C H A P T E R 2 7
General and local anaesthetic agents
425
run to and from the region in which the loss of pain sen-
sation or muscle paralysis is desired. These blocks are
not performed in the surgical field, but at some distance
from the field. They involve a greater area with potential
for more adverse effects. Several types of nerve blocks
are possible:
• Peripheral nerve block: blockage of the sensory and
motor aspects of a particular nerve for relief of pain
or for diagnostic purposes.
• Central nerve block: injection of anaesthetic into the
roots of the nerves in the spinal cord.
• Epidural anaesthesia: injection of the drug into the
epidural space where the nerves emerge from the
spinal cord.
• Caudal block: injection of anaesthetic into the sacral
canal, below the epidural area.
• Spinal anaesthesia: injection of anaesthetic into the
spinal subarachnoid space.
Intravenous regional local anaesthesia
Intravenous regional local anaesthesia involves carefully
draining all of the blood from the person’s arm or leg,
securing a tourniquet to prevent the anaesthetic from
entering the general circulation, and then injecting the
anaesthetic into the vein of the arm or leg. This tech-
nique is used for very specific surgical procedures.
LOCAL ANAESTHETIC AGENTS
Local anaesthetic agents (Table 27.2) are used primar-
ily to prevent the person from feeling pain for varying
periods of time after the agents have been adminis-
tered in the peripheral nervous system. In increasing
concentrations, local anaesthetics can also cause loss
of the following sensations (in this sequence): tempera-
ture, touch, proprioception (position sense) and skeletal
muscle tone. If these other aspects of nerve function are
progressively lost, recovery occurs in the reverse order
of the loss.
The local anaesthetics are very powerful nerve
blockers, and it is very important that their effects be
limited to a particular area of the body. They should
not be absorbed systemically. Systemic absorption could
produce toxic effects on the nervous system and the
heart (e.g. severe CNS depression, cardiac arrhythmias).
TABLE 27.2
DRUGS IN FOCUS Local anaesthetic agents
Drug name
Onset
Duration
Administration
Special
considerations
Esters
amethocaine (Minims
Amethocaine Eye Drops)
10–20 seconds 10–20 minutes Eye
Eye should be protected
from rubbing or
contamination
benzocaine (Cepacaine,
Cepacol)
1 minute
30–60 minutes Skin, mucous membranes Avoid tight bandages with
skin preparation
Amides
bupivacaine (Marcain)
5–20 minutes 2–7 hours
Local, epidural, dental,
caudal, subarachnoid,
sympathetic, retrobulbar
Do not use Bier Block—
deaths have occurred
cinchocaine (Proctosedyl,
Rectinol, Scheriproct)
<15 minutes
3–4 hours
Skin, mucous membranes Monitor for local reactions
levobupivacaine
(Chirocaine)
8–20 minutes
7–10 hours
Local nerve block, epidural
Use cautiously in
individuals with
cardiovascular conditions
lignocaine (EMLA,
Xylocaine, Ziagel)
5–15 minutes
30–90 minutes Caudal, epidural, spinal
cervical, dental, skin,
mucous membrane,
topical patch
Short acting, preferred for
short procedures; danger
if absorbed systemically
mepivacaine (Scandonest)
5–10 minutes
0.5 hours
Dental procedures
Advise person to take care
with hot drinks
prilocaine (Citanest)
1–15 minutes
0.5–3 hours
Nerve block, dental
Advise people not to bite
themselves
ropivacaine (Naropin)
1–5 minutes
2–6 hours
Nerve block, epidural,
caudal
Avoid rapid infusion; offers
good pain management
postop and OB
