In this VETgirl online veterinary continuing education blog, we discuss how to perform a coccygeal block. Coccygeal blocks allow us to provide analgesia without affecting motor function. The use of a coccygeal block is beneficial for certain conditions including pelvic fractures, perineal injuries, surgery of the lower urinary tract, feline urethral obstruction, tail pull injuries, and reproductive emergencies (e.g., dystocia). As a coccygeal block will only provide analgesia to the perineal region for approximately 1 hour, additional analgesic therapy (e.g., buprenorphine 11-22 mcg/kg, IV q 6 or long-acting Simbadol at 0.12-0.24 mg/kg, SQ q 24) should be continued. Note that there are some contraindications for performing a coccygeal block including: anatomical abnormalities (e.g., Manx cat, pelvic fractures) that cause loss of appropriate landmarks, skin infections over the insertion site, severe obesity, hypotension, septicemia and coagulopathies. Rare complications can occur with coccygeal blocks, including lidocaine toxicity, infection at the injection site, and inadequate analgesia.
Here, a step-by-step approach on how to perform a coccygeal block:
1. Use a sterile bottle of 2% preservative-free lidocaine at a dose of 0.1-0.2 mL/kg.
2. Sedate the patient. Once sedated, the patient is placed in ventral recumbency and the sacrococcygeal region surgically prepped. The injection site can be found by palpating the space between the sacrum and first coccygeal vertebra, which can be easily palpated when the tail is moved. Draping is not required and may interfere with the procedure, but aseptic technique is imperative.
3. After donning sterile gloves, the injection site is located just cranial to the first coccygeal vertebrae. Alternatively, the first or second coccygeal intervertebral space can be used. To facilitate this step, an assistant can manipulate the tail.
4. A 25 gauge, 1 inch needle is inserted at a 30 to 45° angle at the midline of the sacrococcygeal space (which is identified with the index finger of the other hand). While advancing the needle, a characteristic “pop” can be felt. This occurs as the needle penetrates the ligamentum flavum.
5. After entering the epidural space, a syringe is attached and gentle negative pressure applied. If blood or cerebrospinal fluid is obtained, the procedure needs to be started again. If no blood or any other fluid is aspirated, proceed to infuse the calculated volume into the epidural space. No resistance to injection should be noticed. Inappropriate infiltration into the subcutaneous tissue may create resistance. The needle is removed after injection.
6. You can tell if your epidural is working if you notice relaxation of the tail and rectum; also, pinching of the tail should not produce a response. If a pain response is elicited after 5 minutes of the first injection, a second injection can be attempted. Due to the increase risk of complications, no more than 2 attempts are recommended.
7. Urethral de-obstruction can be performed after the lidocaine block has taken effect (which occurs within just minutes).
When in doubt, this is a procedure you can easily implement into your blocked cats to improve analgesia. Personally, as it only lasts 1-hour, we don’t do this as commonly and only with severe urethral spasming.