Opiates were found in the blood of three newborns stricken with breathing difficulties on the same day at Anne Arundel Medical Center, and hospital officials said yesterday that they didn't know how the drugs got there.
Officials have not ruled out the possibility that somebody tried to harm the babies, who were listed as stable in the critical-care nursery.
"That's not something we like to think about, but we're not precluding any options," said Beth Evins, director for administration and customer relations at the Annapolis hospital. "We have to look at it. We have to look at the environment. We have to look at the beds they're in. We have to look at the medications they were taking."
Frequently, drugs are detected in the babies of mothers who used them during pregnancy, but "that has been ruled out," said Carolyn Shenk, a hospital spokeswoman.
For now, the investigation is being conducted internally with the assistance of outside medical authorities. The police have not been contacted yet because criminal activity is not the prime suspicion, Ms. Evins said.
"We're doing as much as we can as quickly as we can," Ms. Evins said. "From our perspective, we're going to continue this investigation until we have an answer."
Security has been tightened at the center, hospital officials said.
Hospital officials held a news conference yesterday afternoon to calm fears after they were called by people who had heard that something had gone wrong at the year-old critical-care nursery.
Early Tuesday, a nurse noticed one of the seven babies in the unit was having breathing problems. At about the same time, another infant had almost the same symptoms.
About 14 hours later, a third infant had similar difficulties. None of the babies stopped breathing and none went into cardiac arrest, said Sharon Rossi, clinical director of perinatal services.
The three infants were stabilized quickly by the nursing staff and are not suffering any permanent damage, hospital officials said.
"A full recovery is expected," Ms. Rossi said. "It was a transient kind of condition in the infants and it's corrected itself."
A routine toxicologic test showed traces of an opiate or %o opiate-like substance, which has not been precisely identified, Ms. Evins said. An opiate, such as opium, morphine, codeine or heroin, is a central nervous system depressant that impairs breathing.
Such breathing difficulties are not uncommon among infants in the critical-care unit, Ms. Rossi said. What is unusual was the timing, and the fact that all three had traces of the opiate in their systems.
Toxicologic tests routinely are given to newborns to determine whether their mothers may have taken drugs during pregnancy. After the incidents, all the infants in the critical-care unit were transferred for about 24 hours to an adult coronary care unit while the nursery was examined.
The hospital has installed a locking system that will admit only the staff to the nursery. All medication and medical supplies stored on the unit have been replaced, Ms. Rossi said.