++
The goals of the anesthetic plan are to ensure that the patient is
properly evaluated, (ie, the choice of the anesthetic technique is the best
for the patient based on the surgical procedure), the patient's physical and
mental status has been assessed, and that the patient will remain
hemodynamically stable when her inherent protective reflexes are blunted or
abolished. Additional considerations with regional anesthesia include
providing adequate premedication, placing the block efficiently so as not to
compromise valuable OR time, providing complete anesthesia for the surgical
site, planning for an inadequate or incomplete block, and patient comfort
during long procedures.72
++
Wrong-side anesthetic procedures have been reported in patients
receiving peripheral nerve blocks, especially when the patient changes
position for the block.73 Wrong-sided blocks probably
occur more frequently than reported. Despite multiple checks,
laterality errors can occur, particularly in institutions where large
numbers of nerve blocks are performed. Risk factors that may contribute to
these errors include delay between obtaining the patient's consent and the
block performance, different anesthesiologists performing the block and
managing the patient intraoperatively (resident “block rotations”), time pressure to
administer the block without delaying surgery, and covering the patient's
involved extremity with blankets to maintain warmth, effectively obscuring
the marked site of surgery.
++
A rigid laterality protocol prior to the block placement should substantially
reduce the risk of wrong-sided blocks. In our institution the following
procedure is followed:
++
The surgical staff is required to mark the surgical site immediately
prior to taking the patient to the OR using a wide marker and marking the
site as “YES.”
Once the patient is in the OR, the surgical and anesthesia staff confirm
the laterality with the OR nurse immediately on arrival in the OR.
Both of the patient's extremities are uncovered and examined for
laterality prior to the block procedure.
A “time-out” for confirmation between two caregivers is required
before block performance as well as before the surgical incision.
++
Fortunately, long-term sequalae after laterality errors typically do
not occur, but there is an increased risk of performing surgery on the wrong
side when the wrong limb is anesthetized. Careful attention to the surgical
consent, the marked extremity, and following procedures to double-check the
surgical site are important in preventing laterality errors in patients
receiving peripheral nerve block anesthesia.
+++
Premedication of Patients for Neural Blockade
++
Premedication is one of the essential elements for successful neural
blockade, whether it is for neuraxial blocks or peripheral nerve blocks.
Anxiety causes feelings of uneasiness, tension, and nervousness and has been
associated with a higher degree of intraoperative movement and sedation
requirements. Utilizing anxiolytic premedication does not delay hospital
discharge and is associated with a greater degree of patient
satisfaction.74,75 A patient's previous experience with
regional anesthesia is a significant factor in acceptance of a regional
technique for future surgery. Fear of needle puncture has been cited as a
major cause for patient dissatisfaction or refusal of regional
anesthesia.76,77 If a paresthesia technique is utilized
for placement of a peripheral nerve block, less sedation is used as patient
cooperation is necessary, but it should not be eliminated. When a nerve
stimulator is employed for placement, a greater amount of sedation can be
used for patient comfort.
++
Premedication with an anxiolytic should be administered preoperatively
just as it is given prior to general anesthetics.78–80
In addition to the benefits mentioned, premedication prevents patients from
having an unpleasant recollection of the anesthetic experience. Inadequately
premedicated patients move during the block placement, making it difficult
to interpret responses to nerve stimulation and possibly dislodge the needle
from its intended position.
++
All peripheral nerve blocks can be divided into two major groups: blocks
associated with minor patient discomfort (superficial blocks) and blocks
associated with more patient discomfort (deep blocks). A sedation protocol
should be chosen according to the regional anesthesia technique planned and
according to individual patient characteristics. For instance, an
interscalene brachial plexus block can be administered to a minimally
sedated, fully alert patient. On the other hand, an infraclavicular,
sciatic, or lumbar plexus block necessitates, for most patients, a greater
degree of sedation and analgesia to ensure the patient's comfort and
acceptance. Regardless of the sedation technique chosen, the goal of
sedation is to provide maximum patient comfort while maintaining meaningful
patient contact throughout the procedure.
++
++
The pharmacology of drugs commonly used for premedication in regional
anesthesia is discussed in greater detail in Chapter 11 (Sedation–Analgesia
During Local and Regional Anesthesia). The discussion here will be limited
only to salient features of immediate relevance to the practice of regional
anesthesia.
++
Midazolam is one of the most common anxiolytics used for premedication.
