Preoperative Ultrasonic Assessment of Thin Melanocytic Skin Lesions Using a 100-MHz Ultrasound Transducer: A Comparative Study

BACKGROUND It has been shown that tumor thickness (TT) of melanocytic skin lesions (MSL) of less than 1 mm vertical thickness assessed by 20 MHz are often incorrectly evaluated.
OBJECTIVE We aimed to evaluate the accuracy of 100-MHz ultrasound for the determination of TT of thin MSL, compared with conventional 20-MHz ultrasound and histologic findings.
METHODS Thirty-seven patients with 50 suspicious MSL, including tumor diameter up to 1 cm and maximum vertical TT of less than 1 mm, were recruited. The agreement between the histologically and ultrasographically measured TT was analyzed using Bland and Altman plots.
RESULTS Compared to histology, 20-MHz ultrasound (33.9 μm) as well as 100-MHz (16 μm) resulted in overestimation of TT that was twofold higher for 20-MHz ultrasound. The latter also revealed wider 95% limits of agreement (4.9 to 63 μm) than 100-MHz ultrasound (3.5 to 28.7 μm).
CONCLUSION Analysis of agreement clearly demonstrated that the performance of 100-MHz ultrasound is superior to conventional 20-MHz ultrasound, even though a relatively small positive bias was observed in 100-MHz ultrasound, indicating a systematic error. We consider 100-MHz ultrasound a useful tool for the noninvasive determination of TT of thin MSL in vivo.     

Influence of external cardiac pacing on cerebral oxygenation measured by near‐infrared spectroscopy in children after cardiac surgery

Background: The brain of children in the early period after repair of congenital heart defects with cardiopulmonary bypass (CPB) may be more vulnerable to hemodynamic changes because of impaired cerebral autoregulation. During postoperative testing of the external temporary safety pacer, we performed desynchronizing ventricular pacing (VVI) while monitoring cerebral oxygenation using near‐infrared spectroscopy (NIRS). Methods: We prospectively investigated 11 children (6 girls, 5 boys). Mean age was 6.1 months (±3.8 months) and mean weight: 5.3 kg (±1.5 kg). We performed measurements at four study steps: baseline I, VVI pacing, baseline II and atrial pacing (AOO) to exclude effects of higher heart rate. We continuously measured the effects on hemodynamic and respiratory parameters as well as on cerebral tissue oxygenation index (TOI). Hemoglobin difference (HbD) was calculated as a parameter for cerebral blood flow (CBF). Results: Ventricular pacing leads to a significant decrease in arterial blood pressure and central venous saturation accompanied by an immediate and significant decrease in TOI (63.3% ± 7.6% to 61.5% ± 8.4% [P < 0.05]) and HbD (0.51 ± 1.8 μmol·l⁻¹ to −2.9 ± 4.7 μmol·l⁻¹ [P < 0.05]). Conclusion: Cardiac desynchronization after CPB seems to reduce CBF and cerebral oxygenation in children.     

A New Mechanical Sensor for Detecting Body Activity and Posture, Suitable for Rate Responsive Pacing

In the past, thought about rate responsive pacing mainly focused on rate increase with exercise but did not consider that a rate increase with postural changes also is mandatory in order to prevent orthostatic reactions. A nightly decrease in pacemaker rate when the body is at rest and in a supine position is a further advantage for the patient's sleep and recovery. Therefore, we developed a sensor that could detect not only rest and body activity but also discriminate between a supine and an upright position. This sensor is a muiticontact tilt switch containing a small mercury ball, as shown in the left panel of the figure below. The principle of discrimination between rest and low and high body activity is realized by the movement of the mercury ball resulting from body motion, which causes openings and closures within the sensor as the ball touches the numerous sensor contacts. In the upright position, a distinct number of contacts at the bottom of the tilt switch are closed. In the supine position, there is no closure of the bottom contacts and a postural discrimination can he achieved. We studied 12 volunteers and 10 pacemaker patients with this new device both at rest and during physical exercise. The right panel of the figure illustrates that the contacts per second correlate to the increase of physical exercise, such as walking on the treadmill. Further studies with an external pacemaker containing a small sensor suitable to fit into the pacemaker are in preparation.     

A New Rate-Modulated Pacemaker System Optimized by Combination of Two Sensors

A new rate-modulated pacemaker system optimized by combination of two sensors is described. The parameter body activity and central venous blood temperature control the pacemaker rate. The specific characteristic of each parameter determines its role within the algorithm. While the motion sensor yields a fast reaction following the onset or a change of stress intensity, central venous blood temperature corresponds better to body metabolism. An indication of increased exercise from the motion sensor results in an accordingly rapid increase in the pacing rate. Unless this increased exercise is confirmed by an increase in central venous blood temperature within 2 or 3 minutes, the new motion level will be assumed to be the new baseline motion value and the pace rate will return to a basic pacing rate. Prolonged inappropriate responses are therefore avoided. Longer lasting exercise, fever and nonphysiological signals are recognized and handled safely. Exercise tests with five volunteers under various conditions showed pacing rate behavior that was close to normal.     

Erbium: YAG Laser-Assisted Preparation of a Combined Dermal/Full Thickness Sandwich Skin Graft

BACKGROUND: Skin grafting is a common procedure to close defects after tumor resection. However, delicate areas such as the heel or the sole of the foot can be closed with a specially designed graft as described in this article. OBJECTIVE: To describe a surgical technique by means of erbium:YAG laser-assisted preparation of a combined dermal/full-thickness sandwich skin graft that facilitates the closure of defects, especially at mechanically stressed anatomic sites. METHODS: Tumor defects on the sole of the foot of 28 patients were closed with a new dermal/full-thickness sandwich skin graft. To obtain this special graft, half of a full-thickness skin graft twice the size of the wound defect was deepithelialized with an erbium:YAG laser. After complete defatting of the transplant, the deepithelialized part was folded beneath the full-thickness part (upside down) resulting in a sandwich graft, enabling contact of the papillary dermis with the wound surface. Graft results were graded as excellent when more than 75%, good if 50-75%, fair if 25-50%, and poor if less than 25% of the transplant healed. RESULTS: Results were graded as excellent in 32%, good in 54%, fair in 11%, and poor in 3% of the patients. Total graft loss was experienced in 1 of 28 patients. Complications such as bulky margins or infection were encountered in 14% of the patients. CONCLUSION: The laser-assisted preparation of the combined dermal/full-thickness sandwich skin graft is a new technique that facilitates the closure of defects in delicate anatomic locations with high mechanical stress like the plantar sole.