Search PubMed⌕ Search

Biomedical subjects

R Hartz

Publications and source records attributed to R Hartz.

8 recordsLinked to original sources
PubMed1991

Endoscopic thoracic sympathectomy: evaluation of pulsatile laser, non-pulsatile laser, and radiofrequency-generated thermocoagulation.

We describe a modified technique for percutaneous denervation of the thoracic sympathetic chain by laser to treat selected cases of sympathetic causalgia of the upper extremities. The technique involves transpleural ablation with laser under thoracoscopic guidance through the second or third intercostal space-anterior axillary line. We also compare four different modalities of endoscopic denervation: A xenon chloride excimer laser (308 nm, 35 mJ/pulse, 20 pulses/sec, 2.2 mm catheter tip), CO2 laser (14 W, CW, 2 mm spot size), Nd:YAG laser (88 W, CW, 3 mm spot size), and radiofrequency-generated thermocoagulation (3 W, CW, 2.1 mm catheter tip) by performing bilateral thoracic sympathectomy on 12 mongrel dogs (three dogs each). Criteria analyzed included duration of exposure, power density, total energy output, laser penetration and spread, gross morphology, and scanning electron microscopy (SEM) of the destroyed neural tissue. Total ablation of the inferior segment of the stellate ganglion and the T1-T2 nerve roots by excimer laser required 83 +/1 1 Joules over an exposure period of 118 seconds. Ablation by CO2 and Nd:YAG laser required 153 +/- 13 Joules and 554 +/- 47 Joules delivered over 11 and 6 seconds respectively. In contrast, ablation of the same volume of nerve tissue by RF required 810 +/- 50 Joules over 270 seconds. SEM evaluation revealed that excimer and CO2 laser lesions were narrower in configuration compared to RF and Nd:YAG lesions which showed more lateral spread. The actual depth of penetration per 1 second exposure was similar for Excimer and CO2 (1.5 mm) and RF (1.3 mm), but deeper for Nd:YAG (3 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Clinical experience with portable cardiopulmonary bypass in cardiac arrest patients.

To evaluate the use of portable cardiopulmonary bypass as a resuscitative tool and its impact on long-term survival of patients in cardiac arrest, we reviewed the results of 32 consecutive patients resuscitated by cardiopulmonary bypass for cardiac arrest or severe hemodynamic compromise at Northwestern Memorial Hospital over a 2-year period. Overall survival was 12.5%. Only 1 (3.4%) of the 29 patients who had cardiac arrest survived and left the hospital. All 3 patients who had severe hemodynamic compromise but not cardiac arrest were long-term survivors. Our study suggests that portable cardiopulmonary support systems used as a resuscitative tool do not prolong the survival of most cardiac arrest patients but may be useful for patients with shock due to mechanical causes and for those with profound hemodynamic compromise due to ischemia or myocardial infarction. Portable heart-lung machines can provide patients with excellent hemodynamic support; however, neurological or cardiac recovery is unlikely once cardiac arrest occurs.

Cardiopulmonary Bypass↗
PubMed1985

Prophylaxis of supraventricular tachyarrhythmia after coronary bypass surgery with oral verapamil: a randomized, double-blind trial.

This study investigated the efficacy of oral administration of verapamil, started 24 hours after coronary artery bypass grafting (CABG), in reducing the incidence of postoperative supraventricular tachyarrhythmia (SVT). Two hundred patients were randomly assigned in a double-blind fashion to receive a one-week course of either a placebo or 80 mg of verapamil every 6 hours. Overall, SVT developed in 23 control and 14 verapamil-treated patients, a 39% reduction in incidence (p less than 0.10). Of the patients who received at least four doses and continued to receive the study drug, 17 in the control and 7 in the verapamil group experienced SVT, a 53% decrease in incidence (p less than 0.06). Atrial fibrillation constituted 34 of the 37 SVT episodes and was associated with a slower ventricular response in the group given verapamil (115 +/- 8 versus 156 +/- 4 beats per minute; p less than 0.001). No evidence was found linking postoperative SVT with the withdrawal of beta-blocking drugs. Adverse effects required that 20 patients in the verapamil and 6 in the placebo group be removed from the study. Hypotension or pulmonary edema or both developed in 13 of the patients receiving verapamil, but in only 1 of the control patients (p less than 0.001). We conclude that although verapamil has potential merit for the prophylaxis of SVT after CABG, its use in this setting is associated with a high incidence of unacceptable hemodynamic side effects.

Administration, Oral↗
PubMed1983

Image improvement and design optimization of the time-of-flight PET.

Positron emission tomography (PET) with the added time-of-flight information has been shown to provide a better reconstructed image over conventional positron tomography. This improvement depends on the size of the object being imaged, the intrinsic resolution of the detector, and the time-of-flight resolution. Moreover, the signal-to-noise ratio of a PET image is related not only to the total number of counts in the image but also the event-locating uncertainties, the reconstruction filter function, and the recovered resolution in the image. This study provides a physical explanation for, and description of, the improvement in signal-to-noise ratio of a reconstructed image as a function of the crucial design parameters: time-of-flight timing resolution, intrinsic detector resolution, object size, and reconstructed image resolution.

Electricity↗
PubMed1980

Mesenteric tumefactions.

Mesenteric tumefactions comprise a group of non-neoplastic conditions that present as an intra-abdominal mass. Symptoms vary from none to obstruction of the gastrointestinal tract. Histologic examination reveals dystrophy, fibrosis, or inflammation of the mesenteric fat. Despite a large number of descriptive terms currently in use, this study suggests that all these lesions are part of a single clinical and histologic continuum.

Adipose Tissue↗