Dataset Information

Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements.

ABSTRACT:

Background

Continuous measurement of urinary PO₂ (PuO₂) is being applied to indirectly monitor renal medullary PO₂. However, when applied to critically ill patients with shock, its measurement may be affected by changes in FiO₂ and PaO₂ and potential associated O₂ diffusion between urine and ureteric or bladder tissue. We aimed to investigate PuO₂ measurements in septic shock patients with a fiberoptic luminescence optode inserted into the urinary catheter lumen in relation to episodes of FiO₂ change. We also evaluated medullary and urinary oxygen tension values in Merino ewes at two different FiO₂ levels.

Results

In 10 human patients, there were 32 FiO₂ decreases and 31 increases in FiO₂. Median pre-decrease FiO₂ was 0.36 [0.30, 0.39] and median post-decrease FiO₂ was 0.30 [0.23, 0.30], p = 0.006. PaO₂ levels decreased from 83 mmHg [77, 94] to 72 [62, 80] mmHg, p = 0.009. However, PuO₂ was 23.2 mmHg [20.5, 29.0] before and 24.2 mmHg [20.6, 26.3] after the intervention (p = 0.56). The median pre-increase FiO₂ was 0.30 [0.21, 0.30] and median post-increase FiO₂ was 0.35 [0.30, 0.40], p = 0.008. PaO₂ levels increased from 64 mmHg [58, 72 mmHg] to 71 mmHg [70, 100], p = 0.04. However, PuO₂ was 25.0 mmHg [IQR: 20.7, 26.8] before and 24.3 mmHg [IQR: 20.7, 26.3] after the intervention (p = 0.65). A mixed linear regression model showed a weak correlation between the variation in PaO₂ and the variation in PuO₂ values. In 9 Merino ewes, when comparing oxygen tension levels between FiO₂ of 0.21 and 0.40, medullary values did not differ (25.1 ± 13.4 mmHg vs. 27.9 ± 15.4 mmHg, respectively, p = 0.6766) and this was similar to urinary oxygen values (27.1 ± 6.17 mmHg vs. 29.7 ± 4.41 mmHg, respectively, p = 0.3192).

Conclusions

Changes in FiO₂ and PaO₂ within the context of usual care did not affect PuO₂. Our findings were supported by experimental data and suggest that PuO₂ can be used as biomarker of medullary oxygenation irrespective of FiO₂.

SUBMITTER: Osawa EA

PROVIDER: S-EPMC9742069 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

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Publications

Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements.

Osawa Eduardo A EA Cutuli Salvatore L SL Yanase Fumitaka F Iguchi Naoya N Bitker Laurent L Maciel Alexandre T AT Lankadeva Yugeesh R YR May Clive N CN Evans Roger G RG Eastwood Glenn M GM Bellomo Rinaldo R

Intensive care medicine experimental 20221212 1

<h4>Background</h4>Continuous measurement of urinary PO2 (PuO2) is being applied to indirectly monitor renal medullary PO2. However, when applied to critically ill patients with shock, its measurement may be affected by changes in FiO2 and PaO2 and potential associated O2 diffusion between urine and ureteric or bladder tissue. We aimed to investigate PuO2 measurements in septic shock patients with a fiberoptic luminesce ...[more]

PMID: 36504004

Similar Datasets

Project description:When hemoglobin (Hb) is fully saturated with oxygen, the additional gain in oxygen delivery (DO2) achieved by increasing the fraction of inspired oxygen (FiO2) is often considered clinically insignificant. In this study, we evaluated the change in DO2, interrogated by mixed venous oxygen saturation (SvO2), in response to a change in FiO2 of 0.5 during cardiac surgery. When patients were hemodynamically stable, FiO2 was alternated between 0.5 and 1.0 in on-pump cardiac surgery patients (pilot study), and between 0.3 and 0.8 in off-pump coronary artery bypass grafting patients (substudy of the CARROT trial). After the patient had stabilized, a blood gas analysis was performed to measure SvO2. The observed change in SvO2 (ΔSvO2) was compared to the expected ΔSvO2 calculated using Fick's equation. A total 106 changes in FiO2 (two changes per patient; total 53 patients; on-pump, n = 36; off-pump, n = 17) were finally analyzed. While Hb saturation remained near 100% (on-pump, 100%; off-pump, mean [SD] = 98.1% [1.5] when FiO2 was 0.3 and 99.9% [0.2] when FiO2 was 0.8), SvO2 changed significantly as FiO2 was changed (the first and second changes in on-pump, 7.7%p [3.8] and 7.6%p [3.5], respectively; off-pump, 7.9%p [4.9] and 6.2%p [3.9]; all P < 0.001). As a total, regardless of the surgery type, the observed ΔSvO2 after the FiO2 change of 0.5 was ≥ 5%p in 82 (77.4%) changes and ≥ 10%p in 31 (29.2%) changes (mean [SD], 7.5%p [3.9]). Hb concentration was not correlated with the observed ΔSvO2 (the first changes, r = - 0.06, P = 0.677; the second changes, r = - 0.21, P = 0.138). The mean (SD) residual ΔSvO2 (observed - expected ΔSvO2) was 0%p (4). Residual ΔSvO2 was more than 5%p in 14 (13.2%) changes and exceeded 10%p in 2 (1.9%) changes. Residual ΔSvO2 was greater in patients with chronic kidney disease than in those without (median [IQR], 5%p [0 to 7] vs. 0%p [- 3 to 2]; P = 0.049). DO2, interrogated by SvO2, may increase to a clinically significant degree as FiO2 is increased during cardiac surgery, and the increase of SvO2 is not related to Hb concentration. SvO2 increases more than expected in patients with chronic kidney disease. Increasing FiO2 can be used to increase DO2 during cardiac surgery.

Dataset Information

Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements.

Background

Results

Conclusions

Publications

Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements.

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