Choice of Anesthesia for Outpatient
Knee Arthroscopy
William F. Urmey, M.D.
Assistant Professor of Clinical Anesthesiology
Hospital for Special Surgery
Weil Medical College of Cornell University
New York, NY, USA
Introduction
Regional anesthesia offers many advantages
over general anesthesia for the outpatient, as listed in Table 1.
Table 1:
Advantages of Regional Anesthesia Compared to General Anesthesia
Early discharge for outpatients
Smooth transition to pain control
Increased blood flow to extremity (ies)
Theoretical decrease in reflex sympathetic
dystrophy
Decreased nausea/vomiting
Decreased drowsiness
Decreased urinary retention
Avoids endotracheal intubation
Lower admission rates
Regional
anesthetics promote a smooth transition to postoperative analgesia by
regional, parenteral, or oral administration of analgesics. Some regional anesthetic techniques, e.g. femoral nerve blocks,
can provide long lasting postoperative analgesia while allowing the
patient to return home with adequate function.
Although
many of the advantages of regional anesthesia for outpatient knee arthroscopy
are obvious, there has been an inadequate number of prospective, controlled
studies published to date. This is in part due to the fact that the outpatient
is a relatively new concept. With
the rapid expansion of outpatient surgery and ambulatory centers, we
are just beginning to generate the necessary clinical and academic experience
to begin defining the relevant issues for study.
The goals of outpatient anesthesia for
knee arthroscopy are listed below (Table 2).
Table 2:
Goals of Outpatient Anesthesia
Excellent surgical anesthesia
Smooth transition to PACU/pain control
Minimal side effects (sedation, nausea,
vomiting, urinary retention,
Very low admission rate
Very low complication rate
Quick onset and offset of anesthesia
Regional anesthesia has been shown to
be extremely safe in several recent large-scale outcome studies.1-4 The etiologies
of most of the small number of complications that occurred in these
studies are now understood. Therefore
regional anesthesia is the safest alternative for knee arthroscopy.
Auroy, et al.2 studied 103,730 regional anesthetics.
Only 34 serious neurological deficits occurred in this extremely
large study group. However,
if examined more closely, 21/34 (62%) of the complications were associated
with pain or paresthesia upon injection.
Of the remaining 13 complications, 12 were from spinal anesthetics. Of these 12, 9 were associated with 5% intrathecal
lidocaine. In closed claim study
by Aromaa, et al.1 only 7 claims for long-lasting neurological
deficits resulted from 550,000 spinal and 170,000 epidural anesthetics.
The choice of anesthetic for the outpatient
is very important. This was
accented in a recent prospective, multivariate outcome study by Pavlin,
et al.5 These investigators found that "the anesthetic
technique was the most important determinant of discharge time (p =
0.001)". The major reasons
for prolongation of recovery times are listed in Table 3. Pain was the most common reason for prolonged recovery in this study.
Table 3.
Reasons for Duration of Recovery ³50 Minutes in Phase 1 and ³70 Minutes in Phase 2 (From Pavlin
et al. Anesth Analg 1998;87:816-26.)
Phase 1 Recovery Phase 2 Recovery
(Post anesthesia care unit) (Dedicated outpatient recovery unit)
|
Reasons |
Primary |
Contributing |
Primary |
Contributing
reasons |
|
Pain |
16 |
23 |
14 |
19 |
|
Drowsy |
14 |
23 |
10 |
15 |
|
Nausea/vomiting |
4 |
11 |
10 |
15 |
|
Block
unresolved |
6 |
6 |
7 |
9 |
|
Inadequate
ventilation |
5 |
7 |
1 |
2 |
|
Cardiovascular
problems |
4 |
2 |
2 |
4 |
|
Shivering |
2 |
4 |
0 |
0 |
|
Other |
1 |
2 |
7 |
11 |
|
Unable
to void |
N/A |
N/A |
8 |
12 |
|
System
factors |
9 |
12 |
24 |
41 |
|
Surgical
factors |
0.3 |
0.3 |
2 |
36 |
|
Unspecified |
41 |
41 |
10 |
10 |
|
|
|
|
|
|
NA
= not applicable
aFrequency of primary reasons is expressed
as a percentage of all causes cited as the primary reason for discharge
delay. The total is 100%.
