Effect of severe normocapnic hypoxia on renal function in growth-restricted newborn piglets

Abstract

To examine the effects of intrauterine growth restriction and acute severe oxygen deprivation on renal blood flow (RBF), renovascular resistance (RVR), and renal excretory functions in newborns, studies were conducted on 1-day-old anesthetized piglets divided into groups of normal weight (NW, n = 14) and intrauterine growth-restricted (IUGR, n = 14) animals. Physiological parameters, RBF, RVR, and urinary flow, were similar in NW and IUGR piglets, but glomerular filtration rate (GFR) and filtration fraction were significantly less in IUGR animals (P < 0.05). An induced 1-h severe hypoxia (arterial PO(2) = 19 +/- 4 mmHg) resulted in, for both groups, a pronounced metabolic acidosis, strongly reduced RBF, and increased fractional sodium excretion (FSE; P < 0.05) with a less-pronounced increase of RVR and arterial catecolamines in IUGR piglets. Of significance was a smaller decrease in RBF for IUGR piglets (P < 0.05). Early recovery showed a transient period of diuresis with increased osmotic clearance and elevated FSE in both groups (P < 0.05). However, GFR and renal O(2) delivery remained reduced in NW piglets (P < 0.05). We conclude that, in newborn IUGR piglets, RBF is maintained, although GFR is compromised. Severe hypoxemia induces similar alterations of renal excretion in newborn piglets. However, the less-pronounced RBF reduction during hypoxemia indicates an improved adaptation of newborn IUGR piglets on periods of severely disturbed oxygenation. Furthermore, newborn piglets reestablish the ability for urine concentration and adequate sodium reabsorption early after reoxygenation so that a sustained acute renal failure was prevented.

Intrauterine Growth Restriction Ameliorates the Effects of Gradual Hemorrhagic Hypotension on Regional Cerebral Blood Flow and Brain Oxygen Uptake in Newborn Piglets

“…In a previous study with extensive surgical interventions, including opening the abdominal cavity, craniotomy, and ureter cannulation after retroperitoneal preparation along with 5 h of experimental performance, sham-operated newborn piglets showed no significant differences in ABP with only a slight increase in heart rate (by 20%). This corresponded to a comparatively moderate increase in circulating catecholamines (epinephrine by 73%, norepinephrine by 66%) (26). This elevation in circulating catecholamines was markedly blunted compared with a rather mild hypoxic exposure.…”

“…Furthermore, an improved capacity of newborn IUGR piglets to withstand severely disturbed renal oxygenation has been reported (26). Until now, the effects of IUGR on the cerebral autoregulatory response and cerebral oxygen uptake during gradual reduction of the cerebral perfusion pressure have not been determined.…”

Placental Restriction Increases the Expression of Prostaglandin Endoperoxide G/H Synthase-2 and EP2 mRNA in the Fetal Sheep Kidney during Late Gestation

“…Millard et al (27) reported that administration of indomethacin to fetal sheep caused a significantly greater decrease in renal blood flow when fetal hypoxia was induced. Interestingly, Bauer et al (28) demonstrated that in growth-restricted newborn piglets, the decrease in renal blood flow in response to severe hypoxia was smaller when compared with normally grown newborns, suggesting that adaptations in the growth-restricted fetal kidney improve its capacity to maintain renal blood flow during hypoxia. Based on data from the present study, it would be pertinent to determine the effects of blockade of the EP 2 /EP 4 receptor subtypes on renal blood flow and renin mRNA expression in the growthrestricted fetus.…”

Intrauterine growth restriction improves cerebral O2 utilization during hypercapnic hypoxia in newborn piglets

“…In a previous study with extensive surgical preparations, including opening the abdominal cavity, craniotomy, ureter cannulization after retroperitoneal preparation and up to 5 h experimental performance, sham‐operated newborn piglets showed no significant differences in arterial blood pressure and only a slight increase in heart rate (by 20%). This corresponded to a comparatively moderate increase in circulating catecholamines (adrenaline (epinephrine) by 73%, noradrenaline (norepinephrine) by 66%) (Bauer et al 2000). This elevation in circulating catecholamines was markedly blunted compared with a rather mild hypoxic exposure.…”