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Biomedical subjects

D E Patterson

Publications and source records attributed to D E Patterson.

58 records · Page 4Linked to original sources

Percutaneous removal of kidney stones. Preliminary report.

We have performed percutaneous extractions of renal pelvic stones in 15 patients with the use of the Wolf percutaneous universal nephroscope. At one session, with the patient under general anesthesia, a percutaneous tract is dilated to 24 F, and the stone is immediately removed. Fifteen stones have been removed successfully by ultrasonic lithotripsy, basket retrieval, use of a forceps, or a combination of these techniques. Average operating time has been 1 hour and the mean hospitalization time 4 days. The advantages of this technique are that a skin incision of only 1 to 2 cm is required to remove the stone, hospital days are fewer than with open procedures, and postoperative morbidity is minimal. In selected situations, this method represents a significant advance over standard open surgical procedures for removal of renal pelvic stones.

Adolescent↗

Visualizing substructural fingerprints.

Substructural fingerprints have proven very useful for chemical library and diversity analysis, but their high dimensionality makes them poorly suited to principal components analysis and to standard nonlinear mapping methods. By using a combination of optimizable K-dissimilarity selection (OptiSim) and a modified stress function that suppresses effects of distances that fall beyond a characteristic horizon, it is possible to relax principal components analysis coordinates into more consistently meaningful projections from fingerprint space into two dimensions. The nonlinear maps so obtained are useful for characterizing combinatorial libraries, for comparing sublibraries, and for exploring the distribution of biological properties across structural space.

Combinatorial Chemistry Techniques↗

Prediction of stone composition from plain radiographs: a prospective study.

BACKGROUND AND OBJECTIVES: Stone composition, as reflected in radiographic appearance, is important to help choose between SWL and percutaneous/endoscopic procedures. Predicting a stone's composition accurately from a plain radiograph would be a useful tool in clinical decision-making. However, the ability of physicians to predict composition has not been adequately assessed. A prospective study was designed to quantify the accuracy of a panel of physicians who routinely deal with stones in classifying stone composition solely from radiographs. MATERIALS AND METHODS: A panel of six members was created to review 100 plain-film radiographs from patients with renal stones of known composition. The panel consisted of two urologists, two radiologists, and two nephrologists, all of whom have expertise in stone disease. If the composition guessed was at least 40% of the total stone composition, the response was deemed correct. RESULTS: Overall, there was an average 39% correct response score among the six panelists. When the stones were divided by size, 35% were <1 cm, and 65% were larger. The accuracy of chemical composition determination did not improve with greater stone size, nor was there a difference in accuracy for pure and mixed stones. The most frequently misclassified stone was calcium phosphate, with only 14% being correctly diagnosed. CONCLUSIONS: With a random sampling of plain radiographs, a panel of physicians specializing in stone disease correctly diagnosed the composition of renal calculi less than half of the time without being given clinical information.

Calcium Oxalate↗

Economic considerations for aortic surgery: retroperitoneal approach--is it worth it?

BACKGROUND: Planned reductions in reimbursement for all forms of vascular surgery dictate a need for the development of more cost efficient, yet quality oriented, treatment programs. We are faced with an increasingly older patient population with multiple comorbidities. In this environment it will become extremely difficult to accomplish aortic surgery in a way which will be profitable for our hospitals. More than 100,000 aortic surgeries are performed annually in the United States. Previous reports suggest that earlier hospital discharges and reduced postoperative complications occur when a retroperitoneal approach is used for aortic surgery. Other publications refute this concept. In an effort to determine the most cost efficient method for aortic surgery in our institution, while maintaining high standards of care and outcome, we compared the retroperitoneal approach to the conventional transperitoneal aortic operation. PATIENTS AND METHODS: Between December 1995 and April 1998, 120 patients underwent aortic surgery by either the transperitoneal (n = 60) or retroperitoneal approach (n = 60). All patients were enrolled prospectively in a vascular registry and retrospectively reviewed. Patients were randomly assigned to one of three vascular surgeons. A clinical pathway for elective aortic surgery was developed and applied to both groups. Patients were evaluated with respect to demographics, comorbidities, preoperative risk stratification, conduct of the operative procedure, length of stay, complications, cost, clinical outcomes and patient satisfaction. The indications for aortic surgery were similar in both groups--64% for aneurysm disease and 36% for occlusive disease. Both symptomatic and asymptomatic aneurysms were included and size ranged from 4.4 cm to 14 cm. All aortic reconstructions were done in the standard manner using knitted Dacron velour prostheses in either the aortic tube, bi-iliac or bi-femoral configuration. Statistical analysis of means and medians was accomplished using the Wilcoxin Rank-sum test and percentages were compared using Fisher's Exact test. P values less than 0.05 indicate statistical significance. RESULTS: There were no statistically significant differences in patient demographics. The incidence of atherosclerotic coronary artery disease, obstructive pulmonary disease, diabetes, hyperlipidemia, tobacco abuse, distal lower extremity occlusive disease and the results of chemical myocardial stress evaluations were similar in both groups. Comorbidities of preexisting renal insufficiency/failure and morbid obesity were increased in the retroperitoneal group. Five patients in the retroperitoneal group represented redo aortic surgery and there were no redo procedures in the transperitoneal group. Length of operative procedures and blood replacement requirements for both groups were similar. The transperitoneal group required 2-3 liters more intraoperative intravenous (i.v.) crystalloid than the retroperitoneal group (p < 0.0001). Statistically significant reductions in ICU days, postoperative ileus and total lengths of stay were observed in the retroperitoneal group (p < 0.0001). This resulted in substantial reductions in hospital costs for the retroperitoneal group (p < 0.01). Postoperative complications were similar for both groups except for statistically significant increases in pulmonary edema (p < 0.01) and pneumonia (p < 0.001) in the transperitoneal group. Cardiac arrhythmias, primarily atrial dysrhythmias, were more frequent in the transperitoneal group but this failed to reach statistical significance (p < 0.16). Combined thirty day mortality was 0.9%. Time of recovery to full activity and patient satisfaction substantially favored the retroperitoneal group. CONCLUSION: Our clinical pathway and algorithm for aortic surgery was easily followed by those patients in the retroperitoneal approach group and resulted in decreases in ICU time, postoperative ileus, volume of intraoperative crystalloid and total length of stay. The patients in the transperitoneal group often failed to progress appropriately on the pathway. Reduced hospital costs associated with aortic surgery using the retroperitoneal approach has increased the profitability for this surgery in our institution by an average of $4000 per case and has increased the value (quality/cost) of this surgery to our patients and our institution. This was accomplished in an academic environment with surgical residency training where cost containment has historically been difficult.

Aorta↗