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Updated: Jul 13, 2026

Electrophysiological Methods to Assess Peripheral Pain Block in an Anesthetized Rat
Published on: November 21, 2025
Pudendal block with bupivacaine for postoperative pain relief
Luiz Eduardo Imbelloni1, Eneida Maria Vieira, Marildo A Gouveia
1Institute for Regional Anesthesia, Hospital de Base da FAMERP, São José do Rio Preto, SP, Brazil. dr.imbelloni@terra.com.br
Purpose:
Postoperative pain after hemorrhoidectomy is very intense, and the pain at the first postoperative defecation is very intense. Based on our pilot initial results that reflected reduced postoperative pain, we conducted a prospective, randomized, double-blind study to investigate whether the analgesia produced by bilateral pudendal nerve block using a nerve-stimulator could provide better postoperative pain relief compared with the routine technique in use in the Department of Anesthesia.
Methods:
After Ethical Committee approval and informed consent, 100 patients scheduled for hemorrhoidectomy were randomized into control (C) and study (P) groups with 50 patients each. Bilateral pudendal nerve block with 0.25 percent bupivacaine was performed with nerve-stimulator. Evaluated parameters were pain severity, duration of analgesia, demand analgesia, and possible technique-related complications. Data were evaluated 6, 12, 18, and 24 hours after surgery completion. The first defecation and patient satisfaction were recorded.
Results:
Successful pudendal nerves stimulation was achieved in all patients in the study group. The pudendal nerve block group was found to have better postoperative pain relief, reduced need for analgesics, and patient satisfaction. Mean analgesic duration was 23.8 +/- 4.8 hours vs. 3.6 +/- 1 hours. All patients in the pudendal nerve block had spontaneous micturition vs. 48 patients in the control group. The pudendal analgesia was considered excellent by 44 patients and satisfactory by 6 male patients. The six male patients complained because of penile anesthesia. No anesthetic-related local or systemic complications were observed.
Conclusions:
In this controlled study, bilateral pudendal nerve block oriented by nerve stimulator provided excellent analgesia with low need for opioids, without local or systemic complications, and without urinary retention.
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