Increasing the efficiency of Monte Carlo cohort simulations with variance reduction techniques.

The authors discuss techniques for Monte Carlo (MC) cohort simulations that reduce the number of simulation replications required to achieve a given degree of precision for various output measures. Known as variance reduction techniques, they are often used in industrial engineering and operations research models, but they are seldom used in medical models. However, most MC cohort simulations are well suited to the implementation of these techniques. The authors discuss the cost of implementation versus the benefit of reduced replications.     

NA:YAG激光虹膜切除术治疗闭角型青光眼201例临床观察

目的评价NA：YAG激光虹膜切除术治疗原发性闭角型青光眼和葡萄膜炎继发青光眼的临床疗效。方法回顾分析192例219眼原发性闭角型青光眼和9例葡萄膜炎继发青光眼，接受NA：YAG激光虹膜切除术后的临床效果，随诊16—46月。结果激光切孔一次成功205眼（占89e），激光能量在11—17．1mJ，67％病例在22—84Mj，击射次数2-33次。葡萄膜炎继发青光眼9眼均二次激光后虹膜孔通畅。95．61％术后眼压正常，视野无变化，术后早期一过性眼压升高占34％，术中出血占36％，房角色素增加占47％，1例术后28月接受小量切除术，8例术后需配合使用降眼压药物控制眼压。结论NA：YAG激光虹膜切除术是一种治疗闭角型青光眼的安全有效的方法。术前掌握适应症，把握手术时机，充分的术前准备是手术成功的关键。     

肾移植术后并发尿路上皮肿瘤的临床分析

目的 分析肾移植患者并发尿路上皮肿瘤的特点，探讨其诊治方法。方法 自1998～2003年肾移植患者1293例，术后发生尿路上皮恶性肿瘤21例（1．6％）。男4例，女17例。17例原发病为慢性问质性肾炎。发生尿路上皮肿瘤距肾移植6～62个月，平均26个月。其中膀胱癌6例，单侧肾盂或输尿管癌6例，单侧肾盂或输尿管、膀胱癌8例，双侧肾盂输尿管癌1例。10例上尿路肿瘤发生部位与移植肾同侧，4例发生于移植肾对侧。临床症状以无痛性肉服血尿和反复泌尿系感染为主。19例行手术治疗，术后所有患者免疫抑制剂用量减少1／3并辅以局部灌注化疗。结果 2例行姑息性治疗的晚期肿瘤患者分别于发现肿瘤5、8个月死亡。余19例现已随访2～5年。13例肿瘤复发，复发部位为膀胱或对侧原。肾、输尿管。所有患者在免疫抑制剂减量期间均未出现急性排斥。2例因切除移植肾恢复透析，17例肾功能正常。结论 慢性间质性。肾炎导致。肾功能衰竭的。肾移植患者和女性肾移植患者易发生移植后尿路上皮肿瘤；移植肾同侧上尿路较对侧好发肿瘤；对移植肾对侧为首发的上尿路发生肿瘤者可预防性行双侧上尿路根治性切除。     

Novel explant model to study mechanotransduction and cell-cell communication.

To understand in situ behavior of osteocytes, we characterized a model of osteocytes in their native bone matrix and demonstrated real-time biologic activity of osteocytes while bending the bone matrix. Using 43 male Sprague-Dawley rats, dumbbell-shaped explants were harvested from stainless steel femoral implants after 6-12 weeks and incubated in culture medium or fixed. Sixteen specimens were used to determine bone volume density (BV/TV), volumetric bone mineral density (BMD) and histology for different implantation periods. Osteocyte viability was evaluated by L-lactate dehydrogenase (LDH) activity in 12 cultured explants. Confocal microscopy was used to assess tracer diffusion in three explants and changes in osteocyte pH of a mechanically loaded explant. From 6 to 12 weeks, explant BV/TV and volumetric BMD trended up 92.5% and 101%, respectively. They were significantly and highly correlated. Tissues were uniformly intramembranous and all bone cell types were present. Explants maintained LDH activity through culture day 8. Diffusion at 200 microM was limited to 1,209 Da. Explants appeared capable of reproducing complex bone biology. This model may be useful in understanding osteocyte mechanotransduction in the context of a physiologically relevant bone matrix.     

