Gastrointestinal motility drugs in critical illness

Gastrointestinal motility disturbances in critically-ill patients often require treatment with prokinetic drugs. The aetiology of motility disturbances is complex, and involves electrolyte imbalances, hypervolaemia, reduced intestinal secretion, adverse effects of drugs (catecholamines, opioids, or sedatives) and disease- or treatment-related changes of microflora. However, the choice of prokinetics is narrow, and the multiplicity of pathophysiological mechanisms often limits their efficacy. Gastroparesis can be managed with gastrokinetics such as domperidone, metoclopramide and erythromycin. Their choice depends not only on efficacy, but also on adverse effect profile. The arrhythmogenic potential of domperidone limits maximum daily dose and treatment duration. Metoclopramide and erythromycin induce tachyphylaxis, which restricts treatment duration. The combination of metoclopramide and erythromycin serves as rescue therapy in severe gastroparesis. Neostigmine and laxatives are used to manage colonic paralysis, and these treatment options may eventually be extended by drug candidates, such as prucalopride, lubiprostone, and linaclotide, whose utility in the ICU awaits to be evaluated. Neostigmine’s prokinetic efficacy in colonic paralysis is limited, but well documented in patients with acute colonic pseudo-obstruction (Ogilvie syndrome). Care is advocated in dosing because higher doses of neostigmine inhibit motility. Alternative options include osmotic and stimulant laxatives, especially for prophylactic use. The opioid receptor antagonist alvimopan is used for the short-term management of post-operative ileus, while methylnaltrexone is indicated in palliative care and chronic pain management. Since its efficacy in critically-ill patients remains to be proven, the use of methylnaltrexone in the ICU is off-label and requires proper documentation.