Frank Herbstreit

Impaired upper airway integrity by residual neuromuscular blockade: increased airway collapsibility and blunted genioglossus muscle activity in response to negative pharyngeal pressure.

Background:Residual neuromuscular blockade increases the risk to develop postoperative complications. The authors hypothesized that minimal neuromuscular blockade (train-of-four [TOF] ratio 0.5–1) increases upper airway collapsibility and impairs upper airway dilator muscle compensatory responses to negative pharyngeal pressure challenges. Methods:Epiglottic and nasal mask pressures, genioglossus electromyogram, respiratory timing, and changes in lung volume were measured in awake healthy volunteers (n = 15) before, during (TOF = 0.5 and 0.8 [steady state]), and after recovery of TOF to unity from rocuronium-induced partial neuromuscular blockade. Passive upper airway closing pressure (negative pressure drops, random order, range +2 to –30 cm H2O) and pressure threshold for flow limitation were determined. Results:Upper airway closing pressure increased (was less negative) significantly from baseline by 54 ± 4.4% (means ± SEM), 37 ± 4.2%, and 16 ± 4.1% at TOF ratios of 0.5, 0.8, and 1.0, respectively (P < 0.01 vs. baseline for any level). Phasic genioglossus activity almost quadrupled in response to negative (–20 cm H2O) pharyngeal pressure at baseline, and this increase was significantly impaired by 57 ± 44% and 32 ± 6% at TOF ratios of 0.5 and 0.8, respectively (P < 0.01 vs. baseline). End-expiratory lung volume, respiratory rate, and tidal volume did not change. Conclusion:Minimal neuromuscular blockade markedly increases upper airway closing pressure, partly by impairing the genioglossus muscle compensatory response. Increased airway collapsibility despite unaffected values for resting ventilation may predispose patients to postoperative respiratory complications, particularly during airway challenges.

Neostigmine/Glycopyrrolate Administered after Recovery from Neuromuscular Block Increases Upper Airway Collapsibility by Decreasing Genioglossus Muscle Activity in Response to Negative Pharyngeal Pressure

Background:Reversal of residual neuromuscular blockade by acetylcholinesterase inhibitors (e.g., neostigmine) improves respiratory function. However, neostigmine may also impair muscle strength. We hypothesized that neostigmine administered after recovery of the train-of-four (TOF) ratio impairs upper airway integrity and genioglossus muscle function. Methods:We measured, in 10 healthy male volunteers, epiglottic and nasal mask pressures, genioglossus electromyogram, air flow, respiratory timing, and changes in lung volume before, during (TOF ratio: 0.5), and after recovery of the TOF ratio to unity, and after administration of neostigmine 0.03 mg/kg IV (with glycopyrrolate 0.0075 mg/kg). Upper airway critical closing pressure (Pcrit) was calculated from flow-limited breaths during random pharyngeal negative pressure challenges. Results:Pcrit increased significantly after administration of neostigmine/glycopyrrolate compared with both TOF recovery (mean ± SD, by 27 ± 21%; P = 0.02) and baseline (by 38 ± 17%; P = 0.002). In parallel, phasic genioglossus activity evoked by negative pharyngeal pressure decreased (by 37 ± 29%, P = 0.005) compared with recovery, almost to a level observed at a TOF ratio of 0.5. Lung volume, respiratory timing, tidal volume, and minute ventilation remained unchanged after neostigmine/glycopyrrolate injection. Conclusion:Neostigmine/glycopyrrolate, when administered after recovery from neuromuscular block, increases upper airway collapsibility and impairs genioglossus muscle activation in response to negative pharyngeal pressure. Reversal with acetylcholinesterase inhibitors may be undesirable in the absence of neuromuscular blockade.

Conservative Treatment of Paraplegia after Removal of an Epidural Catheter during Low-molecular-weight Heparin Treatment

EPIDURAL catheters are commonly used in today’s anesthetic practice, and complications are rare. However, hematomas within the spinal canal leading to compression of the spinal cord remain a major concern. In particular, anticoagulation and bleeding disorders are considered to be risk factors for hematoma formation after neuroaxial blockade. We report a case of paraplegia that developed after removal of a thoracic epidural catheter during low-molecular-weight heparin (LMWH) treatment. The patient’s symptoms improved spontaneously, and restitution was complete after conservative treatment.

