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During pregnancy, changes in the IGF axis are associated with changes in maternal metabolism and nutrient repartitioning which are necessary to meet the demands of a growing conceptus. The aim of this study was to assess the IGF axis, maternal weight changes and food intake in female New Zealand White rabbits (n = 7) prior to breeding (day 0) and serially throughout pregnancy until term (day 30-31). The total weight of the pregnant does progressively increased from 4.03 +/- 0.06 kg (mean +/- S.E.M.) on day 0 to 4.47 +/- 0.07 kg on day 30 (P < 0.001). Maternal tissue mass (total weight minus estimated conceptus weight) increased until day 18, plateaued to day 22/23, and then significantly declined. On day 30, the maternal tissue mass was not significantly different from the non-pregnant value, such that the final increase in total weight was due to conceptus growth. Although the does were fed ad libitum, food intake did not change until day 29 when it decreased to approximately 50% of previous intake (P < 0.01). Maternal serum IGF-I was 499 +/- 32 ng/ml on day 0, reached a peak of 832 +/- 160 ng/ml on day 21 (P < 0.02), and then declined to 341 +/- 49 ng/ml on day 30. In contrast, serum IGF-II increased dramatically from a non-pregnant level of 85 +/- 14 ng/ml to 16,295 +/- 2488 ng/ml on day 23 (P < 0.001), and then rapidly declined (3335 +/- 954 ng/ml, day 30). Changes in serum IGF-binding proteins (IGFBPs) followed a pattern similar to IGF-II, as assessed by Western-ligand blotting. All IGFBPs, especially the 45-40 kDa IGFBP-3 doublet, increased dramatically between days 12 and 24 of pregnancy, and then declined towards term. In conclusion, we observed unique and dramatic changes in the maternal serum IGF axis that corresponded to periods of maternal weight gain and loss. The tissue source of IGFs and IGFBPs remains undetermined, although it is of note that the time when major changes in the IGF axis were first observed coincided with the time of functional change from yolk sac to placenta in the rabbit.

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We examined the relationship between acute reductions in renal perfusion pressure, as approximated by femoral arterial blood pressure, and plasma renin activity in the uninephrectomized fetal lamb. Renal perfusion pressure was reduced and maintained at a constant value by controlled partial occlusion of the aorta above the renal artery. After 15 min of reduced blood pressure, blood samples were taken for determination of plasma renin activity. This protocol was performed 22 times in 11 fetal lambs. Additionally, three of the fetuses were delivered by cesarean section and studied as newborns for the first week of life. In the fetus, there was a linear relationship between log plasma renin activity and femoral arterial blood pressure (P less than 0.01). After birth, the relationship still existed, although it was shifted to the right (P less than 0.0001). We conclude that there is a significant relationship between plasma renin activity and renal perfusion pressure in the fetal lamb, and as early as 1 day after birth, this relationship shifts to the right in the newborn lamb.

Very low birth weight (VLBW) infants less than 1,000 g often experience hyperkalemia and hyperglycemia during the initial hospital course. Hyperkalemia has been noted in 44% to 50% of infants less than 800 g birth weight or less than 28 to 29 weeks' gestation. Hyperglycemia occurs 18 times more frequently in infants less than 1,000 g than in those weighing more than 2,000 g. Insulin has been used for VLBW infants less than 1,000 g to manage hyperkalemia, control hyperglycemia, and optimize parenteral nutrition. A protocol for using exogenous insulin therapy for VLBW infants is described.

With the advent of pulse oximetry, there has been a general decrease in the use of transcutaneous (Tc) blood gas monitoring in intensive care environments. The available data, however, suggest that arterial carbon dioxide pressure (PCO2) levels are best estimated by Tc methods. In this study, we report our experience using routine Tc PCO2 monitoring in 32 consecutive infants less than 2 weeks of age with birthweights less than 1500 g. A total of 644 simultaneous pairs (Tc PCO2 versus arterial PCO2) were obtained. Pairs were categorized according to a 2 x 2 matrix design based on sensor temperature (40 degrees or 43 degrees C) versus site of arterial sampling (umbilical [UAC] or peripheral artery catheter [PAC]). Sampling via the UAC resulted in excellent correlation between sample pairs at both sensor temperatures with similar regressions between groups. Sampling via the PAC, however, yielded poor correlation between sample pairs and a significantly different regression from both UAC groups. Based on these findings, we advocate the use of a sensor temperature of 40 degrees C in very low birthweight infants for tracking Tc PCO2 values. In addition, we suggest that inaccuracies in PAC sampling may lead to erroneous PCO2 determinations. We conclude that routine monitoring of Tc PCO2 is accurate and serves a useful and continuing role in the neonatal intensive care environment.