Biological variation of cardiovascular risk factors in patients with diabetes

Biological variation refers to the natural fluctuations found when repeated measurements are made in a biological system. Generally, biological variation remains within narrow boundaries in health, but may differ in pathological states, with implications for the diagnosis and monitoring of disease processes. In disease, biological variation may alter such that any subsequent measurement may need to have a greater difference compared with a healthy control to be biologically relevant. Treatments such as insulin or anti‐hypertensive therapy have been shown to reduce biological variability closer to normal levels and theoretically this may help prevent complication development or progression in conditions such as diabetes. This article reviews how biological variation can influence our identification and assessment of vascular risk factors in a person with diabetes. The role of biological variation in the diagnosis of diabetes (glucose and HbA_1c) is then examined. Finally, the influence that common treatments in diabetes have in modifying biological variation is described.     

Birth plans—Impact on mode of delivery,obstetrical interventions,and birth experience satisfaction: A prospective cohort study

Objective

To examine whether the presence of a birth plan was associated with mode of delivery, obstetrical interventions, and patient satisfaction.

Methods

This was a prospective cohort study of singleton pregnancies greater than 34 weeks’ gestation powered to evaluate a difference in mode of delivery. Maternal characteristics, antenatal factors, neonatal characteristics, and patient satisfaction measures were compared between groups. Differences between groups were analyzed using chi‐squared for categorical variables, Fisher exact test for dichotomous variables, and Wilcoxon rank sum test for continuous or ordinal variables.

Results

Three hundred women were recruited: 143 (48%) had a birth plan. There was no significant difference in the risk of cesarean delivery for women with a birth plan compared with those without a birth plan (21% vs 16%, adjusted odds ratio [adjOR] 1.11 [95% confidence interval (CI) 0.61‐2.04]). Women with a birth plan were 28% less likely to receive oxytocin (P < .01), 29% less likely to undergo artificial rupture of membranes (P < .01), and 31% less likely to have an epidural (P < .01). There was no difference in the length of labor (P = .12). Women with a birth plan were less satisfied (P < .01) and felt less in control (P < .01) of their birth experience than those without a birth plan.

Conclusion

Women with and without a birth plan had similar odds of cesarean delivery. Though they had fewer obstetrical interventions, they were less satisfied with their birth experience, compared with women without birth plans. Further research is needed to understand how to improve childbirth‐related patient satisfaction.     

Effect of anaesthesia on the negative feedback action of gonadal steroids on gonadotrophin secretion in the ovariectomized guinea-pig

The effects of urethane or sodium pentobarbitone anaesthesia on the feedback effects of oestradiol or progesterone on gonadotrophin secretion in the ovariectomized guinea-pig have been investigated. In the control experiments in which no steroids or vehicles were given the concentration of LH and FSH in samples of peripheral blood collected at intervals of 15 min varied in a random episodic manner. The mean level of LH was significantly greater in sodium pentobarbitone- and urethane-anaesthetized animals when compared with conscious animals, and in the conscious animals there was a progressive fall in mean LH level during the course of serial sampling. This effect was not observed in anaesthetized animals. Oestradiol benzoate (2 microgram s.c.) inhibited LH secretion in conscious animals and in those anaesthetized with sodium pentobarbitone, but not in urethane-anaesthetized guinea-pigs. Progesterone (200 microgram s.c.) progressively depressed plasma LH levels in conscious and urethane-anaesthetized animals, but not in guinea-pigs anaesthetized with sodium pentobarbitone. The effect of anaesthesia was the converse of that observed with oestradiol treatment. Significant changes in FSH secretion were not observed under any experimental conditions. These findings point to the existence of a mechanism in spayed guinea-pigs that restrains LH secretion, the action of which is reduced by anaesthesia and modified by oestradiol and progesterone.     

Effect of exposure to long days on the secretion of oestradiol, oestrone, progesterone, testosterone, androstenedione, cortisol and follicle-stimulating hormone in intact and spayed ferrets

The changes in concentration of plasma oestradiol, oestrone, progesterone, androstenedione, testosterone, cortisol and FSH were followed in intact female ferrets brought into oestrus by extension of the photoperiod from 8 to 16 h daily. An additional group of spayed females was similarly exposed to the extended photoperiod. There was no change in the blood oestrone, androstenedione and testosterone levels in the spayed females; the concentration of oestradiol, progesterone and FSH fell, while that of cortisol rose after 6 weeks. The intact females showed no change in plasma oestrone and cortisol concentrations, a rise in plasma oestradiol associated with the onset of oestrus, and falls in the blood levels of testosterone, androstenedione, progesterone and FSH. These results indicate that the changes in plasma gonadal steroid levels after extension of the photoperiod differ markedly from those in rodents or ruminants.     

Reduction of blood viscosity following plasma exchange.

The effect of plasma exchange with plasma protein fraction on blood viscosity was determined in seven hyperlipoproteinaemic patients with coronary or peripheral vascular disease. This resulted in decreases in whole blood viscosity of 83% and 30% respectively at the lowest and highest shear rates studied, and decreases of 21% and 59% in plasma viscosity and fibrinogen. Serum cholesterol and triglyceride were reduced by 66% and 48% respectively. Sequential studies in two patients showed that blood viscosity returned to near-basal values by the 6th day. These findings suggest that plasma exchange may result in short-term enhancement of blood flow in vessels where low shear rates predominate.     

Forward and inverse electrocardiographic calculations using resistor network models of the human torso

An automated method of modelling the electrical properties of the human thorax from horizontal section data such as computerized tomographic scans has been used to develop both forward and inverse transformations between epicardial and body surface potential distributions. Eleven torso models with varying geometry and organ configurations have been studied. For the forward calculations, a standard dipole-like source is placed along the axis of the heart. Inverse calculations are performed using a measured body surface potential distribution and are based on a division of the surface of the heart into 25 source regions, producing epicardial potentials on these regions. A regularization method is used to stabilize the inverse solutions. Both forward and inverse solutions show substantial differences between models. These findings imply that matching models with patient geometry may be necessary in order to use such solutions in a clinical setting.