In most emergency departments, the pace is fast and there is a constant
flow of personnel. Amid all of this activity, addressing the acute pain of a
femoral fracture may not be a top priority. However, most patients use
descriptors such as "excruciating" or "the worst pain
imaginable" when describing the acute pain that they experienced in
association with a femoral fracture. A femoral nerve block can provide
effective pain relief and can be delivered safely in the emergency department
with the appropriate equipment and education of the staff.
After the primary and secondary assessments have been completed and it has
been determined that the patient does not require an immediate trip to the
operating room, temporary stabilization of orthopaedic injuries is undertaken
in the form of splinting or traction. Concurrent with this process, the
orthopaedic surgeon should perform a careful neurovascular examination of the
extremities. Dorsalis pedis and posterior tibial pulses are palpated. The
patient should demonstrate intact anterior tibialis, extensor hallucis longus,
gastrocnemius/soleus, and toe flexor motor function as surrogates for the
integrity of the peroneal and tibial divisions of the sciatic nerve. In
addition, sensation across the dermatomes of the injured lower extremity is
assessed. These are critical first steps in deciding whether a patient is an
appropriate candidate for a femoral nerve block. Patients with abnormal
findings on the neurovascular examination or those who are unable to
participate in the examination are not candidates for a nerve block. The thigh
on the affected side should be carefully examined. Patients with a rigid,
tensely swollen thigh or those with a rapidly expanding hematoma are also not
candidates for a regional block. The history of the injury is then reviewed.
If the history is consistent with a mechanism that places the patient at high
risk for compartment syndrome (such as a crushing injury or a prolonged
extrication secondary to an entrapped lower extremity), then a femoral nerve
block is contraindicated.
Once it has been determined that the patient is a suitable candidate for a
regional block, the risks and benefits of the procedure are explained to the
patient in straightforward terms. If the patient wishes to proceed with the
block, a nerve stimulator and an injection kit are set up at the bedside
(Fig. 1). The stimulator and
injection kits should be maintained in a secure and convenient location to
ensure that the stimulator is in good working order and that the contents of
the kit have not expired. Typically, there will be a lot of activity around
the patient; it is important that all members of the trauma team be familiar
with the nerve block procedure so that efforts such as ensuring appropriate
resuscitation, blood drawing, and Foley catheter placement can be coordinated
with the administration of the block. The injection kit is opened, and the
contents are reviewed to ensure that nothing is missing
(Fig. 2) (see Appendix for a
complete list of supplies). The protective cap on the 30-mL bottle of 0.5%
bupivacaine is removed, and the expiration date is checked. The stimulator is
turned on and is checked for appropriate settings; generally, a current of 0.8
mA at 2 Hz will provide an excellent visual (patellar twitch) cue that the
needle tip is in the immediate vicinity of the femoral nerve without causing
increased pain for the patient. The stimulating needle package is opened, and
the tubing and wire are carefully removed so as to maintain sterility of the
needle. The wire from the needle is connected to the stimulator lead. Twenty
milliliters of bupivacaine are drawn into the 35-mL syringe with use of the
18-gauge needle. This needle is then removed, and the stimulator needle and
tubing are attached to the syringe. The electrocardiogram electrode is placed
on the patient's abdomen, and the grounding clip from the stimulator is
connected. The Mayo stand or table on which the equipment is placed should be
positioned immediately adjacent to the stretcher on the patient's affected
side at the level of the upper abdomen so the stimulator will be clearly
visible and the equipment will be within easy reach
(Fig. 3).
Landmarks on the patient are palpated
(Fig. 4-A). The inguinal
ligament is palpated from the anterior superior iliac spine to the pubic
tubercle. The femoral artery pulse is then located 3 to 4 cm distal to the
inguinal ligament (at the level of the inguinal crease). The femoral nerve is
lateral to the artery (Fig.
