**2. Mechanism of action**

The efficacy of the laparoscopic sleeve gastrectomy leading to sustained weight loss and improvement in comorbidities results from various mechanisms. First, owing to the reduction in stomach volume, there is a dramatic decrease in alimentary intake. Second, the orexigenic hormone ghrelin, which stimulates food intake, fat deposition, and the release of growth hormone, has dropped significantly. One of the primary goals of LSG is to eliminate the fundus, which is the primary source of ghrelin. Moreover, Glucagon-like-peptide-1, Peptide YY, and pancreatic polypeptide may also be factors involved in the mechanism of weight loss [8, 9]. Apparently, this mechanism is most likely multifactorial and still not fully clarified.

#### **2.1 Preoperative considerations**

LSG surgery is recommended for patients with a BMI greater than 40 kg/m2 or a BMI greater than 35 kg/m<sup>2</sup> and co-morbid diseases such as type II diabetes, hypertension, obstructive sleep apnea (OSA), non-alcoholic fatty liver disease, osteoarthritis, hyperlipidemia, or heart disease.

All patients considering bariatric surgery should undergo an adequate preoperative evaluation and workup including lab tests (complete blood count, basic metabolic panel, coagulation panel, HgA1C, thyroid function tests, vitamins, B-HCG for women), chest X-ray, and ECG [10].

Although upper GI endoscopy and abdominal ultrasonography are not routinely recommended, they contain important information that may affect the surgical plan. Concomitant hiatal hernia, esophagitis, H. pylori, and occult malignancies can all be evaluated using esophagogastroduodenoscopy. On the other hand, ultrasonography provides information about cholelithiasis, steatohepatitis, and other abdominal pathologies.

The evaluation of patients with gastroesophageal reflux preoperatively is controversial due to the conflicting results of LSG on reflux symptoms. There are studies in the literature claiming that LSG either improves or worsens reflux [11, 12]. Due to the risk of worsening the current situation and the need for revisional surgery, LSG is not the best option for patients with significant gastroesophageal reflux disease (GERD). The ASMBS released a statement declaring that severe GERD symptoms and Barrett's esophagus are relative contraindications to LSG [13]. Roux en Y gastric bypass, which has long been used as an anti-reflux procedure, should be recommended for this population.

Increased reflux symptoms after LSG can be associated with a concomitant hiatal hernia. There is an emerging consensus on concomitant hiatal repair [14]. According *Laparoscopic Sleeve Gastrectomy – Technical Tips and Pitfalls DOI: http://dx.doi.org/10.5772/intechopen.108997*

to the International Consensus Conference on Sleeve Gastrectomy, 84% of bariatric surgeons believe it should be repaired if present [15].

Smoking cessation and OSA management are critical for preventing respiratory complications in bariatric patients whose oxygen delivery to tissues may be compromised.

Furthermore, the following elements must be addressed: evaluation and optimization of comorbidities; consultation with a dietician, psychiatrist, and endocrinologist; and informed consent and thorough education regarding expectations [7].

#### **2.2 Anesthesia**

The procedure requires general endotracheal tube anesthesia. The anesthesiologist should be prepared for the possibility of difficult intubation, which is common in obese patients, and should have a flexible bronchoscope to assist with endotracheal tube placement.

### **3. Patient positioning and operative field**

The patient is positioned in reverse Trendelenburg and supine with both arms abducted and the legs split (French position). The patient is fixed to the operation table from both legs and the infraumblical site. The surgical covers and instruments are placed after the iodine wash of the abdominal skin. A 5-mm vessel sealer is prepared for dissection. A urinary catheter is not routinely placed. Patients are administered antithrombotic medication (enoxaparin) 12 hours before surgery in addition to sequential pneumatic compression stockings and prophylactic antibiotics.

The surgeon starts on the patient's right during trocar placement and then stands between the legs at the center. The assistant holds the camera with the left hand and uses grasper with the right hand on the patient's left and a nurse on the patient's right (**Figure 1**).

**Figure 1.** *Operative positioning.*
