1, pregnant women lying flat will die? It was recently reported that a 41-year-old obese pregnant woman (height 173cm, weight 128kg, pre-pregnancy 113kg) was admitted to the hospital at 37 weeks for excess amniotic fluid with suspicion of gestational diabetes and macrosomia, and her husband found her dead in her bedroom on the 9th day after discharge. She was lying flat on her back, and the autopsy confirmed dilated jugular veins (in the neck) and subclavian veins (in the chest), atrophied inferior vena cava, and dilated and congested veins in the lower extremities bilaterally. The diagnosis of “supine hypotension syndrome” was made as the probable cause of death. 2. Why do up to 75% of pregnant women experience shortness of breath during pregnancy? Up to 75% of pregnant women experience shortness of breath during pregnancy. There are many reasons for this phenomenon, two of which are important. (1) When lying down, there is very little oxygen left in the lungs (shortness of breath), which is severely reduced during pregnancy as the diaphragm (the respiratory muscle between the chest and abdominal cavities) rises and squeezes the lungs. At full term, it is 80% lower than before pregnancy; when lying down, it is 70% lower than the 20% left. Also, oxygen consumption during pregnancy is 40-75% higher than before pregnancy. (2) When lying flat, the blood pressure drops and there is insufficient blood (oxygen) supply to the organs (nausea) The drop in blood pressure and insufficient blood (oxygen) supply to the organs can cause breathing difficulties. It can also make the patient feel nausea, vomiting, chest and abdominal discomfort or pain, numbness in the hands and feet, impaired vision, ringing in the ears, headache, dizziness, irritability, etc. Shock symptoms such as panic, pallor or bruising, and sweating can even occur. In more serious cases, pregnant women can pass out. Many mid- to late-stage pregnant women sometimes lie down on their own will find the above symptoms, the patient is willing to bend the knees to hold the legs or their own into the side lying position. Obstetricians have long been aware of these phenomena, and found that, in the middle and late stages of pregnancy, pregnant women lying down in addition to lower blood pressure, lower extremity venous pressure is increased. 3, after 20 weeks of pregnancy, must not lie flat? Although, the gestational uterus began to come out of the pelvic cavity at 12 weeks, but generally by 20 weeks, the bottom of the uterus can be felt at the level of the navel, that is to say, the uterus really into the abdominal cavity. Therefore, experts recommend that pregnant women after 20 weeks of pregnancy must not lie flat on their backs, no matter what. Especially some high-risk patients, such as: preterm labor, multiple births, huge children, obese and other pregnant women. Labor should be more careful, because generally speaking, low blood pressure occurs within 3-10 minutes after lying down, in case you fall asleep during this period of time, there is a real possibility that you will never wake up again Health care workers should also be especially careful to keep the left side of the mother’s uterus tilted position all the time during labor and delivery, and in the case of cesarean section or non-obstetrical surgery after 20 weeks of gestation, the patient passes to the surgical bed, the first thing is to put the patient’s right side of the span of the pad high The patient’s right side is elevated. Otherwise, under general or lumbar anesthesia, vasoconstrictive compensatory capacity is reduced. There are reports in the literature, because of this loss of compensation, lumbar anesthesia-induced drop in blood pressure coupled with “supine hypotension” may lead to cesarean section after lumbar anesthesia patient circulatory failure and death. 4, what is supine hypotension syndrome? Here, we mainly talk about blood pressure, which is the arterial blood pressure that your doctor usually measures. In the 1930s and 1950s, there were many such cases reported in the medical literature. It was not until the 1950s and 1960s that doctors were able to figure out what caused this phenomenon and named it “supine hypotension syndrome” due to compression of the aorta (the large artery in the abdominal cavity) and the inferior vena cava (the large vein in the abdominal cavity). Venous blood from the lower extremities normally returns to the heart through the inferior vena cava in the abdominal cavity. (1) The uterus grows with each month of pregnancy, and by the time you can feel your uterus, around 20 weeks of pregnancy, the uterus has moved from the pelvic cavity into the abdominal cavity. Then, when you stand or lie on your side, the uterus will not press on the inferior vena cava. (2) When you lie down, the uterus will press on the inferior vena cava (venous pressure is lower than arterial pressure, and the walls of the veins are thinner than the walls of the arteries, and therefore, they are easily pressurized.), so that venous blood from the lower limbs can not be completely