Constipation in critically ill patients: much more than we imagine

Constipation is a common complication in critically ill patients, but there is limited information available in the literature on this disorder. A number of factors increase the frequency of constipation among patients admitted to intensive care, such as shock, the use of sedatives and opioid agents, electrolyte disturbances and changes in diet.(1,2) The incidence of constipation in the intensive care setting varies widely among studies, and it can range from 5 to 83%.(1-5) Such variation is directly related to the lack of a precise definition. In the guidelines of the American Gastroenterological Association, constipation is defined as fewer than 3 bowel movements per week, feelings of incomplete evacuation, hard stools, difficulty passing stools or the need for manual maneuvers for rectal emptying.(6) Some of these criteria, however, are subjective and difficult to apply in critically ill patients undergoing mechanical ventilation. Published studies on the topic mainly use the frequency of bowel movements during hospitalization or the time between admission to the intensive care unit (ICU) and the first bowel movement as the primary factors that define constipation among critically ill patients.(1,2,4,5,7,8) By understanding the incidence, pathophysiology and consequences of constipation in critically ill patients, strategies for prevention and treatment of this complication can be developed. As already mentioned, constipation has multiple potential causes, but its consequences are not well defined. Constipation could be associated with increased intra-abdominal pressure, reduced nutritional intake, bacterial hyperproliferation, injury of the intestinal mucosa and bacterial translocation through the injured mucosa. Patients who develop constipation often have gastroparesis and paresis of the ileum, conditions that hinder the progression of nutritional support. The resulting inadequate nutritional intake may result in a worse prognosis by reducing the patient’s overall muscle strength and functional capacity, reducing the ability to synthesize new tissues and wound healing, increasing the number of infections and increasing the time of hospitalization and the morbidity and mortality. Constipation may be associated with a longer time on mechanical ventilation.(1,5) Abdominal distension may hinder the action of the diaphragm, decrease lung compliance and increase respiratory effort.(2) In some patients, constipation may be associated with increased intra-abdominal pressure, with consequent reductions in lung compliance and increases in intra-thoracic and pleural pressure, which can cause edema and atelectasis. Constipation is more than an intestinal motility problem or even an epiphenomenon in critically ill patients; it may be part of a broader context of acute intestinal dysfunction. Acute intestinal dysfunction is common among critically ill patients, but it can be difficult to diagnose because of Rodrigo Palácio de Azevedo1, Flávia Ribeiro Machado2