Of the patients, 408 went to Phase 1 and 293 (72%) were delayed
in Phase 1 (excluding patients who bypassed Phase 1); 617 patients went
to Phase 2, and 388 (63%) were delayed in Phase 2.
bFrequency of contributing reasons
is expressed as the percentage of all delayed patients in whom a given
reason was cited as one of the causes contributing to delay. The total is >100% becasue the causes are not mutally exclusive,
i.e. there may be more than one cause for delay. Patients who were not delayed ³50 min in Phase 1 or ³70 min in Phase 2 were not included
in the denominator for this analysis.
Phase
1 is the postanesthesia care unit.
Phase
2 is the dedicated outpatient recovery unit.
Pain in the ambulatory knee arthroscopy
patient poses a challenge to the anesthesiologist, especially with more
complex arthroscopic procedures (e.g. anterior cruciate ligament reconstruction).
Effective methods must be used to control pain in these patients.
However, this must be done without untoward side effects which
may lead to unplanned admissions.
Pain
in the day surgery patient increased nausea and vomiting, delayed discharge,
increased contact with the medical facility, and increased unanticipated
admissions according to a study by Tong and Chung.6 Orthopedic patients had the highest incidence
of severe pain of all outpatients in a study by Chung et al.7
Multimodal analgesia including non-steroidal
anti-inflammatory agents, cryotherapy, local anesthetic infusions, intraarticular
analgesia, and femoral nerve block can be very effective in eliminating
or all but eliminating pain following arthroscopic knee surgery.
Various methods of achieving anesthesia
and analgesia for knee arthroscopic surgery will be presented and discussed
below. Central neuraxial techniques,
femoral/sciatic nerve blocks, intraarticular/incisional injections,
as well as combinations of these techniques will be presented with attention
to postoperative analgesia as well as to intraoperative anesthesia.
Central
Neuraxial Anesthesia
Spinal Anesthesia
Spinal anesthesia is an excellent alternative
for knee arthroscopic procedures of a predictable duration. A single shot spinal anesthetic with a 27 gauge
pencil-point needle is relatively atraumatic. Spinal anesthesia is characterized by rapid onset, reliable duration
and offset, both desirable for the outpatient. Newer needle designs have eliminated any real
concerns with regard to post dural puncture headache (PDPH), which has
limited the use of spinal anesthesia in the past. A 25-gauge Whitacre needle is associated with a PDPH rate of about
1%8 in young patients.
A 27 pencil-point needle is presumably associated with an even
lower PDPH incidence. Distribution of intrathecal plain local anesthetic
in the subarachnoid space is ideal for knee arthroscopy as well as most
lower extremity orthopedic procedures.
Isobaric local anesthetics diminish the hemodynamic changes associated
with spinal anesthesia9 when compared to hyperbaric preparations.
The use of plain (isobaric) local anesthetics virtually eliminates
high spinal anesthesia.
Choice of Local Anesthetic for Outpatient
Spinal Anesthesia
Lidocaine has the longest track record
of safe use for outpatient spinal anesthesia.
Lidocaine has rapid onset of action, intermediate duration ,
and low toxicity in clinically recommended doses.
In a dose-response study, Urmey, et al.10 found that
40 to 60 mg lidocaine resulted in duration of motor block of 1 1/2 to
2 hours, making it an excellent choice for knee arthroscopy.
In recent years, intrathecal lidocaine
has been the focus of some controversy. For the most part, hyperbaric (especially 5% concentration) preparations
have been associated with possible neurotoxicity. Concerns regarding intrathecal lidocaine neurotoxicity
surfaced following its use during microcatheter continuous spinal anesthesia
in the late 1980's. Many reports linked lidocaine and microcatheter
use to cauda equina syndrome.11-13 This resulted in the withdrawal of microcatheters
by the United States FDA in 1992. Factors associated with cauda equina syndrome 12,13 included
1) hyperbaric solutions of lidocaine 2) microcatheter use 3) re-dosing
through the microcatheter 4) poor onset, deficient blocks, and 5) high
total lidocaine dosage (up to 300 mg!).
