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Ambulatory Anesthesia
CURRENT STATUS OF REGIONAL ANESTHESIA FOR ADULT OUTPATIENTS
Dermot Fitzgibbon MB, BCh, FFARCSI
From the Department of Anesthesiology, University of Washington School
of Medicine, Seattle, Washington
Address reprint requests to
Dermot Fitzgibbon, MB, BCh, FFARCSI
Department of Anesthesiology
University of Washington
School of Medicine
1959 N.E. Pacific Street
Seattle, WA 98195
BENEFITS OF REGIONAL ANESTHESIA
The challenge of anesthesia for ambulatory patients is to provide for
rapid return to street readiness with the most effective postoperative
analgesia and minimal undesirable side effects. Regional anesthesia,
with its selective local action and relatively simple equipment, offers
an excellent anesthetic choice in an outpatient facility. In addition to
limiting the anesthetized area to the surgical site, the common side
effects of general anesthesia (e.g., nausea, vomiting, lethargy) are
reduced, the risks and side effects of endotracheal intubation are
minimized, patient recovery time may be decreased, and improved
analgesia is provided in the postoperative period. [7] [46]
A number of studies [51] [82] have evaluated the efficacy of ambulatory
regional anesthesia. Urmey et al [82] prospectively recorded data on
ambulatory surgery patients at an orthopedic speciality hospital where
regional anesthesia was the first-line standard care; the various types
of anesthesia administered are listed in Table 1 (Table Not Available) .
Only 4.4% of patients who had regional anesthesia required admission
compared with 12% of general anesthetics. Discharge times were similar
for general, spinal, or epidural anesthesia (average of 3 hours);
patients who had peripheral nerve blocks were discharged in
approximately 2 hours. Failure of regional anesthesia, necessitating
general anesthesia, occurred in only 1% of cases. The authors concluded
that regional anesthesia in an ambulatory center is effective in all but
a small percentage of patients. Osborne [51] evaluated outcome for 6000
consecutive procedures in a major public teaching hospital day surgery
unit. Anesthesia-related complications were more frequent with general
anesthesia (1:114) than with regional anesthesia (1:180) or local
anesthesia plus sedation
TABLE 1 -- ANESTHETIC TECHNIQUES FOR AMBULATORY ORTHOPEDIC PROCEDURES
From Urmey WF, Stanton J, Sharrock NE: Initial one-year experience of a
97.3% regional anesthesia ambulatory surgery center. Reg Anesth 18:69,
1993; © Churchill Livingstone, with permission.
(Not Available)
(1:780). Recovery with regional or local anesthesia was significantly
shorter than after general anesthesia.
Despite the potential advantages cited regional anesthesia should not be
considered universally appropriate. Factors that contribute to a
successful regional anesthetic include the appropriate selection of
patients, anesthetic technique, and local anesthetic, use of sedative
and hypnotic agents, and the skill of the anesthesiologist. Prior
screening of patients through preanesthesia testing (PAT) clinics is
very useful in determining the acceptability of patients for a regional
anesthetic. Very young or excessively anxious patients may be poor
candidates. Similarly, obese patients may present technical problems,
especially for central neuraxial blocks. Patients of American Society of
Anesthesiologists (ASA) physical status III or IV may be particularly
good candidates for ambulatory regional anesthesia compared to general
anesthesia, especially if their systemic diseases are medically stable.
SELECTION OF TECHNIQUE AND LOCAL ANESTHETIC
Outpatient regional techniques require some modification from standard
inpatient procedures. Ideally, an outpatient regional technique should
be rapid in onset and result in few if any acute or delayed
complications (e.g., pneumothorax). The additional time needed to
perform many regional blocks, as well as the time needed for the
anesthetic to take effect, is a potential drawback when procedures are
short and turnover between cases is rapid. Use of blocks that require
more time than the procedure itself to perform should be limited to
those situations where specifically indicated for medical reasons or the
patient expresses a strong preference for a specific technique. Blocks
that significantly impair the ability to ambulate and void should be
tailored to the anticipated usual duration of surgery by appropriate
selection of both local anesthetic agent and technique to minimize both
recovery and discharge time. Prolonged analgesia from a block (e.g.,
foot, arm, or hand blocks) may be beneficial in some instances,
particularly if the ability of the patient to perform various activities
is not significantly impaired; however, prolonged anesthesia may provoke
anxiety or be considered unpleasant or irritating by many patients when
it persists for many hours after hospital discharge and should be
discussed with patients before instituting such a block.
