Pressors

Noradrenaline

0.01-3 mcg/kg/min IV infusion (central line preferred)

• First line vasopressor in distributive and most forms of shock

• Predominantly ${\alpha }_1$ agonist with some ${\beta }_1$ ⇒ ↑ SVR and mild ↑ HR/CO

• Can be run peripherally short-term (forearm or antecubital) at low doses while CVC inserted

Metaraminol

Bolus: 0.5-2 mg IV PRN | Infusion: 15-30 mg in 500 mL at 15-60 mL/hr

• Predominantly ${\alpha }_1$ agonist; also causes indirect noradrenaline release

• Used widely in peri-operative setting and as bridge vasopressor pre-noradrenaline

• Can be given peripherally; suitable in ward or theatre setting

• Tachyphylaxis with prolonged use

• Reflex bradycardia can occur - treat with atropine

• Less titratable than noradrenaline infusion

Adrenaline

Anaphylaxis: 0.3-0.5 mg IM (thigh) | Shock infusion: 0.01-1 mcg/kg/min IV

• Anaphylaxis: IM adrenaline (Epipen 0.3 mg or ampoule 1:1000) is the drug of first choice

• Septic shock: Second agent alongside noradrenaline when additional inotropic support needed; associated with increased lactate that does not reflect true worsening

• Cardiogenic shock: Adrenaline has more arrhythmogenic risk than other inotropes

• Cardiac arrest: 1 mg IV every alternate loop

Terlipressin

Bolus: 0.85–2.5 mg IV bolus q4–6h | Infusion: 1.3–5 mg/24h

• $V_1$ receptor agonist (smooth muscle vasoconstriction)
• Hepatorenal syndrome type 1: terlipressin + albumin is first line
• Variceal bleeding: 2mg IV bolus then 1 mg q4-6h for up to 5 days
• Used in refractory septic shock as noradrenaline-sparing agent (off-label in Australia)
• Risk: digital/skin ischaemia, bradycardia, mesenteric ischaemia — monitor carefully
• Avoid in ischaemic heart disease, peripheral vascular disease

Doboutamine

2–20 mcg/kg/min IV infusion

• ${\beta }_1$ and ${\beta }_2$ agonist - positive inotropy, chronotropy; reduces SVR (vasodilatory)
• Used in cardiogenic shock with adequate MAP (often combined with noradrenaline)
• Risk of tachycardia and arrhythmia; may worsen hypotension in true hypovolaemia

Milrinone

0.125–0.75 mcg/kg/min IV (load: 25–50 mcg/kg over 10 min, often omitted)

• Used in cardiogenic shock, especially post-cardiac surgery or when β-receptor downregulation limits dobutamine effect
• Useful in pulmonary hypertension (reduces PVR)
• Longer half-life — effects accumulate, harder to titrate; prolonged hypotension if overdosed
• Renally cleared — dose-reduce in AKI

Phenylephrine

Bolus 50–200 mcg IV | Infusion 10–300 mcg/min

• Pure α₁ agonist — vasoconstriction without inotropic effect

• Useful in tachycardia-associated shock where noradrenaline’s β₁ effect is undesirable (e.g., HOCM, AF with fast ventricular rate)

• Reflex bradycardia — use cautiously in bradycardic patients

• Can worsen cardiogenic shock by increasing afterload without supporting cardiac output