Modeling the Impact of Interhospital Transfer Network Design on Stroke Outcomes in a Large City.

BACKGROUND AND PURPOSE: We sought to model the effects of interhospital transfer network design on endovascular therapy eligibility and clinical outcomes of stroke because of large-vessel occlusion for the residents of a large city. METHODS: We modeled 3 transfer network designs for New York City. In model A, patients were transferred from spoke hospitals to the closest hub hospitals with endovascular capabilities irrespective of hospital affiliation. In model B, which was considered the base case, patients were transferred to the closest affiliated hub hospitals. In model C, patients were transferred to the closest affiliated hospitals, and transfer times were adjusted to reflect full implementation of streamlined transfer protocols. Using Monte Carlo methods, we simulated the distributions of endovascular therapy eligibility and good functional outcomes (modified Rankin Scale score, 0-2) in these models. RESULTS: In our models, 200 patients (interquartile range [IQR], 168-227) with a stroke amenable to endovascular therapy present to New York City spoke hospitals each year. Transferring patients to the closest hub hospital irrespective of affiliation (model A) resulted in 4 (IQR, 1-9) additional patients being eligible for endovascular therapy and an additional 1 (IQR, 0-2) patient achieving functional independence. Transferring patients only to affiliated hospitals while simulating full implementation of streamlined transfer protocols (model C) resulted in 17 (IQR, 3-41) additional patients being eligible for endovascular therapy and 3 (IQR, 1-8) additional patients achieving functional independence. CONCLUSIONS: Optimizing acute stroke transfer networks resulted in clinically small changes in population-level stroke outcomes in a dense, urban area.

Validation of the International Classification of Diseases, Tenth Revision Code for the National Institutes of Health Stroke Scale Score.

BACKGROUND: Administrative data can be useful for stroke research but have historically lacked data on stroke severity. Hospitals increasingly report the National Institutes of Health Stroke Scale (NIHSS) score using an International Classification of Diseases, Tenth Revision (ICD-10) diagnosis code, but this code's validity remains unclear. METHODS: We examined the concordance of ICD-10 NIHSS scores versus NIHSS scores recorded in CAESAR (Cornell Acute Stroke Academic Registry). We included all patients with acute ischemic stroke from October 1, 2015, when US hospitals transitioned to ICD-10, through 2018, the latest year in our registry. The NIHSS score (range, 0-42) recorded in our registry served as the reference gold standard. ICD-10 NIHSS scores were derived from hospital discharge diagnosis code R29.7xx, with the latter 2 digits representing the NIHSS score. Multiple logistic regression was used to explore factors associated with availability of ICD-10 NIHSS scores. We used ANOVA to examine the proportion of variation (R2) in the true (registry) NIHSS score that was explained by the ICD-10 NIHSS score. RESULTS: Among 1357 patients, 395 (29.1%) had an ICD-10 NIHSS score recorded. This proportion increased from 0% in 2015 to 46.5% in 2018. In a logistic regression model, only higher registry NIHSS score (odds ratio per point, 1.05 [95% CI, 1.03-1.07]) and cardioembolic stroke (odds ratio, 1.4 [95% CI, 1.0-2.0]) were associated with availability of the ICD-10 NIHSS score. In an ANOVA model, the ICD-10 NIHSS score explained almost all the variation in the registry NIHSS score (R2=0.88). Fewer than 10% of patients had a large discordance (≥4 points) between their ICD-10 and registry NIHSS scores. CONCLUSIONS: When present, ICD-10 codes representing NIHSS scores had excellent agreement with NIHSS scores recorded in our stroke registry. However, ICD-10 NIHSS scores were often missing, especially in less severe strokes, limiting the reliability of these codes for risk adjustment.

Novel iron oxide microparticles used to render stone fragments paramagnetic: assessment of toxicity in a murine model.

