Lower arterial glucose concentrations in lambs with aortopulmonary shunts after an 18-hour fast

Spontaneously occurring hypoglycemia has been described in children with severe acute congestive heart failure. Hypoglycemia may be the result of an increase in glucose utilization in tissues, a decrease in glucose production, or a decrease in the dietary intake of nutrients. To determine whether hypoglycemia may also occur in congenital heart disease with volume overloading, we investigated glucose metabolism during and after an 18-hour fast in nine lambs with an aortopulmonary left-to-right shunt and nine control lambs. Plasma levels of hormones involved in the endocrine control of glucose metabolism were determined. The glucose production rate (rate of appearance [R a]) was studied using [U- 13C]glucose. Gluconeogenesis through the Cori cycle was estimated by measuring glucose 13C recycling. The arterial glucose concentration (3,409 ± 104 v 4,338 ± 172 μmol/L, P < .001) and R a of glucose (16.97 ± 0.89 v 25.49 ± 4.28 μmol · min −1 · kg −1, P < .05) were lower in shunt versus control lambs. There were no differences in hormone levels between control and shunt lambs. Fractional glucose 13C recycling via the Cori cycle (6.9% ± 2.8% v 7.1% ± 2.5%) and gluconeogenesis from pyruvate and lactate (1.24 ± 0.58 v 1.95 ± 0.67 μmol · min −1 · kg −1) were similar in both groups of lambs. The sum of glycogenolysis and gluconeogenesis from precursors other than pyruvate and lactate was lower in shunt versus control lambs (15.73 ± 1.07 v 23.54 ± 4.27 μmol · min −1 · kg −1, P < .05). In conclusion, after an 18-hour fast, the arterial glucose concentration is lower in lambs with aortopulmonary shunts. This lower glucose concentration is associated with a decreased glucose production rate. In shunt lambs, glycogenolysis is decreased, while there is no difference in gluconeogenesis or hormonal control.