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Using Six Sigma to improve once daily gentamicin dosing and therapeutic drug monitoring performance
  1. Sean Egan1,
  2. Philip G Murphy2,3,
  3. Jerome P Fennell2,
  4. Sinead Kelly2,
  5. Mary Hickey4,
  6. Carolyn McLean5,
  7. Muriel Pate1,
  8. Ciara Kirke1,
  9. Annette Whiriskey1,
  10. Niall Wall2,
  11. Eddie McCullagh2,
  12. Joan Murphy6,
  13. Tim Delaney1
  1. 1Pharmacy Department, Tallaght Hospital, Dublin, Ireland
  2. 2Microbiology Department, Tallaght Hospital, Dublin, Ireland
  3. 3Department of Clinical Microbiology, Trinity College Dublin, Ireland
  4. 4Process Improvement Department, Tallaght Hospital, Dublin, Ireland
  5. 5Nurse Practice Development Department, Tallaght Hospital, Dublin, Ireland
  6. 6Phlebotomy Department, Tallaght Hospital, Dublin, Ireland
  1. Correspondence to Sean Egan, Antimicrobial Pharmacists, Pharmacy Department, Tallaght Hospital, Belgard Road, Tallaght, Dublin 24, Ireland; sean.egan{at}


Background Safe, effective therapy with the antimicrobial gentamicin requires good practice in dose selection and monitoring of serum levels. Suboptimal therapy occurs with breakdown in the process of drug dosing, serum blood sampling, laboratory processing and level interpretation. Unintentional underdosing may result. This improvement effort aimed to optimise this process in an academic teaching hospital using Six Sigma process improvement methodology.

Methods A multidisciplinary project team was formed. Process measures considered critical to quality were defined, and baseline practice was examined through process mapping and audit. Root cause analysis informed improvement measures. These included a new dosing and monitoring schedule, and standardised assay sampling and drug administration timing which maximised local capabilities. Three iterations of the improvement cycle were conducted over a 24-month period.

Results The attainment of serum level sampling in the required time window improved by 85% (p≤0.0001). A 66% improvement in accuracy of dosing was observed (p≤0.0001). Unnecessary dose omission while awaiting level results and inadvertent disruption to therapy due to dosing and monitoring process breakdown were eliminated. Average daily dose administered increased from 3.39 mg/kg to 4.78 mg/kg/day.

Conclusions Using Six Sigma methodology enhanced gentamicin usage process performance. Local process related factors may adversely affect adherence to practice guidelines for gentamicin, a drug which is complex to use. It is vital to adapt dosing guidance and monitoring requirements so that they are capable of being implemented in the clinical environment as a matter of routine. Improvement may be achieved through a structured localised approach with multidisciplinary stakeholder involvement.

  • Gentamicin
  • aminoglycosides
  • quality improvement
  • therapeutic drug monitoring
  • drug safety
  • antibiotic management
  • pharmacists
  • clinical pharmacology
  • continuous quality improvement
  • six sigma
  • patient safety
  • quality improvement methodologies
  • teamwork
  • process mapping

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  • Competing interests None.

  • Patient consent Patient consent not sought. All changes to policy were made under the direct supervision of the hospital Drugs and Therapeutics Committee and were based on previously published work, with dose administration timing adjusted based upon inhouse pharmacokinetic evaluation.

  • Ethics approval Ethics approval was provided by Tallaght Hospital Ethics Committee/Tallaght Hospital Drugs and Therapeutics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Audit data before and after intervention are available. In addition, anonymised patient level data are available for review.