), venous admixture (Q˙s/Q˙t), mean pulmonary artery pressure and systemic vascular resistance. No significant differences between modes were found for VT, FiO2, PaO2, arterial hemoglobin saturation, alveolar dead space, heart rate, MAP, cardiac index, stroke volume index, oxygen delivery index, oxygen extraction ratio and dobutamine administration. CONCLUSIONS AND CLINICAL RELEVANCE: In dorsally recumbent anesthetized horses, both ventilation modes supported adequate oxygenation with minimal supplemental oxygen. Compared with CMV, AAV resulted in higher CrsI and lower Q˙s/Q˙t. Despite higher mean Paw with AAV, the cardiovascular effects of each mode were not different. Further trials of AAV in anesthetized horses are warranted.

Risk Factors and Outcomes in Dogs With Respiratory Disease Undergoing Diagnostic Airway Lavage.

Advanced diagnostic testing is becoming increasingly important to accurately assess pulmonary parenchymal, airway, and pulmonary vascular diseases in dogs. Due to respiratory system compromise, diagnostic procedures performed under general anesthesia, including thoracic computed tomography (CT) and bronchoalveolar lavage (BAL), are thought to carry significant risk to dogs with respiratory disease. In lieu of performing these diagnostics, empirical medical therapy is often administered, potentially delaying appropriate therapy or providing unnecessary treatment. This study prospectively evaluated risk factors and outcomes for dogs with respiratory disease undergoing general anesthesia for thoracic CT and BAL. Arterial blood gas samples were taken pre- and post-BAL to evaluate pulmonary gas exchange. Pre-BAL arterial partial pressure of oxygen-to-fractional inspired oxygen ratio was used to stratify dogs into groups of mild or moderate to severe disease severity. A novel thoracic CT disease severity scoring system was used to independently stratify dogs into mild or moderate to severe groups. Statistical comparisons between groups were made for signalment, body weight, temperature, pulse, respiratory rate, WBC count, ventilator-acquired pulmonary mechanics (specific compliance and resistance), change in arterial partial pressure of oxygen post-BAL, and outcomes. Seventeen dogs were prospectively enrolled. A comparatively lower heart rate at presentation was the only potential marker of increased disease severity identified when stratified by CT severity score. Arterial partial pressure of oxygen did not significantly decrease post-BAL regardless of disease severity or stratification method. The CT scoring system significantly correlated with the pre-BAL arterial partial pressure of oxygen-to-fractional inspired oxygen ratio. Incidence of post-procedural complications was 18%, with all complications being transient. Mortality as a direct complication of diagnostics was 0%. When considering euthanasia secondary to severity of the underlying disease and poor prognosis or death due to unrelated disease, mortality was 18%. In dogs with respiratory disease undergoing advanced diagnostic procedures, the overall incidence of post-procedural morbidity was low with no mortality directly attributed to the procedures. A novel CT disease severity scoring system was utilized and shows promise as a tool for evaluation of disease severity in this patient population when compared to arterial blood gas analysis.

Effect of Midazolam on Vestibular Signs in Two Geriatric Dogs with Vestibular Disease.

An abrupt balance impairment, including leaning, falling, and rolling, occurred after IV administration of 0.2 mg/kg midazolam as a preanesthetic medication in two geriatric dogs with a history of nystagmus and head tilt. In the second case, leaning, falling, and rolling recurred after recovery from general anesthesia but gradually ceased after IV administration of 0.01 mg/kg flumazenil. These two cases suggest that the IV administration of midazolam was responsible for the balance impairment in dogs who were suspected to have idiopathic peripheral vestibular disease.

Use of computed tomography and radiation therapy planning software to develop a novel formula for body surface area calculation in dogs.

