+++
Selection of Techniques, Drugs, & Agents
+++
Rationale for Avoiding General Anesthesia with Volatile Agents in
Outpatients
++
When considering invasive outpatient orthopedic surgery, the routine use
of GAVA without peripheral nerve blocks as the centerpiece of a multimodal
analgesic plan is commonly associated with the following costly outcomes:
(1) postanesthesia care unit (PACU) admission; (2) multiple nursing
interventions for pain and postoperative nausea or vomiting (PONV); (3) PACU
and same-day surgery discharge delays; and (4) unplanned hospital
admission.7–11 However, most hospital pharmacy and
therapeutics committees are primarily focused on the pharmacy budget. Six
percent or less of all hospital costs related to surgical care are
attributed to pharmacy drug costs,12 and examining drug
costs in isolation without regard to patient outcomes is ill-advised. The
“least expensive” outpatient GAVA technique, from the standpoint of drug
acquisition for line items used for anesthesia induction and maintenance,
would probably include thiopental, succinylcholine, opioids and volatile
agents.
+++
Postoperative Nausea & Vomiting & Comprehensive Multimodal
Analgesia in Outpatient Regional Anesthesia Practice
++
++
A traditional GAVA plan (thiopental, succinylcholine, volatile agents,
and opioids) is traditionally favored for these specific line-item budgets
of the anesthesia department and the hospital pharmacy, but the technique is
fraught with “downstream” expenses for the hospital and presents a common
basis for patient dissatisfaction. It has been well documented that GA
techniques that exclusively use propofol for induction and maintenance (or
as an intravenous sedative technique combined with RA) has a significantly
lower PONV rate than do GAVA techniques,10,13,14 and
volatile agents and opioids are considered to be the leading causes of
PONV.15 Exclusive use of propofol instead of volatile
agents is considered to provide an important but incomplete method of
prevention of PONV.15 Three antiemetics of differing
mechanisms are required to prevent equivalent PONV outcomes in GAVA patients
versus propofol total intravenous technique patients.16 RA
techniques (without GA) are historically considered to be protective against
PONV,17 but recent research has indicated that there can
be significant differences in PONV incidence when differing RA techniques
are compared for the same type of surgical procedure.18 In
fact, patients undergoing single-injection peripheral nerve block (PNB)
techniques that are later prescribed intravenous patient-controlled
analgesia (IVPCA) do not appear to have significant benefit of PONV
prevention versus similar patients undergoing GAVA with
IVPCA,17 whereas patients receiving sustained analgesia
primarily with continuous PNBs obtain additional PONV prevention
benefits.17
++
For simple knee arthroscopy (mean procedure time <30 min), GA
with desflurane was compared with ipsilateral hyperbaric bupivacaine spinal
anesthesia (4 mg) to assess PONV and a myriad of other
outcomes.19 Desflurane patients received PONV prophylaxis
with dexamethasone and ondansetron if at least two risk factors were present
(female, nonsmoker, PONV history, or motion sickness). Despite PONV
prophylaxis in at-risk desflurane patients, all desflurane patients
encountered significantly more PONV (6/32, 19%) than did selective spinal
anesthesia patients (zero PONV, p = 0.024).19 In addition,
desflurane patients encountered significantly more pain in both phases of
postoperative recovery and more “extreme tiredness” in phase II recovery
than did patients receiving selective spinal anesthesia.19
++
Generally speaking, for outpatient orthopedic anesthesia
routinely incorporating RA techniques: (1) GAVA should be avoided; (2)
opioids should be minimized; and (3) at least two if not three antiemetics
of differing mechanisms of antiemetic prophylaxis should be used. My
suggested criteria for multimodal antiemetics in outpatient orthopedics are:
(1) if the surgery duration is greater than 30 min; (2) if it is likely that
opioids will be included in the postoperative anesthesia plan; (3) if
intraarticular analgesic adjuncts are used that may increase PONV risk (eg,
opioids, neostigmine); or (4) if GAVA is to be used. In outpatient
orthopedics, use of a volatile agent alone is a sufficient sole risk factor
for routine multimodal antiemetic prophylaxis, regardless of other risk
factors. I suggest (1) oral perphenazine18,20,21 (8 mg
preoperatively, with consideration of a repeat 4-mg oral dose
postoperatively should breakthrough PONV symptoms occur, but avoided in
patients with Parkinson disease or history of adverse extrapyramidal
reactions to phenothiazines); (2) dexamethasone18,22–26
(4 mg intravenously, perhaps avoided in diabetic patients); and (3) a 5-HT3
serotoninergic antagonist. The combination of dexamethasone and a 5-HT3
antagonist is more effective in preventing nausea and vomiting after
