Thyroid hormone levels in term and preterm neonates

Screening for thyroid hormone levels in the first week of life is extremely important to identify infants with CH. Worldwide neonatal screening programs have been successful in decreasing childhood mental retardation related to CH by early detection and treatment. To successfully screen for CH, nurses must understand how to draw blood that will yield valid results on the metabolic screening filter paper. It is also important for the nurse to understand that thyroid levels are normally decreased in preterm infants and that regular follow-up of those low thyroid levels is crucial because levels may return to normal and eventual treatment is necessary. Early follow-up testing and treatment are essential. A thyroid scan or ultrasonography is optional and decided on by evaluating the risk-benefit ratio.     

Transcutaneous bilirubin levels in healthy term and late preterm Indian neonates

Objective  

To provide normative data for transcutaneous bilirubin (TcB) measurements in healthy term and late-preterm Indian neonates during first 72 h of age using a multiwavelength reflectance transcutaneous bilimeter.     

Maximal airway pressures during crying in healthy preterm and term neonates

Respiratory muscle strength can be assessed by measurement of maximal inspiratory (PIMAX) and maximal expiratory pressure (P(EMAX)) during crying. There are, however, relatively few data on P(IMAX) and P(EMAX) in infancy, particularly from those born preterm. Our aim was to investigate which factors influenced P(IMAX) and P(EMAX) in preterm and term infants. Forty infants, median gestational age 37 weeks (range 26-43) and birthweight 2.579 kg (range 0.956-5.180) were studied at a postconceptional age (PCA) of 38 weeks (range 32-44). None had respiratory problems. A facemask was placed firmly over the infant's mouth and nose and the infant studied during spontaneous crying. A pneumotachograph fitted snugly into the facemask and from a sideport airway pressure changes were measured. During crying, the distal end of the pneumotachograph was occluded for five breaths and at least three separate occlusions were made. The highest P(EMAX) value sustained for at least 1 s and the highest peak inspiratory pressure P(IMAX) were recorded. The mean P(IMAX) and P(EMAX) were higher in the term compared to the preterm infants (70 cmH2O +/-S.D. 19 versus 58 cmH2O +/-S.D. 17 P(IMAX) and 53 cmH2O +/-S.D. 13 versus 44 cmH2O +/-S.D. 19 P(EMAX), P< 0.05). Both P(IMAX) and P(EMAX) related significantly with postconceptional age, gestational age and weight, but not postnatal age. Stepwise regression analysis demonstrated P(IMAX) related independently with PCA and P(EMAX) with weight. These results suggest respiratory muscle strength is influenced by maturation at birth.     

Serum IgG levels in full term preterm and SFD neonates

Cord blood IgG levels were estimated in fifty normal full term, preterm and small for date babies. The values were significantly lower (p<0·05) both in preterm and SFD babies when compared with normal full term (AGA) newborn. A direct correlation was found to exist between IgG concentration and gestation age in pretern as well as full term (ABA). Small for date babies showed significantly lower (p<0·05) IgG levels as compared to preterm (AGA) neonates suggesting the effect of inadequate placental function as a contributing factor in decreased serum IgG values in small for date babies.     

