REGIONAL ANESTHESIA IN BARIATRIC SURGERIES

Abstract

The incidence of morbid obesity has tripled over the past three decades throughout the world. The WHO estimates that as of 2005, 1.6 billion people were overweight (defined as BMI 25–30 kg/m2) and 400 million obese (BMI>30 kg/m2). Bariatric procedures are classified according to their mechanism of action: restrictive, malabsorptive, or a combination of restrictive and malabsorptive. Restrictive weight loss surgery is based on decreasing gastric volume, with the creation of an early satiety sensation and delayed emptying. Examples include vertical banded gastroplasty (VBG), sleeve gastrectomy (SG), and adjustable gastric banding (AGB). Malabsorptive weight loss surgery alters the absorption of calories and nutritional principles obtained by bypassing parts of the bowel. Examples include biliopancreatic diversion (BPD) and jejuno-ileal bypass. The Roux-en-Y gastric bypass (RYGB) represents a combination of both techniques and can induce a weight loss up to 60 percent of the initial body weight. The anesthetic techniques applicable to bariatric surgery are general anesthesia or regional anesthesia, which is mainly in neuraxial form (spinal and epidural); or a combination of both. The use of other techniques, such as transversus abdominis plane (TAP) block, rectus sheath block, and thoracic paravertebral block, are also possible. Regional anesthetic techniques have been clearly linked to better pain relief and early discharge in patients with morbid obesity. These techniques can be either used to provide surgical anesthesia or aid in postoperative opioid-free analgesia. The techniques can be divided into central neuraxial blocks and peripheral nerve blocks. Regional anesthesia may have potential advantages compared to general anesthesia for select surgical procedures in obese patients. Even when general anesthesia is necessary, the addition of a regional anesthesia technique for postoperative analgesia may decrease requirements for supplemental systemic analgesics and therefore reduce the incidence of opioid-induced side effects. This may be particularly beneficial in obese patients with obstructive sleep apnea (OSA) syndrome. However, obese patients present technical challenges to the anesthesia practitioner due to unfamiliar surface anatomy and difficulty assuming positions optimal for procedural performance. Surface ultrasound is emerging as a useful tool for regional anesthesia in obese patients for preprocedural scanning to establish the site for needle insertion and target location or for real-time needle guidance. Because it may avoid some of the effects of general anesthesia as the patient remains awake and can protect the airway, regional anesthesia has some attractions in the morbidly obese patients. Moreover, complete relaxation of the abdominal musculature is provided which otherwise may be accomplished only with deep general anesthesia or high dosages of neuromuscular blocks. Metabolism of the anaesthetic agents is not a concern. Postoperative pain relieve can be provided avoiding the respiratory depressant effects of systemic narcotics.