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Florida Heart CPR*
Local Anesthesia
2 hours
INTRODUCTION
Local anesthesia with sedation offers anesthesia personnel and the surgeon great
flexibility in tailoring the degree of anesthesia to the needs of the patient. Procedures
that once required patients to stay overnight in the hospital now are performed safely in
office and outpatient surgical suites. The introduction of new anesthetic applications
enables patients to undergo lengthy and complex procedures as outpatients and then
promptly and safely be discharged home. The choice and route of anesthesia
administration is paramount to the patient's overall surgical experience. If the patient
upon discharge is alert, has minimal pain, and has no nausea or vomiting, then their
surgical experience is a positive one (Stoelting, 1989).
PREOPERATIVE SELECTION
The 3 modalities of administering anesthetic agents include local anesthesia, monitored
anesthesia care (MAC), and general anesthesia via an endotracheal tube or laryngeal
mask.
Appropriate patient selection begins with a meticulous medical and surgical history and
physical examination. Once the patient has been cleared for anesthesia, the surgeon
must determine if the proposed surgery can be performed effectively under MAC or if
general anesthesia is necessary.
Another critical factor contributing to the choice of anesthetic modalities to be employed
is the patient's attitude and affect. Some patients want to be "asleep" for the duration of
the surgery, fearing any pain or the chance of hearing what actually is being performed
during surgery. Other patients have trepidation toward general anesthesia and "having a
tube stuck down the throat." If the intravenous (IV) sedation is not going to be deep and
the patient is particularly anxious and not cooperative, this combination may prove
meddlesome during prolonged surgical procedures. The patient may become restless,
requiring more anesthetic agents for a deeper level of sedation than planned. A
resultant decrease in respiratory drive and possible compromise of patient safety may
occur during the procedure.
MONITORED ANESTHESIA CARE
MAC combines IV sedation with local anesthetic infiltration or nerve blocks.
Procedures such as otoplasty, facelift, blepharoplasty, or liposuction are examples of
surgeries routinely performed under MAC. Patients given monitored anesthesia rather
than general anesthesia experience fewer incidences of nausea and vomiting and
typically can be discharged home safely and quickly. The primary disadvantage of MAC
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is the lack of airway control and the threat of aspiration or obstruction. To minimize
these risks, the anesthesia personnel must titrate the medications carefully to maintain
spontaneous respirations while maintaining an anesthetic depth, allowing the patient to
remain comfortable. Careful selection and administration of medications is essential in
producing the desired and optimal intraoperative anesthetic effect and postoperative
outcomes.
LOCAL ANESTHESIA
Local anesthesia encompasses infiltration of the operative site, tumescent techniques,
and nerve blocks.
A nerve block can be labeled minor if one nerve is affected or major if more than one
nerve or conduction in a nerve plexus is impeded.
Local anesthetic agents are usually of the amino amides class and include such agents
as lidocaine, bupivacaine, prilocaine, mepivacaine, and etidocaine. The potency, onset
of action, and duration of these agents varies.
Depending on the area to be anesthetized, varying techniques can be implemented. For
incisional sites, a local anesthetic such as 1% lidocaine with EPI is ideal for direct
injection into the incisional site with rapid onset of the anesthetic effect. For procedures
in which flaps are to be elevated, as in a facelift or coronal forehead lift, the incision site
is anesthetized as previously mentioned, and the flap area can be infiltrated with a
diluted anesthetic such as 0.5% lidocaine with EPI.
For the local anesthetic, 1% lidocaine often is used with 1:200,000 or 1:100,000 EPI.
The latter prolongs the anesthetic effect of lidocaine as a result of its vasoconstrictive
properties. If more prolonged anesthesia is desired, lidocaine can be mixed with
bupivacaine, providing the rapid but shorter lasting anesthesia effect of the former
coupled with the slower but prolonged anesthetic effect of the latter.
In tumescent techniques, vastly larger amounts of anesthetic are used, albeit in dilute
concentrations. Adipose tissue is suffused via an infusion cannula in the subcutaneous
space, with large volumes of diluted lidocaine (0.05-0.1%) and a diluted concentration of
EPI (1:1,000,000) for both anesthetic and hemostatic effects. The safety of this
technique lies in the fact that the anesthetic concentration is extremely small, allowing
large amounts of solution to be used without reaching toxic levels. For example a
mixture of 500 mL of normal saline with 50 mL of 2% lidocaine will result in a
concentration of lidocaine of less than 0.2%. In addition, a tissue plane is created that
aids in later dissection.
