Fiber and fluid administration and the risk of constipation in critically ill adults on mechanical ventilation: A prospective cohort study

Constipation is a common complication in critically ill patients and has been associated with adverse clinical outcomes. However, the role of enteral nutrition composition, particularly fiber and fluid administration, remains unclear. The aim of this study was to evaluate the association between dietary fiber and fluid administration and constipation in invasive mechanical ventilated critically ill adults.

We conducted a prospective cohort study including 74 critically ill adults requiring invasive mechanical ventilation and enteral nutrition. Patients were followed for up to 144 h from initiation of mechanical ventilation. Fiber and total fluid administration were evaluated as time-varying exposures. Constipation was defined as absence of defecation within 144 h. Discrete-time survival analysis was used to assess associations.

Constipation occurred in 54% of patients. Time to first defecation ranged from 48 to 504 h. Most patients (97.3%) received early enteral nutrition, although fiber and fluid delivery were frequently below guideline-recommended targets. No significant association was observed between fiber intake or fluid administration and constipation after adjustment, with results expressed as odds ratios (ORs) and 95% confidence intervals (CIs) (fiber: OR = 1.17, 95% CI: 0.41-3.38; fluids: OR = 1.40, 95% CI: 0.29-6.84).

In critically ill patients receiving invasive mechanical ventilation, fiber and fluid administration were not associated with constipation. These findings may reflect limited exposure during the early phase of critical illness, when gastrointestinal dysfunction is more strongly influenced by disease severity and pharmacological factors.