Administration of Mephentermine in Infants with Hypotension
There is insufficient evidence to recommend mephentermine for routine use in infants with hypotension. Dopamine (2-20 mcg/kg/min) is the preferred vasopressor for management of hypotension in infants when fluid resuscitation is inadequate.
Current Evidence on Vasopressors in Infants
- The American Academy of Pediatrics and other major pediatric guidelines do not specifically recommend mephentermine for management of hypotension in infants 1
- For hypotension refractory to volume replacement and epinephrine injections in pediatric patients, dopamine is the recommended first-line vasopressor at 2-20 mcg/kg/min 2, 1
- Dopamine should be prepared using the "rule of 6": 0.6 × body weight (kg) = number of milligrams diluted to total 100 mL of saline; then 1 mL/h delivers 0.1 mcg/kg/min 2, 1
Monitoring During Vasopressor Administration
- Continuous hemodynamic monitoring is essential during vasopressor administration in infants 2
- Blood pressure should be monitored continuously, preferably with an arterial line 2
- Extreme caution must be exercised to avoid accidental flushing/bolus injection of the IV line 2
- Watch for extravasation which can cause severe tissue injury; phentolamine (0.1-0.2 mg/kg) can be injected intradermally at extravasation site as a countermeasure 2
Alternative Vasopressors for Infants
- In cases where dopamine is ineffective, epinephrine (0.1-1.0 mcg/kg/min) may be considered 3, 1
- For infants with marked circulatory instability and decompensated shock, epinephrine may be preferable to dopamine 2
- In preterm infants with refractory hypotension, a "stress dose" of hydrocortisone (1 mg/kg every 8 hours) has shown effectiveness when vasopressors are inadequate 4
Special Considerations in Neonates
- Preterm infants require a more cautious approach to volume resuscitation and vasopressor therapy compared to term neonates and children 1
- Low birth weight infants with early systemic hypotension (<24 hours of life) may respond to either dopamine (2.5-10 mcg/kg/min) or epinephrine (0.125-0.5 mcg/kg/min) 3
- The use of vasopressors in extremely preterm infants has been associated with higher risk of severe intraventricular hemorrhage, requiring careful consideration of risks and benefits 5
Defining Hypotension in Infants
- Hypotension is defined by age-specific parameters 1:
- Term neonates (0-28 days): Systolic BP <60 mmHg
- Infants (1-12 months): Systolic BP <70 mmHg
- Children (>1 year to 10 years): Systolic BP <70 + (2 × age in years) mmHg
Important Cautions
- While mephentermine has been studied in adults for management of hypotension during spinal anesthesia 6, 7, there is insufficient evidence for its safety and efficacy in infants
- Bottle, burette, or syringe pump containing vasopressors should be covered with protective foil to avoid breakdown by light 1
- In infants with underlying cardiac dysfunction and/or signs of volume overload, additional fluid boluses should be avoided to prevent pulmonary edema 1