Regional Anesthesia for Bariatric Surgery

This ongoing column is authored by members of the International Society for the Perioperative Care of the Obese Patient (ISPCOP), an organization dedicated to the bariatric patient.

Column Editor: Stephanie B. Jones, MD

Dr. Jones is Associate Professor, Harvard Medical School and Vice Chair for Education, Department of
Anesthesia, Critical Care and Pain Medicine, Beth Israel
Deaconess Medical Center, Boston, Massachusetts.

This month’s installment by:Marilu Giacalone, MD; Shantale Cyr, PhD; and
Thomas M. Hemmerling, MSc, MD, DEAA

Dr. Giacalone is from the Department of Anesthesia, University of Pisa, Pisa, Italy. Drs. Cyr and Hemmerling are from the Department of Anesthesia, McGill University, Montreal, Canada.

Funding: No funding was provided.

Disclosures: The authors do not have any conflicts on interest relevant to the content of this article.

ABSTRACT
Bariatric surgery is a safe and effective way to lose weight. The aim of this review is to discuss the application of regional anesthetic techniques to bariatric surgery and evaluate their impact on patient management. Several options are applicable to bariatric surgery, including general anesthesia combined with regional techniques, regional techniques alone, and other forms of local blocks. The choice varies according to the type and duration of surgery, patient characteristics, and patient positioning. These techniques can improve analgesia and decrease side effects. Some techniques may also improve immunocompetence. Patients with obesity undergoing bariatric surgery may benefit from these factors for the enhancement of their postoperative recovery and an earlier return to normal life, allowing the renewed gastrointestinal order to show its biological effects. Regional techniques applied to bariatric surgery offer advantages in the context of the management of patients with obesity, taking into account the complexity and unique issues of caring for this patient population.

KEYWORDS
bariatric surgery, regional anesthesia, anesthetic techniques

Introduction
Obesity is a condition characterized by an excess of body fat and originates from an impaired energy balance. Obesity is defined as a body mass index (BMI) of 30 kg/m2 or more. Morbid obesity is defined as a BMI of 40kg/m2 or more or 35kg/mg2 or more in the presence of comorbidities.1

Bariatric surgery is generally indicated in the presence of morbid obesity when conservative measures were ineffective.2,3 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).[1,2] 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.[2,3] AGB, SG, and RYGB can be performed laparoscopically. In many cases, bariatric practice also comprises interventions aimed to correct the effect of the weight loss, such as abdominoplasty.

Regional techniques applied to bariatric surgery
What we can do. The anesthetic techniques applicable to bariatric surgery are general anesthesia; 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, rectal sheath block more mid-line incisions, and thoracic paravertebral block, are also possible. During the laparoscopic approach, patients need to be placed in a reverse Trendelenburg or lithotomy position, and general anesthesia and endotracheal intubation are the safest choices.[4] Multimodal regimens in analgesia include local anesthetics administered through the surgical ports or via wound infiltration.5 Intraperitoneal local anesthetic administration represents another option.[6,7]

In some situations, surgery is performed via an open approach. A combination of general anesthesia and epidural analgesia can improve analgesia.[8,9] It is recommended not to administer neuraxial opioids in patients with obstructive sleep apnea (OSA).[5] A combination of general anesthesia and spinal analgesia is another option for open bariatric surgery. continuous spinal analgesia, although rarely performed now, was seen to be effective in intra- and postoperative pain management in patients undergoing open VBG, allowing for earlier mobilization.10 In some selected patients, even neuraxial anesthesia alone can be a reasonable alternative (e.g., in patients with severe respiratory impairment[11] or with a history of difficult airway).[12,13]

Less invasive surgery (e.g. abdominoplasty) can be performed under spinal analgesia alone.[14] It also possible to use a TAP block[15] or local anesthesia with midazolam-fentanyl sedation.[16]

