Treatment of the Respiratory Distress Syndrome
Jonathan M. Klein, MD
Peer Review Status: Internally Peer Reviewed
The treatment of the Respiratory Distress Syndrome (RDS) is directed at correction of the pathophysiological conditions that exist in this disease process: A) surfactant deficiency, B) hypoxia, C) acidosis, D) pulmonary vasoconstriction, E) atelectasis, and F) shock.
SURFACTANT REPLACEMENT THERAPY (page 64)
Correction of hypoxia with oxygen. Infants requiring increased ambient oxygen concentration, and who are breathing spontaneously, can be placed on NPCPAP. The concentration of inspired oxygen should maintain the infant's arterial oxygen tension at 50-70 mm Hg. If oxygen required is greater than 50%, consider endotracheal intubation with surfactant replacement (see relevant section). Always confirm diagnosis with a chest radiograph.
Nasal pharyngeal CPAP for RDS should start at 6 cm H2O. If the infant is having recurrent apnea, persistent respiratory acidosis (pH less than 7.20) or if the PaO2 is inadequate in 50% or more oxygen with usage of nasal CPAP, the infant should be intubated and treated with surfactant.
Once intubated, the neonate with RDS should be ventilated by a pressure respirator according to the protocol found on page 36. To minimize both barotrauma and BPD, peak inspiratory pressures should be decreased as tolerated to keep the pCO2 between 40 and 60 mm Hg as long as the pH > 7.25. If pCO2 remains above 60 mm Hg, consider increasing the respiratory rate first, then, if necessary, increase PIP.
If barotrauma occurs (PIE or pneumothorax), consider high frequency ventilation (see separate section on HFV).
To maintain body temperature, the infant is placed in an incubator or on a radiant heater bed. The skin probe is placed on the mid-epigastrium and covered with heat reflecting tape. The servocontroller is set at 36.5°C.
Intravenous fluids (D10W or D5W) are given at an initial rate of 60-80 ml/kg body weight per 24 hours with fluid therapy reassessed every 8-12 hours. Infants with birth weights less than 750g should be given fluids at an initial rate of 80-150 ml/kg per day due to their increased insensible losses and fluid therapy should be reassessed every 6-8 hours. Sodium received as sodium bicarbonate will also have to be taken into consideration when calculating the daily sodium requirement. IT IS IMPERATIVE THAT FLUID THERAPY BE READJUSTED EVERY 8 TO 12 HOURS, BASED ON INTAKE AND OUTPUT, CHANGE IN BODY WEIGHT, SERUM ELECTROLYTE CONCENTRATIONS AND SERUM AND URINE OSMOLALITY DETERMINATIONS. See section on fluid therapy for additional details.
Metabolic acidosis (pH< 7.20) is corrected by a slow infusion of sodium bicarbonate (0.5 mEq/ml.; 4% solution) through a peripheral IV at the rate of 1 mEq/kg body weight per hour. The formula for calculation of the base deficit is: mEq of NaHCO3 = base excess x 0.6 x body weight in kg. Give one-half of the calculated dose and then recheck pH and pCO2 within one-half hour.
Shock is corrected by use of normal saline or Plasmanate R; the dose is 10 cc/kg infused over 15 to 30 minutes. Normal values for systolic and mean aortic pressures are found on pages 1 and 2. Please note the values for infants <1000 grams. Carefully evaluate the need for correction of low BP based on numbers alone in a premature infant who is otherwise well oxygenated, since acute changes in blood pressure may be an etiologic factor in intracranial hemorrhage.
Oral feedings may be initiated even if the infant is mechanically ventilated, or on nasal-pharyngeal CPAP, however, feedings should not be initiated until the infant's condition is stable. Ultimately, the oral intake should provide 100-120 calories/kg/day (see feeding protocol).
When the infant is on CPAP or mechanical ventilation, a chest film should be obtained immediately after initiating therapy and subsequently at least once every 24 hours until the infant's condition is stable.
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