A Sydney nurse has been accused of significantly contributing to the death of an elderly female patient by administering a mix of oral medication tablets via an intravenous drip.

Prosecutors say nurse Mavis Lopez was so grossly negligent in her treatment of 97-year-old Nymphea Anderson at St George Hospital that she ought to be convicted of manslaughter by criminal negligence.

Allegedly negligent: Mavis Lopez has pleaded not guilty to manslaughter. Credit:Michele Mossop

But the nurse has pleaded not guilty to the charge, saying that while she did administer the medications in the wrong way, this mistake may not have contributed to the patient's death and does not warrant a charge of manslaughter in any case.

The trial of Ms Lopez, 44, in the Downing Centre District Court heard last week that Mrs Anderson presented to St George Hospital on January 27, 2009 with nausea, vomiting, a urinary tract infection, angina and dehydration.