How should I calculate and administer a weight‑based bolus dose of an emergency medication, including route, preparation, infusion rate, and monitoring?

Weight-Based Bolus Dosing for Emergency Medications

General Principles for Bolus Administration

For emergency medications requiring bolus dosing, calculate the dose using the patient's actual body weight in kilograms, prepare the medication in the appropriate concentration, administer via the most proximal IV or intraosseous (IO) route available, and follow immediately with a rapid saline flush using a 2-syringe technique (up to 20 mL in older children). 1

Route Selection and Access

• Use the most proximal IV site possible for bolus medication administration to ensure rapid drug delivery to central circulation 1
• IO access is acceptable when IV access has not been achieved, particularly for medications like adenosine, epinephrine, atropine, and amiodarone 1
• Avoid repeated injections at the same site as resulting vasoconstriction may cause tissue necrosis 2

Preparation and Administration Technique

• Inspect all medications visually for particulate matter and discoloration prior to administration; do not use if the solution is colored, cloudy, or contains particulate matter 2
• Use a 2-syringe technique with one syringe containing the medication and another containing normal saline for the flush 1
• Administer the saline flush immediately after the medication bolus—a larger flush of up to 20 mL may be helpful in older children 1

Weight-Based Dosing Calculations

Pediatric Dosing Framework

• For children <30 kg (66 lbs): Calculate dose as 0.01 mg/kg for epinephrine, with a maximum of 0.3 mg (0.3 mL) per injection 2
• For children ≥30 kg (66 lbs) and adults: Use 0.3 to 0.5 mg (0.3 mL to 0.5 mL) of epinephrine, up to a maximum of 0.5 mg per injection 2
• For cardiac arrest epinephrine: Administer 0.01 mg/kg IV/IO for neonates via endotracheal route, and 0.03-0.06 mg/kg for children and adolescents 1

Critical Medication-Specific Dosing

Amiodarone:

• Rapid bolus for pulseless VT: 5 mg/kg IV/IO (maximum 300 mg) as a rapid bolus 1
• Stable arrhythmias: 5 mg/kg (maximum 300 mg) over 20-60 minutes, adjusting rate to urgency 1

Atropine:

• IV/IO dose: 0.02 mg/kg with a minimum single dose of 0.1 mg 1
• Maximum single dose: 0.5 mg for a child, 1.0 mg for an adolescent 1
• May repeat every 5 minutes to maximum total dose of 1 mg for a child and 2 mg for an adolescent or adult 1

Magnesium sulfate:

• For torsades de pointes or hypomagnesemia: 25-50 mg/kg IV/IO (maximum 2 g) 1
• Given by bolus for pulseless torsades, over 10-20 minutes for torsades with pulses 1
• Rapid infusion may cause hypotension and bradycardia—have calcium chloride available to reverse magnesium toxicity 1

Benzodiazepines for seizures:

• Lorazepam: 0.05-0.10 mg/kg IV/IM (maximum 4 mg per dose), may repeat every 10-15 minutes 1
• Midazolam: 0.2 mg/kg IM (maximum 6 mg per dose), may repeat every 10-15 minutes 1
• For sedation: 0.05-0.10 mg/kg IV over 2-3 minutes (maximum single dose 5 mg), with peak effect at 3-5 minutes 1

Infusion Rate and Timing Considerations

Rapid Bolus Medications

• Adenosine requires the most rapid administration: Give as fast IV push followed immediately by rapid saline flush 1
• If no response within 30 seconds, double the initial adenosine dose (0.2 mg/kg, up to 12 mg maximum) followed by immediate rapid saline flush 1
• Epinephrine for anaphylaxis: May be repeated every 5 to 10 minutes as necessary, monitoring clinically for reaction severity and cardiac effects 2

Controlled Infusion Rates

• Diltiazem: Initial dose 15-20 mg (0.25 mg/kg) IV over 2 minutes; additional 20-25 mg (0.35 mg/kg) IV in 15 minutes if needed 1
• Metoprolol: 5 mg over 1-2 minutes, repeated as required every 5 minutes to maximum dose of 15 mg 1
• Esmolol: IV loading dose 500 mcg/kg (0.5 mg/kg) over 1 minute, followed by infusion of 50 mcg/kg per minute 1
• Amiodarone for stable arrhythmias: 150 mg given over 10 minutes, followed by 1 mg/min infusion for 6 hours, then 0.5 mg/min 1

Medications Requiring Slower Administration

• Mannitol for increased ICP: 0.25-1 g/kg given over 20-30 minutes; larger doses (0.5 g/kg) may be given over 15 minutes in acute intracranial hypertensive crisis 1
• Milrinone loading dose: 50-75 mcg/kg over 10-60 minutes; longer infusion times reduce the risk of hypotension 1
• Morphine for pain: 0.1 mg/kg IV; if patient is receiving an infusion and develops pain, give a bolus dose of two times the hourly infusion dose 1

Monitoring Requirements

Continuous Monitoring During Administration

• Continuous electrocardiographic monitoring should be employed during adenosine use, with a defibrillator immediately available 1
• Monitor oxygen saturation when administering benzodiazepines and be prepared to provide respiratory support 1
• Monitor blood pressure and ECG continuously during milrinone infusion 1
• For beta-blockers and calcium channel blockers, monitor for hypotension, bradycardia, and precipitation of heart failure 1

Post-Administration Assessment

• Reassess clinical effect every 3-5 minutes after midazolam administration to avoid oversedation 1
• Observe for 30 seconds after adenosine to determine if AV block occurs or if repeat dosing is needed 1
• Monitor clinically for reaction severity and cardiac effects after epinephrine administration 2

Common Pitfalls and How to Avoid Them

Dosing Calculation Errors

• Obtaining an incorrect weight leads to drug dosing errors in 12.7% of cases 3
• Ten-fold errors still occur at a high rate (8.6% overdoses in one study) despite implementation of pediatric dosing references 3
• Unrecognized air entrainment into the administration syringe frequently results in under-dosing 3

Administration Technique Errors

• Drug dilution errors occur in 33.3% of cases when dilution is required, resulting in dosing errors 3
• Failure to use adequate needle length for intramuscular administration—use at least 1/2 inch to 5/8 inch to ensure intramuscular delivery 2
• Not using the most proximal IV site reduces drug delivery speed and effectiveness 1

Medication-Specific Warnings

• Adenosine is contraindicated in patients who have had a heart transplant and in second- or third-degree AV block or sick-sinus syndrome unless a pacemaker has been placed 1
• Amiodarone should not be used in combination with procainamide or other drugs that cause QT prolongation without expert consultation 1
• Beta-blockers should be avoided in patients with asthma, obstructive airway disease, decompensated heart failure, and pre-excited atrial fibrillation or flutter 1
• Calcium channel blockers should only be given to patients with narrow-complex tachycardias—avoid in patients with heart failure and pre-excited AF or flutter or rhythms consistent with VT 1

Monitoring Failures

• Failure to check blood sugar in seizure scenarios represents a common error of omission 3
• Failure to administer epinephrine and fluid bolus in anaphylactic shock represents another common omission error 3