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April 2001
Volume 65 |
Number 4
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| Should
Regional Blockade Be Performed on Anesthetized Patients? |
Terese T. Horlocker, M.D., Chair
Annual Meeting Subcommittee on Local Anesthesia Pain
Robert A. Caplan, M.D. Committee on Patient Safety and Risk
Management
The performance of regional blockade on anesthetized patients
theoretically increases the risk of periopera-tive neurologic
complications since these patients are unable to respond to the
pain associated with needle- or catheter-induced paresthesias
or intraneural injections. There are few data in the peer-reviewed
literature, however, to support these concerns.
The recent report of a series of cervical spinal cord injuries
associated with interscalene block performed under general anesthesia
has renewed interest in this controversy.1
In each of the four cases, the patient was undergoing arthroscopic
or open rotator cuff repair. An interscalene block was performed
using a 5.0 cm insulated needle (nerve stimulator technique) in
three cases and a 3.75 cm needle that was walked off the C6 transverse
process in the remaining case. One patient moved during injection
of the local anesthetic. In all four cases, the performance of
the interscalene block was followed by total spinal anesthesia
and extensive permanent loss of bilateral cervical cord function.
Magnetic resonance imaging demonstrated syrinx at the cervical
level resulting from intracord injection of the local anesthetic
solution. Although each of the patients initiated a malpractice
suit, the actual medicolegal outcomes were not reported.
These cases present a conundrum to the anesthesiologist: Do they
exemplify bad luck or bad judgment? What actions should be taken
to reduce the occurrence of subsequent similar cases of nerve
injury? Are these recommen-dations based on objective data or
the need to just do something when catastrophic events such as
these are reported? For example, in the four cases of spinal cord
injury following interscalene block, Benumof concluded that the
presence of general anesthesia is a relative con- traindication
to interscalene block and recommended appropriate needle length
and insertion angle to minimize the risk of intracord injection.
1 A review of the patient, surgical and anesthetic
risk factors for neurologic injury are starting points to determine
under which circumstances, if any, it is safe to perform regional
techniques in a heavily sedated or anesthetized patient.
Nerve Injury Associated With Anesthesia
Cheney et al. examined the ASA Closed Claims Project database
to determine the role of nerve damage in malpractice claims filed
against anesthesia care providers. 2
Of the 4,183 claims reviewed, 670 (16 percent) were for anesthesia-related
nerve injury. The most frequent sites of injury were the ulnar
nerve (190 claims), brachial plexus (137 claims), lumbosacral
roots (105 claims) and spinal cord (84 claims). Regional anesthesia
was more frequently associated with nerve injury claims. With
the exception of spinal cord injury, the actual mechanism of injury
was not apparent for most claims. However, spinal cord and lumbosacral
nerve root injuries having identifiable etiology were associated
predominantly with a regional anesthetic technique and were related
to paresthesias during needle or catheter placement or pain during
injection of local anesthetic.
Auroy et al. performed a prospective investigation of serious
complications following regional anesthesia in 103,730 adults.
3 The authors reported 32 cardiac
arrests (seven of which were fatal) and 34 neurologic complications,
including caudal equina syndrome, radiculopathy and paraplegia.
Although not stated, it is presumed that the majority of regional
techniques were performed on conscious patients. Patients with
a persistent paresthesia/radiculopathy experienced pain during
needle placement or local anesthetic injection. In addition, the
persistent paresthesia was in the same topographical distribution
as the paresthesia elicited during the regional technique. Needle
trauma and local anesthetic toxicity were determined to be the
primary etiologies of neurologic complications. The studies by
Cheney et al. and Auroy et al. demonstrate that although serious
complications following regional anesthesia are rare, perioperative
nerve injury remains a significant source of anesthesia-related
claims. 2, 3
Furthermore, there is a tendency to assume that poor outcomes
are a result in deviation from the standard of care. Thus, the
controversy of regional techniques performed under general anesthesia
is amplified by medicolegal issues.
Regional Anesthesia in Anesthetized Children
The majority of children who undergo regional anesthetic techniques
are either heavily sedated or under general anesthesia. Therefore,
studies involving regional anesthesia in the pediatric population
are one strategy for evaluating the risk of neurologic complications
in anesthetized patients.
The largest prospective study evaluating the morbidity of regional
anesthesia in children was performed by Giaufre et al.
4 There were 24,409 regional blocks;
89 per-cent were performed under general anesthesia, 6 percent
were performed in the presence of sedation. Approximately half
of the blocks were performed in patients between 3 and 12 years
of age. Neuraxial blocks, the majority of which were caudal blocks,
accounted for 15,013 (> 60 percent) of all regional anesthetics.
