Using the best technique for injecting epidural anesthesia

The latest updates in epidural anesthesia were presented in a session at the dvm360® Directions in Veterinary Medicine conference in Indianapolis, Indiana; June 24-25, 2022. In his lecture, Gianluca Bini, DVM, MRCVS, DACVAA, assistant professor of anesthesiology and pain management at The Ohio State University, discussed the ideal technique and equipment to use when using epidural anesthesia.

Bini first explained how the proper use of epidural anesthesia can reduce the incidence of chronic pain after the patient wakes up from the procedure being performed. “The best way of tackling [chronic pain] is to cut down pain in the transmission phase and that's what we do with epidural anesthesia. [The pain is] prevented from reaching the spinal cord, no way that chronic pain happens because the stimuli doesn't reach the spinal cord. So, when you have surgical stimulation, it's going to travel across this nerve and is going to get cut out,” Bini said.¹

Techniques for using epidural

Bini explained the best practices for using epidural for a patient with a few tips as follows¹:

• Location of placing the epidural. “When we perform an epidural, normally, we use [the location] L7-S1. We find this place by palpating the ileum wings, and we have our thumb and our middle finger on the ileum wings, and then we palpate the L7-S1 space with our index finger. You normally use L7-S1 because that's the biggest space that’s between two vertebrae. It’s easy to identify, but other locations can be used as needed,” Bini said.
• Positioning on the patient. Bini reminded veterinarians that they should also be comfortable when injecting the epidural. “The other thing that's important is your positioning to the dog. That’s something that we, in veterinary medicine, need to become more aware of; ergonomics sometimes can make the difference. You need to find a position that's comfortable for you. If you're uncomfortable, and it's a procedure that you don't perform every day and that you're not confident with it, then your chances of failing may increase,” Bini said.
• Make sure to go through each layer. When performing an epidural the needle goes through each layer to reach the correct place in the patient’s epidural space. Bini described these layers, in order, as the skin, subcutaneous tissue, fat, interspinous ligament, and ligamentum flavum. Each layer should feel a bit different as the needle passes through each one, he noted.
• Inject slow. Don’t go too fast, otherwise the drug may not spread properly. According to Bini, if you inject too fast the “drugs are going to try to find the path of least resistance, and may not spread as cranial as you want ” and potentially make the procedure ineffective.

Types of needles

The Tuohy needle is used for epidural injections and is an atraumatic needle with a curved tip, according to Bini. He noted that with the Tuohy needle, it is easier to feel each layer when injecting, than with a spinal needle. It also reduces the chances of accidental intrathecal injection. The spinal needle has a very sharp tip and can often go too deep penetrating the dura mater or a blood vessel, if not handled properly. However, Bini stated that the Tuohy needle, “separates [each fiber layer], it doesn't cause damage, it's really, really hard to go too deep… this is the right tool for the right job.”¹

Adverse effects or complications

Bini concludes his lecture by warning veterinarians of the adverse effects of epidurals or any complications that can occur during or after the procedure. He also described some absolute contraindications as lack of proper equipment, lack of expertise, sepsis, coagulopathies, and infection at the injection site.

He also mentioned that “even if you do everything right, there is an 11% to 30% failure rate reported. So, in all cases, you should have some rescue analgesia available.”¹

Reference

Bini G. Old but gold: Updates & myth-busting of epidural anesthesia. Presented at: Directions in Veterinary Medicine; June 24-25, 2022; Indianapolis, Indiana.