What are the classification, indications, route, dosage, contraindications, adverse reactions, interactions, and assessments for vasopressin medications?

Vasopressin Medications: Classification, Indications, and Clinical Management

Vasopressin is a potent endogenous hormone primarily used as a second-line vasopressor in vasodilatory shock (particularly septic shock) when patients remain hypotensive despite fluids and first-line catecholamines. 1, 2

Classification

• Vasopressin is classified as a non-catecholamine vasopressor hormone that acts on V1 receptors to cause vasoconstriction and V2 receptors to promote water reabsorption 3, 4
• Synthetic analogues include terlipressin (longer-acting vasopressin analogue) and desmopressin (primarily used for diabetes insipidus and hemostatic disorders) 5

Indications

• Primary indication: To increase blood pressure in adults with vasodilatory shock (post-cardiotomy or septic shock) who remain hypotensive despite fluids and catecholamines 1, 2
• Secondary indications:
  • Management of acute variceal hemorrhage in cirrhosis 6
  • Adjunctive therapy in cardiac arrest 3
  • Treatment of diabetes insipidus 5

Route and Dosage

• Administration route: Intravenous only 2
• Preparation: Dilute with normal saline (0.9% sodium chloride) or 5% dextrose in water (D5W) to either 0.1 units/mL or 1 unit/mL 2
• Dosing by indication:
  • Septic shock: 0.01 to 0.07 units/minute 1, 2
  • Post-cardiotomy shock: 0.03 to 0.1 units/minute 2
  • Variceal hemorrhage: Typically 0.2-0.4 units/minute, can be increased to maximum 0.8 units/minute (should be accompanied by IV nitroglycerin) 6
• Vasopressin should not be used as the single initial vasopressor for septic shock 1
• Doses higher than 0.03-0.04 units/minute should be reserved for salvage therapy when other vasopressors have failed 6, 1

Contraindications and Precautions

• Contraindicated in patients with known allergy or hypersensitivity to 8-L-arginine vasopressin or chlorobutanol 2
• Use with caution in patients with:
  • Cardiac dysfunction (can worsen cardiac function) 2
  • Coronary artery disease (risk of myocardial ischemia) 7
  • Mesenteric or peripheral vascular disease (risk of tissue ischemia) 7
• Terlipressin is contraindicated in patients experiencing hypoxia, worsening respiratory symptoms, or ongoing coronary, peripheral, or mesenteric ischemia 6

Adverse Reactions and Side Effects

• Cardiovascular: Decreased cardiac output, bradycardia, tachyarrhythmias 2, 7
• Vascular: Ischemia (coronary, mesenteric, skin, digital) 2, 7
• Metabolic: Hyponatremia 2
• Terlipressin-specific: Abdominal pain, chest pain, diarrhea, hyponatremia 6
• Octreotide-specific: Hypoglycemia, hyperglycemia, bradycardia, pancreatitis 6

Drug Interactions

• Additive pressor effects when used with catecholamines 2
• Indomethacin may prolong the effects of vasopressin 2
• Co-administration of ganglionic blockers or drugs causing SIADH may increase the pressor response 2
• Co-administration of drugs causing diabetes insipidus may decrease the pressor response 2

Assessments Before and After Administration

• Before administration:
  • Ensure adequate fluid resuscitation has been attempted 6, 1
  • Establish central venous access for administration 1
  • Arterial catheter placement is recommended for continuous blood pressure monitoring 6, 1
  • Assess baseline cardiac function and hemodynamic parameters 7
• During administration:
  • Continuous monitoring of blood pressure, heart rate, and ECG 1, 8
  • Monitor for signs of tissue ischemia (skin color changes, decreased urine output) 7
  • Assess for hyponatremia 2
  • Monitor cardiac output if available 7

Evaluation and Desired Outcomes

• Primary outcome: Achievement of target mean arterial pressure (typically 65 mmHg in septic shock) 6, 1
• Secondary outcomes:
  • Decreased requirements for catecholamine vasopressors 7
  • Improved organ perfusion (increased urine output, improved mental status) 7
  • Control of variceal bleeding (when used for this indication) 6

Hemodynamic and Multi-system Effects

• Cardiovascular system:
  • Vasoconstriction via V1 receptors on vascular smooth muscle 4
  • Potential decrease in cardiac output due to increased afterload 7
  • Coronary vasoconstriction may lead to myocardial ischemia in susceptible patients 7
• Renal system:
  • Increased urine output reported in several studies of septic shock 7
  • Water reabsorption via V2 receptors in the collecting ducts 4
• Splanchnic circulation:
  • Reduces portal venous blood flow and pressure (basis for use in variceal bleeding) 9
  • Risk of mesenteric ischemia with higher doses 7
• Central nervous system:
  • Acts as a neurotransmitter affecting circadian rhythm and thermoregulation 3

Comparative Efficacy

• Octreotide is the vasoactive drug of choice for variceal hemorrhage based on its superior safety profile compared to vasopressin 6
• Vasopressin is no longer advised for variceal hemorrhage due to high risk of cardiovascular adverse events 6
• For septic shock, norepinephrine remains the first-line vasopressor, with vasopressin as an adjunctive agent 6, 1