Vasopressor Initiation and Titration

Vasopressors raise mean arterial pressure by vasoconstriction in shock that does not respond to enough fluid, or when hypotension threatens organ perfusion during resuscitation. Noradrenaline is the first-line agent in septic, vasodilatory and most other forms of shock, and the usual target is a mean arterial pressure of 65 mm Hg.

Targets. A target of 60 to 65 mm Hg may be enough in older adults, and a higher target may be needed in chronic hypertension. Judge perfusion by lactate, capillary refill, urine output and mentation as well as pressure.

Access. Give through a central vein when possible. A large proximal peripheral vein can be used for noradrenaline for a short time (under 24 hours) while central access is placed, with frequent site checks.

Dose units. Errors arise from mixing micrograms/min and micrograms/kg/min. State the concentration and unit on the chart.

First line. Noradrenaline.

Second line.

• Vasopressin added when noradrenaline reaches about 0.25 to 0.5 micrograms/kg/min, to spare catecholamine.

• Adrenaline when cardiac output is low or noradrenaline and vasopressin are not enough.

• Hydrocortisone added for persistent shock needing escalating vasopressor doses.

Other situations.

• Anaphylaxis: adrenaline.

• Cardiogenic shock: noradrenaline, with an inotrope.

• Neurogenic shock: noradrenaline or phenylephrine.

• Dopamine: only in selected patients with bradycardia and low risk of tachyarrhythmia.

Special groups.

• Children: dose by weight, and use adrenaline or noradrenaline by weight-based infusion.

• Pregnancy: phenylephrine and noradrenaline are used for shock, with left lateral tilt.

• Older adults: lower starting rates and slower titration.

• East Africa: where central access or infusion pumps are unavailable, use a peripheral vein with close site monitoring, a dedicated line and a calculated drip rate checked by two clinicians.

• Noradrenaline: start 0.05 micrograms/kg/min (about 3 to 5 micrograms/min), increase every 5 to 10 minutes by 0.05 micrograms/kg/min to the pressure target. Doses over 0.5 micrograms/kg/min indicate refractory shock.

• Vasopressin: 0.03 units/min fixed (range 0.01 to 0.04 units/min), not titrated upward.

• Adrenaline: 0.05 to 0.5 micrograms/kg/min.

• Phenylephrine: 100 to 180 micrograms/min to start, then 40 to 60 micrograms/min for maintenance.

• Dopamine: 5 to 20 micrograms/kg/min.

• Hydrocortisone: 200 mg daily, as 50 mg intravenously every 6 hours or an infusion.

Monitoring. Use an arterial line, continuous ECG, lactate every 2 to 4 hours, hourly urine output, and checks for digital, gut and limb ischaemia. Check the infusion site every hour for peripheral delivery.

Extravasation. Stop the infusion, aspirate the cannula and infiltrate phentolamine 5 to 10 mg in 10 mL of saline around the site.

Stop rules. Wean one agent at a time in small steps once the pressure is stable and lactate is falling. Stop immediately for severe arrhythmia, limb or gut ischaemia, or extravasation.

Referral and escalation. Escalate for noradrenaline over 0.5 micrograms/kg/min, a lactate that does not fall, a need for a third agent, or a cardiac cause needing mechanical support.

Common errors. Starting vasopressors in an uncorrected hypovolaemic patient, mixing dose units, using a weak peripheral line without monitoring, and stopping vasopressin abruptly, which can cause rebound hypotension.