Most recently, reports of transient radicular
irritation (TRI) following intrathecal or epidural lidocaine use were
published.14,15 In
response to these reports, editorials were published whose authors questioned
the continued use of intrathecal lidocaine16,17. However, more recently, intrathecal mepivacaine
in hyperbaric18 and isobaric19 preparations was
found to be associated with similar (up to 30%) incidences of TRI. Pollock, et al.20and Hampl, et al.21
have found similar incidences of TRI with 2% lidocaine as with 5% lidocaine.
Nevertheless, the author advocates the use of the lower effective
concentrations of lidocaine. Studies have shown that 1.5% or 2% hyperbaric
lidocaine resulted in no difference or faster recovery postoperatively19-21.
when compared to 5% hyperbaric drug.
Recent data from Hampl, et al.22
showed that 2% prilocaine was associated with a 4% incidence of TRI
compared to the 29% associated with 2% lidocaine.
Whereas, it is important to look for
improved alternative drugs and solutions, we must keep in mind the unique
large clinical experience and unparalleled safety record of lidocaine. All local anesthetics have rare associated
neurotoxicity. For example,
bupivacaine was recently associated with cauda equina syndrome in an
isolated case report.23
Bupivacaine has been associated with
much smaller rates of TRI than lidocaine in several studies20-22,24. With this chemical structure in mind, there
has been renewed interest in mepivacaine as an alternative to intrathecal
lidocaine18,19,24-26. Mepivacaine
is an amide local anesthetic of intermediate duration with a chemical
structure similar to that of bupivacaine.
Mepivacaine has been safely used for
spinal anesthesia for close to 40 years, since the first report on its
intrathecal use in 196127.
The first publication of mepivacaine's use in a large scale study,
reported good outcomes with no neurological complications following
20,000 mepivacaine spinal anesthetics28.
In 1966, Lipton et al.29 compared
hyperbaric mepivacaine 4% to tetracaine 1% in a double-blind study of
vaginal deliveries. They concluded
that "the evidence...points to the superiority of mepivacaine as
a more rapidly acting as well as a more profound spinal anesthetic agent."
Henschel, et al.30 reported
on a dose-response study of intrathecal plain mepivacaine in 159 patients
with and without added epinephrine.
They found that "anesthetic duration increased with dosage
and varied from 1 to over 3 hours, averaging over 3 hours with the addition
of epinephrine".
Based on this study, Urmey began using
plain mepivacaine 1.5% or 2% five years ago and reported on its use
for intermediate-duration orthopedic procedures in 199725. Use of isobaric mepivacaine was supported by
a 1994 publication that demonstrated its favorable intrathecal distribution
in a spine model31.
Spinal mepivacaine has been more popular
in Europe, where it has been marketed for years as a 4% hyperbaric preparation.
Association of Mepivacaine with TRI
Intrathecal mepivacaine has been associated
with TRI by case report 32 and prospective studies.18,19,24 In a study of 4% hyperbaric mepivacaine, Hiller
and Rosenberg found a 30% incidence of TRI compared to 3% for bupivacaine.
The mepivacaine-associated TRI lasted up to 60 hours after anesthesia.
Salmela and Aromaa found a similar incidence
of TRI, 36.7%, with 4% mepivacaine in a study comparing it to lidocaine
and bupivacaine. Mepivacaine
was found to have the highest incidence of TRI
(36.7%) compared to 23.3% for lidocaine and 0% for bupivacaine. This was reported at the September, 1997 ESRA
Annual Meeting.
At this same meeting, Salazar, et al.
reported on the incidence of TRI associated with isobaric 2% mepivacaine
compared to 2% isobaric lidocaine in 80 patients. These investigators also found the highest incidence of TRI, 7.5%,
with mepivacaine compared to 2.5% with lidocaine.
