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

Spontaneously occurring hypoglycemia has been described in children with se vere acute congestive heart failure. Hypoglycemia may he the result of an i ncrease in glucose utilization in tissues, a decrease in glucose production , or a decrease in the dietary intake of nutrients. To determine whether hy poglycemia may also occur in congenital heart disease with volume overloadi ng, we investigated glucose metabolism during and after an 18-hour fast in nine lambs with an aortopulmonary left-to-right shunt and nine control lamb s. Plasma levels of hormones involved in the endocrine control of glucose m etabolism were determined. The glucose production rate (rate of appearance [R-a]) was studied using [U-C-13]glucose. Gluconeogenesis through the Cori cycle was estimated by measuring glucose C-13 recycling. The arterial gluco se concentration (3,409 +/- 104 v 4,338 +/- 172 mu mol/L, P < .001) and R-a of glucose (16.97 +/- 0.89 v 25.49 +/- 4.28 mu mol . 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 C-13 re cycling via the Cori cycle (6.9% +/- 2.8% v 7.1% +/- 2.5%) and gluconeogene sis from pyruvate and lactate (1.24 +/- 0.58 v 1.95 +/- 0.67 mu mol . 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 lo wer in shunt versus control lambs (15.73 +/- 1.07 v 23.54 +/- 4.27 mu mol . min(-1). kg(-1), P < .05). In conclusion, after an 18-hour fast, the arter ial glucose concentration is lower in lambs with aortopulmonary shunts. Thi s lower glucose concentration is associated with a decreased glucose produc tion rate. In shunt lambs, glycogenolysis is decreased, while there is no d ifference in gluconeogenesis or hormonal control. Copyright (C) 1999 by W.B . Saunders Company.