M. Douglas Cunningham

Association of elective repeat cesarean delivery and persistent pulmonary hypertension of the newborn

Seventy-one cases of persistent pulmonary hypertension of the newborn have been reviewed in an attempt to identify possibly preventable causes. Three groups of infants were identified. The first group consisted of 36 infants with evidence of perinatal asphyxia. The second group was made up of 23 infants who exhibited a variety of associated factors including pneumonia, septic shock, and congenital diaphragmatic hernia. A third group included 12 infants delivered by elective repeat cesarean section. Infants in the third group did not have evidence of perinatal asphyxia, meconium aspiration, or infection. Chest roentgenograms revealed amniotic fluid aspiration in seven cases, retained lung fluid in three cases, and normal findings in two cases. All 12 infants in the third group developed respiratory distress which eventually progressed to respiratory failure and persistent pulmonary hypertension of the newborn. These data suggest that infants of elective repeat cesarean deliveries are at risk for developing persistent pulmonary hypertension of the newborn and constitute a group of patients with a potentially preventable course of events.

Echocardiography in hypoxemic neonatal pulmonary disease

Sixteen newborn infants with severe pulmonary parenchymal disease and profound hypoxemia were treated with mechanical ventilation, alkalinization, and intravenous tolazoline. Eight infants responded within two hours of initiation of tolazoline therapy with a rise in Pao2 by at least 100% of pretreatment values (mean = 188%, range = 103 to 427%). Eight infants showed little or no change in Pao2 with administration of tolazoline. Echocardiographic evaluation prior to therapy demonstrated marked elevation in both left (LPEP/LVET = 0.52 +/- 0.13) and right (RPEP/RVET = 0.56 +/- 0.08) ventricular systolic time intervals in the eight infants who subsequently responded to tolazoline. Systolic time intervals in nonresponders were within the normal range (LPEP/LVET = 0.37 +/- 0.03, RPEP/RVET = 0.33 +/- 0.04) and were not significantly different from those observed in a control group of 15 infants with pulmonary disease requiring mechanical ventilation but without hypoxemia. Following tolazoline therapy, systolic time intervals in all eight responders fell to normal values. Echocardiography can provide a safe, noninvasive method for identifying those infants with primary pulmonary disease and severe hypoxemia who could be expected to benefit from tolazoline therapy, thereby avoiding tolazoline side effects in infants for whom tolazoline therapy can be predicted to be of little benefit.

Follow up of low birth weight infants

ConclusionConsiderable reduction in mortality of low birth weight infants over the past two decades has been achieved in developed countries without an increase in the prevalence of major h andicaps in the survivors. In the 1980’s overall prognosis for infants above 800 gm birth weight remains good. Continued efforts for improved perinatal and neonatal care can be expected to further reduce the risk of premature birth. Worldwise effort for improved care of the pregnant women and the newborn can be expected to result in similar advances for infant survival and improved child health.

1709 SURFACTANT CHOLESTEROL AS RELATED TO RESPIRATORY DISTRESS IN PREMATURE INFANTS

The role of cholesterol in surfactant is poorly understood, but it is known to decrease lung surface-tension reducing properties in vitro. We studied lipid components of 24 tracheal aspirates from 16 mechanically ventilated infants, 29-36 wk gestation with respiratory distress (preterm A) and pharyngeal aspirates from 5 normal newborns. Mean airway pressure (Paw) was used as an index of noncompliant lung disease. Cholesterol (Chol) and phospholipids were quantified by thin-layer chromatography and reflectance densitometry. Surfactant of preterm A and normal infants was not significantly different except for diminished phosphatidylglycerol (PG). However, a subgroup of preterm A (preterm B; n=7) had mature lecithin:sphingomyelin ratios (L:S), but reversed lecithin:chol ratios (L:C). The data (±SEM) are as follows:Preterm B infants required 17.3% greater Paw than preterm A infants (9.63 ± 1.6 SEM vs 7.96 ± .6 SEM). Despite a mature L:S, some preterm infants had added lung disease requiring increased Paw when the relationship of Lec to Chol was reversed.

97 DIGOXIN TOXICITY ASSOCIATED WITH LOW DOSAGE MAINTENANCE THERAPY IN PREMATURE INFANTS

Current recommendations for the administration of Digoxin (DIG) to low birthweight (LBW) infants are ill defined. We report the frequent occurrence of DIG toxicity in LBW infants treated with low dose maintenance DIG: 10 μg/kg/da without an initial loading dose. DIG was administered parenterally within the first 10 days of life to 34 infants <2500 gm with signs of congestive heart failure and patent ductus arteriosus. Ten of 34 (29.4%) developed DIG toxicity diagnosed on the basis of cardiac arrhythmias, ileus, abdominal distension and/or serum DIG levels >2.0 ng/dl (range 2.1-6.1). Sixteen of the 34 were 1500-2500 gm; 2/16 (12.5%) developed signs and symptoms of DIG toxicity and had elevated serum levels. Eighteen of the 34 infants were <1500 gm with 8/18 (44.4%) becoming DIG toxic. Two infants <1500 gm died; both had toxic serum levels at the time of death and 1 died of unexplained cardiac arrhythmias. All 10 DIG toxic infants had PR intervals >.12 sec (range .13 - .18) at the time of diagnosis without evidence of electrolyte imbalance, liver or renal compromise.We conclude that LBW infants, especially those <1500 gm, are exquisitely sensitive to DIG even at low maintenance dosage. Prolongation of PR interval was indicative of DIG toxicity in our patients. Continuous monitoring of the PR intervals and serial serum DIG levels are recommended for the avoidance of serious complications of DIG therapy in LBW infants.