PURPOSE: We developed novel peptide coated iron oxide supraparamagnetic microparticles that bind to calcium stones, allowing for extraction of these stones with magnetic tools. Urothelial and fibroblast cell lines show minimal to no toxicity when exposed to the particles. Before clinical evaluation, assessment of the in vivo systemic toxicity of the microparticles was required. This was studied in a murine model. MATERIALS AND METHODS: A total of 64 mice were exposed to different concentrations of microparticles (0.5, 1 or 5 mg/dl) intravesically or intravenously via the tail vein. Mice were sacrificed at different intervals (days 1, 3, 28 and 84). Representative samples from the brain, lung, heart, kidney and liver were evaluated histologically at each time point. The tissue distribution pattern of the particles and any degree of inflammation was noted by a clinical pathologist. Liver function tests were also performed at similar intervals. RESULTS: All mice survived until the assigned end point and appeared healthy after exposure to microparticles. In the bladder installation group no particles were seen in any organ regardless of the particle concentration instilled. In the intravenous instillation group there was tissue distribution in the liver and to a lesser extent in the lung. There was mild inflammation in the liver and lung, which was dose dependent. CONCLUSIONS: Novel iron oxide supraparamagnetic microparticles used to render stone fragments paramagnetic in the urinary collecting system did not appear to cross intact urothelial membranes. When introduced systemically, they led to minimal inflammatory changes, predominantly in the liver and lung. Additional long-term studies are required.

Importance of cosmesis to patients undergoing renal surgery: a comparison of laparoendoscopic single-site (LESS), laparoscopic and open surgery.

UNLABELLED: Study Type - Therapy (case series). Level of Evidence 4. What's known on the subject? and What does the study add? Studies in other surgical populations have found that scarring is a relatively unimportant preoperative patient consideration when compared with surgical cure and safety, but that younger age was a significant factor influencing preference for 'scarless' surgery. The present study corroborates the findings of previous series, among patients who were contemplating kidney surgery. OBJECTIVE: • To evaluate patient attitudes towards cosmesis relative to other considerations, before and after undergoing laparoendoscopic single-site surgery (LESS) vs laparoscopic/robot-assisted vs open kidney surgery. METHODS: • Participants were provided with a survey querying demographic information, surgical history and importance of scarring relative to other surgical outcomes and considerations. • The relative importance of each outcome was recorded on a nine-level ranking scale, ranging from 1 (most important) to 9 (least important). • The median scores for each outcome were compared before and after surgery using the Wilcoxon signed-rank test, and by surgical approach using the Kruskal-Wallis test. • The importance of scarring was further analysed according to age (≤ 50 vs >50 years), surgical indication (oncological vs non-oncological), gender, and proportion of patients who had undergone previous abdominal surgery. RESULTS: • A total of 90 patients completed surveys before surgery, of whom 65 (72.2%) also completed surveys after surgery. • 'Surgeon reputation' and 'no complications' were the most important considerations before surgery (median scores 2 and 3, respectively) and after surgery (median scores of 2 for both). • 'Size/number of scars' was the least important consideration before surgery (median score 8) and the second least important consideration after surgery (median score 7). • The median score for 'size/number of scars' was significantly higher for the LESS cohort before surgery (laparoscopic/robot-assisted vs LESS vs open surgery: 8.5 vs 6 vs 9; P = 0.003), but was nonsignificant after surgery (laparoscopic/robotic vs LESS vs open surgery: 7 vs 6.5 vs 7.5; P = 0.83). • The median score for 'size/number of scars' before surgery was significantly higher for younger patients (P = 0.05) and those with non-oncological surgical indications (P < 0.001), but there was no significant difference in this outcome for these sub-groups after surgery. CONCLUSIONS: • For most patients contemplating urological surgery, cosmesis is of less concern than surgeon reputation and avoidance of surgical complications. • Cosmesis may be a more important preoperative consideration for younger patients and those with benign conditions, which warrants further investigation.

Intra-operative erythropoietin during laparoscopic partial nephrectomy is not renoprotective.

PURPOSE: In pre-clinical studies, acute erythropoietin (EPO) administration has been shown to mitigate the deleterious effects of ischemia/reperfusion injury. We reviewed our clinical experience with intraoperative EPO administration as a potential renoprotective agent during laparoscopic partial nephrectomy (LPN). METHODS: Patients who underwent LPN at our institution between August 2008 and March 2010 received 500 IU/kg EPO 30 min prior to hilar occlusion. Those who underwent LPN between August 2006 and July 2008 without receiving EPO were selected as controls. Demographic, clinical, perioperative, and estimated glomerular filtration rate (eGFR) data were compared for the cohorts preoperatively, and during short-term (<6 months) and long-term (≥6 months) follow-up. RESULTS: Short-term eGFR was evaluable for 39 EPO and 29 controls, while long-term eGFR was evaluable for 26 EPO and 27 controls. Baseline demographic and clinical features of the cohorts were similar. For EPO versus controls, median short and long-term follow-up was 19 days versus 22 days and 10.2 months versus 11.9 months, respectively. Mean preoperative, postoperative, and % change in eGFR were statistically similar for the cohorts during short- and long-term follow-up, without and with adjustment for baseline renal function (unadjusted P-values = 0.28, 0.095, and 0.38, respectively, short term, and 0.61, 0.50, and 0.69, respectively, long term). CONCLUSIONS: In this retrospective study, a single dose of EPO prior to hilar occlusion during LPN had no added protective impact on postoperative eGFR in the short or long term. Prospective evaluation in patients with solitary kidneys may better elucidate its potential renoprotective role in this setting.