Local anesthetic agents are commonly classified according to their
relative potency and duration of action as follows: low potency and
short duration (e.g., chloroprocaine), moderate potency and duration
(e.g., lidocaine and mepivacaine), high potency and long duration (e.g.,
tetracaine, bupivacaine, and etidocaine). Selection of specific blocks
are discussed later. Selecting the appropriate local anesthetic for a
given regional anesthetic requires consideration of a number of factors,
including potency, speed of onset, duration of action of local
anesthetics, site and duration of surgery, the degree of muscle
relaxation required, and the duration of analgesia desired. Duration of
anesthesia with a given agent varies with the site of injection and
frequently with the total mass of drug injected. [70] Thus, bupivacaine
injected into the epidural space lasts approximately 2 to 3 hours
whereas the same dose injected into the brachial plexus may last 10 to
11 hours. Vasoconstrictors, such as epinephrine, are added to increase
the duration of action, provide an indication of intravascular
injection, and reduce peak serum levels of local anesthetic. The extent
to which epinephrine prolongs the duration of anesthesia depends on the
specific local anesthetic used and the site of injection.
Vasoconstrictors do not prolong the duration of action of all local
anesthetics in all situations (Table 2) (Table Not Available) .
Epinephrine prolongs the duration of action of all agents for peripheral
nerve blocks except ropivacaine. [33] It also prolongs the duration of
action of epidural chloroprocaine, lidocaine, and mepivacaine. The local
anesthetic properties of the intrinsically more potent and longer acting
agents (bupivacaine, etidocaine, tetracaine) are influenced less by the
addition of epinephrine, particularly when such agents are used
epidurally. Epinephrine does not markedly prolong the duration of motor
block by epidural bupivacaine or etidocaine; however, it does extend the
sensory block by these epidural agents. [71] The effects of epinephrine
added to agents used for spinal anesthesia are discussed later.
The optimal dose of epinephrine is one that would produce maximal
increase in the duration of a local anesthetic agent and minimal
hemodynamic effects. Kennedy et al [36] showed that a supraclavicular
brachial plexus block with 30 mL of 1.6% lidocaine has virtually no
hemodynamic effects whereas the same agent with epinephrine 1:200,000
produced a dose-related increase in cardiac rate, cardiac output, and
stroke volume that persisted for 90 minutes and decreases in peripheral
resistance and concomitant changes in mean arterial pressure that
persisted for 120 minutes. Absorbed epinephrine produces predominantly
beta-adrenergic effects with little evidence of alpha-adrenergic effects
at
TABLE 2 -- DURATION OF ACTION OF LOCAL ANESTHETICS AND EFFECT OF
EPINEPHRINE
Adapted from Ellis JS: Local anesthetics. In Kirby, Gravenstein:
Clinical Anesthesia Practice. Philadelphia, WB Saunders, 1994.
(Not Available)
doses up to 400 mug. Furthermore, epinephrine produced a dose-related
increase in mean duration of anesthesia, but only up to a concentration
of 1:200,000, above which the cardiocirculatory changes continued to
increase without any further increase in the duration of anesthesia. The
optimal dose of epinephrine in the above study was a 1:200,000 solution
or 5 mug/ml concentration. If the use of epinephrine is desirable it
should be added to the local anesthetic just before the local anesthetic
is used. The reason for this is that commercial solutions of epinephrine
containing epinephrine are buffered to a lower pH than the standard
solution of that agent in an effort to oxidation of the epinephrine.
Such acidification moves the pH farther from the pKa of that solution,
reducing the availability of the free base and the rate of diffusion of
the local anesthetic.
The speed of onset of local anesthetics is primarily related to the
agent selected and the site of injection. Thus, agents such as
chloroprocaine have a more rapid onset in the epidural space than agents
such as lidocaine and bupivacaine, and lidocaine and mepivacaine have a
more rapid onset than bupivacaine when used for peripheral nerve blocks.
Efforts to increase the speed of onset of local anesthetics by the
addition of bicarbonate have yielded contradictory results and appear to
be minimally effective.
SEDATION/ANALGESIA
Many patients undergoing surgery with local or regional anesthesia
prefer to be sedated. Small doses of short-acting drugs should be
carefully titrated. Midazolam is an excellent agent for the
moderately-anxious patient. The amnesia it produces does not correlate
with the apparent level of sedation; fully conscious patients may have
no recall of perianesthetic events. Low-dose propofol infusions also
appear to be excellent agents for intraoperative sedation. [84] Adequate
intraoperative sedation can usually be achieved with infusion rates of
25 to 100 mug/kg-1 /min-1 . When intraoperative amnesia is desired in
addition to a rapid recovery, administration of small titrated doses of
midazolam (0.5-3 mg intravenously) prior to the propofol infusion may
offer advantages over either drug alone. Many outpatients find the use
of local anesthetic techniques acceptable alternatives to both general
and regional anesthesia when adequate sedation and anxiolysis are
provided. The addition of a short-acting opioid (e.g., fentanyl,
alfentanil) is especially useful if paresthesia are sought or nerve
stimulation performed during a regional technique and obtundation is
undesirable.
