**5. Discussion**

The basis of laser-tissue interaction is considered to be the photo-termal effect [6, 7]. The emitted laser light energy is absorbed by the tissue and converted into heat. When lower energy is applied, it changes the sodium-potassium balance on the cell membrane and promotes the cellular inflow of the extracellular fluid. On the other hand, when applying higher energy, membrane rupture occurs along with blood vessel and collagen coagulation [8]. For the latter to occur, internal subcutaneous temperature of 50°C should be achieved. Internal temperature should not exceed 65°C. That is considered to be critical end point temperature and higher temperatures lead to unwanted necrosis and subsequent scarring [6, 9]. DiBernardo and Reyes suggest that when performing superficial lipolysis to obtain skin tightening, the surface temperature should not exceed 47°C and should be limited to 42° C.8 The undominant hand should always control the surface temperature. That is why Mordon and Plot called the undominant hand, in this case, the "thinking" hand [10]. Different laser sources and wavelengths have been used for the lipolysis of the fatty tissue. Different wavelengths target different chromophore in the tissue so it has been hypothesized that specific wavelengths have better effect on fat disruption and other for skin tightening [11, 12]. Parlette and Kaminer reported that the 924 nm wavelength has the best fat absorption and thus, the highest fat melting potential [13]. On the other hand, there are authors that suggest that the heat and subsequently the histological damage and repair mechanisms are primarily responsible for the final result [14]. There are not many reports on the safety aspects of the applied energy. Reynaud et al. were the first to calculate the mean values of energy applied to different body areas in 2009. The machine used in their study was 980 nm diode laser. In their study conducted after 534 procedures were following: abdomen 24 600 J (6- 51 kJ), outher thighs 14 600 J (2.2- 31 kJ), waist 9 500 J (4- 19 kJ), posterior face of thighs 13 100 J (4- 25 kJ), inner thighs 10 400 J (4- 20 kJ), submandibular 11 700 J (6.6- 16 kJ), arms 12 800 J (4.7- 17 kJ), inner knees 8 100 J (2.7- 20 kJ), back 21 900 J (11- 35 kJ) [15]. In 2018, Ali published an article proposing parameters for safe and effective laser lipolysis. The average cumulative energy applied for each treated area were as follows: 2000-2500 J (chin), 8000- 12000 J (arm), 5000- 6000 J (gynecomastia in each side), 4000-5000 J (flanks), 10000-14000 J (abdomen), 12000-18000 J (back), 8000-15000 J (saddle bags), 10000-14000 J (thigh and 800-2000 J (knees). The study was conducted on 300 patients using 2 different Nd:YAG machines with incorporated dual wavelengths of 1064 nm and 1320 nm(Smart Lipo triplex Cynosure and DaVinci model Quanta) [16]. There are no scientific data to support the thesis but in authors' personal experience, larger amount of energy should be applied when working with diode laser. This observation is in concordance with the results of the previously mentioned studies. Mordon and Plot suggest that diode technology, in contract to Nd: YAG, has around 30% greater efficiency. They also suggest that higher wavelengths are better absorbed by fat and water therefore enable stronger heating. The latter, on the other hand, can increase the risk of thermal injury [10]. Wolfenson et.al suggest applying maximum of 5 kJ per 10x10cmof skin area treated in order to prevent complications of overheating [17].

Probably the greatest advantage of the laser-assisted liposuction is its ability to achieve significant skin tightening. Therefore, it is widely used in facial shaping, not just to achieve sculpting with fat removal but also to achieve rejuvenation effect. Given that, a term endolight lifting has been establish to describe the use of laser assisted liposuction as primarily rejuvenation procedure in the facial area. In 2011 Holcomb et al. have been first to publish the use of laser lipolysis on a larger series of patients. In total, 478 patients were treated with good final results [18]. In 2018,

