Vancouver, British Columbia — The duration of lipoplasty surgery should generally be limited to six hours or less, says Peter Fodor, M.D., president of the American Society for Aesthetic Plastic Surgery (ASAPS). Lipo-plasty has been used for more than 25 years. However, little study of the physics of the mechanical components involved in the procedure prompted Dr. Fodor to carry out a laboratory-model and a clinical study investigating canisters, tubing and cannulae, in order to derive recommendations for the clinicians.
Using an applesauce and tap water mixture, Dr. Fodor and his group of investigators, including Dr. William Cimino, Ph.D., studied the components incorporated in lipoplasty systems. Among other things, the researchers compared small and large commercially available canisters for their evacuation time. The doctors also investigated different diameters and lengths of tubing and cannulae.
Smaller canisters evacuated fluids faster than larger ones, and larger-diameter cannulae extracted fluids faster than smaller instruments. Venting cannulae facilitated extraction if there was a continuous flow in the tubing, he says. Cannulae with small multiple ports were 24 percent faster than larger ones, although this varied depending on the ratio between the cannulae and the lumen area, he adds."We saw that when the port area exceeds greater than 1.5 times the cross-sectional area of the lumen of the cannulae, the flow rate was not further increased," he says.
Multiple smaller ports accelerated extraction. Sharp-edged ports, which cause greater trauma are not recommended.
"Canisters are an important, but an often overlooked aspect of the lipoplasty system," Dr. Fodor says. Canisters should be visible to the surgeon, paired as left and right and readily exchangeable during the procedure, he adds.
The vacuum pump's gauge should be visible to the operating team. An inline filter prevents splash reaching the moving parts of the pump. Suction tubing should be flexible, lightweight and optimally 10 to 12 feet long. In addition, 3/8 inch internal diameter is adequate for most flow rates, he says.
Dr. Fodor concludes that "bench data can provide insights into clinical settings and the ideal lipoplasty systems should be designed to make best use of the physics of the components."
Although liposuction is still very safe, patients exhibit tremendous variation in response and absorption of lidocaine, and objective data is needed to reassure those undergoing the procedure, says Jeffrey Kenkel, M.D., associate professor and vice chair, department of plastic surgery at the University of Texas Southwestern Medical Center.
"Despite its popularity, liposuction remains a mystery," Dr. Kenkel says, noting there have been persistent, poorly understood problems with thermoregulation.
Dr. Kenkel studied five female patients, aged 29 to 40, who underwent a three-stage ultrasound-assisted lipoplasty technique. Using a Swan ganz catheter, he monitored the patients' vital signs every two hours for 24 hours, and he drew blood samples hourly during surgery and every four hours for 48 hours post-op.
The patients experienced a gradual decrease in mean arterial pressure, increased cardiac output until the catheter was removed post-operatively, increased stroke volume and a drop in systemic vascular resistance.
Epinephrine levels demonstrated a bimodal peak, but Dr. Kenkel notes its very short half-life.
"Is this endogenous epinephrine or exogenous epinephrine? Normally we would see a ratio of 45:1 intra-operatively," he says. However, in a reversal of the normal ratio during surgery, 25 percent of the epinephrine was absorbed. This resulted in a statistically significant linear relationship between the significantly increased cardiac output — sometimes two- to three-fold — and epinephrine absorption. CVP measurements were unchanged.
"Why are we seeing this increase in cardiac work?" Dr. Kenkel asks, noting that in addition to the stress of the procedure, about one-third of patients undergoing liposuction have pre-operative iron deficiency anemia. Normal patients may not experience much change in hypertension, but older patients will, he adds.