Step-by-Step Approach to the Performance of Peripheral Nerve Blocks

By admin On Jul 9, 2023

Ovid: Peripheral Nerve Blocks: A Color Atlas

Editors: Chelly, Jacques E.

Title: Peripheral Nerve Blocks: A Color Atlas, 3rd Edition

> Table of Contents > Section I
– General Concepts > 1 – Step-by-Step Approach to the Performance of
Peripheral Nerve Blocks

Step-by-Step Approach to the Performance of Peripheral Nerve Blocks

Jacques E. Chelly

Evidence shows that peripheral nerve blocks performed in
either awake or lightly sedated adult patients prior to or after
surgery decrease the risk of complications associated with intraneural
or intrathecal injections. Evidence also suggests that the use of
peripheral nerve blocks for anesthesia reduces both operating room time
and length of hospital stay (Table 1-1).
Further, the use of peripheral nerve blocks for postoperative analgesia
has also been shown to reduce length of hospital stay. Regardless of
the timing of the performance of peripheral nerve blocks, the following
12 steps need to be considered:

Obtain a complete and detailed history
and physical examination of the patient, with special emphasis on
history of coagulopathy, anticoagulant therapy, and sensory or motor
nerve deficits, especially in the territory affected by the surgery and
the block(s).

Evaluate indications and determine the
absence of contraindications for anesthesia and/or postoperative
analgesia. The indications for peripheral nerve blocks include most
upper and lower extremity surgery. In addition, thoracic, breast,
urologic (e.g., nephrectomy, prostatectomy, cystectomy), and abdominal
surgeries (e.g., liver resection, colectomy, pancreatectomy) and hernia
repair (inguinal and umbilical) also benefit from the use of
paravertebral blocks. These blocks have been demonstrated to be as
effective as epidural. The contraindications to regional blocks are
local (e.g., infection or trauma, possible preoperative nerve damage),
surgical (e.g., nerve repair), related to the patient’s condition
(e.g., uncooperative or unwilling, presence of uncontrolled seizure
disorder), and related to the surgeon’s preference (unwilling to have
his or her patients blocked). Coagulopathy and anticoagulation therapy
at the time

P.4

of
the performance of the block, which are often cited as
contraindications to peripheral nerve block anesthesia, should be
considered a relative contraindication. Thus, most of the approaches
are based on reaching a nerve superficially using a small gauge needle
introduced into a groove and allowing compression in the area to be
applied. Coagulopathy and anticoagulation therapy at the time of the
performance of the block should be considered contraindications when
the technique requires the needle to pass into muscular masses and when
the nerve is located deep as in the case of a lumbar plexus, any
paravertebral approaches, the classic posterior Labat approach to the
sciatic nerve, or the anterior approach to the sciatic nerve. However,
the use of thromboprophylaxis following surgery is not a
contraindication to the performance of a peripheral nerve block prior
to the initiation of the thromboprophylaxis.

Table 1-1. Benefits and Potential Risks of Peripheral Blocks

Benefits	Potential Risks
During the performance of the block
Preemptive analgesia	Toxicity: cardiac, neurologic, allergic
	Pain and hematoma at the puncture site
During surgery
Avoid general anesthesia	Discomfort, hemodynamic stability
Possible active mobilization of a joint by the patient at the request of the surgeon	Risk of block failure or incomplete block Misevaluation of or changes in the surgical requirement
Postoperative period
Postoperative analgesia (several days with a continuous nerve block)	Theoretical increased risks of permanent or transient nerve damage
Reduced postoperative nausea and vomiting Early discharge

Establish which block(s) and approach and
technique (i.e., neurostimulation, ultrasound, or combined) can best
address the patient’s needs by establishing the type of surgery being
performed, and its approach and techniques. In addition, in the case of
a block performed for postoperative analgesia, it is important to
determine the expected duration of postoperative pain and the
postoperative requirement for active vs. passive mobilization. These
determinations help to differentiate between the need for a single and
the need for a continuous block.
Obtain an informed consent for the
appropriate block by providing a detailed explanation of the respective
risks and benefits of general and regional anesthesia techniques and
the need for immediate or prolonged postoperative analgesia. In
addition to the cited benefits of peripheral nerve blocks, the use of
blocks is especially advantageous in patients with American Society of
Anesthesiologists (ASA) III and IV status with compromised renal,
pulmonary (depending on the block), and cardiac function. For patients
to make an informed decision, it is essential for them to acknowledge
that a peripheral nerve block may be associated with a toxic reaction
to the administration of a local anesthetic solution, including
seizure, cardiac arrhythmias (related to intravascular injection,
increased sensitivity, or excessive concentrations of local anesthetic
solutions), and transient or permanent nerve damage (e.g., acute pain
during injection and paresthesia). The patient also needs to understand
that although the risk of nerve damage is minimized by the use of a
nerve stimulator or an ultrasound, nerve injury remains a possible
complication. Finally, the patient needs to understand that choosing a
peripheral nerve block for anesthesia does not mean that he or she must
remain awake during the surgery. It should be made very clear that
additional sedation is available.
Next, an intravenous access is secured and a nasal cannula is placed delivering O₂ 2 to 3 L/min. The patient’s vital signs are established and monitored (blood pressure and pulse oximetry).

