RPS Conference 2010, Abstracts 2010 - Royal Pharmaceutical Society

88
Neonatal gentamicin infusions– Where did the dose go?
Natalie Medlicott 1 , Simon Mathews 2 , Kwok Chiu Ho 1 , Yan Hang Ho 1 , David Reith 3 , Roland
Broadbent 3
1 School of Pharmacy, University of Otago, Dunedin, New Zealand, 2 Department of Pharmacy
and Pharmacology, University of Bath, Bath, United Kingdom, 3 Department of Women's and
Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
Focal points:
• Previously, we have reported discrepancies between the predicted gentamicin
dose and actual dose delivered through neonatal infusions 1 .
• The aim of this study was to identify potential sources of drug loss in neonatal
infusions.
• Drug loss occurred by retrograde flow up the primary infusion line if a dye
solution in water was infused into a primary fluid containing dextrose.
• Drug delivery was improved by balancing the specific gravity of the infused
solution with the primary intravenous fluid.
Introduction: Gentamicin is administered to neonates for the treatment of suspected gram
negative sepsis. When given as a 30 minute infusion into 10% dextrose, significant discrepancy
occurs between the expected dose and the actual dose delivered 1 . Lower amounts delivered
were particularly apparent in infusions for extremely low birth weight neonates (ELBW: body
weight = 500 g).
The aim of this study was to investigate potential causes of this discrepancy in neonatal
infusions. Bromophenol blue (BrB), was used as a model to investigate flow through the IV line
as it could easily be visualised.
Methods: Intravenous infusions were set-up to simulate administration of gentamicin to
neonates as previously described 1 . The primary fluid was dextrose in water (Baxter neonatal
pump). A syringe driver was used to deliver BrB (0.1% w/v in water) via the T-connection over
35 minutes followed by a 1mL normal saline flush over 35 min.
Infusion variables were: (i) primary fluid dextrose concentration (DX: 0, 5, 10 and 20%w/v), (ii)
injection volume (V: 0.4 or 1mL) and (iii) primary fluid flow rate (FR: 3.8 and 18.7mL/hour to
reflect rates for ELBW (500g) and low birth weight neonates (1.5kg)). Samples were collected
at five minute intervals over 75 minutes and BrB was measured by absorbance spectroscopy
(λ max = 592 nm).