What are the two main components of the fetal response to hypoxic stress?
The fetal brain sparing response to acute hypoxia is triggered by a carotid chemoreflex that leads to bradycardia and an increase in peripheral vasoconstriction.
How does preload affect cardiac output?
Preload is related to cardiac performance through the Frank-Starling law of the heart; a decrease in preload diminishes the force of ventricular contraction and therefore decreases stroke volume. As a result, preload reduction generally results in a decrease in cardiac output.
What is the direct effect of increased preload?
From studies in isolated heart preparations in which preload, afterload, and contractile state were controlled, it has been shown that an increase in preload, produced by an increase in end-diastolic volume, results in an increase in the end-systolic pressure and the stroke volume of the ensuing beat.
How does the fetus increase cardiac output?
Cardiac output early in gestation is thought to be mediated by the increase in stroke volume, whereas later in gestation, the increase is attributable to heart rate. Stroke volume increases gradually in pregnancy until the end of the second trimester and then remains constant or decreases late in pregnancy.
What causes fetal hypoxia?
Intrauterine hypoxia (also known as fetal hypoxia) occurs when the fetus is deprived of an adequate supply of oxygen. It may be due to a variety of reasons such as prolapse or occlusion of the umbilical cord, placental infarction, maternal diabetes (prepregnancy or gestational diabetes) and maternal smoking.
What causes fetal acidosis?
Maternal causes of chronic fetal acidosis include reduced oxygenation of maternal blood, such as in severe respiratory or cardiac disease, or reduced blood flow to the placenta as in connective tissue diseases—for example, systemic lupus erythematosus—and pre-eclampsia.
What is preload dependent?
As mentioned in the article,1 preload dependence is defined as a state in which increases in right ventricular and/or left ventricular end-diastolic volume result in an increase in stroke volume. 2. Changes in preload could be due to hypovolemia and/or a decrease in venous tone with increased venous capacity.
What factors affect preload?
Factors affecting preload Preload is affected by venous blood pressure and the rate of venous return. These are affected by venous tone and volume of circulating blood. Preload is related to the ventricular end-diastolic volume; a higher end-diastolic volume implies a higher preload.
What happens when preload increases?
Increased preload increases stroke volume, whereas decreased preload decreases stroke volume by altering the force of contraction of the cardiac muscle. The concept of preload can be applied to either the ventricles or atria.
What prevents maternal and fetal circulation from mixing?
In general, the spiral arteries are perpendicular to the uterine wall, while the veins are parallel to the uterine wall. This arrangement facilitates closure of the veins during uterine contractions and prevents squeezing of maternal blood from the intervillous space.
What is the key mechanism for regulating fetal blood pressure?
The medulla oblongata contains the vasomotor center that responds to baroreceptors, chemoreceptors and catecholamines. It also regulates peripheral blood vessel dilation and constriction to help maintain normal blood pressure and distribution of blood to vital organs.
What does mild fetal hypoxia mean?
Pediatrics. Intrauterine hypoxia (also known as fetal hypoxia) occurs when the fetus is deprived of an adequate supply of oxygen. It may be due to a variety of reasons such as prolapse or occlusion of the umbilical cord, placental infarction, maternal diabetes (prepregnancy or gestational diabetes) and maternal smoking …