Johannes H. van Oostrom

A comparison of traditional textbook and interactive computer learning of neuromuscular block

We designed an educational software package, RELAX, for teaching first-year anesthesiology residents about the pharmacology and clinical management of neuromuscular blockade. The software uses an interactive, problem-based approach and moves the user through cases in an operating room environment. It can be run on personal computers with Microsoft Windows[TM] (Microsoft Corp., Redmond, WA) and combines video, graphics, and text with mouse-driven user input. We utilized test scores 1) to determine whether our software was beneficial to the educational progress of anesthesiology residents and 2) to compare computer-based learning with textbook learning. Twenty-three residents were divided into two groups matched for age and sex, and a pretest was administered to all 23 residents. There was no significant difference (P > 0.05) in the pretest scores of the two groups. Three weeks later, both groups were subjected to an educational intervention: one with our computer software and the other with selected textbooks. Both groups took a posttest immediately after the intervention. The test scores of the computer group improved significantly more (P < 0.05) than those of the textbook group. Although prior to the study the two groups showed no statistical difference in their familiarity with computers, the computer group reported much higher satisfaction with their learning experience than did the textbook group (P < 0.0001). (Anesth Analg 1997;84:657-61)

Patient repositioning and pressure ulcer risk—Monitoring interface pressures of at-risk patients

Repositioning patients regularly to prevent pressure ulcers and reduce interface pressures is the standard of care, yet prior work has found that standard repositioning does not relieve all areas of at-risk tissue in nondisabled subjects. To determine whether this holds true for high-risk patients, we assessed the effectiveness of routine repositioning in relieving at-risk tissue of the perisacral area using interface pressure mapping. Bedridden patients at risk for pressure ulcer formation (n = 23, Braden score <18) had their perisacral skin-bed interface pressures recorded every 30 s while they received routine repositioning care for 4-6 h. All participants had specific skin areas (206 +/- 182 cm(2)) that exceeded elevated pressure thresholds for >95% of the observation period. Thirteen participants were observed in three distinct positions (supine, turned left, turned right), and all had specific skin areas (166 +/- 184 cm(2)) that exceeded pressure thresholds for >95% of the observation period. At-risk patients have skin areas that are likely always at risk throughout their hospital stay despite repositioning. Healthcare providers are unaware of the actual tissue-relieving effectiveness (or lack thereof) of their repositioning interventions, which may partially explain why pressure ulcer mitigation strategies are not always successful. Relieving at-risk tissue is a necessary part of pressure ulcer prevention, but the repositioning practice itself needs improvement.

Learning about new anesthetics using a model driven, full human simulator.

Objective.New pharmacological agents are introduced into medical practice at an ever-increasing pace. Teaching how to use new medications in the clinical setting presents educational challenges and puts patients at risk. Methods.Patients and clinical settings in which remifentanil might provide clinical advantages over existing anesthetics were identified. A simulator curriculum was developed to demonstrate the use of remifentanil in the sample cases. The simulation was designed to highlight the clinical advantages and potential side effects of remifentanil. A screen displaying the concentrations of remifentanil in plasma and in the hypothetical effector site was developed. A simulator was modified (addition of an infusion pump and a pharmacokinetic screen display) and transported to several cities in the U.S.A. An instructor guided small groups of anesthesiologists and anesthetists through a structured program that enabled participants to observe drug effects in simulated patients. Results.There were 836 participants in the remifentanil program, which was offered in 58 cities in the U.S.A. Surveys were completed by 574 anesthesiologists. There was a significant difference in comfort level for using remifentanil after the session compared to before (Chi-square, p< 0.001.) The statement: “Clinical simulation experience is a means to learn about new agents like remifentanil”was rated as “excellent” by 81% and as “good” by 19% of participants. No participant found the experience to be “not useful.” Conclusions.Patient simulation is a novel method of introducing new drugs to the medical community and is perceived by anesthesia providers as a valuable addition to available teaching methods.

