Rigid penile shaft, but the tip of penis (glans) is soft.Erection lasting more than four hours or unrelated to sexual interest or stimulation.Ischemic priapism is the more common type of priapism and requires immediate medical care to prevent complications caused by not getting enough oxygen to the penile tissue. Blood is trapped in the penis because it cannot flow out of the veins of the penis or there is a problem with the contraction of smooth muscles within the erectile tissue of the penis. Ischemic priapism, also called low-flow priapism, is the result of blood not being able to leave the penis.