The Use of Standardized Patients to Evaluate Interpersonal and Communication Skills of Anesthesiology Residents: A Pilot Study.

OBJECTIVE: The study was conducted to explore the feasibility and validity of using standardized patients (SPs) in assessing the interpersonal and communication skills (ICS) of anesthesiology residents. METHODS: A cross-sectional study was conducted to assess the ICS of anesthesiology residents using SPs. Each resident participated in two staged encounters and was graded by the SPs using a modified SEGUE framework. Each encounter was videotaped and reviewed independently by two senior faculty members using the same checklist. RESULTS: The ICS scores improved with advancement of training. This was confirmed by both SP and faculty (CA-1, 47.8 ± 9.8 and CA-3, 64.8 ± 1.9, P=0.022) assessments. There was strong inter-faculty agreement for individual residents (r=0.95, P<0.001). In-training exam (ITE) scores appeared to correlate with the faculty ICS score (r=0.61, p<0.05). CONCLUSION: Standardized patient encounters using a modified SEGUE framework may be a useful tool to assess ICS among anesthesiology residents. Resident performance improves even in the absence of interventions to teach ICS. The improvement appears to correlate with increasing experience and knowledge.

Simulation of the reversal of neuromuscular block by sequestration of the free molecules of the muscle relaxant.

The study examined in simulations the interaction between a muscle relaxant and an antagonist that binds the free molecules of the relaxant, as experimentally demonstrated for rocuronium and sugammadex. The hypothetical muscle relaxant D and the hypothetical antagonist X were assigned pharmacokinetic properties to define the time course of their concentrations in plasma, and pharmacodynamic properties to define binding of D to either X or the receptors at the motor end plates. D, X, and their complex DX were postulated to diffuse between plasma and the effect compartment. The first and the fourth twitch elicited in sequential trains of four stimuli were evaluated in a model of neuromuscular transmission. The rates of reactions were formulated as differential equations and the equations solved numerically. If the affinity of D for X is comparable to that of D for the postsynaptic receptors, doses of X two to four times larger than the dose of D produce a fast and a complete recovery of the twitches. Smaller doses of X or lower affinities of D for X accomplish a slower and only partial recovery. Additionally, the complete restoration of twitch strength within 2 min after the injection of X requires that X and DX diffuse into the effect compartment. The simulations reveal the physicochemical, pharmacokinetic, and pharmacodynamic properties of an antagonist that restores twitch strength by sequestering the free molecules of the muscle relaxant.

The relationship between twitch depression and twitch fade during neuromuscular block produced by vecuronium: correlation with the release of acetylcholine.

BACKGROUND: Train-of-four stimulation pattern following the administration of non-depolarizing neuromuscular blocking drugs reveals fade on successive contractions. Fade is caused by the release of fewer acetylcholine molecules by the fourth (A4) than by the first stimulus (A1). The current study was conducted to define the relationship between the clinically observed fade and the simulated decline in acetylcholine release (A4/A1) that would be necessary to produce it. METHODS: The T4/T1 ratios produced by different doses of vecuronium (15-80 microg x kg-1) were plotted as a function of the concomitant T1. Separately in a model of neuromuscular transmission, T1, T4, and T4/T1 were estimated using simulations in the presence and in the absence of a neuromuscular blocking drug and a stepwise decrease in A4, but constant A1. RESULTS: Vecuronium induced neuromuscular block was associated with larger T4/T1 ratios (less fade) during the onset than during the offset of the block. All doses caused similar fade during offset. Simulations revealed that the smallest T4/T1 was associated with the nadir of A4/A1 and occurred at the beginning of T1 recovery. The nadir of A4/A1 was only marginally affected by the dose of vecuronium: 15 microg x kg-1 producing the minimum A4/A1 of 0.8 and 80 microg x kg-1 the minimum A4/A1 of 0.7. CONCLUSION: The hysteresis in the fade between onset and offset appears to be caused by a delayed decrease of A4/A1 as compared with the decrease in T1. Tentative estimates of the decrease in A4/A1 during fade produced by vecuronium are offered. However, the validity of these estimates is dependent on the validity of the assumptions made in simulations.

Modeling of twitch fade based on slow interaction of nondepolarizing muscle relaxants with the presynaptic receptors.

Nondepolarizing muscle relaxants (MRs) diminish the indirectly evoked single twitch due to their binding to the postsynaptic receptors. Additionally, the MRs produce progressive diminution of successive twitches upon repetitive stimulation (fade). Our study addresses the generation of fade as observed under clinical situation. The study was conducted in two phases. In the clinical part, we have evaluated the time course of twitch depression and fade following the administration of several doses of three MRs (rocuronium, pancuronium, and cisatracurium). In the second part, we have modified our model of neuromuscular transmission to simulate the time course of twitch depression and fade. The MR was assumed to bind to a single site on the presynaptic receptor to produce fade. The rates of interaction with the presynaptic receptors were characterized in terms of the arbitrarily assigned equilibrium dissociation constant and the half-life for dissociation of the presynaptic complex. A method was developed to relate the release of acetylcholine to the occupancy of the presynaptic receptors. The strength of the first and the fourth twitch was calculated from the peak concentration of the activated postsynaptic receptors, i.e., of those receptors with both sites occupied by acetylcholine. Our results indicate that, while the affinity of the MR for the presynaptic receptor plays little role in the time course of fade, the rate of dissociation of the complex between the presynaptic receptors and the muscle relaxant may be critical in determining the time course of fade. Tentative estimates of this parameter are offered.

Intraoperative identification of both a paradoxical embolism and its probable etiologic site.

We report a case of upper extremity arterial ischemia in a 41-year-old man. Intraoperative transesophageal echocardiography identified a paradoxical embolization that traversed a patent foramen ovale as the probable etiology. The diagnosis of paradoxical embolism with intraoperative identification of the etiologic site of the deep venous thrombosis is a rare event. This case presents the use of transesophageal echocardiography beyond its monitoring function in helping diagnose the cause of arterial ischemia.

Volume of the effect compartment in simulations of neuromuscular block.

BACKGROUND: The study examines the role of the volume of the effect compartment in simulations of neuromuscular block (NMB) produced by nondepolarizing muscle relaxants. METHODS: The molar amount of the postsynaptic receptors at the motor end plates in muscle was assumed constant; the apparent receptor concentration in the effect compartment is the ratio of this amount and the volume arbitrarily assigned to the effect compartment. The muscle relaxants were postulated to diffuse between the central and the effect compartment and to bind to the postsynaptic receptors. NMB was calculated from the free concentration of the muscle relaxant in the effect compartment. RESULTS: The simulations suggest that the time profiles of NMB and the derived pharmacokinetic and pharmacodynamic variables are dependent on the apparent receptor concentration in the effect compartment. For small, but not for large, volumes, times to peak submaximal NMB are projected to depend on the magnitude of NMB and on the binding affinities. CONCLUSION: An experimental design to estimate the volume of the effect compartment is suggested.