G. Alec Rooke

Evaluation of anesthesia residents using mannequin-based simulation: a multiinstitutional study.

Background Anesthesia simulators can generate reproducible, standardized clinical scenarios for instruction and evaluation purposes. Valid and reliable simulated scenarios and grading systems must be developed to use simulation for evaluation of anesthesia residents. Methods After obtaining Human Subjects approval at each of the 10 participating institutions, 99 anesthesia residents consented to be videotaped during their management of four simulated scenarios on MedSim or METI mannequin-based anesthesia simulators. Using two different grading forms, two evaluators at each department independently reviewed the videotapes of the subjects from their institution to score the residents’ performance. A third evaluator, at an outside institution, reviewed the videotape again. Statistical analysis was performed for construct- and criterion-related validity, internal consistency, interrater reliability, and intersimulator reliability. A single evaluator reviewed all videotapes a fourth time to determine the frequency of certain management errors. Results Even advanced anesthesia residents nearing completion of their training made numerous management errors; however, construct-related validity of mannequin-based simulator assessment was supported by an overall improvement in simulator scores from CB and CA-1 to CA-2 and CA-3 levels of training. Subjects rated the simulator scenarios as realistic (3.47 out of possible 4), further supporting construct-related validity. Criterion-related validity was supported by moderate correlation of simulator scores with departmental faculty evaluations (0.37–0.41, P < 0.01), ABA written in-training scores (0.44–0.49, P < 0.01), and departmental mock oral board scores (0.44–0.47, P < 0.01). Reliability of the simulator assessment was demonstrated by very good internal consistency (&agr; = 0.71–0.76) and excellent interrater reliability (correlation = 0.94–0.96;P < 0.01; &kgr; = 0.81–0.90). There was no significant difference in METI versus MedSim scores for residents in the same year of training. Conclusions Numerous management errors were identified in this study of anesthesia residents from 10 institutions. Further attention to these problems may benefit residency training since advanced residents continued to make these errors. Evaluation of anesthesia residents using mannequin-based simulators shows promise, adding a new dimension to current assessment methods. Further improvements are necessary in the simulation scenarios and grading criteria before mannequin-based simulation is used for accreditation purposes.

The effect of isoflurane, halothane, sevoflurane, and thiopental/nitrous oxide on respiratory system resistance after tracheal intubation

Background: After tracheal intubation, lung resistance and therefore respiratory system resistance (Rrs) routinely increase, sometimes to the point of clinical bronchospasm. Volatile anesthetics generally have been considered to be effective bronchodilators, although there are few human data comparing the efficacy of available agents. This study compared the bronchodilating efficacy of four anesthetic maintenance regimens: 1.1 minimum alveolar concentration (MAC) end‐tidal sevoflurane, isoflurane or halothane, and thiopental/nitrous oxide. Methods: Sixty‐six patients underwent tracheal intubation after administration of 2 micro gram/kg fentanyl, 5 mg/kg thiopental, and 1 mg/kg succinylcholine. Vecuronium or pancuronium (0.1 mg/kg) was then given to ensure paralysis during the rest of the study. Postintubation R sub rs was measured using the isovolume technique. Maintenance anesthesia was then randomized to thiopental 0.25 mg [center dot] kg sup ‐1 [center dot] min sup ‐1 plus 50% nitrous oxide, or 1.1 MAC end‐tidal isoflurane, halothane, or sevoflurane. The Rrs was measured after 5 and 10 min of maintenance anesthesia. Data were expressed as means +/‐ SD. Results: Maintenance with thiopental/nitrous oxide failed to decrease Rrs, whereas all three volatile anesthetics significantly decreased Rrs at 5 min with little further improvement at 10 min. Sevoflurane decreased Rrs more than either halothane or isoflurane (P < 0.05; 58 +/‐ 14% of the postintubation Rrs vs. 69 +/‐ 20% and 75 +/‐ 13%, respectively). Conclusions: After tracheal intubation in persons without asthma, sevoflurane decreased Rrs as much or more than isoflurane or halothane did during a 10‐min exposure at 1.1 MAC.

