Extra Topic 2.1 -- Liposuction

Question 1

What is the body mass index (BMI)?

(A 36-year-old, 84 kg, female presents for suction assisted lipectomy of approximately 3000 mL of fat from the flanks and posterior thighs. Her past medical history is unremarkable. Medications include multivitamin and oral contraceptives.)

Answer 1

(Narrow River Question – Don’t just stop at kg/m²)

The body mass index (BMI) is defined as the patient’s weight in kilograms divided by the square of the patient’s height in meters.

The index is used to identify and classify overweight and obese individuals, and theoretically, indicate their associated risk of developing associated health problems (increasing risk with increasing BMI).

The BMI classification is as follows:

• Normal: 18.5-24.9 kg/m²
• Overweight: 25.0-29.9
• Obese (class 1): 30.0-34.9
• Obese (class 2): 35.0-39.9
• Obese (class 3): 4.0.0-49.9
• Superobese: >/= 50 kg/m2

Question 2

Is it important to know what liposuction technique is planned?

(A 36-year-old, 84 kg, female presents for suction assisted lipectomy of approximately 3000 mL of fat from the flanks and posterior thighs. Her past medical history is unremarkable. Medications include multivitamin and oral contraceptives.)

Answer 2

It is important because the morbidity and mortality associated with liposuction is different with different surgical techniques.

The most common technique is referred to as the tumescent technique, where large volumes of dilute lidocaine and epinephrine solution are injected into the subcutaneous tissues, and the amount of removed fat is usually less than 3000 ml.

An alternative technique, semitumescent liposuction, usually involves the removal of larger volumes of fat and is associated with a higher risk of fluid overload, pulmonary edema, local anesthetic toxicity, and fat emboli.

Newer liposuction techniques involving laser and ultrasonic energy to emulsify fat have a very low complication rate and are usually done under local or MAC anesthesia.

Question 3

What are your anesthetic concerns with this case?

(A 36-year-old, 84 kg, female presents for suction assisted lipectomy of approximately 3000 mL of fat from the flanks and posterior thighs. Her past medical history is unremarkable. Medications include multivitamin and oral contraceptives.)

Answer 3

I am concerned about the potential complications associated with this procedure and the patient’s morbid obesity.

Morbid obesity places the patient at risk for complications related to –

• airway management,
• patient positioning,
• pulmonary abnormalities (atelectasis, hypoxia, decreased functional residual capacity, increasing closing capacity, rapid desaturation with apnea),
• obesity hypoventilation syndrome (Pickwickian syndrome),
• obstructive sleep apnea,
• postoperative apnea,
• metabolic syndrome,
• type II diabetes,
• hypertension,
• coronary artery disease,
• stroke,
• altered drug affects,
• deep vein thrombosis,
• pulmonary embolism (from DVT),
• osteoarthritis, and
• nonalcoholic fatty liver disease.

Potential procedure specific complications include –

• perioperative fluid overload,
• pulmonary edema,
• local anesthetic toxicity,
• systemic epinephrine uptake,
• cardiac arrhythmias, and
• pulmonary embolism (from the procedure vs. a DVT).

Question 4

What is the toxic dose of lidocaine?

How much lidocaine is typically administered during liposuction?

(A 36-year-old, 84 kg, female presents for suction assisted lipectomy of approximately 3000 mL of fat from the flanks and posterior thighs. Her past medical history is unremarkable. Medications include multivitamin and oral contraceptives.)

Answer 4

Xtra Q: What additional steps could be taken to reduce the risks of L.A.S.T.?

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While the maximum safe dose of lidocaine with epinephrine is often reported as 7 mg/kg, it is understood that the total dose is only one factor among many that affect the likelihood of local anesthetic toxicity (other factors include the site of injection, the presence of vasoconstrictors, the pharmacologic properties of the local anesthetic, and individual patient risk factors).

The maximum safe dosage for tumescent liposuction is controversial, with patients routinely receiving 35 to 80 mg/kg.

Published guidelines for liposuction from the American Academy of Dermatology recommend a maximum dose of 55 mg/kg.

In any case, I would have a discussion with the surgeon concerning the planned maximum dosage and potential steps that could be taken to reduce the risk of local anesthetic toxicity, such as using diluted tumescent solution, adding epinephrine, and limiting the surgery to less than 3000 ml of fat removal.

Moreover, I would ensure the availability of a lipid rescue kit and carefully monitor the patient for signs and symptoms of local anesthetic toxicity (patients should be monitored throughout the perioperative period and for at least 30 minutes postoperatively since signs and symptoms of toxicity may be delayed for over 15 minutes following tumescent procedures).

Finally, I would perform a careful preoperative evaluation to identify patient factors that may increase the risk of toxicity, such as:

1. extremes of age (< 4 months or > 70 years),
2. cardiac disease (i.e. conduction defects, ischemic heart disease, and low cardiac output),
3. renal or hepatic dysfunction (decreased local anesthetic metabolism or hypoproteinemia),
4. hypoproteinemia (increased levels of free drug),
5. metabolic or respiratory acidosis, or
6. pregnancy (the mechanism of increased sensitivity to local anesthesia during pregnancy is not understood).

Question 5

How would you manage IV fluids during this case?

(A 36-year-old, 84 kg, female presents for suction assisted lipectomy of approximately 3000 mL of fat from the flanks and posterior thighs. Her past medical history is unremarkable. Medications include multivitamin and oral contraceptives.)

Answer 5

When managing fluids, I would take into consideration the amount of tumescent fluid used, urine output, and blood loss.

While the addition of epinephrine to tumescent solution helps to prevent excessive intravascular absorption of the large volumes of subcutaneous fluid, absorption may increase when the epinephrine wears off.

In fact, this subcutaneous fluid is absorbed over 48 hours postoperatively, and may lead to intravascular fluid overload, pulmonary edema, or congestive heart failure.

Therefore, I would keep IV fluid to a minimum, calculate the net fluid balance by subtracting the urine output from the IV fluids and tumescent solution infused, and consider IV furosemide if there were a positive fluid balance greater than 2000 ml.

Question 6

In the PACU, the patient is wheezing and complaining of shortness of breath.

What do you think is the cause?

(A 36-year-old, 84 kg, female presents for suction assisted lipectomy of approximately 3000 mL of fat from the flanks and posterior thighs. Her past medical history is unremarkable. Medications include multivitamin and oral contraceptives.)

Answer 6

There are several possibilities for why this patient is experiencing postoperative wheezing and shortness of breath.

Considering the patient’s obesity and the type of procedure performed, I would consider pulmonary embolism and pulmonary edema (fluid overload, congestive heart failure).

However, these symptoms could also be the result of bronchospasm, pneumothorax, aspiration pneumonitis, or a hypersensitivity reaction.

Therefore, I would go evaluate the patient, provide supplemental oxygen, auscultate all lung fields, review the fluid balance, and consider a chest x-ray.