Page 535 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 501

Due to the common inability to control digital pain the digits in the ice slurry, most clinicians maintain
with a safe dosing of NSAIDs, CRI of analgesic drugs animals at risk of SRL in ice for 24–48 hours past the
VetBooks.ir ing the level of pain suffered by hospitalized laminitis
abatement of clinical signs of sepsis.
has been used to supplement NSAID therapy in decreas-
patients. The use of “Pentafusion” (combination of keta-
mine, morphine, lidocaine, detomidine, and aceproma- Hoof Care in the Treatment of Acute and Early
Chronic Laminitis
zine; Eric Abrahamsen, BEVA Proceedings, 2005) has
been described for use in severely painful cases of lami- In the acute and early chronic laminitis case, it is
nitis. The CRI is a valuable addition to laminitis therapy likely that lamellar instability remains a prominent fac-
because it takes some of the humane concerns away tor. Ideally, in horses with severe acute and early chronic
from the owner and veterinarian treating an animal in laminitis, the force of the horse’s weight on the feet
severe pain. Some of these drugs also affect GI motility; should be reduced. To this end, slings have been used to
therefore, the animals must be monitored closely for enforce partial weight‐bearing, but availability and
large intestinal motility/impaction. Additionally, the ani- inadequate tolerance by the horse frequently result in
mals may become unstable or overly sedate if the CRI failure of this effort. Therefore, many treatment meas-
rate is excessive. For a more focused approach, an epi- ures are aimed directly at the foot. The two main objec-
dural can be considered for analgesia in hindlimb tives of hoof care are to redistribute the force of
laminitis. weight‐bearing away from the hoof wall and to decrease
the extensor moment about the DIP joint.
Several measures of varying efficacy attempt to redi-
Therapy to Limit Structural Failure of the Lamellae
rect weight‐bearing away from the wall by recruiting the
The obvious overarching goal of therapies for the frog, bars, and all or part of the sole to bear weight.
horse at risk of or suffering from laminitis is limiting the However, as discussed in Chapter 8, it must be remem-
structural failure of the lamellae. The only therapy to bered that the physiological role of the sole in weight‐
consistently inhibit—or limit—lamellar structural fail- bearing is not fully understood. The amount of the
ure in both the research and clinical setting is digital ground surface that can be recruited to bear weight is
hypothermia (also termed cryotherapy). 19,25,41 Although highly variable between horses. In general, once the
original work demonstrating efficacy of hypothermia distal phalanx has displaced, pressure over the sole
maintained the horses’ forelimbs in an ice/water slurry under the displaced distal phalanx increases discomfort.
to the level of the carpus, more recent work has dem- Thus, the clinician must weigh the benefits of possibly
20
onstrated that immersion of the foot up to the level of decreasing lamellar stress by applying solar support
the pastern region is adequate to keep the hoof tempera- with the risk of causing excessive solar pressure and
ture less than 10 °C. Although many clinicians use 5‐L worsening the pain (and possibly the pathologic pro-
18
intravenous fluid bags taped to the limbs to maintain cess). Before considering other measures, the clinician
the digits in the ice slurry, commercial alternatives exist must decide whether to leave shoes on the feet if the
(e.g. Ice Spa Pro, Soft‐Ride, Inc.). Continuous hypother- horse is shod. Shoes on firm surfaces concentrate stress
mia in this manner has been demonstrated to protect the around the perimeter of the foot (e.g. the hoof wall and
lamellae from structural failure even when hypothermia lamellae), and therefore removing them will likely be
is not initiated until the onset of lameness. Although beneficial by removing this effect. Removing shoes also
25
most experimental studies demonstrating efficacy of makes other therapeutic measures more feasible, includ-
digital hypothermia have been performed in models of ing recruiting other parts of the ground surface of the
SRL, the same protective effect was recently demon- foot for weight‐bearing and modifying break‐over. The
strated to occur when hypothermia was assessed in EHC potential disadvantage of removing shoes in horses with
model of endocrinopathic laminitis (Belknap and van laminitis is that the removal process itself may cause
Eps, unpublished data). In the clinical setting, digital additional trauma to the lamellae.
hypothermia is most commonly used as a prophylactic The simplest way to recruit the sole, frog, and bars
therapy in the septic equid at risk of laminitis. In a mul- for weight‐bearing is to place the horse on bedding
ticenter retrospective clinical study of the use of digital material that readily conforms to the shape of the foot.
hypothermia as a prophylactic therapy against laminitis In this regard, sand is significantly better than shavings.
in 130 equine enterocolitis cases, horses treated with Peat has also been used. Deep deformable substrates
digital hypothermia were ten times less likely to develop also permit the horse to adjust the angle of its foot to
41
laminitis than those not treated with hypothermia. In optimize comfort. However, the deep deformable sub-
that study, there was a trend for a worse prognosis if strates are not selective in how pressure is applied to the
hypothermia were used intermittently than if not used at ground surface of the foot. Various devices and materi-
all (S. Holcombe, personal communication), indicating als have been placed under the frog, sole, and bars to
that it is very important that the digits need to be con- recruit varying amounts of weight‐bearing. These
tinuously maintained in the hypothermic state. Although include rolled gauze, Lilly pads, silicone putty, Styrofoam
it varies between animals, ice usually needs to be replen- insulation board (usually 2‐inch board), closed cell foam
3
ished every 1–2 hours to maintain the hypothermic (1.5 inches thick, 4 lbs/ft density), and commercial pad
state. Many practitioners only maintain the front digits systems such as the Soft‐Ride boots (Soft‐Ride, Inc.,
in ice due to the increased incidence of laminitis in the Vermillion, OH). The closed cell foam has the advan-
forelimbs; however, it is best to maintain all four limbs tages of not crushing like Styrofoam does, and it can be
in ice if possible. Although no studies have been per- cut to bevel the ground surface to move the break‐over
formed to ascertain the optimal time period to maintain palmarad. The softer materials may offer the additional