PRACTICE AWARENESS OF CONTRAINDICATIONS TO PERTUSSIS VACCINE (V): A SURVEY OF 403 PEDIATRICIANS (P)

The debate over the liability for pertussis-related neurologic complications prompted the following survey. The survey was undertaken to evaluate the awareness of contraindications and examine recent physician attitudes towards the use of the V. A questionnaire (Q) was mailed to 924 P. In the Q the P were asked whether they would/or would not administer the V in each of 27 clinical situations. The situations included contraindications given by the Red Book (RB) of the Committee on Infectious Diseases (American Academy of Pediatrics) and other clinical situations. The Q was completed by 403 P (44%) of whom 192 were child neurologists. Results:All of the responders differed with the recommendations of the RB. Unexpectedly, the results show that some P would have given the V even when contraindicated by the RB, and a number of clinical situations (prematurity 14%, allergies 17%, cystic fibrosis 18%, family history of seizures 21%, cerebral palsy 26% and sibling with adverse reaction to V 51% ) were erroneously interpreted as contraindications. If P non-compliance with established guidelines is as prevalent as our survey suggests, lower immunization rates, increased incidence of pertussis, increased V related complications and increased number of vaccine related litigations will not be unexpected.

CLASSROOM PERFORMANCE, HEALTH, SOCIAL FACTORS OF VERY LOW BIRTH WEIGHT (VLBW) CHILDREN: FOLLOW-UP AT 5–8 YEARS

Increasing survival of VLBW infants causes concern for long term health and educational needs. This study was designed to locate VLBW children at school age, to compare educational services they required with peers and term siblings and to review computerized data of the hospital course. Parental, educational and medical information was obtained from questionnaires, interviews and clinic or field visits. Of 43 neonates weighing ≤1250g ([xmacr ;[plusmn;SEM =1076g±19.2) admitted for intensive care from 1974-1978 and surviving to school age, 7 were lost to follow-up and 3 have yet to attend school. Of the 33 VLBW children in school, 3(9.1%) were in classes for the major handicapped while 30(90.9%) were found comparable to their classmates by teachers or test scores; however, 14/30 (47%) required remedial instruction to perform at grade level. Major medical problems included seizures, spastic diplegia and visual or hearing loss. Of 13 VLBW children with siblings in school, 3 required more specialized staff than their siblings. The group without the need for specialized teaching staff had older maternal ages ([xmacr ;[plusmn;SEM=24.7yrs±1.28 vs 21.7±0.74,p<0.05, t-test) and tended to reside in higher socioeconomic households by Hollingshead Index (p<0.10,X2) which may have resulted in more stimulation at home. The VLBW children had a greater proportion (17/33, 51.5%) requiring specialized instruction than the general school population (24%, p<0.001,X2), although with this instruction most compared favorably with classmates.

A Neonate and Her Diabetic Mother

At the University of Kentucky Albert B. Chandler Medical Center, Integrative Clinicopathological Conferences are held regularly to explore various dimensions—economic, psychosocial, ethical, preventive, and medical—of health care. They are organized by Dr. Joseph Engelberg. Professor of Physiology and Biophysics. This conference was moderated by Dr. Peter P. Bosomworth. Chancellor of the Medical Center.

1286 IMPROVED PREDICTION OF FETAL LUNG MATURITY IN DIABETIC PREGNANCIES

Following planned termination of pregnancy, infants of diabetic mothers (IDM) have shown a continued vulnerability to the respiratory-distress syndrome (RDS) suggesting false-positive fetal lung maturity testing. Adequacy of the lecithin/sphingomyelin (L/S) ratio for predicting RDS was studied in 56 diabetic (DM) and 50 nondiabetic (ND) pregnancies. Amniotic-fluid samples (n=130) were assayed for 1- and 2-dimensional (dim) thinlayer chromatographic (TLC) L/S ratios, and phosphatidylglycerol (PG) and phosphatidylinositol (PI) assays. L/S ratios for all pregnancies by both TLC techniques revealed higher 1-dim values from 36-38 wk gestation (P<0.01). Per cent PI was increased for ND over DM before 34 wk (P<0.03), otherwise it did not delineate gestational age for either group. PG appeared in the surfactant complex beyond 34 wk (P<0.001), however, when L/S ratios were 2 to 2.9, it appeared in only 16.7% of DM pregnancies vs 50% of ND (P<0.02). PG was absent in 37% of all pregnancies > 38 wk with L/S ratios > 3. PG detection by class of DM was delayed for class A pregnancies beyond 36.5 wk (r=0.6551, P<0.007). Respiratory distress developed in 3 infants (2.9%): 2 ND had transient tachypnea (1.9%), 1 IDM had RDS (0.95%). We conclude: 1) 2-dim TLC improves phosphatide identification, 2) PG, if present, confirms fetal lung maturity in conjunction with positive L/S ratios, and 3) the L/S ratio remains the best available indicator of fetal lung maturation, irrespective of maternal diabetes.