What starting infusion rate and titration protocol should I use for a noradrenaline (norepinephrine) infusion in a 70‑kg adult with hypotension?

Norepinephrine Infusion Protocol for a 70-kg Adult with Hypotension

Start norepinephrine at 0.5 mg/hour (approximately 8 mcg/min or 0.1–0.15 mcg/kg/min) via continuous IV infusion, preferably through central venous access, while simultaneously administering at least 30 mL/kg (2100 mL for 70 kg) crystalloid bolus, and titrate every 4 hours by 0.5 mg/hour increments to achieve a mean arterial pressure of 65 mmHg. 1

Critical Pre-Administration Requirements

Before initiating norepinephrine, you must address hypovolemia with aggressive fluid resuscitation. 1, 2

• Administer a minimum 30 mL/kg crystalloid bolus (2100 mL for a 70-kg patient) before or concurrent with norepinephrine initiation to prevent severe organ hypoperfusion caused by vasoconstriction in hypovolemic patients. 1, 2
• Use balanced crystalloids (lactated Ringer's or Plasma-Lyte) preferentially over normal saline for fluid resuscitation. 1
• In severe hypotension (systolic <70 mmHg), start norepinephrine as an emergency measure while fluid resuscitation continues rather than waiting for complete volume repletion. 1

Preparation and Concentration

Standard adult concentration: Add 4 mg of norepinephrine to 250 mL of D5W to yield 16 mcg/mL. 1

• This concentration allows for precise titration and minimizes volume administration. 1
• Never mix norepinephrine with sodium bicarbonate or other alkaline solutions in the IV line, as adrenergic agents are inactivated in alkaline solutions. 3, 2

Administration Route

Central venous access is strongly preferred to minimize extravasation risk and tissue necrosis. 1, 2

• If central access is unavailable or delayed, temporary peripheral IV or intraosseous administration can be used with strict monitoring protocols. 1, 2
• Place an arterial catheter as soon as practical for continuous blood pressure monitoring. 1

Starting Dose and Initial Titration

Begin at 0.5 mg/hour (approximately 8–12 mcg/min or 0.1–0.15 mcg/kg/min for a 70-kg patient). 1, 2

• Monitor blood pressure and heart rate every 5–15 minutes during initial titration. 1, 2
• Increase dose by 0.5 mg/hour every 4 hours as needed to achieve target MAP. 1
• Maximum recommended dose is 3 mg/hour (50 mcg/min or 0.7 mcg/kg/min). 1

Hemodynamic Target

Target mean arterial pressure (MAP) of 65 mmHg for most patients. 1, 2

• Patients with chronic hypertension may require higher MAP targets (70–80 mmHg), while younger normotensive patients may tolerate lower pressures. 1
• Titrate based on both MAP and markers of tissue perfusion: lactate clearance, urine output >50 mL/hour, mental status, and capillary refill. 1, 2

Escalation Strategy for Refractory Hypotension

When norepinephrine reaches 0.25 mcg/kg/min (approximately 17.5 mcg/min or 1 mg/hour for 70 kg) and hypotension persists, add vasopressin 0.03–0.04 units/min as second-line therapy rather than continuing to escalate norepinephrine alone. 1, 2

• Alternatively, add epinephrine 0.1–0.5 mcg/kg/min if vasopressin is unavailable. 1
• For persistent hypoperfusion despite adequate vasopressors with evidence of myocardial dysfunction, add dobutamine starting at 2.5 mcg/kg/min, doubling every 15 minutes up to 20 mcg/kg/min. 1, 4
• Consider hydrocortisone 50 mg IV every 6 hours (or 200 mg continuous infusion) for refractory shock requiring high-dose vasopressors. 1

Monitoring Parameters

Continuous monitoring must include: 1, 2

• Blood pressure (preferably via arterial line) every 5–15 minutes initially, then continuously
• Heart rate and cardiac rhythm
• Urine output (target >50 mL/hour for at least 4 hours)
• Lactate clearance
• Mental status
• Capillary refill and peripheral perfusion (skin temperature, extremity warmth)
• Signs of excessive vasoconstriction (cold extremities, decreased urine output)

Management of Extravasation

If extravasation occurs, infiltrate phentolamine 5–10 mg diluted in 10–15 mL of saline intradermally at the site immediately to prevent tissue necrosis. 1, 2

• Do not remove the IV catheter before administering phentolamine, as it serves as a landmark for precise infiltration. 1
• Observe the patient for at least 24 hours after phentolamine treatment to confirm no further tissue injury is developing. 1

Special Considerations for Obese Patients

For obese patients (BMI ≥30), use actual body weight for initial dosing calculations but recognize that weight-based requirements may be lower than in non-obese patients. 5

• Obese patients require lower weight-based doses (approximately 0.09 mcg/kg/min) compared to non-obese patients (0.13 mcg/kg/min) but similar total doses (8–9 mcg/min). 5
• Consider starting at the lower end of the dosing range and titrating based on response rather than strict weight-based calculations. 5

Critical Pitfalls to Avoid

Never use dopamine as first-line therapy instead of norepinephrine, as it is associated with higher mortality and more arrhythmias. 1, 2

Do not use low-dose dopamine for "renal protection"—it provides no benefit and is strongly discouraged. 1, 2

Avoid phenylephrine as first-line therapy, as it may raise blood pressure while worsening tissue perfusion due to pure alpha-agonism without beta effects. 1

Do not expect norepinephrine to increase heart rate—the baroreceptor-mediated vagal reflex typically causes no change or modest bradycardia despite beta-1 stimulation. 2

Never increase norepinephrine doses with the goal of inducing tachycardia or enhancing cardiac output via chronotropic mechanisms—add dobutamine instead if cardiac output augmentation is needed. 2, 4