Noradrenaline Dosing for Septic Shock in a 35 kg Patient
For a 35 kg man with septic shock, the initial noradrenaline microdrip rate should be 52-105 drops per minute using a 500 ml D5W solution with a starting dose of 0.05-0.1 μg/kg/min. 1
Calculation Process
Determine the appropriate initial dose:
- Initial noradrenaline dose: 0.05-0.1 μg/kg/min 1
- For a 35 kg patient:
- Lower range: 0.05 μg/kg/min × 35 kg = 1.75 μg/min
- Upper range: 0.1 μg/kg/min × 35 kg = 3.5 μg/min
Standard concentration preparation:
- Standard concentration: 4 mg noradrenaline in 500 ml D5W
- This equals 8 μg/ml (4,000 μg ÷ 500 ml)
Calculate flow rate:
- Lower range: 1.75 μg/min ÷ 8 μg/ml = 0.22 ml/min
- Upper range: 3.5 μg/min ÷ 8 μg/ml = 0.44 ml/min
Convert to drops per minute (microdrip = 60 drops/ml):
- Lower range: 0.22 ml/min × 60 drops/ml = 13.2 ≈ 13 drops/min
- Upper range: 0.44 ml/min × 60 drops/ml = 26.4 ≈ 26 drops/min
Administration Guidelines
- Target MAP: Maintain mean arterial pressure (MAP) ≥65 mmHg 2, 1
- Titration: Increase dose by 0.05-0.1 μg/kg/min (1.75-3.5 μg/min for this patient) every 5-15 minutes based on blood pressure response 1
- Monitoring: Continuous arterial blood pressure monitoring is strongly recommended 1
Important Clinical Considerations
- Early administration: Start noradrenaline early in septic shock, as profound and prolonged hypotension increases mortality 3, 4, 5
- Fluid resuscitation: Ensure adequate fluid resuscitation (minimum 30 ml/kg crystalloids) before or concurrent with noradrenaline initiation 2, 1
- Peripheral administration: When central venous access is unavailable, noradrenaline can be administered through a large peripheral vein using a microdrip system with careful monitoring for extravasation 1
Refractory Hypotension Management
If target MAP cannot be achieved with noradrenaline alone:
- Add vasopressin: Up to 0.03 U/min to either raise MAP or decrease noradrenaline requirements 2, 1
- Consider epinephrine: As an additional agent to maintain adequate blood pressure 2, 1
- Avoid dopamine: Only use in highly selected patients with low risk of tachyarrhythmias 2, 1
Monitoring Parameters
- Continuous blood pressure monitoring
- Tissue perfusion markers (lactate clearance, urine output, mental status)
- Signs of extravasation if administered peripherally
- Cardiac function (if myocardial depression is suspected)
By following these guidelines, you can effectively manage septic shock in this 35 kg patient while minimizing complications and optimizing outcomes.