Post-extubation polyuria: characterization of an underrecognized phenomenon in a proof-of-concept study

The transition from invasive mechanical ventilation (MV) to unassisted breathing involves significant physiological changes for patients admitted to Intensive Care Units (ICUs). Discontinuation of MV impacts not only the respiratory system, but also affects hemodynamics and fluid balance. We aimed to assess whether urine output changes following extubation.

A prospective study was conducted at CASMU Medical Center (Uruguay). We included adult patients who required invasive MV for 1 to 15 days in the ICU and were subsequently extubated and placed on conventional oxygen therapy. Urine output was documented for the 48 h before and after extubation.

The study included 60 patients, with a median age of 58 (32-70) years, that received invasive MV for 3 (2-4) days. Following extubation, diuresis increased from 2.1 (1.4-3.1) L/day to 3.2 (2.3-4.6) L/day (P < 0.001). Polyuria (diuresis >3 L in 24 h) was present in 16 (27 %) patients during MV, compared to 34 (57 %) patients after extubation (P < 0.001). Urine output (relative to pre-extubation values) persisted significantly elevated for up to 30 h after discontinuation of MV. The increase in diuresis following extubation was correlated with the level of positive end-expiratory pressure administered during MV (r_s = 0.368; P = 0.004). Increased diuresis was not associated with hemodynamic or renal function impairment.

Discontinuation of MV was associated with a significant increase in urine output. This observed post-extubation polyuria may represent a physiological response to changes in intrathoracic pressure and fluid redistribution, and warrants further research to explore underlying mechanisms.