Initial systolic time intervals as predictors of the severity of transient tachypnea in term neonates

Structural cardiac lesions in transient tachypnea of the newborn

BACKGROUND

Transient tachypnea of the newborn (TTN) is considered a benign disorder. Given its self-limiting nature, few studies have looked for associated pathology. This study explores the association of TTN with structural cardiac lesions.

METHODS

Over a six-month period, all inborn term and late preterm neonates with TTN (without predisposing factors) underwent 2D echocardiography within the first ten days of life, after tachypnea had subsided. Equal number of neonates born during the same period, matched for birth weight, gestational age, sex, and mode of delivery but without tachypnea, also underwent echocardiography before ten days of life. The cardiologist performing the echocardiography was blinded to the presence or absence of tachypnea.

RESULTS

Thirty-six neonates with tachypnea and equal number of controls underwent echocardiography. Due to matching, there was no significant difference in birth weight, gestational age, sex, or mode of delivery between the two groups. Mean age at echocardiography also did not significantly differ. Neonates with TTN had significantly more structural cardiac lesions than those without (16 [44.44%] vs 5 [13.39%]; p < 0.009).

CONCLUSION

Significantly more neonates with TTN have associated structural cardiac lesions. All neonates with TTN should be screened for underlying structural cardiac lesions.

Role of digoxin-like immunoreactive substance in the pathogenesis of transient tachypnea of newborn

Background. Transient tachypnea of newborn (TTN) is usually observed in term or near-term infants. It constitutes an important part of the respiratory distress cases observed in the neonatal intensive care unit (NICU). Aim. This paper examines the effects of digoxin-like immunoreactive substance (DLIS) on fluid and ion balance, hemodynamic and echocardiographic parameters of neonates with TTN. Methods. Plasma DLIS, Na⁺, K⁺, urea, creatinine, serum and urine osmolarity, urine FeNa⁺, 24-hour urine output, echocardiographic investigation and mean blood pressure, and clinical parameters of disease severity were recorded in TTN group and compared with control on the 1st and 7th days of their lives. Results. Plasma DLIS levels were statistically higher in TTN group (0.66 ± 0.37 ng/mL) compared to control group (0.24 ± 0.20 ng/mL) both on the 1st day (P < 0.01) and the 7th day (P < 0.05). For TTN group, significant correlation was found between plasma DLIS levels and maximum respiratory rate, duration of tachypnea, and length of hospitalization on the 1st day. Plasma DLIS levels were correlated negatively with serum osmolarity levels. Plasma DLIS levels were positively correlated with urine output, urinary FeNa⁺ levels, cardiac output, left ventricles end diastolic diameters, and right ventricles end diastolic diameters. Conclusions. Increased DLIS levels were correlated with disease severity in cases with TTN. This increase may be a primary or secondary event in the disease progress. It may help reduce the fluid overload due to already disturbed cardiac functions in patients by increasing urine output and natriuresis; however it may also contribute to disease pathogenesis, by inhibiting alveolar Na⁺-K⁺-ATPase which further decreases fetal alveolar fluid resorption.

Effects of dobutamine on left ventricular performance in newborns as determined by systolic time intervals

To evaluate the effects of dobutamine on myocardial function in newborns, left ventricular systolic time intervals (STI) - normalized pre-ejection period (PEPI), normalized left ventricular ejection time (LVETI) and pre-ejection period to left ventricular ejection time ratio (PEP/LVET) - were assessed by echocardiography in 18 newborns treated with dobutamine for clinically diagnosed heart failure. Examinations were performed prior to and 30 min after starting dobutamine infusion (7.5 or 10 micrograms/kg per min). Patients were assigned to two groups according to their PEP/LVET prior to dobutamine administration: group I (n = 9) with pre-treatment PEP/LVET less than or equal to 0.35 and group II (n = 9) with pre-treatment PEP/LVET greater than 0.35. While there was no change of STI in group I, dobutamine infusion resulted in a significant decrease in PEPI (from 102 +/- 4.8 to 87.8 +/- 4.2; mean +/- SEM; P less than 0.01) and of PEP/LVET (from 0.56 +/- 0.05 to 0.45 +/- 0.05; mean +/- SEM; P less than 0.01) and in a significant increase of LVETI (from 237.6 +/- 5.6 to 253.3 +/- 5.2; mean +/- SEM; P less than 0.01) in group II. Heart rate increased significantly in both groups. Left ventricular end-diastolic dimension, also assessed by echocardiography, did not change in the eight studies performed. An increase in mean arterial pressure was found in three out of five newborns of group II and in one out of four patients in group I. It is concluded that dobutamine can improve cardiac performance in newborns with impaired left ventricular function. This effect is probably due to an improvement in myocardial contractility.