Peripheral Nerve Block: Does it Affect Pain Perception in Acute Compartment Syndrome?
A Systematic Review
Ashraf Elazab1,3*, Ahmed Abd-Elgawad2 and Mohamed Attia2
1Department of Orthopedic Surgery, Dammam Medical Complex, Dammam, Saudi Arabia
2 Department of Anesthesia, Dammam Medical Complex, Dammam, Saudi Arabia
3Department of Orthopedic Surgery, ELsenbellaween, and Mansoura international hospital, Egypt
Submission: June 23, 2018; Published: August 24, 2018
*Corresponding author:Ashraf Elazab, Department of Orthopedic Surgery, Elsenbellaween and Mansoura international hospital, Egypt
Ahmed Abd-Elgawad, Department of Anesthesia, Dammam Medical Complex, Dammam, KSA
How to cite this article:Ashraf E, Ahmed A E, Mohamed A. Peripheral Nerve Block: Does it Affect Pain Perception in Acute Compartment Syndrome? A
Systematic Review. Ortho & Rheum Open Access J 2018; 12(4): 555844. DOI: 10.19080/OROAJ.2018.12.555844.
The purpose of this study was to evaluate the effect of peripheral nerve block (PNB) on perception of pain induced by compartment syndrome (CS) in orthopedic surgery. Studies emphasized or discussed the relation between PNB and CS until March 2017 were identified in databases. Nine studies were eligible according to our selection criteria. All were case reports. Outcome including pain perception, duration to decompression and tissue necrosis were extracted from selected studies and analyzed. Pain perceived in seven out of nine cases. Decompression time range from 0 to 4 hours from pain perception and 140 min to 48 hours from operation time. Tissue necrosis was observed in three out of nine cases. In conclusion there is no evidence in the literatures supporting the assumption that PNB prevent the perception of CS pain. Accordingly, it could be considered safe for postoperative pain control in orthopedic surgery with special precautions in high-risk patients.
Keywords: Peripheral nerve block; Compartment syndrome; Delayed diagnosis; Orthopedic surgery
In modern anesthesia practice the treatment of postoperative pain is a basic human right and an essential part of perioperative care . Regional analgesic techniques were introduced aiming to minimize systemic narcotic usage which could reduce the incidence of known adverse effects including tiredness, nausea, respiratory depression, decreased intestinal motility and urinary retention . Moreover, it correlates with improved patient satisfaction, better short-term outcomes and decreased length of hospital stay [3-6]. Peripheral nerve block (PNB) as a regional analgesic technique widely used for postoperative control in orthopedic surgery. However, its efficacy for postoperative pain control raised concerns for the possible masking of the ischemic pain which is the cardinal diagnostic symptom of the compartment syndrome (CS). That may lead to delay in diagnosis with its catastrophic consequences. CS is an orthopedic emergency, which occurs when perfusion pressure of fascial compartment falls below the tissue pressure with resultant ischemia of muscles and nerves of the compartment . Irreversible tissue damage can occur within 4-6 hours after
the onset of symptoms; however, nerves are already severely damaged after 2 hours of increased compartment pressure [8,9].
Diagnosis of CS is mainly clinical. Signs and symptoms include: pain out of proportion to the injury and exacerbating by passive stretching of the involved muscles, swelling and coldness. Late signs of paraesthesia, pulslessness and paralysis follow . Pulslessness may not occur and diagnosis is assisted by invasive measuring of intra compartmental pressure. Urgent faciotomy is the definitive treatment. In the literature, some authors blamed PNB in delaying the diagnosis of CS while others defended. Our purpose was to evaluate the effect of PNB on perception of pain induced by CS in orthopedic surgery
We searched the databases including PubMed, Cochrane library, Web of Science, Embase, and reference lists of included studies using the following terms: (peripheral nerve block, regional anesthesia, CS, limb ischemia, and ischemic limb pain).
Articles discussing the effect of PNB on CS pain perception were
identified until the date of last research on 30 April 2017.
The inclusion criteria were studies which reported the
effect of PNB on compartmental syndrome pain perception in
the extremities whether it mask this pain, delay its perception
or had no effect. Outcome including pain perception, duration
to decompression and tissue necrosis. The pre-specified criteria
were used to select the eligible studies by two reviewers
(Elazab. A, Abd-Elgawad. A). Any disagreement between the two
reviewers about the selected studies was resolved by consulting
a third reviewer (Attia .M).
Among initially identified 268 articles that were searched
in the databases, 7 duplicates were excluded by using endnote
program and 224 citations were excluded after screening the
titles and abstracts. After reading full texts, 27 citations, which
did not fulfill inclusion criteria, were excluded (Table 1). Ten
studies with 10 patients fulfilled the inclusion criteria [1,11-19].
One of them  was excluded because the CS occurred outside
the blocked area. Lastly 9 cases were included in the analysis all
of them were case reports (Figure 1).
These 9 cases were published between 1997 and 2015 and
contain 6 males and 3 females with their age ranging from 4 to
75 years. Four of them were in the upper extremities and 5 were
in lower extremities.
The type of the injected local anesthetic material varied. It
was ropivacaine 7.5 % in one study, ropivacaine 0.5 % in one
study, ropivacaine 0.2 % in three studies, 0.25% bupivacaine
in one study, 0.125% levobupivacaine in one study, one study
used a combination of bupivacaine 0.5 % plus lidocaine 2%, and
in one study the type of local anesthetic was not clear (Table
2). The nerve block procedure was done preoperatively in six
cases, and immediately postoperatively in three cases. General
anesthesia was used in eight trials; however, PNB was used as a
sole anesthetic only in one trial. The types of intervention were
fasciotomy ± debridement and release of external pressure in
all cases. Table 1 summarizes the characteristics of the included
studies. Pain perceived in seven out of nine cases. Decompression
time ranged from 0 to 4 hours from pain perception and 140 min
to 48 hours from operation time. Tissue necrosis was observed
in three out of nine cases.