Tadalafil for prevention of renal dysfunction secondary to renal ischemia.

INTRODUCTION: Growing evidence suggests that phosphodiesterase-5 inhibitors may mitigate ischemia-related renal damage through multiple mechanisms. We evaluated the role of tadalafil in renal function preservation during experimentally induced ischemia/reperfusion injury (IRI) in a solitary kidney porcine model. MATERIALS AND METHODS: Ten adult female pigs underwent left laparoscopic nephrectomy followed by a 1 week recovery period. They were then randomized to tadalafil versus no treatment prior to cross-clamping the contralateral renal hilum for 90 minutes. The experimental group received 40 mg tadalafil in two equally divided doses, 12 hours before and just prior to surgery. Serum creatinine for each animal was obtained just prior to ischemia induction (D0) and at days 1, 3 and 7 following hilar occlusion. Median creatinine at each time point was compared between groups using the Kruskal-Wallis test. RESULTS: Median serum creatinine at D0 was significantly lower in the tadalafil group (after two doses of tadalafil) (123.8 µmol/L versus 168.0 µmol/L, p = 0.009). As expected, median creatinine for each group rose significantly on D1 (p = 0.04 for each). Median creatinines following hilar occlusion at D1, D3 and D7, however, were not significantly different between groups. CONCLUSIONS: In this porcine model, administration of perioperative tadalafil improves preoperative renal function, but it does not appear to mitigate ischemia/ reperfusion injury from hilar occlusion.

Complications during the initial experience with laparoendoscopic single-site pyeloplasty.

OBJECTIVE: • To review our initial series of laparoendoscopic single-site (LESS) pyeloplasties, focusing on 30-day complication rates as an indicator of learning curve, and to define the expected morbidity. PATIENTS AND METHODS: • The study comprised 28 patients who underwent LESS pyeloplasty by a single surgeon from October 2007. • A chart review was undertaken to identify the complications that occurred within the first 30 days after surgery. RESULTS: • The mean operating time was 197 min. • Seven patients (25%) experienced a total of eight complications. Four patients required nephrostomy tube placement (14%) during the early postoperative period, two for symptomatic obstruction despite the ureteral stent and two for a urine leak. Another had urine leakage that resolved spontaneously after she went home with the surgical drain for 1 week. One patient (4%) developed a retroperitoneal haematoma and required blood transfusion and one had haematuria that prolonged hospital stay by 2 days. • Of the patients experiencing complications, 71% were in the first ten cases. Only two complications occurred in the subsequent 18 patients. CONCLUSIONS: • The LESS pyeloplasty procedure is a technically difficult, even for an experienced laparoscopic surgeon and the surgical challenges of this technique may translate to a higher complication rate for LESS than for conventional laparoscopic pyeloplasty early in the learning curve. However, within a relatively few cases, the complication rate is similar to that of standard laparoscopic pyeloplasty. • Additional follow-up is required to determine the long-term success rate.

HaNDL Syndrome Presenting with Thunderclap Headache.

INTRODUCTION: Transient headache and neurologic deficits with cerebrospinal fluid lymphocytosis (HaNDL) is defined as a secondary, nonvascular headache disorder characterized by the findings described in its name. Patients with HaNDL syndrome typically present with gradual onset migrainous headaches of moderate to severe intensity with transient neurological symptoms. Case Report. We discuss a patient who presented with thunderclap headache, recent transient neurologic deficits, and was ultimately diagnosed with HaNDL after an extensive neurologic evaluation. CONCLUSION: Thunderclap headache has very rarely been described in patients with HaNDL. After excluding emergent and secondary causes, HaNDL should be considered in patients with thunderclap-quality headaches, particularly when there is a history of transient neurological symptoms.

Mobile Stroke Units: Bringing Treatment to the Patient.