UPPER EXTREMITY BLOCKS
Brachial plexus anesthesia is suitable for many upper extremity
procedures, most notably for orthopedic surgery. The axillary approach
is suitable for forearm and hand surgery whereas the interscalene
approach is useful for shoulder and more proximal upper extremity
surgeries. Intravenous regional anesthesia (Bier block) provides
adequate anesthesia of the hand and forearm for procedures of limited
duration (less than 1 hour).
Axillary Brachial Plexus Block
The axillary approach is safe and effective for outpatients. [19]
Localization of the plexus may be based on elicitation of paresthesias,
palpation of a click as
the surrounding fascial sheath is pierced, piercing the axillary artery,
or observation of motor responses to direct electrical stimulation of
nerves. Although there is some controversy regarding the most reliable
method of performing a successful axillary block, block of at least two
nerves appears to be important to improving the success rate. [42] Urban
et al [79] prospectively evaluated 508 patients who received either
interscalene or axillary brachial plexus blocks for upper extremity
surgery. They noted that major immediate complications were infrequent,
with only one mild seizure in the axillary block group and evidence of
intravascular injection in only two of the patients in the interscalene
group; however, 23% of patients in the axillary group complained of
pain, tenderness, or bruising in the axilla on the first day of surgery,
and in 2 patients the pain persisted for 2 weeks. Paresthesia occurred
in 19% of patients in the axillary group on the first postoperative day,
and 7% of patients continued to have paresthesias 2 weeks after surgery.
Similar problems of bruising and persistent numbness associated with
axillary blocks were reported by Cooper et al. [13]
Interscalene Brachial Plexus Block
Despite its common use for open shoulder surgery, interscalene block is
less widely accepted as a viable anesthetic technique in the fast
turnover setting of ambulatory surgery. [66] Its major advantage is that
it provides very effective postoperative analgesia as well as providing
satisfactory anesthesia for surgery or arthroscopy of the shoulder. The
block can also be used for surgery on the upper arm; however, the lower
part of the brachial plexus, and in particular, the medial cutaneous
nerve of the arm, intercostobrachial nerve, and the ulnar nerve are
frequently missed by this approach. In situations where anesthesia of
the medial aspect of the arm or forearm are required, additional block
of the intercostobrachial nerve or supplementation by the axillary
approach is required. The interscalene approach to the plexus is
generally unsuitable for outpatient hand surgery. D Alessio et al [16]
reported on the use of interscalene block for ambulatory surgery.
Compared with general anesthesia, the block required significantly less
total nonsurgical intraoperative time use and resulted in fewer
unplanned admissions for therapy of severe pain, sedation, or nausea and
vomiting. A failure rate of 8.7% was observed. No airway problems other
than hoarseness due to recurrent laryngeal nerve block were noted.
Postoperatively, patients who had the block proceeded more rapidly
through PACU and phase 2 recovery than comparable patients who received
general anesthesia (72 minutes ± 24 versus 102 minutes ± 40, for
regional versus general; P = 0.0001).
A number of different nerves (phrenic, recurrent laryngeal, and cervical
sympathetic) may be blocked in addition to the roots of the brachial
plexus when using the interscalene approach. Side effects commonly
observed from block of these nerves are relatively minor and well
tolerated. Involvement of the recurrent laryngeal and cervical
sympathetic nerves is rarely significant, but patients may experience
hoarseness, dysphagia, and blurred vision, and should be cautioned
against drinking or eating while hoarseness and dysphagia are present.
Reversible diaphragmatic paralysis has been reported to occur in up to
100% of cases. [83] In addition, greater than 25% mean reductions in
functional residual capacity and FEV1 have also been associated with the
block. [81] Complete or incomplete paralysis of a hemidiaphragm is
usually well-tolerated, but spirometric studies have documented altered
respiratory capacity for several hours. [83] [53] Urmey et al [80] have
listed respiratory considerations for interscalene brachial plexus
block.
LOCAL ANESTHETIC CHOICE FOR UPPER EXTREMITY BLOCK
Agents commonly used for peripheral nerve blocks, including brachial
plexus blocks, are listed in Table 3 . In general, agents of
intermediate potency exhibit a more rapid onset than the more potent
agents. Etidocaine may be an exception because it produces a block of
relatively rapid onset. [71] Mepivacaine provides a greater degree of
motor block with a longer duration of sensory anethesia than lidocaine
when used for brachial plexus block. [86] The variation in duration of
anesthesia after brachial plexus block is also considerably greater than
that observed after other types of regional anesthesia. As such, it is
prudent to forewarn patients about to receive a brachial plexus block of
the possibility of prolonged sensory and motor block, particularly when
agents such as bupivacaine and etidocaine are used. When numbness is
persistent after an upper extremity block, the patient s discharge need
not be delayed until the block has resolved. Instructions can be given
in the care of the extremity to prevent injury while sensation is
lacking. Patients should also be instructed on the use of short-acting
opioids and nonsteroidal anti-inflammatories prior to complete
resolution of the block, and on regular use thereafter if significant
postoperative pain is anticipated. Patients should be reassured that
sensation will return after discharge and be given a contact telephone
number or person if persistent beyond the expected duration.
