Renal function of normal full-term infants in the first hours of extrauterine life

A Randomized Controlled Trial of Intact Cord Milking versus Immediate Cord Clamping in Term Infants Born by Elective Cesarean Section

OBJECTIVE

We evaluated whether intact umbilical cord milking (UCM) is more effective than immediate cord clamping (ICC) in enhancing placental transfusion after elective cesarean delivery.

STUDY DESIGN

In a randomized trial, volume of placental transfusion was assessed by Δ hematocrit (Hct) between neonatal cord blood and capillary heel blood at 48 hours of age, corrected for the change in body weight.

RESULTS

There were no significant differences in cord blood mean Hct values at birth (UCM, 44.5 ± 4.8 vs. ICC, 44.9 ± 4.2%, p = 0.74). Conversely, at 48 hours of age, the UCM group had significantly higher capillary heel Hct values (UCM, 53.7 ± 5.9 vs. ICC, 49.8 ± 4.6%, p < 0.001), supporting a higher placental transfusion volume (Δ Hct, UCM 9.2 ± 5.2 vs. ICC 4.8 ± 4.7, p < 0.001), despite comparable neonatal body weight decrease (UCM, -7.3 vs. ICC, -6.8%, p = 0.77).

CONCLUSION

Higher Δ Hct between cord blood at birth and capillary heel blood at 48 hours of age, corrected for the change in body weight, suggests that intact UCM is an efficacious and safe procedure to enhance placental transfusion among neonates born via elective cesarean delivery.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT03668782.

Assessment of kidney function in preterm infants: lifelong implications

This educational review will highlight the historical and contemporary references that establish a basic understanding of measurements of kidney function in the neonate and its relevance for the life of an individual. Importantly, the differential renal function of preterm infants relative to term infants has become paramount with the increased viability of preterm infants and the realization that kidney function is associated with gestational age. Moreover, neonatal kidney function is primarily associated with absolute renal mass and hemodynamic stability. Neonatal kidney function and its early developmental progression predict lifelong cardiovascular and renal disease risks. Validation of estimation equations of kidney function in this population has provided important reference data for other investigations and a clinical basis for prospective and longitudinal follow-up. Future research should be directed towards a better understanding of surrogate markers of kidney function from infancy through adulthood. Pediatric nephrologists should be aware of the developmental aspects of kidney function including the importance of the congenital nephron endowment and the preservation of kidney function throughout a lifetime. • Nephrogenesis occurs in utero in concert with other organ systems by branching morphogenesis, including the lungs, pancreas, and vascular tree, with over 60 % of nephrons being formed during the last trimester. • Infants born preterm before 36 weeks' gestation are in active nephrogenesis and are at increased risk of having a decreased nephron endowment from prenatal and postnatal genetic and epigenetic hazards that will impact the patient for a lifetime. • Post-natal adaptation of kidney function is directly proportional to the number of perfused nephrons, estimated by total kidney volume (TKV), mean arterial pressure (MAP), and gestational age. • Accurate measurement of glomerular filtration rate (GFR) in infants is problematic due to the unavailability of the gold standard inulin. The traditional use of creatinine to estimate GFR is unreliable in preterm infants due to its tubular reabsorption by immature kidneys and its dependence on muscle mass as an endogenous marker. Alternative endogenous markers to estimate GFR are cystatin C and beta trace protein (BTP). • Long-term follow-up of renal function in those born preterm should be life long and should include assessment of GFR, total kidney volume (TKV) relative to body surface area (BSA), and cardiovascular risks including hypertension and vascular stiffness.

