Wounds

Definition

A break or injury in the surface of the skin or the underlying tissues.

Clinical Signs

May observe any of the following:

Jagged or torn edges of skin or puncture marks depending on type of wound.
An opening of surgical incision.
Frank bleeding, or oozing, depending on type and depth of wound.
An abnormal discoloration (e.g., redness, bruising).
Tenderness or pain.
Wound site is warm to touch.
Swelling at / or surrounding wound site.
The presence of pus.
A foul odor (if wound infected).

Etiology

In any open wound, whether it is small or large, the principles for care remain the same: to prevent and reduce infection and to promote wound healing.

When wounds occur, the type or extent can result in a variety of effects such as: decreased mobility or loss of body part, blood loss, or bacterial contamination, or infection.

Wounds may be classified as being clean, contaminated, or infected. Wounds that are considered clean are those made under aseptic conditions such as surgical incisions made by a veterinarian. Contaminated wounds differ from infected wounds in that there is a lesser bacterial count present than with infected wounds. The cause of a wound, the degree of contamination and blood supply to the wound can be determining factors as to whether infection will develop.

Types of wounds are categorized based on the mechanism and depth of injury as follows:

Incised (incision) wounds are clean precise cuts that are primarily made by a veterinarian during surgery.
Wound dehiscence refers to post op surgical sites that have opened up on their own or through chewing or incessant licking of incision site or through chewing out of sutures, staples, or surgical adhesive.
Abrasions or scrapes are surface or superficial wounds. With these types of wounds, a small amount of oozing blood may or may not be seen and deeper tissues remain intact. Abrasions or scrapes may occur when rubbing up against rough edges in cages while rough-housing with cage mates or due to falls against rough objects.
Lacerations are wounds that go below the skin’s surface into deep tissue and sometimes include fat and/or muscle. The wounds often have jagged, irregular edges and bleeding is more profuse. Lacerations may occur due to falls, bites, or other incidents.
Puncture wounds are small openings in the skin produced by pointed objects such as teeth. Bleeding may be very minimal, and the wound, if small, may heal over quickly before the owner has a chance to notice. Heavier bleeding may also occur with a puncture wound. Fortunately, initial free bleeding will actually help clean the wounds. Puncture wounds are often the result of bites.
Bite wounds can be either puncture wounds, lacerations, or a combination of both. Wounds such as these are always considered contaminated and tend to require more care, especially if they are extensive. Small bite wounds can sometimes heal before they are noticed, however, due to the bacteria involved, they can become abscessed.

In wound healing vasoconstriction (constriction of the blood vessels) occurs as soon as the wound occurs. It is followed by vasodilation (dilation of the blood vessels) resulting in the redness and swelling that is seen below the epithelium. Next, epithelial cells start to migrate, and fibrin (which helps in clotting) starts to layer in the wound. The area of the wound with the greatest amount of stress on it will be fortified with collagen as healing takes place.

Keeping the rat’s environment and the wound site clean will help to enable healing and prevent or reduce the chance of infection.

Figures

Case Histories of Wounds In Rats

Abrasion / Puncture Wounds

Fig. 1: Abrasion / puncture wound to hind foot involving MRSS (methicillin-resistant Staphylococcus schleiferi) in 18-month-old female rat (Silky)

Bite Wounds

Fig. 1: Bite wound to scrotum in male rat (Cricket)
Fig. 2: Bite wound to muzzle in adult male rat (Silky)
Fig. 3: Bite wound to nose in a 3-month-old female rat (Nunu)
Fig. 4: Bite wounds and resolving hematoma in a 1-year-old female rat (Pigg)
Fig. 5: Bite wound to right leg, during introductions, in 6-month-old female rat (Luna)
Fig. 6: Bite wound to neck, during introductions, in 4-month-old female rat (Phi-Adara)
Fig. 7: Bite wound to ear, during introductions, in female rat (Yasmine)

Wound Dehiscence

Fig. 1: Post op wound dehiscence in female rat (Sneaker)
Fig. 2: Wound dehiscence following mammary tumor removal in female rat (Katinka)

Diagnostics

Stabilize rat
Obtain history of injury from pet owner
X-ray may only be necessary if wound extensive
Examine area surrounding wound for any damage done to underlying tissues

Treatment

The first consideration in treatment is to treat any life-threatening issues and to ensure that the rat’s condition is stabilized.

