Peripheral Nerve Blockade (also
see Chapter 44
and Chapter
45
)
Regional anesthetic procedures that inhibit conduction in fibers
of the peripheral nervous system can be classified
TABLE 14-5 -- Minor nerve blocks
*
|
|
Plain Solution |
Epinephrine-Containing Solution |
|
Drug |
Usual Concentration (%) |
Usual Volume (mL) |
Dosage (mg) |
Average Duration (min) |
Average Duration (min) |
|
Procaine |
2 |
5–20 |
100–400 |
15–30 |
30–60 |
|
Chloroprocaine |
2 |
5–20 |
100–400 |
15–30 |
30–60 |
|
Lidocaine |
1 |
5–20 |
50–200 |
60–120 |
120–180 |
|
Mepivacaine |
1 |
5–20 |
50–200 |
60–120 |
120–180 |
|
Prilocaine |
1 |
5–20 |
50–200 |
60–120 |
120–180 |
|
Bupivacaine |
0.25 |
5–20 |
12.5–50 |
180–360 |
240–480 |
|
Etidocaine |
0.5 |
5–20 |
25–100 |
120–240 |
180–420 |
|
Doses listed refer to 70-kg adults. Doses should be reduced
for children (see Chapter 45
)
and for patients with specific risk factors. |
*Also see
Chapter 45
.
together under the general category of peripheral nerve blockade. This form of regional
anesthesia has been arbitrarily subdivided into minor and major nerve blocks. Minor
nerve blocks are defined as procedures involving single nerve entities such as the
ulnar or radial nerve, whereas major nerve blocks involve the blockade of two or
more distinct nerves or a nerve plexus.
Most local anesthetics can be used for minor nerve blocks. The
onset of blockade is rapid with most drugs, and the choice of drug is determined
primarily by the required duration of anesthesia. A classification of the various
drugs according to their duration of action is shown in Table
14-5
. The duration of both sensory analgesia and motor blockade is prolonged
significantly when epinephrine is added to the various local anesthetic solutions.
In 1986 a technique of intrapleural regional analgesia was described
as an alternative to multiple intercostal nerve blocks.[76]
This procedure involves the administration of local anesthetic solution into the
pleural space, either by percutaneous administration or by placement through the
open chest by the surgeon. With percutaneous administration, an epidural needle
is inserted into the pleural space, usually by way of the fourth to the ninth intercostal
space. An epidural catheter is then passed into the pleural space approximately
5 to 10 cm beyond the tip of the needle and directed posteriorly, superiorly, and
medially. The needle is removed, and the local anesthetic is administered through
the catheter. The risk of pneumothorax has varied in published case series. Intrapleural
analgesia can also be administered by the surgeon through the open chest during thoracotomy.
Although interpleural analgesia appeared useful for unilateral postoperative analgesia
after cholecystectomy, mastectomy, and nephrectomy,[77]
[78]
its efficacy for post-thoracotomy pain is doubtful.
[79]
In the original case series, 22 to 30 mL of
0.5% bupivacaine with epinephrine was used in this technique; the duration of analgesia
was reported to average approximately 8 hours with a range of 4 to 24 hours. The
advantage of the technique is the ability to administer subsequent injections of
local anesthetics by catheter to provide long-lasting analgesia without subjecting
patients to repeated multiple intercostal nerve blocks. Caution is advised, however,
because this technique has been associated with extremely high
TABLE 14-6 -- Major nerve blocks
|
Drug with Epinephrine 1:200,000 |
Usual Concentration (%) |
Usual Volume (mL) |
Maximum Dose (mg) |
Usual Onset (min) |
Usual Duration (min) |
|
Lidocaine |
1–2 |
30–50 |
500 |
10–20 |
120–240 |
|
Mepivacaine |
1–1.5 |
30–50 |
500 |
10–20 |
180–300 |
|
Prilocaine |
1–2 |
30–50 |
600 |
10–20 |
180–300 |
|
Bupivacaine |
0.25–0.5 |
30–50 |
225 |
15–30 |
360–720 |
|
Etidocaine |
0.5–1.0 |
30–50 |
400 |
10–20 |
360–720 |
|
Tetracaine |
0.25–0.5 |
30–50 |
200 |
20–30 |
300–600 |
|
Doses listed refer to 70-kg adults receiving epinephrine-containing
solutions. Doses should be reduced, as detailed in Chapter
45
, for children, for patients with specific risk factors, and when non-epinephrine-containing
solutions are used. |
plasma concentrations of anesthetic and an associated risk of convulsions.[76]
Interpleural analgesia has also been used to provide analgesia for chronic pain
conditions as diverse as upper extremity complex regional pain syndromes, pancreatitis,
and cancer of the thorax and abdomen. In many centers, interpleural analgesia has
largely been supplanted by thoracic epidural analgesia for most thoracic and abdominal
procedures.
