Local anaesthetics best served warm
Local anaesthetics best served warm (Australian Doctor)
LOCAL anaesthetics are less painful when warmed to body temperature before injection, research finds.
Patients reported significantly less pain when local anaesthetics had been warmed to 37°C, compared with when injected at room temperature, researchers concluded after assessing 18 studies with a total of more than 800 patients.
The finding held true both for subcutaneous and intradermal injections, and for buffered and unbuffered anaesthetics, researchers wrote last month in the Annals of Emergency Medicine.
"There are important clinical implications to these findings," they said. "Warming of local anaesthetic solutions can be performed in almost any clinical setting in which local anaesthetics are used by utilising equipment already available for other purposes, such as thermostatically controlled water baths or incubators."
The studies included in the meta-analysis used a variety of warming approaches, such as fluid warmers, baby food warmers, a warming tray and a syringe warmer. It is unknown, however, whether simply warming the anaesthetic between a doctor's hands would suffice.
Patients in the studies were asked to rate the amount of pain they felt on injection by using a pain scale, which was measured from 0 to 100. There was an average pain reduction of 11 when anaesthetics were warmed, compared with when were left at room temperature.
An explanation for the findings could be that as temperature increases, more anaesthetic passes through cell membranes, resulting in a faster onset of effect, the researchers said. Alternatively, colder solutions might stimulate nociceptors to a greater degree than warmer solutions. Meanwhile, they dismissed concerns that local anaesthetics might degrade on heating.
Annals of Emergency Medicine 2011; 58:86-98.
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