Insulin Should NOT Be Used as a Pressor for Hypotension
Insulin has no role as a vasopressor or blood pressure support agent in patients without hyperglycemia. This question reflects a fundamental misunderstanding of insulin's cardiovascular effects.
Insulin's Actual Hemodynamic Effects
Vasodilatory Properties
- Insulin causes vasodilation and reduces total peripheral vascular resistance in experimental studies, not vasoconstriction 1, 2
- Insulin per se does not elevate blood pressure; rather, it possesses vasodilatory properties that would theoretically lower blood pressure 1, 2
Hypotensive Effects in Specific Populations
- In diabetic patients with autonomic neuropathy, insulin administration provokes severe postural hypotension, with systolic blood pressures falling below 50 mm Hg in some cases 3
- This hypotensive effect occurs almost immediately after intravenous insulin, is progressive, and may last several hours 3
- The hypotensive effect coincides with falling blood glucose levels and occurs before hypoglycemic levels are reached 3
Why This Misconception Exists
Insulin Resistance and Hypertension Association
- Hyperinsulinemia and insulin resistance are associated with elevated blood pressure in epidemiological studies, but this does not mean insulin raises blood pressure directly 1, 4, 2
- The relationship is confounded by obesity, age, and ethnic differences 1
- Proposed indirect mechanisms include enhanced renal sodium retention, elevated intracellular calcium, and increased sympathetic nervous system activity—but these are secondary effects of chronic insulin resistance, not acute insulin administration 2
Contradictory Evidence
- Neither insulin infusion within physiological range nor continuously sustained hyperinsulinemia in patients with insulinoma are associated with elevated blood pressure 1
- Some experimental studies show no blood pressure elevation could be induced by prolonged hyperinsulinemia 2
Appropriate Vasopressor Options
For hypotension without hyperglycemia, standard vasopressors should be used:
- Norepinephrine for distributive shock
- Vasopressin as adjunctive therapy
- Epinephrine for anaphylactic or cardiogenic shock
- Phenylephrine for isolated vasodilation
The Only Context Where Insulin Affects Blood Pressure Management
- In hemorrhagic hypotension and resuscitation, insulin administration prevents the increase in glucose-6-phosphatase gene expression responsible for hyperglycemia, but this is a metabolic effect, not a pressor effect 5
- Insulin normalized plasma glucose and corticosterone levels during hemorrhagic hypotension, but was not used to raise blood pressure 5
Critical Safety Concern
Administering insulin to a normoglycemic or hypoglycemic patient with hypotension would be dangerous, potentially causing:
- Severe hypoglycemia
- Worsening hypotension (especially in patients with autonomic dysfunction) 3
- Cardiovascular collapse
- Neurological injury from hypoglycemia