Complications
Complications of local anesthetic agents can manifest as a localized reaction or
systemic adverse effects. The most common cause of such sequelae is secondary to
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accidental intravascular infiltration but systemic conditions also may increase the risk of
these untoward effects. Cardiovascular disease, hepatic and renal dysfunction, acidbase abnormalities, and hypoxia can amplify the possibility of anesthetic toxicity. In
addition, the very old, very young, and gravid females may respond aberrantly to these
agents.
Localized untoward effects include prolonged or permanent paresthesias, anesthesia,
and motor weakness. In addition, local vasoconstriction has been reported with
resultant necrosis.
Systemic adverse effects can result in angina pectoris, shortness of breath,
dysrhythmias, and cardiovascular collapse. Bupivacaine in particular has been
associated with decreased cardiac output and hypotension.
Disorientation, auditory and visual hallucinations, and decreased responsiveness,
including coma, are possible effects of CNS toxicity. Respiratory and cardiovascular
collapse and seizures also may emanate from CNS-induced toxicity.
Rash and other manifestations of allergic reactions (including anaphylaxis) can result
from local anesthetic agents. The amino amides are much less likely to cause immune
reactions because of their lack of para-aminobenzoic acid (PABA), as compared to the
amino esters, which are derivatives of PABA. Some amino amides do contain
methylparaben, a structural similar compound to PABA, which may account for the
resultant stimulatory immune effect of the amino amides.
Methemoglobinemia can result in respiratory drive irregularity, cyanosis, and graying of
the skin. Prilocaine mainly has been linked to this toxic effect as a result of its
metabolite acting as an oxidizing agent of hemoglobin.
Remain cognizant of the possibility of local anesthetic reaction to successfully manage
these untoward effects. If suspected, the injection should be terminated, the patient’s
airway should be assessed for patency, and supplemental oxygen should be
administered. Vital signs and pulse oximetry should be checked. If the patient is
desaturating, an airway should be secured through basic life support protocols. If this
proves unsuccessful, intubation and advanced cardiac life support protocols are
indicated. If hypotension or dysrhythmias occur, IV fluids, vasopressors, and
antiarrhythmic drugs should be employed.
Management of CNS toxicity is directed toward control of respiratory drive and halting
seizure activity. Benzodiazepines and succinylcholine are the drugs of choice to abort
seizure activity and decrease neuromuscular sequelae to facilitate airway control,
respectively.
MONITORED ANESTHESIA CARE - TECHNIQUE
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IV sedation may begin after IV access is secured, cardiopulmonary monitors are
applied, and oxygen is given via nasal cannulae.
Midazolam (Versed), a short acting, water-soluble benzodiazepine, is administered in 1mg bolus doses for its amnestic and anxiolytic properties. Midazolam, with a 2-hour
half-life, has limited cardiovascular effects, allows for expeditious recovery, and has no
postoperative sequelae such as nausea and vomiting.
Fentanyl, a rapidly acting narcotic analgesic, can be administered in boluses of 25- to
50-mcg increments for analgesia with little sedative effect. As with all narcotic agents,
respiratory function can be depressed, and the patient may experience nausea and
emesis.
A 10- to 20-mg bolus of ketamine, which produces dissociated anesthesia, can facilitate
tolerance to injection of local anesthetic agents. Serious cardiovascular adverse effects
and seizures have been reported along with psychotic reactions and nightmares.
Propofol (Diprivan) is a rapidly acting sedative and hypnotic agent. Propofol has
excellent effects with quick patient recovery. Given in 0.5-1 mg/kg injections that are
infused slowly prior to the injection of local anesthesia, propofol maintains respiratory
drive and allows the patient to tolerate the local anesthetic injections. A propofol
infusion, with a starting dose of as low as 25 mcg/kg/min throughout the procedure, can
provide smooth and constant anesthesia with the option of "deepening" the patient at
stimulating moments by administering boluses of 50 mcg of fentanyl, 10 mg of
ketamine, or 10 mg/kg of propofol.
Near the end of surgery, the propofol infusion must be titrated to “lighten” the patient
and must be turned off approximately 5 minutes prior to the end of the procedure. At
this time, the patient should be awake and following commands appropriately. Upon
transfer to the recovery room, IV fentanyl (25-50 mcg) or Demerol (12.5-25 mg) may be
given for postoperative pain or shivering.
Postoperatively, patients who have undergone MAC must be monitored for
cardiorespiratory function, bleeding, nausea, and pain. The rapidity of patient
recuperation depends on the length and type of procedure and on the type of sedation
employed. Another factor may be the overall patient tolerance to anesthetic agents and
the ability to metabolize these chemicals for excretion from the body. Concomitant use
of other pharmaceutical agents and body habitus can affect the rate of anesthetic
metabolism and overall tolerance to these agents.
