Author: Miguel Martinez, Anaesthesia and Analgesia Specialist
Hi, my name is Miguel Martinez, Anaesthesia and Analgesia Specialist at Northwest Veterinary Specialists. A large part of what we do on a daily basis is focused on making dogs and cats as comfortable and pain-free as possible.
In recent years, there has been an enormous development of what is called regional anaesthesia. This technique consists of injecting local anaesthetic near a nerve to desensitise or numb a specific area of the body. The analgesia (pain relief) achieved is superb.
These local blocks are very effective if the drug is deposited very near the nerve, because otherwise they do not work well. The question is: How do we know where the nerve is?
Traditionally, we used to guess this by localising some anatomical landmarks in the body, and more recently using a little electrical current to stimulate the nerve and produce a muscle twitch. However, nowadays the gold standard technique is to see the nerves and surrounding anatomical structures by means of ultrasound images.
Fortunately, at Northwest Veterinary Specialists, we have a strong team of ultrasonographers and excellent equipment (fig. 1). With the aid of ultrasound images, we perform what we call ultrasound guided nerve blocks. Currently, the vast majority of our patients receive one or more of these blocks when they undergo any surgical procedure. The advantages of US guided nerve blocks are improved post-operative comfort, enhanced recovery and a reduction of complications.
As an example, I am going to show you how we perform a nerve block to treat perioperative pain in a dog undergoing a cranial cruciate ligament repair (TPLO technique).
First of all, we anaesthetised the dog to prepare it for surgery. Our nurses and theatre technicians prepare all the equipment and clip and clean the skin of the surgical area (fig 2).
Then, with the aid of the ultrasound machine, we localise the saphenous and sciatic nerve. These two nerves provide sensory input from all areas of the back leg from the stifle and downwards (fig. 3 ,4 ,5 and 6).
Once we have a good image of the relevant nerve, we introduce a specially designed needle under ultrasound guidance to the vicinity of the nerve sheath. We make sure we haven’t pierced any blood vessels before injecting the local anaesthetic drug to surround the nerve completely. This, in turn, will numb the target area in just a few minutes and for several hours. (fig, 7 and 8) The surgeons will repair the cruciate ligament surgically while the patient is closely monitored by our anaesthesia nurses under our guidance. At the end of the procedure, we take the patient to the recovery ward to provide a calm and controlled environment for recovery from anaesthesia. Once the patient is awake, we perform regular checks to confirm the patient is comfortable and pain free. To that effect, we use validated pain scoring charts. The analgesia obtained with the nerve blocks is of unparalleled quality and the advent of ultrasound guided nerve blocks has revolutionised completely the way we approach perioperative pain management in recent years. I believe it has made a huge difference to our beloved dogs and cats.