Spontaneous diuresis as a marker of successful liberation from positive pressure ventilation: A retrospective...

Positive pressure ventilation (PPV) alters hemodynamics and neurohormonal regulation, leading to sodium and water retention. Transition to unassisted breathing is expected to reverse these effects, but the magnitude and clinical relevance of this have not been fully characterized.

We conducted a retrospective observational study of adult ICU patients, who underwent planned PPV discontinuation (PPVdc). Patients receiving dialysis or intravenous furosemide within ±24 h of PPVdc were excluded. Changes in urine output (UO) and mean arterial pressure (MAP) were analyzed for the entire cohort and compared between successful versus failed PPVdc.

687 patients met the eligibility criteria, of whom 587 (85 %) had successful PPVdc. Mean hourly UO increased significantly in the 6 h following PPVdc (118.2 ± 76.8 mL/h vs 85.7 ± 48.1 prior to PPVdc, p < 0.01) and during the 24 h following PPVdc (108.9 ± 54.7 mL/h vs 87.5 ± 43.0 prior to PPVdc, p < 0.01). MAP rose concurrently by 8-10 % over the same periods (p < 0.01). UO increases were significantly greater in successful compared with failed PPVdc at 6 h (adjusted difference = +18.8 mL/h; 95 % CI +4.5 to +33.1; p = 0.01)., findings further confirmed by propensity score-matched analysis.

PPVdc was associated with prompt and sustained increase in UO and a concomitant rise in MAP. Greater diuresis was linked to successful liberation from PPV, suggesting that mobilization of retained fluid is a marker of recovery, and the lack of it may help identify patients at higher risk of PPVdc failure. Prospective studies should explore whether proactive fluid management around the time of PPVdc could improve weaning outcomes.