PITTSBURGH -- Children suffering from high levels of sodium in their blood -- like a 4-month-old infant allegedly poisoned with salt water by his mother this week -- are at high-risk for permanent brain damage, if they survive, doctors said Friday.

The doctors, all specialists in children's health, said high levels of salt cause the brain to shrink and cells to burst, leading to seizures, brain bleeding and even coma -- all injuries that can lead to permanent damage.

None of the doctors are directly involved with the case of Noah King, an infant from Tennessee whose mother, Amber Brewington, has been arrested in Pittsburgh on charges she injected him at least five times with salt water.

But all agreed that the level of sodium Noah had when he arrived at Children's Hospital of Pittsburgh -- 215 units per deciliter -- was well above normal levels of about 135 to 145, and could not have been caused by any natural illness. Noah remains in critical condition.

"Death is a possibility of high serum sodiums, and the higher the sodium, the greater the chance of permanent neurological injury or death," said Dr. Basil Zitelli, a pediatrician at the hospital.

Brewington, 21, tried to poison her son by repeatedly injecting salt water into his hospital feeding tube in what she claimed were attempts to hasten the death of a sick and suffering child, police said.

She is in the Allegheny County Jail on a charge of attempted homicide. A preliminary hearing is scheduled for Wednesday, but she does not yet have an attorney listed. Brewington told police she suffers from severe postpartum depression.

There are several conditions that can cause high levels of sodium in the blood, including severe, long-term diarrhea and vomiting or diabetes insipidus, an illness in which the kidneys fail to retain water. However, it would be unlikely, if not impossible, for the levels to surpass 200, doctors said.

A 1993 study on salt poisoning in children done by British pediatrician Roy Meadow found that two of four children died when sodium levels exceeded 200. Meadow is best known for research on Munchausen syndrome by proxy, in which a caregiver fakes or induces illness in others to generate sympathy.

Dr. Jordan Symons, a kidney and dialysis expert at Seattle Children's Hospital, said thirst is a primitive mechanism for the body to balance fluids, so illness does not generally cause severely high levels of sodium.

"A serum sodium concentration above 200 would be extremely difficult to achieve in an infant, probably in anybody ... related to natural illness or disease," Symons said. "So were a number above 200 to be seen, it would make one wonder how that possibly could have happened."

In early May, Noah was admitted to a medical center in Columbia, Tenn., according to police. He was soon transferred to Vanderbilt University Hospital, where his mother told police he suffered from "possible brain damage and life-threatening seizures" from an unknown cause.

Pittsburgh police Cmdr. Thomas Stangrecki said investigators believe all of Noah's illnesses are directly related to his mother's actions, but police are still trying to obtain medical records from the facilities that treated him.

Zitelli said a child suffering from naturally occurring high sodium levels would have symptoms related to other diseases, such as faulty kidney functioning, weight loss or prolonged vomiting or diarrhea.

"A child who is just ingesting sodium wouldn't have these signs, so it would be suspicious," Zitelli said.