Midazolam is effective given orally, intranasaly, sublingually,
intramuscularly, intravenously, and as a continuous
infusion.81 It has been used in combination with a variety
of medications, such as narcotics, propofol, and dexmedetomidine, for
intraoperative and postoperative pain management. Benzodiazepines bind
specific receptors in the central nervous system, enhancing the inhibitory
effect of various neurotransmitters. For example, benzodiazepines facilitate
GABA-receptor binding, leading to an increase in the membrane conductance of
chloride ions. The subsequent change in membrane polarization inhibits
normal neuronal function. The advantages of midazolam compared with other
drugs in this class include flexibility in administration methods, lack of
pain on administration either intravenously or intramuscularly, and its
favorable onset and duration of action. It has been suggested that midazolam
may also have a favorable effect on postoperative nausea and
vomiting.80
++
A narcotic analgesic is introduced only at the time of needle placement. For
example, alfentanil provides intense analgesia of short duration, making it
an excellent choice for administration just prior to block placement.
Alfentanil is a less potent (1/5 to 1/10) analog of fentanyl. It penetrates
the brain rapidly with an onset time to peak effect of 1 to 2 min. Recovery
from alfentanil is more rapid than from fentanyl or
sufentanil.82 Prolongation of drug effect after large or
repeated doses is less likely because of its increased protein binding,
lower lipid solubility, and smaller volume of distribution. Unlike fentanyl,
there are no secondary increases in alfentanil plasma concentrations after
large or repeated doses.83 When alfentanil is used for
block placement, evaluation of the block can be conducted with return of
full patient cooperation within minutes.84 Fentanyl and
sufentanil have also been used effectively as part of the block sedation
regimen. Fentanyl, in titrated doses of 25 to 100 mcg, provides satisfactory
analgesia for block placement with minimal untoward side effects (eg,
hemodynamic instability or severe respiratory depression), but plasma levels
can increase with large or repeated doses.85
++
When multiple nerve blocks are necessary, low-dose sufentanil has been suggested
to be an effective alternative to alfentanil, providing satisfactory pain
relief without alterations in consciousness.79 Regardless
of the narcotic chosen, timing of the administration of the narcotic depends
on its onset and peak effect, which should coincide with needle insertion
through deeper tissues. The dose and type of premedication used depend on
the procedure, the patient, and the anesthesiologist's knowledge of the
pharmacodynamics of the drugs chosen. Commonly used regimens for sedation
during various regional anesthesia procedures are listed in Table 61–1.
++
++
+++
Performance of Neural Blockade: Block Area vs Blocks in the OR
++
Peripheral nerve blocks are often thought to result in decreased OR
efficiency. In contrast to this popular belief, when actual OR times are
compared in that manner, several studies have demonstrated that OR times are
actually reduced with the utilization of regional
anesthesia.86 In a study by Williams and coworkers
comparing general anesthesia with peripheral nerve blockade or to a
combination of both, regional anesthesia was associated with the lowest
anesthesia-controlled time, the lowest turnover time, and the lowest
incidence of unplanned hospital admission.87
++
Whether a designated block room is needed depends on the skill and
experience of the anesthesiologist as well as the local anesthesiology
practice and layout of the holding area and ORs. Studies evaluating OR
efficiency with peripheral nerve block anesthesia performed in an induction
room vs in the OR have demonstrated conflicting
results.86,88 Advantages of an induction room include
reduction in OR time (arrival to beginning of surgery), less stressful
environment for resident education and training, and the ability to change
the anesthetic plan or redo an inadequate block without delaying surgery.
Disadvantages of a designated block or induction room include the need for
qualified personnel to monitor the patient once the block is placed,
additional expenses related to the physical space and equipment, and lack of
utilization of the space (first case of the day, outside regular OR hours,
next patient not ready for a variety of reasons)89,90
Patient anxiety levels are unchanged whether the block is placed in the OR
or in a dedicated induction area.91 In teaching
institutions where peripheral nerve blocks are routinely administered in the
OR, anesthesia induction time improves with the skill level of the
anesthesiologist.92
++
++
Regardless of where the actual procedure is performed, adequate space,
equipment, and monitoring are imperative to ensure time-efficient care of
the patient. If a block room is used, the physical size should allow enough
space for proper monitoring, emergency access, and resuscitation of the
patient. All supplies, drugs, and other equipment for the block procedure
should be readily available in the room and prepared at the bedside. Proper
lighting, administration of oxygen, and emergency airway management equipment
with suction must be available whenever a nerve block is performed.
