Control strategy with multivariable fault tolerance module for automatic intravenous anesthesia

In the anesthesia automation, an automatic propofol infusion system uses Bi-spectral Index Signal (BIS) as a primary feedback signal to manipulate propofol dose. However, the BIS signal may be suspended for some time due to poor EEG signal quality, noise, and many other factors. Therefore, BIS signal failure may be the main cause of inadequate propofol infusion. This fact motivates the need for integration of multivariable fault tolerance module (MFTM) and fractional-order Smith predictor controller to avoid adverse reactions of inadequate propofol dosing during BIS failure. Smith Predictor control strategy is sufficiently robust to predict feedback BIS during BIS failure via patient pharmacological modeled BIS. However, modeled BIS may not provide a guarantee of adequate propofol infusion during BIS failure and especially in the presence of hypotension and hypertension. Thus, the proposed control strategy is designed with MFTM to detect BIS sensor fault and to estimate feedback BIS during BIS failure. Further, the proposed control strategy is designed with a multivariable pharmacological patient model to analyze the cross effect of propofol infusion on BIS and hemodynamic variables. The robustness of the proposed control strategy is tested in the presence of noxious surgical stimulation, BIS sensor fault and heavy hemodynamic disturbance. The pharmacological parameters and recorded signals of 30 patients during various surgeries have been used to validate simulated results. The performance of the proposed control strategy assures optimization and smooth propofol infusion during BIS failure. The proposed system provides stability for a wide range of physiological parameters range. The proposed scheme maintains smooth BIS and MAP signal despite the delay, BIS sensor fault, and surgical disturbances.

Developmental and cardiac toxicities of propofol in zebrafish larvae

Propofol, a commonly used anesthetic, is convenient to use, induces quick effect, enables rapid recovery, and is widely accessible given its stable supply. However, its adverse effects are a concern. Reportedly, propofol exhibits a significant inhibitory effect on the respiratory and circulatory systems. Furthermore, intravenous administration of this drug results in hypotension, rapid heart rate, and respiratory failure. Because many pregnant women are administered propofol during childbirth, it may have a significant negative effect on the development of infants. Propofol can cause considerable developmental neurotoxicity and has known activity on the heart. However, the underling mechanisms of these toxicities remain unclear. In the present study, zebrafish embryos were exposed to propofol at different concentrations (0.05, 0.1, 0.5, 1, 5, 10, and 20 μg/ml) to determine its developmental and cardiac toxicities. Propofol exposure decreased the survival rate and hatchability of zebrafish embryos. Additionally, the embryo malformation rate increased in a concentration-dependent manner. Different types of malformations were observed following propofol administration. The proportion of pericardial cysts increased, whereas the heart rate and size decreased with an increase in propofol concentration. The quantitative reverse-transcription polymerase chain reaction revealed that propofol significantly altered the expression of genes related to cardiac development and functions in zebrafish. Collectively, our findings indicate that propofol exposure induces significant developmental and cardiac toxicities in zebrafish.

Characterizing the time-course of antihypertensive activity and optimal dose range of fimasartan via mechanism-based population modeling

Fimasartan is a novel angiotensin II receptor blocker. Our aims were to characterize the time-course of the antihypertensive activity of fimasartan via a new population pharmacokinetic/pharmacodynamic model and to define its optimal dose range. We simultaneously modelled all fimasartan plasma concentrations and 24-h ambulatory blood pressure monitoring (ABPM) data from 39 patients with essential hypertension and 56 healthy volunteers. Patients received placebo, 20, 60, or 180mg fimasartan every 24h for 28days and healthy volunteers received placebo or 20 to 480mg as a single oral dose or as seven doses every 24h. External validation was performed using data on 560 patients from four phase II or III studies. One turnover model each was used to describe diastolic and systolic blood pressure. The input rates into these compartments followed a circadian rhythm and were inhibited by fimasartan. The average predicted (observed) diastolic blood pressure over 24-h in patients decreased by 10.1±7.5 (12.6±9.2; mean±SD)mmHg for 20mg, 14.2±7.0 (15.1±9.3) mmHg for 60mg, and 15.9±6.8 (11.5±9.9)mmHg for 180mg daily relative to placebo. The model explained the saturation of antihypertensive activity by counter-regulation at high fimasartan concentrations. Drug effect was maximal at approximately 23ng/mL fimasartan for diastolic and 12ng/mL for systolic blood pressure. The proposed mechanism-based population model characterized the circadian rhythm of ABPM data and the antihypertensive effect of fimasartan. After internal and external model validation, 30 to 60mg oral fimasartan given once daily was predicted as optimal dose range.