Category:Vasopressors: Difference between revisions

A vasopressor is a medicine that raises the blood pressure by producing arterial vasoconstriction. The category sits at the intersection of sympathomimetics, hormones, and the small set of pressor agents acting on other mechanisms. The clinical use of vasopressors is concentrated in the acute-care setting: distributive shock (septic, anaphylactic, neurogenic), cardiogenic shock when filling pressures are adequate, anaesthesia-induced hypotension, and the emergency management of cardiac arrest where the inotropic and vasoconstrictor effects are co-equally desired.

The history of the category coincides with the isolation of adrenaline by Jokichi Takamine in 1900, the first hormone isolated in pure form and the first systematically used vasopressor. The clinical pharmacology has been progressively refined as the receptor classification (alpha vs beta of Ahlquist 1948, then the alpha-1/alpha-2 and beta-1/beta-2/beta-3 subtypes through the 1960s and 1980s) has clarified which receptor activation produces which physiological effect. The modern vasopressor pharmacopoeia is built on the principle that septic shock is dominated by vasodilatation rather than by depressed inotropy, and that an alpha-1-predominant agent is therefore the first-line approach.

The SOAP-II trial in 2010 compared norepinephrine and dopamine as initial vasopressors in shock and found that norepinephrine was associated with substantially fewer arrhythmic events and a trend toward lower mortality;^[1] norepinephrine has since been the first-line vasopressor in essentially every contemporary septic-shock guideline. The VASST trial in 2008 demonstrated that the addition of low-dose vasopressin (0.03 units per minute, replacing the relative vasopressin deficiency of septic shock) to norepinephrine produced a non-inferior outcome with reduced norepinephrine requirement, and vasopressin has become the standard second-line agent in catecholamine-refractory shock.

The most recent vasopressor approval is the recombinant human angiotensin II (Giapreza, La Jolla Pharmaceutical, 2017), studied in the ATHOS-3 trial of catecholamine-resistant vasodilatory shock and used as a third-line agent in selected patients with profound vasoplegia.^[2] The clinical use of angiotensin II in shock remains, as of the mid-2020s, niche but mechanistically distinct from the catecholamines, and a small body of evidence suggests it may be particularly useful in shock complicating cardiac surgery and in acute-on-chronic kidney injury with vasoplegia.

The other vasopressor agents fill more specific niches. Intravenous phenylephrine, an alpha-1 selective agonist, is used by anaesthetists for the transient hypotension of spinal or epidural anaesthesia; the lack of beta-1 inotropic effect makes it useful where reflex tachycardia is to be avoided (aortic stenosis, tetralogy of Fallot, hypertrophic cardiomyopathy). Oral midodrine (an alpha-1 agonist metabolically activated to desglymidodrine) is used for chronic orthostatic hypotension in autonomic failure. Methylene blue, originally an antimalarial and a methemoglobinemia antidote, is used off-label in selected catecholamine-refractory vasoplegic shock through inhibition of soluble guanylate cyclase and nitric oxide synthase. The intravenous calcium-channel antagonist reversal protocols use calcium gluconate, glucagon, insulin-glucose, and intravenous lipid emulsion in addition to the standard catecholamine vasopressors.

The clinical management of a vasopressor infusion is, like that of many intensive-care medicines, as much about technique as about dose. Central-venous access is required for sustained infusion to avoid extravasation injury; arterial-line monitoring is required for titration; the choice of agent and the rate of escalation are guided by the clinical context (sepsis: norepinephrine first, vasopressin second, angiotensin II or epinephrine third; cardiogenic shock with inadequate cardiac output: dobutamine first, epinephrine or milrinone second; anaphylaxis: intramuscular epinephrine first, intravenous epinephrine and pressors as needed; neurogenic shock with bradycardia: norepinephrine with chronotropic support).

By mechanism:

• Catecholamines (endogenous and synthetic) (cross-indexed under sympathomimetics and catecholamines where built):
  • Norepinephrine (first-line in septic and distributive shock)
  • Epinephrine (anaphylaxis, cardiac arrest, refractory shock, severe asthma exacerbation)
  • Dopamine (less commonly used since SOAP-II)
  • Dobutamine (beta-1 selective inotrope, not strictly a vasopressor)
  • Phenylephrine (alpha-1 selective)
• Vasopressin and its analogues (cross-indexed under hormones):
  • Vasopressin (arginine vasopressin, antidiuretic hormone) for catecholamine-refractory shock
  • Terlipressin (selective V1 receptor agonist; hepatorenal syndrome, oesophageal variceal bleeding, refractory shock in selected jurisdictions)
• Renin-angiotensin pathway:
  • Recombinant human angiotensin II (Giapreza, 2017)
• Other:
  • Methylene blue (intravenous, off-label, refractory vasoplegic shock)
  • Hydroxocobalamin (cyanokit, occasionally used for cyanide-induced vasoplegia)
  • Midodrine (oral, chronic orthostatic hypotension; not for acute shock)
  • Droxidopa (oral, metabolised to norepinephrine; neurogenic orthostatic hypotension)

The boundary of this category is "medicine prescribed to raise arterial blood pressure through vasoconstriction in the acute or chronic setting." The antihypertensives are the pharmacologic opposite of vasopressors and are collected separately. The intravenous fluid resuscitation of hypotensive shock with crystalloid or colloid is a volume intervention rather than a vasopressor and is listed under electrolyte replacements. The chronic medicines used in autonomic failure for orthostatic hypotension (midodrine, droxidopa, fludrocortisone for volume expansion, pyridostigmine in selected cases) are collected here when their use is specifically for blood-pressure support. The combined alpha-and-beta blocker labetalol, although it lowers rather than raises blood pressure, is sometimes mentioned in hypertensive-emergency context alongside vasopressor pharmacology because of the clinical-pharmacology overlap; labetalol is listed under beta-blockers and antihypertensives.

This category page is an encyclopedia article about its subject. The actual index of medicines belonging to the category is generated automatically by the wiki engine, from category-membership declarations on the individual medicine pages, and appears at the foot of the page below the references.