What is the norepinephrine (vasopressor) initial and maximum dose?

Norepinephrine Initial and Maximum Dosing

For septic shock and hypotension management, start norepinephrine at 0.02 mcg/kg/min (approximately 0.5 mg/hour or 8-12 mcg/min in a 70 kg adult), titrating by 0.5 mg/hour increments every 4 hours to a maximum of 3 mg/hour, targeting a mean arterial pressure of 65 mmHg. 1, 2, 3

Initial Dosing Parameters

• Start at 0.02 mcg/kg/min as recommended for septic shock, particularly in pregnant patients 1
• Alternative starting range: 0.1-0.5 mcg/kg/min (7-35 mcg/min in 70 kg adult) for general hypotension 2
• Hourly dosing equivalent: 0.5 mg/hour as the initial rate 2, 3
• Administer as continuous IV infusion, preferably through central venous access 1, 2

Maximum Dosing

• Maximum dose: 3 mg/hour (approximately 50 mcg/min or 0.7 mcg/kg/min in 70 kg adult) 2, 3
• Titration increments: 0.5 mg/hour every 4 hours based on blood pressure response 2, 3
• When reaching 0.1-0.25 mcg/kg/min without adequate response, add vasopressin 0.03-0.04 units/min as second-line therapy rather than continuing to escalate norepinephrine alone 1, 2

Critical Pre-Administration Requirements

• Administer minimum 30 mL/kg crystalloid bolus before or concurrent with norepinephrine initiation 1, 2
• Balanced crystalloids (lactated Ringer's, Plasma-Lyte) are preferred over normal saline 1
• In severe hypotension (systolic <70 mmHg), start norepinephrine emergently while continuing fluid resuscitation rather than delaying for complete volume repletion 2

Target Blood Pressure and Monitoring

• Target MAP: 65 mmHg for most patients with septic shock 1, 2, 3
• Monitor blood pressure every 5-15 minutes during initial titration 2
• Place arterial catheter as soon as practical for continuous monitoring 2
• Assess tissue perfusion markers: lactate clearance, urine output >50 mL/hour, mental status, capillary refill 2, 3

Administration Route

• Central venous access strongly preferred to minimize extravasation risk and tissue necrosis 1, 2, 3
• Peripheral IV administration acceptable temporarily if central access unavailable, with strict monitoring 2
• If extravasation occurs, infiltrate phentolamine 5-10 mg diluted in 10-15 mL saline at the site immediately 2

Escalation Strategy for Refractory Hypotension

• Add vasopressin 0.03-0.04 units/min when norepinephrine reaches 0.1-0.25 mcg/kg/min and hypotension persists 1, 2
• Add epinephrine 0.1-0.5 mcg/kg/min as alternative second agent if needed 2
• Add dobutamine up to 20 mcg/kg/min for persistent hypoperfusion with myocardial dysfunction 2
• Do NOT increase vasopressin above 0.04 units/min except for salvage therapy 2

Special Population Considerations

Pregnant Patients

• Start at 0.02 mcg/kg/min with target MAP 65 mmHg 1
• Consider more restrictive initial fluid boluses (1-2 L) due to lower colloid oncotic pressure and higher pulmonary edema risk 2
• Vasopressin 0.04 units/min can be added for refractory shock with fetal monitoring when appropriate 1

Pediatric Patients

• Starting dose: 0.1 mcg/kg/min, titrating to clinical effect 2, 3
• Typical range: 0.1-1.0 mcg/kg/min 2, 3
• Maximum doses up to 5 mcg/kg/min may be necessary in some children 2

Critical Pitfalls to Avoid

• Never use dopamine as first-line agent - associated with higher mortality and arrhythmias compared to norepinephrine 2
• Do not use phenylephrine as first-line therapy - may raise blood pressure while worsening tissue perfusion 2
• Avoid low-dose dopamine for renal protection - no benefit and strongly discouraged 2
• Do not mix with sodium bicarbonate or alkaline solutions - inactivates adrenergic agents 2
• Address hypovolemia first - vasoconstriction in hypovolemic patients causes severe organ hypoperfusion despite "normal" blood pressure 2

Nuances in Dosing Context

The evidence shows a potency ratio of approximately 12-13:1 for norepinephrine versus phenylephrine when administered as infusions 4, 5. Recent research supports early norepinephrine administration (concurrent with fluid resuscitation) in patients with profound hypotension, particularly when diastolic blood pressure ≤40 mmHg or diastolic shock index ≥3, to avoid prolonged hypotension 6. The fixed hourly dosing regimen (0.5-3 mg/hour) provides a practical framework that aligns with the mcg/kg/min dosing when accounting for average adult body weight 2, 3.