discharge than is a 5-HT3 antagonist used alone.27
++
It should be understood that opioids are commonly going to be used for RA
procedure premedication, intraoperative management of nerve block onset
latency, and postoperative analgesic rescue of symptomatic pain not covered
by the peripheral block's nerve distribution. In addition, multimodal
analgesic techniques, such as low-dose intravenous ketamine,28–31 pre- and postoperative inhibitors of the cyclooxygenase type-2
enzyme,32–35 and intraarticular injections by the
surgeon to cover myriad mechanisms of the acute pain inflammatory cascade,
also have the potential to be useful.36–42 As of this
writing, the United States Food and Drug Administration has issued
advisories regarding celecoxib and valdecoxib, while rofecoxib and valdecoxib have already
been withdrawn from the market by manufacturers, due to an increase of
cardiovascular adverse events associated with long-term use, so caution is
advised pending final regulatory declarations.
+++
Minimizing Anesthesia-Controlled Time in the Operating Room
++
++
The potential value of the RA induction room should not be
underestimated from the pharmacoeconomic perspective. Performing PNB
techniques before OR entry has been shown to be associated with a time
savings of approximately 9 min of OR time per case compared with using GAVA
without blocks.9 In general, when the patient enters the
OR ready for surgical preparation, and has a faster emergence (and exit) due
to the use of sedation versus GAVA, an OR with five cases can save 45
min/day. If the cost of a minute of OR time is estimated to be $30, then
1 day of this amount of time savings for five cases carries a potential cost
reduction of $1350. A portion of this theoretical savings is likely
“real” in centers operating at or above 80% capacity, in which forced
overtime (of preoperative, intraoperative, and postoperative
nursing/ancillary staff) is a major budgetary expenditure. The cost savings
becomes even more significant when cases later in the day (eg, after 3
pm or 5 pm) are commonly
“stacked” into fewer available staffed ORs, further lengthening
already-long clinical days. Dexter and colleagues estimated that emergence
which is 6 min faster than baseline likely translates to a per-case overtime
reduction ranging from 1.3 to 2.6 min.43 In a 50-case
surgical pavilion, this translates to 65 to 130 min of overtime saved. How
the reduction of anesthesia-controlled time influences OR staff retention is
unknown. Repeated episodes of forced overtime for OR staff may lead to a
loss of staff morale, which may translate to staff turnover. Staff turnover
implies the replacement of departed, experienced staff with less experienced
staff, associated training, and possible surgical process inefficiencies
until training is complete and posttraining experience is sufficient to
resume an optimally efficient surgical process. Prolonged
anesthesia-controlled time may also adversely affect staff morale in both
phase 1 and phase 2 PACUs. No studies to date have correlated reduced
anesthesia-controlled time and perioperative nursing or OR staff retention.
++
OR time savings for outpatient shoulder surgery, via shorter induction time
and emergence time values has also been substantiated when interscalene
nerve block was used alone without GAVA.44 In this study,
recovery room times and unplanned hospital admissions were also reduced in
the patients treated with the interscalene block versus
GAVA.44
+++
Bypass of the Postanesthesia Care Unit in Ambulatory Surgery
++
++
In outpatient surgery, PACU bypass has been shown to be achievable in
nearly 90% of patients receiving exclusively RA techniques (including
neuraxial techniques if hemodynamic criteria are met).10
To achieve PACU bypass in an institution where RA techniques are used in
high volume, it is important to use tested criteria that incorporate both
physiologic parameters and immediate symptomatic outcomes to determine PACU
bypass eligibility and to use criteria that incorporate specific outcomes
for both RA patients and GA patients.45 Criteria that
incorporate the original Regional Anesthesia PACU Bypass
Criteria,10 the traditional Modified Aldrete
Score,46 the White-Song Fast-Tracking
Criteria,47 and the Mayo Modified Discharge Scoring System
have been recently proposed (Table 74–1).45,48
++
++
In surgical pavilions with large caseloads (eg, 50 cases/day), an 80%
PACU bypass rate (compared with no PACU bypass) can lead to a PACU nurse
full-time equivalent (FTE) staffing reduction of up to four FTE if the PACU
nurses are full-time employees, or by 20 nursing hours if the PACU nurses
are part-time employees.43 When combined with forced
overtime of OR staff and step-down recovery staff, OR time savings and PACU
bypass (documented to be achievable with exclusive use of RA) can present
important cost-saving opportunities for the hospital.
