Safety Hints

Caution about injections: It is quite dangerous to insert the syringe
needle in the wrong place and inject the solution into an artery by mistake.
A good habit to develop when giving any type of injection is to
draw back on the syringe (i.e., pull back on the plunger) before injecting the
solution. If you draw back and get blood, reposition the needle and
draw back again. This technique prevents an accidental intra-arterial
injection, which can cause serious complications. If you draw back
blood with the initial insertion, you have not created a major problem.
Because you are using a small needle, you should not do significant
damage to the blood vessel, but you may need to hold pressure over
the area for a few minutes to decrease bruising.
Caution about maximal safe dosage: Be aware of how much you are
injecting to avoid exceeding the safe doses. Average-sized wounds (up
to 4–5 cm) usually present no problem, but it is easy to forget about
dosage concerns when you are working on larger wounds. All anesthetic
agents have systemic as well as local effects. The safe dosage is
based on the total weight of the patient (thus the maximal doses are
given as mg of agent/kg of patient body weight). Overdose can lead to
seizures and even cardiovascular collapse or death due to the myocardial
depressant and vasodilator effects of these agents.