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August 2024
2024 AAHA Fluid Therapy Guidelines for Dogs and Cats
Selected highlights from the 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats
The AAHA Fluid Therapy Guidelines for Dogs and Cats offer an overview of the body’s fluid dynamics and provide practical recommendations for selecting fluids, calculating administration rates, and choosing administration routes in dogs and cats for the purposes of resuscitation, rehydration, and maintenance. The guidelines also cover fluid therapy recommendations for anesthetized patients, patients with common conditions, and those with disorders presenting special fluid therapy challenges. Additionally, the guidelines detail patient monitoring parameters, highlight methods to prevent fluid overload, describe fluid delivery options, and address controversies and misconceptions in fluid therapy.
The following pages provide highlights from the new Fluid Therapy Guidelines and examples of how to use the guidelines in practice, including:
- The Guidelines at a Glance
- Fluid Therapy Treatment Algorithms
- How to Use These Guidelines: Sasha’s Case
- 6 Tips for Cats from the Fluid Therapy Guidelines
For more information, refer to the guidelines at aaha.org/fluid-therapy. There you’ll find a downloadable copy of the guidelines as well as resources, algorithms, tables, charts and frequently asked questions.
The 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats are endorsed by the American Association of Feline Practitioners.
Fluid Therapy Treatment Algorithms
The Guidelines in Action
Case Study: Fluid Therapy for Gastrointestinal Disease
Adesola Odunayo, DVM, MS, DACVECC and Ewan Wolff, DVM, PhD, DACVIM (Small Animal Internal Medicine)
Sasha, a 5-month-old, mixed-breed dog weighing 10 kg was presented for evaluation of vomiting and diarrhea of three days duration.
Physical Examination Results:
- Abdominal pain
- Tachycardia, heart rate = 200 beats/minute
- Weak peripheral pulses
- CRT = 3 seconds (normal <2 seconds)
- Estimated 6% dehydration
Clinical Pathology Results (complete blood count and serum chemistry profile):
- Panleukopenia
- Hypoglycemia, blood glucose 60 mg/dL (normal = 68–104 mg/dL)
- ELISA test for parvovirus = positive
- Hypotension, systolic blood pressure = 70 mm Hg (normal = 90–140 mm Hg)
- Increased blood lactate = 4 mmol/L (normal <2.5 mmol/L)
What is Sasha’s fluid therapy plan?
1. Treat hypovolemic shock
Sasha’s clinical signs indicate shock or poor perfusion (tachycardia, weak peripheral pulses, prolonged CRT). Sasha’s history of vomiting and diarrhea indicates a likely component of hypovolemia leading to shock, although vasodilatory shock may also be present. Shock is life-threatening, so address this first by rapidly expanding the intravascular space with fluids, also called fluid resuscitation.
Several options for fluid therapy are available, including isotonic crystalloids, hypertonic saline, natural or synthetic colloids,* or a combination of these. No conclusive evidence supports the superiority of one fluid type over another in the treatment of shock. In Sasha’s case, isotonic crystalloids were chosen for her resuscitation.
The plan:
- 20 mL/kg bolus of Plasma-Lyte A administered IV over 15 minutes
- Abdominal pain treated with a pure mu opioid (methadone)
Reassessment:
- Heart rate = 170 beats/minute
- CRT = >2 seconds
- Systolic blood pressure = 85 mm Hg
Slight improvement noted but perfusion parameters have not normalized.
Repeat bolus:
- A second 20 mL/kg bolus of Plasma-Lyte A was administered over 15 minutes
- 0.5 mL/kg (5 mL) bolus of 50% dextrose, diluted 1:2 with 10 mL of saline administered intravenously through a peripheral catheter to address hypoglycemia
Reassessment:
- Heart rate = 110 beats/minute
- Femoral pulses = strong
- CRT = 2 seconds
- Systolic blood pressure = 110 mm Hg
- Blood lactate concentration = 2 mmol/L
Sasha’s normalized perfusion parameters indicated improved oxygen delivery and resolution of shock. Sasha was monitored closely over the next 24 hours to ensure that her perfusion and volume status remained within normal ranges.
If Sasha had not responded to fluid therapy, vasopressors would have been indicated.
2. Correct dehydration
Once Sasha has been fluid resuscitated, a fluid therapy plan for rehydration (interstitial space deficit) was initiated. Administering arbitrary volumes (1.5×, 2×, 3× the maintenance rate) may result in ineffective therapy or overhydration, so the rehydration plan was based on the estimated percent dehydration identified by physical examination.
