Supine Hypotensive Syndrome
Aortocaval compression syndrome
Supine Hypotensive Syndrome:
Dizziness and a drop in blood pressure caused when the mother is in a supine position and the weight of the uterus, infant, placenta, and amniotic fluids compress the inferior vena cava, reducing return of blood to the heart and cardiac output.
Signs and Symptoms
- Tachycardia (early sign)
- Bradycardia (very late sign)
- Edema of the lower extremities
- Sings of fetal hypoxia or distress (seen through CTG in hospital)
- Decreased femoral pulse
Supine hypotensive syndrome is caused when the inferior vena cava is compressed by the weight of a pregnant female’s uterus, fetus, placenta and amniotic fluids while lying in the supine position. The effects of supine hypotensive syndrome are very similar to that of shock, but they are not treated in the same fashion.
This condition can develop as early as the second trimester but is maximal during the third trimester, 36 to 38 weeks. When the pregnant female in these stages lies in the supine position, the added weight of the enlarged uterus and its contents will press down on the interior vena cava. The inferior vena cava is the route by which de-oxygenated blood from the lower half of the body returns to the heart. When the inferior vena cava is compressed it reduces the amount of blood that returns to the heart and reduces cardiac output, this can result in a loss of 30% of the effective circulating blood volume. It can take three to seven minutes for significant hypotension to become manifest.
As stated previously, supine hypotensive syndrome can mimic symptoms of shock. This is because when the blood flow from the inferior vena cava is constricted the blood pressure will drop and will contract the uterine arteries and redirect blood to the major organs. This can cause distress for the fetus, where fetal hypoxia can occur and in extreme cases, fetal demise.
The patient will experience reduced blood pressure, signs of shock such as cool, moist and clammy skin, tachycardia (early sign), bradycardia (very late sign), dizziness, syncope or near syncope, pedal edema, nausea, decreased femoral pulse, and signs of fetal distress which can only be detected by way of CTG at a hospital.
Treating supine hypotensive syndrome is rather easy. If the patient is found unconscious and supine (and supine hypotensive syndrome is suspected) the patient can be placed in the left lateral recumbent position symptoms should be immediately alleviated. If she is awake and feeling symptoms of supine hypotensive syndrome have her sit up, and lay on her side, preferably the left side. If a spine injury is suspected and the patient is secured to a backboard you can tilt the backboard by placing a folded towel or sheet under the right side of the backboard, effectively raising the patient and angling her position to the left releasing pressure from the uterus off of the inferior vena cava. This method is effective for transport of any pregnant trauma patient, as it will help to avoid supine hypotensive syndrome as well as shock. Displacing the uterus manually to the left is also a useful, if any other means of relieving the pressure are unavailable.
During labor the patient will be supine with the knees up, so supine hypotensive syndrome is possible, so it is imperative that a rolled up towel or a wedge of some sort be placed under the patients buttocks, elevating the pelvis as indicated for labor and delivery, but have the right side slightly higher than the left in order to tilt the patient to the left slightly.
For the most part, if a pregnant female is complaining of dizziness or other signs or symptoms of poor perfusion, place them in the left lateral recumbent position. This will almost immediately relieve any symptoms, and is recommended universally to place the pregnant patient in the recovery position no matter what, whenever possible. Moving the patient from the supine position to the left lateral recumbent position increases cardiac output by 20% to 100%, and 97% of reported patients in a study, being titled to the left was more satisfactory than titling to the right. As stated before, when proper procedures are performed to treat supine hypotensive syndrome symptoms will alleviate almost immediately, however, blood pressure may take a few minutes to return to its previous level. Blood pressure should be measured while the patient is in the left lateral recumbent position, or after backboard is titled for spinal precautions, as the reading will be inaccurate in the supine position.
- Place patient in left lateral recumbent position or elevate right hip.
- If suspected trauma or spinal injury secure to backboard, tilt backboard to left.
- High flow oxygen via non-rebreather.
- Treat for shock if other signs of shock are present.
- Keep patient warm.
- Transport with a quiet, gentle ride to the hospital.
Illustration of inferior vena cava compression by the gravid uterus.