Intravenous Regional Anesthesia
Surgical anesthesia during intravenous regional anesthesia (IVRA) is
produced by multiple and complementary mechanisms, including block of
peripheral small nerves and nerve endings (initial effect), block of
nerve trunks at a proximal site (main anesthetic component), ischemia,
and compression of nerve trunks. [63] The block can be used for various
upper extremity operations, including both soft-tissue and orthopedic
procedures, primarily in the hand and forearm. [5] It has also been used
for foot procedures with a calf tourniquet. [38] The agent most commonly
used for an upper extremity block is 0.5% lidocaine, approximately 40 mL
for upper extremity procedures, and 0.25% lidocaine 50 to 60 mL for
lower extremity procedures. Because of the risk of toxic reactions,
bupivacaine is not a suitable agent. Although chloroprocaine, because of
its extremely short serum half-life, might appear to be the ideal choice
for IVRA, it is contraindicated because it can cause phlebitis on
intravenous injection. [31] IVRA is a safe and effective way to provide
anesthesia for surgery distal to the elbow of less than 1 hour s
duration. A limiting feature of the technique is the onset of tourniquet
pain. Clinical investigations involving unmedicated unanesthetized
volunteers
TABLE 3 -- LOCAL ANESTHETICS USED FOR PERIPHERAL NERVE BLOCKS
Agent Concentration Duration (minutes)
2-Chloroprocaine 2%-3% 30-75
Lidocaine 1%-2% 50-120
Mepivacaine 1%-2% 120-300
Bupivacaine 0.25%-0.5% 300-720
Etidocaine 0.5%-0.75% 300-720
have shown that upper extremity tourniquet inflation can be tolerated
for 29 to 34 minutes in motivated, healthy subjects. [3] [15] The use of
a double tourniquet reduces but does not eliminate this problem. Onset
of analgesia and anesthesia after injection is rapid, so surgery or
manipulation may begin within 5 to 10 minutes. Lidocaine typically
produces sensory loss earliest on the radial forearm and in the first
dorsal web space. The onset of fingertip anesthesia is variable and
unpredictable, as is decrease in motor function. [78] Supplementation of
IVRA with a digital nerve block may be used if digital anesthesia is
inadequate. Normal sensation and motor power return rapidly after
tourniquet release. In some situations rapidity of recovery with loss of
analgesia may be considered a disadvantage. Infiltration of the wound
with long acting local anesthetic or peripheral nerve block by the
surgeon prior to cuff release and application of dressings may overcome
this problem in the early postoperative period. Recently, Reuben et al
[61] studied the effects of IVRA using ketolorac 60 mg and 38 mL of 0.5%
lidocaine, and noted that patients who had received ketoralac
experienced less postoperative pain (both in PACU and in the first 24
hours), and concluded that ketorolac improves IVRA with 0.5% lidocaine,
both in terms of controlling intraoperative tourniquet pain and by
diminishing postoperative pain.
ABDOMINAL, PERINEAL, AND LOWER EXTREMITY BLOCKS
Lumbar epidural anesthesia is suitable for pelvic, lower abdominal, and
lower extremity (excluding foot) surgery. The onset and quality of
sensory and motor block of the fifth lumbar and first sacral roots by
epidural anesthesia are often delayed or incomplete, with a failure of
the S1 segment sensory block in up to 46% of patients when using
lidocaine hydrochloride and epinephrine. [28] Spinal anesthesia is
superior to epidural anesthesia for lower extremity and perineal
surgery, and is useful for lower extremity, urologic, and herniorrhaphy
procedures in the ambulatory setting. Anesthesia and analgesia for mid-
and forefoot surgery can be satisfactorily achieved with peripheral
nerve blocks of the ankle and foot. Complete analgesia lasting from 10
to 25 hours after surgery has been described with ankle blocks using
bupivacaine 0.5%. [67] Details on how to perform this block are provided
by Schurman. [69]
Spinal Anesthesia
The advantages of spinal anesthesia for ambulatory surgery include ease
of administration, rapid onset, and high reliability. Potential
disadvantages include the possibility of postdural puncture headache,
urinary retention, and transient radicular irritation with lidocaine. In
North America three local anesthetics are commonly used to produce
spinal anesthesia: lidocaine, tetracaine, and bupivacaine (Table 4) .
Lidocaine produces short-to-intermediate-acting anesthesia and is
ideally suited for ambulatory regional anesthesia. The only mixture of
lidocaine currently approved by the Food and Drug Administration (FDA)
for subarachnoid use is a 5% solution made hyperbaric in 7.5% dextrose.
