Background Incorrect intravenous administration of concentrated potassium chloride (KCl) solutions is potentially lethal. The Quality Agency for the Spanish National Health System has recommended safe practices to reduce this risk.

Purpose To describe the implementation of standardised labelling of KCl solutions by nursing staff and evaluate adherence.

Materials and methods In May, 2011 the hospital group for the safe use of medication identified KCl as a hazardous drug. It decided to introduce labelling of diluted KCl solutions by the nursing personnel responsible for preparing and administering them in cardiology, cardiac surgery, emergency observation, coronary care, postoperative care, postcardiac care and intensive care. Information on the label should include patient identification, prescribed KCl dose, volume and solution type. A month-long (22 August–26 September 2011) prospective observational study with 10 cross-sectional time points was conducted. Two independent observers evaluated adherence to the safe practice. The percentage adherence (%) was calculated by dividing the number of patients with labelled KCl solution by the total number of patients prescribed KCl.

Results Of the total 898 patients hospitalised in these wards during the study, those prescribed KCl included 14 in cardiology, 18 in cardiac surgery, 34 in coronary care, 14 in emergency observation, 8 in postoperative care, 32 in postcardiac and 78 in intensive care. The percentage adherence for labelling of KCl solutions by nursing staff was 100% in all units except cardiac surgery (88.8%) and intensive care (97.4%).

Conclusions Adherence to the labelling initiative of the group for the safe use of medication was very high, almost 100%. Safe practices that reduce patient risk increase the quality of health systems and the level of satisfaction among healthcare professionals.