+++
Intraoperative Management
++
Almost any anesthesiologist with skill and determination can
become proficient in neuraxial and peripheral nerve blocks, but the
intraoperative treatment of the patient can be the most challenging aspect
of the practice of regional anesthesia. Sedation appropriately adjusted for
patient comfort is always beneficial and improves the quality of the
anesthesia achieved with peripheral nerve blocks. Most surgeons prefer
patients to be lightly asleep during surgery so that they can better
concentrate on the technical aspects of the operation. Similarly, the
majority of patients also prefer not to be aware of activities in the OR.
The choice and amount of sedation depends on the patients' desire for
sedation, their tolerance, and any medical problems that may affect the
ability to tolerate deeper levels of sedation.
+++
Intraoperative Sedation
++
Many choices are available for intraoperative sedation once the
block has been placed. For an in-depth discussion on these medications see
Chapter 11 (Sedation–Analgesia During Local and Regional Anesthesia). Here
we will briefly discuss advantages and disadvantages to many of the
medications often used in conjunction with regional anesthesia. The
anesthesiologist should be comfortable with the mechanism of action, onset
and duration, side effects, and hemodynamic effects of the medications used.
It is prudent to remember that not all patients require significant additional sedation
beyond that used for initial block placement.
++
Propofol, a diisoprophenol, is commonly used for induction, sedation,
and maintenance of anesthesia. Because of its water insolubility, it is
prepared in an emulsion that can cause pain on injection especially through
small veins. Advantages of propofol include rapid onset, elimination, and
low incidence of side effects. It has an antiemetic quality, making it a
desirable medication for ambulatory surgery. Disadvantages in addition to
the incidence of pain on injection include significant cardiovascular
depression, especially in the elderly or debilitated patient. Propofol can
either be given as repeated bolus doses every 5–15 min or, more commonly,
as a continuous infusion. The usual dose for sedation during regional
anesthesia is between 10 and 50 mcg/kg/min.
++
Dexmedetomidine, an α2-receptor agonist, has been
used in critical care settings to effectively provide sedation with less
hemodynamic instability than with propofol. It is gaining popularity as an
effective agent for intraoperative sedation. Dexmedetomidine is
approximately eight times more selective toward the
α2-adrenoreceptors than clonidine. It decreases
anesthetic requirements by up to 90% as well as inducing
analgesia.93 At therapeutic doses, dexmedetomidine is not
associated with respiratory depression, despite the profound levels of
sedation that occur. It has the advantage of reducing postoperative narcotic
requirements because of its analgesic properties. Compared with propofol, it
has a slower onset and offset of sedation. Intraoperative mean arterial
pressure is not reduced to the degree seen with propofol. Heart rate is
decreased because of its sympatholytic and vagal-mimetic
effects.94 The average infusion rate for intraoperative
sedation is 0.5–0.8 mcg/kg/h. It is important for the clinician to note
that errors with dexmedetomidine infusion have occurred because the drug was
infused in micrograms per kilogram per minute instead of micrograms per kilogram
per hour.95
++
Clonidine, an α2-adrenoreceptor agonist, has been
advocated as another effective agent for intraoperative sedation. In a study
on patients undergoing prolonged dental surgery, it was infused at a rate of
2 mcg/kg. It did not induce significant bradycardia, hypotension, or other
severe side effects in healthy volunteers and provided an analgesic effect
similar to that for dexmedetomidine.96
++
Low-dose midazolam infusions (0.03–1 mg/kg/h), combinations of ketamine and
midazolam, and propofol and ketamine have been used effectively for
intraoperative sedation after block placement. Ketamine has potent analgesic
effects, provides hemodynamic stability (sympathomimetic action), and has
minimal effect on the ventilatory drive, making it an excellent choice for
debilitated patients or as a supplement for incomplete regional anesthesia.
Analgesia can persist up to 40 min after ketamine administration has been
terminated. Its association with postanesthetic confusion, disorientation,
bad dreams, or hallucinations has limited its use in ambulatory surgery.
Premedicating the patient with midazolam, limiting the dose, and allowing
the patient to recover quietly will circumvent some of the untoward effects
of ketamine.97,98
++
The use of narcotics during the intraoperative treatment of patients
receiving regional anesthesia should be limited unless the patient has a
chronic condition causing discomfort unrelated to the blocked surgical site.