Recently, observations have been made that 5% hyperbaric lidocaine may
cause back and bilateral leg pain. Pinczower et al [55] described the
problem in nine patients who received hyperbaric lidocaine for spinal
anesthesia in an ambulatory setting. The dose of lidocaine ranged from
40 to 100 mg. The pain was described as either sharp or cramping with or
without associated back pain. None of these patients
TABLE 4 -- LOCAL ANESTHETICS USED FOR SPINAL ANESTHESIA
Agent Concentration Usual Dose Baricity Duration (minutes)
Lidocaine 5% in 7.5% glucose 50-100 mg Hyperbaric 45-80
2% 40-60 mg ? Hypobaric 60-100
Bupivacaine 0.75% in 8.25% glucose 9-15 mg Hyperbaric 90-240
0.5% 15 mg Isobaric 90-240
Tetracaine 0.5% in 5% glucose 10-20 mg Hyperbaric 150-300
0.5% 10-20 mg Isobaric 150-300
0.1% 7.5-10 mg Hypobaric 150-300
demonstrated objective neurologic deficits. In all cases, the symptoms
resolved fully within 1 week. Tarkkila et al [76] estimate that
approximately 10% of patients who receive hyperbaric 5% lidocaine may
experience these problems. Because of concerns of neurotoxicity relating
to either a high lidocaine or dextrose concentration, [41] [68] [76] the
manufacturing company now recommends dilution of the mixture with equal
volume of cerebrospinal fluid (CSF) prior to subarachnoid injection. A
number of studies suggest equal if not greater efficacy with lower
concentrations of lidocaine. [43] [77] Liew [43] reported on the use of
25 mg of 0.5% lidocaine for minor outpatient gynecologic procedures; 93%
of patients developed a block to T10. The mean duration of sensory block
was 32.5 minutes, and all patients had complete resolution of motor
block within 1 hour. Bupivacaine 0.75% in 8.25% dextrose is useful for
procedures lasting 2 to 2.5 hours, althought the time to spontaneous
voiding may be considerably longer. [23] Although subarachnoid
bupivacaine without a vasoconstrictor possesses an anesthetic profile
similar to tetracaine without a vasoconstrictor, differences do exist
between the drugs. The depth and duration of motor block is probably
greater with tetracaine [11] making it less desirable for outpatient
anesthesia. Bupivacaine, when compared with tetracaine, has been
reported to cause less hypotension [4] and to have a lower incidence of
lower extremity tourniquet pain. [12]
The effect of epinephrine on subarachnoid anesthesia is confusing.
Chambers [9] noted that different doses of epinephrine (100-300 mug)
added to hyperbaric lidocaine did not prolong the duration of anesthetic
block to any clinically useful effect, but time to full recovery was
delayed by 40 to 50 minutes; similar effects were observed with
subarachnoid bupivacaine. [8] Chiu [10] showed that 200 mug of
epinephrine added to 50 mg of hyperbaric lidocaine delayed the ability
to void urine by approximately 1 hour, and may delay discharge. Moore et
al [47] studied the effect of epinephrine added to lidocaine for lower
extremity surgery using the occurrence of intraoperative pain as an
end-point rather than thoracic dermatome sensory regression. The
duration of anesthesia prior to the occurrence of pain was 87 minutes ±
16 minutes for the plain lidocaine group and 128 minutes ± 23 minutes
for the lidocaine with epinephrine group. Epinephrine may have a
differential vasoconstrictive effect at different levels. Kozody et al
[40] showed that 200 mug of intrathecal epinephrine caused dural
vasoconstriction, implying that epinephrine prolongs a lidocaine block
primarily in the lumbosacral area. Thus, some prolongation of lower
extremity anesthesia may be achieved by the addition of epinephrine but
at a potential cost of delayed recovery and discharge. For routine lower
extremity or perineal surgery the author recommends the use of 50 to 60
mg 5% lidocaine in 7.5% dextrose diluted in equal volumes with CSF and
injected without epinephrine. If prolongation of lower extremity
anesthesia is necessary (greater than 60 minutes) the author
recommends the addition of 200 mug of epinephrine to lidocaine or the
use of bupivacaine 8 to 12 mg without epinephrine. Subarachnoid
tetracaine with epinephrine is not recommended for ambulatory surgery.
RECOVERY AFTER SPINAL ANESTHESIA
The generally accepted sequence of return of function after spinal block
is motor, sensory, and sympathetic; however, several studies have found
recovery of sympathetic activity may occur before complete regression of
the motor or sensory spinal block, [18] [62] although Axelsson [2]
demonstrated that motor strength in the lower extremities was restored
40 to 140 minutes on average before restoration of detrusor strength
after subarachnoid injections of bupivacaine and tetracaine. Pflug [54]
considered the ability to urinate a final indication of reversal of
sympathetic paralysis because an intact, functioning sympathetic nerve
supply to the bladder and urethra is necessary for this function.
