These patients appear to respond best to permanent quadripolar lead placement but long-term results do not appear to be independently affected by the method of test stimulation. Loss of benefit over time is not common.
Patients with pulmonary insufficiency due to scleroderma have long been considered suboptimal candidates for lung transplantation. This has been supported by small single-center experiences that did not reflect the entire U.S. experience. We sought to evaluate the outcome of patients with scleroderma who underwent lung transplantation. We conducted a retrospective review of 47 patients with scleroderma who underwent lung transplantation at 23 U.S. centers between 1987 and 2004 and were reported to the United Network for Organ Sharing. Women constituted 57% of the patients. The mean age was 46 years. Twenty-seven patients received single lung transplants (57%), and the remaining received double lung transplants. The mean cold ischemia time was 4.1 hours. There were 7 early deaths (< or =30 days) and 17 late deaths (> 30 days). The causes of early death were primary graft failure and a cardiac event in two patients each and bacterial infection and stroke in one patient each. Late mortality was due to infection in seven patients, respiratory failure in three, malignancy in two, and multisystem organ failure, rejection, pulmonary hypertension, and a cardiac event in one patient each. The causes of early and late death were not recorded for two patients. One patient received a second transplant owing to graft failure of the first. Twenty-three patients (49%) were alive at a mean follow-up of 24 months. The Kaplan-Meier 1- and 3-year survival rates were 67.6% and 45.9% respectively, which are not significantly different from those of 10,070 patients given transplants for other lung conditions during the same period (75.5% and 58.8% respectively, P = 0.25). Donor gender, recipient's age, and type of transplant did not affect survival. In carefully selected patients with scleroderma who have end-stage lung disease, lung transplantation is a valid life-saving therapeutic option. Available data suggest acceptable short-term morbidity and mortality and a long-term survival similar to that of patients given transplants for other lung conditions.
In this paper, we report on the development of an implantable pressure sensing system that is powered by mechanical vibrations in the audible acoustic frequency range. This technique significantly enhances interrogation range, alleviates the misalignment issues commonly encountered with inductive powering, and simplifies the external receiver circuitry. The interrogation scheme consists of two phases: a mechanical vibration phase and an electrical radiation phase. During the first phase, a piezoelectric cantilever acts as an acoustic receiver and charges a capacitor by converting sound vibration harmonics occurring at its resonant frequency into electrical power. In the subsequent electrical phase, when the cantilever is not vibrating, the stored electric charge is discharged across an LC tank whose inductor is pressure sensitive; hence, when the LC tank oscillates at its natural resonant frequency, it radiates a high-frequency signal that is detectable using an external receiver and its frequency corresponds to the measured pressure. The pressure sensitive inductor consists of a planar coil (single loop of wire) with a ferrite core whose distance to the coil varies with applied pressure. A prototype of the implantable pressure sensor is fabricated and tested, both in vitro and in vivo (swine bladder). A pressure sensitivity of 1 kHz/cm H2O is achieved with minimal misalignment sensitivity (26% drop at 90° misalignment between the implanted device and acoustic source; 60% drop at 90° misalignment between the implanted device and RF receiver coil).
Sacral neuromodulation has had a tremendous impact on the treatment of urinary incontinence and lower urinary tract symptoms for patients with neurologic conditions. This stimulation does not use real-time data from the body or input from the patient. Incorporating this is the goal of those pursuing a neuroprosthesis to enhance bladder function for these patients. Investigators have demonstrated the effectiveness of conditional (also called closed-loop) feedback in animal models as well as limited human studies. Dorsal genital nerve, pudendal nerve, S3 afferent nerve roots, S1 and S2 ganglia have all been used as targets for stimulation. Most of these have also been used as sources of afferent nerve information using sophisticated nerve electrode arrays and filtering algorithms to detect significant bladder events and even to estimate the fullness of the bladder. There are problems with afferent nerve sensing, however. Some of these include sensor migration and low signal to noise ratios. Implantable pressure sensors have also been investigated that have their own unique challenges, such as erosion and sensor drift. As technology improves, an intelligent neuroprosthesis with the ability to sense significant bladder events and stimulate as needed will evolve.