In the event of uncontrolled bleeding or gaping wounds, apply even, direct pressure to the wound with a clean cloth to control bleeding, wrap rat in towel or blanket to maintain normal body temperature, and seek emergency veterinary care immediately.

For rats suffering from shock: provide oxygen, and warmed SQ or IV fluids. If deemed appropriate, consider administering dexamethasone.

Once the rat is stabilized, assess type and extent of wound. Cleanse or irrigate wound with either normal saline, 1% chlorhexidine solution diluted with water to the color lighter than a robin’s egg blue or 2% chlorhexidine solution diluted 1:40 (1 part chlorhexidine to 40 parts water), or Betadine solution diluted 1:5 (1 part Betadine to 5 parts water), or non-abrasive soap and water. Cleansing with hydrogen peroxide is not necessarily recommended as it can result in damage to healthy tissue and delay the healing process.

In most cases minor cuts and abrasions, if cleansed initially and kept clean, will heal on their own without the need for surgical intervention. However, uncared for wounds that are several hours old along with bite or puncture wounds, which are all considered contaminated or infected, may also be cleansed and allowed to granulate and heal on their own without surgical intervention.
The decision, by a veterinarian, to close a wound with sutures, staples, or surgical adhesive will depend on the location of the wound on the body, the extent of damage, and degree of contamination. In rare cases, where a contaminated or infected wound is deep into muscle or fat the wound may be debrided, a drain inserted temporarily (to allow for drainage of pus), and sutures used to close the wound.

In the event of bite wounds, puncture wounds, or deep lacerations, or where the wound is believed to be contaminated, a broad-spectrum antibiotic (e.g.; cephalosporin, or trimethoprim/sulfa, or Clavamox, or enrofloxacin) should be initiated. Treatment of wounds penetrating the GI tract or oral cavity may also need to include metronidazole.

Where pain or discomfort is a factor, analgesics or pain relievers such as meloxicam or ibuprofen may be given. Do not give if the rat is receiving corticosteroids. An alternate choice would be Tylenol.

*Note: It is important to remember to wash your hands with soap and water before, and after, wound care. This will help to prevent introducing any further contamination into the wound and protect you, too!

Incisions

These precise cuts primarily made during surgery should be kept clean and dry. However, if external suture material has been used and there is drainage or crusting the area may be cleaned with a clean cotton swab (Q-tip) dampened (not dripping) with clean water or normal saline.
For post op incisions that have pulled apart (wound dehiscence), depending on length of time post op that the wound opened and the depth of the wound, the veterinarian may elect to cleanse and re-close with alternative suture material, and apply a body wrap to prevent the rat from accessing the site.
Post op incisions that have opened after a period of time, are not extensive and still have viable tissue, may benefit from the application of topical Silvadene (antibacterial, antifungal) where deemed appropriate.

Where the rat continues to pull out sutures or open the wound, or where healing is poor or delayed due to the presence of pus or maceration, the use of hydrogels (e.g., Intrasite), or gentle packing of granulated sugar or medicinal honey into the wound to prevent adherence of bacterial growth and promote granulation of the tissue for healing may be a choice of treatment.

An oral antibiotic is recommended in this circumstance.

Abrasions

Cleanse wound with normal saline or non-abrasive soap and water.
Remove any foreign particles that may have stuck to wound.
Apply topical antimicrobial (e.g., Polysporin or Bacitracin) sparingly.
Cleanse and apply topical daily or more frequently if contaminated.

Contusions

Apply a cold pack to the affected area.
Contact your veterinarian if you observe swelling, limited movement, discoloration, or signs of pain.

Caring for Lacerations, Puncture Wounds, or Bites

Commonly Used Irrigating Solutions

Normal saline
- Sterile normal saline may be obtained through a veterinarian.
- An over-the-counter normal saline wound wash (e.g., Blairex).
- Homemade sterile saline solution for wound cleansing made with the following:
  - 16 ounces water (use distilled if your tap water is hard)
  - 1 teaspoon table salt
  - You can use warm water, or you can boil the solution then cool to room temperature before use.
    *Note: boiling is usually not necessary when flushing a non-sterile wound such as an abscess.

