Postnatal changes of extracellular volume, atrial natriuretic factor, and diuresis in a randomized controlled trial of high-frequency oscillatory ventilation versus intermittent positive-pressure ventilation in premature infants < 30 weeks gestation

Objectives: High-frequency oscillatory ventilation (HFOV) with a high lung volume strategy is an experimental mode of ventilating preterm infants aime d at achieving maximal alveolar recruitment Higher mean airway pressures ar e used during HFOV than during intermittent positive-pressure ventilation ( IPPV), and the intrathoracic volume increase is relatively constant Both fa ctors increase the risk to depress organ blood flow and diuresis. Our objec tive was to test the hypothesis that high lung volume HFOV attenuates the p ostnatal reduction of extracellular volume in preterm infants by reducing p lasma atrial natiuretic factor and diuresis. Design: Prospective, randomized, controlled clinical trial. Setting: University hospital, Level III neonatal intensive care unit. Patients: Premature infants <30 wks gestation requiring intubation for resp iratory distress syndrome within the first 6 hrs of life; 15 infants (gesta tional age, 26 [24-29] wks, birth weight 814 [452-1340] g) were randomized to HFOV, 19 infants (gestational age 27 [24-39] wks, birth weight 930 [644- 1490] g) to IPPV. Interventions: The randomized mode of ventilation was assigned within 1 hr after intubation. During HFOV mean airway pressure was increased as long as oxygenation improved and no lung overinflation was seen on chest radiograp h. IPPV rates were greater than or equal to 60/min. Measurements and Main Results: We measured extracellular volume (sucrose di lution) and atrial natriuretic factor an Day 1 and Day 3, Mean airway press ure, body weight, diuresis, and fluid intake were measured daily. During HF OV mean airway pressure was higher at 12 hrs (median 7 cm H2O vs. 4 cm H2O; p = .001) and 24 hrs (median 6 cm H2O vs. 3 cm H2O; p = .01). In both grou ps, extracellular volume decreased between Day 1 and Day 3 (HFOV from 428 /- 126 mL to 344 +/- 145 mL [p = .003], IPPV from 466 +/- 108 mL to 414 +/- 124 mL [p = .01]) and diuresis increased (HFOV, from 2.5 +/- 1.7 to 4.6 +/ - 0.9 mL/kg/hr [p = .001]; IPPV, from 2.8 +/- 1.6 to 4.2 +/- 1.0 mL/kg/hr ( p =.01]). Plasma atrial natriuretic factor was not decreased in the HFOV gr oup. Conclusions: High lung volume HFOV as primary mode of ventilation in preter m infants <30 wks gestation did not result in unwanted fluid retention and a decrease in diuresis in the first days of life.