Biomedical Engineering Reference
In-Depth Information
treating such areas (26). Some of the available technology now
takes thermal readings at the cannula tip as well as provides
skin surface temperature readings through an infrared ther-
mal monitor screen (SmartLipo MPX). Total energies utilized
for the laser range from 5000 to 60,000 J/cm 2 . Size of the treat-
ment location, the total amount of fat, the number of strokes,
distance of cannula placement from the skin and depth within
the fat layer, number of repeated cycle passes, and individual
surgical techniques prevent recommending an absolute num-
ber of kilojoules for each region. Reynaud has published
guidelines using a 980-nm diode laser (21). His average totals
for each area are listed here: 24,600 J for abdomen, 21,900 J for
back, 14,600 J for hip, 13,100 J for buttock, 8100 J for knee, and
10,400 J for inner thigh. The cumulative total for the subman-
dibular region seems a bit high, since we typically use about
50% of the total of 11,700 J reported.
After LAL is complete, the emulsifi ed fat may be removed by
aspiration with traditional liposuction or extrusion through
incision sites by gentle physician massage (24). One system
(CoolLipo) has integrated cannulas that allow for LAL and aspi-
ration simultaneously. Aspiration continues until the appropri-
ate body contour is reached. A pinch test is used at the conclusion
of the procedure to test for any contour irregularities.
Entry sites are left open for drainage and wound dressings
applied in a fashion similar to traditional tumescent liposuc-
tion. Patients wear compression bandages and/or garments
between 3 and 30 days depending on the area treated (12).
Patients may resume daily activities as tolerated, usually within
24 hours. Pain management usually requires only acetamino-
phen and, occasionally, a codeine-containing medication.
Patients can usually resume vigorous physical activity within
7 days. Postoperative physiotherapeutic treatments or lym-
phatic drainage massage is used by some to accelerate patient
recovery and enhance the clinical result (14,30).
likelihood of a thermal burn increases (14). In this same study
of 537 patients using a 1064-nm Nd:YAG laser, four skin burns
occurred (16).
Although the majority of reports on LAL indicate decreased
bruising as a distinct advantage over traditional liposuction,
one author has disputed this advantage with a case series and a
retrospective review (40,48). Three of 44 patients in one series
experienced severe ecchymoses, with tenderness lasting
beyond the resolution of bruising following LAL with an
Nd:YAG system (48). Lack also found a higher degree of
edema, ecchymosis, skin sensitivity, and pain in LAL patients
compared with those undergoing traditional liposuction,
although no statistical analysis was performed (40).
Blistering of the skin is a direct result of superfi cial thermal
damage. Superfi cial treatment more readily leads to epidermal
injury (26). Epidermal injury is typical when the skin surface
temperature reaches 47°C, with blistering at temperatures of
58°C or greater (26). However, in clinical practice, we have
witnessed epidermal blistering when surface temperatures are
far below 58°C. For this reason, continuous thermal monitor-
ing is necessary and the temperature end point should not
exceed 40°C.
In addition, the accumulated energy could be employed as a
surgical end point; however, few studies have tried to quantify
energy levels by treatment area. In addition, there is a wide
range of energy levels reported in the literature due to lack of
knowledge in early studies. In 2009, Reynaud and colleagues
reported their experience with 534 LAL procedures using a
980-nm diode laser (21). Data recorded during the 534 proce-
dures allowed for a calculation of the mean cumulative energy
applied for each location: 8100 J for the knee, 14,600 J for the
hip, 10,400 J for the inner thigh, 11,700 J for the chin, 12,800 J
for the arm, 13,100 J for the buttock line, 21,900 J for the back,
and 24,600 J for the abdomen. However, wide ranges of ener-
gies were identifi ed when the mean energy levels were calcu-
lated, with accumulated energies between 6000 and 51,000 J
while treating the abdomen. Other factors such as the treat-
ment area, the depth of cannula placement, and individual
techniques will also interfere with the fi nal accumulated
energy. Therefore, other clinical end points, such as palpation,
use of a handheld infrared temperature gauge, and integrated
internal sensing devices, should be used to avoid thermal
injury.
The presence of tumescent fl uid may provide some epider-
mal protection. According to Mordon et al., cooled tumescent
fl uid infi ltration decreases skin surface temperature greatly
(34). The large volume of tumescent fl uid used for anesthesia
serves as a large reservoir for heat transfer. Just as cooled
tumescent fl uid lowers the skin surface temperature, tumes-
cent fl uid heated by laser light from bioheat transfer could
produce epidermal heating, with increasing temperatures
occurring beyond the treatment time. For this reason, we
advocate close monitoring of skin surface temperatures with
an infrared temperature sensor or similar technology. We
often discontinue LAL in an area once a temperature of
38-40°C has been reached, knowing that the maximum tem-
perature may reach 41°C several minutes later. If this does
occur, we quench the area quickly with an ice bath.
A theoretical concern of LAL is its effects on serum lipid
levels. Laser-induced adipocyte rupture causes the release of
complications, adverse effects, and
precautions
The complication rate following LAL is extremely low in well-
trained hands, estimated at 0.93% according to a prospective
trial in 537 patients (16). A second large study by Chia and
Theodorou of 1000 consecutive cases of suction-assisted and
laser-assisted lipectomy under local anesthesia confi rms these
fi ndings (47). Ecchymoses, edema, and pain are the most com-
monly experienced adverse events (18,30), similar to those
expected following liposuction and usually mild in severity.
Paresthesias and hyperpigmentation have also been reported
(14,18). Rare side effects similar to liposuction-related compli-
cations are also possible including seroma, infection, neuropa-
thy, and minor contour irregularities. Touch-up rates following
laser-assisted liposuction are low, reported as 7.3% in one
study of laser-assisted and suction-assisted liposuction (47).
Adverse events can largely be avoided. Inappropriately high
laser settings resulting in high radiant energy, overly aggressive
tissue treatment with concentration in a single treatment area
for long periods of time all increase the risk of tissue hyper-
thermia and a risk of irreversible tissue injury (45).
Some of the most common adverse effects related to LAL are
often secondary to the heat produced by the laser fi ber, result-
ing in residual tissue damage (45). If the laser energy is inap-
propriately high, or the local temperature rises above 47°C, the
 
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