Vasopressin is Synthesized to Lesser Extent in the Heart in Response to Wall Stress
Vasopressin is Synthesized to Lesser Extent in the Adrenal Gland in Response to Increased Catecholamine Secretion
Physiologic Actions of Vasopressin
Vasopressin Acts at V2 Receptors on the Renal Collecting Duct, Resulting in Increased Collecting Duct Permeability: result in water reabsorption
Vasopressin is the Primary Anti-Diuretic Hormone (ADH): regulates water balance
Vasopressin Acts at V1a Receptors on Vascular Smooth Muscle, Resulting in Potent Vasoconstriction
General Comments
However, the vasoconstrictor effect of vasopressin occurs at doses higher than the anti-diuretic activity
The vasoconstrictor effects of vasopressin are relatively preserved during hypoxic and acidotic conditions (both of which develop during shock)
Cerebral Vasoconstriction: less direct effect than the catecholamines
Coronary Vasoconstriction: less direct effect than the catecholamines
Increased Vascular Sensitivity to Norepinephrine (see Norepinephrine, [[Norepinephrine]])
Neutral or Inhibitory Effect on Cardiac Output: depending on its dose-dependent increase in systemic vascular Resistance (SVR) and the reflexive increase in vagal tone
Vasopressin Acts at V1b Receptors in the Pituitary Gland
Administration
Cardiac Arrest (ACLS Guidelines): 40 U IV Bolus
High-Dose IV Drip (for Esophageal Variceal Hemorrhage): 0.3 to 1.5 U/min
At this high dose, vasopressin decreases blood flow to the splanchnic and portal venous vascular beds
High doses can result in cardiac and gastrointestinal ischemia and/or infarction: concomitatnt use of IV nitroglycerin has been used to reduce the risk of cardiac ischemia
High-Dose Intra-Arterial Drip in Superior Mesenteric Artery (for Esophageal Variceal Hemorrhage): 0.2 to 0.5 U/min
Low-Dose IV Drip (for Sepsis): non-titrating 0.04 U/min
At this low dose, vasopressin causes systemic vasoconstriction, with increased BP (and decreased CO): however, splanchnic blood flow is usually increased or unchanged
Low doses can also increase pulmonary pressures (usually modestly)
QT Prolongation with Definite Association with Torsade (see Torsade, [[Torsade]])
Renal Adverse Effects
Hyponatremia (see Hyponatremia, [[Hyponatremia]]): case reports have been described of vasopressin-induced hyponatremia when administered in the setting of septic shock [MEDLINE]
Other Adverse Effects
Digital Ischemia: due to peripheral vasoconstriction
Splanchnic Vasoconstriction
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References
Inotropes and Vasopressors: Review of Physiology and Clinical Use in Cardiovascular Disease. Circulation. 2008 Sep 2;118(10):1047-56. doi: 10.1161/CIRCULATIONAHA.107.728840 [MEDLINE]
Exogenous Vasopressin-Induced Hyponatremia in Patients With Vasodilatory Shock: Two Case Reports and Literature Review. J Intensive Care Med. 2015 Jul;30(5):253-8. doi: 10.1177/0885066613507410. Epub 2013 Oct 7 [MEDLINE]