Pharmacokinetics of antibiotics in neonates

The pharmacodynamics in neonates are different from those in adults and children because the absorption, distribution, metabolism and excretion of drugs in neonates are always changing for the following reasons. In neonates, the proportion of extracellular fluid is large; the amount of plasma protein is small; renal function is immature; and the hepatic enzyme system is immature. In addition, individual birthweights, gestational ages in weeks, cardiopulmonary functions and renal excretory functions vary. All of these factors should be considered when selecting the dose and administration method of a drug. In concrete terms the distribution volume is large, which causes a low maximum concentration. In addition neonate renal excretory function is low and the hepatic enzyme system is immature, thus the half-life of drugs is prolonged. Therefore, the same dose per unit time as that for children (including infants) needs to be administered to neonates at dosing intervals that may be prolonged according to renal function.

A combined ultrasonic and biochemical study of fetal renal function in the term fetus

The fetal glomerular filtration rate of plasma (GFR) and the percentage of fetal tubular reabsorption of water were measured by means of combined ultrasonic and biochemical methods in 20 normal and 10 complicated pregnancies. The duration of pregnancy varied from 35 to 42 wk. In normal pregnancy GFR of plasma varied from 2.0 to 7.1 ml/min (mean = 4.1) and tubular reabsorption of water ranged from 84.1 to 93.0% (mean = 89.8). There was no relationship with gestational age. In the group of complicated pregnancies - apart from one anencephalic case - no apparent difference in GFR and percentage tubular reabsorption between the group of normal (greater than or equal to 10th percentile) and reduced fetal birth weight (less than 10th percentile) was observed.

Renal response to acid loading in the developing lamb fetus, intact in utero

Response of the fetal kidney to metabolic acidosis was studied in five fetal lambs, 115-125 days gestation, in order to evaluate the renal contribution to elimination of hydrogen ion during intra-uterine development. Experiments were conducted on healthy unanesthetized fetuses, intact in utero, with catheters implanted at hysterotomy into a fetal femoral artery and vein and into the bladder via the urachus, four or more days prior to the study. A metabolic acidosis was induced by infusion of isotonic lactic acid, 15 m mole/kg, intravenously over a period of 90 minutes. Serial arterial samples were taken and urine collected in fractions before, during and for three hours following the infusion, for measurements of pH, bicarbonate, lactate and electrolytes as well as urine output. During the infusion, urine pH fell from 6.65 to 6.25 and was 6.34 three hours later (Figs. 1 to 4, Tabs. III to IV). Lactic acid infusion caused a prompt increase in urine output from a mean rate of 0.12 to a maximum of 0.28 ml/kg/min at the end of the infusion, returning to control rates three hours later. Lactate excretion increased from 0.05 to a maximum of 4.6 mumole/kg/min at the end of infusion; titratable acid increased from 0.22 to a maximum of 4 muEq/kg/min; the rates of excretion of lactate and titratable acid were still higher than control at the end of three hours. Ammonia excretion increased from 0.21 to a maximum of 0.56 muEq/kg/min three hours after the end of infusion. The acid infusion caused a small but significant fall in excretion of bicarbonate. During the 90 minutes of infusion and over the following three hours, about 800 mumole lactate was excreted while net acid excretion over the same period was no more than half that amount. The diuresis was also accompanied by a net loss of sodium and chloride, the excretion of these ions increasing more than threefold following acid infusion; excretion of potassium decreased to one-third its rate prior to the infusion. During the 90 minutes of infusion, blood pH fell from 7.36 to 7.13, base deficit rose from 3.8 to 16.4 mEq/L and lactate rose from 2.2 to 14.8 mM/L; there was also a small but significant rise in both blood PCO2 and PO2 (Figs. 1 to 2, Tabs. I to II). During the following three hours of recovery, pH rose gradually to 7.29, base deficit and lactate fell to 7.4 mEq/L and 8.7 mM/L respectively. Since renal excretion of net acid and lactate was small, the decrease in blood base deficit and lactate levels during the recovery must therefore be mainly due to equilibration in various fetal compartments as well as placental transfer. These experiments indicate that, in the lamb fetus, intact in utero, the kidney although limited by immaturity of several mechanisms, is capable of responding to an acid load and thus can make a small contribution to fetal homeostasis. The increase in excretion of net acid is accompanied by loss of sodium and chloride in the urine.