Insulin bolus in DKA?

A middle aged male with a history of IDDM presents with 2 days of nausea and vomiting. He reports running out of his insulin. In triage, FSBS is critical high, FS ketones are 5.0. You start to treat for DKA with bolus of IVF and draw basic labs. You order your insulin infusion and give a 0.10U/kg bolus prior to starting the drip. Your attending questions your actions. 

Clinical Question:

Is there any evidence to support giving an insulin bolus prior to starting a drip in DKA patients?

Literature:

The latest ADA recommendations last updated in 2009 still recommend giving a 0.1U/kg bolus prior to initiating an insulin infusion at 0.1U/kg/hr. This recommendation is based on the theory that DKA represents a significant "insulin resistant" state, and a bolus of insulin is needed to overcome this resistance and effectively reduce serum glucose and suppress gluconeogensis. Much of these recommendations are based on limited studies from the 1980's, measuring active levels of insulin in serum, and none were prospective comparing continuous insulin infusion with and without the bolus. (1) In 2008, Kitbachi Et al performed a randomized prospective study with three arms, those on an insulin infusion at 0.07U/kg/hr with and without a bolus, and those who were only on a infusion at 0.14U/kg/hr. Kitbachi effectively demonstrated that an insulin bolus is unnecessary in those who were started on a infusion at 0.14U/kg/hr. There was no difference in time to optimal glucose, pH, Anion Gap, or bicarbonate. (2) In 2010, Goyal Et al performed a similar study but had two arms, insulin infusion at 0.1U/kg/hr and those with an infusion and a bolus. He showed no difference in length of ED stay or hospital stay, and no difference in time to goal glucose or anion gap closure. (3)

Take Home:

In summary, there appears to be a paucity of evidence supporting the ADA recommendation for an insulin bolus prior to infusion, however there seems to be robust evidence showing at least a noninferiority with insulin infusion alone. Therefore I find there is no reason to continue using an insulin bolus during my standard treatment of DKA.

References:

1) Diabetes in the Emergency Department: Acute Care of Diabetes Patients. Clinical Diabetes April 1, 2011 29:51-59 http://care.diabetesjournals.org/content/32/7/1335.short
2) Kitabchi Et al, Is a priming dose of insulin necessary in a low-dose insulin protocol for the treatment of diabetic ketoacidosis? Diabetes Care. 2008 Nov;31(11):2081-5
3) Goyal Et al, Utility of initial bolus insulin in the treatment of diabetic ketoacidosis. J Emerg Med. 2010 May;38(4):422-7. doi: 10.1016/j.jemermed.2007.11.033. Epub 2008 Jun 2.

Submitted by Louis Jamtgaard, PGY-3