Proliferating pilomatricoma

We report on 9 patients with pilomatricomas that showed unusual histopathologic features. Our patients were mainly elderly individuals (age range 42 to 88 years; mean age 70.1 years) who presented solitary cutaneous nodules situated on the head and neck (7 neoplasms), upper arm (1 neoplasm), and back (1 neoplasm). All the lesions were treated by simple excision. Follow-up data available in 7 of the 9 patients (mean follow-up, 17 months) revealed local recurrences in 1 patient whose lesion recurred 3 times. No lymph node involvement or distant metastases were recorded in any of our cases. Histopathologically, most neoplasms were characterized by a relatively large lesion in the clermis that in some cases showed extension to the subcutis. Each lesion was predominantly composed of a lobular proliferation of basaloid cells in association with adjacent focal areas containing eosinophilic, cornified material with shadow cells. In some cases, relatively large areas of shadow cells were present, whereas, in others only small foci of shadows cells were observed. Cytomorphologically, the basaloid cells showed features of matrical and supramatrical cells of a normal hair follicle and exhibited variable nuclear atypia and mitotic figures. The overall architectural pattern of the neoplasms was different from that of large fully developed stereotypical pilomatricomas that maintain a cystic character with basaloid cells predominantly aligned at the periphery. Based on the histopathologic findings, namely the presence of a large, lobular proliferation of basaloid cells in association with small to large foci of shadow cells, we interpreted these neoplasms to be a distinctive proliferative variant of pilomatricoma and propose the designation "proliferating pilomatricoma." Proliferating pilomatricomas should be differentiated from the recently described matricoma, basal-cell carcinoma with matrical differentiation, and matrical carcinoma (pilomatrical carcinoma).     

Removal of surface bacteria by irrigation

We examined the efficacy of various irrigation solutions delivered through a power irrigator to remove bacteria from three different surfaces. Titanium, stainless-steel, and cortical bone surfaces were coated with three different bacterial species: Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus epidermidis. They were then irrigated with 1 L of fluid delivered by jet lavage. The fluids tested were normal saline and solutions of bacitracin, neomycin, and soap. One set of specimens was not irrigated, as a control. After irrigation, the specimens were sonicated to remove residual bacteria, and the sonicate was quantitatively cultured to allow evaluation of the amount of residual bacteria on the surface. The results showed that removal of bacteria reflects an interaction between bacterial species, surface characteristics, and irrigation solution. Fewer bacteria were present in all the irrigation groups than in the control. Soap solution was as good as or better than any other solution at removing all three types of bacteria from all three surfaces, although not all of the pairwise comparisons were statistically significant. There was a significant advantage to soap solution over antibiotic irrigant or saline alone in removing Staphylococcus epidermidis from metallic surfaces. The use of a soap solution for irrigation seems to improve the removal of some bacteria from some surfaces in this experimental model and may represent a better type of irrigation additive.     

Remifentanil for use during conscious sedation in outpatient oral surgery.

PURPOSE: Remifentanil is a new, short-acting opioid that is similar pharmacodynamically to currently available opioids but differs in its pharmacokinetics. In the present study, we compared the use of remifentanil with the use of meperidine during intravenous conscious sedation for third molar surgery. PATIENTS AND METHODS: Forty patients who were scheduled for the removal of impacted third molars were randomly assigned to undergo 1 of 2 intravenous conscious sedation techniques. For both groups, 50:50 nitrous oxide oxygen were administered via nasal hood, and midazolam was titrated to Verril's sign. Twenty patients each then received either remifentanil 0.05 microgram/kg/min or meperidine 50 mg. Both patients and surgeons were blinded to the narcotic that was used. Blood pressure, heart rate, and oxygen saturation were determined before sedation and every 5 minutes during surgery. Recovery was measured using serial Trieger tests every 5 minutes after surgery. Patient and surgeon satisfaction of the quality of sedation was measured with a visual analog scale. RESULTS: Peak heart rate (91 beats/min for remifentanil vs 107 beats/min for meperidine, P <.01) and peak systolic blood pressure (131 mm Hg for remifentanil vs. 142 mm Hg for meperidine, P <.05) were significantly lower for the remifentanil group. Although there was a trend toward increased surgeon satisfaction with remifentanil (86 of 100 with remifentanil vs. 73 of 100 with meperidine), it was not found to be statistically significant. Likewise, other physiologic parameters were not found to be statistically significant. CONCLUSIONS: The lower peak heart rate and systolic blood pressure levels indicate that remifentanil may allow for less fluctuation in cardiovascular parameters. This could prove beneficial in patients with cardiovascular compromise.     

散结消肿贴中大黄重楼提取工艺优选研究

目的：优选散结消肿贴中大黄、重楼的渗漉提取工艺。方法：以总固体物得率和总蒽醌得率为指标，用正交实验优选。结果：工艺中影响最大的因素是乙醇浓度，其次是乙醇用量，浸泡时间影响较小。最佳工艺条件为乙醇浓度65％，乙醇用量8倍量。浸泡时间24h。结论：渗漉法操作简单，成份破坏少，用优选所得条件进行提取，总蒽醌和总固体物得率均较高，优选结果可用于散结消肿贴中大黄、重楼的提取。