Matthew B. Weinger

Retrospective data collection and analytical techniques for patient safety studies

To enhance patient safety, data about actual clinical events must be collected and scrutinized. This paper has two purposes. First, it provides an overview of some of the methods available to collect and analyze retrospective data about medical errors, near misses, and other relevant patient safety events. Second, it introduces a methodological approach that focuses on non-routine events (NRE), defined as all events that deviate from optimal clinical care. In intermittent in-person surveys of anesthesia providers, 75 of 277 (27%) recently completed anesthetic cases contained a non-routine event (98 total NRE). Forty-six of the cases (17%) had patient impact while only 20 (7%) led to patient injury. In contrast, in the same hospitals over a two-year period, we collected event data on 135 cases identified with traditional quality improvement processes (event incidence of 0.7-2.7%). In these quality improvement cases, 120 (89%) had patient impact and 74 (55%) led to patient injury. Preliminary analyses not only illustrate some of the analytical methods applicable to safety data but also provide insight into the potential value of the non-routine event approach for the early detection of risks to patient safety before serious patient harm occurs.

Development and Evaluation of a Graphical Anesthesia Drug Display

Background Usable real-time displays of intravenous anesthetic concentrations and effects could significantly enhance intraoperative clinical decision-making. Pharmacokinetic models are available to estimate past, present, and future drug effect-site concentrations, and pharmacodynamic models are available to predict the drugs associated physiologic effects. Methods An interdisciplinary research team (bioengineering, architecture, anesthesiology, computer engineering, and cognitive psychology) developed a graphic display that presents the real-time effect-site concentrations, normalized to the drugs’ EC95, of intravenous drugs. Graphical metaphors were created to show the drugs’ pharmacodynamics. To evaluate the effect of the display on the management of total intravenous anesthesia, 15 anesthesiologists participated in a computer-based simulation study. The participants cared for patients during two experimental conditions: with and without the drug display. Results With the drug display, clinicians administered more bolus doses of remifentanil during anesthesia maintenance. There was a significantly lower variation in the predicted effect-site concentrations for remifentanil and propofol, and effect-site concentrations were maintained closer to the drugs’ EC95. There was no significant difference in the simulated patient heart rate and blood pressure with respect to experimental condition. The perceived performance for the participants was increased with the drug display, whereas mental demand, effort, and frustration level were reduced. In a postsimulation questionnaire, participants rated the display to be a useful addition to anesthesia monitoring. Conclusions The drug display altered simulated clinical practice. These results, which will inform the next iteration of designs and evaluations, suggest promise for this approach to drug data visualization.

Methylnaloxonium diffuses out of the rat brain more slowly than naloxone after direct intracerebral injection

The value of intracerebral injections as a means of relating brain structure and function is dependent on the degree of site specificity of the injection. The purpose of this study was to compare the distribution over time of naloxone and its quaternary derivative, methylnaloxonium, after intracerebral microinjection. One microliter of tritiated naloxone (NAL) or methylnaloxonium (MN 10.0 ng, 12.8 nCi for both drugs) was infused directly into the n. raphe pontis. Each animal was then decapitated at a specific time (2.5, 5.0, 15, 30, or 60 min), the brain was removed and dissected into hindbrain, cerebellum, midbrain and cortex. Tritium beta emissions of brain homogenates were measured 1 day later, MN remained better localized to the injection site than did the same volume of the more lipophilic NAL. Within 15 minutes, less than 5% of the NAL remained in the hindbrain compared with nearly 40% of the MN. These results that MN may be a better probe than NAL for investigating the relationship of opioid receptor anatomy and function, particularly for dependent variables requiring sustained time courses.

Drug wastage contributes significantly to the cost of routine anesthesia care.

STUDY OBJECTIVE To complement previous studies that employed indirect methods of measuring anesthesia drug waste. DESIGN Prospective, blinded observational study. SETTING Operating rooms of a single university hospital. SUBJECTS Anesthesia providers practicing in this setting who were completely unaware of the conduct of the study. MEASUREMENTS All opened and unused or unusable intravenous (IV) anesthesia drugs left over at the end of each workday were collected over a randomly selected typical 2-week period. MAIN RESULTS 166 weekday cases were performed. Thirty different drugs were represented in the 157 syringes and 139 ampoules collected. Opioid waste as well as opened vials that became outdated were counted in the tally. Based on actual hospital drug acquisition costs,

Alterations in diaphragm EMG activity during opiate-induced respiratory depression

1,802 of drugs were wasted during this 2-week period (

Quantitative description of the workload associated with airway management procedures

300/OR), amounting to an average cost per case of

Brain sites mediating opiate-induced muscle rigidity in the rat: methylnaloxonium mapping study

10.86. On a cost basis, six drugs accounted for three quarters of the total wastage: phenylephrine (20.8%), propofol (14.5%), vecuronium (12.2%), midazolam (11.4%), labetalol (9.1%), and ephedrine (8.6%). Because incompletely used syringes or vials that were discarded in the trash were not measured in this analysis, the results may underestimate the total cost of drug wastage at this institution by up to 40%. CONCLUSIONS The results of this study are similar to those of previous studies that employed electronic record keeping techniques to calculate drug waste. Intravenous drugs that are prepared but unused may be a significant cost of intraoperative anesthesia care. Methods to reduce the amount of drug wasted are proposed.

