The metabolic effects of a hypertonic fructose infusion on the mother and fetus during labor

Carbohydrate solution intake during labour just before the start of the second stage: a double-blind study on metabolic effects and clinical outcome

OBJECTIVE

To study the effects of oral carbohydrate ingestion on clinical outcome and on maternal and fetal metabolism.

DESIGN

Prospective, double-blind, randomised study.

SETTING

Leyenburg Hospital, The Hague, The Netherlands.

POPULATION

Two hundred and two nulliparous women.

METHODS

In labour, at 8 to 10 cm of cervical dilatation, the women were asked to drink a solution containing either 25 g carbohydrates or placebo. In a subgroup of 28 women, metabolic parameters were measured.

MAIN OUTCOME MEASURES

Number of instrumental deliveries, fetal and maternal glucose, free fatty acids, lactate, pH, Pco2, base excess/deficit and beta-hydroxybutyrate.

RESULTS

Drinking a carbohydrate-enriched solution just before starting the second stage of labour did not reduce instrumental delivery rate (RR 1.1, 95% CI 0.9-1.3). Caesarean section rate was lower in the carbohydrate group, but the difference did not reach statistical significance (1% vs 7%, RR 0.2, 95% CI 0.02-1.2). In the carbohydrate group, maternal free fatty acids decreased and the lactate increased. In the umbilical cord there was a positive venous-arterial lactate difference in the carbohydrate group and a negative one in the placebo group, but the differences in pH and base deficit were comparable.

CONCLUSION

Intake of carbohydrates just before the second stage does not reduce instrumental delivery rate. The venous-arterial difference in the umbilical cord suggested lactate transport to the fetal circulation but did not result in fetal acidaemia.

The effects of oral carbohydrate administration on fetal acid base balance

AIMS

Little evidence-based data are available on the effects of eating and drinking during labor. Intravenous glucose administration has been related to fetal metabolic acidosis. The question is, whether oral intake of carbohydrates effects the fetal acid-base balance.

METHODS

In a double blind, prospective placebo controlled study 100 nulliparous women were randomized at 8-10 cm of cervical dilatation. All women were asked to drink 200 cc of either a carbohydrate solution (containing 25 grams carbohydrates) or placebo. In all women, both arterial and venous umbilical cord pH, pCO2, pO2, HCO3- and base excess/deficit were assessed. In a subgroup of women, whose deliveries were complicated by mild signs of fetal distress, clinical outcome and acid-base status was described separately.

RESULTS

Fetal arterial umbilical cord pH were identical: 7.20 +/- 0.07 in the placebo group and 7.20 +/- 0.08 in the carbohydrate group and the base excess -6.6 +/- 2.8 versus 6.6 +/- 3.7. In the women with mild signs of fetal distress, no differences were observed as well.

CONCLUSIONS

Oral carbohydrate intake during labor seems to be safe regarding the fetal acid-base balance. Further study on the maternal and fetal metabolic parameters is essential to give a more complete picture.

Fetal and maternal energy metabolism during labor in relation to the available caloric substrate

AIM

To discuss maternal and fetal metabolic events during labor and the possible role of glucose administration.

RESULTS

The oxidative pathway covers the largest part of the energy demand of labor, although in the second stage or, in polysystolic labor, the non-oxidative pathway becomes important as well. Glucose is the main maternal energy source, but the rise in ketobodies, even during normal labor, suggests a relative shortage. In the first stage of labor, a combination of a respiratory alkalosis, and to a lesser extent, a metabolic acidosis, result in a rise in the maternal pH. In the second stage of labor, the maternal pH decreases due to an increasing metabolic acidosis. Glucose is also the main fetal energetic fuel. In fetal hypoxia, lactate is produced, which in most cases is transferred to the maternal circulation. High maternal lactate concentrations, however, may interfere with this process. Furthermore, fetal hyperglycemia may lead to an increased fetal lactate production.

CONCLUSIONS

Maternal hyperglycemia, may lead to an increase in maternal and fetal lactate production resulting in metabolic acidosis. Unlike high dosage intravenous glucose administration, it is not likely that oral intake of carbohydrates leads to maternal and fetal hyperglycemia and subsequently to metabolic acidosis, but studies are rare.