++
In a patient population undergoing anterior cruciate ligament (ACL)
reconstruction, PACU bypass is associated with hospital cost reduction of
$420.49 The cost savings component from the initial of
$420 per PACU bypass patient (which excluded savings associated with
nurse staffing reductions highlighted by Dexter and colleagues detailed
earlier) were likely attributable to RA patients experiencing fewer symptoms
than those receiving GAVA. Williams and coworkers also reported that
throughout the multipavilion university hospital during peak use of PACU
bypass (3000 outpatient orthopedics procedures per year), PACU nurse staffing
requirements for 25,000 surgical patients per year (throughout all
pavilions) consisted of 28 FTE PACU nurses.49 When the
main campus multipavilion hospital relocated outpatient orthopedics to
another off-site hospital in the health system, PACU bypass was used on the main
campus for monitored anesthesia care cases only. Soon after, PACU nurse
staffing requirements increased to 36 FTE for the same annual
caseload.49 PACU bypass should not be underestimated as a
potentially powerful cost management tool in ambulatory orthopedic
anesthesia when nerve blocks are routinely used, not only from a staffing
standpoint, but also with respect to overall symptom reduction and return to
wakefulness during same-day recovery.
+++
Successful Same-Day Discharge in Ambulatory Surgery
++
++
Woolhandler and Himmelstein have estimated that the cost of hospital
admission (for all types of diagnoses and procedures) is
$1050.50 Williams and coworkers found that the hospital
cost increment associated with an overnight admission after ACL
reconstruction was $385.49 The
likely cost differences in the findings of Williams and coworkers versus
those of Woolhandler and Himmelstein are likely related to the generally
healthy status of outpatients presenting for ACL reconstruction. The key
point is that it will always be less expensive for a patient to go home
immediately after outpatient surgery than to be admitted overnight for
observation.51 That said, precautions are required to
ensure that costs are not incurred later in the form of requiring hospital
readmission for complications improperly managed during the initial
admission, especially since these readmissions are often ineligible for
third-party reimbursement. Indeed, refractory pain is the most common cause
of hospital readmission after discharge, accounting for over one third of
such readmissions.52
++
It is important to understand that the associated hospital cost
reductions of $420 for PACU bypass and $385 for successful same-day
discharge were calculated by using standard econometric techniques of
multivariate regression analysis.49 Thus, the associated
cost savings captured in these values incorporate any and all expenditures
related to OR time, additional RA equipment and medications used,
prophylactic antiemetics, and postoperative parenteral nursing interventions
required for symptoms. When specific time-resource and symptomatic outcomes
were incorporated into the stated multivariate regression analysis, these
covariates were not independent predictors of hospital costs, only PACU
bypass and successful same-day discharge were independent predictors of
hospital cost reductions. Thus, when deriving any cost analysis equation
using these cost-saving values, it is important to use these values only for
such analyses, pending the results of future, more detailed, economic
studies. It would not be methodologically correct to simultaneously
incorporate cost values from myriad other studies that calculate various
itemized costs of events such as “minutes of PACU time,” “minutes of
phase 2 recovery time,” or individual drug costs or labor costs. The use of
cost estimate values from multiple studies is methodologically incorrect
since “double-counting” would occur, which may artificially elevate
incremental differences in cost, cost-benefit, cost-effectiveness, and
cost-utility.