4-B), and this location is marked with a pen. A small indentation
can be made with a pen cap so that the location will be visible after sterile
preparation of the skin. The groin on the affected side is then prepared with
povidone-iodine swabsticks. The skin at the marked site is anesthetized with
the injection of approximately 0.5 mL 2% lidocaine with use of the preloaded
5-mL syringe and 25-gauge needle provided in the kit, resulting in a wheal
(Fig. 5). Sterile surgical
gloves are donned after it has been verified that all connections have been
made and the stimulator has been turned on. The stimulating needle is
withdrawn from its package and, with one hand being used to stabilize the
skin, the needle is advanced through the skin at the previously made mark. The
stimulating needle has a relatively blunt tip that requires quick, firm, and
controlled pressure in order to penetrate the skin. The needle is then slowly
advanced with the tip angled about 30° cephalad. The femoral nerve has a
proximal branch that extends to the sartorius, and this muscle often will be
the first to exhibit a twitch in synchrony with the stimulator's audio tone
and flashing indicator. The needle should continue to be advanced until the
patella is noted to twitch in concert with the cues from the stimulator. At
this point, in a patient with an average body habitus, the needle tip
typically has been advanced 2 to 3 cm and is in the immediate vicinity of the
femoral nerve. If the needle is advanced and no twitch is elicited, the needle
should be withdrawn to the level of the skin and reinserted in a slightly more
lateral direction. In order to avoid penetration of the femoral artery, the
needle should never be redirected medially toward the fingers lying over the
pulse of that vessel. Once the patellar twitch has been elicited, the needle
is stabilized in position with one hand and the syringe is picked up with the
other hand (Figs. 6-A and 6-B).
An attempt at aspiration is first made to ensure that the needle is not within
the artery (signified by the presence of easily aspirated bright red blood).
If the needle has been inadvertently advanced into the artery, it should be
withdrawn and pressure should be applied for five minutes before resuming the
procedure. Approximately 1 to 2 mL of bupivacaine are slowly injected, and the
patellar twitch should stop at this point. If the patient experiences a sudden
increase in pain or if the patellar twitch continues, the needle tip may be
within the nerve itself and should be withdrawn slightly. The remainder of the
bupivacaine is then injected in a controlled fashion over the course of sixty
seconds. Aspiration is attempted periodically to verify that the needle is not
within a blood vessel, and the patient is asked about the development of
circumoral numbness, tinnitus, or blurred vision. Any of these symptoms may
indicate an intravascular injection, and the procedure is discontinued if this
occurs. After 20 mL of bupivacaine have been injected, the needle is
withdrawn, the site is checked for bleeding, and the stimulator is returned to
the appropriate location.
Most patients begin to report a diminution of pain within five minutes and
experience more than ninety minutes of effective pain relief with a
satisfactory femoral nerve block. The trauma team initially may be
apprehensive about the block being performed early in the process of the
trauma workup. Through education with an attending anesthesiologist and the
acquisition of good technical skills, junior residents at our institution have
been able to perform the block safely and efficiently and there have been no
cases in which the procedure was a rate-limiting step in the patient's
evaluation. By providing the block before transporting the patient to the
radiology department, we are able to provide effective pain relief when it is
needed most—during transfers to and from the imaging tables. The
duration of pain relief beyond ninety minutes is less well defined; however,
on the basis of the 3.5-hour half-life of bupivacaine in adults, the effect
can be expected to last throughout the duration of the trauma evaluation.
CRITICAL CONCEPTSINDICATIONS:Femoral nerve block placement in the emergency department has been shown to
be effective during the treatment of diaphyseal and/or distal femoral
fractures (both closed and open) in awake and alert adults who are able to
respond appropriately to questions and who have a normal neurovascular
examination of the injured extremity.CONTRAINDICATIONS:Intubated or obtunded patients or other patients who are not able to
respond to questions and follow commands, thereby precluding an adequate
examination.Patients with an injury history that is consistent with a crushing or other
mechanism that places them at increased risk for compartment syndrome.Patients with physical examination findings that are consistent with
compartment syndrome or impending compartment syndrome.Patients with an abnormal neurovascular examination or an unstable spine
injury.Patients with a history of a bleeding diathesis or an abnormal coagulation
profile associated with a potential risk for the development of an injection
site hematoma.PITFALLS:Inability to access the necessary equipment in a timely fashion. This
pitfall can be avoided through communication with the emergency department
staff and the trauma team before implementation of the technique and by
performing a "dry run" of the procedure in the trauma bay before
performing it in a tense environment with an actual trauma patient.Local anesthetic toxicity. This pitfall can complicate regional anesthetic
techniques secondary to two primary mechanisms. Either the administration of
an excessive amount of local anesthetic or inadvertent intravascular injection
can result in severe patient compromise. Gross overdose is readily avoided by
adhering to maximum dosing guidelines; in this case, no more than 3 mg/kg of
bupivacaine is injected into the perineural space. As an example, an 80-kg
patient may safely receive 240 mg of bupivacaine (48 mL of a 0.5% bupivacaine
solution). Note that this dose represents a true minimum toxic dose yet is
>50% greater than the dose that was delivered in our study population.
