Physico-chemical stability of Plasma-Lyte 148 and Plasma-Lyte 148 + 5% Glucose with eight common intravenous medications


This paper looks at whether dilutions of eight commonly used critical care agents (morphine, midazolam, fentanyl, ketamine, clonidine, aminophylline, salbutamol and frusemide) are stable in Plasmalyte 148 and Plasmalyte 148 + 5% Glucose, compared to dilutions in 0.9% sodium chloride or 5% Glucose.  This is important as Plasmalyte 148 is generally accepted as a safer and more efficacious maintenance solution in paediatrics compared to sodium chloride. It is widely used in paediatric practice in both the ward and critical care/theatre environments.  Current compatibility data is lacking.

Drugs were given via infusion line with a side port (“Y connectors”), and concentrations measured at 0, 2 and 24 hours.  This allowed for assessment of both compatibility of different drugs with Plasmalyte 148 +/- Glucose as a short-term infusion (assuming most drugs been cleared from the Y connector site at 2 hours) and also stability of longer term infusions used in intensive care (24 hour measurement). A  concentration change of <5% defined as chemically stable.

This study demonstrated that seven of the eight studied drugs were chemically stable when mixed with Plasmalyte 148 +/- Glucose.  The exception, midazolam, showed >10% increase in concentration at 2 and 24 hrs.  Comment is made that this is chemically implausible and may be explained by an unaccounted for experimental error.  Again, all drugs save midazolam were chemically and physically compatible (at usual clinical concentrations) at the Y connector with an infusion of Plasmalyte 148 +/- 5% Glucose.

In addition, the pH of all infusions mixed with Plasmalyte 148 +/- Glucose was 5 – 9 and therefore deemed safe to be administered through a peripheral vein.  Indeed, the buffering capacity of Plasmalyte makes it less likely to case pH induced thrombophlebitis than standard fluids (0.9% sodium chloride or 5% glucose).

Take home message

Diluting morphine, aminophylline, salbutamol, clonidine, ketamine, fentanyl and frusemide with Plasmalyte 148 +/- 5% glucose is a physiochemically safe and stable option. It may be less likely to cause pH induced thromobophlebitis than dilutions in 0.9% sodium chloride or 5% glucose. This study suggests midazolam is not stable in dilution with plasmalyte 148 =/- 5% glucose (reason unclear) and is not recommended.

Reviewed by: Dr Rachael Chapman