A state investigation couldn't pinpoint what caused the mysterious death of a toddler in routine surgery last year, but it did fault Fairview Southdale Hospital in Edina for poor record-keeping of her vital signs.

Calla Christopherson was having a simple outpatient procedure to open a clogged tear duct Aug. 22, 2006, when the 2-year-old's breathing became labored and her oxygen level started falling. One doctor injected a muscle relaxant in the girl, but her heart rate then started falling as well. An emergency team tried but failed to resuscitate her.

The hospital violated federal health care standards, according to the state investigative report released Wednesday, because the surgical team failed to continuously update the girl's blood pressure and other vital signs in the surgical record.

The amount of muscle relaxant given to Calla was unclear, as it was recorded differently in medical records and a physician's handwritten notes, according to the report from the Minnesota Department of Health. An initial blood test during autopsy also suggested an overdose of anesthesia, but a follow-up test ruled that out.

The investigation started with a complaint from Calla's mother, who was concerned by the gaps in vital sign data she received.

"I'm angered, because this just shouldn't happen," said Holly Christopherson, who adopted Calla from China and brought her to Minnesota in 2005 when she was a year old. "Nobody should have to go through this."

The anesthesiologist in the case told state investigators he was sure he gave the girl the right doses of medication. The discrepancy over the amount of muscle relaxant occurred, he said, because he had squirted some out of a syringe to ensure that what was left inside was the correct dosage.

He added that Calla's vital signs were monitored on machines but weren't copied into the medical record because the surgical team was focused on trying to save the dying patient.

A nurse anesthetist said that she was given a "very short period of time" to update the medical record before the vital signs were deleted from the monitoring machine but that she was too despondent over the girl's death to do so. She told a state investigator she "was so upset she just stared at the chart and could not gather herself to write anything," according to the report.

Calla had a heart defect common in babies, but the autopsy ruled that out as a cause of death. Holly Christopherson, of Burnsville, said the past year has been difficult. Her last moment with Calla was laying her on the operating table.

"She was beautiful, sweet, loving, affectionate, happy," she said.

Explaining the death to Calla's 5-year-old sister, Kiah, has been particularly difficult.

"She doesn't understand finality," the mother said. "We just had Calla's birthday. She thought she was going to come back."

Allison Page, Fairview's vice president for patient safety, expressed sympathy for the family. The hospital has responded by designating one person to handle recordkeeping throughout each surgery. An internal review found no fault in the actual care for the girl, whose death remains a troubling mystery, Page said. "The team did really everything possible to try to save her life."

Jeremy Olson can be reached at jolson@pioneerpress.com or 651-228-5583.