PURPOSE OF REVIEW: Mobile stroke units (MSUs) have revolutionized emergency stroke care by delivering pre-hospital thrombolysis faster than conventional ambulance transport and in-hospital treatment. This review discusses the history of MSUs technological development, current operations and research, cost-effectiveness, and future directions. RECENT FINDINGS: Multiple prospective and retrospective studies have shown that MSUs deliver acute ischemic stroke treatment with intravenous recombinant tissue plasminogen activator (IV r-tPA) approximately 30 min faster than conventional care. The 90-day modified Rankin Scores for patients who received IV r-tPA on the MSU compared to conventional care were not statistically different in the PHANTOM-S study. Two German studies suggest that the MSU model is cost-effective by reducing disability and improving adjusted quality-life years post-stroke. The ongoing BEST-MSU trial will be the first multicenter, randomized controlled study that will shed light on MSUs' impact on long-term neurologic outcomes and cost-effectiveness. MSUs are effective in reducing treatment times in acute ischemic stroke without increasing adverse events. MSUs could potentially improve treatment times in large vessel occlusion and intracranial hemorrhage. Further studies are needed to assess functional outcomes and cost-effectiveness. Clinical trials are ongoing internationally.

Geographic Analysis of Mobile Stroke Unit Treatment in a Dense Urban Area: The New York City METRONOME Registry.

Background Mobile stroke units (MSUs) reduce time to intravenous thrombolysis in acute ischemic stroke. Whether this advantage exists in densely populated urban areas with many proximate hospitals is unclear. Methods and Results We evaluated patients from the METRONOME (Metropolitan New York Mobile Stroke) registry with suspected acute ischemic stroke who were transported by a bi-institutional MSU operating in Manhattan, New York, from October 2016 to September 2017. The comparison group included patients transported to our hospitals via conventional ambulance for acute ischemic stroke during the same hours of MSU operation (Monday to Friday, 9 am to 5 pm). Our exposure was MSU care, and our primary outcome was dispatch-to-thrombolysis time. We estimated mean differences in the primary outcome between both groups, adjusting for clinical, demographic, and geographic factors, including numbers of nearby designated stroke centers and population density. We identified 66 patients treated or transported by MSU and 19 patients transported by conventional ambulance. Patients receiving MSU care had significantly shorter dispatch-to-thrombolysis time than patients receiving conventional care (mean: 61.2 versus 91.6 minutes; P=0.001). Compared with patients receiving conventional care, patients receiving MSU care were significantly more likely to be picked up closer to a higher mean number of designated stroke centers in a 2.0-mile radius (4.8 versus 2.7, P=0.002). In multivariable analysis, MSU care was associated with a mean decrease in dispatch-to-thrombolysis time of 29.7 minutes (95% CI, 6.9-52.5) compared with conventional care. Conclusions In a densely populated urban area with a high number of intermediary stroke centers, MSU care was associated with substantially quicker time to thrombolysis compared with conventional ambulance care.

Clinical Information Systems Integration in New York City's First Mobile Stroke Unit.

BACKGROUND: Mobile stroke units (MSUs) reduce time to thrombolytic therapy in acute ischemic stroke. These units are widely used, but the clinical information systems underlying MSU operations are understudied. OBJECTIVE: The first MSU on the East Coast of the United States was established at New York Presbyterian Hospital (NYP) in October 2016. We describe our program's 7-month pilot, focusing on the integration of our hospital's clinical information systems into our MSU to support patient care and research efforts. METHODS: NYP's MSU was staffed by two paramedics, one radiology technologist, and a vascular neurologist. The unit was equipped with four laptop computers and networking infrastructure enabling all staff to access the hospital intranet and clinical applications during operating hours. A telephone-based registration procedure registered patients from the field into our admit/discharge/transfer system, which interfaced with the institutional electronic health record (EHR). We developed and implemented a computerized physician order entry set in our EHR with prefilled values to permit quick ordering of medications, imaging, and laboratory testing. We also developed and implemented a structured clinician note to facilitate care documentation and clinical data extraction. RESULTS: Our MSU began operating on October 3, 2016. As of April 27, 2017, the MSU transported 49 patients, of whom 16 received tissue plasminogen activator (t-PA). Zero technical problems impacting patient care were reported around registration, order entry, or intranet access. Two onboard network failures occurred, resulting in computed tomography scanner malfunctions, although no patients became ineligible for time-sensitive treatment as a result. Thirteen (26.5%) clinical notes contained at least one incomplete time field. CONCLUSION: The main technical challenges encountered during the integration of our hospital's clinical information systems into our MSU were onboard network failures and incomplete clinical documentation. Future studies are necessary to determine whether such integrative efforts improve MSU care quality, and which enhancements to information systems will optimize clinical care and research efforts.