However, there were 506 spinals (75 percent of which were performed
in premature infants) and 135 thoracic epidural anesthetics. Catheters
were placed in only 1,026 of 2,396 (43 percent) epidural patients.
Peripheral nerve blocks were performed in 5,251 (21 percent) cases.
The remaining 5,306 (22 percent) regional techniques involved
local infiltration/field, intra-venous regional and tracheal block.
All 23 complications occurred after neuraxial block. More than
half of the 23 reported complications (four total spinals, six
intravascular injections complicated by convulsions in two cases
and cardiac arrhythmias in two cases, and two transient paresthesias)
may have been influenced by the patient's alertness during the
performance of the neural blockade. None resulted in long-term
sequelae.
The study by Giaufre et al. suggests that the conduct of regional
anesthesia in anesthetized children carries a relatively small
risk for serious complications. This may be due to several factors.
The specific regional techniques performed on pediatric patients
are somewhat limited: typically, caudals, epidurals and field
blocks. Moreover, these blocks are often performed by specialists.
Lower con-centrations and doses of local anesthetics may be utilized
because the regional blocks are more often performed to provide
postoperative analgesia rather than intraoperative anesthesia.
In addition, small children are unlikely (or unable) to report
transient minor deficits. The lack of sequelae may be in part
due to the timing of events: Nearly all complications were noted
in the operating room or postanesthesia care unit where immediate
and skilled resuscitation was possible. Alternatively, neural
injuries may resolve more rapidly and completely in children,
resulting in a lower incidence of neurologic complications following
regional anesthetic techniques. The theory that children are at
lower risk for nerve injury is supported by the database of the
ASA Closed Claims Project, which contains a striking paucity of
claims for pediatric nerve injury (1 percent of all claims) in
comparison to claims for nerve injury in adults (16 percent of
all claims, p =0.01). A related finding that also suggests a lower
risk for chil-dren is the complete absence of claims for ulnar
neuropathy in patients less than 16 years of age. 2,
5 The decreased incidence of
neurologic complications in children, regardless of etiology,
makes extrapolation of the pediatric litera-ture to adult patients
problematic.
Regional Anesthesia in Anesthetized Adults
Although the risk of nerve injury associated with regional anesthesia
in the anesthetized adult has not been formally evaluated, several
studies have investigated the safety of neuraxial techniques for
spinal drainage or post-operative analgesia in these patients.
Grady et al. assessed the frequency of neurologic complications
in 478 patients undergoing transphenoidal surgery in conjunction
with intraoperative spinal drainage. 6
Cerebrospinal fluid drainage was accomplished with a 19-gauge
malleable needle or 16- or 20-gauge intrathecal catheters. All
malleable needles and catheters were placed after tracheal intubation.
Patients were therefore turned from the lateral to supine position
with the needle/catheter indwelling. The drains were used intraoperatively
for air injection or cerebrospinal fluid removal in 265 (55 percent)
and 202 (42 percent) patients, respectively. There were no neurologic
deficits attributable to spinal drainage. Gwirtz et al. prospectively
evaluated the safety of intrathecal opioid injection in 5,969
surgical patients. 7 In most patients
(98 percent), preserva-tive- free morphine (with or without fentanyl)
was administered at the L3-4 or L4-5 interspace at the end of
surgery while the patient was still anesthetized. A local anesthetic
was included in the injectate in 2.5 percent of patients. No neurologic
complications were noted. Abel et al. reported similar results
in 4,392 patients who underwent lumbar epidural catheter placement
under general anesthesia upon completion of abdominal or thoracic
procedures. 8 A solution containing opioids alone
was infused in 98 percent of patients. These three studies suggest
that lumbar needle and catheter placement under general anesthesia
without the injection of local anesthetic may not represent a
signifi-cant risk for neurologic complications. 6-8
Perhaps it is the combination of needle trauma and neurotoxicity
that result in nerve injury.
Peripheral and plexus blocks represent additional risk in the
anesthetized patient. The larger dose of local anesthetic given
as a single bolus over a relatively short interval increases the
risk of systemic toxicity, while heavy sedation or general anesthesia
diminishes the patient's ability to report early signs of rising
local anesthetic blood levels. In addition, although some peripheral
techniques are performed as a field block, most require that the
nerve or sheath be formally identified by eliciting a paresthesia
or nerve stimulator response or by locating an adjacent vascular
structure. The use of a nerve stimulator does not replace the
patient's ability to respond to the pain of needle trauma or intraneural
injection.
Urmey et al. performed interscalene blocks on 10 unpremedicated
patients using the paresthesia technique with an insulated needle.
