The Optimum Dosage of Prilocaine in Periprostatic Nerve Block During Transrectal Ultrasound Guided Prostate Biopsy: A New Approach in Dose Calculation
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Objective: We aimed to calculate the optimum dose of prilocaine per one mL prostate volume in periprostatic nerve block (PPNB) during transrectal ultrasound (TRUS) guided prostate biopsy (PBx). Materials and Methods: We retrospectively evaluated the medical records of 83 patients from whom 12 cores TRUS guided PBx were obtained between years 2011 and 2013. Prostatic sizes were evaluated separately as Size 1 (anterior-posterior on the axial plane), Size 2 (transversal), and Size 3 (cranial-caudal on the sagittal plane) for all patients. The visual analog scores (VAS) of the patients during PBx, prostatic volumes, and prilocaine doses per one mL prostate were evaluated. The correlation between VAS of patients during PBx and prostatic volume, the prostatic sizes and prilocaine dosage per one mL prostate was analyzed using Cubic regression test. Results: It was found that VAS scores of patients were significantly positive correlated with prostatic volume, Size 1, 2 and 3 (p<0.05). However, there was a negative significant correlation between VAS and prilocaine dose per one mL prostate volume (r=-0.402, p<0.01). The dose of 0.1 mL prilocaine infiltration per one mL prostatic tissue in PPNB was the maximum dose that caused a mild and under annoying pain (VAS<2) in patients according to cubic regression formula. Conclusion: Prilocaine dosage, prostatic volume and prostatic sizes (especially anterior-posterior and cranial-caudal) significantly affect VAS scores during TRUS guided PBx. The pain in TRUS guided PBx should be controlled with an optimum dose of prilocaine as 0.1 mL per one mL of prostatic tissue.