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We read with interest the paper by Minasian et al. They quote that pain experienced during an injection is related to the temperature of the injection and the speed of delivery of the solution. 
In their article, they have used all anaesthetics at room temperature. We have been pre-warming our anaesthetic solutions routinely for cataract surgery. We use a heat pad (Dreamland appliance...
In their article, they have used all anaesthetics at room temperature. We have been pre-warming our anaesthetic solutions routinely for cataract surgery. We use a heat pad (Dreamland appliance services model HP3, 240V,52-60W) to warm solutions to 40ºC prior to subtenon's injection. We have noted that patients found this less painful than non pre-warmed solutions.
There are reports to support that pre-warming anaesthetic solution is less painful than using solutions at room temperature.  Increasing
temperature or pH (alkalinising the anaesthetic solution) works in the
same fashion, that is, by increasing the concentration of non-ionised form
which is more lipid soluble and results in almost immediate sensory
blockade.   Though altering the pH and pre-warming the anaesthetic
solution have been tried separately, we have not encountered any study
that combines both these variables. We believe that such a study would be
worthwhile and needs to be looked at. Even if the pH of the solution
changes after warming, we do not believe that pH is a factor in reducing
pain, as confirmed by their study.
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