Veterinary Nursing: Managing Vomiting, Diarrhea, and Anorexia in Animals

Dehydration and Electrolyte Imbalance

As fluids are lost, the animal's internal environment becomes unstable. Key imbalances include:

• Hyponatremia: Low sodium levels, which is considered very serious.
• Hypokalemia: Low potassium levels. This is particularly dangerous because it can subsequently lead to anorexia.
• Chloride Imbalance: Affects the body's ability to maintain fluid balance.
• Sodium: Essential for nerve function and muscle contraction.

Beyond electrolytes, patients are at risk for acid-base imbalances and aspiration (inhaling gastric contents into the lungs).

Anorexia and Hepatic Lipidosis

Anorexia is the lack or loss of appetite. When an animal stops eating, it begins to catabolize (break down) its own body tissues for energy. This leads to weight loss, a decreased immune response, and impaired healing.

In cats, prolonged anorexia is especially dangerous due to the risk of hepatic lipidosis. Because cats mobilize fat stores for energy, their livers may become overwhelmed and unable to process the fat efficiently, leading to fat accumulation within the liver organ.

Management and Treatment

The primary goals of treatment are to remove the initiating cause, control symptoms, and correct physiological deficits.

Fluid Therapy

If an animal is more than 5% dehydrated, or if they are losing fluids faster than they can be replaced, IV fluids are required to correct dehydration and electrolyte/acid-base imbalances.

Dietary Management and Reintroduction

To allow the gastrointestinal (GI) tract to rest, food may be withheld initially. Once the patient is stable, food should be reintroduced over 3–5 days using highly digestible, bland, or prescription intestinal diets (e.g., Hill's I/D).

The food transition period should last approximately one week to return the animal to their regular diet. A common method is a gradual ratio shift:

Critical Note: If diarrhea recurs during this transition, you must slow down. Return to the previous successful feeding stage and remain there until the stool firms up before attempting to increase the regular diet again.

Anorexia Intervention and Enteral Nutrition

If an animal refuses food, nurses may use appetite stimulants (such as Mirtazapine), force-feeding via syringe, or enteral nutrition. Enteral nutrition involves placing tubes to deliver food directly into the digestive tract:

1. Nasoesophageal tube: A small tube placed through the nostrils to the stomach.
2. Esophagostomy tube: A tube placed surgically into the esophagus.
3. Gastrostomy tube (PEG): A tube surgically placed directly into the stomach.

Clinical Calculations

When managing nutrition, nurses must calculate the Resting Energy Requirement (RER) to determine how many kilocalories (kcals) the patient needs per day.

The formula for RER is: $\text{RER} = (30 \times \text{body weight in kg}) + 70$

Example Calculation: For a 3kg cat being fed Hill's A/D (which contains 1.3 kcals/ml):

1. Calculate RER: $\text{RER} = (30 \times 3\text{ kg}) + 70 = 160\text{ kcals/day}$
2. Calculate daily food volume: $\text{Food per day} = \frac{160\text{ kcals}}{1.3\text{ kcals/ml}} = 123\text{ mls/day}$

Additionally, water requirements are calculated based on RER:

• Dogs: $\text{RER} \times 1.6 = \text{mls of water needed}$
• Cats: $\text{RER} \times 1.2 = \text{mls of water needed}$