+++
Successful Resource Management of Well-Trained Ra Practitioners in the
Ambulatory Surgery Setting
++
++
In ambulatory surgery, well-trained RA practitioners may be tempted to
implement a comprehensive nerve block care algorithm for all surgical
patients. This enthusiasm should be tempered by the consideration of the
“opportunity cost” of providing labor-intensive nerve block anesthesia for
patients who may not necessarily benefit from these procedures. For
instance, in the study by Williams and colleagues,11 543
patients underwent “relatively noninvasive” outpatient knee surgery, while
the remainder underwent “more invasive” knee surgery. Forty-three percent
(253/543) of the patients undergoing the noninvasive procedure received
femoral (with or without sciatic) nerve blocks, but the use of nerve blocks
in these patients was not associated with a reduction in symptoms, nursing
interventions, or unplanned hospital admissions.11 As a
result, these authors concluded that based on this retrospective review of a
significant clinical caseload of noninvasive knee surgery outpatients, nerve
blocks should be reserved for patients who have significant refractory
postoperative pain, or in other special situations such as a complicated
pain history or intolerance to traditional oral analgesic techniques.
++
In the same review of 1200 consecutive knee surgery outpatients, 657
underwent more invasive knee surgery, and 527 of these 657 (80%) received
femoral with or without sciatic nerve blocks.11 In these
patients, nerve block anesthesia and analgesia were significantly associated
with reduced pain symptoms during recovery (therefore, fewer nursing
interventions for pain management), and fewer unplanned hospital admissions.
It is important to note that the selection of nerve block
anesthesia–analgesia appears to be necessary but not sufficient to
comprehensively reduce postoperative nursing interventions and unplanned
hospital admissions: whenever GAVA was used (in the presence or the absence
of nerve block anesthesia), the odds ratio of more associated symptoms after
GAVA was 2.1 (p < 0.001), whereas the odds ratio of more associated
unplanned hospital admissions after GAVA was 3.3 (p =
0.001).11 Thus, nerve block anesthesia and analgesia for
indicated (more invasive) procedures (ideally in the setting of a
comprehensive multimodal analgesic care plan) and the avoidance of GAVA (for
all procedures) will likely provide the anesthesia care team (and the
hospital) with the fewest possible side effects and the greatest
facilitation of successful same-day discharge. However, routine nerve blocks
for noninvasive knee surgery may be an investment of RA practitioners' time
(and risk) that may provide relatively little benefit, and that takes away
opportunity for RA practitioners to engage in other value-adding activities.
Such value-adding activity may include the placement of continuous nerve
block catheters for select patients, when time may have been only available
previously to administer a single-injection nerve block.
+++
Pain Risk Stratification
+++
Upper Extremity Surgery
++
++
For outpatient shoulder or upper extremity surgery, there have been few
substantiated, comprehensive recommendations for allocating nerve blocks
(single-injection vs continuous infusion) based on anticipated postoperative
pain, postoperative nursing interventions (with versus without), or
unplanned hospital admissions.
++
In shoulder surgery, the comparison of single-injection blocks with GAVA
has shown predictable findings. For arthroscopic acromioplasty of the
shoulder performed under GAVA, Singelyn and colleagues showed that
interscalene nerve block provided definitive recovery advantages over
suprascapular nerve block, single-injection intraarticular local anesthetic,
and controls.53 For outpatient open surgery of the rotator
cuff, Hadzic and coworkers reported that GAVA use (vs single-injection
brachial plexus block with ropivacaine) led to increased postanesthesia care
unit admissions (vs phase 1 recovery bypass), higher reports of
postoperative pain, longer time to ambulation, longer time to same-day
discharge, and higher risk of unplanned hospital
admission.54 In this study, no outcome differences
occurred in follow-up from 24 h to 2 weeks after surgery, but this study was
underpowered.
++
In a recent review, Boezaart suggested that an anterior approach to the
brachial plexus is ideal for open-shoulder surgery, whereas a posterior
(paravertebral) approach is well suited for arthroscopic
surgery.55 In this review, Boezaart explains that the
anterior approach to the brachial plexus concomitantly provides reliable
anesthesia to the overlying skin, but the posterior approach does not.
Potential advantages to the posterior approach may include less frequent
blockade of the phrenic nerve, but the posterior approach is also associated
with less motor block. Arthroscopic shoulder surgery using the posterior
approach, most commonly, must be accompanied by general
anesthesia,55 in order to provide sufficient analgesia to
the overlying skin.