Substantially lower doses can produce toxic responses if injected
intravascularly. Intravascular injection is avoided by frequent aspiration for
blood and incremental injection with continuous monitoring for signs of
toxicity such as tinnitus, circumoral numbness, tachycardia, nystagmus, and
central nervous system excitation or depression. Current approaches to the
management of local anesthetic toxicity include the selection of less toxic
alternatives, such as ropivacaine or levobupivacaine, ultrasound guidance to
identify and avoid vascular structures, and the immediate availability of a
lipid emulsion such as Intralipid (Fresenius Kabi, Uppsala, Sweden). A lipid
emulsion acts as a lipid sink for the fat-soluble local anesthetics. Use of
this agent has resulted in markedly improved survival after local anesthetic
overdose-induced cardiac and central nervous system
dysfunction1.
Unidentified intravascular injection or gross overdose are unlikely events
when this procedure is performed while carefully following the technique as
described; neither has been reported in the peer-reviewed literature, to our
knowledge.Technical pitfalls, including equipment failure. A battery that lacks a
full charge or improper electrical connections can result in inadequate
current delivery and failure to elicit a twitch response. The former problem
can be prevented by ensuring that the stimulator is maintained with a charged
battery. The latter problem can be avoided by understanding the circuit
between the patient and the stimulator required for proper stimulator
function. Current delivery depends on a closed circuit. If the light-emitting
diode fails to flash, the electrocardiogram electrode and the wire connections
should be checked.Injection of anesthetic too far distant from the femoral nerve. As
mentioned above, the branch of the femoral nerve to the sartorius muscle tends
to arise anterior to the main trunk of the femoral nerve. The sartorius twitch
response is frequently encountered en route to the true quadriceps twitch of
the femoral nerve itself. Premature injection on the sartorius twitch will
result in an excellent block of the sartorius but a failed femoral nerve
block, which will provide inadequate anesthesia. Elicitation of a true
quadriceps twitch is essential.Prolonged paresthesias in the femoral nerve distribution. This complication
has been reported to occur very rarely, with an incidence of
0.03%2. Brull et al.
recently reported on neurological complications after regional
anesthesia3. Their
review of 13,378 femoral nerve blocks from four studies revealed fifty-two
instances of prolonged paresthesias and one case that had failed to resolve
completely after twelve months. The cause of this complication is most likely
multifactorial and may be due to direct nerve injury, compression by hematoma,
or local anesthetic toxicity. While this complication has been shown to be
rare, it should be included in the discussion of risks and benefits with the
patient.AUTHOR UPDATE:Current data suggest that the utilization of ultrasound-guided nerve
localization hastens, simplifies, and improves the accuracy of regional
anesthetic/analgesic
techniques4. This
technique has not been reported in the emergency department scenario and is
not currently used in our facility. Our results with the simple nerve
stimulator technique for nerve localization demonstrated that this method is
effective. Nevertheless, ultrasound is being used for regional anesthesia
needle guidance in the elective setting and, if it can be carried out as
efficiently in the emergency department setting as is the technique of
localization with the use of the nerve stimulator, a future study comparing
the effectiveness of the two techniques will be undertaken.
CRITICAL CONCEPTS
INDICATIONS:
Femoral nerve block placement in the emergency department has been shown to
be effective during the treatment of diaphyseal and/or distal femoral
fractures (both closed and open) in awake and alert adults who are able to
respond appropriately to questions and who have a normal neurovascular
examination of the injured extremity.
CONTRAINDICATIONS:
Intubated or obtunded patients or other patients who are not able to
respond to questions and follow commands, thereby precluding an adequate
examination.Patients with an injury history that is consistent with a crushing or other
mechanism that places them at increased risk for compartment syndrome.Patients with physical examination findings that are consistent with
compartment syndrome or impending compartment syndrome.Patients with an abnormal neurovascular examination or an unstable spine
injury.Patients with a history of a bleeding diathesis or an abnormal coagulation
profile associated with a potential risk for the development of an injection
site hematoma.
Intubated or obtunded patients or other patients who are not able to
respond to questions and follow commands, thereby precluding an adequate
examination.
Patients with an injury history that is consistent with a crushing or other
mechanism that places them at increased risk for compartment syndrome.
Patients with physical examination findings that are consistent with
compartment syndrome or impending compartment syndrome.
Patients with an abnormal neurovascular examination or an unstable spine
injury.
Patients with a history of a bleeding diathesis or an abnormal coagulation
profile associated with a potential risk for the development of an injection
site hematoma.
