A nursing sister broke down in tears as she told an inquest of her shock and distress at the sudden death of her three-year-old patient.

Sister Daina Dumpnieks said she arrived at work at 7.30am to learn that Naazish Farooq had suffered a cardiac arrest.

The sister told yesterday how she had left Naazish, of Great Horton, Bradford, in a stable and improving condition on a ventilator in St James's Hospital, Leeds, on the evening of October 7, 1999.

The inquest at Leeds Coroner's Court has heard that a phenomenally high potassium level was recorded in Naazish's blood as hospital staff tried desperately to save her in the early hours of the next morning.

Sister Dumpnieks fought back tears as she told of the distress of Naazish's family as they arrived at the intensive care unit at the hospital.

She said she collected the death certificate that morning and gave it to Naazish's uncles. She had heard talk about Naazish having a high potassium level in her blood when she died.

"I was aware that there were doubts but got no impression of any disagreement among the hospital staff," she said.

Naazish had been diagnosed with a rare form of lymph cancer after she was admitted to the hospital from St Luke's in Bradford on September 24.

The cause of her death was certified as a cardio-respiratory attack and B-Cell lymphoma. She was buried the same day in accordance with the family's religion but her body was exhumed when a police investigation was launched following the discovery that she had more than twice the lethal level of potassium in her blood at the time of her death.

Pathologist Christopher Milroy found that cause of death was consistent with potassium poisoning but he could not be certain how she died.

Dr Margaret Fitzpatrick, a paediatric renal consultant, told the inquest that the dialysis method used for Naazish had worked well at the hospital for eight years although only six or seven children a year went through the process.

Naazish had been given dialysis fluid injected with potassium for the 12 days prior to her death. The bags were changed and mixed every two to three hours.

Dr Fitzpatrick said she was very surprised by Naazish's death but she did not believe that any fault in the dialysis equipment was to blame.

She said that the 18.9 level of potassium recorded in Naazish's blood at the time of her death was outside her experience. She had never encountered such a level during her career or in any medical literature.

"I really would concur with most of the suppositions that this really would need to be repeated because it cannot be right," she said.

She added that if potassium had layered in the bottom of Naazish's dialysis bag she would have expected it to have crept up to danger level rather than having happened suddenly.

"There would be some signs of the heart not coping," she said.

She said that warning changes on the ECG machine would be characteristic and bizarre.

Dr Fitzpatrick said that she believed a second reading of 12.4 was a consequence of Naazish's cardiac arrest.

Coroner David Hinchcliffe said the inquest will not finish this week. It will have to be further adjourned to a date in March.