Many horses that develop laminitis aren’t euthanized as a direct result of the lamellar changes, but rather due to the uncontrollable pain associated with the inflamed and separated tissues. While we all have our preferred medications to help manage pain, which of these therapies actually have any scientific merit backing their use?
During the 2020 Virtual AAEP Convention, Katherine Ellis, DVM, from the Gail Holmes Equine Orthopaedic Research Center at Colorado State University, said, “Pain management is undoubtedly challenging, and a multimodal approach is necessary. While evidence is lacking specific to pain management in laminitic horses, many options are still available.”
Types of pain that veterinarians need to treat include the following:
- Inflammation of the laminae;
- Increase pressure within the rigid hoof capsule;
- Tearing of the soft tissues;
- Excessive contact between the sole and P3; and
- Neuropathic pain.
“When pain is uncontrolled, maladaptive pain can develop, which has no value to the animal,” relayed Ellis.
Using a case-based approach, Ellis reviewed the available evidence for various therapies.
Case 1: Grain Overload
Horses are commonly administered phenylbutazone, which is anecdotally the most popular NSAID for treating laminitis. Studies specifically showing the efficacy of phenylbutazone for laminitic pain are lacking. Other studies have suggested that different NSAIDs, such as flunixin, ketoprofen or firocoxib, might be more effective than phenylbutazone for pain management.
“If a horse is not responding to one NSAID then it might be of value to try a different NSAID,” advised Ellis.
Vasodilators such as pentoxiphylline or acepromazine have no evidence supporting their use in horses with laminitis and, importantly, do not have any analgesic effects.
“In contrast, controlled hypothermia [for treating acute laminitis] has been well studied,” Ellis noted.
Submerging the distal limb in an ice bath or boot for 48-72 hours significantly decreases lamellar injury and pain. But these beneficial effects are only observed if hypothermia is applied continuously, which is labor intensive and not possible for many clients in the field.
Case 2: Chronic Laminitis in a Horse with PPPID
The horse, suffering a flare up, was treated with 2 grams of oral bute, but it has not improved like last time. Further, the horse is sensitive to light touch over the back—a sign of central desensitization (maladaptive pain).
For the central desensitization, studies say that gabapentin might be helpful. However, higher doses (20 mg/kg) are often needed.
Further, adjunct therapies to consider include 1) TENS, with evidence in painful human conditions only); and 2) acupuncture, which anecdotal studies report decreased pain with two treatments one week apart.
Physical therapies such as massage, chiropractic and physical therapy might be attempted to help treat the secondary pain that often occurs within the horse’s axial skeleton (i.e., neck, back and pelvis)
Case 3: Hospitalized Patient with Supporting Limb Laminitis
This horse underwent pastern arthrodesis and subsequently developed support-limb laminitis in the contralateral limbs.
“Evidence supports the administration of opioids such as morphine and butorphanol. Considering the adverse events associated with systemic opioids, these can instead be used as local blocks. Fentanyl patches can also be applied,” Ellis said.
Tramadol (10 mg/kg) can be used, but it has been associated with colic. When administered in combination with a ketamine continuous rate infusion (CRI) the dose of tramadol can be decreased to 5 mg/kg PO q 8 hr to minimize chances of colic.
Additional therapies can include local anesthetics, such as a lidocaine (administered as a CRI) or mepivacaine/bupivacaine (administered locally at the nerves that innervate the foot). A newer product that releases bupivacaine slowly (liposomal bupivacaine) has been studies in horses, but it is not currently labelled for use in the horse.
Further, oral acetaminophen can be considered as well as biologics such as stem cells and platelet-rich plasma (PRP). Biologics can be predominantly used for its anti-inflammatory properties either as IV region limb perfusions or directly injected into the coronary band.
Using the above-described options in various combinations can help gain control over a laminitic horse’s pain while the tissues heal as best they can.