Biomedical Engineering Reference
In-Depth Information
Oftentimes in laser resurfacing, propofol (Diprivan) is the
primary IV sedative agent used because it provides rapid
induction, easy maintenance, and quick termination. Analge-
sia is provided by fentanyl (Sublimaze) supplemented inter-
mittently with ketamine (Ketalar). To counteract the potentially
troublesome side effects of ketamine, as well as to provide
sedation and amnesia, all patients receive midazolam (Versed)
on initiation of IV access and the total dose of ketamine is lim-
ited to 1 mg/kg. This regimen decreases the risk of “bad
dreams” and adverse psychic experiences. In addition, Glyco-
pyrrolate (Robinul) can be used as a drying agent to help keep
the airway free of excess secretions.
After IV access has been secured, sedation is generally achieved
with midazolam at a dose of 0.05-0.1 mg/kg. Glycopyrrolate,
0.2 mg, and fentanyl, 1-2 mcg/kg, are given, followed by an ini-
tial dose of propofol, 1-2 mg/kg, to facilitate the placement
of the LMA. With the LMA in proper position and the
patient breathing spontaneously, propofol is administered in a
continuous infusion using an IV infusion pump in a dose of
100-300 mcg/kg/min. Supplemental oxygen may be supplied
from the circle system of an anesthetic machine or through tub-
ing from an oxygen cylinder at 2-4 L/min. If an anesthetic
machine is being used, N
2
O and anesthetic gases may also be
used; however, their addition may lead to an increased incidence
of postoperative nausea and vomiting. IV analgesia is provided
as needed with small doses of ketamine, 10-20 mg, and/or fen-
tanyl, 25-50 mcg. Continuous ECG, pulse oximetry, blood pres-
sure at 5-minute intervals, and continuous end-tidal CO
2
volume are used to monitor the patient. At the conclusion of the
laser resurfacing, the propofol infusion is discontinued, and the
patient rapidly awakens. The LMA is removed when the patient
is able to follow commands, usually within about 5 minutes.
The aforementioned anesthetic technique requires an ECG
machine, blood pressure monitor, functional suction appara-
tus, pulse oximeter, supplemental oxygen source, LMA, and
IV infusion pump. Capnography, although only optional for
anything other than minimal sedation, is desirable to monitor
the adequacy of ventilation. Any facility administering nar-
cotics or sedatives must have appropriately trained medical
personnel, a fully stocked resuscitation cart, intubation equip-
ment (laryngoscope, blades, ET tubes), a method for deliver-
ing positive-pressure ventilation (Ambubag or Jackson-Rees
circuit), and a charged and functional defibrillator. In addi-
tion, a recovery area staffed with qualified nursing personnel
should have the capacity to monitor ECG, blood pressure, and
pulse oximetry.
Even in a properly monitored environment, there has been
some concern over the safety of using lasers in close proximity
to oxygen. The use of opioids may require the use of oxygen to
maintain the pulse oximetry above 90%. Although modern
inhaled anesthetics are nonflammable, CO
2
and N
2
O are
combustible. Therefore, it is imperative that flammable liq-
uids and prep solutions not be used in the facial preparation.
The LMA and its pilot tube used to inflate the pharyngeal cuff
are both very resistant to damage from inadvertent laser
strikes, but green O
2
tubing is easily damaged by a few laser
pulses. However, the oxygen flowing through the tube will not
ignite. ET and LMA tubes can be fully protected by wrapping
them with saline-soaked gauze or towels. With proper tech-
nique and caution preventing combustible liquids near opera-
tive areas, laser resurfacing in the presence of oxygen and an
anesthetic delivery system, such as an ET or LMA, can be very
safe.
Conscious Sedation
Conscious sedation is defined as a depressed level of con-
sciousness during which a patient retains control over his
protective reflexes and can respond to commands. This type
of anesthesia is being used more frequently for outpatient
dermatologic and cosmetic surgery and is particularly rele-
vant in laser rejuvenation. Sedation renders a patient less
mobile than simply injecting a local anesthetic or using topi-
cally applied cream, thereby decreasing the risks of compli-
cations from the surgical procedure. A combination of
propofol, a nonbarbiturate anesthetic, and fentanyl, an opi-
oid agonist, is often used. The nonbarbiturate anesthetic
provides amnesia as well as mental detachment from the
procedure.
In a study, 20 patients received conscious sedation for proce-
dures, including dermabrasions, blepharoplasties, facelifts,
CO
2
laser resurfacing, and liposuction. First, each patient was
given 1 mg/kg IV of fentanyl. Then, the patient received an
initial bolus of propofol of 0.5 mg/kg followed by a infusion
rate at 150 mg/kg/min to achieve sedation. A total of 95% of
the patients reported a lack of pain from the procedure;
only two experienced nausea after the procedure. Other anal-
gesic choices include ketorolac (up to a total of 30 mg IV or
60 mg IM), phenoperidine, and pentazocine. Midazolam
(up to a maximum of 20 mg) has also been used as a short-
acting powerful sedative. Although this technique is designed
to maintain protective reflexes, it should be avoided in patients
who are at high risk for airway incompetence during sedation.
Basic monitoring should occur throughout the procedure,
including pulse oximetry, blood pressure, and ECG. Emer-
gency drugs and equipment must be available. Pulse oximetry
should be continued for about 20 minutes after the conclusion
of the procedure. Generally, the patient can then be discharged
after an hour with a responsible adult. Potential problems with
conscious sedation include oversedation, undersedation, and
drug reactions (86,87).
Propofol-Ketamine Technique with Opioid Avoidance
Opioid use has been associated with an 8.3% incidence of
postoperative nausea and vomiting when used with droperidol
and ondansetron prophylaxis. A retrospective study using pro-
pofol-ketamine anesthetic technique with opioid avoidance,
room air, and spontaneous ventilation indicates that this com-
bination may be an excellent anesthetic alternative for full-face
laser resurfacing. Patients in this study were given glycopyrro-
late 0.2 mg at the onset. Some patients then received 2 or 4 mg
of midazolam to reduce propofol requirements. Propofol was
administered as a dilute (5 mg/mL) solution in a 50-mL bag
connected via a 60 drops/mL IV set piggybacked into the most
proximal main IV port. The patients were titrated to a loss of
lid reflex and verbal response and then given a 50 mg IV bolus
of ketamine. Within 2 minutes, injection of local anesthetic
could begin. The main branches of the trigeminal nerve were
blocked with 2-5 mL of 2% lidocaine with 1:100,000 epineph-
rine (Fig. 16.6). One milliliter of this solution was also injected
into the zygomaticotemporal and zygomaticofacial branches.
Then, a field block of 1% lidocaine with 1:100,000 epinephrine
was injected along the entire perimeter of the face, and
