Factors Influencing Prognosis in Patients Requiring Prolonged Mechanical Ventilation: Impact of the Role of Diurnal Plasma Cortisol Measurements

Objectives: Identify the factors, both respiratory and non-respiratory, that are associated with the outcomes of patients requiring prolonged mechanical ventilation (PMV). Methods: A retrospective medical record review at a 16-bed weaning ward. Forty-five consecutive ventilator-dependent patients admitted to our ward for attempted weaning during a 12-month period were included. Data were obtained from patients on the day of admission. Measurements included demographics, arterial blood gas, serum albumin, BUN, creatinine, AM (0800) cortisol, PM (1600) cortisol and functional respiratory parameters. Results: Twenty patients were successfully weaned from mechanical ventilation (weaning success) during the 90 days of admission, whilst the remaining 25 patients failed to wean or died (weaning failure) during the 90-day limit. Univariate logistic regression analysis showed that the outcome of weaning failure was significantly associated with 5 factors: tidal volume (OR, 0.98; 95% CI, 0.97-0.99; p=0.022), respiratory frequency (OR, 1.13; 95% CI, 1.01-1.27; p=0.024), frequency/tidal volume ratio (OR, 1.04; 95% CI, 1.01-1.16; p=0.005), maximum negative inspiratory pressure (OR, 0.91; 95% CI, 0.84-0.99; p=0.036), and slope of AM-PM cortisol levels (OR, 5.84; 95% CI, 1.81-18.88; p=0.003). Multivariate analysis revealed the 1 factor associated with weaning failure for patients requiring PMV to be the slope of AM-PM cortisol levels (OR, 8.35; 95% CI, 1.62-43.07; p=0.011). Conclusions: The slope of AM-PM cortisol levels on the day of admission was the only independent factor that influences the outcomes of patients requiring PMV. Our study provides strong support for the prognostic value of AM and PM cortiol measurements in the weaning ward. Some strategies aimed toward improving circadian rhythms may benefit the outcome of PMV patients.