ABSTRACT
BACKGROUND: Facial electromyography (FEMG) may have utility in the assessment of nociception during surgery. The difference between state entropy (SE) and response entropy (RE) is an indirect measure of FEMG. This study assesses an automated algorithm for remifentanil administration that is based on maintaining an entropy difference (ED) that is less than an upper boundary condition and greater than a lower boundary condition. METHODS: The algorithm was constructed with a development set (n = 40), and then automated and studied with a validation set (n = 20) of patients undergoing anterior cruciate ligament repair. The percentage of time that the ED was maintained between the two boundary conditions was determined. Remifentanil and propofol predicted effect-site concentrations (Ce) were determined at surgical milestones and, after drug discontinuation, the time to response to verbal stimulation and orientation was measured. RESULTS: The median (25th-75th percentile) per cent of time that the ED was recorded between the boundary conditions was 99.3% (98.1-99.8%). Predicted propofol (microg ml(-1)) and remifentanil (ng ml(-1)) Ce (sd), respectively, were 3.5 and 4.0 at induction, 1.9 (0.8) and 7.2 (3.7) at the end of surgery, and 1.1 (0.5) and 3.2 (2.2) at eye opening. The median time to eye opening and orientation was 3.8 and 6.8 min, respectively. CONCLUSION: This feasibility study supports the concept that remifentanil may be delivered using an algorithm that maintains the difference between SE and RE between the upper and lower boundary condition.
Subject(s)
Analgesics, Opioid/administration & dosage , Drug Monitoring/methods , Piperidines/administration & dosage , Acoustic Stimulation , Adolescent , Adult , Algorithms , Analgesics, Opioid/pharmacology , Anesthesia Recovery Period , Anesthetics, Intravenous , Anterior Cruciate Ligament/surgery , Awareness/drug effects , Drug Administration Schedule , Electromyography/drug effects , Electromyography/methods , Entropy , Feasibility Studies , Female , Humans , Male , Middle Aged , Monitoring, Intraoperative/methods , Movement/drug effects , Piperidines/pharmacology , Propofol , Remifentanil , Signal Processing, Computer-AssistedABSTRACT
In this case a woman underwent a cervical laminectomy with a total i.v. anaesthesia technique and during her care two problems occurred with propofol delivery. In both cases, bispectral index increases alerted caregivers to the decreased propofol delivery and allowed them to make corrections in a manner timely enough to prevent the occurrence of awareness during anaesthesia. The case illustrates how intraoperative processed electroencephalographic monitoring may decrease the incidence of recall of awareness following surgery.
Subject(s)
Anesthesia, General , Awareness , Electroencephalography , Intraoperative Complications/diagnosis , Isoflurane/analogs & derivatives , Mental Recall , Monitoring, Intraoperative/methods , Adult , Anesthesia, General/instrumentation , Anesthetics , Cervical Vertebrae , Desflurane , Equipment Failure , Female , Fentanyl , Humans , Intraoperative Complications/prevention & control , Intraoperative Complications/psychology , Laminectomy , Monitoring, Intraoperative/instrumentation , Nerve Compression Syndromes/surgery , Piperidines , Propofol , Psychological Tests , Remifentanil , Shoulder Pain/psychology , Shoulder Pain/surgery , Signal Processing, Computer-AssistedABSTRACT
One-dimensional microcavities are optical resonators with coplanar reflectors separated by a distance on the order of the optical wavelength. Such structures quantize the energy of photons propagating along the optical axis of the cavity and thereby strongly modify the spontaneous emission properties of a photon-emitting medium inside a microcavity. This report concerns semiconductor light-emitting diodes with the photon-emitting active region of the light-emitting diodes placed inside a microcavity. These devices are shown to have strongly modified emission properties including experimental emission efficiencies that are higher by more than a factor of 5 and theoretical emission efficiencies that are higher by more than a factor of 10 than the emission efficiencies in conventional light-emitting diodes.
