AIM: To determine the content of emodin and physcion in rat plasma by nonaqueous RP-HPLC. METHODS: After hydrolysis and extraction, the content of emodin in the plasma was determined by nonaqueous RP-HPLC. The separation was performed on Kromasil C 18 column (250 mm?4.6 mm, 5.0 ?m) with the mobile phase comprised of methanol-acetic acid (99.9∶0.1). The flow rate was 1.0 mL?min -1 and the detection wavelength was at 254 nm. RESULTS: The linear ranges for emodin and physcion were in the range of 0.0425-2.8 ?g?mL -1 and 0.0491-3.14 ?g?mL -1 , respectively. The average recoveries of emodin and physcion were 95.7%-100.1% and 96.2%-99.8%, with corresponding RSD of 1.3% and 1.6% respectively. CONCLUSION: This method is simple, rapid, accurate and reproducible with RP-HPLC to detect rhein in plasma.

【Objective】 To compare the perioperative blood loss between interlaminar and transforaminal approaches by percutaneous endoscopic discectomy in order to provide more reference for guiding the proper choice of surgical methods clinically. 【Methods】 We retrospectively analyzed the clinical data of 160 patients who underwent percutaneous endoscopic lumbar discectomy from June 2019 to November 2020， with 80 patients in interlaminar approach group and 80 in transforaminal approach group. The blood loss was calculated according to Gross formula. 【Results】 The perioperative total blood loss （mL）， hidden blood loss （mL） and hemoglobin loss （g/L） were significantly lower in interlaminar approach group than in transforaminal approach group （119.73±179.26 vs. 158.6±190.65， 109.73±179.53 vs. 148.78±190.19， 3.76±8.12 vs. 4.31±7.62） （P<0.05）. However， there was no significant difference in visible blood loss between the two groups. 【Conclusion】 The perioperative hidden blood loss accounts for a large proportion in percutaneous endoscopic lumbar discectomy. In addition， the interlaminar approach causes less blood loss than the transforaminal approach.