Acute Pain Management
When your animal is a patient at the Cornell University Hospital for Animals, he or she will first be assessed and treated for pain by the service primarily managing the case (e.g., Surgery, Medicine, Oncology, etc.). If he or she requires anesthesia for surgery or diagnostic procedures, he or she will be transferred to the Anesthesiology and Pain Medicine Service. On this service, board-certified anesthesiologists – faculty at the College of Veterinary Medicine – as well as anesthesiologists-in-training (called residents), interns (veterinarians completing a year of intensive post-graduate clinical training), licensed veterinary technicians (LVTs), veterinary assistants, and veterinary students work together to diagnose and treat pain. However, our role does not end when the patient leaves the operating room. We often follow patients with intensive, unique, or dynamic pain management needs into the Intensive Care Unit (ICU) or Nursing Care Unit, assisting other services by providing advanced techniques. We also offer our services in the ER.
We use the same techniques (e.g., nerve stimulation, ultrasonography) and products (e.g., needles, catheters) used in human hospitals. Read more about some of them below.
Neuraxial (epidural and spinal) analgesia
Neuraxial anesthesia is the injection of analgesic drugs around the neuraxis (spinal cord). This includes both epidural and intrathecal injection. With epidural injection, drugs are injected just outside the dura mater, the outermost meningeal layer. With intrathecal injection, drugs are injected directly into the cerebrospinal fluid, deep to the dura mater and arachnoid. Epidural injection is more common in veterinary patients. Injecting analgesic drugs around the spinal cord produces analgesia superior to that provided by systemic drugs, at lower doses.
Epidural catheterization
Sometimes, a patient’s pain is excruciating and expected to last for days to weeks while the patient recovers. Examples include multiple pelvic fractures in dogs or septic arthritis in horses. Instead of performing a single epidural injection, a fine catheter can be inserted into the epidural space for repeated injection of drugs. These catheters can be left in place for days, as long as they are kept sterile.
Peripheral nerve blocks
Peripheral nerve blocks involve the injection of local anesthetic, usually along with other drugs, around a nerve external to the spinal column. This is usually done under ultrasonography so that the anesthesiologist can visualize the nerve, ensuring the local anesthetic is injected in close proximity to it. Occasionally, this is done in conjunction with nerve stimulation. Nerve stimulation involves passing a low current through a special stimulating needle. If the nerve contains neurons responsible for muscle contraction, a characteristic involuntary muscular response will occur. This tells the anesthesiologist the needle tip is close enough to the nerve to inject local anesthetic.
Peripheral nerve catheters
Peripheral nerve catheters are inserted adjacent to peripheral nerves, such as the sciatic nerve, under ultrasound guidance. Like epidural injection, they allow repeated injection of local anesthetics and other drugs around peripheral nerves in patients and can be left in place for days as long as they are kept sterile. We can inject a high concentration of local anesthetic when the patient’s pain is severe, then decrease the concentration of local anesthetic as the patient recovers.
Subcutaneous catheters
In pigs, it can be difficult to maintain catheters for analgesic drug delivery in peripheral veins as we can in dogs or horses due to the thickness of their skin and subcutaneous tissue. We have pioneered the placement of subcutaneous (under the skin) catheters under ultrasound guidance in pigs – often inserted at the back of the neck – for delivery of drugs like opioids. These catheters are simple to place, well-tolerated by pigs, and can last for days or weeks.
Continuous rate infusions (CRI)
A continuous (or constant) rate infusion (CRI) is the continuous intravenous delivery of a specific amount of analgesic drug (e.g., micrograms of an opioid) each hour, rather than injecting the drug as a bolus every few hours. This technique produces more stable blood concentrations of the drug and thus, better analgesia. The rate can be increased or decreased depending on a patient’s needs. The drug is delivered precisely using a syringe pump or driver. CRIs are frequently used in patients under general anesthesia and in the Intensive Care Unit (ICU).
Intra-articular (joint) analgesia
The administration of analgesic drugs directly into the fluid in a joint (called synovial fluid) is an excellent method of providing analgesia in patients with acute, moderate-to-severe joint pain. This may occur due to surgery in the joint, joint infection (septic arthritis), or an immune-mediated process (immune-mediated polyarthritis). For instance, after joint surgery (commonly performed in dogs and horses), morphine and/ or local anesthetic may be injected. Like epidural injection, this provides long-lasting analgesia with minimal systemic effects.
For more information on intra-articular injections for osteoarthritis, see Chronic Pain Management.