A comparison of the effects of four intravenous solutions for the treatment of ketonuria during labour

Forty women in whom ketonuria was detected during the first stage of labour were allocated randomly to intravenous treatment with one litre of either normal saline, Hartmann's solution, 5% dextrose or 10% dextrose. The solutions were administered over 1 h and blood was taken immediately beforehand and thereafter at 30-min intervals for 90 min to assess their effect on intermediary metabolism, plasma osmolality and acid-base status. Although both the 5 and 10% dextrose infusions caused a rapid decline in whole blood D-3-hydroxybutyrate concentrations, they also produced pathological degrees of maternal hyperglycaemia and hyperinsulinaemia and a marked elevation in the mean blood lactate and pyruvate concentrations. Administration of 10% dextrose was also associated with a significant increase in serum osmolality. Hartmann's solution produced significantly higher mean whole blood lactate and pyruvate concentrations than did normal saline. There was a significant increase in the venous base deficit in the group infused with 10% dextrose, indicating that the buffering capacity of the blood had been exceeded. It is concluded that rapid infusions of dextrose or Hartmann's solution should not be administered during labour. Normal saline should be used for rehydration and if dextrose therapy is deemed necessary the dose administered should not exceed physiological requirements.

Metabolic effects of constant hypertonic glucose infusion in well-oxygenated fetuses

In order to investigate the metabolic effects of a constant hypertonic glucose infusion in well-oxygenated fetuses, ten experiments were carried out in nine long-term experiments in fetal lambs. It appeared that a constant hypertonic glucose infusion did not significantly affect the fetal blood gases, pH, and plasma lactate levels when fetal glucose was kept below 150 mg. per 100 ml. It was also demonstrated that glucose infusions significantly increased the fetal lactate levels and decreased the blood pH when fetal plasma glucose was over 150 mg. per 100 ml. However, there was no decrease in fetal PO2 and pco2 until fetal glucose reached values over 300 mg. per 100 ml. These studies suggest that constant hypertonic glucose infusion does not improve fetal blood gases or pH and that fetal hyperglycemia over 300 mg. per 100 ml. produces severe metabolic acidosis.

Fetal carbohydrate metabolism: its clinical importance

A basic understanding of fetal nutrition and metabolism is essential in the clinical management of the obstetric patient. The fetus depends upon a constant infusion of glucose for energy production and growth. Maternal glucose is the prime source of this nutrient. Alterations in maternal carbohydrate homeostasis will lead to changes in fetal metabolism. In diabetes mellitus, hyperglycemia may produce hyperinsulinemia and macrosomia. The growth-retarded fetus may have a decreased supply of maternal glucose and reduced amounts of hepatic glycogen and adipose tissue. The fetus must depend upon these stores for survival during periods of intrauterine hypoxia. In the newborn period, hypothermia and hypoxia may rapidly deplete energy reserves. With this information, the clinician may more knowledgeably manage dietary demands in the antepartum patient, fetal distress during labor, and the immediate newborn period.

The effect of fructose infusions in the course of labor upon parturient and fetus

Fructose infusions were administered to parturients with healthy term fetuses at a speed of 1 g/min for 106 on the average. The results confirm that fructose has the expected properties. The blood glucose and FFA levels show that a substantial part of the infused fructose is indeed stored and that only a small portion is used to cover immediate energy needs. This positive result is predominant by a considerable degree of acidosis arising in the parturient in spite of the fact that fructose was infused at a slower rate than in the majority of papers published so far. Since the fructose infusions were intended for premature fetuses, which already have an increased tendency toward acidosis, the results confirm the unsuitability of such a treatment.

Lactic acidosis complicating treatment of ketosis of labour

Hypertonic glucose, fructose, and sorbitol solutions were given intravenously to women in the first stage of labour who had ketonuria and ketonaemia as evidenced by a raised blood acetoacetate and 3-hydrosybutyrate. There was no difference in the antiketogenic action of these, which was rapid and effective, but when compared with a control group who were given normal saline they had a high incidence of hyperlactataemia, and nine out of 28 patients developed lactic acidosis after the infusions. The "lactatogenic" effect was shared by all three substrates, and when they are used in the treatment of ketosis of labour, and the mother develops lactic acidosis, they might exacerbate pre-existing lactic acidosis and precipitate fetal distress.