++
In two recent, separate studies of the efficacy of intraarticular analgesic
infusions, some conclusions can be drawn regarding pain risk stratification
in common outpatient shoulder procedures. One study by Harvey and associates
showed that patients undergoing arthroscopic subacromial decompression of
the shoulder receiving ropivacaine 0.2% in a continuous subacromial
infusion experienced 34% lower pain scores than did saline
controls.56 Another study by Boss and
coworkers57 showed that patients receiving a continuous
subacromial infusion of bupivacaine 0.25% after open acromioplasty and
rotator cuff repair did not experience any difference in pain relief from
those receiving saline placebo infusion. In one study by Klein and
colleagues, patients undergoing open rotator cuff repair with an active
treatment of local anesthetic infusion via an indwelling interscalene
catheter had significantly improved pain management than did control
patients receiving a saline placebo infusion.58 Thus, the
logical conclusion can be reached that open acromioplasty and rotator cuff
repair likely creates more postoperative pain than does arthroscopic
subacromial decompression, based on the lack of responsiveness of the former
(more invasive) procedure to subacromial infusion analgesia, whereas the
less invasive procedure is responsive to subacromial infusion analgesia.
However, open rotator cuff repair patients have favorable analgesic
responses when a continuous interscalene catheter with local anesthetics is
used.
++
A review by Chelly and associates59 provides an overview
that may guide practitioners for categories of postoperative shoulder pain,
until more definitive evidence is available. In this review, shoulder
procedures are clustered into a catheter-eligible category if the following
procedures are involved: shoulder arthroplasty, rotator cuff repair, Bankart
repair, and open reduction/internal fixation of the humerus. The benefit of
continuous interscalene catheters for shoulder arthroplasty and rotator cuff
repair is well documented.58,60–65 Although logic would
indicate similar effectiveness for less invasive procedures, there is little
evidence at this time to indicate that interscalene brachial plexus
catheters would be similarly useful for patients undergoing less invasive
shoulder operations such as shoulder stabilization procedures, distal
clavicle resection or acromioplasty, subacromial decompression, biceps
tenodesis or tenotomy, or even routine debridement inside the glenohumeral
joint, when compared with single-injection nerve blocks and perioperative
multimodal oral analgesia. Thus, studies are needed to show the benefit of
continuous nerve blocks (vs single-injection), and single-injection blocks
(vs no blocks) for a wide variety of shoulder procedures that produce an
uncertain magnitude of postoperative pain.
++
For outpatient wrist and hand surgery, Hadzic and coworkers addressed this
patient population comparing chloroprocaine infraclavicular nerve block with
GAVA, showing that GAVA use led to increased postanesthesia care unit
admissions (vs phase 1 recovery bypass), higher reports of postoperative
pain, longer time to ambulation, and longer time to same-day
discharge.66 However, there were no outcome differences in
follow-up from 24 h to 2 weeks after surgery. This latter finding was
underpowered and did not show statistical equivalence.66
Chan and associates prospectively studied nonrandomized hand surgery
patients (n = 126) undergoing either GAVA (n = 39), axillary block
(n = 42), or Bier block (n = 45).67 GAVA was associated with
the most postoperative symptoms and nursing labor intensity, as well as the
longest discharge times. Bier block patients had the fastest recovery times
and lowest associated total perioperative costs, but also were at small risk
for conversion of the anesthesia plan (2/45) to GAVA due to tourniquet pain.
Gebhard and colleagues retrospectively studied hand surgery patients
(n = 62) receiving GAVA (n = 20), Bier block (n = 21) or wrist block
(n = 21).68 They found that wrist block patients were
discharged home soonest, and encountered (1) less hypertension than did Bier
block patients; and (2) less hypotension than did GAVA
patients.68 McCartney and coworkers prospectively studied
100 hand surgery outpatients randomized to receive GAVA
(n = 50) or brachial plexus block with lidocaine (n = 50). These authors found
essentially similar if not identical findings to those reported by Hadzic
(prospectively) and Chan (retrospectively) as mentioned earlier. McCartney
and coworkers also concluded that there were no long-term (2-week) pain
outcome differences, although the brachial plexus block group only received
the short-acting local anesthetic lidocaine.69
++
For other (distal) upper extremity surgery, Chelly and associates state that
PNB catheters are likely indicated for implantation procedures after trauma,
as well as for open reduction/internal fixation of the hand or
digits,59 although a prospective randomized trial to
definitively verify this intuitive concept may be difficult to achieve.