They concluded that the "election
of 2% isobaric mepivacaine as an alternative to 2% isobaric lidocaine
for short term surgery should be questioned.
In our study, the incidence of TRI was greater in patients receiving
2% isobaric mepivacaine". They also found that duration of sensory and
motor blockade was significantly longer with mepivacaine. Following this, Liguori, et al.26
reported on a comparison of 60 mg 2% lidocaine to 45 mg 1.5% mepivacaine
in 60 patients. In this study,
the incidence of TRI was 22% with lidocaine, but TRI was not reported
with mepivacaine.
Although mepivacaine has a place in spinal
anesthesia for intermediate duration procedures, it is apparently not
the answer to eliminating TRI. It
has been associated with higher incidences of TRI than lidocaine in
2 prospective studies and a lower incidence in one study.
With similar dosage and technique, mepivacaine's duration can
be expected to be approximately 30-50% longer than that of lidocaine,
but significantly shorter than equipotent doses of bupivacaine. The discrepancy in incidences of TRI in various
investigations may have to do with the qualitative nature of the phenomenon
of TRI, patient positioning, or
possibly the milligram dosage used.
For example a recent report of 1,045 patients who received 3%
hyperbaric lidocaine 30-45 mg showed a TRI incidence of only 0.4%.33
Lumbar Epidural Anesthesia
Lumbar epidural anesthesia has been found
to have favorable properties for day surgery. In an excellent study of outpatient epidural anesthesia, Kopacz
and Mulroy found that epidural anesthesia with chloroprocaine or lidocaine
was associated with very favorable discharge times34. In a study of epidural anesthesia for outpatient
knee arthroscopy, Parness, et al35 found significant reductions
in time to discharge, incidence of nausea and vomiting, and postoperative
pain requiring treatment compared
to general anesthesia.
Improvements in spinal needles and the
development of matched needle sets for CSE anesthesia have changed how
we perform outpatient regional anesthesia.
The result has been that spinal and CSE techniques are supplanting
epidural anesthesia for outpatient orthopedic procedures. There are a few reasons for this trend. First, rapid onset of anesthesia is important
in the day surgical patient. Compared
to epidural anesthesia, intrathecal local anesthetic injection has been
found to have a significantly quicker onset of sensory and motor anesthesia
both with spinal36 and CSE37,38 techniques for
orthopedic surgery. Second,
the shortest duration local anesthetic for epidural use, chloroprocaine,
has been associated with a syndrome of severe back pain. Third, injection of a large dose of epidural local anesthetic is
necessary to perform knee surgery (up to 30 mL of 2% lidocaine). Urmey, et al. have recently found that 5 of
15 patients felt the incision after 20 mL epidural 2% lidocaine injected
through the needle at L3-4 compared to 0 of 20 patients who received
CSE anesthesia with an initial dose of 40 mg 2% lidocaine. Finally, most practitioners use local anesthetics
with added epinephrine for epidural anesthesia 34,39. Whereas the author favors this practice, this
results in much longer block offset times compared to intrathecal plain
local anesthetics, making epidural anesthesia less than ideal for the
outpatient.
Combined Spinal Epidural Anesthesia
Single injection spinal anesthesia lacks
the flexibility of a continuous technique. To compensate for this shortcoming, anesthesiologists commonly overdose
the patient to ensure adequate duration of surgical anesthesia. In a study of dose response characteristics
of lidocaine CSE anesthesia, Urmey et al.10 clearly demonstrated
a dose-dependent increase in duration.
The CSE technique allowed this study to be completed ethically,
by providing the "safety net" of an epidural catheter. This allowed prolongation of surgical anesthesia
in the small percentage of cases in which the surgery outlasted the
duration of the initial intrathecal dose of lidocaine. By reducing the initial intrathecal lidocaine
dose to 40 mg, all measured ambulatory discharge milestones were considerably
shortened.