BACKGROUND: Body surface area (BSA) can reflect metabolic rate that might normalize dosing of chemotherapeutics across widely variable weights within a species. The current BSA formula for dogs lacks height, length, and body condition. HYPOTHESIS: Computed tomography (CT) imaging will allow inclusion of morphometric variables in allometric modeling of BSA in dogs resulting in an improved formula for BSA estimation. ANIMALS: Forty-eight dogs from 4 institutions with whole-body CT images. METHODS: Retrospective and prospective case series. Body surface area was contoured using whole-body CT scans and radiation therapy planning software. Body length and height were determined from CT images and also in 9 dogs by physical measurement. Nonlinear regression was used to model the BSA data sets using allometric equations. Goodness-of-fit criteria included average relative deviation, mean standard error, Akaike information criterion, and r2 (derived from the r-value generated by regression models). RESULTS: Contoured BSA differed from the current formula by -9% to +19%. Nonlinear regression on untransformed data yielded BSA = 0.0134 × body weight [kg]∧ 0.4746 × length (cm)∧ 0.6393 as the best-fit model. Heteroscedasticity (increasing morphometric variability with increasing BSA) was an important finding. CONCLUSIONS AND CLINICAL IMPORTANCE: Computed tomography-derived BSA was used to incorporate body length into a novel BSA formula. This formula can be applied prospectively to determine whether it correlates with adverse events attributed to chemotherapy.

Surgical Simulation: Markers of Proficiency.

OBJECTIVE: Surgical simulation has become an integral component of surgical training. Simulation proficiency determination has been traditionally based upon time to completion of various simulated tasks. We aimed to determine objective markers of proficiency in surgical simulation by comparing novel assessments with conventional evaluations of technical skill. DESIGN: Categorical general surgery residents completed 10 laparoscopic cholecystectomy modules using a high-fidelity simulator. We recorded and analyzed simulation task times, as well as number of hand movements, instrument path length, instrument acceleration, and participant affective engagement during each simulation. Comparisons were made to Objective Structured Assessment of Technical Skill (OSATS) and Accreditation Council for Graduate Medical Education Milestones, as well as previous laparoscopic experience, duration of laparoscopic cholecystectomies performed by participants, and postgraduate year. Comparisons were also made to Fundamentals of Laparoscopic Surgery task times. Spearman's rho was utilized for comparisons, significance set at >0.50. SETTING: University of Missouri, Columbia, Missouri, an academic tertiary care facility. PARTICIPANTS: Fourteen categorical general surgery residents (postgraduate year 1-5) were prospectively enrolled. RESULTS: One hundred forty simulations were included. The number of hand movements and instrument path lengths strongly correlated with simulation task times (ρ 0.62-0.87, p < 0.0001), FLS task completion times (ρ 0.50-0.53, p < 0.0001), and prior real-world laparoscopic cholecystectomy experience (ρ -0.51 to -0.53, p < 0.0001). No significant correlations were identified between any of the studied markers with Accreditation Council for Graduate Medical Education Milestones, Objective Structured Assessment of Technical Skill evaluations, total previous laparoscopic experience, or postgraduate year level. Neither instrument acceleration nor participant engagement showed significant correlation with any of the conventional markers of real-world or simulation skill proficiency. CONCLUSIONS: Simulation proficiency, measured by instrument and hand motion, is more representative of simulation skill than simulation task time, instrument acceleration, or participant engagement.

Case Difficulty, Postgraduate Year, and Resident Surgeon Stress: Effects on Operative Times.

OBJECTIVE: We aimed to evaluate resident operative times in relation to postgraduate year (PGY), case difficulty and resident stress while performing a single surgical procedure. DESIGN: We prospectively examined operative times for 268 laparoscopic cholecystectomies, and analyzed relationships between PGY, case difficulty, and resident surgeon stress utilizing electrodermal activity. Each case operative times were divided into 3 separate time periods. Case Start and End times were recorded, as well as the time between the start of the operation and the time until the cystic structures were divided (Division). Case difficulty was determined by multiple trained observers with a high inter-rater concordance. SETTING: University of Missouri, a tertiary academic medical institution. PARTICIPANTS: All categorical general surgery residents at our institution. RESULTS: For each operative time period examined during laparoscopic cholecystectomy, operative time increased, with each incremental increase in difficulty resulting in approximately 130% longer times. Minimal differences in operative times were seen between PGY levels, except during the easiest cases (Start-End times: 38.5 ± 10.4 minutes vs 34.2 ± 10.8 minutes vs 28.9 ± 10.9 minutes, p 0.002). Resident stress poorly correlated with operative times regardless of case difficulty (Pearson coefficient range 0.0-0.22). CONCLUSIONS: Operative times are longer with increasing case difficulty. PGY level and resident surgeon stress appear to have minimal to no correlation with operative times, regardless of case difficulty.

Anesthesia modifies subthreshold critical slowing down in a stochastic Hodgkin-Huxley-like model with inhibitory synaptic input.

