Scientific Basis for Hypotonic Tumescent Liposuction

Scientific Basis for Use of Hypotonic Solutions with Ultrasonic Liposuction

Angela Y. Song, MD, Jennifer M. Bennett, MS, Julio A. Clavijo MD, PhD, William Cimino PhD, J. Peter Rubin, MD.

Many plastic surgeons have promoted the use of hypotonic solutions in conjunction with suction lipectomy or ultrasound assisted lipectomy. The theoretical advantage of these solutions is that induced adipocyte swelling will increase the stress on the cell membrane, making it more susceptible to disruption by ultrasound energy. However, the optimal tonicity of injectable fluids for increasing adipocyte size is currently unknown. Additionally, potassium has been theorized to increase cell membrane permeability.

In our study, we aimed to determine: 1. The effect of tumescent solution osmolality on diameter of adipocytes isolated from fresh human abdominal subcutaneous tissue; 2. The time course of change in adipocyte size while exposed to hypotonic solution; and 3. The differential effect of adding potassium to the solutions.

Method: Base solutions with three different osmolalities were prepared for the study: Normal saline(NS) (154 mOsm/L), ½ NS(77 mOsm/L), and ¼ NS (38.5 mOsm/L). Each base solution was further modified to contain 5, and 10 mEq/L of potassium, and free water was added to adjust to starting osmolality. This resulted in a total of nine different solutions.

Adipocytes from abdominal subcutaneous tissue of six patients(mean age = 46) were isolated by collagenase digestion. Adipocytes were suspended in each of the nine solutions, and fat cell diameter determined at 0, 15, 30, 45 minutes. Digestion was performed by placing 5g samples in 15 mg of collagenase/3.5% BSA for 20-30 minutes in a 37°C, at 115 rotations/min, and centrifuged at 1000 RPM for 10 minutes. The fatty supernatant underwent second centrifugation. 100 µl aliquots were extracted from the middle adipocyte layer and stabilized in isotonic solution prior to experimentation.

Cell sizing was performed using a 100X light microscope (Fig. 1). Digital images of a field containing 50-100 adipocytes taken at a standardized focal length, and diameters of the individual cells measured utilizing image software (Kodak ID 3.6®).

Results: Average adipocyte diameter was 79µm + 8µm at time 0. No significant difference in cell diameter was seen at time 0 in all solutions tested. Cells suspended in NS showed no significant increase in diameter over a period of 45 minutes (Fig. 2). Cells suspended in ½ NS achieved an 8% increase in diameter at 45 minutes (p < .05). The ¼ NS group had the most profound impact on cell diameter, increasing by 14%(p < .01) at 15 minutes, and 15%(p < .01) at 45 minutes (Table 1). Potassium, as an independent variable, had no effect on cell diameter.

Conclusions: Hypotonic solution can significantly increase human adipocyte cell diameter. The effect of quarter normal saline, a standard, commercially available fluid, has a significant effect on cell diameter within fifteen minutes. Therefore, a tumescent solution with an osmolality of ¼ NS may facilitate ultrasonic lipoplasty.

Figure 1: Sample Microscopic Field of Adipocytes in Suspension

Fig. 2: Adipocyte diameter at baseline, and at 15, 30, and 45 minutes after immersion in NS, ½ NS, and ¼ NS.

NS ½ NS ¼ NS

t = 15 minN N Y

t = 30 minN N Y

t = 45 minN Y Y

N = Not Significant Y = Significant, p < .05

Table 1. Effect of Solution Type and Time of Immersion on Adipocyte Diameter

References

1. Tchoukalova YD, Harteneck DA, Karwoski RA, Tarara J, Jensen MD. A quick, reliable, and automated method for fat cell sizing. J Lipid Res. 44: 1795-1801, 2003.

2. Adama C, Mazzocchi M, Rossi A, Suderi N. Ultrasonic liposcupturing: extrapolations from the analysis of in vivo sonicated adipose tissue. Plast Reconstr Surg. 100(1): 220-226, 1997.

3. Hoefflin SM. Lipoplasty with hypotonic pharmacologic lipo-dissolution. Aesthetic Surg J. 22: 573-5776, 2002.