Narcotics should be used for analgesia and patient confort, not for anesthesia. They should not
used to “rescue” an incomplete or failed block. Patient complaints should
be investigated to determine if the discomfort is from positioning, prior
chronic conditions, or in the surgical area not completely covered by the
block. Because anesthesia of the skin is often the last to occur, local
infiltration by the surgeon, when possible, and deeper levels of sedation at
the beginning of the procedure are often all that is required for the
procedure to proceed while the block is “setting up.” Providing adequate
padding for extremities; support for the upper back, shoulders, and head;
prewarming the OR table; and providing continued warmth with forced air
heating, heated blankets, and warmed intravenous infusions will decrease
the discomfort caused by the cold OR and firm OR table. Deeper levels of
sedation or opioids may be required for patients with chronic pain conditions. Using a
short-acting sedative (eg, propofol) is a better choice than continued
narcotic boluses that will compromise the patient's ability to protect the
airway. If the block is inadequate or these measures are ineffective, it is
safer to induce a light general anesthesia and control the airway rather
than resorting to oversedation and intravenous narcotics. However, patients
who chronically use oral opioids to treat their osteoarthritic or other pain
needs may require and benefit from the judicious intraoperative use of
opioids for their comfort.
++
Finally, some patients can be well sedated by the administration of low
concentrations of nitrous oxide, similarly to the practice widely used in
dental offices. Others, however, may be very intolerant of the effects of
nitrous oxide. Nitrous oxide has analgesic and sedative properties and can
be easily discontinued if the patient is not tolerating it.
++
+++
Intraoperative Monitoring
++
Intraoperative monitoring is essential to the safety of regional
anesthesia. Before any local or regional anesthetic is administered,
equipment and medications should be available to support full resuscitation.
The same equipment used for general anesthesia should be checked and be
immediately available in the event that the anesthetic is converted to
general. If the block is placed in the OR, blood pressure,
electrocardiography, pulse oximetry, and end-tidal carbon dioxide monitoring
should be instituted before the block is placed. A face mask (6 L of oxygen)
or nasal cannula (up to 5 L of oxygen) should be applied once sedation is
begun and continued throughout the case. It is of utmost importance that a
properly functioning bag–mask device capable of delivering positive–pressure
ventilation be immediately available in the area where regional anesthesia
is practiced. The CO2-sampling line can be connected to
the face mask or to the nasal prongs to provide continuous end-tidal
CO2 measurement. Temperature monitoring should follow ASA
standards.99 For longer cases in which large areas of the
patient's body are exposed, the patient's temperature should be monitored
continuously.
++
Monitoring the patient under light or deep sedation requires vigilance
on the part of the anesthesiologist. The potential problem of
hypoventilation induced by sedatives is ever present. End-tidal
CO2 monitoring and pulse oximetry help guide the depth of
sedation that is safe for the patient. In one study of plastic surgery
patients, 39% of the patients developed oxygen saturations below 89%,
despite appropriately administered sedation.100
++
+++
Intraoperative Patient Care
++
In addition to hemodynamic monitoring, other needs of the patient need
to be addressed whether the patient is under light or deep sedation. Noxious
stimuli and uncomfortable positioning may make a pleasant experience
potentially intolerable.
++
Significant noise levels are often present in the OR due to discussion
among the staff, handling of instruments, or the use of various pneumatic
instruments. In a study on noise levels during various orthopedic surgical
procedures, noise levels up to 118 decibels (dB)—a level that is
potentially damaging to the hearing—were recorded when pneumatic drills
and saws were used. Suction tips were found to yield levels up to 96
dB.101 In another study on the effect of noise on the
bispectral index, noise levels over 100 dB resulted in an appreciable
increase in the bispectral index, despite propofol
sedation.102 Shielding the patient's ears from the
unwanted noise should be done routinely to help reduce the patient's
anxiety.
++
Warming the OR table with forced air prior to positioning the patient on the
table, then covering the patient with a warm blanket helps to relax the
patient and provide comfort prior to sedation for the block injection
(Figure 61–7). Preventing hypothermia during the operation will
help prevent uncomfortable postoperative shivering and delays in discharge
from the recovery room. Making the OR table as comfortable as possible with
additional padding and positioning will make longer procedures more
tolerable, especially for the arthritic patient or the patient with chronic
axial pain.