The dynamics of a stochastic type-I Hodgkin-Huxley-like point neuron model exposed to inhibitory synaptic noise are investigated as a function of distance from spiking threshold and the inhibitory influence of the general anesthetic agent propofol. The model is biologically motivated and includes the effects of intrinsic ion-channel noise via a stochastic differential equation description as well as inhibitory synaptic noise modeled as multiple Poisson-distributed impulse trains with saturating response functions. The effect of propofol on these synapses is incorporated through this drug's principal influence on fast inhibitory neurotransmission mediated by γ-aminobutyric acid (GABA) type-A receptors via reduction of the synaptic response decay rate. As the neuron model approaches spiking threshold from below, we track membrane voltage fluctuation statistics of numerically simulated stochastic trajectories. We find that for a given distance from spiking threshold, increasing the magnitude of anesthetic-induced inhibition is associated with augmented signatures of critical slowing: fluctuation amplitudes and correlation times grow as spectral power is increasingly focused at 0 Hz. Furthermore, as a function of distance from threshold, anesthesia significantly modifies the power-law exponents for variance and correlation time divergences observable in stochastic trajectories. Compared to the inverse square root power-law scaling of these quantities anticipated for the saddle-node bifurcation of type-I neurons in the absence of anesthesia, increasing anesthetic-induced inhibition results in an observable exponent <-0.5 for variance and >-0.5 for correlation time divergences. However, these behaviors eventually break down as distance from threshold goes to zero with both the variance and correlation time converging to common values independent of anesthesia. Compared to the case of no synaptic input, linearization of an approximating multivariate Ornstein-Uhlenbeck model reveals these effects to be the consequence of an additional slow eigenvalue associated with synaptic activity that competes with those of the underlying point neuron in a manner that depends on distance from spiking threshold.

Perceptions of Simulator- and Live Tissue-Based Combat Casualty Care Training of Senior Special Operations Medics.

The relative effectiveness of live tissue (LT)- and inanimate simulation (SIM)-based training of combat medics is the subject of intense debate. A structured interview was utilized to determine the training modality preferences and the perceived value of LT- and SIM-based combat casualty care training of 25 senior special operations medics. Participant demographics and training experience, Likert scale-based assessment of training modality value, selection of preferred training modality for 11 combat casualty care procedures, and 12 open-ended questions probing opinions of the limitations and benefits of LT- and SIM-based training were collected from this convenience sample. All participants indicated significant combat medic experience and training. Of the 11 procedures questioned, LT was identified as superior for seven with mixed responses for the remaining four. LT was consistently identified as an essential training modality with tactile sensation and the physiologic responses of animal models to injury and therapy as primary benefits. Across procedures, 100% of participants felt that LT should be used in combat casualty care training and 96% felt that SIM should also be utilized. Repeatability and accuracy of size/weight were identified as key benefits of SIM training. Respondents reported that capability, self-confidence, success, and resilience of the combat medic all benefitted from LT training. The overriding theme was the general superiority of LT with recognition of the unique and complementary benefits of SIM.

Surgical resident technical skill self-evaluation: increased precision with training progression.

BACKGROUND: Surgical resident ability to accurately evaluate one's own skill level is an important part of educational growth. We aimed to determine if differences exist between self and observer technical skill evaluation of surgical residents performing a single procedure. MATERIALS AND METHODS: We prospectively enrolled 14 categorical general surgery residents (six post-graduate year [PGY] 1-2, three PGY 3, and five PGY 4-5). Over a 6-month period, following each laparoscopic cholecystectomy, residents and seven faculty each completed the Objective Structured Assessment of Technical Skills (OSATS). Spearman's coefficient was calculated for three groups: senior (PGY 4-5), PGY3, and junior (PGY 1-2). Rho (ρ) values greater than 0.8 were considered well correlated. RESULTS: Of the 125 paired assessments (resident-faculty each evaluating the same case), 58 were completed for senior residents, 54 for PGY3 residents, and 13 for junior residents. Using the mean from all OSATS categories, trainee self-evaluations correlated well to faculty (senior ρ 0.97, PGY3 ρ 0.9, junior ρ 0.9). When specific OSATS categories were analyzed, junior residents exhibited poor correlation in categories of respect for tissue (ρ -0.5), instrument handling (ρ 0.71), operative flow (ρ 0.41), use of assistants (ρ 0.05), procedural knowledge (ρ 0.32), and overall comfort with the procedure (ρ 0.73). PGY3 residents lacked correlation in two OSATS categories, operative flow (ρ 0.7) and procedural knowledge (ρ 0.2). Senior resident self-evaluations exhibited strong correlations to observers in all areas. CONCLUSIONS: Surgical residents improve technical skill self-awareness with progressive training. Less-experienced trainees have a tendency to over-or-underestimate technical skill.

