Early and late results of surgical repair of truncus arteriosus

Ninety-two patients had corrective operation for truncus arteriosus between 1967 and 1975. During the first 30 days after surgery, 23 patients died. No significant differences appear between early mortality and sex, type of truncus, variations in pulmonary arterial anatomy, truncal valve regurgitation, associated anomalies, previous operation, or duration of extracorporeal circulation. Greater risk is probably encountered with the higher but still operable levels of pulmonary resistance. Reoperation has been required in three patients. Fifty-nine percent of survivors are symptom-free, with all but two of the remainder (38%) being in NYHA functional class II. The late result is suggestively less satisfactory in patients with significant preoperative truncal valve regurgitation. Some late complications related to deterioration of the earlier aortic homograft conduit may be avoided by use of a porcine valve Dacron conduit. The current operative mortality of 9%, and the well-being of 97% of surviving patients suggest the continued advisability of recommending operation for appropriate patients.     

Sensitive high-performance liquid chromatographic determination of cyclizine and its demethylated metabolite, norcyclizine, in biological fluids using coulometric detection

An accurate, sensitive, selective and reproducible high-performance liquid chromatographic method with coulometric detection for the determination of cyclizine and its inactive demethylated metabolite, norcyclizine, in biological fluids has been developed. The drugs were separated using a custom packed reversed-phase C18 analytical column and phosphate buffer (0.05 M, pH 3)-acetonitrile (7:3) as mobile phase. The dual electrode coulometric detector was operated in the "oxidative-screen" mode with the upstream electrode (detector 1) set at 0.55 V and the downstream electrode (detector 2) set at 0.90 V. Serum and urine samples were prepared for analysis by solid-phase extraction, followed by a simple phase-separation step. The limit of quantitation was 1 ng/ml for both cyclizine and norcyclizine in serum and urine.     

Effect of triiodothyronine administration in experimental myocardial injury

Twelve healthy pigs were subjected to a 20-min, period of regional myocardial ischemia by snaring the left anterior descending coronary artery (LAD) between its first and second diagonal branches. The resulting myocardial injury caused significant acute hemodynamic impairments. Cardiac index declined significantly during reperfusion interval and returned to preischemic level by postoperative day 7. Plasma total triiodothyronine (TT3), free triiodothyronine (FT3) and free fatty acid (FFA) decreased gradually and reached the nadir at 6 h after LAD occlusion. In contrast, plasma reverse triiodothyronine (rT3) increased progressively after LAD occlusion and reperfusion. To investigate the effect of T3 on ischemic myocardium, T3 (0.2 microgram/kg/dose; n = 5) or saline (placebo; n = 6) was administered immediately, 30 min, 60 min, 90 min, and 120 min after reperfusion. Plasma TT3 and FT3 increased dramatically after triiodothyronine supplement but declined to presichemic level at six h after LAD occlusion. The pigs treated with T3 demonstrated a rapid improvement in cardiac index over the reperfusion interval, whereas cardiac index in the placebo group remained depressed. Myocardial oxygen consumption estimated by rate pressure product showed no difference between placebo and T3-treated groups. Oxygen extraction as O2 saturation difference between aorta and coronary sinus was less in T3-treated group. Nine pigs (four in the T3-treated group and five in the placebo group) were subjected to euthanasia with hypertonic KCl solution on postoperative day 7. Myocardial infarct size determined by triphenyltetrazolium chloride (TTC) tissue enzyme staining technique was not significantly different between T3-treated and placebo groups. We concluded that this animal model is a useful model of myocardial injury simulating "euthyroid sick syndrome" as seen in patients with cardiopulmonary bypass, and T3 supplementation after reperfusion significantly enhanced postischemic left ventricular functional recovery but did not affect myocardial oxygen consumption and myocardial infarct size.     

Microfluidic transistors for analog microflows amplification and control

Two microfluidic transistors for analog flow control and amplification for lab-on-a-chip applications are presented. The transistors are based on the elastic membrane microchannel, where the flow in the microchannel between the substrate and the membrane is controlled by the pressure differences along the channel and across the membrane. Reduced-order models that capture the low-inertia dynamic behavior of the coupled fluid–structure interaction were developed to enable fast small-signal analysis of large circuits. The accuracy of the models is assessed by comparing to numerical simulations of the coupled fluid–structure interaction problem. Analog behavior (based on analytical modeling and numerical simulation) of the two devices is characterized in terms of dependence of the volume flow rate on the source–drain and gate–source pressure differences, analogous to the characterization of MOSFET operation. The characteristic curves are then used to extract the small-signal parameters (transconductance and intrinsic output resistance), characterizing the dynamic response to small time-varying pressures at the gate and/or drain. The characterization enabled identification of the various static and dynamic operation regimes of the devices, including the transistive regime where the device operates as amplifier, and the capacitive (positive and negative) regimes. Finally, the dual-membrane transistor is used to showcase its use as a diode and a common-source amplifier in the design of a micropump that, in turn, is used for mixing of two species using pulsating flows.