For example, a patient who weighs 80 kg should receive a maximum dose of 550 mg of
lidocaine with epinephrine. If using 2% lidocaine, then the patient should not receive
more than 225 mL of this agent. The maximum doses of all anesthetic agents should be
committed to memory, allowing for the calculations as shown above. In addition,
medications such as the aminoglycosides, succinylcholine, and compounds that reduce
liver functions may increase the toxicity of local anesthetic agents.
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The patient should be questioned concerning problems with anesthesia in the past.
Using local anesthetics sparingly or avoiding certain compounds helps the clinician to
avoid toxic adverse effects.
ALTERNATIVES
Although MAC is a safe method for providing anesthesia, general anesthesia is
preferred for lengthy or complex procedures. General anesthesia provides amnesia,
analgesia, and muscle relaxation. In addition, the patient’s airway is secured with an
endotracheal tube or laryngeal mask, and the risk of aspiration or obstruction is
minimized. The primary disadvantage of general anesthesia is the increased incidence
of nausea and vomiting and the somnolence of patients postoperatively. However, in
properly selected patients, local anesthesia with MAC is a safe and effective method of
providing anesthesia for operative procedures.
REFERENCES
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Badrinath S, Avramov MN, Shadrick M, et al: The use of a ketamine-propofol
combination during monitored anesthesia care. Anesth Analg 2000 Apr; 90(4):
858-62.
Biswas S, Bhatnagar M, Rhatigan M, et al: Low-dose midazolam infusion for
oculoplastic surgery under local anesthesia. Eye 1999 Aug; 13 ( Pt 4): 537-40.
Hogan Q: Local anesthetic toxicity: an update. Reg Anesth 1996 Nov-Dec; 21(6
Suppl): 43-50.
Katzen LB: Anesthesia, anelgesia, and amnesia. In: Cosmetic Oculoplastic
Surgery, Eyelid, Forehead, and Facial Techniques. 3rd ed. 1999: 67-74.
Kendell J, Wildsmith JA, Gray IG: Costing anaesthetic practice. An economic
comparison of regional and general anaesthesia for varicose vein and inguinal
hernia surgery. Anaesthesia 2000 Nov; 55(11): 1106-13.
Nique TA: Introduction: The anesthetic continuum. In: Anesthesia for Facial
Plastic Surgery. 1993: 1-3.
Stoelting R, Miller R: Basic Anesthesia. 2nd ed. 1989: 417.
Thorne AC: Local anesthetics. In: Ashton SM, Beasley RW, Thorne CHM, eds.
Grabb and Smith's Plastic Surgery. 5th ed. 1997.
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Florida Heart CPR*
Local Anesthesia Assessment
1. The modalities of administering anesthetic agents include:
a. local anesthesia
b. monitored anesthesia care (MAC)
c. general anesthesia via an endotracheal tube or laryngeal mask
d. all of the above
2. This combines IV sedation with local anesthetic infiltration or nerve blocks.
a. Local anesthesia
b. MAC
c. General anesthesia
d. All of the above
3. Patients given ______ rather than _______experience fewer incidences of
nausea and vomiting and typically can be discharged home safely and quickly.
a. Monitored anesthesia / general anesthesia
b. General anesthesia / monitored anesthesia
c. General anesthesia / MAC
d. MAC / general anesthesia
4. Complications of local anesthetic agents can manifest as a localized reaction or
systemic adverse effects.
a. A localized reaction
b. Systemic adverse effects
c. Both A and B
d. Neither A nor B
5. Systemic adverse effects from complications of local anesthetic agents can result
in:
a. cardiovascular collapse.
b. angina pectoris
c. shortness of breath
d. all of the above
6. Postoperatively, patients who have undergone MAC must be monitored for pain
and:
a. Cardiorespiratory function
b. Bleeding
c. Nausea
d. All of the above
7. Although MAC is a safe method for providing anesthesia, general anesthesia is
preferred for:
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a. Lengthy procedures
b. Emergency procedures
c. Complex procedures
d. A and C
8. General anesthesia provides:
a. Amnesia
b. Analgesia
c. Muscle relaxation
d. All of the above
9. The primary disadvantage of ______ is the increased incidence of nausea and
vomiting and the somnolence of patients postoperatively.
a. MAC
b. Local anesthesia
c. General anesthesia
d. All of the above
10. The primary disadvantage of ____ is the lack of airway control and the threat of
aspiration or obstruction.
a. MAC
b. Local anesthesia
c. General anesthesia
d. All of the above
Florida Heart CPR*
Local Anesthesia