In a study that compared epidural anesthesia
with 20 mL plain lidocaine to CSE with a 40 mg initial intrathecal dose,
CSE was associated with a faster onset and a better quality block.38 However, discharge characteristics were similar
for both patient groups.
Combined Spinal Epidural as an Alternative
to Chloroprocaine Epidural Anesthesia
2-Chloroprocaine is a short-acting ester
local anesthetic. Chloroprocaine
is characterized by properties that make it a useful drug for epidural
anesthesia in the outpatient. These
properties include 1) rapid onset 2) short duration 3) low toxicity,
and 4) rapid hydrolysis by plasma pseudocholinesterase. Chloroprocaine has been a popular choice for outpatient epidural
anesthesia based on these properties.
However, the clinical use of chloroprocaine
for regional anesthesia has not been devoid of complications or serious
side effects. Problems associated
with the drug have included neurological deficits resulting from accidental
or unrecognized intrathecal injection of 2-chloroprocaine.40-43 This was first reported in 1980.
More recently, a syndrome of severe back
pain has been associated with the use of epidural chloroprocaine. This was first reported by Fibuch and Opper
in 1988.44 Subsequent
studies have shown that chloroprocaine associated back pain was due
to the additive, ethylenediamine-tetracetic acid (EDTA), which was used
as a preservative to prolong the drug's shelf life.
The commercial preparation has undergone
a rapid evolution. Presently,
plain chloroprocaine is marketed. Hopefully,
use of the plain drug will eliminate these clinical complications.
Kopacz and Mulroy compared the use of
epidural chloroprocaine with lidocaine and mepivacaine for ambulatory
surgery.34 These authors found that epidural chloroprocaine
was characterized by a significantly shorter duration than lidocaine
or mepivacaine. Subsequently,
in a dose response study of CSE using lidocaine 2% plain, Urmey et al.
evaluated three initial intrathecal doses of lidocaine, 40 mg, 60 mg,
and 80 mg.10 In this
study of 90 patients having ambulatory knee arthroscopy, the lowest
dose of 40 mg lidocaine was found to have much shorter duration of sensory
and motor blockade. This duration was very similar to that reported
by Kopacz and Mulroy for epidural chloroprocaine. CSE with smaller dose lidocaine is an excellent
alternative continuous regional anesthetic technique. Onset and offset of anesthesia compares very
favorably to epidural chloroprocaine.
Compared to epidural anesthesia with
20 mL 2% lidocaine plain, Urmey et al.38 found that CSE with
a 40 mg initial intrathecal dose was quicker to perform (97 vs 156 sec),
had a more rapid onset (6 vs 14 min) and similar duration. In addition, the plain lidocaine epidural group, close to 40% of
patients could feel the surgical incision, necessitating epidural reinforcement
or delay of surgery. By contrast,
none of the CSE patients were aware of the surgical incision.
Femoral
Nerve Block
This technically easy and highly effective
regional anesthetic technique can be used for surgical anesthesia for
anterior lower extremity procedures or in combination with sciatic nerve
block or intraarticular local anesthesia.
Local anesthetic blockade of the femoral nerve is an excellent
technique for anesthesia of the knee.45-49
However, in a recent study, Casati and Fanelli found that femoral-sciatic
nerve block offered no advantage in terms of time to discharge when
compared to hyperbaric bupivacaine spinal anesthesia for knee arthroscopy
in the outpatient.50
Continuous techniques for blocking the
femoral nerve are increasingly popular.51 An extra or intracatheter
may be used to provide analgesia over a 2-3 day period. Similarly, Singelyn, et al. have reported a
technique for continuous three-in-one blockade of the femoral, obturator,
and lateral femoral cutaneous nerves by use of a modified Seldinger
technique.52 Use of these techniques have been largely limited
to inpatients thus far.
The femoral nerve or 3-in-1 block can
be used for surgical anesthesia with agents such as 2% lidocaine or
1.5%-2% mepivacaine in volumes of 25-30 mL.
