Fluid therapy – getting under the skin

When we think of fluid therapy we tend to think of oral electrolytes and intravenous fluids. But how often do we think of subcutaneous (s/c) fluids? For many of us this is a much under used way to provide addition fluids and electrolytes, but it’s worth considering. It easy to give, painless and can help significantly with mild dehydration.

Posted: 11 February 2019

Fluid therapy – getting under the skin


All animals are amenable to this, including rabbits, cats, ferrets, guinea pigs and mice. The opportunity to use s/c fluids are certainly there if you look for them.

When can you use s/c fluids?

It’s important to be aware that this approach is great for helping with mild dehydration or preventing dehydration in patients with chronic conditions such as renal failure. It isn’t however a safe way to treat shock or attempt diuresis. In these situations, the intravenous route is preferred.

What fluids can be used?

  • Lactated Ringers - probably the most effective fluid to use is Lactated Ringers (Hartmans). It’s a balanced crystalloid with the same osmolarity of our patients.
  • Avoid dextrose - glucose can sting when given by the s/c route, so should be avoided. It can also cause cellulitis and dermal necrosis.
  • Add potassium – this is important when treating cats for chronic renal failure. No more than 40mEq/l per litre bag. It’s also necessary to regularly monitor blood potassium levels.

How much and how often?

In reality, fluids can be given as often as is needed. This could be daily, on alternate days or even just once or twice a week.

The volume of fluid at each treatment is limited to what the animal will tolerate. For most cats and rabbits, between 50 and 150mls works best. Each animal will have to be assessed, and the volume adjusted and balanced against the benefit and frequency required.

Maintenance requirements are higher in rabbits and small mammals when compared to dogs and cats. This is due to their higher metabolic rates. As a guide, the maintenance fluids are as follows;

  • Cats – approximately 60mls/kg/day
  • Rabbits and ferrets - approximately 75 ml/kg/day or higher
  • Small rodent - approximately 100 ml/kg/day

What are the complications and limitations of s/c fluids?

Luckily, problems associated with repeated s/c fluid administration are uncommon. The procedure is generally safe, and many owners are, with a little training and reassurance, happy to learn and give this at home. In fact, in a recent study, 85% of owners said it was an easy/no stress/okay experience for them and 89% said it was an easy/no stress/okay experience for their cats, i.e. the majority of owners gave positive feedback. Some of the problems to look out for include;

  • Abscess – if you find a persistent, hard, warm swelling which is painful, it may be an abscess. Whilst you don’t generally need to clip and swab the skin when giving s/c fluids, you may occasionally find bacteria are introduced from a contaminated needle.
  • Ventral swelling – the fluids are usually given in the dorsal thoracic (scapular) region or the lateral chest. When larger volumes (100mls or more) are given, the slow absorption may allow gravity to move the fluids ventrally. This isn’t a problem as it will eventually be absorbed.
  • Contamination – great care must be taken by the owner when storing and using the fluids. Poor technique can cause the fluid and giving set to become contaminated. Minimise the risk by keeping unused fluids in the fridge, replacing the needle regularly and washing hands.
  • Accidental injection – pay particular attention to the site and direction of the needle. Poor placement may inadvertently introduce the needle into the thorax, abdomen or muscle. Client training is essential.
  • Cardiac overload – this is especially a problem in animals with heart failure if the fluid volume is too great. Measure the volume given accurately.
  • Hypokalaemia and hypernatraemia – this is always possible when fluids are given over a prolonged period. Make sure regular electrolyte measurements are taken, and if required, supplemental potassium is given.

Limitations – the rate of fluid absorption is the main restriction of using s/c fluids. It’s therefore not appropriate for hypovolemic or severely dehydrated patients and therefore only reserved for those with mild dehydration.

What’s involved?

In order to give the fluids, you’ll need a few consumables and measuring tools. Our suggestions include;

  • Fluid - 500mls bag of Hartmans/Lactated Ringers
  • Giving set and needle – an 18-22 gauge butterfly needle works well
  • Measuring facilities - accurate weigh scales (measure before and after to work out the volume delivered) or 100ml burette

Most cats and rabbits tolerate the process of being given s/c fluids extremely well, especially if the fluid is warmed first. It takes just a few minutes to give 60-100mls, so in almost all cases there is minimal stress. Keep the animal settled on something comfy, allowing someone to cuddle and stroke at the same time.

Share these videos

There are some very helpful YouTube videos which you could share with your clients to demonstrate how to give the fluids effectively.