All the regional techniques applied to bariatric surgery share the objective of limiting the use of inhaled and intravenous anesthetics and opioids, which reduces respiratory and hemodynamic endangerment, and also reduces interference with the gastrointestinal tract, allowing the surgical interventions to show their biological effects. New forms of bariatric surgery are currently being studied, some of which act by inducing changes in the electrical gastric activity and are performed with a minimally invasive approach obtainable under sedation or local anesthesia.[17]

What we should know. The first goal of regional anesthesia applied to bariatric surgery is to cover the nociceptive and adrenergic stimulation originating from the manipulation of the gastrointestinal tract and the abdominal wall. The second goal is to guarantee adequate postoperative analgesia without interference with bowel motility, allowing early alimentation as well as mobilization, reducing the risk of thrombosis and respiratory infections. Achieving these goals can promote an early return to normal life for the patient, allowing early start of the postoperative weight loss program.[18]

The first step of caring for a patient with obesity is employing correct implementation of regional techniques. It is recommended to perform neuraxial blocks at least 12 hours after the administration of low molecular weight heparin (LMWH) to reduce the risk of hematoma. Removal of indwelling catheters should also occur at least 12 hours after administration of LMWH.[18]

The implementation of a neuraxial block in patients with obesity may not be easy as the palpation of bony landmarks, the ability of back flexion, the pattern of fat distribution, and anatomic variations play an important role.[19] When a difficult block is predicted (e.g., in the case of inability to palpate landmarks), the application of ultrasound (US) examination prior to the puncture can facilitate the execution of the block, enhance its success, reduce the risk of complications, and improve the quality of analgesia and patient satisfaction (Figure 1).[20–22] US examination in patients with obesity is impaired,[23,24] but the quality of images can be enhanced by the use of harmonic imaging or 3D-US.[23] Using conventional US, a low-frequency probe is recommended to avoid the attenuation of the US waves caused by fat tissue at higher frequencies.[24]
In every case, the minimization of procedural time is essential to improve the management of patients with obesity, who may not tolerate the position and have respiratory impairment, mainly if they received sedative intravenous premedication. Some studies indicate a lower dose of local anesthetics in patients with obesity either for epidural[25] or spinal[26] analgesia, based on the reduction of the epidural space due to fatty infiltration and increased abdominal pressure.[27] Other studies recommend standard doses.[28–30]

How to do it. Before a neuraxial block, the patient should be hydrated to compensate for the vasodilatation and the hypotension as a consequence of the autonomic block. A preload with 500 to 1000 mL of crystalloid solution is recommended.[31]

For spinal anesthesia, the sitting position with back flexion is the most suitable. This position is essential for the identification of the bony landmarks (i.e., iliac crest, scapula, spinous processes, intervertebral spaces). The availability of a US machine may help in the identification of the site of the puncture. Having a needle of a proper length increases the success of the procedure at the first attempt. The following formula can be used to help in the choice of needle size:
Lumbar puncture depth (cm)=1+17 weight(kg)/ height (cm)[32]

A free flow of cerebrospinal fluid from the tip of the needle identifies the subarachnoid space, after which the local anesthetic is injected. A slow injection can make the spread of the block more predictable.[31] Single-shot spinal anesthesia was described for addominoplasty.14 the injection even of just 13mg of bupivacaine in L3-L4 allowed to obtain a sensitive block until T6.

Epidural analgesia in bariatric surgery improves the quality of analgesia, prevents venous thrombosis, and allows an early recovery of bowel function.[3] It is usually accomplished by the preoperative placement of a catheter for the administration of local anesthetics and opioids, if needed, for bolus injections or continuous infusions. The patient can be sitting with the back flexed to obtain a reduced distance of the epidural space from the skin.[33] The patient may also be in a lateral position, according to preferences of the patient and the anesthesiologist (Figure 2). In one study,[34] an epidural catheter was placed under US guidance in patients undergoing various bariatric interventions (i.e., open and laparoscopic SG, RYGB, AGB). The epidural space was found at an average of 9.1cm from the skin at T6-T7 in most patients. Levels of T9-T10 and T10-T11 for laparoscopic AGB have also been used for sufficient analgesia.[35] Ropivacaine or (L-) bupivacaine are the local anesthetics of choice; ropivacaine has the advantage of causing less motor block.[18] An example of epidural infusion for postoperative analgesia is bupivacaine 0.1% and meperidine 1mg/mL with an infusion rate of 14mL/hour in patients who underwent gastric bypass.[8]

