Discrepancies between predicted and observed rates of intravenous gentamicin delivery for neonates.
OBJECTIVE
This study aimed to investigate intravenous infusions as used in the neonatal intensive care setting, to determine the effect of gentamicin dose (mg), gentamicin concentrations (mg/ml), flow rate (ml/h) and flush volume (ml) upon the length of infusion time.


METHODS
Intravenous infusions were set up to simulate administration of gentamicin to neonates. Dextrose (10%, w/v) was administered as the primary intravenous fluid at 3.8 or 18.7 ml/h. Gentamicin doses (0.5 mg/0.2 ml, 2 mg/0.2 ml, 2.5 mg/1.0 ml, or 10 mg/1.0 ml) were delivered into the intravenous line at a T-connection using a Graseby pump over 35 min. This was followed by a saline flush of 1 or 2 ml over a further 35 min. At the end of each experiment a 2 ml 0.9% saline bolus was given. Analysis of gentamicin collected at 5-min intervals was by an HPLC method.


RESULTS
The experiment demonstrated that under the infusion conditions neonates weighing 2.5 kg would receive only 80% of the drug at 60 min, increasing to 90-95% by 75 min. In extremely low birth weight neonates (0.5 kg), even lower percentage of gentamicin recovery occurred. At 60 min only 60% of the intended gentamicin dose had been delivered and this increased to only 70% by 75 min.


CONCLUSIONS
The delivery of gentamicin administered by intravenous infusion is substantially extended in extremely low birth weight neonates. This appeared to be primarily due to the small volumes and low infusion rates used in these patients.
Sherwin
Catherine M T
CM
Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand. Catherine.Sherwin@cchmc.org
McCaffrey
Frances
F
Broadbent
Roland S
RS
Reith
David M
DM
Medlicott
Natalie J
NJ
D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000032:analysis; D016503:Drug Delivery Systems / Q000379:methods*; D005839:Gentamicins / Q000008:administration & dosage* / Q000032:analysis; D006801:Humans; D066298:In Vitro Techniques; D007262:Infusions, Intravenous / Q000379:methods*; D015931:Intensive Care, Neonatal / Q000379:methods; D013997:Time Factors
D000900:Anti-Bacterial Agents; D005839:Gentamicins