++
++
+++
Transition of Patients from the OR to Postoperative Care
++
After surgery, most patients are fully alert and able to meaningfully
discuss the findings with the surgeon in the OR while a wound dressing is
being applied. On arrival in the recovery room, most ambulatory surgery
patients are fast-tracked to the postanesthesia care unit and prepared for
discharge. Inpatients are often more comfortable, especially in the early
recovery period, due to the lasting effects of the local anesthetics chosen
for the regional technique.
+++
Transfer of Care to the Nursing Staff
++
To prevent unnecessary concerns by anyone involved in treating the
patient, it is important, on completion of the surgical procedure, to
discuss with the surgeons, patient, and nursing staff the expected duration
of the motor and sensory blockade. A proper multimodal pain management
protocol should be developed and thoroughly discussed with the nursing staff
and the patients and their families. An understanding of the need to provide
pain relief for surgical areas not covered by the nerve block and to avoid
severe pain when the block wears off is important for a satisfactory
postoperative recovery. To avoid unnecessary consultations, it is important
for the staff and patient to understand that the block may last longer in
some patients than in others because of the variability in the duration of
action of local anesthetics.
++
+++
Outpatient Acute Pain Management
++
Standard verbal and written instructions regarding pain management at
home and protection of the anesthetized extremity are commonly provided for
outpatients to ensure continued safe and satisfactory
recovery.52 Additional instructions are necessary for
patients with continuous peripheral nerve block analgesia. Both verbal and
written instructions about the infusion pump, its safety mechanisms, signs
and symptoms of local anesthetic toxicity, and contact information should
any questions arise should be given to the patient before discharge. Most
centers utilizing continuous peripheral nerve block infusions at home have
developed protocols for patient follow-up and evaluation, patient and
nursing education, and emergency contact information. When home health
nurses can be involved, extensive patient education and home evaluation can
be conducted. The home health nurses can be trained to evaluate the patient
for adjustments in drug delivery and assess catheter sites, dressings, and
infusion devices. They can be trained to remove the peripheral nerve
catheters, saving the need for the patient to return to the hospital for
care. Telephone follow-up within the first 24 h is a necessary part of
patient care when continuous catheters are utilized. Depending on the length
of time the catheter is left in place, continued regular follow-up by
telephone or a postoperative visit should be instituted until the catheter
is removed.103
++
It is beyond the scope of this chapter to discuss various local
anesthetic protocols for continuous outpatient nerve blocks (the reader is
directed to Chapter 10 [Local Anesthetic Solutions for Continuous Nerve
Blocks] for more information on this subject). In general, a continuous
infusion of dilute ropivacaine (0.2%) at a continuous rate of 5–10 mL/h
has been suggested by some authors as it provides excellent sensorimotor
dissociation with better preservation of motor function than
bupivacaine.104 Other administration protocols include PCA
(bolus technique) or a low background continuous infusion combined with a
smaller boluses of PCA. It has been suggested that PCA techniques reduce the
local anesthetic consumption by 64 to 73%.105
+++
Inpatient Acute Pain Management
++
The same education is important for the patient who is to be admitted
after a surgical procedure with regional anesthesia. Because longer-acting
local anesthetics can be used for the patient who is to be admitted, it is
important for the nursing and surgical staff to understand that the duration
of the sensory and motor block will be prolonged. Again, educating the staff
and the patient will prevent unnecessary consultations for neurologic
defects. Even surgical staff comfortable with regional techniques need to be
educated about the duration and effect of the peripheral nerve blocks. For
example, when a patient has a total knee replacement, often a continuous
femoral nerve catheter is placed for postoperative pain control. The femoral
nerve block will cover a large portion of the area causing pain, but the
sciatic distribution is not blocked. Pain control for the sciatic
distribution is usually best accomplished by prescribing intravenous PCA or
oral analgesia. This multimodal approach to pain management is especially
important for the inpatient as the surgical procedures are usually more
involved. Educating the staff about the benefits and limitations of the
block as well as the need for additional pain medication will prevent
misconceptions about patient pain complaints.106,107
++
Other factors related to the block also require staff education for the
safety of the patient. If the block is going to affect lower extremity motor
function, the patient will not be able to get out of bed by himself or bear
weight on the blocked lower extremity. This should be explained to the
patient and the caregivers. If an upper extremity block has been performed,
then measures to protect the blocked upper extremity (eg, sling for
interscalene blocked extremity) need to be instituted. The patient and
family need to be reminded that the full function of the extremity will
return when the block wears off.