The TAP block is the injection of local anesthetics in the transversus abdominis plane, localized between the transversus abdominis and internal oblique muscles, which contains the nerves responsible for the sensitivity of the anterior abdominal wall.[36,37] The technique is performed by using the triangle of Petit and the iliac crest as landmarks. After raising the abdominal flap and the plication of the rectus abdominis, the needle is slowly advanced until the sensation of a loss of resistance. It is important to note that landmark guided TAP blocks are challenging to perform on patients with obesity. As the triangle of Petit can be difficult to locate in patients without obesity, it may be impossible to locate in patients with obesity; therefore, US-guided TAP blocks should be presented as a safer alternative.[38]

Next, local anesthetic is injected into the target space.36 A bilateral block provides analgesia from T8 to L1.[36,37] It can be used for abdominoplasties, with decreased pain scores and morphine consumption in comparison to the traditional therapy.[36,37] An example of anesthetic dose is 20mL of a mixture of bupivacaine 0.5 % and lidocaine 1% plus 0.2mL of epinephrine 1:1000 for each side.[36]

The intraperitoneal administration of local anesthetics can reduce autonomic reactions responsible for postoperative tissue damage with possible delayed recovery.[7] An application is the placement of an intraperitoneal catheter for continuous analgesia following laparoscopic ABG.[6] An infusion of bupivacaine 0.375% at 2mL/hour for 48 hours improves pain scores in comparison to placebo.[6] Another technique is pre-emptive analgesia through pre-induction (of general anesthesia), which includes administering intravenously ketorolac (30 mg), pre-incisional skin infiltration with 75mL of bupivacaine 0.25%, and block of the rectus fascia at the end of surgery using 75mL of bupivacaine 0.25%.[39]

Impact on patient outcome. Combined techniques (i.e., general and epidural anesthesia) improve pain management in open bariatric surgery allowing earlier mobilization[8] and avoiding thrombotic and infectious sequels. They do not interfere with respiratory function intra- or postoperatively.[40,41] Regional anesthesia alone can be a safe and effective alternative[11–13] in selected patients with obesity and for specific types of surgery. Regional techniques show better pain management with less use of opioids in comparison to traditional techniques and may decrease the level of stress, the hospital stay, and length of recovery after surgery. Regional anesthesia has also been shown to preserve immune function better than general anesthesia and opioids.[18]

Conclusion
The complexity of the bariatric patient dictates the choice of safe anesthetic strategies that minimize the stress related to the operation. Many options are available, including combined techniques, neuraxial anesthesia alone, and emerging techniques, such as TAP block and local administration of anesthetics. For laparoscopic operations, in the absence comorbidities of a marked extent, general anesthesia and multimodal intravenous analgesic regimens are a reasonable choice. In the case of open surgery, combined techniques, such as general-epidural or general-TAP block are useful and can allow patients with obesity to recover quicker after surgery.

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Funding: No funding was provided.

Disclosures: The authors do not have any conflicts on interest relevant to the content of this article.

Author affiliation
Dr. Giacalone is from the Department of Anesthesia, University of Pisa, Pisa, Italy. Drs. Cyr and Hemmerling are from the Department of Anesthesia, McGill University, Montreal, Canada.

Address for correspondence
Prof. TM Hemmerling , Dept. of Anesthesia, Division of Experimental Surgery, McGill University, Arnold and Blema Steinberg McGill Medical Simulation Centre, Montreal General Hospital, C10-153, 1650 Cedar Avenue, Montreal, H3G 1A4, Canada

Category: Anesthetic Aspects of Bariatric Surgery, Past Articles