Free radical reaction products and antioxidant capacity in beating heart coronary artery surgery compared to conventional bypass.

Oxygen-derived free radicals are important agents of tissue injury during ischemia and reperfusion. The aim of this study was to investigate changes in protein and lipid oxidation and antioxidant status in beating heart coronary artery surgery and conventional bypass and to compare oxidative stress parameters between the two bypass methods. Serum lipid hydroperoxide, nitric oxide, protein carbonyl, nitrotyrosine, vitamin E, and ß-carotene levels and total antioxidant capacity were measured in blood of 30 patients undergoing beating heart coronary artery surgery (OPCAB, off-pump coronary artery bypass grafting) and 12 patients undergoing conventional bypass (CABG, on-pump coronary artery bypass grafting). In the OPCAB group, nitric oxide and nitrotyrosine levels decreased after reperfusion. Similarly, ß-carotene level and total antioxidant capacity also decreased after anesthesia and reperfusion. In the CABG group, nitric oxide and nitrotyrosine levels decreased after ischemia and reperfusion. However, protein carbonyl levels elevated after ischemia and reperfusion. Vitamin E, ß-carotene, and total antioxidant capacity decreased after ischemia and reperfusion. Significantly decreased nitration and impaired antioxidant status were seen after reperfusion in both groups. Moreover, elevated protein carbonyls were found in the CABG group. The off-pump procedure is associated with lower degree of oxidative stress than on-pump coronary surgery.

A MEMS-Based Power-Scalable Hearing Aid Analog Front End.

A dual-channel directional digital hearing aid front end using microelectromechanical-systems microphones, and an adaptive-power analog processing signal chain are presented. The analog front end consists of a double differential amplifier-based capacitance-to-voltage conversion circuit, 40-dB variable gain amplifier (VGA) and a power-scalable continuous time sigma delta analog-to-digital converter (ADC), with 68-dB signal-to-noise ratio dissipating 67 µ W from a 1.2-V supply. The MEMS microphones are fabricated using a standard surface micromachining technology. The VGA and power-scalable ADC are fabricated on a 0.25-µ m complementary metal-oxide semciconductor TSMC process.

A Compact and Low-Cost MEMS Loudspeaker for Digital Hearing Aids.

A microelectromechanical-systems (MEMS)-based electromagnetically actuated loudspeaker to reduce form factor, cost, and power consumption, and increase energy efficiency in hearing-aid applications is presented. The MEMS loudspeaker has multilayer copper coils, an NiFe soft magnet on a thin polyimide diaphragm, and an NdFeB permanent magnet on the perimeter. The coil impedance is measured at 1.5 Omega, and the resonant frequency of the diaphragm is located far from the audio frequency range. The device is driven by a power-scalable, 0.25-mum complementary metal-oxide semiconductor class-D SigmaDelta amplifier stage. The class-D amplifier is formed by a differential H-bridge driven by a single bit, pulse-density-modulated SigmaDelta bitstream at a 1.2-MHz clock rate. The fabricated MEMS loudspeaker generates more than 0.8-mum displacement, equivalent to 106-dB sound pressure level (SPL), with 0.13-mW power consumption. Driven by the SigmaDelta class-D amplifier, the MEMS loudspeaker achieves measured 65-dB total harmonic distortion (THD) with a measurement uncertainty of less than 10%. Energy-efficient and cost-effective advanced hearing aids would benefit from further miniaturization via MEMS technology. The results from this study appear very promising for developing a compact, mass-producible, low-power loudspeaker with sufficient sound generation for hearing-aid applications.

Urinary epidermal and insulin-like growth factor excretion in autistic children.

Growth factors have been implicated in the pathogenesis of autism. We have investigated daily urinary excretion of insulin-like growth factor-1 (IGF-1), epidermal growth factor, and insulin-like growth factor binding protein-3 in autistic children (n=34, age 2-5 years) and age-matched control children (n=29). The mean urinary IGF-1 level was lower in the autism group than the control group (p=0.03). Height was normal. These findings suggest altered IGF-1 metabolism in young autistic children. The cause-effect relationship should be examined by longitudinal studies and insulin-like growth factor provocation tests.

Coronary artery bypass grafting in the conscious patient without endotracheal general anesthesia.

BACKGROUND: Over the past several years, considerable experience has accumulated in performing coronary anastomoses on the beating heart, and various aspects of minimally invasive approaches have been simplified. In an attempt to further simplify and decrease the "invasiveness" of this procedure, performing this operation without endotracheal general anesthesia was deemed feasible in certain subsets of patients. METHODS: Between October 1998 and June 1999, 5 patients underwent coronary artery bypass grafting without endotracheal general anesthesia, using high thoracic epidural block to construct extension grafts with a short segment of radial artery, between the in situ left or right internal thoracic arteries and the left anterior descending (n = 4) or right coronary arteries (n = 1). There were 2 female and 3 male patients, with a mean age of 67.4 +/- 8.3 years. RESULTS: The perioperative course of the patients was uneventful. There was no perioperative morbidity or mortality. No patient was converted to general anesthesia or to conventional operation. Control angiograms revealed patent anastomoses in all patients. In 1 patient, spasm of the radial artery graft was observed that was relieved 3 weeks later spontaneously. Mean length of hospital stay was 2.2 +/- 0.4 days. All patients were symptom free and returned to normal daily life at the first postoperative month. CONCLUSIONS: Our initial experience confirms the feasibility of performing coronary bypass grafting in the conscious patient without endotracheal general anesthesia.

Minimally invasive mitral valve surgery: the subxiphoid approach.

BACKGROUND: This report describes mitral valve replacement using a unique subxiphoid approach with a lower ministernotomy and a skin crease incision and compares the operative and echocardiographic results to patients undergoing mitral valve replacements using previously described strategies. METHODS: Fifty-four patients underwent mitral valve replacement using a subxiphoid approach (group 1); 32 patients underwent mitral valve replacement, 11 patients underwent mitral valve replacement + tricuspid reconstruction, 2 patients underwent mitral valve replacement + tricuspid valve replacement, and 9 patients underwent mitral reconstruction. This group of patients was compared to 11 patients who underwent mitral valve replacement through a superior ministernotomy (group 2) and 29 patients who underwent mitral valve replacement with full median sternotomy (group 3, 22 mitral valve replacements, 2 mitral valve replacements + tricuspid reconstruction, 2 mitral reconstructions, and 3 mitral reconstructions + tricuspid reconstruction). RESULTS: There was no operative mortality in all groups. The operation lasted significantly longer in group 2 patients compared to group 1 and 3 patients (p < 0.01). Postoperative mediastinal drainage was significantly lower in groups 1 and 2 (p < 0.001). Pain assessment revealed no difference between the groups. Three patients in group 1 presented with pericardial effusion. Except for this complication, early postoperative echocardiographic findings of the patients were similar in all three groups. All patients were in New York Heart Association functional class I or II at the second postoperative month, irrespective of the surgical technique used. CONCLUSIONS: There was no prominent superiority of the ministernotomy approaches over the standard median sternotomy approach. However, the reliability of the subxiphoid approach is documented echocardiographically and any type of mitral replacement can be performed with this approach.