Michael F. O’Connor

BIS monitoring to prevent awareness during general anesthesia.

Background Unexpected awareness is a rare but well-described complication of general anesthesia that has received increased scientific and media attention in the past few years. Transformed electroencephalogram monitors, such as the Bispectral Index monitor, have been advocated as tools to prevent unexpected recall. Methods The authors conducted a power analysis to estimate how many patients would be needed in an appropriately powered study to demonstrate the Bispectral Index monitor reduces awareness, as well as a cost analysis to assess the cost of using the monitor for this purpose alone. Results If unexpected recall is rare (1 in 20,000), it will require a large study to demonstrate that the monitor reduces awareness (200,000–800,000 patients), and the cost of using it for this purpose alone would be high (

Discovering Healthcare Cognition: The Use of Cognitive Artifacts to Reveal Cognitive Work

400,000 per case prevented). If awareness is common (1 in 100), then the number of patients needed in a study to demonstrate that the monitor works becomes tractable (1,000–4,000 patients), and the cost of using the monitor for this purpose alone becomes lower (

The role of the vasculature in regulating venous return and cardiac output: historical and graphical approach

2,000 per case prevented). Because there are reported cases of awareness despite Bispectral Index monitoring, the authors are certain that the effectiveness of the monitor is less than 100%. As the performance of the monitor decreases from 100%, the size of the study needed to demonstrate that it works increases, as does the cost of using it to prevent awareness. Conclusion The contention that Bispectral Index monitoring reduces the risk of awareness is unproven, and the cost of using it for this indication is currently unknown.

Concurrence of Intraoperative Hypotension, Low Minimum Alveolar Concentration, and Low Bispectral Index Is Associated with Postoperative Death

Healthcare systems, especially hospital operating room suites, have properties that make them ideal for the study of the cognitive work using the naturalistic decision-making (NDM) approach. This variable, complex, high-tempo setting provides a unique opportunity to examine the ways that clinicians plan, monitor, and cope with the irreducible uncertainty that underlies this work domain. As frontline managers, anesthesia coordinators plan and manage anesthesia assignments for surgical procedures. As frontline managers, coordinators develop and use cognitive artifacts to distribute cognition across time and among members of the acute care staff. Examination of these cognitive artifacts and their use reveals the hidden subtleties of the coordinators’ work. The use of NDM methods including cognitive artifact analysis to understand cognitive work generates insights that extend beyond the operator level to the study of team-level cognition. Results can be used to create computer-based artifacts that aid individual and team cognition.

Anesthesia advanced circulatory life support

AbstractPurposeTo review the physiology of cardiac output regulation by the peripheral vasculature. This will enable the clinician to understand and manage the complex circulatory changes in vanous forms of shock, and in other common altered circulatory states encountered in anaesthetic practice.SourceArticles were obtained from a Medline review (1966 to present; search terms: shock, venous return, cardiac output) and a hand search (Index Medicus). Other sources include review articles, personal files, and textbooks.Principal findingsAt steady state, cardiac output is equal to venous return (VR). Venous return depends on mean systemic pressure (PMS, which is the pressure in the peripheral vasculature driving blood flow to the heart, right atrial pressure (PRA, and the resistance to venous return (Rv. When considenng VR, PRA is the downstream pressure to VR. and not simply an indirect measure of the volume status. The pressure gradient for VR is, therefore, PMS−PRA, and in a system obeying Ohm’s Law,

Sensemaking, safety, and cooperative work in the intensive care unit

VR = \frac{{P_{MS} - P_{RA} }}{{R_{RA} }}

Technological Distractions (part 2): A Summary of Approaches to Manage Clinical Alarms With Intent to Reduce Alarm Fatigue

Shock and other altered circulatory states cause changes in both VR and cardiac function. The circulation can be conveniently described by a venous return and a cardiac output curve. By drawing these curves for each clinical situation. a clear understanding of the altered circulatory state is obtained, and treatment options can be clearly defined.ConclusionThe peripheral circulation controls cardiac output in many clinical conditions. Manipulation of the peripheral circulation is as important to the successful treatment of shock and other altered circulatory states, as is the manipulation of cardiac output.RésuméObjectifRevoir la physiologie de la régulation vasculaire périphérique du débit cardiaque. Ceci devrait permettre au clinicien de comprendre et de prendre en charge les changements circulatoires complexes survenant dans les états de choc et autres états d’instabilité circulatoire rencontrés en anesthésie.SourceLes articles ont été compilés grâce à un survol deMedline (de 1966 jusqu’à maintenant: mots-clés: choc, retour veineux, débit cardiaque) et une recherche manuelle (Index Medicus). Des articles de revue, des dossiers personnels et des manuels ont aussi été utilisés.Principales constatationsÀ l’état d’équilibre, le débit cardiaque est égal au retour veineux (RV). Le RV dépend de la pression systolique moyenne (PSM) laquelle est constituée de la pression vasculaire périphériques qui arnène le sang au coeur, la pression aunculaire droite (PAD) et la résistance au retour veineux (RV Si on examine le RV on constate que la PAR est la pression d’aval du RV et non simplement une mesure indirecte de la volémie. Le gradient de la pression pour RV est donc PSM−PRA et ce système obéit à la loi d’Ohm.