The Catecholamine Sparer
Second-line vasopressor added to Norepinephrine in septic shock for catecholamine sparing. Effective in severe acidemia where catecholamines fail. Fixed dosing in Canada.
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Mechanism: Receptor Agonist: Causes vascular smooth muscle contraction via non-adrenergic pathways. Also acts on (kidney) causing water retention (antidiuretic).
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Dosing: Canada (Fixed): 0.03 or 0.04 units/min. Do not titrate up and down rapidly due to longer half-life.
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PK: Onset: 5–15 mins. Half-life: 10–20 mins (Longer than catecholamines).
indications
- Septic Shock (Catecholamine Sparing) – Second-line, usually added when Norepi > 0.25–0.5 mcg/kg/min
- Vasoplegia Post-Cardiac Surgery – Specific niche
evidence & efficacy
- VASST Trial: No mortality benefit overall, but potential benefit in “less severe” shock (<15 mcg/min norepi).
- Sparing Effect: Useful to limit the arrhythmogenic dose of norepinephrine.
cautions
contraindications
- Ischaemia: Can cause coronary, mesenteric (gut), and digital ischaemia at high doses
- Hyponatremia: rare with stress dosing, but possible ( effect). Generally avoid in patients with or at high risk of raised ICP.
special considerations (canada/royal college)
clinical pearl
Acidosis: Remains effective in severe acidemia (pH < 7.15) where catecholamine receptors become desensitized.
- Fixed Dosing: In Canada, typically run at 0.03 or 0.04 units/min fixed. Do not titrate up and down rapidly due to longer half-life.