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Per oral endoscopic myotomy (POEM) for achalasia

AMBER L. SHADA AND LEE L. SWANSTRÖm

HISTORY

Recent interest in natural orifice transluminal endoscopic surgery led to explorations of novel ways of exiting the gastrointestinal (GI) tract to perform extraluminal operations. One of these was submucosal endoscopy with a mucosal safety flap, which involved creating a submucosal tunnel before exiting the organ to minimize the chance of closure failure. Pasricha recognized the possibility this offered for endoscopic access to the circular muscles of the lower esophageal sphincter (LES), and used this approach to perform the first endoscopic myotomy in pigs in 2007. Subsequently, Inoue performed the first human per oral endoscopic myotomy (POEM) for achalasia in 2008. Since that time, POEM has been increasingly adopted as a technique to treat achalasia, and has expanded to the treatment of other esophageal motility disorders as well.

PRINCIPLES AND JUSTIFICATION

POEM is an effective treatment for all types of achalasia and has been reported for patients from age 3 to late 90s. It has been shown to be safe and effective for end-stage or “sigmoid” esophagus as well as reoperative cases. Aside from achalasia, POEM has been used for diffuse esophageal spasm (DES), hypertensive LES, spastic achalasia, and nutcracker esophagus.

The primary alternative approaches to the treatment of achalasia are either laparoscopic Heller myotomy or endoscopic balloon dilation. Injection of the LES with botulinum toxin (Botox) is regarded as a temporizing treatment due to its transient effectiveness. The advantages of POEM relate to its minimal access approach, resulting in less pain and shorter recovery. Additionally, the lack of dissection of the gastro-esophageal junction (GEJ) to access the LES may minimize the chance of postprocedure gastroesophageal reflux and avoid external adhesions that might compromise subsequent surgical treatments. A further important benefit of POEM is the ability to extend the myotomy proximally in cases of esophageal body spastic motility disorders.

POEM requires general anesthesia and is therefore contraindicated in patients with severe pulmonary disease, cirrhosis, portal hypertension, and coagulopathy. Additionally, prior esophageal or mediastinal radiation, or recent mucosal ablation or endoscopic mucosal resection is a contraindication. While previous Heller myotomy is not a contraindication, previous esophageal resection would probably be.

While not an absolute contraindication, we typically do not perform POEM for achalasia patients who have an associated significant hiatal hernia, as there is a high rate of reflux afterward. Also, it is probably not resource efficient to perform POEM on someone needing a concomitant laparoscopic procedure, unless they have an indication for an extended thoracic myotomy.

PREOPERATIVE ASSESSMENT

Achalasia patients should always have a comprehensive symptom assessment covering typical presenting symptoms including dysphagia, chest pain, regurgitation of undigested foods, weight loss, and previous interventions—all of which have been shown to affect outcomes of any treatments. The Eckardt score, a useful standardized symptom tool, can score patients to stratify disease severity and predict treatment success (see Table 42.1). Upper endoscopy with biopsies is essential to exclude pseudoachalasia related to infiltrative cancers. Upper GI barium esophagogram—preferably a timed barium swallow—serves as a roadmap for the operation, excludes significant findings like diverticula and serves as a baseline study for long-term patient follow-up. Although “heartburn” is a frequent complaint of achalasia patients, gastroesophageal reflux is physiologically extremely unlikely and thus 24-hour pH acid studies are not usually indicated.

Esophageal manometry is the single most important test, as it definitively establishes the diagnosis of achalasia. Introduced a decade ago, high resolution manometry (HRM) has increasingly become the gold-standard test, allowing classification of achalasia into three types that correspond as well to the degree of success following intervention: achalasia with minimal esophageal pressurization (Type 1, classic), achalasia with esophageal pressurization (Type 2), and achalasia with spasm (Type 3). Achalasia by definition is evidenced by complete loss of primary esophageal body motility and defective relaxation of the LES. Newer diagnostic modalities such as impedance planimetry have not been in use long enough to establish normal values and therefore are currently more intraoperative and research tools.

PATIENT PREPARATION

Preoperative informed consent should cover the following potential issues: possible anesthesia complications, esophageal perforation (salvageable with endoscopic approaches in the majority of cases), incomplete myotomy leading to continued dysphagia, inability to relieve symptoms (particularly if pain is a primary symptom), and postoperative gastroesophageal reflux.

Patients are prepared for surgery with 3 days of nystatin swish and swallow (given the high incidence of esophageal candidiasis in achalasia), and placed on a clear liquid diet 24 hours prior to surgery.

OPERATION

Anesthesia

General endotracheal anesthesia is always used, to better control carbon dioxide (CO₂) absorption and to compensate for elevation of the diaphragm from extravasated CO₂. Anesthesiologists should be reminded of the high risk for aspiration in achalasia patients and take appropriate induction precautions.

Positioning

1. The patient is positioned supine on the operating table with the left arm tucked at the patient’s side. The operating room table should be moved away from the anesthesia machine to allow the surgeon and assistant adequate room at the head of the table (see Figure 42.1). The surgeon will operate facing toward the patient’s feet, so the viewing monitor should be located at the foot of the bed, with the endoscope stack behind the surgeon. If using a scope cart with no secondary monitor, the endoscopic cart and monitor should be located across the table at the patient’s midbody. Pneumatic leg compression devices and forced-air patient warming should be used. Ready access to the chest and abdomen during the procedure is needed, most commonly for decompression of pneumoperitoneum or capnothorax.

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