Minute-to-minute urine flow rate variability: a retrospective survey of its ability to provide early warning of acute hypotension in critically ill multiple trauma patients.

Purpose: Dynamic changes in urine output and neurological status are the recognized clinical signs of hemodynamically significant hemorrhage. In the present study, we analyzed the dynamic minute-to-minute changes in the UFR and also the changes in its minute-to-minute variability in a group of critically ill multiple trauma patients whose blood pressures were normal on admission to the ICU but who subsequently developed hypotension within the first few hours of their ICU admission.

Patients And Methods: The study was retrospective and observational. Demographic and clinical data were extracted from the computerized register information systems initially; the clinical and laboratory data of 100 critically ill patients with multiple trauma who were admitted to the ICU during the study period were analyzed. Of this group, ten patients were eventually included in the study on the basis of the inclusion criteria.

Results: The minute-to-minute urine flow rate (UFR) and urine flow rate variability (UFRV) both decreased significantly during the periods of hypotension (p values 0.001 and 0.006, respectively). Notably, the decrease in UFRV preceded by at least 30 min a corresponding decline in the systolic and mean arterial blood pressures, which manifested as a flattening of UFRV amplitude which was observed prior to the occurrence of the lowest recorded systolic and mean arterial blood pressures. Statistical analysis by the Pearson method demonstrated a strong direct correlation between the decrease in UFRV and the decrease in the MAP (R = 0.9, p = 0.001), and SBP (R = 0.86, p = 0.001) and the decreasing urine output per hour (R = 0.88, p < 0.001).

Conclusion: We found that changes in UFRV correlate strongly with systolic and mean arterial blood pressures. We feel that this parameter could potentially serve as an early signal of hemodynamic deterioration due to occult bleeding in critically ill trauma patients, and might also be able to identify the optimal end-point of hemodynamic resuscitative measures in these patients.