M; Male, F; Female, BMI: Body Mass Index, DM; Diabetes Mellitus, Dis: Disease, PCRA; Patient Controlled Regional Analgesia.
As pain is the cardinal and first alarming symptom of the CS
we searched for the perception of pain under a well-functioning
nerve block. The main findings in this study were that pain was
perceived in 7 [1,11,12, 14,15,18,19] of the 9 cases with wellfunctioning
nerve block and in 3 of them [11,14,18] ischemic
pain could be perceived under dense sensory and motor block
Table 2. In 6 of these 7 cases where pain could be perceived,
there was no any muscle necrosis or long-term neural deficit.
While in one case  some anterior and lateral musculature
of the leg was found to be non-viable and removed but without
neurological deficit. In this case fasciotomy was done 4 hours
after the patient had reported severe pain and his pain cannot be
controlled by extra dose of local anesthetic. During this period
intra compartmental pressure was measured twice (2 hrs and
3 hrs after pain) and it was high in both readings (more than 30 mm Hg) and lastly fasciotomy done after 4 hours of pain.
Of course, we cannot know exactly when the CS started but if
we assume that it was started with the first complain of pain,
it is possible to get muscle necrosis after 4 hours . So, in this
case we can consider as a case of delay in intervention rather
than a delay in diagnosis and PNB cannot be blamed in masking
the pain as it was clear that the pt can perceive pain under the
H = hour, min = minute.
In the remaining two cases [6,13,] the patients did not
complain of severe pain during the effect of nerve block. In the
first one of them  the patient was given ankle block for foot
surgery and she was pain free for about 12 hours then complained
of severe pain which was not relieved by oral analgesics and CS
was diagnosed on clinical basis and immediate fasciotomy done.
All muscles were found to be completely viable and there was no
any sequel. Because we cannot know when the CS started, there
are two possible scenarios. First, we can assume that CS started
less than 4 hours from onset of pain but pain was not perceived
until the block torn off after 12 hours (which is uncommon for
ankle block with bupivacaine 0.25% to stay for 12 hrs). The
other possible scenario assumes that the CS did not occur until
12 hours and pain perceived normally at the onset. So, in this
case we cannot conclude neither the patient can perceive pain
under nerve block nor cannot.
In the last case  the patient was a 72 years old male
with multiple co morbidities who was operated for redo open
reduction internal fixation of his left radius under axillary
brachial plexus block and presented after 24 hours from
operation with multiple swellings over the forearm and hand
with loss of sensation of his fingers. Examination revealed
edema of the forearm with multiple hemorrhagic blisters, painful
passive movement of the fingers, reduced capillary refilling and
reduced sensation over the median nerve distribution. Diagnosis
of acute CS was confirmed with intra compartmental pressure
measuring which revealed high pressure of 50 mm Hg in the
anterior compartment. In this case the patient did not complain
of pain, and pain was not the presenting complaint 24 hours
after the operation. So, we can explain missing of pain in this
case by one of three scenarios.
First assumes that the action of nerve block was prolonged for
24 hours (which is very uncommon) and masked the perception
of pain during this period. In second scenario we will assume
that pain of CS was masked by the nerve block and the reduced
perfusion caused nerve damage that prevented perception
of pain after the block had worn off. These two scenarios are
refused because the anterior compartment muscles are supplied
by both median and ulnar nerves and at presentation the median
nerve only was affected while the ulnar was well functioning
that means that it was neither blocked nor damaged and it
was supposed to carry pain sensation to be perceived. The last
possible scenario for explanation is that it was a silent CS rather
than an occult one as it is possible for a CS to occur without
intractable or even significant pain even in a fully alert patient
with sensate limb [20,21].
The mechanism by which ischemic pain is transmitted via
blocked nerve is poorly understood. It could have a different
pathway from that of surgical pain. Munk et al.  showed
that surgical pain is primarily mediated through the thin unmyelinated
C-fibers and myelinated Aδ- fibers whereas ischemic
pain primarily mediates through the thicker A-β fibers. Thus, by
using local anesthetics in dilute concentrations, it is possible to
obtain sufficient post-operative pain relief without excluding
the possibility of ischemic pain being felt by the patient. This
explanation is logic but still alone does not explain the cases
where ischemic pain was felt with the use of concentrated local anesthetics and dense motor block which means that A alpha
fibers (thicker and more resistant to block than A beta fibers)
Another explanation is that ischemic pain has a different
mechanism which is more intense and sustained than surgical
pain. Cometa et al.  showed that in ischemic tissue it is
postulated that bradykinin, serotonin, acetylcholine, adenosine,
potassium ions, and hydrogen ions are some of the substances
responsible for ischemic pain [15,22]. Tissue acidosis evidently
initiates the pain pathway as increasing levels of hydrogen ion
concentration may act on skeletal muscle nociceptors resulting
in pain impulse transmission . The hormonal markers of
inflammation and injury are thought to undergo tachyphylaxis
after nociceptor activation ; however, hydrogen ion
excitation, in particular, produces non-adapting activation of
nociceptors [23,24]. These two explanation theories of different
pathway and different mechanism can together give explanation
for transmission of pain via a blocked nerve although still not
definite; and more experimental work is needed.
There is no evidence in the literatures supporting the
assumption that PNB prevent the perception of CS pain.
Accordingly, it could be considered safe for postoperative pain
control in orthopedic surgery with special precautions in highrisk