Suitable criteria for ambulation after spinal anesthesia include normal
perianal (S4-5) pinprick sensation, plantar flexion of the foot, and
proprioception of the big toe. Discharge criteria after spinal
anesthesia include normal sensation, ability to walk, and ability to
urinate. Patients should be instructed not to lift heavy objects or
strain for 24 hours.
POSTDURAL PUNCTURE HEADACHE
The use of spinal anesthesia in younger patients for ambulatory
procedures has been discouraged by reports of a high incidence of
postdural puncture headaches (PDPH). [25] Outpatients appear to have a
higher risk of PDPH than inpatients. [25] [49] In ambulatory surgery the
possibility of PDPH assumes more prominence because it may impair the
ability to return to normal activities shortly after the procedure. For
patients planning to travel long distances soon after surgery, the
occurrence of a severe headache in a geographical area remote from the
hospital may be difficult to manage. Headache following dural puncture
is typically delayed in onset and postural in nature. PDPH presumably
occurs when a slow leak of CSF leads to contraction of the subarachnoid
space and compensatory expansion of the pain-sensitive intracerebral
veins. A variety of factors are involved in the incidence of PDPH,
including age, sex, needle diameter, and needle tip design. [26] [48]
Patients younger than 45 years old are at greater risk from a higher
incidence and severity of headache requiring treatment. Efforts have
been made to reduce the incidence of PDPH by changing the size and
design of the needle. In a meta-analysis of PDPH and spinal needle
design, Halpern [30] showed a reduction in the incidence of PDPH when
noncutting needles rather than cutting needles were used, unless the
discrepancy in needle diameter was very large. There was also a
reduction in PDPH when a small-diameter spinal needle compared with a
larger diameter needle of the same type was used. Quincke point needles
may cause persistent dural tears whereas blunt or noncutting spinal
needles (Whitacre, Sprotte) may spread dural fibers and decrease CSF
loss after dural puncture, thereby reducing the incidence of PDPH. [65]
The use of 22- and 25-gauge Quincke needles in young patients cannot be
encouraged as few studies with large patient numbers have demonstrated a
PDPH incidence under 10%. [75] Although the incidence of headache
significantly decreases with the smaller diameter needles, such as
27-gauge and 29-gauge, [22] technical difficulties may be increased.
[17] [44] The incidence of PDPH in young
patients with a 25-gauge Whitacre needle varies between 0.6% and 3.0%.
[6] [7] The incidence of headache after a 24-gauge Sprotte is probably
similar, [21] [64] although Wiesel et al [85] report an incidence of
15.2% with 24-gauge Sprotte needles in patients under 45 years old.
Needle size is less of a factor in the incidence of PDPH when noncutting
needles are used compared with Quincke-type needles. [14] [27] Smith et
al [72] recently compared the use of 25- and 27-gauge Whitacre needles
in obstetric patients and observed increased technical difficulties with
the use of the smaller gauge needles. The possibility of a lower
incidence of PDPH with the 27-gauge needle was unproven in this study.
Campbell et al [7] noted that 25-gauge Whitacre and 24-gauge Sprotte
needles were comparable with respect to ease of insertion and incidence
of PDPH, but that the Whitacre needles were substantially cheaper than
the Sprotte needles.
Based on these studies and on other currently available information, the
author recommends the routine use of 25-gauge Whitacre needles for young
patients in the ambulatory setting as the incidence of PDPH does not
appear to be significantly different with either Sprotte needles or the
smaller gauge Whitacre needles, and the cost-savings may be significant
with 25-gauge Whitacre. Although advances in needle tip design may have
reduced the incidence of PDPH, the problem still persists, and a higher
incidence should be expected in the younger outpatient age groups.
Alternative methods of regional anesthesia for outpatient anesthesia
should be considered if either the risk of PDPH is unacceptable to the
patient or access to appropriate medical care or advice is difficult
should this problem arise. If PDPH occurs and does not respond to
conservative approaches, an epidural blood patch on an outpatient basis
can be highly effective. [59] Patients are instructed to rest quietly
for 1 hour after injection of autologous blood. Patients can be
discharged but should subsequently avoid straining and should maintain
good oral fluid intake at home.
Epidural Anesthesia
Effective use of epidural local anesthesia requires an understanding of
local anesthetic potency and duration and a realistic estimate of the
length of the procedure. A variety of different agents are used for
epidural anesthesia (Table 5) . 2-Chloroprocaine (2-CP), an amino ester
local anesthetic, is a short-acting agent that allows efficient matching
of surgical procedure length and duration of epidural analgesia. It is
available in 2% and 3% concentrations, with the latter preferable for
surgical anesthesia.