Comparison of the Effects of Etomidate, Propofol, and Thiopental on Respiratory Resistance after Tracheal Intubation

Background Tracheal intubation frequently results in reversible bronchoconstriction. Propofol has been reported to minimize this response in healthy patients and in asthma patients, but may be unsuitable for hemodynamically unstable patients for whom etomidate may be preferable. The current study examined respiratory resistance after tracheal intubation after induction with either thiopental, etomidate, or propofol. A supratherapeutic dose of etomidate was used to test the hypothesis that the bronchoconstrictive response could be minimized by deep intravenous anesthesia. Methods Seventy‐seven studies were conducted in 75 patients. Anesthesia was induced with either 2.5 mg/kg propofol, 0.4 mg/kg etomidate, or 5 mg/kg thiopental. Respiratory resistance was measured at 2 min after induction. Results Respiratory resistance at 2 min was 8.1+/‐3.4 cmH sub 2 O *symbol* l sup ‐1 *symbol* s (mean+/‐SD) for patients receiving propofol versus 11.3+/‐5.3 for patients receiving etomidate and 12.3+/‐7.9 for patients receiving thiopental (P less than or equal to 0.05 for propofol vs. either etomidate or thiopental). Conclusions Respiratory resistance after tracheal intubation is lower after induction with propofol than after induction with thiopental or after induction with high‐dose etomidate.

Screen-Based Anesthesia Simulation With Debriefing Improves Performance in a Mannequin-Based Anesthesia Simulator

Background: Previous investigations have established the need for improved training for management of anesthetic emergencies. Training with inexpensive screen-based anesthesia simulators may prove to be helpful. Purposes: We measured the effectiveness of screen-based simulator training with debriefing on the response to simulated anesthetic critical incidents. Methods: Thirty-one 1st-year clinical anesthesia residents were randomized into 2 groups. The intervention group handled 10 anesthetic emergencies using the screen-based anesthesia simulator program and received written feedback on their management, whereas the traditional (control) group was asked to study a handout covering the same 10 emergencies. All residents then were evaluated on their management of 4 standardized scenarios in a mannequin-based simulator using a quantitative scoring system. Results: The average point score for the simulator-with-debriefing group was 52.6 +/- 9.9 out of 95 possible points. The traditional group average point score was 43.4 +/- 5.9, p =. 004. Conclusions: Residents who managed anesthetic problems using a screen-based anesthesia simulator handled the emergencies in a mannequin-based anesthesia simulator better than residents who were asked to study a handout covering the same problems. Computer simulations with feedback are effective as a supplement to traditional residency training methods for the management of medical emergencies.

Hemodynamic response and change in organ blood volume during spinal anesthesia in elderly men with cardiac disease

Aging and disease may make the elderly patient with cardiac disease particularly susceptible to hypotension during spinal anesthesia.We studied 15 men, 59-80 y old, with histories of prior myocardial infarction (n = 9), congestive heart failure (n = 2), and/or stable myocardial ischemia (n = 11) given spinal anesthesia with 50 mg lidocaine in dextrose. Technetium-99m-labeled red blood cell imaging estimated left ventricular ejection fraction (EF) and changes in blood volume in the abdominal organs and legs. Arterial and pulmonary artery catheters provided hemodynamic measurements. Sensory block averaged T4 (range T1-10). Mean arterial pressure decreased 33% +/- 15% (SD) (P < 0.001), secondary to decreases in vascular resistance (SVR), -26% +/- 13% (P < 0.001) and cardiac output, -10% +/- 16% (P = 0.03). EF increased from 53% +/- 11% to 58% +/- 14% (P < 0.001) while left ventricular end-diastolic volume (LVEDV) decreased (-19% +/- 9%, P < 0.001). Blood volume increased in the legs (6% +/- 6%, P = 0.006), kidneys (10% +/- 9%, P < 0.001), and mesentery (7% +/- 5%, P 0.001) but not in the liver or spleen. Cardiac function was well maintained. We concluded that the primary mechanism of hypotension was a decrease in SVR, not cardiac output, despite the decrease in LVEDV. (Anesth Analg 1997;85:99-105)

Priorities in perioperative geriatrics.