Ophthalmic artery blood flow velocity in healthy term and preterm neonates

Ophthalmic artery blood flow velocity (OA-BFV, cm/s), cerebral blood flow velocity (C-BFV, cm/s), and cardiac output (ml/min) were measured by pulsed Doppler sonography in 15 healthy term and 10 well preterm (26-35 wk) infants in the first week of life. OA-BFV did not increase with increasing gestational age (preterm: peak systolic BFV 29 +/- 5 cm/s, mean BFV 7.2 +/- 1.5 cm/s; term: peak systolic BFV 27 +/- 5 cm/s, mean BFV 6.6 +/- 1.3 cm/s), unlike C-BFV (preterm: peak systolic BFV 34 +/- 8 cm/s, mean BFV 9.4 +/- 2.3 cm/s; term: peak systolic BFV 43 +/- 9 cm/s, p less than 0.05; mean BFV 11 +/- 3.0 cm/s, p less than 0.05) and cardiac output (preterm 329 +/- 128 ml/min, term 732 +/- 112 ml/min; p less than 0.001). The ratio of OA-BFV/C-BFV was significantly higher in preterm than in term infants (p less than 0.01). In preterm infants, but not in term infants, there was a positive linear correlation of OA-BFV to C-BFV (r = 0.88). We conclude that it is possible to measure opthalmic artery blood flow velocity in neonates by pulsed Doppler sonography. Gestational age has different effects on OA-BFV and on C-BFV. Although it is a point of discussion if blood flow velocities are reflecting absolute blood flow, Doppler assessment of OA-BFV could be a tool for monitoring risk factors for retinopathy of prematurity.     

Measurement of right ventricular volume in healthy term and preterm neonates

BACKGROUND: Pulmonary hypertension is associated with worse perinatal outcomes in infants with respiratory disorders. In such infants right ventricular dysfunction may result in poor pulmonary blood flow. OBJECTIVE: To evaluate the practicability and repeatability of echocardiographic measurements of right ventricular volume in healthy term and preterm neonates, and to follow changes in right ventricular volume over the first 2 days of life. METHODS: Serial echocardiographic examinations were performed on day 0, 1, and 2 on healthy term and preterm neonates. Two methods of estimating right ventricular volume were assessed: the ellipsoid approximation and Simpson's stacked discs methods. Systolic and diastolic volumes on days 1 and 2 were compared with baseline values on day 0. Term and preterm volumes were compared at the same time points. RESULTS: Thirty five infants were recruited, 18 term and 17 preterm. Right ventricular volumes were significantly lower on day 1 and day 2 than baseline in both term and preterm infants. Median (interquartile range) end systolic and diastolic volumes for term infants on days 0, 1, and 2 were 1.04 (0.88-1.44), 0.82 (0.70-1.03), 0.92 (0.72-0.97) ml/kg and 2.21 (2.10-2.75), 2.05 (1.81-2.38), 1.91 (1.81-2.13) ml/kg respectively. In preterm infants the values were 1.09 (0.91-1.16), 0.72 (0.54-0.91), 0.61 (0.54-0.76) ml/kg and 2.09 (1.71-2.25), 1.47 (1.23-1.98), 1.43 (1.22-1.78) ml/kg respectively. CONCLUSION: Right ventricular volume decreases over the first 2 days of life in healthy term and preterm infants.     

Growth hormone release in response to growth hormone-releasing hormone in term and preterm neonates

The growth hormone response to a single intravenous dose of human growth hormone-releasing hormone (GHRH) was examined in 23 healthy neonates (12 term and 11 preterm) aged 2-4 days. There were no significant increases in growth hormone concentrations at any point in time studied following GHRH administration in either group of newborns. The mean basal growth hormone levels of term neonates were significantly higher than those of the premature newborns (39.6 +/- 5.3 vs. 23.2 +/- 3.3 ng/ml; p less than 0.01) and this difference in growth hormone remained significant 15 and 30 min after GHRH injection. Gestational age correlated positively with both basal and peak growth hormone concentrations in our patients. In conclusion, first, neonates studied in their first days of life have high basal levels of growth hormone and fail to further secrete any significant amount of growth hormone following a single dose of GHRH, and, second, premature newborns secrete significantly less growth hormone than do term neonates.     