PITFALLS:
Inability to access the necessary equipment in a timely fashion. This
pitfall can be avoided through communication with the emergency department
staff and the trauma team before implementation of the technique and by
performing a "dry run" of the procedure in the trauma bay before
performing it in a tense environment with an actual trauma patient.Local anesthetic toxicity. This pitfall can complicate regional anesthetic
techniques secondary to two primary mechanisms. Either the administration of
an excessive amount of local anesthetic or inadvertent intravascular injection
can result in severe patient compromise. Gross overdose is readily avoided by
adhering to maximum dosing guidelines; in this case, no more than 3 mg/kg of
bupivacaine is injected into the perineural space. As an example, an 80-kg
patient may safely receive 240 mg of bupivacaine (48 mL of a 0.5% bupivacaine
solution). Note that this dose represents a true minimum toxic dose yet is
>50% greater than the dose that was delivered in our study population.
Substantially lower doses can produce toxic responses if injected
intravascularly. Intravascular injection is avoided by frequent aspiration for
blood and incremental injection with continuous monitoring for signs of
toxicity such as tinnitus, circumoral numbness, tachycardia, nystagmus, and
central nervous system excitation or depression. Current approaches to the
management of local anesthetic toxicity include the selection of less toxic
alternatives, such as ropivacaine or levobupivacaine, ultrasound guidance to
identify and avoid vascular structures, and the immediate availability of a
lipid emulsion such as Intralipid (Fresenius Kabi, Uppsala, Sweden). A lipid
emulsion acts as a lipid sink for the fat-soluble local anesthetics. Use of
this agent has resulted in markedly improved survival after local anesthetic
overdose-induced cardiac and central nervous system
dysfunction1.
Unidentified intravascular injection or gross overdose are unlikely events
when this procedure is performed while carefully following the technique as
described; neither has been reported in the peer-reviewed literature, to our
knowledge.Technical pitfalls, including equipment failure. A battery that lacks a
full charge or improper electrical connections can result in inadequate
current delivery and failure to elicit a twitch response. The former problem
can be prevented by ensuring that the stimulator is maintained with a charged
battery. The latter problem can be avoided by understanding the circuit
between the patient and the stimulator required for proper stimulator
function. Current delivery depends on a closed circuit. If the light-emitting
diode fails to flash, the electrocardiogram electrode and the wire connections
should be checked.Injection of anesthetic too far distant from the femoral nerve. As
mentioned above, the branch of the femoral nerve to the sartorius muscle tends
to arise anterior to the main trunk of the femoral nerve. The sartorius twitch
response is frequently encountered en route to the true quadriceps twitch of
the femoral nerve itself. Premature injection on the sartorius twitch will
result in an excellent block of the sartorius but a failed femoral nerve
block, which will provide inadequate anesthesia. Elicitation of a true
quadriceps twitch is essential.
Inability to access the necessary equipment in a timely fashion. This
pitfall can be avoided through communication with the emergency department
staff and the trauma team before implementation of the technique and by
performing a "dry run" of the procedure in the trauma bay before
performing it in a tense environment with an actual trauma patient.
Local anesthetic toxicity. This pitfall can complicate regional anesthetic
techniques secondary to two primary mechanisms. Either the administration of
an excessive amount of local anesthetic or inadvertent intravascular injection
can result in severe patient compromise. Gross overdose is readily avoided by
adhering to maximum dosing guidelines; in this case, no more than 3 mg/kg of
bupivacaine is injected into the perineural space. As an example, an 80-kg
patient may safely receive 240 mg of bupivacaine (48 mL of a 0.5% bupivacaine
solution). Note that this dose represents a true minimum toxic dose yet is
>50% greater than the dose that was delivered in our study population.
Substantially lower doses can produce toxic responses if injected
intravascularly. Intravascular injection is avoided by frequent aspiration for
blood and incremental injection with continuous monitoring for signs of
toxicity such as tinnitus, circumoral numbness, tachycardia, nystagmus, and
central nervous system excitation or depression. Current approaches to the
management of local anesthetic toxicity include the selection of less toxic
alternatives, such as ropivacaine or levobupivacaine, ultrasound guidance to
identify and avoid vascular structures, and the immediate availability of a
lipid emulsion such as Intralipid (Fresenius Kabi, Uppsala, Sweden). A lipid
emulsion acts as a lipid sink for the fat-soluble local anesthetics. Use of
this agent has resulted in markedly improved survival after local anesthetic
overdose-induced cardiac and central nervous system
dysfunction1.
Unidentified intravascular injection or gross overdose are unlikely events
when this procedure is performed while carefully following the technique as
described; neither has been reported in the peer-reviewed literature, to our
knowledge.
Technical pitfalls, including equipment failure. A battery that lacks a
full charge or improper electrical connections can result in inadequate
current delivery and failure to elicit a twitch response. The former problem
can be prevented by ensuring that the stimulator is maintained with a charged
battery. The latter problem can be avoided by understanding the circuit
between the patient and the stimulator required for proper stimulator
function. Current delivery depends on a closed circuit. If the light-emitting
diode fails to flash, the electrocardiogram electrode and the wire connections
should be checked.
