What is the starting dose for a norepinephrine (levophed) drip for a 50kg elderly patient?

Norepinephrine Drip Calculation for 50kg Elderly Patient

Start norepinephrine at 0.5 mg/h (approximately 8 mcg/min or 0.1-0.2 mcg/kg/min for this 50kg patient) via continuous IV infusion, preferably through central venous access, while ensuring adequate fluid resuscitation with at least 30 mL/kg (1500 mL) crystalloid bolus. 1, 2

Standard Preparation and Concentration

• Add 4 mg of norepinephrine to 250 mL of D5W to yield a concentration of 16 mcg/mL 1
• The FDA-approved dilution is 4 mg/4 mL vial added to 1,000 mL of 5% dextrose solution, yielding 4 mcg/mL 2
• Saline solution alone is not recommended due to oxidation risk; use dextrose-containing solutions 2

Initial Dosing for 50kg Elderly Patient

• Start at 0.5 mg/h (8 mcg/min), which equals approximately 0.16 mcg/kg/min for this 50kg patient 1, 2
• The FDA label recommends initial dosing of 2-3 mL/min (8-12 mcg/min) of the 4 mcg/mL solution 2
• For elderly patients, use the lower end of the dosing range due to age-related pharmacodynamic changes 3

Titration Protocol

• Titrate by 0.5 mg/h increments every 4 hours to a maximum of 3 mg/h 1
• Target mean arterial pressure (MAP) of 65 mmHg 1
• Monitor blood pressure every 5-15 minutes during initial titration 1
• Adjust rate to establish and maintain low normal blood pressure (80-100 mmHg systolic) 2

Critical Pre-Administration Requirements

• Administer minimum 30 mL/kg (1500 mL for 50kg patient) crystalloid bolus before or concurrent with norepinephrine initiation 1
• Use balanced crystalloids (lactated Ringer's or Plasma-Lyte) preferentially over normal saline 1
• Blood volume depletion must be corrected as fully as possible before vasopressor administration 2

Administration Route

• Central venous access is strongly preferred to minimize extravasation risk and tissue necrosis 1, 2
• Insert plastic IV catheter through suitable bore needle well advanced centrally into vein 2
• If central access unavailable, peripheral IV can be used temporarily with strict monitoring 1
• Place arterial catheter as soon as practical for continuous blood pressure monitoring 1

Monitoring Parameters

• Blood pressure and heart rate every 5-15 minutes during titration 1
• Tissue perfusion markers: lactate clearance, urine output >50 mL/h, mental status, capillary refill 1
• Watch for signs of excessive vasoconstriction: cold extremities, decreased urine output 1
• Monitor for potential side effects: hypertension, arrhythmias, tissue ischemia 1

Escalation for Refractory Hypotension

• When norepinephrine reaches 0.25 mcg/kg/min (12.5 mcg/min for 50kg patient) and hypotension persists, add vasopressin 0.03-0.04 units/min 1
• Consider adding epinephrine 0.1-0.5 mcg/kg/min if vasopressin inadequate 1
• For persistent hypoperfusion despite adequate vasopressors, add dobutamine up to 20 mcg/kg/min 1

Special Considerations for Elderly Patients

• Elderly patients are more susceptible to adverse effects due to age-related pharmacokinetic and pharmacodynamic changes 3
• Progressive decline in homeostatic mechanisms means drug effects are mitigated less, with stronger reactions than younger subjects 3
• Postural hypotension with blood pressure-lowering agents is augmented in elderly 3
• Monitor closely for cognitive impairment, as the brain is especially sensitive in old age 3

Extravasation Management

• If extravasation occurs, infiltrate phentolamine 5-10 mg diluted in 10-15 mL of saline intradermally at the site immediately 1
• Norepinephrine can cause severe tissue necrosis with extravasation 1

Duration of Therapy

• Continue infusion until adequate blood pressure and tissue perfusion maintained without therapy 2
• Reduce gradually, avoiding abrupt withdrawal 2
• Treatment may be required for up to 6 days in some cases of vascular collapse 2

Common Pitfalls to Avoid

• Never start norepinephrine without addressing hypovolemia first - vasoconstriction in hypovolemic patients causes severe organ hypoperfusion despite "normal" blood pressure 1
• Do not mix with sodium bicarbonate or alkaline solutions in IV line - adrenergic agents are inactivated 1
• Avoid using dopamine as first-line agent - associated with higher mortality and arrhythmias 1
• Do not use phenylephrine as first-line therapy - may raise blood pressure while worsening tissue perfusion 1