Changes in fetal lamb arterial blood gas and acid-base status with advancing gestation

Abstract

To determine whether there are changes in blood gas and acid-base status with advancing gestation in the fetal lamb, similar to that reported in the human fetus, blood gas, acid-base, and blood metabolite values were measured in 447 control, arterial blood samples from 108 chronically instrumented fetal lambs between 103 and 146 days gestation. With advancing gestation, Po(2), pH, O(2) saturation, and O(2) content fell significantly, while Pco(2) and hemoglobin concentration increased. Blood glucose and lactate concentrations were unchanged, although the lactate level increased with decreasing Po(2), particularly when below ~13 mmHg. Multiple linear regression indicated that increasing fetal number was associated with decreased Po(2) and glucose level and increased pH, HCO(3)(-), base excess, and lactate concentration. Hemoglobin concentration was higher in female than male lambs. Overall, there was a linear relationship between glucose concentration and birth weight. It is concluded that in fetal lambs as in the human fetus, there are changes in blood gas and acid-base status with advancing gestation. This may be due to the decrease in fetal weight-normalized uterine and umbilical blood flows than occurs in these and other species as gestation proceeds. In addition, the reduced birth weight in twin and triplet lambs may be due to hypoglycemia rather than hypoxemia.

Lactate in cord blood and its relation to fetal gluconeogenesis in at term deliveries

“…Fetal anaerobic metabolism with the development of metabolic acidosis is recognized as having a low pH with a high base excess (BE) at birth [2]. An alternative method to estimate the fetal 'oxygen debt' is lactate (2-hydroxypropanoic acid) concentration, an end product in glucose anaerobic metabolism [3][4][5]. Experimental animal data have suggested that lactate concentration is better than pH in predicting hypoxic process and neonatal morbidity [6].…”

Pharmacokinetics of tulathromycin in fetal sheep and pregnant ewes

“…Mean estimated pharmacokinetic parameters (Table ) in ewes and fetuses, and mean plasma concentrations in ewes, fetuses, and amniotic fluid (Figure ) are presented. Fetal blood gasses were analyzed at each sampling point (Table ) to confirm fetal viability, and all values were within expected ranges for gestational age (Rurak & Bessette, ).…”

“…The tubing was sutured to the inside of a hollow plastic golf ball with holes (Whiffle design, Wilson ™ ) to prevent collapse of membranes over the tubing and to secure it in the amniotic cavity amniotic fluid (Figure 2) are presented. Fetal blood gasses were analyzed at each sampling point (Table 2) to confirm fetal viability, and all values were within expected ranges for gestational age (Rurak & Bessette, 2013).…”

The fetuses‐at‐risk approach: survival analysis from a fetal perspective

“…Substantial animal and human biomedical research supports the fetuses‐at‐risk approach . Studies on sheep, horses, cows and humans all show that uterine and umbilical blood flow to the fetus increases as pregnancy advances.…”