Purpose of ReviewSacral neuromodulation (SNM) is being used to treat lower urinary tract symptoms (LUTS) with growing popularity among clinicians in multiple specialties. As this therapy becomes more common in the USA and Europe, urologists will encounter more patients implanted with SNM generators.Recent FindingsOver time, it has recently been understood that up to 53% will develop pain at the implant site as reported by Groen et al. (J Urol 186:954, 2011) and 3–38% will lose effective stimulation as reported by Al-zahrani et al. (J Urol 185:981, 2011) and White et al. (Urology 73:731, 2009). There is a paucity of troubleshooting methodology in the literature, apart from revision surgery, to salvage the SNM generator. In fact, it has been suggested that one contemporary series’ failure rate is lower than some historic series because of the ability to reprogram devices as reported by Siegel et al. (J Urol 199:229, 2018). Standard algorithms for such reprogramming efforts are lacking in the literature and may salvage some patients otherwise destined for surgical revision or addition of multimodal therapy to achieve acceptable symptom control.SummaryIt is possible to troubleshoot and thereby salvage many SNM generators, saving patients from surgical revision in many cases and increasing the number of patients with persistent benefit from SNM. The algorithms presented in this manuscript represent a systematic strategy for reprogramming and troubleshooting SNM generators.
The kidney has both afferent (sensory) and efferent (sympathetic) nerves that can influence renal function. Renal innervation has been shown to play a role in the pathogenesis of many forms of hypertension. Hypertension and flank pain are common clinical manifestations of autosomal dominant (AD) polycystic kidney disease (PKD). We hypothesize that renal innervation contributes to the hypertension and progression of cystic change in rodent PKD. In the present study, the contribution of renal innervation to hypertension and progression of renal histopathology and dysfunction was assessed in male Han:SPRD-Cy/+ rats with ADPKD. At 4 weeks of age, male offspring from crosses of heterozygotes (Cy/+) were randomized into either 1) bilateral surgical renal denervation, 2) surgical sham denervation control, or 3) nonoperated control groups. A midline laparotomy was performed to allow the renal denervation (i.e., physical stripping of the nerves and painting the artery with phenol/alcohol). Blood pressure (tail cuff method), renal function (BUN) and histology were assessed at 8 weeks of age. Bilateral renal denervation reduced the cystic kidney size, cyst volume density, systolic blood pressure, and improved renal function (BUN) as compared with nonoperated controls. Operated control cystic rats had kidney weights, cyst volume densities, systolic blood pressures, and plasma BUN levels that were intermediate between those in the denervated animals and the nonoperated controls. The denervated group had a reduced systolic blood pressure compared with the operated control animals, indicating that the renal innervations was a major contributor to the hypertension in this model of ADPKD. Renal denervation was efficacious in reducing some pathology, including hypertension, renal enlargement, and cystic pathology. However, sham operation also affected the cystic disease but to a lesser extent. We hypothesize that the amelioration of hypertension in Cy/+ rats was due to the effects of renal denervation on the renin angiotensin system.
Monitoring bodily pressures provide valuable diagnostic and prognostic information. In particular, long-term measurement through implantable sensors is highly desirable in situations where percutaneous access can be complicated or dangerous (e.g., intracranial pressure in hydrocephalic patients). In spite of decades of progress in the fabrication of miniature solid-state pressure sensors, sensor drift has so far severely limited their application in implantable systems. In this paper, we report on a universal packaging technique for reducing the sensor drift. The described method isolates the pressure sensor from a major source of drift, i.e., contact with the aqueous surrounding environment, by encasing the sensor in a silicone-filled medical-grade polyurethane balloon. In-vitro soak tests for 100 days using commercial micromachined piezoresistive pressure sensors demonstrate a stable operation with the output remaining within 1.8 cmH2O (1.3 mmHg) of a reference pressure transducer. Under similar test conditions, a non-isolated sensor fluctuates between 10–20 cmH2O (7.4–14.7 mmHg) of the reference, without ever settling to a stable operation regime. Implantation in Ossabow pigs demonstrate the robustness of the package and its in-vivo efficacy in reducing the baseline drift.
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