Impact of renal dysfunction on weaning from prolonged mechanical ventilation

In the intensive care unit (ICU) setting, the combination of mechanical ventilation and renal replacement therapy (RRT) has been associated with prolonged length of hospital stay, high cost of care and poor outcome. We gathered outcome data on patients who had severe renal dysfunction on transfer to our regional weaning center (RWC) for attempted weaning from prolonged mechanical ventilation (PMV). We screened the admission laboratory values of 1077 patients transferred to our RWC over an 8-year period. We reviewed the medical records of patients with serum creatinine > 2.5 mg/dl.

Sixty-three patients met screening criteria and 40 patients were on RRT at the time of transfer. Eighteen patients had begun chronic RRT at least 2 months prior to admission to the transferring hospital for their current illness. Twenty-two patients had RRT initiated at the transferring hospital. Ten patients had RRT initiated at the RWC; eight patients had improvement or resolution of azotemia at our facility. RRT was withheld at patient/family request in five patients with progressive renal failure. None of the 50 patients who received RRT recovered renal function during treatment at our RWC. Intermittent hemodialysis was the standard RRT at the RWC. Duration of mechanical ventilation prior to transfer to the RWC was 49.7 ± 33.5 days (mean ± SD).

Outcome of weaning attempts in the 63 patients was as follows: 13% weaned, 3% failed to wean and 84% died. These outcomes were significantly worse (P<0.001) than those in the 1014 patients whose admission serum creatinine was = 2.5 mg/dl (58% weaned, 15% failed to wean, 27% died). The five patients in whom RRT was withheld were predominantly in progressive multisystem organ failure, and were unlikely to have survived regardless of RRT. From the study cohort, only one of the 10 patients discharged alive returned home, in contrast to 42% of the control group. No patient with severe renal dysfunction survived to 1 year post-discharge, compared to a 1-year survival of 38% in the control group (P = 0.029). Only four of the 10 patients survived more than 1 month, with the longest survival being 122 days.

Patients who require PMV and RRT have a very poor prognosis. The small number of patients with renal insufficiency not requiring RRT had a more favorable hospital outcome and mortality, but long-term survival remained poor.