750 mg per day of acetazolamide in the prevention of acute mountain sickness (AMS), as recommended in the meta-analysis published in 2000 in the British Medical Journal, may be excessive and is controversial. To determine if the efficacy of low-dose acetazolamide 125 mg bd (250 mg), as currently used in the Himalayas, is significantly different from 375 mg bd (750 mg) of acetazolamide in the prevention of AMS, we designed a prospective, double-blind, randomized, placebo-controlled trial. The participants were sampled from a diverse population of (non-Nepali) trekkers at Namche Bazaar (3440 m) in Nepal on the Everest trekking route as they ascended to study midpoints (4280 m/4358 m) and the endpoint, Lobuje (4928 m), where data were collected. Participants were randomly assigned to receive 375 mg bd of acetazolamide (82 participants), 125 mg bd of acetazolamide (74 participants), or a placebo (66 participants), beginning at 3440 m for up to 6 days as they ascended to 4928 m. The results revealed that composite AMS incidence for 125 mg bd was similar to the incidence for 375 mg bd (24% vs. 21%, 95% confidence interval, -12.6%, 19.8%), in contrast to significantly greater AMS (51%) observed in the placebo group (95% confidence interval for differences: 8%, 46%; 12%, 49% for low and high comparisons, respectively). Both doses of acetazolamide improved oxygenation equally (82.9% for 250 mg daily and 82.8% for 750 mg daily), while placebo endpoint oxygen saturation was significantly less at 80.7% (95% confidence interval for differences: 0.5%, 3.9% and 0.4%, 3.7% for low and high comparisons, respectively). There was also more paresthesia in the 375-mg bd group (p < 0.02). We conclude that 125 mg bd of acetazolamide is not significantly different from 375 mg bd in the prevention of AMS; 125 mg bd should be considered the preferred dosage when indicated for persons ascending to altitudes above 2500 m.

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Background: Balloon sinus dilation (BSD) is a commonly performed sinus procedure in the United States. Several cadaveric studies have evaluated BSD accuracy and the maxillary sinus has consistently been shown to be the most challenging to cannulate. We designed an independent study to evaluate the intraoperative accuracy of maxillary sinus BSD. Methods:A prospective, single-blinded trial evaluating the accuracy of maxillary sinus BSD was performed using 2 commercially available BSD systems (guidewire-and probebased systems) randomly assigned to patients undergoing endoscopic surgery for chronic rhinosinusitus without nasal polyps (CRSsNP) or a skullbase approach in patients without sinus disease. All patients underwent maxillary BSD followed by uncinectomy to reveal dilation of the natural maxillary sinus ostia. The recorded procedures were reviewed by 3 fellowship-trained rhinologists from different institutions blinded to the BSD system utilized. The primary endpoint compared accuracy of maxillary BSD a empts. The secondary endpoint compared accuracy between the 2 systems.Results: Twenty-nine maxillary BSD procedures were performed in 18 patients (age range, 20-79 years; mean, 51 years) without nasal polyposis undergoing maxillary antrostomy as part of a more extensive procedure. BSD was successful in 18 of 29 (62%) a empts and unsuccessful in 9 of 29 (31%) a empts, with statistically "almost perfect" interrater agreement (kappa = 0.86). There was no statistical difference between the 2 BSD systems (p = 0.81). Conclusion:Maxillary BSD appeared to be less accurate in living patients when compared with findings from previously published cadaver studies. There were no differences in accuracy between the probe-and guidewire-based systems. This is the first non-industry-sponsored study evaluating maxillary sinus BSD in living patients. Further studies are needed to investigate the clinical implications of our findings. C 2019 ARS-AAOA, LLC.

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e15124 Background: Circulating tumor cells (CTCs) are found in human blood when cancers undergo metastatic dissemination, and CTCs have been reported as a surrogate marker for tumor response and linked to shorter survival in metastatic prostate cancer patients. This study assessed the use of CTCs as a continuous factor for clinical monitoring of prostate cancers patient in real time and evaluated the association between baseline CTC number, various clinical characteristics, and survival. Methods: CTCs were enumerated using the CellSearch FDA cleared CTC kit in 206 patients with metastatic prostate cancer. Variables including metastatic site, PSA, Gleason score, level of testosterone and androgen treatment were tested for association with CTC number. The probability of patient survival over time was estimated by the Kaplan-Meier method. Results: Baseline CTC numbers were strongly associated with survival (p<0.0001), with overall survival being significantly poorer in patients with ≥5 CTCs. Significantly higher CTC numbers were observed in patients with bone metastasis (mean=41.1 CTCs) compared to those with lymph node metastasis (mean=2.5 CTC, p=0.026). Analysis of the association between CTC counts and PSA level revealed a weak positive correlation between CTC number and PSA (Correlation coefficient r=0.269, Significance level p<0.001). CTC number further correlated with the Gleason score (p=0.009) and lower testosterone levels (p<0.0001). Patients with no androgen depletion had significantly lower numbers of CTCs (median=3.94) compared to those with androgen depletion (median=406, p<0.001). Conclusions: Baseline CTCs are predictive of patient survival and are significantly correlated with clinical characteristics in prostate cancer patients.Our study confirms previous findings that support the use of CTC levels as a prognostic biomarker for prostate cancer patients.