10–20 μg/kg/minute
Box 1.2 Fluid Therapy Prescription Formula
This formula incorporates fluid deficit (dehydration), ongoing losses, and maintenance fluid needs. It should be used only after intravascular volume deficits (hypovolemic shock) have been corrected.
Rate of deficit correction is generally over 12–36 hours depending on patient stability, chronicity of dehydration, and tolerance for IV fluids.
Maintenance needs are generally 2–3 ml/kg/hour for dogs and 1–2 ml/kg/hour for cats.
Example Fluid Prescription Calculation
25 kg mixed breed dog (lean body condition)
Estimated to be 8% dehydrated based on physical exam findings (tacky mucous membranes, prolonged skin tent, slightly sunken globes, hyperviscous saliva in the corner of the mouth).
No conditions that would make the patient fluid intolerant; plan to correct over 24 hours.
The dog is losing approximately 60 ml in vomit every hour, no excessive gastrointestinal or urinary losses.
Deficit = 0.08 × 25
Deficit = 2000 ml
Rate of deficit correction = 2000/24 = 83 ml/hour
Fluid prescription (per hour) = 83 ml (deficit) + 60 ml (losses) + 50 ml (maintenance)
Fluid prescription = 193 ml/hour
Electrolyte monitoring should be performed routinely (Table 1.2) in patients with dehydration and shock. This is particularly true in anorexic patients or those with renal dysfunction, which may require supplementation with potassium and/or phosphorus. Additionally, as many fluids used in veterinary medicine are designed as “replacement” and not “maintenance” fluids, sodium values may increase in patients receiving prolonged intravenous fluid therapy, particularly in patients with continued free water loss, such as renal, gastrointestinal, skin, and respiratory loss. Fluids with lower sodium concentrations such as Normosol‐M, 0.45% NaCl, and dextrose 5% in water (D5W) may be necessary to prevent or manage hypernatremia associated with prolonged fluid therapy and/or concurrent hypotonic fluid losses.
Table 1.2 Monitoring parameter guidelines and frequencies for dehydrated patients and those in hypovolemic, distributive, and hypoxemic shock.
| Physical assessmenta | Blood pressure | SpO2 | Urine output/specific gravity | PCV/TS/BG/Azo Stick® | VBG/ABG/electrolytes | |
|---|---|---|---|---|---|---|
| Dehydrationb | 8–12 hours | 8–12 hours | 12–24 hours | 8–12 hours | 12–24 hours | 12–24 hours |
| Hypovolemic shock | 1–2 hours initially, then 4–6 hours once stabilized | 1–2 hours initially, then 4–6 hours | 4–6 hours | 4–6 hours | 4–6 hours initially, then 6–8 hours | 4–6 hours initially, then 6–8 hours |
| Distributive shock | 1–2 hours initially, then 4–6 hours once stabilized | 1–2 hours initially, then 4–6 hours | 4–6 hours | 4–6 hours | 6–8 hours | 6–8 hours |
| Hypoxemic shock | 1–2 hours initially, then 4–6 hours once stabilizedc | 2–6 hoursc | 1–4 hoursc | 4–6 hoursc | 12–24 hours and after pRBC transfusionc | 12–24 hoursc |
a Physical assessment parameters include hydration evaluation, mucous membranes, capillary refill time, respiratory rate and effort, cardiac and thoracic auscultation, pulse quality, and temperature.
b Dehydrated patients should also be weighed every 8–12 hours.
c Frequency of diagnostics will depend on patient stability and amount of stress caused to the patient with handling, evaluation, and blood sampling.
ABG, arterial blood gases; BG, blood glucose; PCV, packed cell volume; SpO2, peripheral capillary oxygen saturation; TS, total solids; VBG, venous blood gases.
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