What are the effects of a bite wound?
Local to the bite itself, you have all sorts of things to consider, such as;
- Tearing – surrounding tissues can be torn with variable results. A small skin tear would be minor, whilst a tear of muscle, blood vessels or nerves can have serious consequences. Some tissues may even be torn away from their normal attachments.
- Crush injury – the pressure that can be exerted by the carnassial teeth of a dog or cat can be extreme. Significant crushing trauma can occur to anything, including muscle and bone.
- Bruising - damage to blood vessels can cause bleeding under the skin, resulting in painful bruising.
- Haematoma and seroma – blood and serum can collect between tissue spaces, delaying healing and acting as a medium in which bacteria can grow.
- Necrosis – tissues can have their local blood supply compromised, which in turn can lead to anoxia and necrosis.
- Dead space – bite wounds often result in an unwanted dead space as a result of tissues being pulled apart. The dead space can fill with fluid, which delays the normal healing process.
- Infection - all bite wounds are usually heavily contaminated with bacteria from the skin, or more likely from the aggressor's mouth. The infection can be from both aerobic and anaerobic bacteria. Aerobic organisms include Staphylococcus intermedius, Enterococcus spp. and Escherichia coli., whilst anaerobic bacteria frequently isolated include Bacillus spp., Clostridium spp. and Corynebacterium spp.
- Hair and debris – foreign material can be forced into the wound by the teeth, creating a focus for infection.
- Oedema – the inflammation and fluid accumulation will frequently result in tissue oedema around the wound.
Whilst the majority of bite wounds are minor, there are some which can have some serious consequences if missed. Some of the systemic and potentially life-threatening problems include;
- Septic shock – this can develop extremely rapidly with fatal consequences. Have you read our article on sepsis?
- Hypovolaemic shock – significant blood loss can result in cardiovascular depression, so the patient should be carefully assessed. Fluid replacement is important, and the animal will need to be stabilised as soon as possible.
- Ocular damage – proptosis or a ruptured eye can be a devastating injury.
- Puncture of the chest wall – this can result in;
- rib fractures
- Penetration of the abdomen – bite wounds resulting in a puncture of the abdominal wall could potentially lead to;
- torn or ruptured spleen, liver or kidneys
- major haemorrhage
- rupture of the bladder
- damage to gastrointestinal tract resulting in peritonitis
- septic abdomen, usually a few days after the injury
Stabilise and treat – 11 top tips
When the animal is first seen, you’ll need to make some important clinical decisions. Stabilising the patient prior to dealing with the wound itself will always take priority.
- Fluids first - if the animal is in hypovolaemic shock, insert an intravenous catheter and give fluids as soon as possible. In most situations, colloids and blood transfusion are rarely required.
- Cover the wound – this is initially done using sterile swabs soaked in sterile isotonic solution.
- Pain relief – most traumatic bite wounds will be painful, so analgesics are important. Use opioids such as buprenorphine and non-steroidal anti-inflammatory drugs (but check the renal function first).
- Antibiotics - a broad-spectrum bactericidal drug may be indicated. Prior to giving the drugs, take samples for culture. Some cases may benefit from the antibiotics being given intravenously.
- Clean and suture the wound – in most cases this is best performed under sedation or a general anaesthetic, however always correct any hypovolaemia first. If the wound is being prepared for suturing several days after it first occurred, make a careful examination for any necrotic tissue, and remove if present. Infected wounds should not be sutured, as second intention healing will occur when the infection has resolved.
- Prevent contamination – when clipping a wound, carefully wipe away hair and debris with moistened sterile swabs. Sterile K-Y jelly can also be applied to the wound prior to clipping to prevent contamination.
- Flush the wound – flush a fresh wound with sterile isotonic solution such as saline or Hartmann's. Avoid solutions containing glucose as these can potentiate bacterial growth. Repeat the flushing daily.
- Dressings - debridement dressings (e.g. Allevyn) and gels (e.g. Intracite) should be used if the wound becomes infected or necrotic.
- Drains – when dead space is created, the insertion of a Penrose drain to allow fluid and debris to find its way out will aid healing. Occasionally you may find it necessary to use an active suction drain.
- Check for granulation tissue - once this is present, antibiotics can usually be stopped.