A woman in the third trimester of pregnancy is predisposed to supine hypotension syndrome in pregnancy while in the supine or sitting position due to the hemodynamic and anatomic changes of pregnancy.
The large uterus of late pregnancy can compress the inferior vena cava (IVC) such that venous return is significantly reduced.
This decreased preload can lead to decreased cardiac filling and hence decreased cardiac output and hypotension.
Supine hypotension syndrome in pregnancy can be especially deleterious in the usual setting of increased cardiac demand in pregnancy.
Of normovolemic pregnant patients, only 8% to 10% display supine hypotension syndrome in pregnancy due to adequate physiologic compensation; however, when faced with blood or other fluid losses such as in trauma or critical illness, supine hypotension of late pregnancy is more prevalent.
In these instances of supine hypotension syndrome in pregnancy, simple repositioning can be life saving. Establishing left uterine displacement by elevating the patient’s right side greater than 15 degrees allows the uterus to be displaced off the inferior vena cava.
After a traumatic injury, before this maneuver is performed assessment of the stability of the patient’s spinal cord must be undertaken, and if uncertainly exists, the patient should not be moved without using formal spinal precautions.