A Longitudinal Description of Heart Rate Variability in 28—34-Week-Old Preterm Infants

The purpose of this study was to longitudinally describe changes in heart rate variability (HRV) from 28 to 34 weeks postmenstrual age (PMA). A convenience sample of 31 low-risk preterm infants participated. HRV was quantified using a spectral analysis of heart periods and recorded during seven weekly test sessions from an electrocardiogram (ECG) signal. The total range of frequency components (0.04—2.0 Hz), high-frequency (HF) components (0.30—1.3 Hz), and ratio of low-to-high frequency (LF/HF) components (0.04—0.20/ 0.30—1.3 Hz) were measured. A mixed general linear model analysis revealed no significant change over weekly test sessions for the total, the high, and the ratio of LF/HF components. A significant interaction effect was, however, noted in the HF components for test session × gender (df = 1; F = 4.85; p = .030). With increasing age, the HF components for females increased or displayed a pattern of HRV indicative of a more mature autonomic nervous system (ANS). Study findings warrant further investigation of the impact of gender on normative descriptions of HRV.

Comparative Testing of Pulse Oximeter Probes

The testing of pulse oximeter probes is generally limited to the integrity of the electrical circuit and does not include the optical properties of the probes. Few pulse oximeter testers evaluate the accuracy of both the monitor and the probe. We designed a study to compare the accuracy of nonproprietary probes (OSS Medical) designed for use with Nellcor, Datex-Ohmeda, and Criticare pulse oximeter monitors with that of their corresponding proprietary probes by using a commercial off-the-shelf pulse oximeter tester (Index). The Index pulse oximeter tester does include testing of the optical properties of the pulse oximeter probes. The pulse oximeter tester was given a controlled input that simulated acute apnea. Desaturation curves were automatically recorded from the pulse oximeter monitors with a data-collection computer. Comparisons between equivalent proprietary and nonproprietary probes were performed. Data were analyzed by using univariate and multivariate general linear model analysis. Five OSS Medical probe models were statistically better than the equivalent proprietary probes. The remainder of the probes were statistically similar. Comparative and simulation studies can have significant advantages over human studies because they are cost-effective, evaluate equipment in a clinically relevant scenario, and pose no risk to patients, but they are limited by the realism of the simulation.

The Stealth Station Image Guidance System may interfere with pulse oximetry.

PurposeInterference on pulse oximetry can come from many sources. We found an additional source of interference from the Stealth Station. This article gives an overview of sources of pulse oximeter interference so that clinicians can better prevent them.Technical featuresThis article discusses the infrared disturbances caused by the Stealth Station. The Stealth Station is a frameless stereotactic positioning system that utilizes a three dimensional location system to measure the position of the patient and the surgical tools, and to relate those positions to previously recorded imaging. To understand the disturbance caused by the Stealth Station, we discuss its operation and that of pulse oximeter monitors. Pulse oximeter interference can come from volume artifacts, electrical and light noise, and can be caused by issues related to the patient. Because the passive Stealth Station contains a strong infrared light source, interference caused by light is a likely reason for the interference we noted. Pulse oximeters rely on the timevariant light signal modulated by arterial volume variations in the finger. Although relatively immune to static light sources, pulse oximeters are extremely sensitive to time-varying light sources. The light emitted by the passive Stealth Station is time-varying at 4 Hz and this is causing the pulse oximeter to provide invalid results. Shielding can generally be used to stop the light from the Stealth Station from being picked up by the pulse oximeter sensor.ConclusionInfrared light interference can be very common, but is easily dealt with if one is aware of it.ObjectifL’interférence sur la sphygmo-oxymétrie peut provenir de nombreuses sources, dont une nouvelle provenant de la Stealth Station. Nous présentons un aperçu des interférences avec le sphygmo-oxymètre, ce qui permettra aux cliniciens de la prévenir.Caractéristiques techniquesLa Stealth Station est un système de positionnement stéréotaxique sans cadre qui utilise un système de repérage en trois dimensions pour mesurer la position réelle du patient et des instruments chirurgicaux et pour relier cette position à des images virtuelles préalablement enregistrées.L’interférence avec le sphygmo-oxymètre peut provenir d’artéfacts volumique, des produits électriques et de légers bruits et elle peut être causée par des problèmes reliés au patient. Comme la Stealth Station passive contient une puissante source de lumière à infrarouges, c’est une raison probable de l’interférence notée. Les sphygmo-oxymètres dépendent du signal lumineux variable dans le temps qui est modulé par les variations du volume artériel dans le doigt. Bien que relativement soustraits aux sources de lumière statiques, les sphygmo-oxymètres sont extrêmement sensibles aux sources de lumière variables dans le temps. La lumière émise par la Stealth Station passive varie dans le temps à 4 Hz, ce qui invalide certains résultats au sphygmooxymètre. Une protection peut généralement être utilisée pour empêcher la lumière provenant de la Stealth Station d’être captée par le détecteur du sphygmo-oxymètre.ConclusionL’interférence de la lumière infrarouge peut se rencontrer souvent, mais on peut facilement la contourner pourvu qu’on en prenne conscience.

