Gastrointestinal Motility Problems in the Critical Care Setting
Gregory S. Sayuk
I. GENERAL PRINCIPLES
A. Gastrointestinal (GI) motility abnormalities are common in the intensive care unit (ICU) setting.
B. Motility problems are a consequence of multiorgan dysfunction, medications, and metabolic derangements.
C. As many as two-thirds of ICU patients are affected, predominantly with disordered gastric and colonic motor function.
D. Motility disorders manifest as gastric stasis (producing gastroesophageal reflux disease [GERD]), colonic dysfunction (abdominal distension, constipation), and diarrhea.
E. Typical signs and symptoms often are masked in the unresponsive or sedated patient.
F. GI motility complications prolong ICU stays and are associated with nearly a doubling of mortality risk.
II. ETIOLOGY
A. Critical illnesses.
1. Causes of gastric stasis (delayed gastric emptying, gastroparesis) include the following:
a. Neurologic (closed head, spinal cord injury).
b. Inflammatory (infection, sepsis).
c. Acute pain.
2. Medications resulting in decreased gastric transit.
a. Anticholinergic medications.
b. Sympathomimetics/pressor agents.
c. Narcotics.
d. Phenothiazines/antipsychotics.
e. Propofol.
3. Comorbid disorders.
a. Organ failure (cirrhosis, end-stage kidney disease).
b. Metabolic diseases (poorly controlled diabetes mellitus, hypothyroidism).
c. Prior gastric surgery and vagotomy.
d. Neurologic diseases (Parkinson disease, neuropathy).
e. Diseases that alter the mucosa (amyloidosis, scleroderma).
4. Metabolic derangements.
a. Electrolytes (hypercalcemia, hypokalemia, hypomagnesemia).
b. Hyperglycemia.
c. Acidosis/alkalosis.
5. Sympathetic neural stimulation often accompanies severe illness, resulting in selective suppression of excitatory motor reflexes and sustained intrinsic inhibitory neural overactivity.
a. Adverse outcomes from gastric stasis are the following:
i. Poor absorption of oral- or nasogastric-administered medications.
ii. Intolerance to enteral feeding.
b. Predisposition to GERD and its complications (e.g., dysphagia, GI bleeding); GERD is further exacerbated by supine positioning, use of nasogastric tubes, and mechanical ventilation.
i. Tracheobronchial aspiration and pulmonary compromise.
c. Causes of colonic dysfunction (distension, constipation) include the following:
i. Medications, metabolic disturbances, and medical comorbidity (see Section II.A).
ii. Infection, either systemic (pneumonia, sepsis) or GI (e.g., Clostridium difficile, cytomegalovirus).
iii. Ischemia (intestinal, cerebrovascular).
iv. Surgical intervention.
v. Autonomic imbalance accompanying medical and surgical illnesses.
vi. Supine positioning, as it is not conducive to voluntary elimination.
vii. The withholding or strict limitation of luminal nutrition, a major stimulant of colonic motor function.
viii. Combinations of factors, which may precipitate massive colonic dilatation or pseudoobstruction.
d. Diarrhea complicates as many as 1/3 of episodes of critical care. Its causes, evaluation, and treatment are presented in chapter 79.
6. Enteral feedings.
a. Of ICU patients receiving enteral nutrition, 40% to 60% develop diarrhea.
b. Hyperosmolar formulas, higher infusion rates, and colonic fermentation of malabsorbed carbohydrates have been invoked as etiologies.
7. Infections, including C. difficile, and in immunocompromised patients, opportunistic pathogens (e.g., cytomegalovirus, herpes simplex virus).
8. Medications (antacids, antibiotics, lactulose, sorbitol-containing medication suspensions).
9. Fecal impaction, with fecal overflow around the impaction.
III. DIAGNOSIS
A. Gastric stasis (delayed gastric emptying, gastroparesis).
1. Gastric stasis is suspected with impaired tolerance to gastric feeding, including clinical evidence of oral regurgitation or tracheobronchial aspiration (e.g., airway suctioning of enteral nutrition products).
2. Gastric residual volumes of 200 mL or greater suggest retention.
3. More reliable measurements of gastric emptying include scintigraphic techniques and octanoate breath testing, but are rarely performed clinically.
4. Mechanical obstruction is evaluated by upper endoscopy or radiographic imaging techniques (abdominal plain films, computed tomography [CT] scan).
5. GERD, as an outcome of gastric stasis, typically presents with heartburn and regurgitation, though critically ill patients may not endorse these symptoms.
a. Chest pain is an atypical GERD symptom, but mandates exclusion of cardiopulmonary explanations.