Ventilatory response to 2-h sustained hypoxia in humans.

While opiate-induced increases in thoracic muscle tone may contribute to impaired ventilation during opiate anesthesia, the effects of high-dose opiates on diaphragm muscle activity have not been elucidated. The effects of the opiate agonist alfentanil (ALF, 500 micrograms/kg subcutaneously) on diaphragm (DIA) and intercostal (IC) electromyographic (EMG) activity in spontaneously ventilating adult rats were studied. EMG segments corresponding to inspiration and expiration were selected using an impedance plethysmographic respiratory waveform. Total EMG activity over a respiratory cycle was significantly greater in the DIA than in the IC. ALF produced a decrease in inspiratory and an increase in expiratory DIA EMG activity. These changes in diaphragm function following ALF were accompanied by significant respiratory depression. The effects of the alpha-2 agonist dexmedetomidine on ALF-induced changes in diaphragm and intercostal EMG activity were also examined. While dexmedetomidine alone had minimal effects on DIA activity, it significantly attenuated the ALF-induced increase in expiratory DIA EMG. The potential etiology and implications of these opiate-induced changes in diaphragm muscle function are discussed.

Double-blind evaluation of patient-controlled epidural analgesia during labor

STUDY OBJECTIVES To measure the workload associated with specific airway management tasks. SETTING AND INTERVENTION Written survey instrument. PATIENTS 166 Stanford University and 75 University of California, San Diego, anesthesia providers. MEASUREMENTS AND MAIN RESULTS Subjects were asked to use a seven-point Likert-type scale to rate the level of perceived workload associated with different airway management tasks with respect to the physical effort, mental effort, and psychological stress they require to perform in the typical clinical setting. The 126 subjects completing questionnaires (overall 52% response rate) consisted of 43% faculty, 26% residents, 23% community practitioners, and 8% certified registered nurse-anesthetists (CRNAs). Faculty physicians generally scored lower workload measures than residents, whereas community practitioners had the highest workload scores. Overall, workload ratings were lowest for laryngeal mask airway (LMA) insertion and highest for awake fiberoptic intubation. Airway procedures performed on sleeping patients received lower workload ratings than comparable procedures performed on awake patients. Direct visualization procedures received lower workload ratings than fiberoptically guided procedures. CONCLUSIONS These kinds of data may permit more objective consideration of the nonmonetary costs of technical anesthesia procedures. The potential clinical benefits of the use of more complex airway management techniques may be partially offset by the impact of increased workload on other clinical demands.

A role for CNS α-2 adrenergic receptors in opiate-induced muscle rigidity in the rat

Previous work has demonstrated that direct injections of methylnaloxonium (MN), a hydrophilic quaternary opiate antagonist, in the area of the nucleus raphe pontis (RPn) significantly attenuated alfentanil-induced muscle rigidity in the rat. To extend these observations and to explore further the regions important for opiate-induced rigidity, rats were implanted with chronic guide cannulae aimed at discrete brain sites with an emphasis on the region from the periaqueductal grey (PAG) to the RPn. Each animal was pretreated by a blinded observer with an intracerebral injection of MN (125 ng total dose) or saline, and electromyographic (EMG) activity was recorded from the gastrocnemius muscle. Alfentanil (ALF; 500 micrograms/kg) was then administered subcutaneously and the magnitude of tonic EMG activity was assessed as a measure of hindlimb rigidity. The administration of MN into the pontine raphe nucleus (RPn) and also into the more lateral nucleus reticularis tegmenti pontis significantly attenuated ALF rigidity compared with saline-pretreated controls. Within the midbrain, MN selectively reversed rigidity when injected into the periaqueductal grey (PAG). The dorsal PAG appeared to be a more important site than the ventral PAG. There was no significant effect on ALF rigidity of MN injections into brain regions between the ventral PAG and the RPn while MN injections into the deep layers of the superior colliculus, lateral to the dorsal PAG, partially attenuated ALF rigidity. In contrast, rigidity was not consistently reversed after MN injections into the basal ganglia, the dorsal superior colliculus, or the region of the decussation of the dorsal tegmentum. This study provides strong evidence that nuclei of the reticular formation, specifically the PAG, raphe pontis, and reticularis tegmenti pontis that are known to play a role in other opioid-mediated behaviors, are important in opiate-induced muscle rigidity in the rat. These results could have implications for the prevention of this undesirable effect of high-dose opiate administration.