A 1% chlorhexidine solution diluted with water to the color lighter than a robin’s egg blue.
A 2% chlorhexidine solution diluted 1:40 (1 part chlorhexidine to 40 parts water).
Betadine solution diluted 1:5 (1 part Betadine to 5 parts water).
The use of non-abrasive soap and water.

Lacerations

Control bleeding by applying direct even pressure with a clean cloth.
Inspect the wound for depth and degree.
Cleanse the wound with one of the above irrigating solutions once or twice daily, or as directed by veterinarian.
In the event laceration is deep the vet may be required to close the wound using sutures, staples, or surgical adhesive.
Topical antimicrobial may be indicated. *Note: if surgical adhesive is used, a topical antimicrobial may cause adhesive to loosen.
In the event wound contamination is a factor a broad-spectrum antibiotic may be appropriate.

Punctures

Irrigate, or cleanse wound with one of the above irrigating solutions once or twice daily, or as directed by veterinarian.
In the event wound contamination is a factor or the puncture is believed to be from a bite a broad-spectrum antibiotic should be initiated.

Bite wounds

Control the bleeding by applying pressure with a clean cloth.
Inspect the wound for depth and degree.
Irrigate, or cleanse the wound with one of the above irrigating solutions once or twice daily, or as directed by veterinarian.
Initiate a broad-spectrum antibiotic.

In the event of abscess development refer to the Abscess article in the Health section of the Rat Guide.

For information regarding medications refer to the Rat Medication Guide.

Nursing Care

For open wounds, or for wounds that require sutures, provide clean bedding daily such as cloth or paper towels. Avoid loose or shredded bedding to minimize wound contamination and infection.
Check the wound site daily and cleanse as directed.
Maintain a clean cage environment.
Apply any antimicrobial topical agents or oral antibiotics as prescribed.
Observe for and follow-up with veterinarian if any of the following presents:
1. Any redness that extends from the wound after 2 days.
2. If there is yellow or purulent drainage from the wound.
3. If there is increased swelling or limited movement.

Outcome

Wound healing without signs of infection
No mobility impairment
Pain resolved

Prevention

Consider the risk of lacerations / punctures which may result from falls or colliding with structures or sharp objects within cages.
Care should be taken when first introducing new rats to a cage environment with existing rats to reduce the risk of bullying or territorial fight wounds.
Always supervise your rat’s interaction with other pets.
Be sure that cage bar spacing is appropriate for the rat’s size to prevent escape.

References

Abstracted from wound management using sugar. (2002, March 1). Veterinary News. Retrieved December 22, 2008, from http://vetextension.psu.edu/resources/newsletters/pdf/VNMar02.pdf.
Langlois, I. (2004). Wound management in rodents. Veterinary Clinics of North America: Exotic Animal Practice, 7(1), 141-167. doi:10.1016/j.cvex.2003.08.004 Retrieved June 1, 2017, from https://secure.jbs.elsevierhealth.com/action/getSharedSiteSession?rc=8&redirect=https%3A%2F%2Fwww.vetexotic.theclinics.com%2Farticle%2FS1094-9194%2803%2900072-0%2Freferences
Mandal, M. D., Mandal, S. (2011, April). Honey: its medicinal property and antibacterial activity. Asian Pacific Journal of Tropical Biomedicine, 1(2), 154-160. doi:10.1016/s2221-1691(11)60016-6. Retrieved June 01, 2017, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3609166/
Mathews, K. A., Binnington, A. G. (2002). Wound management using sugar. Comp Contin Educ Pract Vet., 24, 41-50. Retrieved June 1, 2017, from http://www.hungarovet.com/wp-content/uploads/2007/08/wound-management-using-sugar-2002.pdf
Smeak, D. D. (2006, January 11). Wounds: the scoop on sugar. In Proceedings of the North American Veterinary Conference Volume 20. Retrieved June 1, 2017, from http://www.ivis.org/proceedings/navc/2006/SAE/529.pdf
Winkler, K. P. (2016). Initial wound management – emergency medicine and critical care. In Merck Veterinary Manual. Retrieved June 1, 2017, from http://www.merckvetmanual.com/emergency-medicine-and-critical-care/wound-management/initial-wound-management