Barbara Haydon

Precision of office-based blood glucose meters in screening for gestational diabetes☆

OBJECTIVE Is the precision of currently available glucose meters adequate for gestational diabetes screening? STUDY DESIGN We performed a prospective cohort study of 62 gravid women and compared the precision of three glucose meters to laboratory standard technology. RESULTS The HemoCue coefficient of variation was sufficiently low in venous whole blood and plasma and capillary whole blood and plasma (3.0%, 1.8%, 2.8%, and 2.3%, respectively) to allow use in gestational diabetes screening. The OneTouch II coefficient of variation was sufficiently low in capillary whole blood (2.7%) to allow use in gestational diabetes screening but was too high in venous whole blood and plasma and in capillary plasma (3.6%, 7.8%, and 5.7%). The ExacTech coefficient of variation was too high in venous or capillary whole blood (5.4% and 8.1%) for use in gestational diabetes screening and does not analyze plasma samples. CONCLUSION The HemoCue meter in venous and capillary whole blood and plasma and the OneTouch II meter in capillary whole blood have coefficients of variation low enough for gestational diabetes screening.

Positional effects on maternal cardiac output during labor with epidural analgesia.

OBJECTIVE Our purpose was to test the hypothesis that the supine versus the lateral position is associated with a greater decrement in cardiac output after epidural analgesia in labor. STUDY DESIGN Twenty-one normal term subjects were randomized to the left lateral or supine position in early labor. Cardiac output measured by the acetylene rebreathing method, stroke volume, heart rate, mean arterial pressure, and systemic vascular resistance were obtained at 5-minute intervals, beginning before a 500 ml intravenous fluid bolus (baseline) and ending 45 minutes after epidural injection. RESULTS Mean baseline supine versus lateral group differences were significant for 21% lower cardiac output, 21% lower stroke volume, 19% higher mean arterial pressure, 50% higher systemic vascular resistance, and equivalent heart rate. In the supine group fluid bolus resulted in significantly increased cardiac output and stroke volume, decreased mean arterial pressure and systemic vascular resistance, and unchanged heart rate. In the supine group cardiac output and stroke volume decreased significantly after epidural injection. The lateral position group exhibited no hemodynamic alterations after fluid bolus or epidural. CONCLUSIONS In contrast to the lateral position, the supine position is associated with a significant postepidural decrement in cardiac output, not identified by a change in heart rate. This likely reflects an inability to maintain stable preload volume in the supine position.

Glucose and lactate kinetics during a short exercise bout in pregnancy

Pregnancy is considered diabetogenic. Although exercise has been advocated to assist in metabolic control of the nonpregnant diabetic individual, there is a paucity of data about the metabolic effects of exercise during pregnancy. To examine whether moderate exertion may be beneficial in the maintenance of maternal carbohydrate homeostasis, glucose and lactate kinetics were measured in the third trimester in five pregnant nondiabetic women (gestational age, 34.2 +/- 0.1 weeks [mean +/- SE]) by infusion of 45 microg x kg(-1) x min(-1) [6,6-2H2]glucose and 70 microg x kg(-1) x min(-1) [U-13C]lactate tracers. Subjects were observed at rest for determination of baseline steady-state kinetics over a 30-minute period, and then they exercised for 30 minutes at 60% maximum oxygen consumption (VO2max) and were evaluated for 30 minutes postexercise. Glucose and lactate kinetics and lactate oxidation were measured throughout the exercise protocol. This study was repeated postpartum in all individuals at least 6 weeks after delivery. Compared with the steady-state preinfusion period, plasma glucose concentration was not elevated during exercise in either group, nor was plasma lactate concentration significantly different in either group. Glucose kinetics did not change during exercise, but lactate kinetics increased in both groups. V02 and percent of lactate C contribution to CO2, an indication of lactate oxidation, increased proportionally in both groups during exercise. Metabolic perturbations, as measured by glucose and lactate kinetics, do not appear to be different during the third trimester of pregnancy during a relatively short bout of exercise compared with the nonpregnant state.

Fetal Heart Rate Response to Maternal Exertion

Doppler monitoring of fetal heart rates during maternal exertion has suggested that fetal bradycardia occurs frequently during vigorous exercise, causing concern for fetal safety. Doppler determination of fetal heart rate during vigorous maternal effort is difficult. To avoid motion artifact, we observed fetal heart rate using two-dimensional ultrasound and determined the incidence of fetal bradycardia in 45 pregnant women (age, 29.0 +/- 3.7 years [mean +/- SD]; gestational age, 25.2 +/- 3.0 weeks) during 85 submaximal and 79 maximal cycle ergometer tests. Average fetal heart rate did not change during exercise. A single episode of fetal bradycardia (heart rate less than 110 beats per minute for greater than or equal to 10 s) occurred during submaximal exertion during a maternal vasovagal episode. Sixteen episodes of fetal bradycardia were noted within three minutes after cessation of exercise, 15 of which followed maximal maternal effort. We conclude that brief submaximal maternal exercise up to approximately 70% of maximal aerobic power (maternal heart rate less than or equal to 148 beats per minute) does not affect fetal heart rate. In contrast to submaximal maternal exertion, maximal exertion is commonly followed by fetal bradycardia. This may indicate inadequate fetal gas exchange.