Objective Measurement of Clinical Competency in Surgical Education Using Electrodermal Activity.

OBJECTIVE: Within the realm of surgical education, there is a need for objective means to determine surgical competence and resident readiness to operate independently. We propose a novel, objective method of assessing resident confidence and clinical competence based on measurement of electrodermal activity (EDA) during live surgical procedures. We hypothesized that with progressive training, EDA responses to the stress of performing surgery would exhibit decline, elucidating an objective correlate of clinical competence. DESIGN: EDA was measured using galvanic skin response sensors worn by residents performing laparoscopic cholecystectomy on sequential live human patients over an 8-month period. Baseline, phasic (peak) and tonic EDA responses were measured as a fractional change from baseline. SETTING: University of Missouri, Columbia, Missouri, an academic tertiary care facility. PARTICIPANTS: Fourteen categorical general surgery residents and 5 faculty surgeons were voluntarily enrolled and participated through completion. RESULTS: Tonic fractional change (FCTONIC) was highest in PGY3 residents compared with postgraduate year (PGY) 1 and 2 residents (7.199 vs. 2.100, p = 0.004, 95% CI: 8.58-1.61 and PGY4 and 5 residents (7.199 vs. 2.079, p = 0.002, 95% CI: 8.38-0.29). Phasic fractional change in EDA (FCPHASIC) exhibited a progressive decline across resident training levels, with PGY1 and 2 residents having the highest response, and faculty displaying the lowest FCPHASIC responses. Statistical differences were seen between FCPHASIC faculty and PGY4 and 5 (3.596 vs. 6.180, p = 0.004, 95% CI: 0.80-4.36), PGY4 and 5, and PGY3 (6.180 vs. 15.998, p = 0.003, 95% CI: 3.33-16.3), as well as among all residents and faculty (13.057 vs. 3.596, p = 0.004, 95% CI: 15.8-3.1). CONCLUSION: Phasic EDA changes decrease with increasing clinical competence. For those participants with the lowest and highest levels of competence, tonic EDA changes are minimal. Tonic EDA changes follow an inverse-U shape with differing levels of clinical competence.

Live tissue versus simulation training for emergency procedures: Is simulation ready to replace live tissue?

BACKGROUND: Training of emergency procedures is challenging and application is not routine in all health care settings. The debate over simulation as an alternative to live tissue training continues with legislation before Congress to banish live tissue training in the Department of Defense. Little evidence exists to objectify best practice. We sought to evaluate live tissue and simulation-based training practices in 12 life-saving emergency procedures. METHODS: In the study, 742 subjects were randomized to live tissue or simulation-training. Assessments of self-efficacy, cognitive knowledge, and psychomotor performance were completed pre- and post-training. Affective response to training was assessed through electrodermal activity. Subject matter experts gap analysis of live tissue versus simulation completed the data set. RESULTS: Subjects demonstrated pre- to post-training gains in self-efficacy, cognitive knowledge, psychomotor performance, and affective response regardless of training modality (P < .01 each). With the exception of fluid resuscitation in the psychomotor performance domain, no statistically significant differences were observed based on training modality in the overall group. Risk estimates on the least pretest performance subgroup favored simulation in 7 procedures. Affective response was greatest in live tissue training (P < .01) and varied by species and model. Subject matter experts noted significant value in live tissue in 7 procedures. Gap analysis noted shortcomings in all models and synergy between models. CONCLUSION: Although simulation has made significant gains, no single modality can be identified definitively as superior. Wholesale abandonment of live tissue training is not warranted. We maintain that combined live tissue and simulation-based training add value and should be continued. Congressional mandates may accelerate simulation development and improve performance.

Recognition and Treatment of Nerve Agent Casualties: Evidence of Reduced Learner Engagement During Video-based Training.

