Background: A number of plastic surgeons have advocated using hypotonic solution in ultrasound lipoplasty, theorizing that induced adipocyte swelling increases membrane susceptibility to ultrasonic disruption. Additionally, it has been theorized that potassium increases membrane permeability. This study aimed to determine the effect of solution osmolality on adipocyte diameter, the time course of hypotonic solution action, and the effect of potassium addition on adipocyte diameter.
Methods: Base solutions with three different osmolalities were prepared: normal saline (NS) (154 mOsm/l), 1/2NS (77 mOsm/l), and 1/4NS (38.5 mOsm/l). Each solution was modified to contain 0, 5, and 10 mEq/l of potassium and adjusted to starting osmolality. Adipocytes of six patients were suspended in the nine solutions, and diameters were determined at 0, 15, 30, and 45 min. Diameters were measured using imaging software (Kodak ID 3.6).
Results: At time 0, the average adipocyte diameter was 79 +/- 8 microm, and no difference was seen in any of the solutions. Cells in the NS group showed no significant increase in diameter over 45 min. The 1/2NS group achieved an 8% +/- 1.9% increase in diameter at 45 min (p < 0.05). The 1/4NS group showed an increase by 14% +/- 2.4% (p < 0.01) at 15 min, and 15% +/- 2.3% (p < 0.01) at 45 min. Potassium had no independent effect on cell diameter.
Conclusions: Hypotonic solution can significantly increase human adipocyte diameter. The findings showed that 1/2NS had a significant effect within 15 min. Tumescent solutions with an osmolality of 1/4NS may be useful in facilitating ultrasonic lipoplasty.