The Patient Undergoing Liposuction
Patients undergoing liposuction pose unique challenges in regard
to intraoperative fluid management. A major factor determining the amount of intravascular
volume changes during surgery is the type of liposuction being performed. Liposuction
can be an office-based procedure using minimal sedation and subcutaneous infiltration
of large volumes of dilute lidocaine and epinephrine solution. This is referred
to as the tumescent technique and tends to be used
to remove smaller volumes of fat (<3000 mL). Infiltration of large fluid volumes
is used to make the tissue firm and facilitate removal of adipose tissue. Because
of the smaller volumes of fat removed and less damage to subcutaneous tissue, the
tumescent technique has less risk of large fluid shifts. Semitumescent liposuction
tends to involve removal of larger volumes of fat, larger volumes of lidocaine plus
epinephrine solution, and more sedation. When a volume of more than 2000 to 3000
mL of fat is removed, the patient may require general anesthesia. These cases may
lead to life-threatening complications involving fluid management. Ideally, the
epinephrine in the tumescent solution decreases systemic absorption of the extremely
large volumes of fluid administered subcutaneously. However, if the fluid is not
removed before the effect of the epinephrine has worn off, the patient can absorb
a significant amount of the administered fluid. Case reports[138]
[139]
[140]
have
described the development of pulmonary edema after liposuction.
Further complicating the management of liposuction patients are
the large doses of lidocaine administered. During this procedure, patients receive
up to 70 to 80 mg/kg of lidocaine. Vasoconstriction and removal of most of the infused
solution is thought to prevent lidocaine toxicity.[141]
However, one report[142]
suggested that lidocaine
might impair alveolar epithelial fluid clearance. This impaired clearance of pulmonary
fluid in conjunction with increased intravascular volume from the absorbed solution
may explain some of the adverse occurrences, including death, reported after liposuction.
There are significant data to support the increase in the maximum dose of lidocaine
from the standard 7 mg/kg, but the maximum safe dosage of lidocaine for tumescent
liposuction is still an area of controversy.
The American Academy of Dermatology has published guidelines for
liposuction.[143]
The use of significant amounts
of intravenous sedation or analgesic administration was considered to be potentially
dangerous, particularly when conducted in an office-based setting. The recommended
maximum dose of lidocaine was 55 mg/kg. This increased dosage mandates proper preoperative
evaluation of patients' medications to determine whether they are using any drugs
that inhibit the cytochrome 3A4 or 1A2 system. These are the major pathways by which
lidocaine is metabolized, and even mild inhibition of these enzyme systems can lead
to potentially lethal serum lidocaine levels.
Controlled trials regarding the best method for performing liposuction
are lacking. However, a large body of practical knowledge suggests that liposuction
can be performed safely using large doses of lidocaine and large volumes of infused
solution. Vigilance regarding potential volume overload and pulmonary edema is required
to safely perform this procedure.
