Which of the following is the least likely physiological change in pregnancy
Ans. is 'd' i.e. increase in peripheral vascular resistance Hemodynamic changes during pregnancyThe most important point to remember about cardiovascular changes during pregnancy is that in normal pregnant patients, circulation is hyperdynamic and that a high cardiac output is present.The increase in cardiac output starts about 10 weeks into the pregnancy reaches the maximum at about 24-28 weeks and remains elevated until parturition.The rise in cardiac output is initially determined by increase in stroke volume and later on as the pregnancy advances the heart rate also increases.An increase in intravascular volume is one of the main determinants of the increased cardiac output of pregnancy.There is an increase in both red cell volume and plasma volume.A good clinical marker of the presence of an expanded I. V. volume during pregnancy is the presence of grade 2/6 systolic ejection murmur.This physiologic murmur appears at about 10-12 weeks into the pregnancy and disappears in the beginning of the postpartum period.The increase in the intravascular volume fulfills the needs of the developing uteroplacental circulation and protects the mother against the potentially harmful effects of the blood loss that occurs at parturition.The increase in blood volume of pregnancy does not alter the central venous pressure (CVP), which is the same as in the nonpregnant women.Another important hemodynamic change in pregnancy is decreased peripheral vascular resistance (PVR).PVR decreases during pregnancy on the arterial side and the venous side of the circulation. The cause of this change is not well understood, but is most likely a direct effect of placental hormones or vasodilator prostaglandins (prostacyclins) on blood vessels.The decreased peripheral vascular resistance is manifested clinically by a decrease in both mean and diastolic blood pressure. This decrease is clearly observed during second trimester.Because most of the intravascular volume is contained in the capacitance vessels, the decrease in venous resistance represents the adaptation of the vascular tree to the blood volume expansion. If this adaptation does not occur, thev. volume will not expand, thereby seriously compromising the uteroplacental circulation.Hemodynamic changes in normal pregnancy*Cardiac output- Increased*Heart rate- Increased*Systemic vascular resistance- Increased*Pulmonary vascular resistance- Increased*Mean arterial pressure- Increased*Pulmonary capillary wedge pressure- Increased*Central venous pressure- Normal*Left ventricular stroke volume- IncreasedAlso knowThere are several periods during pregnancy when the danger of cardiac decompensation is especially great.First is between 12 and 32 weeks of gestation, a time during which hemodynamic changes of pregnancy develops.The most critical period is between 28-32 weeks of gestation, when the hemodynamic changes of pregnancy peak and cardiac demands are maximum.The other dangerous time for pregnant cardiac patient is during labour and delivery.During labour every uterine contractions injects blood from the uteroplacental circulation into the maternal blood stream increasing the cardiac output by approximately 15% to 20%.This continuous demand on the heart may trigger congestive heart failure,During the second stage of labour, maternal pushing further compromises the venous return to the heart causing a decrease in cardiac output that may be critical for some cardiac patients.The final dangerous time for the pregnant cardiac patient is 4-5 days after delivery.Patients with primary pulmonary hypertension, Eisenmenger's syndrome, Aortic stenosis and cyanotic heart disease may be able to go through pregnancy and labour and delivery without major complications.However, sudden death in the early postpartum period may occur. Decreased peripheral resistance with right to left shunting and pulmonary embolization from silent iliofemoral thrombus are two problems occurring at this time.
Increase in intravascular volume
Increase in cardiac output
Increase in stroke volume
Increase in peripheral vascular resistance
Cardiovascular System