9 Paresthesias were elicited with
the nerve stimulator power “off.” Upon elicitation of the paresthesia,
the nerve stimulator was turned “on” and the amperage slowly increased
to a maximum of 1.0 mA. Only one patient had a motor response,
yet all patients had surgical anesthesia after injection of the
local anesthetic. Similar results were reported using a noninsulated
needle. Since it is possible to have sensory nerve contact and
not elicit a motor response, the use of a nerve stimulator does
not prevent nerve injury in the anesthetized patient. In addition,
the elicited motor response does not distinguish between stimulation
of a peripheral nerve, a plexus, spinal root or spinal cord.1,10
Only patient feedback during injection of the local anesthetic
will provide early recognition of incorrect needle placement.
What can we definitively conclude from these large series and
case reports? First, the safety of regional anes-thesia performed
on anesthetized pediatric patients is not readily applied to adults.
Needle and catheter placement associated with administration of
neuraxial opioids at the lumbar level only appears safe. However,
techniques performed above the termination of the cord or injection
of local anesthetics, which have the potential for neurotoxicity,
should be avoided until proven safe. Few data exist on the relative
risk of peripheral techniques. It may be that the cases of intracord
injection following interscalene block reflect the number of neural
structures present within needle contact and that other plexus
of peripheral blocks are not as dangerous when performed in the
presence of heavy sedation or general anesthesia. The increasing
popularity of lower extremity techniques will no doubt be associated
with subsequent case reports of neurologic complications. We must
be honest in reporting these cases in order to evaluate the risks
and benefits.
Major complications after regional anesthetic techniques are
rare but can be devastating to the patient and the anesthesiologist.
Prevention of regional anesthesia-related complications begins
during the preoperative visit with a careful evaluation of the
patient’s medical history and an appropriate discussion of the
risks and benefits of the available anesthetic techniques. In
adult patients, administration of conscious sedation levels of
anxiolysis and injection of 1 percent lidocaine should allow most
procedures to be performed with the patient both awake and comfortable.
Although it may be customary in some settings to perform regional
anesthesia in the anesthetized patient, the anesthe-siologist
should carefully consider whether the benefits of this approach
are greater than the risk of a rare catastrophic, but potentially
preventable, outcome.
References:
1. Benumof JL. Permanent loss of cervical spinal
cord function associated with interscalene block performed under
general anesthesia. Anesthesiology. 2000; 93:1541-1544.
2. Cheney FW, Domino KB, Caplan RA, Posner KL.
Nerve injury associated with anesthesia. A closed claims analysis.
Anesthesiology. 1999; 90:1062-1069.
3. Auroy Y, Narchi P, Messiah A, et al. Serious
complica-tions related to regional anesthesia: Results of a prospective
survey in France. Anesthesiology. 1997; 87:479-486.
4. Giaufre E, Dalens B, Gombert A. Epidemiology
and morbidity of regional anesthesia in children: A one-year prospective
survey of the French-Language Society of Pediatric Anesthesiologists.
Anesth Analg. 1996; 83:904-912.
5. Morray JP, Geiduschek JM, Caplan RA, et al.
A com-parison of pediatric and adult anesthesia closed mal-practice
claims. Anesthesiology. 1993; 78(3):461-467.
6. Grady RE, Horlocker TT, Brown RD, et al. Neurologic
complications after placement of cerebrospinal fluid drainage
catheters and needles in anesthetized patients: Implications for
regional anesthesia Mayo Perioperative Outcomes Group. Anesth
Analg. 1999; 88(2):388-392.
7. Abel MD, Horlocker TT, Messick JM, Jr., et
al. Neuro-logic complications following placement of 4,392 con-secutive
epidural catheters in anesthetized patients. Reg Anesth Pain Med.
1998; 23(35):3.
8. Gwirtz KH, Young JV, Byers RS, et al. The
safety and efficacy of intrathecal opioid analgesia for acute
postop-erative pain: Seven years’ experience with 5,969 surgi-cal
patients at Indiana University Hospital. Anesth Analg. 1999; 88:599-604.
9. Urmey WF, Stanton J, O’Brien S, et al. Inability
to con-sistently elicit a motor response following sensory paresthesia
during interscalene block administration. Reg Anesth Pain Med.
1998; 23(35):7.
10. Passannante AN. Spinal anesthesia and permanent
neu-rologic deficit after interscalene block. Anesth Analg. 1996;
82:873-874.
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Terese
T. Horlocker, M.D., is Associate Professor of Anesthesiology,
Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota. |
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Robert
A. Caplan, M.D., is a Clinical Professor of Anesthesiology,
University of Washington, Staff Anesthesiologist, Virginia
Mason Medical Center, Seattle, Washington. |
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