However, most surgical procedures about the knee require that
it be combined with sciatic nerve block
or intraarticular anesthesia to ensure anesthesia of the posterior
lower extremity. However, knee
or quadriceps analgesia may be effectively achieved when femoral nerve
block is combined with small amounts of parenteral analgesics.
25-30 mL 0.25% bupivacaine or ropivacaine with added epinephrine
results in effective analgesia following knee surgery which may last
greater than 24 hours. A recent
study showed that ropivacaine 0.5% had faster onset and better anesthesia
characteristics than 0.25% bupivacaine (private communication with V.
Tagariello).
Edkin, et al. studied long acting femoral
nerve block and found that 92% of patients who underwent ACL reconstruction
required no additional analgesia.53 They found that bupivacaine 0.5% with epinephrine
resulted in a mean duration of analgesia of 29 hours. Femoral nerve block reduced parental analgesic
use by 80% in recovery room and 40% overall54 in another
study. Similar findings have
been reported by Tierney, et al.55
Femoral nerve block is simple and a safe,
effective means for providing postoperative analgesia and surgical anesthesia
for selected procedures. It
is overlooked and is greatly underutilized.
It can be a major component of a balanced regimen for knee arthroscopic
surgery when combined with anti-inflammatory, opioid, axial, intraarticular
and cryotherapeutic techniques.
Postoperative
Analgesia in the Knee Arthroscopy Patient
Long-acting femoral nerve block provides
excellent analgesia after knee surgery. It is impractical, however, for the patient having routine less
complex arthroscopic knee surgery (e.g. meniscectomy, debridement),
due to the prolonged quadriceps paralysis and need for a brace. Other analgesic modalities, used in conjunction with one another
results in synergism and can be very effective in treating pain and
allow for rapid, comfortable discharge.
Whitelaw, et al.56 reported
on the use of cryotherapy in the knee arthroscopy patient. Barber, et al.57 found that cryotherapy
lowered VAS scores, reduced oral analgesic use, and improved physical
therapy milestones in the patient following arthroscopic surgery.
Intraarticular analgesia with opiates
and local anesthetics have also been studied extensively in the knee
arthroscopy patient. In a randomized,
prospective, double-blinded study of patients following arthroscopic
knee surgery, Heard et al.58 concluded that "Our results
indicate that intraarticular injection of bupivacaine after arthroscopic
knee surgery provides prolonged analgesia but that there is no significant
prolonged analgesia provided by intraarticular morphine". Similarly, Laurent et al. 59 and Wrench et al.60
have found that intraarticular opiates were ineffective. Reuben et al.61 reported that "Patients
receiving a multimodal analgesic regimen of perioperative nonsteroidal
anti-inflammatory drugs, intraarticular bupivacaine, and external cooling
did not receive any additional analgesia from intraarticular morphine".
In a study of knee arthroscopic surgery
patients, Tetzlaff, et al.62 compared four groups with different
intraarticular injections:
Group 1: 0.25% bupivacaine/epinephrine
Group 2: 1 mg morphine/saline/epinephrine
Group 3: 025% bupivacaine/2 mg MSO4/epinephrine
Group 4: 0.25% bupivacaine/3 mg MSO4/epinephrine
They
concluded that, "bupivacaine/morphine/epinephrine provided pain
control and decreased opioid use int the PACU.
Increasing morphine dose did not improve clinical results."
Finally intrathecal clonidine has been
found to improve analgesia and decrease analgesic use.63,64
It appears that cryotherapy, nonsteroidal
anti-inflammatory drugs, and intraarticular local anesthetics possibly
with clonidine, but not intraarticular opioids all have a place in the
postoperative analgesic care of the patient following knee arthroscopic
surgery.
Conclusion
Regional anesthesia can work well for
outpatient surgical procedures. In
a previous study published in 199365, Urmey, et al. showed
that regional anesthesia could be used in 97.3% of patients (n = 907)
with excellent outcome. Recovery
times and complications were comparable to previous reports of ambulatory
anesthesia. Extremely low rates
of vomiting and urinary retention were found.
However, regional anesthesia is a technical specialty and careful,
exact technique must be practiced in treating the outpatient.
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