What are the first-line treatments for severe hypotension, specifically which vasopressors (pressers) can be used to increase blood pressure?

Vasopressors for Severe Hypotension

Norepinephrine is the first-line vasopressor for severe hypotension and should be initiated at 0.1-0.5 mcg/kg/min (or 0.2-1.0 mcg/kg/min) targeting a mean arterial pressure (MAP) of 65 mmHg. 1, 2

Initial Vasopressor Selection

Norepinephrine is strongly recommended as the first-choice vasopressor across all shock states due to its superior safety profile compared to other catecholamines, with lower rates of arrhythmias and mortality. 1, 2, 3

Dosing and Administration

• Start norepinephrine at 0.1-0.5 mcg/kg/min and titrate to achieve MAP ≥65 mmHg 2
• Administer through a central venous line when possible to prevent tissue necrosis from extravasation 2
• If extravasation occurs, infiltrate 5-10 mg phentolamine diluted in 10-15 mL saline into the affected site immediately 2

Target Blood Pressure

• Initial MAP target should be 65 mmHg for most patients 1, 2
• Monitor tissue perfusion markers (lactate clearance, urine output, mental status) in addition to arterial pressure 2

Second-Line Vasopressor Options

When norepinephrine alone fails to achieve adequate MAP or requires escalating doses, add a second agent rather than continuing to increase norepinephrine:

Vasopressin (Preferred Second-Line Agent)

• Add vasopressin 0.03 units/min to norepinephrine when additional vasopressor support is needed 1, 4
• Vasopressin is FDA-approved for vasodilatory shock and works independently of catecholamine receptors, making it effective when alpha-adrenergic receptors are down-regulated 1, 4
• Can be used to either raise MAP to target or decrease norepinephrine dosage 1, 2
• Do not use vasopressin as a single initial vasopressor; it must be combined with norepinephrine 1
• Doses higher than 0.03-0.04 units/min should be reserved for salvage therapy 1

Epinephrine (Alternative Second-Line Agent)

• Add epinephrine 0.05-0.5 mcg/kg/min when additional agent is needed to maintain adequate blood pressure 1, 2
• Can be added to or potentially substituted for norepinephrine 1
• Caution: Higher risk of metabolic disturbances (hyperglycemia, lactic acidosis) and tachyarrhythmias compared to norepinephrine 5

Context-Specific Considerations

Septic Shock

• Norepinephrine remains first-line 1, 3
• In patients with low systemic vascular resistance (wide pulse pressure with diastolic BP <50% of systolic), norepinephrine is recommended alone initially 1
• Vasopressin is particularly effective in septic shock due to relative vasopressin deficiency 1, 6

Pediatric Septic Shock

• Dopamine remains first-line for fluid-refractory hypotensive shock in pediatric patients, though norepinephrine is increasingly used 1
• Age-specific considerations: infants <6 months may have reduced response to dopamine due to immature sympathetic innervation 1

Cardiogenic Shock

• Norepinephrine is appropriate as first-line vasopressor 1, 7
• Add dobutamine 2-20 mcg/kg/min if evidence of persistent hypoperfusion despite adequate filling pressures to increase cardiac output 1
• Avoid excessive vasoconstriction that increases left ventricular afterload 1

Agents to Avoid or Use Sparingly

Dopamine

• Use only in highly selected patients with low risk of tachyarrhythmias and absolute or relative bradycardia 1, 2
• Associated with higher rates of cardiac arrhythmias without mortality benefit compared to norepinephrine 1, 5
• Do not use low-dose dopamine for renal protection - this practice is not supported by evidence 1, 2

Phenylephrine

• Not recommended except in rare circumstances: serious arrhythmias with norepinephrine, known high cardiac output with persistent low BP, or salvage therapy 1
• Pure alpha-agonist increases afterload without inotropic support 1

Critical Pitfalls to Avoid

• Never delay vasopressor initiation while pursuing aggressive fluid resuscitation - early norepinephrine administration may reduce fluid overload risk 2, 3
• Do not use vasopressin as monotherapy - it must be combined with catecholamine vasopressors 1
• Avoid high-dose dopamine (>10 mcg/kg/min) due to excessive adverse effects without benefit 1, 5
• Monitor for digital and mesenteric ischemia when using any vasopressor, particularly at high doses 1, 4
• Titrate vasopressors to both MAP and perfusion markers, not MAP alone 2