Ilfeld and colleagues have shown that a continuous infraclavicular brachial
plexus catheter (vs placebo catheter infusion) resulted in less
postoperative dynamic pain and opioid consumption and fewer sleep
disturbances.70 The surgical procedures performed included
open reduction/internal fixation (elbow, radius, or ulna), bony/capsular
wrist procedures (carpectomy, capsulodesis, fusion, or shrinkage) metacarpal
arthroplasty, suspensionplasty, and ulnar nerve transposition. Although all
of these procedures are intuitively painful, the small study sample size (30
patients divided equally between two groups) prevents the practitioner from
distinguishing relative postoperative pain scores per
procedure.70
++
Less invasive upper extremity procedures (typically applicable to
outpatients) have not been comprehensively studied with respect to potential
the value of continuous catheters versus single-injection blocks. However,
Rawal and coworkers71 showed that an axillary continuous
nerve block catheter with intermittent bolus dosing provided excellent wrist
and hand analgesia for patients undergoing surgical procedures that may have
been somewhat less invasive than those described earlier by Ilfeld and
colleagues.70 Rawal and coworkers' study included 60
patients who received a mepivacaine axillary block bolus and concomitant
nerve block catheter placement and were undergoing carpal tunnel release
(n = 11), finger fracture repair (n = 11), tendon repair
(n = 10), finger joint arthrodesis (n = 10), wrist arthroscopy
(n = 8), and tumor resection or other procedures (n = 10). This study neither
studied a control group of patients undergoing no nerve block, nor a
treatment group undergoing single-injection nerve block only. In fact, 3 of
the 60 patients studied did not use the bolus dose function postoperatively.
However, most every bolus treatment was prompted by patients achieving a
verbal pain score of at least 5 (out of 10), and bolus treatments returned
pain scores to around 3 (out of 10), thus providing clinically significant
analgesia.71 Patients in this study used all of their
allotted boluses by the twelfth hour after surgery; as such, the reader may
speculate that patients may simply benefit from a long-acting
single-injection nerve block designed to provide 18 h of postoperative
analgesia, instead of the technical complexity of a nerve block catheter.
Rawal and coworkers found that the most common cause of patient
dissatisfaction with the continuous catheter, intermittent–bolus technique
was hand numbness.71 Therefore, patient uncertainty and
potential dissatisfaction associated with prominent numbness or motor block
should likely be factored into the decision of which nerve block technique
is selected when a single-injection versus a continuous catheter technique
is considered.
++
To summarize, outpatient hand surgery often results in significant
postoperative pain, with patient pain scores often reaching or exceeding VAS
5 (out of 10).72 Retrospective reviews and prospective
studies have demonstrated uniformly that patients receiving PNBs have
significantly improved outcomes on the day of surgery compared with patients
receiving GAVA. For shoulder surgery, the use of continuous brachial plexus
catheters is sufficiently substantiated to recommend their routine placement
(by trained practitioners) for invasive shoulder surgery. These findings
also encourage the routine use (by trained practitioners) of all
peripheral/regional techniques for upper extremity surgery, although further
research is needed to determine outcome benefits of continuous versus
single-injection nerve blocks in the days and weeks following mildly to
moderately invasive shoulder and distal upper extremity surgery. The
usefulness of intraarticular and incisional infusions after simple
arthroscopic procedures of the shoulder has been documented, but these
articular and incisional infusions do not appear to confer sufficient
analgesia after more invasive, open, shoulder surgery.
++
++
Recommendations for rational nerve block selection (single-injection, vs
continuous catheter, vs none) in outpatient knee surgery have been recently
suggested.73 This guideline incorporates the resource
management principles described earlier, and creates three major categories:
(1) noninvasive, (2) more invasive, and (3) most invasive (Table
74–2). Noninvasive implies that routine use of nerve block analgesia is
probably not necessary, as described previously.11 “More
invasive” implies that a routine femoral nerve block would be recommended,
but that a sciatic nerve block is probably not necessary, since the vast
majority of the postoperative pain is likely attributable to the femoral
nerve distribution. “Most invasive” implies that the postoperative pain
will be likely attributable to both femoral and sciatic nerve distributions,
and both nerves would likely benefit from routine blockade. The more
invasive and most invasive knee surgery categories are based on clustering
moderate and severe into one category of surgical
invasiveness.11 This algorithm73 also
describes when a single-injection block would likely be sufficient, vs when
a continuous nerve block catheter would likely be of greater benefit than a
single injection.
