eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Neonatology
Meconium Aspiration Syndrome: Treatment & Medication
Updated: Dec 2, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Treatment
Medical Care
- Prevention of meconium aspiration syndrome (MAS)
- Prevention is paramount.
- Obstetricians should monitor fetal status in an attempt to identify fetal stress.
- When meconium is detected, administering amnioinfusion with warm, sterile saline is theoretically beneficial; it dilutes the meconium in the amniotic fluid, thereby minimizing the severity of the aspiration. However, routine amnioinfusion to prevent meconium aspiration syndrome is not well-supported by current evidence.
- Current recommendations no longer advise routine intrapartum suctioning for infants born to mothers with meconium staining of the amniotic fluid.1
- When aspiration occurs, intubation and immediate suctioning of the airway can remove much of the aspirated meconium.
- No clinical trials justify suctioning based on the consistency of meconium. Do not perform the following harmful techniques in an attempt to prevent aspiration of meconium-stained amniotic fluid:
- Squeezing the chest of the baby
- Inserting a finger into the mouth of the baby
- The American Academy of Pediatrics Neonatal Resuscitation Program Steering Committee has promulgated guidelines for management of the baby exposed to meconium. The guidelines are under continuous review and are revised as new evidence-based research becomes available. The current guidelines are as follows:2
- If the baby is not vigorous (defined as minimal or absent respiratory effort, poor muscle tone, or heart rate <100 beats/min): Use direct laryngoscopy, intubate, and suction the trachea immediately after delivery. Suction for no longer than 5 seconds. If no meconium is retrieved, do not repeat intubation and suction. If meconium is retrieved and no bradycardia is present, reintubate and suction. If the heart rate is low, administer positive pressure ventilation and consider suctioning again later.
- If the baby is vigorous (defined as good respiratory effort, crying, good muscle tone, and heart rate >100 beats/min): Do not electively intubate. Clear secretions and meconium from the mouth and nose with a bulb syringe or a large-bore suction catheter.
- In either case: The remainder of the initial resuscitation steps should ensue and include drying, stimulating, repositioning, and administering oxygen as necessary.
- Continued care in the neonatal ICU (NICU)
- Maintain an optimal thermal environment to minimize oxygen consumption.
- Minimal handling is necessary because these infants are easily agitated, which causes right-to-left shunting, leading to hypoxia and acidosis.
- Sedation is often necessary to decrease agitation.
- Continue respiratory care. Oxygen therapy via hood or positive pressure is crucial in maintaining adequate arterial oxygenation. If mechanical ventilation is required, make concerted efforts to minimize the mean airway pressure and to use as short an inspiratory time as possible. Oxygen saturations should be maintained at 90-95%.
- Surfactant therapy is now commonly used to replace displaced or inactivated surfactant and as a detergent to remove meconium. Although surfactant use does not appear to affect mortality rates, it appears to reduce the severity of disease and progression to extracorporeal membrane oxygenation (ECMO).3 Studies are ongoing to evaluate the potential role of pulmonary lavage with surfactant.
- Although conventional ventilation commonly is initially used, high-frequency oscillation and jet ventilation are alternative effective therapies. Hyperventilation to induce hypocapnia and compensate for metabolic acidosis is no longer a primary therapy for pulmonary hypertension because hypocarbia may result in decreased cerebral perfusion (PaCO 2 <30 mm Hg). Prolonged alkalosis has been shown to cause neuronal injury in animals and humans, providing another reason to avoid alkalosis in these patients.4
- Ventilator therapy aimed at minimizing mean airway pressure and tidal volume should be used if pulmonary interstitial emphysema or a pneumothorax is present.
- For treatment of persistent pulmonary hypertension of the newborn (PPHN), inhaled nitric oxide is the pulmonary vasodilator of choice.
- Pay careful attention to systemic blood volume and blood pressure. Volume expansion, transfusion therapy, and systemic vasopressors are critical in maintaining systemic blood pressure greater than pulmonary blood pressure, thereby decreasing the right-to-left shunt through the patent ductus arteriosus.