#### *Laser-Assisted Liposuction in Face and Body Contouring DOI: http://dx.doi.org/10.5772/intechopen.99145*

Valizadeh et al. conducted a study on female patients seekng submental liposuction for fat reduction and skin rejuvenation. The patients were randomly assigned to two different groups: one treated with laser assisted liposuction and the other treated with traditional liposuction. The thickness of the submental fat was evaluated pre and postoperatively with ultrasound. The residual fat thickness was significantly lower in the laser assisted group at a 2 weeks follow-up with even greater difference at a 2 months follow up. Subjective patient evaluation was also performed using a subjective scale from 0 to 5. Patients treated with the laser assisted liposuction were considerably more satisfied than those treated with traditional liposuction in terms of fat reeduction and final skin appearance [19]. On the other hand, many patients who are candidates for liposuction have some amount of skin laxity. This method offers excellent alternative for those where there is no clear indication for skin resection surgeries but are in higher risk in being left with some skin sagging after the procedure. There have been subjective reports on skin tightening after the laser assisted procedures but DiBernardo and Reyes were first to prove it in 2009 [9]. Several analysis and studies have been conducted to explain and measure the skin tightening effect. According to mathematical analysis and thermoregulatory measurement, internal temperature has to be between 48 and 50°C to obtain skin tightening effect [6, 20–22]. Although many reports exist and studies have been conducted, to date, there is no consensus on the amount of skin tightening that can be achieved and the indications are left to the surgeon's subjective opinion according to his or hers experience. Therefore, the drawback of this technique is the surgeon's learning curve.

Blood loss during the procedures significantly influences patient's recovery period. Many studies showed the superiority of laser-assisted liposuction over the standard tumescent technique regarding the diminished blood loss [9, 17, 23, 24]. Abdelaal and Aboelatta have conducted a prospective study to evaluate the amount of blood loss and have concluded that laser assisted liposuction can reduce the blood loss up to 50%n comparing to the conventional liposuction [25]. The reduction of blood loss diminishes the risk of postoperative anemia and fatigue which significantly contribute to the patient's wellbeing through the recovery.

Various reports have also been published on the improvement of superficial skin irregularities such as cellulite. Petti et al. evaluated the cellulite improvement through the results on the modified Nurnberger-Muller scale 3-6 months after the laser assisted liposuction. An average improvement score was 1.58 on a scale from 1 to 3 suggesting significant satisfaction rate on the final esthetic appearance [26]. The authors have used laser-assisted lipolysis to treat skinny patient with localized cellulite with high satisfaction rate.

Disruption of the fatty cells with laser energy enables the use of cannulas of the smaller caliber. Thus, smaller entrance point can be made. Nevertheless, care must be taken not to injure the entrance site with laser energy. In that case, the resulting incision scar can be esthetically unpleasing. In the same time, the procedure puts less strain on the surgeon as it is not his or her hand and mechanical manipulations responsible for the adipose cell disruption. The latter is also responsible for inflicting less trauma to the tissue that also contributes to the faster recovery. In a fibrotic area such as the male breast or the tissue that has previously been traumatized with liposuction, laser lipolysis is an excellent tool to melt the entrapped fat without additionally traumatizing the tissue. That is why laser assisted liposuction is an excellent tool in treating pseudogynecomastia or contour irregularities form previous surgeries.

The biggest disadvantage of the laser assisted liposuction is the possibility of the thermal injury, burn, necrosis and unwanted scarring. As previously stated, some

reports on safety protocols have been made and can be used as guidelines when implementing the laser in one's practice [15, 16]. Generally speaking, when internal subcutaneous thermometer is incorporated in the machine one can precisely measure the temperature and avoid overheating. Unfortunately, not all the devices come with that equipment. As already mentioned, cold compresses and external thermometer can be used to avoid placing too much energy in one spot. In authors' experience, the use of the undominant hand to control the skin temperature is the best tool to avoid the thermal injury. Also, when starting to implement this technique, lower power settings and discontinuous waves can be used to avoid complications. One should bear in mind that in this situation the energy is applied from under the skin so any postoperative blistering (if not caused by the outside pressure from the garment) will surely result in full thickness necrosis.

If laser lipolysis without subsequent suctioning is used, postoperative mass formation is possible that on histological analysis is described as fluid-filled pseudocyst with characteristics of foreign-body granuloma [27]. Given that, the authors advise suctioning the liquefied fat whenever possible. Last, but not least, when suctioning is performed, there is less swelling and the final result is achieved sooner. The latter, in the end, contributes to the overall patient'satisfaction.

Another drawback of this technique is the increase in the operating time. Prado reported in their study that average duration of traditional liposuction was 45 min and the laser assisted one- 60 minutes [28]. Although there is an increase in the operating time, the overall procedure, especially the suctioning is easier to carry out compared to the traditional liposuction.

One case of acute kidney injury due to rhabdomiolysis has been reported [29]. Hence, the surgeon should avoid injuring the muscle aponeurosis during the procedure. Nevertheless, in patients presenting with symptoms of acute kidney injury postoperatively, he or she should react accordingly.