T he aging of the baby-boom population and the decreases in adult mortality seen in the last few decades will dramatically increase the age of Americans between 2010 and 2030. During that time, the population older than age 65 yr is expected to grow by 75%, whereas between 1995 and 2050, the cumulative growth of the population older than 85 yr is expected to exceed 400% (1). Furthermore, it has been reported that the increased demand for surgery in this population may exceed the rate of population growth (2). The implications of an aging population for the practice of anesthesiology are profound. Age-related changes in physiology and pharmacology can affect every aspect of perioperative care. The changes in surgical demographics will compel the anesthesiologist to become familiar with the physiology and clinical care of the aged. This review will serve as an introduction. First, some of the physiologic changes that occur with aging will be presented. Second, the preoperative assessment of the older surgical patient will be discussed. Third, some of the research related to intraoperative management of the geriatric surgical patient will be described. In the fourth section, we will discuss some geriatric-specific issues related to postoperative management.

Long-duration low-flow sevoflurane and isoflurane effects on postoperative renal and hepatic function

Sevoflurane degradation by carbon dioxide absorbents during low-flow anesthesia forms the haloalkene Compound A, which causes nephrotoxicity in rats. Numerous studies have shown no effects of Compound A formation on postoperative renal function after moderate-duration (3–4 h) low-flow sevoflurane; however, effects of longer exposures remain unresolved. We compared renal function after long-duration low-flow (<1 L/min) sevoflurane and isoflurane anesthesia in consenting surgical patients with normal renal function. To maximize degradant exposure, Baralyme® was used, and anesthetic concentrations were maximized (no nitrous oxide and minimal opioids). Inspired and expired Compound A concentrations were quantified. Blood and urine were obtained for laboratory evaluation. Sevoflurane (n = 28) and isoflurane (n = 27) groups were similar with respect to age, sex, weight, ASA status, and anesthetic duration (9.1 ± 3.0 and 8.2 ± 3.0 h, mean ± sd) and exposure (9.2 ± 3.6 and 9.1 ± 3.7 minimum alveolar anesthetic concentration hours). Maximum inspired Compound A was 25 ± 9 ppm (range, 6–49 ppm), and exposure (area under the concentration-time curve) was 165 ± 95 (35–428) ppm · h. There was no significant difference between anesthetic groups in 24- or 72-h serum creatinine, blood urea nitrogen, creatinine clearance, or 0- to 24-h or 48- to 72-h urinary protein or glucose excretion. Proteinuria and glucosuria were common in both groups. There was no correlation between Compound A exposure and any renal function measure. There was no difference between anesthetic groups in 24- or 72-h aspartate aminotransferase or alanine aminotransferase. These results show that the renal and hepatic effects of long-duration low-flow sevoflurane and isoflurane were similar. No evidence for low-flow sevoflurane nephrotoxicity was observed, even at high Compound A exposures as long as 17 h. Proteinuria and glucosuria were common and nonspecific postoperative findings. Long-duration low-flow sevoflurane seems as safe as long-duration low-flow isoflurane anesthesia.

Low-flow sevoflurane compared with low-flow isoflurane anesthesia in patients with stable renal insufficiency.

BACKGROUND Sevoflurane is degraded to compound A (CpA) by carbon dioxide absorbents containing strong base. CpA is nephrotoxic in rats. Patient exposure to CpA is increased with low fresh gas flow rates, use of Baralyme, and high sevoflurane concentrations. CpA formation during low-flow and closed circuit sevoflurane anesthesia had no significant renal effects in surgical patients with normal renal function. Preexisting renal insufficiency is a risk factor for postoperative renal dysfunction. Although preexisting renal insufficiency is not affected by high-flow sevoflurane, the effect of low-flow sevoflurane in patients with renal insufficiency is unknown. METHODS After obtaining institutional review board approval, 116 patients with a stable preoperative serum creatinine concentration 1.5 mg/dl or greater were assessable. Patients were randomized to receive either sevoflurane (n = 59, 0.8-2.5 vol%) or isoflurane (n = 57, 0.5-1.4 vol%) at a fresh gas flow rate of 1 l/min or less. Use of opioids was restricted to a minimum, and Baralyme was used to increase CpA exposure. Inspiratory and expiratory CpA concentrations were measured during anesthesia. Renal function (serum creatinine and blood urea nitrogen, urine protein and glucose, creatinine clearance) was measured preoperatively and 24 and 72 h after induction. RESULTS Demographic patient data did not differ between groups. Patients received 3.1 +/- 2.4 minimum alveolar concentration-hours sevoflurane or 3.8 +/- 2.6 minimum alveolar concentration-hours isoflurane (mean +/- SD). Durations of low flow were 201.3 +/- 98.0 and 213.6 +/- 83.4 min, respectively. Maximum inspiratory CpA with sevoflurane was 18.9 +/- 7.6 ppm (mean +/- SD), resulting in an average total CpA exposure of 44.0 +/- 30.6 ppm/h. There were no statistically significant changes from baseline to 24- and 72-h values for serum creatinine or blood urea nitrogen, creatinine clearance, urine protein, and glucose, nor were there significant differences between both anesthetics. CONCLUSION There were no statistically significant differences in measured parameters of renal function after low-flow sevoflurane anesthesia compared with isoflurane. These results suggest that low-flow sevoflurane anesthesia is as safe as low-flow isoflurane and does not alter kidney function in patients with preexisting renal disease.

