Myocardial function and hemoglobin oxygen affinity during hyperglycemia in the fetal lamb

Abstract

To determine the effects of maternal hyperglycemia on fetal hemodynamic and cardiac function, a study was carried out on 9 chronically catheterized fetal sheep. In 6 fetuses, glucose was infused intravenously with an initial dose of 5 mg/kg per min. Data were compared with controls. This dose was gradually increased to 16 mg/kg per min by the 5th day. The initial blood glucose was 14.7±3.0 mg/dl and increased to 54.6±16.4 mg/dl by the last day of the infusion period (P < 0.001). The PO2 decreased from a baseline of 20.25±3.40 to 15.88±5.24 mmHg (P < 0.01). Similarly significant decreases were also observed for the blood O2 content and O2 hemoglobin saturation: 8.5±1.7 to 6.4±2.2 ml/dl and 62.3±13.6 to 46.1±17.6%, respectively, during hyperglycemia (P < 0.01). The duration of the preejection period (PEP) before the start of the experiment was 45±4 ms; a final value of 57±10 ms was obtained (P < 0.01). However, the electromechanical delay and ejection time (ET) showed no significant variation. The ratio of the PEP/ET increased from 0.31±0.04 to 0.38±0.07 (P < 0.01) during hyperglycemia. The reticulocytes increased from 1.4±1.8 to 3.1±2.9% (P < 0.05) and the 2,3-diphosphoglycerate decreased from 4.4±1.1 to 2.8±1.2 μmol/g hemoglobin (P < 0.005). This study demonstrated that fetal hyperglycemia depresses myocardial function in the fetal lamb. The changes in cardiac function could not be explained by the small drop in O2 saturation.