Kopacz [39] noted that the duration of sensory anesthesia after epidural
injection of 20 mL of 3% 2-CP and 1.5% lidocaine was significantly
shorter (133 minutes ± 28 minutes for 2-CP, 182 minutes ± 38 minutes
for lidocaine) than
TABLE 5 -- LOCAL ANESTHETIC DRUGS USEFUL FOR OUTPATIENT EPIDURAL
ANESTHESIA
Drug Concentration Typical Volume (mL) Duration (minutes) *
Chloroprocaine 2%-3% 15-24 30-90
Lidocaine 1.5%-2% 15-24 60-90
Mepivacaine 1.5%-2% 15-24 90-120
*Solution contains 1:200,000 concentration of epinephrine.
after 1.5% mepivacaine (247 minutes ± 42 minutes). In addition,
discharge times were significantly shorter for 2-CP (269 minutes ± 62
minutes) and lidocaine (284 minutes ± 62 minutes) than for mepivacaine
(357 minutes ± 71 minutes). Each of these solutions contained 5 mug/mL
epinephrine. Deck et al [20] compared the effects of epidural 3% 2-CP
and 1.5% lidocaine without epinephrine. Patients receiving 2-CP had
significantly faster times to block resolution, ambulation, and
discharge than those receiving lidocaine. Patients receiving 2-CP had
resolution of block (120 minutes ± 15 minutes versus 190 minutes ± 44
minutes) and were discharged sooner (127 minutes ± 16.8 minutes versus
195 minutes ± 43.8 minutes) than patients in the lidocaine group. The
implication of these studies are that moderate epidural doses of 3% 2-CP
without epinephrine may be the epidural solution of choice for
ambulatory epidural anesthesia.
Prolonged and sometimes permanent neurologic deficits have been reported
after inadvertent subarachnoid injections of 2-CP during attempted
epidural anesthesia. [59] The combination of a low pH and the presence
of sodium bisulfite may have been responsible for the neurotoxic
reactions. [29] 2-CP itself does not appear to be neurotoxic. Partly
because of these reports, the preparation of the drug has undergone an
evolution resulting in 2-CP preparations with different additives.
Earlier preparations of the drug contained methylparaben. In 1987, a new
preparation that was free of both methylparaben and sodium bisulfite was
marketed under the brand name Nesacaine-MPF (Nesacaine methylparaben
free, Astra Pharmaceutical, Westborough, MA); however, this preparation
contains disodium ethylenetetraacetic acid (EDTA), which has been
associated with a syndrome of prolonged backache following regression of
epidural anesthesia with Nesacaine-MPF. [24] [50]
2-CHLOROPROCAINE BACK PAIN
In 1989, Fibuch [24] published the first of several reports describing a
syndrome of prolonged backache following regression of epidural
anesthetic with EDTA containing Nesacaine-MPF. Orkin [50] reported a 40%
incidence of backache following 2-CP epidural anesthesia in ambulatory
patients. Stevens [73] found a 100% incidence of back pain after large
doses of 2-CP. The pain typically begins during regression of sensory
anesthesia. It is described as being deep, aching, or burning in
character. The pain is poorly localized to the lumbar region and severe
in intensity. It is not easily treated with conventional analgesics and
may last 24 hours or more. It has not been reported to cause either a
chronic pain syndrome or any lasting neurologic sequelae. This syndrome
of severe back pain was not reported prior to the addition of EDTA;
therefore, EDTA has been the leading suspect in the cause of back pain.
One possibility is that EDTA leaking into the lumbar musculature may
result in localized hypocalcemia and tetanus. [24] Other possible
contributing factors include the low pH (2.5-3.5) of 2-CP as 2-CP is
more acidic than the other commonly used local anesthetics. Stevens [74]
concluded that large doses (> 40 mL) of 2-CP that contains EDTA resulted
in a high incidence of back pain. Use of a lower volume (< 25 mL)
significantly reduced the incidence of back pain. Treatment with
epidural fentanyl (100 mug) has provided prompt relief. [73]
If 2-CP is planned for epidural use, a block might prudently first be
established with 1.5% lidocaine (to exclude inadvertent subarachnoid
injection and avoid potential neurotoxic effects from 2-CP) and then
maintained with 2-CP. For short procedures, epinephrine should be
avoided. The minimal volume of 2-CP necessary should be used. The use of
epidural bupivacaine is not recommended for ambulatory surgery due to
its unnecessarily prolonged duration.
