In it's basic form it means lack of oxygen. This word arises in two types of medical malpractice cases.
It comes up in (1) anesthesia cases and in (2) brain-damaged baby cases.
In an anesthesia case, we typically see a patient who undergoes surgery and there is some deprivation of oxygen leading to brain injury or death.
In a brain-damaged baby case it typically involves a mother who is in labor, preparing to give birth. As a result of not recognizing the baby being in distress, the uterus may become a hostile environment and the baby may be deprived of oxygen.
Prolonged lack of oxygen can lead to brain damage and possibly death.
Anoxia means a total lack of oxygen. There are other medical terms that mean a diminished or decreased amount of oxygen.