In some individuals cutaneous branches of the second cervical nerve (C2) may innervate the caudal area of the horn base. (J3.80.w1)

Local anaesthetic block of the cornual branch of the zygomaticotemporal (lachrymal) nerve:

• Insert a 2.5 cm, 18 gauge needle into the upper third of the temporal ridge, immediately behind the ridge and about 2.5 cm below the base of the horn, to a depth of 0.7 to 1.0 cm. (B205.12.w12) 
  • The nerve may be palpable, between the frontalis and temporal muscles, about half way from the lateral canthus of the eye to a point about 3cm below the lateral base of the horn. (J234.12.w2)
  • In large bulls the needle should be inserted to about 2.5 cm deep. (J234.12.w2)
• Draw back on the plunger to check that the needle is not placed intravascularly. (J234.12.w2)
• Inject 5 to10 ml 2% lidocaine hydrochloride (the amount required depends on the size of the animal). (J234.12.w2)
• A blink response should be noted during administration; drooping of the upper eyelid is a good early sign of correct anaesthesia.
• Failure may occur if the anaesthetic solution is injected too deeply, into the temporal muscle aponeurosis. (J234.12.w2; B205.12.w12)
• Note: In large individuals with well developed horns make a second injection about 1 cm caudal to the first injection, to block the posterior division of the nerve. (B205.12.w12)

Additional block:

• In individuals with well-developed horns an additional injection may be required, posterior to the horn or as an elliptical ring block around the horn base. (J234.12.w2, B344.66.w66)
  • This injection should block cutaneous branches of cervical nerves. (B205.12.w12)
  • Slide a long needle, approximately 19 gauge, under the skin and inject the local anaesthetic solution while withdrawing the needle. (B344.66.w66)
  • Take particular care to inject on the caudal aspect of the horn to ensure that any innervation from the cervical nerves is affected. (B344.66.w66)

• For disbudding calves or dehorning cattle.

• Redirecting the needle several time during injection of the local anaesthetic increases the volume of tissue into which the solution is injected and therefore decreases the risk that the nerve is not anaesthetised. (B344.66.w66)
• Check that the whole area at the base of the horn has been anaesthetised before commencing the operation. (B344.66.w66)

General notes for local anaesthesia:

• 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 (adrenaline) at 1 part per 200,000 or norepinephrine at 1 part per 100,000 may be added to the local anaesthesia 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)

• Failure may occur if the anaesthetic solution is injected too deeply, into the temporal muscle aponeurosis. (J234.12.w2)
• In individuals with well-developed horns a second injection may be required, posterior to the horn or as an elliptical ring block around the horn base. (J234.12.w2)
• Injection under the skin at the horn base may be difficult as the skin is tightly applied to the skull in this area. (B344.66.w66)

• Local anaesthetic solution e.g. 2% lidocaine hydrochloride.
• Needle (20G, 2.5 cm, longer for large bulls). (J234.12.w2)
• Syringe.