KNEE SURGERY
Arthroscopic procedures on the knee joint form a large proportion of
outpatient surgical procedures. The surgery may be solely diagnostic,
and in this situation may last less than 30 minutes. Therapeutic
procedures (e.g., meniscectomy) may last 2 to 3 hours. The knee is
innervated by L3, L4, and L5 nerve roots anteriorly and the first two
sacral roots posteriorly. A number of different regional anesthetic
techniques have been used for knee surgery (Table 6) . Randel [57]
considered epidural anesthesia superior to spinal or general anesthesia
for outpatient knee arthroscopy. Patel et al [52] noted favorable
operating conditions and good postoperative analgesia with a 3-in-1
femoral nerve block, a lateral cutaneous nerve block of thigh, and 10 mL
0.25% bupivacaine as supplementary intra-articular anesthesia, if
required. A variety of analgesic techniques have been evaluated and
advocated for managing postoperative pain after arthroscopic knee
surgery. These techniques have largely focused on the use of
intra-articular anesthetics, intra-articular opioids, and systemic
nonsteroidal anti-inflammatory agents. Although studies have shown
various degrees of success, intra-articular injections of local
anesthetics and opioids are currently popular for postoperative
analgesia. Intra-articular 0.25% bupivacaine, usually in doses of 20 mL,
is associated with significantly improved early (1-6 hours)
postoperative analgesia, and generally does not appear to be effectively
maintained thereafter. [1] [35] Conflicting results exist regarding the
efficacy of intra-articular morphine with some studies revealing
effective analgesia for up to 48 hours [34] [37]
TABLE 6 -- REGIONAL ANESTHETIC TECHNIQUES FOR KNEE SURGERY
Technique Agents Advantages Disadvantages
Epidural Lidocaine 1.5% ± 2-CP Faster recovery time compared with
spinal or general anesthesia. [57] Relatively slow onset time; wet tap;
patchy block.
Spinal Lidocaine, bupivacaine Rapid onset; dense block. PDPH;
unpredictable duration of surgery.
Nerve block (3-in-1, sciatic) Lidocaine + epinephrine Prolonged
postoperative analgesia; no impairment of voiding. Slow onset; inability
to ambulate.
Femoral nerve block + intra-articular injection Bupivacaine 0.25% +
epinephrine Prolonged postoperative analgesia; no impairment of voiding;
early discharge. Some difficulty with ambulation; ? patchy anesthesia.
Local anesthesia (skin + intra-articular) Lidocaine 0.5% + epinephrine
Use of epinephrine should eliminate need for tourniquet; ? postoperative
analgesia. Minor procedures only; potential for large doses of local
anesthetic.
TABLE 7 -- LOCAL ANESTHETIC AGENTS USED FOR INFILTRATION TECHNIQUES
Agent Concentration Duration without Epinephrine (minutes) Duration
With Epinephrine (minutes)
Lidocaine 0.5-1.0 30-60 120-360
Mepivacaine 0.5-1.0 45-90 120-360
Bupivacaine 0.25-0.5 120-240 180-420
Etidocaine 0.5-1.0 120-180 180-420
and others failing to demonstrate any clinical effect. [32] [56] Reuben
[60] recently evaluated the effect of intravenous and intra-articular
ketorolac (60 mg) with intra-articular bupivacaine (30 mL 0.25%) in
patients undergoing elective arthroscopic meniscal surgery.
Intra-articular ketorolac in combination with bupivacaine significantly
decreased postoperative pain, decreased analgesic requirements, and
increased analgesic duration after arthroscopic knee surgery. Patel et
al [52] suggest that a 3-in-1 femoral nerve block may be extremely
useful for outpatient knee arthroscopy, providing both excellent
postoperative analgesia and a high degree of patient acceptance.
LOCAL ANESTHESIA
Local infiltration of the operative site with dilute solutions of local
anesthetics is a simple and safe technique for outpatients. Because the
injection of local anesthetics can be associated with significant
discomfort, the use of intravenous sedative and analgesic drugs
(so-called "conscious sedation") has become very popular among surgeons.
[45] A variety of surgical procedures, including vasovasotomy,
circumcision, hydrocele and spermatocele repairs, cystoscopy, inguinal
herniorrhaphy, plastic and reconstructive surgery, and breast biopsy
with needle localization, are suitable for local infiltration. In
addition, local anesthetic supplementation (e.g., infiltration with
0.25% bupivacaine) decreases incisional pain in the recovery room and
potentially hastens recovery time. [46] Agents commonly used for local
infiltration are listed in Table 7 .
CONCLUSION
Regional anesthesia is ideally suited for many types of adult outpatient
surgery. It requires appropriate choice of both anesthetic agent and
technique. Central neuraxial anesthesia provides ideal anesthetic
conditions for many procedures, and to avoid delays in time to discharge
caused by either prolonged motor block or inability to void urine, the
use of short-acting agents without epinephrine (lidocaine for
subarachnoid, 2-CP for epidurals) is recommended. A variety of methods
for improved postoperative analgesia is now available to minimize both
patient discomfort and impairment of function. Increased use of regional
anesthesia and analgesia in the ambulatory setting may result in greater
satisfaction for both patient and physician alike.
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