returned to the heart, and at the same time, it causes the venous blood pressure of the lower limbs to be elevated. Without blood back to the heart, the heart beats more vigorously, but also can not deliver anything to the whole body. The heart can’t pump enough blood, which causes the blood pressure to drop, and pregnant women will experience the various symptoms mentioned above. (3) When you take the initiative to become a side-lying position, the inferior vena cava is no longer under pressure. When you bend your knees and hold your legs, you can increase the venous pressure in the lower limbs and overcome some of the insufficient blood return to the heart due to the compression of the inferior vena cava, so you will feel some relief from the symptoms. When you lie down, in addition to the compression of the inferior vena cava, scientists later found that the aorta in the abdominal cavity is also partially compressed (4) Causing insufficient perfusion of the distal branches of the arteries (e.g., uteroplacental arteries and arteries of the lower limbs). (5) Inadequate blood flow to the uteroplacenta may lead to placental abruption and fetal hypoxia. Decrease in blood pressure can also cause insufficient cerebral oxygenation and decreased renal blood perfusion in pregnant women, coupled with compression of the ureter by the uterus, resulting in decreased urine output. 5.How to deal with “supine hypotension syndrome” caused by aortic-inferior vena cava compression? Many pregnant women instinctively lie on their sides to relieve their discomfort, which tells us the answer. Clinical trials have also confirmed that elevating the right hip of the pregnant woman and tilting the pelvis to the left by 15-30 degrees, although not completely relieved, can reduce the pressure on the aorta-inferior vena cava, thus effectively minimizing the complications of compression of these blood vessels. Babies of mothers in the 15-degree tilted position had better cord blood chemistry and clinical scores after birth compared to babies of flat lying mothers. If left uterine tilt does not result in relief of the patient’s symptoms or fetal heart abnormalities, the patient can be placed in a full left lateral position or try to right-tilt the uterus by having the patient’s left crotch padded. In short, the angle and direction of padding should be adjusted according to the patient’s specific situation. If there is no special water bladder air bag, we often use a large pillow or rolled up blanket, the right side of the pregnant woman’s waist and crotch together with the cushion, so as not to make the patient twisted waist uncomfortable. 6, “supine hypotension syndrome” incidence is not 100%, why? Because when the aorta and inferior vena cava are obstructed, our body will have some ways to cope with it: (1) to establish more collateral circulation of the arteries and veins, so that the blood flow bypasses the obstructed area; (2) the nerve reflex will compensate for the increase in vasoconstriction to raise the blood pressure, etc.; (3) pregnant women with different degrees of lumbar spinal protrusion, protruding significantly so that the inferior vena cava is less likely to be compressed. However, we have no way of determining which individuals have sufficient arteriovenous collateral circulation to compensate for subaortic vena cava obstruction; which individuals have nerve reflexes active enough to vasoconstrict blood vessels to the extent that blood pressure is normalized; and we have no way of predicting spine-uterus relationships, uterine shape, and degree of tenderness in different individuals. Also, experiments have confirmed that lower extremity (femoral) and (N) arterial pressures perfused by the lower branches of the abdominal aorta can be reduced when upper extremity arterial pressures are normal. In other words, even if the mother’s blood pressure measured in the upper limbs is normal, it does not exclude the possibility of insufficient blood flow to the uterus and fetal damage due to abdominal aortic compression. 7. Will painless labor be affected by “supine hypotension syndrome”? “Supine hypotension syndrome occurs in more than 30% of pregnant women, and the incidence is higher in patients who have labor analgesia or intrathecal anesthesia, which itself causes a decrease in blood pressure. However, this is not to say that we do not advocate labor analgesia or intrathecal anesthesia. Quite the contrary, we believe that the benefits of labor analgesia outweigh the disadvantages for both the mother and the fetus, and actively encourage epidural labor analgesia. The “supine hypotension syndrome” can be prevented, and hypotension caused by labor analgesia or intrathecal anesthesia can be treated. Moreover, anesthesiologists are paying more attention to this aspect, and there are reports in the literature of an increase in the overall safety of the mother and baby. Therefore, to ensure the safety of every mother and fetus, we require that all pregnant women over 20 weeks of gestation maintain a left-tilted uterine position.