Two related approaches for unilateral somatic blockade in the
thorax are continuous extrapleural catheters (placed through the chest by the surgeon
dorsal to the parietal pleura) and continuous thoracic paravertebral somatic blockade.
One advantage of these two latter approaches over interpleural analgesia is that
very little of the administered solution leaks out of the chest into the chest tubes.
Brachial plexus blockade for upper limb surgery is the most common
major peripheral nerve block technique. A significant difference exists between
the time of onset of various drugs when these blocks are used ( Table
14-6
). In general, drugs with intermediate potency exhibit more rapid
onset than the more potent compounds do. Onset times of approximately 14 minutes
for lidocaine and mepivacaine have been reported, as opposed to approximately 23
minutes for bupivacaine.[80]
Etidocaine may be
an exception in that it produces a relatively rapid onset and a long duration of
blockade. A variety of approaches to the brachial plexus are available; the choice
of approach is dictated by several factors, including the site of surgery and the
ability of the patient to tolerate spillover
TABLE 14-7 -- Epidural anesthesia
*
|
Drug with Epinephrine 1:200,000 |
Usual Concentration (%) |
Usual Volume (mL) |
Total Dose (mg) |
Usual Onset (min) |
Usual Duration (min) |
|
Chloroprocaine |
2–3 |
15–30 |
300–900 |
5–15 |
30–90 |
|
Lidocaine |
1–2 |
15–30 |
150–500 |
5–15 |
|
|
Mepivacaine |
1–2 |
15–30 |
150–500 |
5–15 |
60–180 |
|
Prilocaine |
1–3 |
15–30 |
150–600 |
5–15 |
|
|
Bupivacaine |
0.25–0.75 |
15–30 |
37.5–225 |
10–20 |
180–300 |
|
Etidocaine |
1.0–1.5 |
15–30 |
150–300 |
5–15 |
|
|
Doses listed refer to 70-kg adults receiving epinephrine-containing
solutions. Doses should be reduced, as detailed in Chapter
45
, for children, for patients with specific risk factors, and when non-epinephrine-containing
solutions are used. |
*Also see
Chapter 43
.
to other nerves, such as the phrenic nerve. Similarly, the lumbar plexus can be
approached by several routes, including a posterior approach, an anterior perivascular
"3 in 1" approach, and an anterior fascia iliaca compartment approach.[81]
Epinephrine will prolong the duration of most local anesthetics
used for brachial plexus blockade, but it is less effective with drugs that have
intrinsically longer durations of action. The variation in duration of anesthesia
after branchial plexus blockade is also considerably greater than that observed with
other types of conduction block. For example, durations of anesthesia varying from
4 to 30 hours have been reported for bupivacaine. It would be prudent to forewarn
patients who are to be given a major nerve block about the possibility of prolonged
sensory and motor block in the involved region, particularly when drugs such as bupivacaine
and etidocaine are used. Knowledge shapes expectation and can often relieve anxiety
over unusual sensations and thus increase comfort and reduce distress.
