The Impact of Anesthetics on FLIP

Achalasia is a disease of unknown etiology in which inflammatory cells destroy ganglion cells in the wall of the esophagus.\[1,2 \] This inflammatory degeneration preferentially involves the inhibitory neurons in the esophageal myenteric plexus that are needed to effect normal peristalsis in the esophageal body and normal relaxation of the LES.\[3\] Thus, the classic manometric features of achalasia are: 1) absent esophageal peristalsis and 2) failure of the LES to relax with swallowing.\[4\] These physiologic abnormalities cause the typical achalasia symptom of dysphagia for both liquids and solids. No therapy is available to restore the lost esophageal ganglion cells in achalasia. Rather, treatments are directed at disrupting the LES muscle using invasive procedures that include pneumatic dilation, Heller myotomy, and per-oral endoscopic myotomy (POEM). In 2008, using the technique of esophageal high resolution manometry, Pandolfino et al. identified three subtypes of achalasia.\[5\] In all three subtypes, there is no peristalsis and the LES does not relax normally with swallowing \[recognized by an elevated integrated relaxation pressure (IRP) on high-resolution manometry\]. In Type I achalasia, swallowing results in little or no distal esophageal pressurization. In Type II achalasia, swallowing is associated with panesophageal pressurization to a level \>30 mm Hg. In Type III achalasia, swallowing is associated with spastic esophageal contractions. Patients with Type II achalasia have the best response to any form of achalasia treatment, whereas Type III patients have the worst response. In the aforementioned study, the investigators also identified a group of patients who had abnormal LES relaxation with swallowing (i.e. an elevated IRP), but who had some preserved peristalsis in the body of the esophagus.\[5\] The investigators proposed that this was probably a heterogeneous group of patients, some having a variant form of achalasia and others having a mechanical obstruction at the esophago-gastric junction (EGJ). This manometrically-defined condition in which there is an elevated IRP with preserved peristalsis is now called EGJ-outflow obstruction.\[6\] A subset of patients with EGJ-outflow obstruction is a form of achalasia, likely due to the same process that causes esophageal ganglion cell loss in classic achalasia. There are additional spastic disorders of the esophagus such as diffuse esophageal spasm and hypercontractile esophagus. Functional luminal imaging probe (FLIP) topography is a tool that has been increasingly helpful in characterization of patients with esophageal motor abnormalities, particularly those with achalasia, EGJOO and disorders with spastic elements.\[7\] In addition FLIP topography has been utilized to guide intervention and gauge adequacy of intervention pre and post myotomy. FLIP topography is now utilized in our standard algorithm for both diagnostic work ups of patients with motor diseases of the esophagus and during POEM procedures. During the course of some procedures, multiple FLIP assessments may be obtained for clinical purposes. These patients with esophageal motor disorders are at increased risk of aspiration. We often perform endotracheal intubation for these patients with esophageal motor disorders to protect the airway and decrease the risk of aspiration. A common anesthetic gas is sevoflurane is used in endotracheal intubation. However, sevoflurane affects esophageal motility based on preliminary data from abstracts\[8,9\] but the appropriate anesthetic protocol with FLIP assessment remains unknown. Alternatives to sevoflurane include isoflurane or Propofol only sedation or total intravenous anesthesia (TIVA). Propofol only sedation is not thought to impact esophageal motility. The impact of isoflurane is unknown. At our institution we have generally performed FLIP topography assessments OFF sevoflurane. During the course of an entire procedure, both on and off gas may be used depending on the procedure and discretion of the anesthesia team. The exact impact of each anesthesia approach on the FLIP assessments. To address the above-noted knowledge gaps in optimal sedation for FLIP topography achalasia and motility disorders of the esophagus, we propose to determine the impact of esophageal motility as assessed by FLIP topography.