Recommended Doses for Medications in Critical Care
Magnesium Sulfate
For torsades de pointes or refractory ventricular arrhythmias: 25-50 mg/kg IV/IO over 10-20 minutes (maximum 2 g), administered faster in torsades de pointes 1. In pediatric patients, this same dosing applies 1.
For severe pre-eclampsia/eclampsia, the FDA-approved regimen is 4-5 g IV loading dose over 5-15 minutes, followed by 1-2 g/hour continuous infusion 2. The WHO guidelines specify 4 g IV loading dose over 5-15 minutes, followed by 1 g/hour maintenance infusion for 24 hours 3. Total daily dose should not exceed 30-40 g 2.
For persistent bronchospasm in anaphylaxis, consider magnesium as adjunctive therapy 4, though specific dosing is not detailed in the anesthesia guidelines.
N-Acetylcysteine (NAC)
No established dose for sepsis management exists in current guidelines. Research studies have used 600 mg orally three times daily 5 or IV formulations 6, but these remain investigational. The evidence does not support routine use of NAC in sepsis outside clinical trials 7.
Vitamin C (Ascorbic Acid)
No guideline-recommended dose for sepsis exists. Research protocols have used 1.5 g IV every 6 hours for 4 days 8, 9, but large randomized trials showed no significant benefit on mortality or vasopressor-free days 8. Vitamin C is not recommended for routine sepsis management 7.
Thiamine
100 mg IV every 6-8 hours for 4 days has been studied in sepsis research protocols 8, 9. One trial suggested potential renal protective effects and improved lactate clearance 10, but thiamine remains investigational and is not recommended for routine sepsis use outside clinical trials 7.
Hydrocortisone
For refractory septic shock requiring high-dose vasopressors: 50 mg IV every 6 hours OR 200 mg/day continuous infusion for 7 days or until ICU discharge 11. This should be initiated after at least 4 hours of norepinephrine or epinephrine at ≥0.25 mcg/kg/min 12.
For anaphylaxis in adults: 200 mg IV 4. Pediatric dosing: >12 years: 200 mg; 6-12 years: 100 mg; 6 months-6 years: 50 mg; <6 months: 25 mg 4.
For acute asthma: 1-2 mg/kg IV initial dose (acetate salt for IM) 13.
Trimetazidine
No established dose for acute cardiac conditions exists in guidelines. Research has used 3-5 mg/kg IV in animal models of myocardial ischemia-reperfusion 14, but this remains experimental and is not recommended for clinical use.
Norepinephrine
Starting dose: 0.01-0.02 mcg/kg/min IV, titrated to maintain MAP ≥65 mmHg 12, 11. The range extends to 0.1-0.5 mcg/kg/min as needed 11. Norepinephrine is the first-line vasopressor for septic shock 12, 11, 15.
If MAP remains inadequate despite low-moderate norepinephrine doses (0.1-0.2 mcg/kg/min), add vasopressin 0.04 units/min (not weight-based) 12, 11. Vasopressin should not exceed 0.03 units/min in some protocols 15.
For persistent hypoperfusion despite adequate volume and blood pressure, consider adding epinephrine 12.
Critical Caveats
The HAT protocol (Hydrocortisone, Ascorbic acid, Thiamine) is NOT recommended for routine use despite early enthusiasm. Large trials showed no mortality benefit 8, 9, 7.
Magnesium sulfate use beyond 5-7 days in pregnancy can cause fetal abnormalities 2.
Norepinephrine should be started peripherally if central access is not immediately available—do not delay vasopressor initiation 11.
Monitor for magnesium toxicity: absent reflexes, respiratory depression, bradycardia 3, 13.