Nitric oxide levels in preterm and term infants and in premature infants with bacteremia

OBJECTIVE: To determine the serum nitric oxide levels in healthy neonates and in infants with bacteremia. METHODS: We performed a prospective study in a tertiary neonatal intensive care unit. The serum nitric oxide levels were measured in all infants at birth (basal) and in the infected neonates also on the first 2 days of bacteremia. RESULTS: Thirty-three neonates (10 term, 23 preterm) were included. Eleven preterm infants (mean gestational age 27 weeks) had bacteremia. The main blood culture isolates included coagulase-negative staphylococci (n=4), Klebsiella pneumoniae (n=3), and Escherichia coli (n=3). The serum nitric oxide levels increased during infection in 10 infants (p <0.008). The mean nitric oxide level before infection was 44 microM and during infection 96 microM (p=0.008). In the healthy babies, the mean nitric oxide level was 26 microM in those with a gestational age <27 weeks, 44 microM in those born between 28 and 36 weeks of gestation, and 63 microM in term infants. CONCLUSIONS: Bacteremic preterm infants produce significantly higher amounts of nitric oxide. The basal nitric oxide levels at birth may be correlated with gestational age.     

Temperature measurement in term and preterm neonates

Body temperatures of 99 term and 44 preterm infants were measured at four sites: core (5 cm beyond the anus, with an electronic telethermometer), rectum (2 cm, with a mercury-in-glass thermometer), axilla, and between the skin and mattress. Temperatures measured at the four sites agreed closely in this group of largely normothermic infants. However, five of seven term infants with abnormal core temperature (greater than 1.5 SD below or above the mean) would have been judged to be normothermic by each of the three other measurements. The temperatures in preterm infants were lower and varied less with the site of measurement, indicating a smaller core-surface temperature gradient because of their relative lack of thermal insulation by body fat. Axillary temperature was as reliable as rectal temperature measured in the usual way with a mercury-in-glass thermometer. Measurement of the temperature between the skin and mattress was nearly as accurate as the other more frequently used methods. Ninety percent of temperatures were within 0.1 degree C of their final stabilization readings by 5 minutes for each type of thermometer and measurement site.     

Antenatal magnesium sulphate exposure is associated with prolonged parathyroid hormone suppression in preterm neonates

The effects of maternal magnesium sulphate treatment on neonatal mineral status and parathyroid hormone secretory response were studied in 8 exposed and 27 control preterm infants during the first 2 wk of life. Antenatal magnesium sulphate resulted in hypermagnesaemia during the first 3-7 d of life without affecting other serum mineral concentrations. Conclusion: Early hypermagnesaemia was associated with hypercalciuria during the first 3 d and parathyroid hormone suppression up to the age of 2 wk in the exposed infants.     

Urinary N-acetyl-beta-D-glucosaminidase excretion in term and preterm neonates

Urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion was measured in term and preterm neonates on days 1, 4, 7, 14 and 28 of life. Urinary NAG showed a peak level on day 4 or 7 in these infants. In addition, it tended to be higher with the degree of prematurity. In sick preterms who were depressed at birth and had respiratory failure, the NAG activity was further elevated during the first 2 weeks, suggesting the presence of renal tubular injury in this period. These observations thus suggest that urinary NAG may be a sensitive measure of renal maturation or damage in neonates.     

Echocardiographic measurements in normal preterm and term neonates

To the purpose of better defining normative data on intracardiac dimensions and systolic time intervals in very low birth weight infants, we collected M-mode echocardiograms from 210 healthy preterm and term neonates with birth weights between 780 and 5,350 g and gestational ages ranging from 26 to 43 weeks. Fifty-nine neonates were less than 24 h, 62 were 25-48 h, and 89 were 48-144 h of age. Diastolic and systolic left ventricular dimensions increased gradually with advancing birth weight (r = +0.84 and 0.78). Left atrial and aortic root dimensions tended to show a parabolic relationship with birth weight, increments were reduced at higher birth weights (r = +0.92 and 0.85). The shortening fraction of the left ventricle (mean +/- SD 33.8 +/- 4.9%) and the left atrial/aortic ratio (1.16 +/- 0.10) were constant throughout all weight subgroups. Pre-ejection periods and ejection times of both ventricles were reduced in preterm infants due to their higher heart rates, but left and right ventricular PEP/ET ratios in preterm and term infants were comparable. Septal thickness in diastole and in systole tended to increase slowly with advancing birth weight, but correlation coefficients were low. This information is currently used as data base for a computer program to interpret M-mode echocardiograms performed in our nursery.     

