Seven-month-old twins Patrick and Benjamin Binder remained in critical but stable condition a day after the 22-hour operation to separate the pair, born joined at the head. Doctors at Johns Hopkins Children's Center in Baltimore were keeping the West German twins in a drug-induced coma, or "prolonged anesthetic sleep," as they recover from the rigors of the surgery. "We're slightly encouraged they're doing well," said Dr. Mark Rogers, who coordinated the surgery. But he also emphasized: "We will not know how this turns out for several weeks." Two major risks are bleeding and swelling of the brain tissue.