of children on significant long-term drug therapy. Apparently innocuous drug
combinations can interact and cause significant problems in children, for example, an
episode of methaemoglobinaemia has been reported in a 3-month-old child following
the application of EMLA. It was concluded from that case that prilocaine (in the
EMLA) had interacted with a sulfonamide (which can also produce
methaemoglobinaemia) that the child was already receiving.
Infection
The introduction of agents capable of producing a generalized infection, such as
human immunodeficiency virus (HIV) infection and hepatitis, is a complication which
should not occur when appropriate cross-infection control measures are employed.
5.7.2 Early localized complications
Pain
Pain resulting from local anaesthetic injections can occur at the time of the injection
due to the needle penetrating mucosa, too rapid an injection, or injection into an
inappropriate site. The sites at which injection may be painful include: (1)
intraepithelial; (2) subperiosteal; (3) into the nerve trunk; (4) intravascular. An
intraepithelial injection is uncomfortable because at the start of the injection the
solution does not disperse and this causes the tissues to balloon out. Subperiosteal
injection may produce pain both at the time of injection and postoperatively. The
initial pain is due to injection into a confined space, with the delivery of solution
causing the periosteum to be stripped from the bone. Direct contact of the nerve trunk
by the needle produces an electric-shock type of sensation and immediate anaesthesia.
This is most likely to occur in the lingual and inferior alveolar nerves during inferior
alveolar nerve blocks. Unfortunately, this complication is more common with
experienced operators as it represents good location of the needle. When it does occur
the solution should not be injected at that point but delivered after the needle has been
withdrawn slightly, thus avoiding an intraneural injection. If the needle does contact
the nerve then the patient and parent should be warned that anaesthesia of the nerve
may be prolonged. Altered sensation may last up to a few weeks in some cases.
Intravascular injection
Accidental intravascular injections can occur in children if aspiration is not
performed. Intravascular injections can cause local pain if the vessel penetrated is an
artery and arterial spasm occurs. Intravenous injections can produce systemic effects
such as tachycardia and palpitations. Intra-arterial injections are much rarer than
intravenous injections, however the effects of an intra-arterial injection can be
alarming. Such effects range from local pain and cutaneous blanching (201HFig. 5.18) to
severe intracranial problems. The reported, rare cases of hemiplegia following local
anaesthetic injections can be accounted for by rapid intra-arterial injection. This can
produce sufficient intracranial blood levels of the local anaesthetic to produce central
nervous tissue depression.
Failure of local anaesthesia