Beware Hypoglycemia When Treating Hyperkalemia with Insulin

Today’s pearls are about preventing hypoglycemia when using insulin to treat hyperkalemia.

The “right” insulin dose is unknown.

• Regular insulin doses of 5 unit boluses up to 20 unit/hr infusions have been used (Blumberg 1988). Most common dose is 10 units IV regular insulin bolus (lowers K+ ~ 0.5-1 mEq/L).

• Overall incidence of hypoglycemia appears to be ~10%, but could be higher (Allon 1990; Schafers 2012; Apel 2014; Scott 2019)
  • A 10 unit dose of IV regular insulin has an onset of action ~5-10 minutes, peaks at 25-30 minutes, and lasts 2-3 hours. IV dextrose lasts < 1 hour.
    • The biggest risk of hypoglycemia is about 45-90 minutes after the insulin dose when the dextrose has started to ‘wear off’

• Risk factors for developing hypoglycemia (Apel 2014)
  • No prior diagnosis of diabetes
  • No use of diabetes medication prior to admission
  • Lower pretreatment glucose (104 mg/dL vs 162 mg/dL, P = 0.04)
  • Renal dysfunction (insulin may be partially renally metabolized) (Dickerson 2011)
  • Higher insulin dose (LaRue 2017)

• Strategies for avoiding hypoglycemia
  • Here is a suggested strategy for administering enough dextrose to counter the initial insulin bolus of 10 or 20 units. It is loosely based on the Rush University protocol. (Apel 2014)
  • MGH has a hyperkalemia order set that we updated to address this issue. It provides 25 gm of dextrose up front with the insulin and has subsequent finger sticks + PRN dextrose defaulted. Please use the order set!

• The Institute for Safe Medication Practices (ISMP) highlighted this issue in a February 2018 Safety Alert

^#3

Author: Bryan D. Hayes, PharmD

Attending Pharmacist, Emergency Medicine and Toxicology, Massachusetts General Hospital; Assistant Professor of EM, Harvard Medical School View all posts by Bryan D. Hayes, PharmD