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Report by Ross MurphySpecialist Registrar Search checked by Simon Carley, Specialist Registrar
Clinical scenario
A 45 year old woman attends the emergency department with cellulitis. You decide to admit her for intravenous antibiotics. She becomes agitated, distressed and tearful when you explain this to her. On questioning she reveals that she is afraid of the pain of intravenous cannulation. You wonder whether a prior injection of local anaesthetic would lessen the pain of cannulation without affecting your chances of success.
Three part question
In [a patient requiring intravenous cannulation] will [a prior injection of local anaesthetic] reduce [the pain of cannulation without effecting the chance of successful cannulation]?
Search strategy
Medline 1966–07/00 using the OVID interface. [Venflon.mp OR cannula.mp or exp catheterization, peripheral OR exp infusions, intravenous OR exp injections, intravenous] AND [local anaesthetics.mp OR exp anaesthetics, local OR exp bupivicaine OR exp lidocaine OR exp procaine OR exp tetracaine] AND [pain.mp OR exp pain]. LIMIT to human and english language AND abstracts.
Search outcome
Altogether 251 papers were found of which 241 were irrelevant or of insufficient quality for inclusion. The remaining 10 papers are shown in table 6.
Comments
These studies do indicate that a prior injection of local anaesthetic lessens the pain of intravenous cannulation without affecting the chances of successful cannulation. However, none of the trials were fully blinded and most were not properly single blinded. One used a placebo control and only one reported side effects. While the results were statistically significant it is not known if they were clinically significant and few of the trials commented on the increased length of time it takes to administer anaesthetic or the cost to the health service. Although different anaesthetics were used in different studies most concentrated on 1% lignocaine. Previous studies have shown that the pain of injection of local anaesthetic is less when it is warmed and buffered with bicarbonate and in order to achieve best results this is how lignocaine should be administered prior to attempted cannulation.
Clinical bottom line
A prior injection of local anaesthetic does reduce the pain of intravenous cannulation without affecting the success.
Report by Ross MurphySpecialist Registrar Search checked by Simon Carley, Specialist Registrar