Chapter 41: Effects of Anesthesia on the GI Physiology

INTRODUCTION

This chapter will cover clinical considerations concerning gastrointestinal physiology as it pertains to the practice of anesthesia. Appreciation of normal physiology, as well as pathological states of the gastrointestinal system, is critical to ensure a safe anesthetic and in management of patients with complex related disease states. Common diseases and conditions such as obesity, inflammatory bowel disease, and gastroesophageal reflux are discussed in detail in this chapter.

CLINICAL ANESTHESIA CONSIDERATIONS OF GASTROINTESTINAL DISEASE

Obesity and Morbid Obesity

Obesity is linked to many factors, including low metabolism, excessive calorie intake, inability to feel full, psychological factors, genetic predisposition, general factors, and cultural influences. Health consequences of severe obesity include high blood pressure, diabetes, heart disease, joint and bone problems, sleep apnea, decreased self-esteem, decreased mobility/daily function, and decreased longevity. In this regard, obesity through increased peptide growth factors and reproductive hormones is a risk factor for many cancers. Body mass index (BMI) is defined as weight (kg)/height (m²). A desirable BMI is in the range of 18 to 25; however, 1.9 billion people internationally have a BMI of 25 to 30, which is considered overweight.^1,2 Thirty-four percent of U.S. adults older than 20 years are overweight while 35% are considered obese (BMI 30−40) as per reports from the Centers for Disease Control and Prevention. BMI ≥40 is termed morbid obesity, while BMI ≥50 is superobesity, and BMI ≥60 is supersuperobesity, respectively.

As mentioned, obesity can cause pulmonary, cardiovascular, neoplastic, gastrointestinal, musculoskeletal, and endocrine complications. Pulmonary complications include obstructive sleep apnea (OSA), restrictive lung disease, and reduced residual lung capacity. Cardiovascular and cerebrovascular complications include right-sided heart failure, hypertension, and stroke. Obesity is also associated with breast and colon cancer. Gastrointestinal complications include gastroesophageal reflux, liver disease through fatty liver, and fibrosis, as well as hiatal hernias. Musculoskeletal complications include osteoarthritis and chronic back pain. Endocrine complications include impaired fertility and reproductive hormone imbalances. Depression is also associated with obesity. Though beyond the scope of this chapter, each disease often results in medications which can have potential interactions with anesthetics and/or undesirable effects such as the increased risk of bleeding.

Metabolic syndrome is a result of a combination of obesity complications, including abdominal obesity, hypertension, insulin resistance, atherogenic dyslipidemia, as well as a proinflammatory and prothrombotic state.³ Diagnosis is via at least three of the following: hypertension, increased fasting blood glucose, abdominal obesity, decreased high-density lipids, and increased triglycerides. Metabolic syndrome predicts 25% of new-onset cardiovascular disease and, therefore, diagnosis and treatment of this condition are imperative.

Treatment options for severe obesity include diets (which are rarely successful), medications, exercise programs, behavioral modification, and surgery.

Perioperative Management

Obese patient considerations include issues with intravenous access, positioning, endotracheal intubation, noninvasive blood pressure monitoring, and emergence from anesthesia.^1,4 Peripheral lines ...