CHAPTER 145 Acute Care of Soft Tissue Injuries Involving the Eyelids, Ears, and Face
The horse is prone to traumatic injury of the head. Environmental conditions, a heightened flight response, and equipment and tack used for horses all contribute to injury occurrence. Despite the impressive volume of bleeding and very concerned owners that often accompany horses with a head injury, few incidents are truly life threatening to the horse; depression fractures of the cranium, resulting in cerebral trauma, are one exception. However, an injury can have substantial impact on the horse’s athletic performance or appearance, and hence on its consequent value to the owner. Successful surgery of the head is facilitated by the region’s extensive blood supply and by close attention to surgical technique on the part of the surgeon. There is often limited soft tissue to work with, and wounds may be contaminated at the time of initial injury or when paranasal sinuses or nasal passages are penetrated. Wounds that are left to heal by second intention may appear cosmetically unacceptable because of scar contracture or tissue loss and attendant misshapen anatomic features. In some instances, chronic medical conditions (e.g., exposure keratitis when an upper eyelid laceration heals and contracts) can result from open-wound management.
Many surgical procedures of the head can be performed in the standing, sedated horse with complementary use of regional anesthesia. Numerous peripheral nerve blocks or topical infusions of local anesthetic can be used to facilitate analgesia, the descriptions of which are beyond the scope of this chapter. Horses with complicated and extensive lacerations requiring meticulous surgery or those that are head shy or fractious are best managed with general anesthesia. Surgical preparation of wounds on the head should be confined to use of povidone-iodine–based solutions or scrub and lavage or rinsing with sterile physiologic saline solution. Only povidone-iodine solution should be used in preparation of wounds near or involving the eye because scrubs and chlorhexidine-based products are harmful to the cornea. The eye and adjacent wounds can be lavaged with physiologic sterile saline or an ophthalmic irrigating solution. Administration of antimicrobials and nonsteroidal anti-inflammatory drugs should follow normal principles for acute wound care. Assurance of adequate tetanus prophylaxis is also necessary.
Blunt or sharp traumatic injury to the eyelids is common in horses. The larger upper eyelid is injured most commonly, and it has a more critical protective function for the eye, including blinking and tear film distribution. Loss of eyelid function can result in epiphora, exposure keratitis, corneal ulceration, conjunctivitis, and other complications. Prompt repair of eyelid lacerations is always indicated. The aim of surgical reconstruction is to preserve the anatomic integrity of the entire eyelid margin to the greatest possible extent. With this in mind, debridement of eyelid lacerations should be kept to a minimum. A tenuous, thin strip of torn tissue (e.g., a hanging eyelid fragment) should not be removed unless it is obviously dead; even a fragile blood supply may be sufficient to facilitate survival of the tissue and effective salvage of an eyelid margin.
Partial-thickness lacerations that do not involve the lid margin are gently debrided and closed in one or two layers with 3-0 to 5-0 suture. Absorbable suture is used for subcutaneous layers. Healing is usually uncomplicated, and return to full function of the eyelid can be anticipated. If scar contracture results in retraction of the eyelid margin from the globe, a blepharoplasty procedure (such as a Z-plasty) is necessary to restore normal function.
Full-thickness lacerations that involve the eyelid margin are more common and necessitate two-layer closure. Again, debridement of the wound margins should be very conservative to preserve the maximum possible amount of tissue and result in the best chance for normal functional outcome. The eyelid margin should be accurately realigned with a figure-of-eight, cruciate, or mattress suture using 4-0 to 6-0 absorbable suture material, with the knot protruding externally and distant from the margin, so it does not rub on the cornea. This suture can be preplaced before the deep-layer closure or placed after the deep layer closure. The deep, tarsal plate layer of the eyelid is closed in a simple continuous pattern with 5-0 or 6-0 absorbable suture that does not penetrate the conjunctiva. Lastly, the skin is carefully apposed, starting adjacent to the eyelid margin suture, with simple interrupted, 3-0 to 6-0 nonabsorbable sutures (Figure 145-1). No suture tags or knots should be able to contact the cornea. Blepharoplasty procedures are necessary with defects involving more than 30% to 40% of the lid margin tissue. Impaired eyelid function can be managed with temporary tarsorrhaphy or a third-eyelid flap to protect the globe. Injury to the cornea must be concurrently treated, and this may include placement of a subpalpebral lavage catheter for medication administration.
Figure 145-1 Eyelid laceration repair.
(From Dallap Schaer B: Vet Clin North Am Equine Pract 23:49-65, 2007.)