Changes in electrodermal activity (EDA) correlate with arousal and stress during stimulating experiences. We hypothesized that associations exist between short-term performance gains and changes in EDA. A total of 187 combat medics were randomly assigned to simulation (S), live tissue (L), or video (V) based training in the recognition and treatment of nerve agent casualties. Change in EDA from baseline to training was quantified for tonic and phasic responses and was categorized as positive (>+10%), no change (±10%), or negative (<-10%). Cognitive and psychomotor skills assessments were applied before and after the baseline/training period to quantify short-term performance changes. Statistically significant differences in both EDA arousal measures between training modalities (p < 0.001 with L > S ∼ V) were observed. Notably, larger proportions of trainees experienced negative changes in tonic (67%) and phasic (21%) EDA measures in the V group when compared to the L and S groups. Regardless of training modality, negative tonic and phasic EDA responses were associated with lower psychomotor performance gains and this finding approached statistical significance (tonic: p = 0.056, phasic: p = 0.08). No significant differences were noted in pre- to post-training cognitive performance between EDA response categories. As quantified by EDA response to training, reduced arousal was associated with lower short-term psychomotor, but not cognitive, performance gains.

Comparison of Short-Term Postoperative Analgesia by Epidural, Femoral Nerve Block, or Combination Femoral and Sciatic Nerve Block in Dogs Undergoing Tibial Plateau Leveling Osteotomy.

OBJECTIVE: To compare early postoperative analgesia in dogs undergoing unilateral tibial plateau leveling osteotomy (TPLO) that received bupivacaine via preoperative femoral nerve block (FNB), combination femoral-sciatic nerve block (F+SNB), or lumbosacral epidural (EPI). STUDY DESIGN: Randomized, blinded, prospective clinical trial. ANIMALS: Forty-five client-owned dogs undergoing unilateral TPLO. METHODS: Dogs undergoing unilateral TPLO were enrolled and randomly allocated to 1 of 3 treatments: FNB, F+SNB, or EPI. Assessments were completed by an observer blinded to treatment at 0, 1, 2, 4, 6, and 8 hours after extubation using the Glasgow Composite Pain Score-Short Form (GCPS-SF). Dogs with a total score ≥ 6 or ≥ 3 in any category were given a rescue analgesic. Outcome measures analyzed for differences across treatments were the GCPS-SF at each time point, time to first rescue analgesic, and total number of rescue analgesic doses per dog. RESULTS: The GCPS-SF score at extubation was significantly higher for FNB (median 3) compared to F+SNB (median 2). A significantly higher proportion of dogs receiving FNB (4/14) than F+SNB (0/17) required rescue analgesic at extubation. There was no significant difference in the proportion of dogs requiring rescue at extubation between FNB and EPI (2/14) or between F+SNB and EPI. There was no significant difference in the median time to first rescue between FNB (0 hours) and F+SNB (2 hours) or between F+SNB and EPI (1.5 hours). CONCLUSION: In dogs undergoing unilateral TPLO, bupivacaine administered via FNB, alone or in combination with sciatic nerve block, can provide short-term postoperative analgesia not different to that with administration via lumbosacral epidural.

Channel-noise-induced critical slowing in the subthreshold Hodgkin-Huxley neuron.

The dynamics of a spiking neuron approaching threshold is investigated in the framework of Markov-chain models describing the random state-transitions of the underlying ion-channel proteins. We characterize subthreshold channel-noise-induced transmembrane potential fluctuations in both type-I (integrator) and type-II (resonator) parametrizations of the classic conductance-based Hodgkin-Huxley equations. As each neuron approaches spiking threshold from below, numerical simulations of stochastic trajectories demonstrate pronounced growth in amplitude simultaneous with decay in frequency of membrane voltage fluctuations induced by ion-channel state transitions. To explore this progression of fluctuation statistics, we approximate the exact Markov treatment with a 12-variable channel-based stochastic differential equation (SDE) and its Ornstein-Uhlenbeck (OU) linearization and show excellent agreement between Markov and SDE numerical simulations. Predictions of the OU theory with respect to membrane potential fluctuation variance, autocorrelation, correlation time, and spectral density are also in agreement and illustrate the close connection between the eigenvalue structure of the associated deterministic bifurcations and the observed behavior of the noisy Markov traces on close approach to threshold for both integrator and resonator point-neuron varieties.