Tissue temperatures during ultrasound-assisted lipoplasty

Removing excess subcutaneous fat with the assistance of ultrasonic energy has recently become a technique of interest in the United States after nearly a decade of use in Europe. There are a number of reported advantages of ultrasound-assisted lipoplasty over traditional liposuction, and there are also some theoretical concerns. Ultrasound-assisted lipoplasty involves the conversion of electrical energy to mechanical energy and transfer to the tissues through acoustic pressure waves, with the formation of heat as a by-product. Heat generated in this process dissipates through the body's own cooling mechanisms and conduction to the surrounding tissues, and it does not contribute to the clinical treatment of the adipose tissue. Reports of "burns" and ischemic skin injuries in the literature, and concerns for potential heat-related problems, prompted us to investigate whether significant temperature elevations occur in the clinical setting. Subcutaneous tissue temperature determinations during ultrasound-assisted lipoplasty were begun in February of 1996, and data were collected from 55 patients who had the procedure performed during a 6-month period. Intraoperatively, temperature measurements were made with a data-logging instrument and a needle microprobe inserted into the subcutaneous tissues. Temperatures were taken in the area of liposuction before the infusion of tumescent fluid, after tumescent fluid infusion, and at 5-minute intervals until the end of the procedure. The patient's core body temperature remained stable during the procedure within a narrow range (35.7 degrees C to 36.3 degrees C). There was a gradual increase in the temperature of the subcutaneous tissues over time during the application of ultrasonic energy; however, average subcutaneous temperatures remained below the core temperature (p < 0.05) at all time intervals. Room-temperature tumescent fluid further enhanced the thermal safety zone without lowering core body temperature. There were no temperature related complications in our study population and no untoward effects of performing temperature measurements. We conclude that there is no clinically significant elevation of subcutaneous temperatures during ultrasound-assisted lipoplasty. Reported ischemic skin complications are more likely the result of injury to the subdermal plexus rather than a temperature-induced thermal injury. Although heat is a natural by-product of the energy transfer involved in ultrasound-assisted lipoplasty, the risk of thermal injury is negligible when the procedure is performed by experienced operators. Complete understanding of the technique along with strict adherence to basic principles of flap vascularity will ensure safe and effective performance of ultrasound-assisted lipoplasty.