InfusionFox
Endocrine

Insulin CRI (DKA, low-dose IV)

Continuous low-dose IV regular insulin CRI for diabetic ketoacidosis in dogs and cats. Start once intravascular volume has been restored and dehydration is being actively corrected. The sliding scale adjusts pump rate and carrier fluid composition together so BG falls steadily without driving the patient into hypoglycemia.

Regular crystalline insulin · 250 mL bag · IV
  • Regular crystalline insulin only. Do NOT use lispro, aspart, NPH, glargine, detemir, or any long- or ultra-short-acting analogue for this protocol. Hoehne specifies regular insulin (Humulin R, Novolin R, ReliOn R, etc.) for the low-dose CRI.
  • Prime the line and discard 50 mL. Regular insulin binds to plastic IV tubing, running 50 mL of the prepared solution through the administration set and discarding it saturates the binding sites so the delivered dose matches the calculated rate. This is not optional.
  • Goal: BG decline ≤ 50–75 mg/dL/hr toward < 250 mg/dL. Faster decline risks osmotic shifts. Adjust by changing the pump rate per the sliding scale, not the bag concentration. Re-check BG every 2 hours.
  • Do not give insulin SC in dehydrated DKA patients, absorption is unreliable. IV CRI or intermittent IM (see /insulin-im-dka) until rehydrated and eating.
Determines the current sliding-scale tier (pump rate + fluid composition). Re-enter when BG is rechecked every 2 hours.
Default 2.2 U/kg for both species; modern evidence supports this in cats. The conservative 1.1 U/kg cat option remains in the literature; only affects calculations when species is cat.
Awaiting input

Enter a patient weight to see the result.

Reference

How the calculation works

The bag is prepared once: 2.2 U/kg regular insulin added to 250 mL 0.9% NaCl. After priming and discarding 50 mL to saturate the tubing binding sites, the effective concentration is:

$$\text{effective concentration} = \frac{2.2_{\text{U/kg}} \times \text{weight}_{\text{kg}}}{250 - 50}\,\text{U/mL}$$

The sliding scale then specifies the pump rate (mL/hr) for each blood glucose tier, which delivers:

$$\text{delivered dose (U/kg/hr)} = \frac{\text{rate}_{\text{mL/hr}} \times \text{concentration}_{\text{U/mL}}}{\text{weight}_{\text{kg}}}$$

Worked example with current inputs

Enter a patient weight to see the worked example.

Enter a patient weight to see the worked example.

Enter a patient weight to see the worked example.

Concurrent management

Electrolytes and monitoring

Hypokalemia, hypophosphatemia, and hypomagnesemia commonly develop or worsen as DKA therapy progresses (rapid declines in K and P seen in 84% and 48% of dogs respectively per Hoehne). Monitor electrolytes every 4–6 hours initially.

  • Potassium: KCl CRI per the InfusionFox sliding-scale calculator (/hypokalemia). Hard ceiling 0.5 mEq/kg/hr.
  • Phosphate: KPhos CRI 0.03–0.12 mmol/kg/hr IV. If KPhos is given concurrently with KCl for K supplementation, subtract the K contribution of the KPhos from the total K administered as KCl.
  • Magnesium: MgSO₄ CRI 0.25–1 mEq/kg/day in patients with documented hypomagnesemia.
  • Bicarbonate: Generally not needed, the metabolic acidosis of DKA resolves with fluid + insulin therapy. Hoehne notes ADA recommends IV bicarbonate only if arterial pH < 7.0 after 1 hr of fluids; give one-third to one-half of the calculated dose, then re-check pH.

BG / interstitial glucose: every 1–2 hr until stable, then every 4 hr. Hoehne notes continuous glucose monitoring systems are an accurate alternative in DKA patients.

Concurrent disease workup is essential. Concurrent diseases drive DKA in up to 74% of dogs and 93% of cats (Hoehne, citing pancreatitis, UTI, neoplasia, hyperadrenocorticism in dogs; hepatic lipidosis, cholangiohepatitis, pancreatitis, infections, and neoplasia in cats). DKA will not resolve durably without identifying and treating the underlying trigger.

Sources

  • Hoehne SN. Diabetic Ketoacidosis. In: Silverstein DC, Hopper K, eds. Small Animal Critical Care Medicine. 3rd ed. St. Louis, MO: Elsevier; 2023. Chapter 73, pp. 432–435. Sliding scale: Table 73.1, p. 435 (CRI protocol; Macintire 1993 cited as the source of the per-tier rates). Treatment overview: Box 73.1, p. 434.
  • See also /insulin-im-dka for the intermittent IM alternative protocol.