Anatomical Basis And Clinical Research On The Application Of Perineal Nerve Block In Transperineal Prostate Biopsy Under Local Anesthesia

Background and objectiveTransperineal prostate Biopsy has the advantages of high detection rate and low infection rate,which has been extensively applied gradually in recent years.However,no standard local anesthesia technique is available for such procedure so far.We discover in clinical practice that,remarkable anesthetic effects can be achieved in 2 relatively fixed sites,which are about 2cm away from both sides of the anterior anal margin,in the manner of injection of local anesthetics.As far as we are concern,this may be related to the block of perineal nerve,the branch of pudendal nerve.Therefore,this research first verified the possibility of these two sites as the entry points of perineal nerve block through anatomical and transcutaneous electrical nerve stimulation(TENS).Furthermore,the pain degree as well as the incidence of adverse events in patients when applying perineal nerve block in transperineal prostate biopsy through these two sites was also observed through randomized controlled trials,so as to explore the effectiveness,convenience and safety of it as a new local anesthesia technique for transperineal prostate biopsy.Methods(1)Fundamental anatomical research on perineal nerveFundamental anatomical research was carried out on the perinea of 5 adult male cadavers,and the average distance between both perineal nerves and the midline was measured at anterior anal margin level.(2)Relative depth of perineal nerve verified under transcutaneous electrical nerve stimulator guidanceThe relative fixed positions of block points were verified in 20 patients through peripheral nerve plexus electrical stimulator,and the depth range of perineal nerve was explore.In the meantime,nerve infiltration anesthesia and transperineal prostate biopsy were conducted under its guidance.Moreover,the Visual Analogue Scale(VAS)score was adopted to assess and record the pain degree in each stage.Operation time,intraoperative changes of heart rate and blood pressure,intraoperative and postoperative adverse reactions and postoperative pathological results were recorded.Finally,the SPSS22 statistical software was used for data analysis.(3)Randomized controlled trials on the application of perineal nerve block in transperineal prostate Biopsy without nerve stimulator90 patients were randomly divided into 3 groups.Group 1 was the control group receiving peri-prostate infiltration anesthesia(including the path of insertion).Group 2 was the control group receiving PAT infiltration anesthesia,and group 3 was the observation group undergoing perineal nerve block at the block points.Afterwards,transperineal prostate biopsy was conducted,respectively,and the VAS score was adopted to assess and record the pain degree at each stage.In addition,operation time,intraoperative changes of heart rate and blood pressure,intraoperative and postoperative adverse reactions and postoperative pathological results were recorded.Finally,the SPSS22 statistical software was used for data analysis.Results(1)Fundamental anatomical research on perineal nerveThe overall average distance between the superficial branch of perineal nerve and the midline was 1.86±0.06 cm at the anterior anal margin level;while that between the deep branch of perineal nerve and the midline was 2.16±0.06 cm,which was consistent with the sites we discovered.(2)Relative depth of perineal nerve verified under transcutaneous electrical nerve stimulator guidanceThe depth of insertion required to complete perineal nerve block on the left side ranged from 3.00 cm to 4.00 cm,with an average of 3.48±0.31 cm,while that on the right side was 3.00-4.00 cm,with an average of 3.49±0.33 cm.(3)Randomized controlled trials on the application of perineal nerve block in transperineal prostate Biopsy without nerve stimulatorDifferences in the age,height,weight,BMI,prostate volume,PSA and postoperative prostate detection rates among the 3 groups were not statistically significant(P>0.05),but the operation time and anesthesia time in groups 2 and 3 were longer than those in group 1(P<0.001).Differences in pain scores at the time of ultrasonic probe placement and local anesthesia injection among the 3 groups were not statistically significant(P>0.05).Meanwhile,differences in the frequency of insertion at the time of pain occurrence in skin puncture,capsule breakthrough and sampling,as well as in the highest VAS score showed no statistical significance(P>0.05).However,the frequency of insertion at the time of pain occurrence from subcutaneous placement of puncture needle to prostate insertion was 2.20±1.61 in group 3,which was notably lower than 5.00±2.56 in group 1 and 4.17±2.28 in group 2.Additionally,the mean of the highest VAS score in group 3(1.70±0.88)was also evidently lower than 2.27±0.58 in group 1 and 2.17±0.83 in group 2.Differences in intraoperative and postoperative complications among the 3 groups were not statistically significant(P>0.05).Conclusions Anatomical,electrophysiological and clinical trials have verified that,the sites 2cm away from both sides of the anterior anal margin can serve as the perineal nerve block points.Moreover,the application of perineal nerve block through these 2 block points in transperineal prostate biopsy under local anesthesia is effective,safe and reproducible,which displays unique superiority on alleviating pain during needle insertion.In order to remember the points easily,we named it “transperineal prostate biopsy local anesthesia switch”(abbreviated as TPA switch).