The 8-year-old boy whose arm was bitten off by a shark in Florida over the weekend remained comatose Tuesday in critical but stable condition. 

Doctors say he likely suffered brain injury from blood loss, although they're not yet sure to what extent. 

Family members have been taking turns standing at Jessie Arbogast's bedside at Sacred Heart Children's Hospital in Pensacola, Fla., in an intensive-care room crammed with medical machinery. 

"In speaking with the family, it is a time in their life where really time has stopped," said Sister Jean Rhoads, vice president for mission services with the Sacred Heart Health System. "They are very focused and centered on Jessie's condition and care." 

Dr. Jack Tyson, one of the first physicians to treat the boy after the attack, said on NBC's Today show Wednesday morning that there may have been some hopeful signs. 

Nurses reported that Jessie "apparently attempted to open his eyes ... even perhaps looked over at them as they were talking," Tyson said. 

"This is a small thing, but it's better than nothing," he added. 

Surgeons reattached Jessie's right arm after it was bitten off by the 7-foot bull shark Friday while he was wading in knee-deep water on a Florida Panhandle beach. The boy's uncle and another beachgoer wrestled the shark to shore, where a ranger shot it and pried its jaw open while a firefighter pulled the arm out of the shark's gullet. 

The boy also suffered a severe leg wound and was nearly drained of blood, which harmed virtually every organ in his body and has probably caused some brain damage. 

His parents, David and Claire Arbogast, of Ocean Springs, Miss., are most often at Jessie's side, but he also has received visits from other members of a large extended family, Rhoads said. 

"They talk frequently to him, try to make sure he is comfortable ... anything to keep Jessie realizing they are there," Rhoads said. 

But doctors were unsure of what, if anything, Jessie can comprehend although they say he appears to have avoided potentially fatal brain swelling and does not seem to be worsening. 

"He likely has suffered a brain injury and that very well could be significant for him," said Dr. Tim Livingston, a pediatric neurologist. "We do have evidence that his brain is not functioning correctly." 

Doctors had not used the term coma before Tuesday, although the boy has been in critical condition since the attack. Livingston said tests showed brain activity akin to deep sleep or a light coma.   

The Associated Press contributed to this report