- ECMO is used if all other therapeutic options have been exhausted. Although effective in treating meconium aspiration syndrome, ECMO is associated with a high incidence of poor neurologic outcomes.
Surgical Care
- Although primary management of air block syndromes (pneumothorax or pneumopericardium) is achieved by thoracic drainage tubes inserted by a neonatologist, a pediatric surgical consultation may be necessary in severe cases. Therapy with fibrin glue has been shown to be effective in patients with a persistent air leak.
Consultations
- Evaluation with a pediatric cardiologist is necessary for echocardiographic assessment. This imaging technique ensures normal cardiac structure and assesses the severity of pulmonary hypertension and right-to-left shunting.
- Evaluation with a pediatric neurologist is helpful in the presence of neonatal encephalopathy or seizure activity.
Diet
- Perinatal distress and severe respiratory distress preclude feeding.
- Intravenous fluid therapy begins with adequate dextrose infusion to prevent hypoglycemia.
- Intravenous fluids should be provided at mildly restricted rates (60-70 mL/kg/d).
- Progressively add electrolytes, protein, lipids, and vitamins to ensure adequate nutrition and prevent essential amino acid and essential fatty acid deficiencies.
Medication
In addition to the treatments listed below, surfactant replacement therapy is frequently used. Natural lung extract is administered to replace the surfactant that has been stripped. Surfactant also acts as a detergent to break up residual meconium, thereby decreasing the severity of lung disease. Surfactant is used in patients with meconium aspiration syndrome (MAS); however, its efficacy, dosage regimen, and most effective product are not yet established.
Respiratory gases
Inhaled nitric oxide (NO) has the direct effect of pulmonary vasodilatation without the adverse effect of systemic hypotension. It is approved for use, if concomitant hypoxemic respiratory failure occurs.
Nitric oxide, inhaled (INOmax)
Endogenously produced from the action of the enzyme NO synthetase on arginine. Exogenously inhaled NO is used in an attempt to decrease pulmonary vascular resistance and improve lung blood flow. It relaxes vascular smooth muscle by binding to the heme moiety of cytosolic guanylate cyclase, activating guanylate cyclase and increasing intracellular levels of cGMP, which then leads to vasodilation.
Adult
Pediatric
20 ppm inhaled via respirator initially; not to exceed 80 ppm; most children respond at 20 ppm and can be weaned to lower doses; effect of pulmonary vasodilatation may still be observed at 5 ppm
Must be delivered by a system that measures concentrations of NO in the breathing gas, with a constant concentration throughout the respiratory cycle and that does not cause generation of excessive inhaled nitrogen dioxide
Nitric oxide donor compounds (eg, nitroprusside, nitroglycerin) may increase risk of developing methemoglobinemia
Right to left shunting of blood; methemoglobin reductase deficiency
Pregnancy
Precautions
Toxic effects include methemoglobinemia and pulmonary inflammation resulting from reactive nitrogen intermediates; caution in thrombocytopenia, anemia, leukopenia, or bleeding disorders; monitor for PaO2, methemoglobin, and NO2; abrupt withdrawal causes rebound pulmonary hypertension
Systemic vasoconstrictors
These agents are used to prevent right-to-left shunting by raising systemic pressure above pulmonary pressure. Systemic vasoconstrictors include dopamine, dobutamine, and epinephrine. Dopamine is the most commonly used.
Dopamine (Intropin)
At lower doses, dopamine stimulates beta1-adrenergic and dopaminergic receptors (renal vasodilation, positive inotropism); at higher doses, it stimulates alpha-adrenergic receptors (renal vasoconstriction).