Modeling in anesthesia.

A model can be defined as an abstraction of reality which accounts for those properties of a phenomenon that are pertinent to the purpose of the model. Models are used in anesthesia to understand the various physiologic, pharmacological and physical processes that occur during anesthesia. Indeed, many different types of models that comply with our definition can be distinguished. Early models consisted of electrical models of the arterial blood dynamics and cardiovascular system. Physical models of drug uptake and distribution have been developed to explain the kinetics of volatile anesthetics in the body. The goal of this paper is to introduce the reader to some of the types of models that have been used to facilitate education and research in anesthesia. These examples will elucidate the steps involved in developing a model and the various types of models that have been proven useful

Waste Gas Monitor Reduces Wasted Volatile Anesthetic

Objective. The increasing focus on health care costs requires that all physicians evaluate practice behaviors. The primary emphasis in anesthesia has been limiting the use of expensive medications and interventions. Reducing waste is another approach, and volatile anesthetics are an appropriate target in that simple reduction of fresh gas flow (FGF) rates is effective. A monitor that measures and displays the cost of wasted volatile anesthetic was developed and used to determine if real-time display of the cost would result in decreased FGF rates, which, in turn, would decrease wasted anesthetic. Methods. The waste gas monitor (WGM) measures flow rate at the anesthesia machines scavenger port, integrates this with agent concentration, and displays the calculated cost, real-time, on a portable computer screen. The WGM equipment was attached to the anesthesia machine in the gynecologic surgery operating room (OR) and those cases performed under general endotracheal anesthesia and lasting longer than one hour were eligible for inclusion. First year anesthesiology residents assigned to the study OR as part of a non-specialty rotation, were the subjects of the study. For each resident, after data were collected from at least two eligible baseline cases (Baseline Phase, WGM not visible and resident unaware of its presence), the monitor was introduced and data collection continued for at least three more eligible cases (Visible Phase). Results. Nine residents were initially enrolled, but due to scheduling difficulties only five residents completed the protocol. Data from cases using the WGM demonstrated a 50% decrease (3.58 ± 1.34 l/min vs. 1.78 ± 0.51 l/min (p = 0.009)) in the scavenger flow rates, which resulted in a 48% (

Verification and validation of physiology simulators.

5.28 ± 0.68 vs.

Ventilation apparatus and anesthesia delivery system

2.72 ± 0.80 (p = 0.002)) decrease in hourly cost of wasted volatile anesthetic. There was no difference between the Baseline and Visible phases with regard to use of nitrous oxide or intravenous anesthetic agents. Conclusions. The WGM decreased wasted volatile anesthetic by encouraging decreased FGF rates.