A cemented caval vein filter: case report.

Study Design. Case report. Objective. To present a previously undescribed complication of bone cement use during spinal surgery. Summary of Background Data. Surgical cement reaching the circulation is a frequently described complication. The placement of caval vein filters is a routine measure in specific patients to prevent thrombotic material, usually from deep venous thrombosis in the lower extremities, from reaching the pulmonary circulation. A case of bone cement getting trapped in the caval filter rendering it unremovable has not been published. Methods. A 66-year-old patient underwent dorsal spondylodesis of the lumbar spine for superinfected metastasis with instability. Because of deep venous thrombosis of both femoral and iliac veins, a caval filter had been placed before surgery. Bone cement from the surgical procedure migrated into the venous bloodstream and got caught in the caval filter, thus rendering the filter unremovable. Results. Surgical removal of the filter was necessary. Conclusion. If caval filters are present in patients undergoing surgery involving the use of bone cement, the possibility of cement being caught by the filter must be considered.

Does teaching non-technical skills to medical students improve those skills and simulated patient outcome?

Objectives The purpose of this study is to evaluate the effects of a tailor-made, non-technical skills seminar on medical student’s behaviour, attitudes, and performance during simulated patient treatment. Methods Seventy-seven students were randomized to either a non-technical skills seminar (NTS group, n=43) or a medical seminar (control group, n=34). The human patient simulation was used as an evaluation tool. Before the seminars, all students performed the same simulated emergency scenario to provide baseline measurements. After the seminars, all students were exposed to a second scenario, and behavioural markers for evaluating their non-technical skills were rated. Furthermore, teamwork-relevant attitudes were measured before and after the scenarios, and perceived stress was measured following each simulation. All simulations were also evaluated for various medical endpoints. Results Non-technical skills concerning situation awareness (p<.01, r=0.5) and teamwork (p<.01, r=0.45) improved from simulation I to II in the NTS group. Decision making improved in both groups (NTS: p<.01, r=0.39; control: p<.01, r=0.46). The attitude ‘handling errors’ improved significantly in the NTS group (p<.05, r=0.34). Perceived stress decreased from simulation I to II in both groups. Medical endpoints and patients´ outcome did not differ significantly between the groups in simulation II. Conclusions This study highlights the effectiveness of a single brief seminar on non-technical skills to improve student’s non-technical skills. In a next step, to improve student’s handling of emergencies and patient outcomes, non-technical skills seminars should be accompanied by exercises and more broadly embedded in the medical school curriculum.

The impact of standardized patients on the training of medical students to manage emergencies

Background: Teaching emergency management should educate medical students not only for facts and treatment algorithms but also for time effective physical examination, technical skills, and team interaction. We tested the hypothesis, that using standardized emergency patients would be more effective in transmitting knowledge and skills compared with a more traditional teaching approach. Methods: Medical students (n = 242) in their fourth (second clinical) year were randomized to receive either training on standardized patients simulating 3 emergency settings (“acute chest pain,” “stroke,” and “acute dyspnea/asthma”) or traditional small group seminars. Before and after the respective training pathways, the students’ knowledge base (multiple-choice examination) and practical performance (objective structured clinical examination using 3 different emergency scenarios) were assessed. Results: Teaching using standardized patients resulted in a significant albeit small improvement in objective structured clinical examination scores (61.2 ± 3 for the standardized patient trained group vs 60.3 ± 3.5 for the traditional seminar group; P = 0.017, maximum achievable score: 66), but no difference in the written examination scores (27.4 ± 2.4 vs 27.0 ± 4.4; P = 0.341; maximum achievable score: 30). Conclusion: Teaching management of emergencies using standardized patients can improve medical students’ performance in clinical tests, and a change from traditional seminars in favor of practice sessions with standardized patients does not compromise the learning of medical facts.