Robust closed-loop control of induction and maintenance of propofol anesthesia in children

BACKGROUND

During closed-loop control, a drug infusion is continually adjusted according to a measure of clinical effect (e.g., an electroencephalographic depth of hypnosis (DoH) index). Inconsistency in population-derived pediatric pharmacokinetic/pharmacodynamic models and the large interpatient variability observed in children suggest a role for closed-loop control in optimizing the administration of intravenous anesthesia.

OBJECTIVE

To clinically evaluate a robustly tuned system for closed-loop control of the induction and maintenance of propofol anesthesia in children undergoing gastrointestinal endoscopy.

METHODS

One hundred and eight children, aged 6-17, ASA I-II, were enrolled. Prior to induction of anesthesia, NeuroSENSE™ sensors were applied to obtain the WAVCNS DoH index. An intravenous cannula was inserted and lidocaine (0.5 mg·kg(-1) ) administered. Remifentanil was administered as a bolus (0.5 μg·kg(-1) ), followed by continuous infusion (0.03 μg·kg(-1) ·min(-1) ). The propofol infusion was closed-loop controlled throughout induction and maintenance of anesthesia, using WAVCNS as feedback.

RESULTS

Anesthesia was closed-loop controlled in 102 cases. The system achieved and maintained an adequate DoH without manual adjustment in 87/102 (85%) cases. Induction of anesthesia (to WAVCNS  ≤ 60) was completed in median 3.8 min (interquartile range (IQR) 3.1-5.0), culminating in a propofol effect-site concentration (Ce ) of median 3.5 μg·ml(-1) (IQR 2.7-4.5). During maintenance of anesthesia, WAVCNS was measured within 10 units of the target for median 89% (IQR 79-96) of the time. Spontaneous breathing required no manual intervention in 91/102 (89%) cases.

CONCLUSIONS

A robust closed-loop system can provide effective propofol administration during induction and maintenance of anesthesia in children. Wide variation in the calculated Ce highlights the limitation of open-loop regimes based on pharmacokinetic/pharmacodynamic models.

Degradable PLGA scaffolds with basic fibroblast growth factor: experimental studies in myocardial revascularization

Our goal was to investigate the efficacy of degradable poly(D,L-lactic-coglycolic acid) (PLGA) scaffolds loaded with basic fibroblast growth factor (bFGF) in inducing cardiac neovascularization, increasing perfusion, and improving cardiac function.For ease of scaffold implantation into the ventricular wall, we developed a channel-producing device. Mini-swine, established as the animal model, were grouped as follows: channels-alone (control) group, channels and blank scaffolds (CBS) group, and channels and bFGF-incorporating scaffolds (CFS) group. Two scaffolds were implanted in each animal in the CBS and CFS groups. Six weeks postoperatively, endothelial cells were immunohistologically stained for von Willebrand factor, and proliferating cells for Ki-67 antigen. The density of new vessels was counted by image-analysis software. Left ventricular function and myocardial perfusion were documented by echocardiography and nuclear scanning, respectively, before implantation and 6 weeks postoperatively.The combined application of PLGA and bFGF ensured sustained release of growth factor in the target region. In the CFS group, Ki-67-positively stained cells, vascular density, and perfusion-defect percentage all showed significant improvement (P < 0.001), compared with the control and CBS groups, which did not. Moreover, the left ventricular fractional shortening percentage in the CFS group (28.98% +/- 1.24%) showed a significant increase, compared with the control group (26.57% +/- 1.92%, P = 0.009) and the CBS group (27.11% +/- 0.71%, P = 0.033), neither of which showed a difference (P = 0.508).The bFGF-incorporating PLGA scaffold can promote neovascular formation, enhance blood-flow perfusion, and improve myocardial function, although the original scaffold lumina were eventually occluded by inflammatory cells and scar tissue.