Pathomechanisms and complications related to patient positioning and anesthesia during shoulder arthroscopy.

The lateral decubitus and beach-chair positions each offer unique benefits to the shoulder surgeon with respect to visualization, efficiency, and ease during arthroscopic shoulder procedures. The purpose of this article was to comprehensively review the reports and studies documenting independent and dependent complications related to patient positioning and anesthesia during arthroscopic shoulder surgery. The lateral decubitus position has been associated with the potential for peripheral neurapraxia, brachial plexopathy, direct nerve injury, and airway compromise. The beach-chair position has been associated with cervical neurapraxia, pneumothorax, and the potential for end-organ hypoperfusion injuries (when deliberate hypotension is used). Potentially concerning are hypotensive bradycardic events, which may be relatively common in association with the use of epinephrine-containing interscalene anesthetics in beach chair-positioned patients. Irrigant complications (fluid spread, ventricular tachycardia) are avoidable risks not unique to either specific position. Although minor transient anesthetic- and position-related complications (neurapraxia, hypotension) may occur in as many 10% to 30% of patients, major complications such as end-organ damage or permanent impairments are exceedingly rare. Regardless of position, complications are almost uniformly avoidable if surgeon and anesthetist exercise care and prudent attention to position and anesthetic choices. The purpose of this article is to review the potential for position- and anesthesia-related complications and acquaint the shoulder surgeon with the proposed pathophysiologic mechanisms that can lead to them.

Effect of Prophylactic Bronchodilator Treatment on Lung Resistance after Tracheal Intubation

BackgroundAfter Induction of anesthesia, lung resistance increases. We hypothesized that prophylactic bronchodilator treatment before tracheal intubation would result in a lower lung resistance after placement of the endotracheal tube. MethodsForty-two adult patients were randomized to receive one of three inhaled medications 1 h before surgery. All patients first underwent pulmonary function tests. Patients then received either inhaled albuterol (360 μg) (n = 12), Inhaled ipratroplum bromide (72 μg) (n = 15) or a placebo Inhalation (n = 15). Two, 5, and 15 min after tracheal intubation, lung resistance was measured using the method of von Neergard and Wirtz. ResultsPatients who received either bronchodilator had significantly lower lung resistance after intubation than those receiving placebo. At 2 min, lung resistances were 12.7 ± 1.4 cmH2O·1-1·s-1 (mean ± SEM) for the placebo group, 6.4 ± 3.1 cmH2O·1-1·s-1 for the ipratropium-treated group (P < 0.05 vs. placebo), and 7.2 + 0.8 cmH2O·1-1·s-1 for the albuterol-treated group (P < 0.05 vs. placebo). The differences in lung resistance persisted through the final measurement at 15 min. Three of fifteen placebo-treated patients developed audible wheezing whereas no patients developed wheezing In either bronchodilator-treated group (P < 0.05 by Fishers exact test). Although smokers and nonsmokers in the placebo group developed similar resistances after intubation, bronchodilator treatment resulted in lower resistance in nonsmokers than in smokers (P < 0.05). ConclusionsProphylactic treatment with either an inhaled β2-adrenergic agonist or an inhaled cholinergic antagonist produced lower lung resistance after intubation when compared with an inhaled placebo medication. The effect was more pronounced in nonsmokers than in smokers.