Adult
Pediatric
5-20 mcg/kg/min IV
Incompatible when admixed with acyclovir, amphotericin B, indomethacin, insulin, and sodium bicarbonate
Phenytoin, alpha-adrenergic and beta-adrenergic blockers, general anesthesia, and MAOIs increase and prolong effects of dopamine
Documented hypersensitivity (rare in neonatal population); outflow tract obstructions such as subaortic stenosis
Pregnancy
Precautions
Adverse effects include tachycardia and arrhythmia; treat hypovolemia before infusion; promptly treat extravasation with SC phentolamine; administration through a central vein is recommended; do not use a systemic or umbilical artery for infusion; if dosages >20 mcg/kg/min are required, consider a different agent (eg, epinephrine, dobutamine)
Monitor closely urine flow, cardiac output, pulmonary wedge pressure, and blood pressure during the infusion; before infusion, correct hypovolemia as indicated; monitoring central venous pressure or left ventricular filling pressure may be helpful in detecting and treating hypovolemia
Dobutamine (Dobutrex)
Increases blood pressure primarily via stimulation of beta1-adrenergic receptors. Drug appears to have more prominent effect on cardiac output than on blood pressure.
Adult
Pediatric
2-25 mcg/kg/min IV continuous infusion; initiate at low dose and titrate while monitoring effects
Beta-adrenergic blockers antagonize effects of dobutamine; general anesthetics may increase toxicity
Documented hypersensitivity; idiopathic hypertrophic subaortic stenosis and atrial fibrillation or flutter
Pregnancy
Precautions
Following a myocardial infarction use with extreme caution; hypovolemic state should be corrected before using this drug
Epinephrine
Used for severe bronchoconstriction, especially in patients with underlying reactive airways disease. Alpha-agonist effects include increased peripheral vascular resistance, reversed peripheral vasodilatation, systemic hypotension, and vascular permeability. Beta2-agonist effects include bronchodilatation, chronotropic cardiac activity, and positive inotropic effects.
Adult
Pediatric
0.1 mcg/kg/min IV initially; gradually titrate dose; not to exceed 1 mcg/kg/min
Increases toxicity of beta-blocking and alpha-blocking agents and that of halogenated inhalational anesthetics
Documented hypersensitivity; cardiac arrhythmias, angle-closure glaucoma; local anesthesia in areas such as fingers or toes because vasoconstriction may produce sloughing of tissue; during labor (may delay second stage of labor)
Pregnancy
Precautions
Caution in elderly, prostatic hypertrophy, hypertension, cardiovascular disease, diabetes mellitus, hyperthyroidism, and cerebrovascular insufficiency; rapid IV infusions may cause death from cerebrovascular hemorrhage or cardiac arrhythmias
Sedatives
These agents maximize efficiency of mechanical ventilation, minimize oxygen consumption, and treat the discomfort of invasive therapies.
Morphine
Used for analgesia and sedation.
Adult
Pediatric
0.05-0.2 mg/kg/dose IV over 5 min q2-4h prn
Any CNS depressant; phenothiazines may antagonize analgesic effects of opiate agonists; tricyclic antidepressants, MAOIs, and other CNS depressants may potentiate adverse effects of morphine; incompatible when admixed with furosemide, pentobarbital, phenobarbital, or phenytoin (forms precipitant)
Documented hypersensitivity (rare in neonates); severe respiratory depression
Pregnancy
Precautions
Caution in hypotension, respiratory depression, nausea, emesis, constipation, urinary retention, atrial flutter, and other supraventricular tachycardias; has vagolytic action and may increase ventricular response rate; may cause histamine release
Fentanyl (Sublimaze)
Potent opioid used for analgesia, sedation, and anesthesia. Has a shorter duration of action than morphine.
Adult
Pediatric
1-4 mcg/kg/dose IV slow push
Infusion rate: 1-5 mcg/kg/h IV
Barbiturates (eg, pentobarbital, thiopental) or other CNS depressants may have additive effects; phenothiazines may antagonize analgesic effects of opiate agonists; tricyclic antidepressants may potentiate adverse effects of fentanyl when both drugs are used concurrently
Documented hypersensitivity (rare in neonates); hypotension or potentially compromised airway in which establishing rapid airway control is difficult
Pregnancy
Precautions
May cause marked respiratory depression and hypotension; exercise caution with patients diagnosed with emesis, constipation, or urinary retention; idiosyncratic reaction (ie, chest wall rigidity syndrome) may require neuromuscular blockade to increase ventilation
Phenobarbital (Luminal)
An anticonvulsant that may be used as a sedative. Suppresses the CNS from the reticular activating system (ie, presynaptic, postsynaptic).