Cost comparison of robotic, laparoscopic, and open partial nephrectomy.

PURPOSE: To compare direct costs associated with open partial nephrectomy (OPN), laparoscopic partial nephrectomy (LPN), and robot-assisted LPN (RALPN). METHODS: A meta-analysis of nonoverlapping studies was performed to determine operating room (OR) time, equipment use, and length of stay (LOS) for OPN, LPN, and RALPN. Cost models using cost data obtained from our institution were created, and robotic cost and maintenance were amortized over 7 years. One- and two-way sensitivity analyses were performed to evaluate the effect of changing variables on the cost effectiveness of each approach. RESULTS: Seven RALPN, 18 LPN, and 8 OPN data series were identified, comprising a total of 477, 2220, and 2745 procedures, respectively. Weighted mean OR time was 188, 200, 193 minutes; weighted mean LOS was 2.6, 3.2, and 5.9 days for RALPN, LPN, and OPN, respectively. LPN was the most cost-effective approach at a mean direct cost of $10,311, with a cost advantage of $1116 and $1652 over OPN ($11,427) and RALPN ($11,962), respectively. Sensitivity analyses demonstrate that significant decreases in robotic costs are required for RALPN to be cost effective. CONCLUSION: Despite similar OR times, LPN is more cost effective than OPN because of shorter LOS. Because of lower instrumentation costs, LPN is the most cost effective despite a longer LOS than RALPN. RALPN has high cost of maintenance and instrumentation, which is partially compensated by the shorter LOS. Evidence of oncological and functional equivalence to OPN is warranted to determine the future role of RALPN.

Minimally invasive nephrectomy: the influence of laparoendoscopic single-site surgery on patient selection, outcomes, and morbidity.

OBJECTIVES: To define clinical scenarios in urology for which laparoendoscopic single-site surgery (LESS) is indicated and likely to be successful. We report a series of LESS nephrectomies and compare patient characteristics with traditional laparoscopic nephrectomies performed during the same time period. METHODS: We retrospectively reviewed all laparoscopic nephrectomies (conventional or LESS) performed by a single surgeon at our institution since our initial LESS cases in August 2007. Patients were not randomized; instead the surgeon used clinical judgment to decide with the patient which procedure should be performed. Factors that may have influenced this decision were retrospectively analyzed. RESULTS: Of all minimally invasive nephrectomies, 47% were performed using LESS technique (30/64). One conversion from LESS to standard laparoscopy occurred. Patients undergoing LESS had a smaller median age (47 vs 63.5 years, P = .004), body mass index (24.4 vs 28.4, P = .001), tumor size in nephrectomies performed for suspected malignancy (4 cm vs 6 cm, P = .043), and hospital length of stay (42.7 vs 46.1 hours, P = .006). LESS patients were also more likely to be undergoing a nephrectomy for a benign indication (50% vs 15%, P = .006). The complication rate for LESS and conventional laparoscopy was 13% (4/30) and 15% (5/34), respectively, with similar distributions across Clavien grades. CONCLUSIONS: With appropriate patient selection, almost 50% of minimally invasive nephrectomies can be performed using LESS with similar complication rates and outcomes compared with traditional laparoscopy. Younger, thinner patients with nononcological indications or smaller tumors are prime candidates for LESS nephrectomy.

Minimal arterial in-flow protects renal oxygenation and function during porcine partial nephrectomy: confirmation by hyperspectral imaging.

OBJECTIVES: To examine the potential for renal protection through incomplete renal artery (RA) occlusion with both assessments of creatinine changes and the use of hyperspectral imaging to monitor tissue oxygenation. Renal ischemia during partial nephrectomy can have adverse consequences on renal function. METHODS: Fourteen pigs with a solitary kidney underwent open partial nephrectomy with warm ischemia. The RA flow was measured and reduced to 25%, 10%, and 0% of baseline for 60 minutes. Hyperspectral imaging was used to assess the percentage of oxyhemoglobin (%HbO(2)) at baseline, during ischemia, and during reperfusion. The %HbO(2) and change in the serum creatinine level from baseline were compared. RESULTS: The baseline RA flow and %HbO(2) were similar in all groups, and, as expected, RA occlusion resulted in decreasing %HbO(2). The reduction of RA flow to 25% and 10% improved the nadir tissue oxygenation compared with 0% flow (P = .01 and P = .04, respectively) and 25% flow also appeared to prolong the interval to reach the nadir %HbO(2). Reperfusion resulted in a swift return to the baseline %HbO(2) in all 3 groups. The change in the serum creatinine from baseline to postoperative day 7 showed significantly improved renal preservation in the 25% RA flow group. CONCLUSIONS: Incomplete RA occlusion during porcine partial nephrectomy resulted in favorable renal oxygenation profiles with as little as 10% blood flow and appeared to be renoprotective when 25% of the baseline RA flow is preserved. Hyperspectral imaging is a sensitive, noninvasive tool for real-time monitoring of renal oxygenation and, thereby, blood flow, which could facilitate intraoperative decision-making to protect kidney function.