P.5

After the patient is properly positioned,
he or she may be given some sedation including midazolam IV (start with
0.5 mg i.v. in older patients and up to 2–3 mg in anxious healthy or
young patients) and fentanyl 50 to 100 µg. The administration of these
drugs should be titrated to the need of each individual patient.
Midazolam is our drug of choice because of its relatively short
half-life, lack of hemodynamic effects, and the availability of a
specific antagonist (flumazenil) that can be administered immediately
if necessary. It is important to recognize that most blocks can easily
be performed with minimum sedation as long as a good local anesthesia
is performed. In addition, not all patients are good candidates for
blocks, especially those who are too anxious. In these patients, it is
preferable to recommend general anesthesia and a postoperative
analgesia not based on the use of a peripheral nerve block.
Choose the proper local anesthetic
mixture and concentration based on the desired onset time for the
block, the expected duration of surgery, and the need for postoperative
pain control, a need for a preferential sensory block.
Perform the block:
- Position the patient correctly.
- Identify the appropriate landmarks; mark them and/or the area scanned with the ultrasound.
- After appropriate disinfection of the
  area, perform an appropriate local anesthesia, usually with 1%
  lidocaine. The depth of the local anesthesia depends on the depth of
  the nerve (very superficial for an interscalene block, more profound
  for an anterior sciatic or lumbar plexus block).
- Under strict aseptic conditions,
  introduce the insulated needle (connected to a nerve stimulator) or
  noninsulated needle (ultrasound); locate the nerve by advancing the
  needle slowly under vision (ultrasound) or by eliciting a specific
  motor response or an electrical paresthesia (neurostimulation) in the
  appropriate territory (sensory nerve).
- Adjust the position of the needle in the
  optimum position either under vision (ultrasound) or by maintaining the
  same motor response or paresthesia with a current less than 0.5 mA
  (neurostimulation). However, it is also important to confirm that the
  motor response disappears for a current less than 0.25 mA (which
  theoretically prevents too close proximity between the needle and the
  nerve).
- After appropriate positioning of the
  needle, and negative aspiration for blood, inject 1 to 2 mL of local
  anesthetic solution. In the case of neurostimulation, this injection
  should be associated with the disappearance of the elicited motor
  response. The current delivered by the nerve stimulator is then
  increased to 2 to 3 mA, which results in the reappearance of the
  specific motor response, confirming the appropriate positioning of the
  needle. In the case of ultrasound, this injection helps to verify that
  the needle is not intraneural. The rest of the local anesthetic
  solution is injected, confirming negative aspiration of blood every 5
  mL.
After the block is performed, evaluate
the intensity of the motor and sensory block by asking the patient to
perform specific movements. In addition, ice and pinprick may be used
to evaluate the intensity of the sensory block, usually at 5-minute
intervals. If after 30 minutes the sensory block is incomplete,
consideration should be given to performing a complementary nerve block
distal to the first approach.
Before surgery, inform the surgeon of
your evaluation and of the possible need for local anesthetic
supplementation. Have the surgeon confirm your findings.
Educate the patient on:
- what to do until complete recovery of motor and sensory function.
- how to manage postoperative pain including the use of oral medication.
- how to identify symptoms of local anesthetic toxicity and other relevant side effects and complications.
P.6

In the case of ambulatory surgery, it is most
appropriate to discharge the patient with written and signed
instructions (including a pager/telephone number that the patient can
use) in case of questions or postsurgical problems.
In the case of an ambulatory procedure,
do a postoperative follow-up by telephone the next day. A second phone
call made after the expected complete recovery to document the recovery
process and to record the patient’s comments, if any, is also
recommended. If the patient complains of complications, he or she
should be asked to return to the hospital for a complete evaluation.