Biomedical subjects

David M Wilhelm

Publications and source records attributed to David M Wilhelm.

4 recordsLinked to original sources

PubMed2004

Assessment of basic human performance resources predicts the performance of virtual ureterorenoscopy.

PURPOSE: Regardless of training, innate ability may influence the acquisition of endoscopic skills. Until recently objective methods to assess innate ability have not been available. We compared objective measures of human basic performance resources (BPRs) using nonlinear causal resource analysis (NCRA) and expert rated endoscopic performance of medical students on a virtual reality (VR) simulator. MATERIALS AND METHODS: BPRs were measured in 18 medical students (group 1) using 13 validated tests. BPR results were compared to the results of ureteroscopic skills assessment on the VR simulator. An NCRA model was devised to predict performance based on BPRs and the limiting performance resource (LPR). The same BPRs were measured in a second group of 14 medical students (group 2). Using the model created from group 1 performance of VR ureterorenoscopy was predicted based on LPR for each student in group 2. Predicted performance was compared to rated performance. RESULTS: The average difference in score between 2 expert raters was 7.2%. The average difference in predicted score based on the NCRA model and rated score was only 8.0%. In 9 of the 14 group 2 subjects (63%) the performance prediction by NCRA was in excellent agreement (+/-10%) with the expert rating on the VR simulation. NCRA over predicted performance in 2 subjects (14%) and under predicted performance in 3 (21%). CONCLUSIONS: Objective prediction of ureteroscopic performance in the VR environment using LPRs (measures of innate ability) for each subject is possible and practical using new measurement and modeling methods. The selection of surgical candidates, training and the educational curriculum could be impacted.

Clinical Competence↗

PubMed2003

Infrared thermography and thermocouple mapping of radiofrequency renal ablation to assess treatment adequacy and ablation margins.

OBJECTIVES: The primary disadvantage of renal tumor RF ablation is the inability to monitor the intraoperative propagation of the RF lesion with real-time imaging. We sought to assess whether adequately lethal temperatures are obtained at the margins of the intended ablation zone using laparoscopic thermography to monitor radiofrequency (RF) lesions in real time, thermocouple measurements, and histopathologic evaluation. METHODS: Renal RF lesions were created under direct laparoscopic vision in the upper (1 cm diameter) and lower (2 cm) poles of the right kidney in 5 female pigs. The RF lesions were produced with the RITA generator and probe, set at 105 degrees C for 5-minute ablations. During RF treatment, a laparoscopic infrared (IR) camera measured the surface parenchymal temperatures, as did multiple thermocouples. The pigs were then either immediately killed (n = 3) or allowed to live for 2 weeks (n = 2). The kidneys were removed to correlate the temperature measurements with histologic analysis of the ablated lesion. RESULTS: Using a threshold temperature of greater than 70 degrees C for visual "temperature" color change, the IR camera identified the region of pathologic necrosis of the renal parenchyma during RF ablation. Thermocouple measurements demonstrated that the temperatures at the intended ablation radius reached 77.5 degrees C at the renal surface and 83.7 degrees C centrally, and temperatures 5 mm beyond the set radius reached 52.6 degrees C at the surface and 47.7 degrees C centrally. The average diameter of the gross lesion on the surface of the kidney measured 17.1 mm and 22.4 mm for 1-cm and 2-cm ablations, respectively. These surface measurements correlated with an average diameter of 16.1 mm and 15.9 mm (1-cm and 2-cm ablations, respectively) as measured with the IR camera. All cells within these ablation zones were nonviable by nicotinamide adenine dinucleotide diaphorase analysis. The average depth of the lesions measured 19 mm (1-cm ablation) and 25 mm (2-cm ablation) on gross histologic examination. CONCLUSIONS: The laparoscopic IR camera is able to monitor the surface renal temperatures during RF treatment. Thermocouple measurements during RF ablation confirmed the thermographic findings and demonstrated that lethal temperatures at the margin of the intended treatment zone are routinely obtained and that a rapid decline in temperature occurs beyond the predicted ablation margin.

Animals↗

PubMed2003

Feasibility of laparoscopic partial nephrectomy using pledgeted compression sutures for hemostasis.

PURPOSE: To develop a technique for laparoscopic partial nephrectomy (LPN) without the use of hilar occlusion that allows large renal resection and excellent hemostasis. MATERIALS AND METHODS: Five female domestic pigs underwent right laparoscopic transperitoneal lower-pole partial nephrectomy after placement of pledgeted parenchymal compression sutures tied intracorporeally to induce regional renal hypoperfusion. Postoperatively, serial serum creatinine measurements were obtained to monitor renal function. The pigs were allowed to recover and 2 weeks later underwent an identical procedure on the left side. The animals were sacrificed after the second procedure, and both renal units were removed for ex vivo retrograde urograms and histologic analysis. RESULTS: The median operative time was 154.5 minutes (range 110-305 minutes), and the median blood loss was 137.5 mL (range 100-300 mL). On average, 35% (range 31%-36.8%) of the kidney was resected. All cases required use of adjunctive hemostatic clips to control bleeding from central vessels. All animals survived 2 weeks and had no evidence of urinary extravasation clinically or on ex vivo retrograde urograms. CONCLUSIONS: In the porcine model, LPN with placement of pledgeted sutures allows resection of large renal segments, although technical refinements are required to improve hemostasis. Currently, the need for adjunctive hemostatic measures limits the initial clinical application of this technique to small, exophytic tumors.

Animals↗

PubMed2002

Assessment of basic endoscopic performance using a virtual reality simulator.

BACKGROUND: The objective of this study was to evaluate the effect of supervised training using a state-of-the-art virtual reality (VR) genitourinary endoscopy simulator on the basic endoscopic skills of novice endoscopists. STUDY DESIGN: We evaluated 21 medical students performing an initial VR case scenario (pretest) requiring rigid cystoscopy, flexible ureteroscopy with laser lithotripsy, and basket retrieval of a proximal ureteral stone. All students were evaluated with objective parameters assessed by the VR simulator and by two experienced evaluators using a global rating scale. Students were then randomized to a control group receiving no further training or a training group, which received five supervised training sessions using the VR simulator. All students were then evaluated again in the same manner using the same case scenario (posttest). RESULTS: Comparing the results of pre- and posttests, no major differences were demonstrated for any variable in the control group. In the trained group, posttest results revealed statistically significant improvement from baseline in the following parameters: total procedure time (p = 0.002), time to introduce a ureteral guidewire (p = 0.039), self-evaluation (p < 0.001), and evaluator assessment (p < 0.001). Comparing the posttest results of the control and trained arms, we found significantly better posttest scores in the trained group for the following parameters: ability to perform the task (p = 0.035), overall performance (p = 0.004), and total evaluator score (p < or = 0.001). CONCLUSIONS: Students trained on the VR simulator demonstrated statistically significant improvement on repeat testing, but the control group showed no improvement. Endourologic training using VR simulation facilitates performance of basic endourologic tasks and might translate into better performance in the operating room.

Adult↗