++
+++
Foot and Ankle Surgery
++
++
For outpatient foot and ankle surgery, few if any substantiated,
comprehensive recommendations are available for allocating nerve blocks
(single-injection vs continuous infusion) based on anticipated postoperative
pain, postoperative nursing interventions (with vs without), or unplanned
hospital admissions. Interestingly, few studies compared PNBs with GAVA
for surgery below the knee. In addition, few studies have categorized
postoperative foot and ankle pain as sufficiently manageable with a
single-injection nerve block vs requiring an indwelling sciatic nerve
catheter. Most studies evaluating the use of various approaches to the
sciatic nerve block for foot and ankle surgery have either simply evaluated
block success rate (with no comparative treatment group), compared varying
popliteal/sciatic nerve block approaches (sometimes with neuraxial
techniques), or compared continuous infusion strategies.
++
Singelyn and colleagues provided one of the first studies describing
efficacy of the popliteal fossa block placed with nerve stimulator guidance,
and reported a low 3% (15/507) rate of conversion to
GAVA,74 whereas Provenzano and coworkers reported a
conversion rate to GAVA of 18% (84/467).75 In the same
study, Provenzano and coworkers reported a significant reduction in
postoperative opioid requirements in patients with a successful popliteal
fossa block compared with 367 patients who did not receive the
block.75
++
When neuraxial techniques are being considered, Curatolo and associates
provide important insight that epidural anesthesia for foot and ankle
procedures is associated with a high (4.4%, 7/160) conversion rate to
GAVA, although epidural success was correlated with larger per-segment
doses.76 Two studies have compared the efficacy of spinal
anesthesia with popliteal fossa block, and both showed intraoperative
efficacy of both techniques, although the in-hospital recovery after spinal
anesthesia was more lengthy,77,78 with an additional risk
of urinary retention after spinal.78 Generally speaking,
meaningful postoperative analgesia should not be expected after neuraxial
techniques, and analgesia after popliteal fossa block will depend on the
local anesthetic agent (and additives) used. In addition, when the analgesic
duration of the popliteal sciatic block (with long-acting local anesthetics)
is compared with the durations of ankle block, foot block, or subcutaneous
infiltration, one should expect doubling or tripling the analgesic duration
with a sciatic-specific depot injection.79
++
Continuous sciatic nerve catheters have gained popularity in recent years.
After being introduced by Singelyn and colleagues who described a complex
Seldinger (catheter-over-guidewire) technique for catheter placement
(achieving a 92% success rate),80 authors have
repeatedly found that continuous infusion nerve blocks lead to excellent
analgesic outcomes when compared with single-injection blocks (or placebo
catheters).81–83 At this time, there are no definitive
guidelines for the selection of single-injection vs continuous
popliteal/sciatic techniques based on anticipated surgery, with the
exception of recommendations implied by the myriad findings reported
earlier. Others have suggested that for hardware removal from the foot and
ankle, a single-injection block is sufficient, whereas for most other foot
ankle procedures, the use of a continuous sciatic catheter may have
additional benefits.59 The ultimate decision about the use of
single-injection vs continuous sciatic techniques may depend on realistic
expectations by the surgeon regarding return to weight-bearing status. In
this situation, the surgeon may not have an accurate impression of
weight-bearing success rates in the setting of uncontrolled pain, but full
weight-bearing in a the setting of a partially anesthetized sciatic nerve
(via a continuous sciatic catheter) may be ill-advised.
+++
Summary Statement Regarding Nerve Block Technique Allocation
++
The rational use of single vs continuous nerve block techniques in
ambulatory surgery, that is, allocating the “scarce resource” of the
well-trained RA practitioner and avoiding routine nerve blocks for patients
who probably do not need them (or providing single-injection nerve blocks
when a continuous catheter is not likely needed) will free up time to
perform catheter techniques for patients undergoing indicated procedures. In
OR settings that care for both outpatients and inpatients, this strategy
allows the skilled RA practitioner to also dedicate time to nerve block
catheter placement where it is most beneficial.