Different doses of exogenous surfactant for treatment of meconium aspiration syndrome in newborn rabbits.
OBJECTIVE
To evaluate the effects of 2 different doses of exogenous surfactant on pulmonary mechanics and on the regularity of pulmonary parenchyma inflation in newborn rabbits.


METHODS
Newborn rabbits were submitted to tracheostomy and randomized into 4 study groups: the Control group did not receive any material inside the trachea; the MEC group was instilled with meconium, without surfactant treatment; the S100 and S200 groups were instilled with meconium and were treated with 100 and 200 mg/kg of exogenous surfactant (produced by Instituto Butantan) respectively. Animals from the 4 groups were mechanically ventilated during a 25-minute period. Dynamic compliance, ventilatory pressure, tidal volume, and maximum lung volume (P-V curve) were evaluated. Histological analysis was conducted using the mean linear intercept (Lm), and the lung tissue distortion index (SDI) was derived from the standard deviation of the means of the Lm. One-way analysis of variance was used with a = 0.05.


RESULTS
After 25 minutes of ventilation, dynamic compliance (mL/cm H2O.kg) was 0.87 +/- 0.07 (Control); 0.49 +/- 0.04 (MEC*); 0.67 +/- 0.06 (S100); and 0.67 +/- 0.08 (S200), and ventilatory pressure (cm H2O) was 9.0 +/- 0.9 (Control); 16.5 +/- 1.7 (MEC*); 12.4 +/- 1.1 (S100); and 12.1 +/- 1.5 (S200). Both treated groups had lower Lm values and more homogeneity in the lung parenchyma compared to the MEC group: SDI = 7.5 +/- 1.9 (Control); 11.3 +/- 2.5 (MEC*), 5.8 +/- 1.9 (S100); and 6.7 +/- 1.7 (S200) (*P < 0.05 versus all the other groups).


CONCLUSIONS
Animals treated with surfactant showed significant improvement in pulmonary mechanics and more regularity of the lung parenchyma in comparison to untreated animals. There was no difference in results after treatment with either of the doses used.
Lyra
João Cesar
JC
Department of Pediatrics, School of Medicine of Botucatu, State University of São Paulo (UNESP), São Paulo, SP, Brazil. jc.lyra@uol.com.br
Mascaretti
Renata S
RS
Precioso
Alexander Roberto
AR
Chang
Yin Chia
YC
Costa
Maria Tereza Zulini da
MT
Vaz
Flávio Adolfo Costa
FA
Okay
Yassuhiko
Y
Rebello
Celso Moura
CM
D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008170:Lung Compliance / Q000187:drug effects*; D008297:Male; D008471:Meconium Aspiration Syndrome / Q000188:drug therapy*; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D011663:Pulmonary Surfactants / Q000008:administration & dosage*; D011817:Rabbits; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000187:drug effects*; D013997:Time Factors
D011663:Pulmonary Surfactants