The distal branch of the perineal nerve supplies the caudal udder (to the base of the posterior teats) and the escutcheon of the udder. (B342.16.w16, J13.3.w1) The perineal nerve block is a regional nerve block which may be used to provide desensitisation for certain surgical procedures to the caudal udder. (B342.16.w16, J234.12.w2)

Perineal nerve block:

• Restrain the cow.
• At the ischial arch, about 2.0 to 2.5 cm lateral to the midline on both sides, inject 5.0 to 7.0 mL of 2% lidocaine solution into the subcutaneous and subfascial tissues. (B342.16.w16, J234.12.w2)

• For desensitisation of the caudal teats and escutcheon of the udder in the standing cow. (J234.12.w2) For removal of supernumerary teats or warts in the caudalmost area of the udder and the escutcheon. (B342.16.w16)
• Does not interfere with healing. (B342.16.w16)

• The analgesic technique chosen should be decided based on the procedure to be undertaken, the facilities available and the skills of the practitioner. (J215.7.w1)
• Standard aseptic techniques should be practiced when performing local analgesia, including surgical preparation of the skin and sterile injection techniques. (J215.7.w1)
• Aspiration to check for blood should be carried out prior to injection, to avoid inadvertent intravenous injection. (J215.7.w1)
• Epinephrine (adrenalin) at 1 part per 200,000 or norepinephrine (noradrenaline) at 1 part per 100,000 may be added to local anaesthetic solution to decrease the absorption of the agents and prolong their action. These vasopressors should not be used for analgesia of appendages such as the tail, teats or toes as they may produce sufficient circulatory compromise of the appendage to result in tissue necrosis and sloughing. (J215.7.w1)
• Hyaluronidase may be added to local anaesthetic solutions to increase tissue permeability and thus decrease the time to onset of analgesia and reduce the volume of local anaesthetic solution required; it will also reduce the duration of analgesia. However it is questionable whether it is needed other than with procaine hydrochloride solution, since other local anaesthetic agents, such as lidocaine, penetrate tissues adequately. If used, then 150 turbidity reducing units (TRUs) of hyaluronidase may be added per 25 mL of 2% lidocaine. Combining both adrenaline and hyaluronidase with local anaesthetic solution may both increase initial spread and onset while also reducing uptake and therefore prolonging anaesthesia. Note: Use of hyaluronidase is NOT a substitute for accurate placement of local anaesthetic solution, since the tissue fascial planes will still act as barriers. (B342.16.w16)

Physical restraint and/or sedation is required in addition to the desensitisation of the operational area before any operation is carried out on the teat, both for the safety of the surgeon and to maintain asepsis. (J234.12.w2)

• The cow is restrained standing for minor procedures, otherwise in lateral or dorsal recumbency. (J234.11.w3)

• 2% lidocaine. (B342.16.w16, J234.12.w2)
• Needle.
• Syringe.

• This procedure is technically more difficult than local infiltration. (B342.16.w16)

• Inexpensive. (B342.16.w16)