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Letter to the editor

Editor, Dr H. Newman ('Letters' Aust Prescr 1995;18:57) states that for many years he has stressed to his trainees that 16 gauge or larger intravenous cannulae need not be used for resuscitation because the flow of a watery solution through an 18 gauge is 'only a little slower'.

It would seem that his trainees, with their intimate knowledge of Poiseuille's law (laminar flow rate alpha radius4), have been too polite to point out that a 16 gauge cannula (ID 1.30 mm 'Surflo') can in fact achieve a flow rate 3.5 times greater than that of an 18 gauge (ID 0.95 mm). Dr Newman's ability to compensate by raising the flask appears to defy Galileo's theory (velocity alpha square root height).

I suggest we observe the resuscitation protocol endorsed by the 5 learned Colleges, for the physics as well as the therapeutics!

Phillip Gray
General Practitioner
Queanbeyan, N.S.W.