Accuracy of blind approach and ultrasound–guided techniques for pudendal nerve block in cadaveric cats - a pilot study

This blinded, randomized and prospective cadaveric pilot study compared the accuracy of a blind approach for pudendal nerve block (PNB–B) with that of the ultrasound–guided technique (PNB–US) in cats. Two male cat cadavers were used for a preliminary anatomical study to identify palpable bony landmarks, while eight additional cadavers were employed for the experimental phase. Each hemipelvis was randomly assigned to one of the two techniques: PNB–US, performed according to the deep dorsolateral method described by Adami et al. (J Feline Med Surg 15:901–907, 2013), or the PNB–B, developed based on the preliminary anatomical findings, identifying the application point laterally to the sacrococcygeal joint. Block accuracy was assessed by dye spread, considering the nerve branches stained in each approach. The success rate was 87.5% (7/8) for PNB–B and 75% (6/8) for PNB–US. In the injections considered accurate in PNB–B, dye was deposited at the point of confluence of sacral nerve branches forming the pudendal nerve, while in PNB–US the pudendal nerve was stained near the exit of the pelvis. The ischial nerve was inadvertently stained in 75% (6/8) of PNB–B and 25% (2/8) of PNB–US injections. These findings indicate that PNB–B can be considered an effective alternative to the ultrasound–guided technique, although, in clinical settings, it may produce motor blockade due to unintended ischial nerve involvement. The results provide preliminary data to support future in vivo clinical studies aimed at confirming the safety and analgesic efficacy of this novel blind technique in cats.