Calculate the fluid deficit:
Fluid deficit (L) = % dehydration × weight in kg
Fluid deficit (L) = 0.06 × 10 kg
Fluid deficit (L) = 0.6 L or 600 mL
Because Sasha had no contraindications for rapid treatment of dehydration (e.g., heart disease, low protein concentration, kidney disease), her fluid deficit was replaced over 12 hours, or 50 mL/hr IV for the next 12 hours with Plasma-Lyte A.
3. Provide maintenance water requirements
Sasha’s daily maintenance water requirement was estimated to be about 100 mL/kg/day (or 42 mL/hr) and was met with isotonic crystalloids until Sasha started eating and drinking on her own. As a growing puppy, Sasha had a slightly higher maintenance water requirement.
Sasha’s maintenance water requirement was added to the fluid deficit rate for a final rate of 92 mL/hr for the first 12 hr using Plasma-Lyte A. After 12 hr, the fluid rate may be reduced to 42 mL/hr or 100 mL/kg/day, if Sasha has no significant ongoing losses. Sasha’s hydration status was assessed multiple times during hospitalization and her fluid rate was adjusted as needed.
Because large fluid volumes were needed to treat dehydration and provide maintenance, dextrose was supplemented in the Plasma-Lyte A as a 1.25% solution. Sasha’s serum glucose concentration was closely monitored during hospitalization and the dextrose concentration adjusted based on response to therapy.
While Sasha’s potassium was normal (3.9 mEq/L) on presentation, it was expected to decrease because of ongoing anorexia and the use of large volumes of potassium-poor fluids. KCl was supplemented at 0.05 mEq/kg/hr (0.5 mEq/hr). Based on a fluid rate of 92 mL/hr, this amounts to about 5.5 mEq/L of KCl added to the Plasma-Lyte A bag. The amount of KCl added to the fluids may be adjusted depending on changes in Sasha’s serum potassium concentration, which was checked every 24–48 hr.
Fluids supplemented with KCl should never be administered as a bolus, so if Sasha requires a fluid bolus during hospitalization, the fluids must not contain a KCl supplement.
4. Treat ongoing losses
During Sasha’s hospitalization, it was important to consider the possibility of substantial and continuous volume losses, such as from gastric residual volumes, diarrhea, or vomiting. The ongoing losses are either measured (gastric residual volumes) or estimated (vomiting, diarrhea) and then replaced using isotonic crystalloids.
Sasha had about 100 mL of fluid loss from vomiting. The Plasma-Lyte A administration rate was increased by 25 mL/hr for the next 4 hr. After 4 hr, Sasha was re-evaluated for additional ongoing losses, and the fluid rate adjusted as indicated.
Another consideration for Sasha is the potential need for colloid therapy (e.g., plasma, canine albumin, etc.) related to hypoalbuminemia. While this is not frequently needed in dogs with parvovirus, it should be considered when albumin concentration is below 2 g/dL, and the patient is not making significant clinical improvement. Additionally, colloid therapy should be considered in patients with signs of peripheral edema or hypotension in the presence of hypoalbuminemia.
5. Offer nutritional support
Nutrition is an important part of managing canine parvovirus. Place a nasogastric or nasoesophageal tube as early as possible during hospitalization and initialize nutrition therapy after serum electrolyte abnormalities and poor perfusion are treated. Liquid diets are largely composed of water, so the volume of diet provided through the tube should be considered as part of the patient’s total fluid requirement.
6. Consider other treatment options as needed
Sasha may have been treated as an outpatient if she had no signs of shock. In that case, subcutaneous fluids (approximately 20 mL/kg) may have been administered, as well as other supportive therapy for canine parvovirus. The client may also be taught how to administer subcutaneous fluids at home or instructed regarding oral rehydration protocol for parvovirus.
* For a discussion of the risks associated with synthetic colloids, see the AAHA Fluid Therapy Guidelines for Dogs and Cats at aaha.org/fluid-therapy.
Additional Reading
Mylonakis ME, Kalli I, Rallis TS. Canine parvoviral enteritis: an update on the clinical diagnosis, treatment, and prevention.
Vet Med (Auckl). 2016;7:91-100. Published 2016 Jul 11. doi:10.2147/VMRR.S80971
Pardo M, Spencer E, Odunayo A, et al. AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024;60():60:131-163. doi: 10.5326/JAAHA-MS-7444.
6 Tips for Cats from the AAHA Fluid Therapy Guidelines
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