Adult
Pediatric
20 mg/kg IV as a single loading dose, administer slowly over 10-15 min. Maintenance dose is 3-5 mg/kg/day
Incompatible when admixed with clindamycin, hydralazine, insulin, methadone, midazolam, morphine, ranitidine, and vancomycin; may cause respiratory depression if concurrently on CNS depressants (eg, benzodiazepines); decreases effectiveness of corticosteroids, theophylline, and beta-blockers
Documented hypersensitivity (rare in neonates); severe uncontrolled pain
Pregnancy
Precautions
Rarely causes respiratory depression at this dose; do not administer IV administration faster than 50 mg/min; carefully monitor upon administration for hypotension, bradycardia, and arrhythmias because parental product contains 68% propylene glycol; paradoxical excitement and delirium may occur in infants experiencing pain
Pentobarbital (Nembutal)
CNS sedative and hypnotic that acts primarily on the cerebral cortex and reticular formation through decreased neuronal synaptic activity.
Adult
Pediatric
2-6 mg/kg IV slow push
Incompatible when admixed with cefazolin, cimetidine, clindamycin, fentanyl, hydrocortisone, insulin, midazolam, morphine, pancuronium bromide, phenytoin, ranitidine, or vancomycin; may cause respiratory depression with concurrent use of CNS depressants (eg, benzodiazepines); increased toxicity with CNS depressants and possibly phenobarbital
Documented hypersensitivity (rare in neonates); severe uncontrolled pain
Pregnancy
Precautions
Caution with hypovolemic shock, CHF, hepatic impairment, chronic or acute pain, or renal dysfunction; may cause respiratory and cardiovascular depression; carefully monitor upon administration for hypotension, bradycardia, and arrhythmias because parental product contains 68% propylene glycol; paradoxical excitement and delirium may occur in infants experiencing pain
Neuromuscular blocking agents
These agents are used for skeletal muscle paralysis to maximize ventilation by improving oxygenation and ventilation. They are also used to reduce barotrauma and minimize oxygen consumption.
Pancuronium (Pavulon)
Neuromuscular blocker whose effects are reversed by neostigmine and atropine.
Adult
Pediatric
Initial dose: 0.1 mg/kg (0.04-0.15 mg/kg) IV push
Maintenance dose: 0.02-0.1 mg/kg/dose q30min to q3h prn
Dose-dependent increased toxicity with magnesium sulfate and furosemide (increase or decrease neuromuscular blockade); caution with coadministration with drugs that increase neuromuscular blockade (eg, aminoglycosides, inhaled anesthetics); avoid drugs that antagonize neuromuscular blockade or prolong muscular weakness (eg, corticosteroids, amphotericin B, phenytoin, verapamil)
Documented hypersensitivity (rare in neonates)
Pregnancy
Precautions
May cause hypoxemia (unlikely in a ventilated patient), tachycardia, BP changes, and excessive salivation; exercise caution in patients with preexisting pulmonary, hepatic, or renal disease; prolonged use may result in muscle delayed recovery of paralysis
More on Meconium Aspiration Syndrome |
| Overview: Meconium Aspiration Syndrome |
| Differential Diagnoses & Workup: Meconium Aspiration Syndrome |
 Treatment & Medication: Meconium Aspiration Syndrome |
| Follow-up: Meconium Aspiration Syndrome |
| Multimedia: Meconium Aspiration Syndrome |
| References |
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References
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Further Reading
Keywords
meconium aspiration syndrome, MAS, meconium-stained amniotic fluid, fetal hypoxic distress, intrauterine distress, placental insufficiency, maternal hypertension, preeclampsia, oligohydramnios, maternal drug abuse, neonatal respiratory distress, airway obstruction, surfactant dysfunction, chemical pneumonitis, pulmonary hypertension, atelectasis, persistent pulmonary hypertension of the newborn, PPHN, pneumothorax, pneumomediastinum, pneumopericardium, pulmonary interstitial emphysema, respiratory acidosis, metabolic acidosis, syndrome of inappropriate secretion of antidiuretic hormone, SIADH
