There are two major groups of local
anaesthetics: esters and amines.
- Esters : procaine (Novocaine), and tetracaine (Pontocaine)
- Amines: lidocaine (Xylocaine) and bupivacaine (Marcaine).
If a past allergy is reported, an anesthetic from another class
can be used. Most often, however, the allergy is to the preservative
used in the lidocaine multidose vials. Therefore, one option is to
use a single-dose lidocaine preparation that does not contain preservatives.
For routine Emergency room use, a mixture of lidocaine 1%, with
or without epinephrine 1/100,000 parts, is recommended. For regional
nerve blocks, a 2% solution is used. The lidocaine 2% solution can
be combined with equal parts of the Marcaine 0.25% solution to obtain
relatively quick, yet longer lasting anaesthesia. The anaesthetic
effect of lidocaine lasts less than an hour, but as long as two hours
if the epinephrine containing preparation is used. Marcaine’s
effect lasts from 12-24 hours. This would be important, for example,
in the case of a distal digit amputation, where longer-term anaesthesia
is desired. Some patients continue to experience considerable pain
even after simple suturing, and Marcaine could significantly reduce
Epinephrine is commonly used as an adjuvant to reduce bleeding and
slow anaesthetic absorption systemically. A noticeable decrease in
wound bleeding will be noted in about seven minutes. Epinephrine
should be avoided in those patients with vasospastic disorders, those
with crush or circumferential extremity injuries, or those on beta-blockers.
The use of epinephrine in the fingers, toes or penis has classically
been contraindicated, because of its supposed propensity to cause
vasospasm in these areas.
A toxic dose of Xylocaine (lidocaine) is 3 mg per kg intravenously;
5 mg per kg when injected without epinephrine into the wound margin,
and 7 mg per kg when injected with epinephrine into the wound margin.
There is evidence that the toxic dose may actually be much higher
than usually quoted. The toxicity of Marcaine is one-quarter that
of lidocaine, on a weight to weight basis.
Prior to the administration of local anaesthetics, check the sensory
and motor nerve response, and for allergy (very rare). The pediatric
literature supports the use of a topical anesthetic such as LET (a
combination of lidocaine, epinephrine and tetracaine) prior to needle
infiltration to reduce the pain. Slow injection by a small needle
(such as a 25, 27 or 30 Gauge) will reduce the pain of infiltration.
Adverse reactions to local anaesthetics may take several forms.
Adverse Reactions to Local Anaesthetics
abdominal and uterine cramps
(>3mg /kg IV, >5 mg/kg without epinephrine,
> 7 mg/kg with epinephrine)
||IV leak (? From regional blocks?)
CNS excitation, depression
||rare to amides
uncommon to esters
If there is doubt about allergy, in minor cases, plain normal saline
can be injected into the wound margin to stretch the skin, thereby
affording some degree of anaesthesia.
Malignant hyperthermia is now considered NOT to be precipitated
by the use of lidocaine. Traditionally, in this setting, an ester
has been utilised.
Tetanus prophylaxis - Tetanus vaccination
The tetanus disease itself is a serious one but relatively rare in Canada.
An identifiable acute injury occurs in the majority of cases (70%).
Puncture wounds and lacerations account for most cases. Interestingly,
approximately one-half of these injuries occurred indoors. Only a small
percentage of cases occur in previously properly “immunised” patients.
The incubation period is from two days to two months.
Tetanus vaccines must be administered intramuscularly. The anterolateral
thigh is recommended in infants and the deltoid muscle in older children
and adults. These adsorbed vaccines should not be administered subcutaneously
as sterile abscess can form.
Since 1982, all school children in Ontario are required by law to
be immunised. As of 1987, it is the law in Ontario that physicians
inform their patients of the risks and benefits of immunisation. Adverse
reactions to primary immunisation with tetanus toxoid are rare. The
booster dose, however, can cause local erythema and swelling. Overuse
of tetanus vaccines can lead to Arthus type reactions, urticarial reactions,
and angioneurotic edema , and rarely, peripheral neuropathy and anaphylaxis.
Tetanus immune globulin (human) is a passive immunising agent containing
preformed antibodies. Serum sickness can occasionally occur especially
in the past when the globulin was derived from horse sera.
The decision to administer tetanus prophylaxis in the Emergency room
depends on the current immunisation status of the patient and the liability
of tetanus contamination in a given wound. In this Emergency Department,
the order for a “tetanus booster” usually means that tetanus
polio (Salk type) inactivated vaccine is administered.
Several protocols for the administration of tetanus prophylaxis are
The Canadian Immunization Guide – 6th Edition – 2002
is available at
Prophylactic oral, IM or IV antibiotics in wound care of routine
is NO evidence (based on many clinical studies and a meta-analysis)
to support the routine use of prophylactic oral, IM or IV antibiotics
to prevent wound infections after closure of routine lacerations. Antibiotics
do NOT substitute
for proper wound cleansing.
Prophylactic antibiotic treatment is, however, proven to be of value
in the treatment of animal and human bites in particular. See D. Special
Situations in Wound Care / Mammalian bites
``Use of antibiotics should be individualized based on the degree
of bacterial contamination, the presence of infection-potentiating
factors, such as soil, the mechanism of injury, and the presence or
absence of host predisposition to infection. In general, decontamination
is far more important than antibiotics. Prophylactic antibiotics should
be used in most human, dog, and cat bites, intraoral lacerations, open
fractures, and exposed joints or tendons.`` From Management of lacerations
in the emergency department. O. Capellan and J. Hollander Emergency
Medicine Clinics of North America. Volume 21, Number 1, February 2003