Injection of anesthetic too far distant from the femoral nerve. As
mentioned above, the branch of the femoral nerve to the sartorius muscle tends
to arise anterior to the main trunk of the femoral nerve. The sartorius twitch
response is frequently encountered en route to the true quadriceps twitch of
the femoral nerve itself. Premature injection on the sartorius twitch will
result in an excellent block of the sartorius but a failed femoral nerve
block, which will provide inadequate anesthesia. Elicitation of a true
quadriceps twitch is essential.
Prolonged paresthesias in the femoral nerve distribution. This complication
has been reported to occur very rarely, with an incidence of
0.03%2. Brull et al.
recently reported on neurological complications after regional
anesthesia3. Their
review of 13,378 femoral nerve blocks from four studies revealed fifty-two
instances of prolonged paresthesias and one case that had failed to resolve
completely after twelve months. The cause of this complication is most likely
multifactorial and may be due to direct nerve injury, compression by hematoma,
or local anesthetic toxicity. While this complication has been shown to be
rare, it should be included in the discussion of risks and benefits with the
patient.
Prolonged paresthesias in the femoral nerve distribution. This complication
has been reported to occur very rarely, with an incidence of
0.03%2. Brull et al.
recently reported on neurological complications after regional
anesthesia3. Their
review of 13,378 femoral nerve blocks from four studies revealed fifty-two
instances of prolonged paresthesias and one case that had failed to resolve
completely after twelve months. The cause of this complication is most likely
multifactorial and may be due to direct nerve injury, compression by hematoma,
or local anesthetic toxicity. While this complication has been shown to be
rare, it should be included in the discussion of risks and benefits with the
patient.
AUTHOR UPDATE:
Current data suggest that the utilization of ultrasound-guided nerve
localization hastens, simplifies, and improves the accuracy of regional
anesthetic/analgesic
techniques4. This
technique has not been reported in the emergency department scenario and is
not currently used in our facility. Our results with the simple nerve
stimulator technique for nerve localization demonstrated that this method is
effective. Nevertheless, ultrasound is being used for regional anesthesia
needle guidance in the elective setting and, if it can be carried out as
efficiently in the emergency department setting as is the technique of
localization with the use of the nerve stimulator, a future study comparing
the effectiveness of the two techniques will be undertaken.
Peripheral nerve stimulator (STIM300; B Braun Medical, Bethlehem,
Pennsylvania).Stimuplex insulated needle (STIM-A2250; B Braun Medical, Bethlehem,
Pennsylvania).30-mL 0.5% bupivacaine (Marcaine; AstraZeneca, Wilmington, Delaware).5-mL 2% lidocaine-prefilled syringe (#3390; International Medication
Systems, South El Monte, California).35-mL MONOJECT syringe (#1183500777; Kendall, Mansfield,
Massachusetts).Povidone iodine swabsticks (three) (#10-4101; Triad Disposables, Hartland,
Wisconsin).BIOTAC Ultra 7300 series foam electrode (two) (#50007361; Kendall,
Mansfield, Massachusetts).Triflex sterile surgical gloves (#2D7255; Cardinal Health, McGaw Park,
Illinois).18-gauge 1.5-in (3.8-cm) sterile needle (#305196; BD, Franklin Lakes, New
Jersey).25-gauge 5/8-in (1.6-cm) sterile needle (#305122; BD, Franklin Lakes, New
Jersey).
Peripheral nerve stimulator (STIM300; B Braun Medical, Bethlehem,
Pennsylvania).
Stimuplex insulated needle (STIM-A2250; B Braun Medical, Bethlehem,
Pennsylvania).
30-mL 0.5% bupivacaine (Marcaine; AstraZeneca, Wilmington, Delaware).
5-mL 2% lidocaine-prefilled syringe (#3390; International Medication
Systems, South El Monte, California).
35-mL MONOJECT syringe (#1183500777; Kendall, Mansfield,
Massachusetts).
Povidone iodine swabsticks (three) (#10-4101; Triad Disposables, Hartland,
Wisconsin).
BIOTAC Ultra 7300 series foam electrode (two) (#50007361; Kendall,
Mansfield, Massachusetts).
Triflex sterile surgical gloves (#2D7255; Cardinal Health, McGaw Park,
Illinois).
18-gauge 1.5-in (3.8-cm) sterile needle (#305196; BD, Franklin Lakes, New
Jersey).
25-gauge 5/8-in (1.6-cm) sterile needle (#305122; BD, Franklin Lakes, New
Jersey).