InfusionFox
Electrolytes & Fluids

Hypokalemia / KCl supplementation

IV potassium supplementation for hypokalemia in dogs and cats. Enter serum K and body weight; returns a KCl-supplemented fluid rate sized to the deficit and capped at the 0.5 mEq/kg/hr ceiling that prevents iatrogenic cardiac arrhythmia. Reserve for patients in whom oral repletion is inadequate, impossible, or too slow.

  • 0.5 mEq/kg/hr ceiling. KCl IV infusion above this rate risks cardiac toxicity. The maximum pump rate shown is the highest rate at which this patient can receive the prescribed concentration without exceeding that ceiling.
  • Mix the bag thoroughly. Inadequate mixing of KCl in flexible bags has been shown to cause up to 4× concentration spikes at the outflow port.
How this calculator works

Looks up the recommended KCl supplementation per IV fluid bag from a published sliding scale by serum K, then computes the maximum safe pump rate for this patient based on weight. InfusionFox identifies pattern; clinical decisions remain with the practitioner.

Reference range typically 3.5–5.5 mEq/L. Below 3.5 = hypokalemia. Severe (<2.5) usually warrants IV supplementation.
Smaller bags are typical for ICU patients on tighter K control.
Awaiting input

Enter a patient weight to see the result.

Reference

How the calculation works

The scale row gives KCl to add per bag and a maximum rate (mL/kg/hr) so total K delivery stays ≤ 0.5 mEq/kg/hr. Maximum pump rate for this patient:

$$\text{max pump rate (mL/hr)} = \text{weight}_{\text{kg}} \times \text{max rate}_{\text{mL/kg/hr}}$$

Final bag concentration:

$$\text{concentration (mEq/L)} = \frac{\text{KCl added (mEq)}}{\text{bag size (L)}}$$

Worked example with current inputs

Enter a patient weight to see the worked example.

Enter a patient weight to see the worked example.

Reference

Sliding scale

Guidelines for routine intravenous supplementation of potassium in dogs and cats, designed so that the K delivery rate does not exceed 0.5 mEq/kg/hr at the maximum listed pump rate.

Serum K (mEq/L) mEq KCl per 1 L bag mEq KCl per 250 mL bag Max pump rate (mL/kg/hr)
< 2.0 80 20 6
2.1–2.5 60 15 8
2.6–3.0 40 10 12
3.1–3.5 28 7 18
3.6–5.0 20 5 25

Concentration ceilings

  • Peripheral vein: ≤ 60 mEq/L (above this causes vein irritation and sclerosis; central line preferred).
  • Subcutaneous route: ≤ 35 mEq/L.
  • The K<2.0 row's 80 mEq/L concentration exceeds the peripheral ceiling, central access is recommended for that band.

Practical notes

  • KCl IV infusion should not exceed 0.5 mEq/kg/hr to avoid cardiac toxicity.
  • DKA exception: rates up to 0.9 mEq/kg/hr have been used safely in human patients with continuous ECG monitoring; InfusionFox enforces the 0.5 mEq/kg/hr ceiling regardless.
  • Begin oral potassium supplementation as soon as the patient can tolerate it.
  • For lab samples drawn from K-containing fluid lines, discard the initial volume to avoid spuriously high results.
  • Mix the bag thoroughly after addition to prevent localized concentration spikes (up to 4× reported with inadequate mixing).

Sources

  • DiBartola SP, ed. Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. 4th ed. St. Louis, MO: Elsevier Saunders; 2012. Chapter 5 (Disorders of Potassium: Hypokalemia and Hyperkalemia), pp. 107-108, Table 5-2.
  • Table 5-2 originally from: Greene RW, Scott RC. Lower urinary tract disease. In: Ettinger SJ, ed. Textbook of Veterinary Internal Medicine. Philadelphia: WB Saunders; 1975:1572.