Patient-reported body image and cosmesis outcomes following kidney surgery: comparison of laparoendoscopic single-site, laparoscopic, and open surgery.

BACKGROUND: Laparoendoscopic single-site surgery (LESS) is reported to result in superior cosmesis versus alternative surgical approaches, based solely on surgeon assessment or anecdotal evidence. OBJECTIVE: Evaluate patient-reported body image and cosmesis outcomes following kidney surgery. DESIGN, SETTING, AND PARTICIPANTS: We conducted a prospective and retrospective observational cohort study involving patients who underwent kidney surgery (n=114) via LESS (n=35), laparoscopic (n=52), or open (n=27) approaches. Cosmesis was evaluated using a comprehensive survey administered ≥3 mo postoperatively. MEASUREMENTS: Survey components were a body image questionnaire (BIQ) consisting of body image and cosmesis subscales, a photo-series questionnaire (PSQ) assessing scar preferences after knowledge of scar outcomes for alternative surgical approaches, and query of preference for future surgical approach using a trade-off method. Body image, cosmesis, and PSQ scales ranged from 5 to 20, 3 to 24, and 1 to 10, respectively. RESULTS AND LIMITATIONS: Median BIQ component scores did not significantly differ across surgical approaches. Median ratings for the LESS, laparoscopy, and open scar photographs were 8, 5, and 5, respectively (p=0.0001). Before viewing photographs, median self-scar ratings for LESS, laparoscopy, and open approaches were 9, 5, and 6.5, respectively (p=0.02); after photographs, ratings were 9, 7, and 7, respectively (p=0.008). Assuming equivalent surgical risk among the approaches, overall preference for future LESS, laparoscopy, or open surgery was 39%, 33%, or 4%, respectively. As theoretical risk of LESS was raised, preference for LESS decreased, whereas preference for laparoscopy and open surgery increased. Study limitations are a nonrandomized design and the use of a nonvalidated scale. CONCLUSIONS: Urologic patients favor LESS cosmesis outcomes over those for laparoscopy or open surgery. Considering the superior scar satisfaction among LESS patients, who were younger and more likely to be undergoing surgery for benign disease, we infer that this demographic most values the cosmetic advantages of LESS.

Novel stone-magnetizing microparticles: in vitro toxicity and biologic functionality analysis.

BACKGROUND AND PURPOSE: We have developed novel iron-based microparticles (Fe-MP) that bind to calcium oxalate stone fragments, rendering them paramagnetic. Previously, we demonstrated enhanced efficiency of stone extraction in an inanimate model using magnetic instrumentation. Before in vivo stone extraction studies, we sought to further characterize Fe-MP with regard to cellular toxicity and to assess the influence of biologic fluids on binding performance. TOXICITY: Monolayers of murine fibroblasts, human urothelium, and human transitional-cell carcinoma cells were exposed to 1 mg/mL of Fe-MP or saline via an agarose overlay. Cellular viability was assessed using neutral red staining and densitometry. Biologic functionality: Human calcium oxalate stone fragments were incubated with a solution of 1 mg/mL of Fe-MP containing varying concentrations of urine (10%-50%) or blood (0.5%-2%) for 10 minutes. Fragments were then extracted using an 8F magnetic tool. Assays of 10 stone fragments categorized as small (3-3.9 mg) or large (6-6.9 mg) were run in quadruplicate at each concentration. RESULTS: No toxicity was seen in any of the three cell lines after 48 hours of particle exposure, except in urothelial cells at the lowest cell concentration. Stone extraction success was 100% for all stones, regardless of concentration of urine or blood, and extractions were completed in less than 10 minutes. CONCLUSIONS: Preliminary toxicity testing revealed minimal to no cellular toxicity that was attributable to Fe-MP. The microparticles function well in the presence of clinically relevant concentrations of urine and blood that may be present during endoscopic stone surgery. Further toxicity and stone extraction testing in animal models is necessary.