Pulmonary artery pressure in term and preterm neonates

Systolic pulmonary artery pressure (PAP) during the first 4 days after birth was determined in 41 healthy term and 46 preterm infants by measuring ductal Doppler flow velocity and systemic arterial pressure (SAP). Among preterm infants, 21 had respiratory distress syndrome (RDS) and 25 did not. Sequential indices within 96 h of age were presented respectively. At the ages of 2 and 12 h the ratio between pulmonary and systemic arterial pressure was significantly higher in term than in preterm infants without RDS ( p < 0.05). At the age of 24 h, PAP to SAP ratio was similar in all study groups. Between 48 and 72 h, PAP to SAP ratio was significantly higher in preterm infants with RDS than in infants without RDS ( p < 0.05). Our findings indicated that: (1) in healthy fullterm infants pulmonary artery pressure fell to subsystemic level during the first 12 h. indicating the critical time in circulatory transition; (2) prematurity did not affect ductal closure times significantly; and (3) RDS was associated with prolonged ductal patency and delayed postnatal circulatory adaptation characterized by pulmonary hypertension.     

Gentamicin dosage in preterm and term neonates.

Pre-dose and peak serum levels of gentamicin were measured in 82 neonates (25-42 weeks'' gestational age), and for comparison in 10 infants and 9 children. Dosage was 2-2.5 mg/kg twice daily for the neonates, and three times daily for infants and children. Neonates were subdivided according to gestational age and weight. Serum levels of gentamicin were very variable in all groups. Preterm neonates of low gestational age (25-30 weeks) showed a 66% incidence of pre-dose levels exceeding 1 microgram/ml, indicating possible accumulation. In the less premature neonates this incidence was still 20-29%. The level of 4 microgram/ml, the minimum concentration required to inhibit most of the bacteria sensitive to gentamicin, was reached in increasing numbers of neonates as their gestational age rose (from 30% in the 31- to 35-week gestational age group, to 60% at term); those small-for-gestational age had consistently lower levels. It is concluded that term neonates require dosage to be individualized and serum levels of the drug to be monitored.     

Skin bilirubin measurement during phototherapy in preterm and term newborn infants

Background

The few existing studies evaluating the reliability of transcutaneous bilirubin monitoring during phototherapy gave controversial results.

Aims

To evaluate the accuracy of transcutaneous bilirubin measurement in a large population of newborn infants, during phototherapy.

Study design and methods

Total serum bilirubin and transcutaneous bilirubin on patched and unpatched skin areas were simultaneously measured in newborn infants undergoing phototherapy. Transcutaneous measurements were performed with a multiwavelength transcutaneous bilirubinometer (Respironics BiliCheck™). The Passing-Bablok regression and the Bland-Altman plot were used to estimate the relationship between serum and transcutaneous bilirubin.

Results

We studied 364 newborn infants with a mean (SD) gestational age of 34.6 (3) weeks and a mean birth weight of 2371 (805) grams. Total serum bilirubin, patched transcutaneous bilirubin and unpatched transcutaneous bilirubin were similar before phototherapy. After 52 (33) hours of phototherapy, the difference between serum bilirubin and patched transcutaneous bilirubin was 0.2 (3.1) mg/dL (not significant) while the difference between serum bilirubin and unpatched transcutaneous bilirubin was 3.2 (3.0) mg/dL (p < 0.001). Statistical analysis showed a good agreement between serum bilirubin and patched transcutaneous bilirubin, while unpatched transcutaneous bilirubin underestimates serum levels. The difference between patched and unpatched values was significantly lower in preterm than in term infants (2.8 mg/dL vs. 3.6 mg/dL; p < 0.001).

Conclusion

BiliCheck can be safely used for the evaluation of bilirubin levels in newborn infants under phototherapy. Its reliability on patched skin of the forehead is high enough to consistently reduce blood draws and to ascertain when to discontinue phototherapy. Because of the individual variance, any clinical decision has to be taken on the basis of the transcutaneous bilirubin trend more than on a single value.