Abstract Background and Aims Urine oxygen level, an indicator of kidney medullar oxygenation, is promising for predicting the onset of acute kidney injury (AKI). Furosemide, a commonly used diuretic in ICU, significantly increases urine output and is believed to change kidney medullar oxygenation. We monitored the longitudinal change of urinary oxygen partial pressure during bolus or pump administration of furosemide, aiming to describe the reaction pattern in an AKI-susceptible patient population. Method The prospective observational pilot study included seven adult patients in the ICU because of cardiac surgery or sepsis. We monitored the continuous urinary oxygen partial pressure for 8-24 hours through a device placed between the urinary catheter and collecting bag during furosemide administration, recorded hourly urine output simultaneously from a urine bag, and followed the patients in the hospital for the onset and development of AKI. Results We recruited three female patients and four male patients with an average age of 54 years and a medium of 5 days in ICU with an AKIN stage I of AKI during their hospital stay. None of them developed more severe stage AKI or required any kidney replacement therapy. We found a reverse correlation pattern between hourly urine output and urinary oxygen partial pressure. Specifically, the urine oxygen level dropped during urine volume increase caused by furosemide bolus administration and abolished by furosemide administration through a pump with more stable urine output. The paired t-test showed a significant increase in average urine oxygen level (mean difference = 21.2 mmHg, p = 0.044) recorded during the “high hourly urine output” period compared to the “low hourly urine period”. Conclusion We first found a drop in urinary oxygen partial pressure during the high urine output period elicited by bolus furosemide administration. It shed light on the confounding factors in AKI predicating during possible furosemide administration.
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