Norepinephrine Dosing in Shock: 25 ng/kg/min is a Low Dose
A dose of 25 nanograms per kilogram per minute (ng/kg/min) of Levophed (norepinephrine) is considered a low dose in the management of shock.
Dosing Range Context
According to established guidelines, norepinephrine dosing for shock management falls within the following ranges:
- Low dose: 0.01-0.1 μg/kg/min (10-100 ng/kg/min)
- Moderate dose: 0.1-0.5 μg/kg/min (100-500 ng/kg/min)
- High dose: >0.5 μg/kg/min (>500 ng/kg/min)
The American Heart Association and pediatric emergency guidelines indicate that the typical therapeutic range for norepinephrine in shock is 0.1-2.0 μg/kg/min (100-2000 ng/kg/min) 1. At 25 ng/kg/min, this dose falls at the lower end of the therapeutic spectrum.
Clinical Implications of Low-Dose Norepinephrine
Low-dose norepinephrine (25 ng/kg/min) has the following characteristics:
- Provides mild to moderate vasoconstriction
- Has minimal impact on heart rate compared to higher doses
- Carries lower risk of peripheral ischemia and tissue necrosis
- Less likely to cause tachyarrhythmias compared to higher doses 2
Dosing Considerations
The FDA label for Levophed indicates that dosing should be titrated according to the patient's response, with the average maintenance dose ranging from 2-4 μg/min of base (not weight-based) 3. When converting to weight-based dosing, this typically corresponds to 0.02-0.06 μg/kg/min for most adults, placing 25 ng/kg/min (0.025 μg/kg/min) within this lower maintenance range.
Important Clinical Considerations:
Mortality correlation: Doses exceeding 1 μg/kg/min (1000 ng/kg/min) have been associated with mortality rates >90% in septic shock 4, making 25 ng/kg/min substantially below this threshold.
Obese vs. non-obese patients: Research shows that obese patients typically require lower weight-based doses (0.09 μg/kg/min) compared to non-obese patients (0.13 μg/kg/min) 5. For both groups, 25 ng/kg/min would be considered low.
Titration approach: Guidelines recommend starting at the lowest effective dose and titrating up based on clinical response, targeting a mean arterial pressure of 65 mmHg 1, 6.
Clinical Cautions
Even at low doses like 25 ng/kg/min, monitor for:
- Extravasation (can cause severe tissue damage)
- Arrhythmias (though less common at lower doses)
- Ensure adequate volume status before initiating norepinephrine
Conclusion
At 25 ng/kg/min, norepinephrine is being administered at a low dose that would typically be used in the initial management of shock, with expectation of upward titration based on clinical response. This dose is well below the thresholds associated with high mortality or significant adverse effects.