Innovative home grown calculator improves the safety of aminoglycoside use

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Infections caused by Gram-negative bacteria are becoming increasingly prevalent and constitute a serious threat to public health. They are difficult to treat and are frequently associated with high morbidity and mortality rates. Now a Queensland-developed calculator for the use of bacteria-killing aminoglycoside antibiotics will help make it easier for clinicians throughout the state to safely prescribe and administer these powerful but high-risk drugs.

Aminoglycosides are a commonly-used class of highly effective broad-spectrum antibiotics, such as Gentamicin, Tobramycin and Amikacin. They are used for the treatment of serious Gram-negative pathogens including intra-abdominal infections, urinary tract infections, and importantly in the management of sepsis.

While they provide a broad range of Gram-negative cover, their narrow therapeutic window means that dosing must be individualised to each patient for safe and effective use. Incorrect dosing can result in failure of treatment (under-dosing) or significant adverse effects including vestibular toxicity, ototoxicity and renal toxicity (excess dosing).

In September 2020 the Sunshine Coast Hospital and Health Service (SCHHS) Antimicrobial Stewardship (AMS) team, in a joint initiative with the SCHHS ICT Software Development team, launched a desktop calculator to help prescribers and pharmacists facilitate the dosing of aminoglycosides, ensuring that safe and efficacious empiric doses of aminoglycoside antibiotics were prescribed to patients.

The SCHHS Antimicrobial Stewardship (AMS) team consists of AMS pharmacists Tricia Kilfoyle and Sarah Kingscote, and infectious diseases physician Dr Kathryn Wilks.

“We know that dosing of aminoglycosides requires several manual calculations and application of patient-related information, and prescribing of these antibiotics is required to be prompt at a time of complex and competing clinical priorities,” Ms Kilfoyle said.

The AMS team said that the aminoglycoside calculator addresses this by using the evidence-based recommendations of the QLD Health ‘Aminoglycoside Dosing in Adults’ guideline and removing the need for multiple manual calculations.

“It incorporates patient specific parameters including height, weight, renal function and presence of septic shock to calculate a dose specific to the patient’s requirements. The calculator also applies whether or not to use the ideal, actual or adjusted body weight as appropriate in the dosing calculation. 

“Our strategy minimises the risk of incorrect dosing, aids in highlighting contra-indications and ensures adequate dosing and administration in patients with sepsis and septic shock.

“The calculator aims to give our clinicians one less thing to worry about,” Ms Kilfoyle said.

Video Tutorial: Introduction to the SCHHS Aminoglycoside Calculator (10 mins)

The aminoglycoside calculator has deployed to over 6,000 clinical workstations across SCHHS. The 2020 launch included a broad communications campaign in conjunction with the production of a mandatory introductory Learning Management System (LMS) module for all prescribers and pharmacists commencing in SCHHS to familiarise both existing and new staff with the application.

The calculator has been used over 2,000 times to assist in aminoglycoside prescribing, and the high uptake by prescribers demonstrates that there was a clinical need to assist with aminoglycoside dosing even despite the ongoing competing demands of the COVID-19 pandemic.

“Feedback from our SCHHS clinicians has been unequivocally positive in that the calculator is easy to access, easy to use and provides them with clear direction as to what to prescribe,” Ms Kilfoyle said.

The aminoglycoside calculator is now available for clinicians state wide and part of CKN’s Antimicrobial Stewardship suite of resources.

“We’re excited to share the tool with our colleagues across Queensland Health as we believe that patient safety and risk reduction strategies should be available to use across services,” Ms Kilfoyle said.

The SCHHS AMS team aims to ensure that the code remains in line with current clinical recommendations and to monitor usage via audit on an ongoing basis.

“We hope to maintain the tool as required to ensure availability to our clinicians for many years to come!” Ms Kilfoyle said.