Predicting the Need for Renal Replacement Therapy Using a Vascular Occlusion Test and Tissue Oxygen Saturation in Patients in the Early Phase of Multiorgan Dysfunction Syndrome

Abstract

Background: Acute kidney injury (AKI) is associated with an increased mortality in critically ill patients, especially in patients with multiorgan dysfunction syndrome (MODS). In daily clinical practice, the grading of AKI follows the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. In most cases, a relevant delay occurs frequently between the onset of AKI and detectable changes in creatinine levels as well as clinical symptoms. The aim of the present study was to examine whether a near infrared spectroscopy (NIRS)-based, non-invasive ischemia-reperfusion test (vascular occlusion test (VOT)) together with unprovoked (under resting conditions) tissue oxygen saturation (StO₂) measurements, contain prognostic information in the early stage of MODS regarding the developing need for renal replacement therapy (RRT).

Methods: Within a period of 18 months, patients at the medical intensive care unit of a tertiary university hospital with newly developed MODS (≤24 h after diagnosis, APACHE II score ≥20) were included in our study. The VOT occlusion slope (OS) and recovery slope (RS) were recorded in addition to unprovoked StO₂. StO₂ was determined non-invasively in the area of the thenar muscles using a bedside NIRS device. The VOT was carried out by inflating a blood pressure cuff on the upper arm. AKI stages were determined by the changes in creatinine levels, urinary output, and/or the need for RRT according to KDIGO.

Results: 56 patients with MODS were included in the study (aged 62.5 ± 14.4 years, 40 men and 16 women, APACHE II score 34.5 ± 6.4). Incidences of the different AKI stages were: no AKI, 16.1% (n = 9); AKI stage I, 19.6% (n = 11); AKI stage II, 25% (n = 14); AKI stage III, 39.3% (n = 22). Thus, 39.3% of the patients (n = 22) developed the need for renal replacement therapy (AKI stage III). These patients had a significantly higher mortality over 28 days (RRT, 72% (n = 16/22) vs. no RRT, 44% (n = 15/34); p = 0.03). The mean unprovoked StO₂ of all patients at baseline was 81.7 ± 11.1%, and did not differ between patients with or without the need for RRT. Patients with RRT showed significantly weaker negative values of the OS (-9.1 ± 3.7 vs. -11.7 ± 4.1%/min, p = 0.01) and lower values for the RS (1.7 ± 0.9 vs. 2.3 ± 1.6%/s, p = 0.02) compared to non-dialysis patients. Consistent with these results, weaker negative values of the OS were found in higher AKI stages (no AKI, -12.7 ± 4.1%/min; AKI stage I, -11.5 ± 3.0%/min; AKI stage II, -11.1 ± 3.3%/min; AKI stage III, -9.1 ± 3.7%/min; p = 0.021). Unprovoked StO₂ did not contain prognostic information regarding the AKI stages.

Conclusions: The weaker negative values of the VOT parameter OS are associated with an increased risk of developing AKI and RRT, and increased mortality in the early phase of MODS, while unprovoked StO₂ does not contain prognostic information in that regard.

Keywords: MODS; acute kidney injury; intensive care; tissue oxygen saturation.

Figure 1

Unprovoked StO₂ and the VOT occlusion and recovery slopes at baseline and after 96 h, in the context of renal replacement therapy (RRT) status until day 28.

Figure 2

Mean ± standard deviation for unprovoked StO₂ and the VOT parameters OS and RS at baseline, regarding the stages of acute kidney injury (AKI) according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Bonferroni correction for OS: no AKI vs. AKI stage III, p = 0.036; no AKI vs. AKI stage I/AKI stage II, p > 0.05; AKI stage I vs. AKI stage II/AKI stage III, p > 0.05. Bonferroni correction for RS: no AKI vs. AKI stage III, p = 0.007; no AKI vs. AKI stage I/AKI stage II, p > 0.05; AKI stage I vs. AKI stage II/AKI stage III, p > 0.05. Bonferroni correction for unprovoked StO₂: no AKI vs. AKI stage III, p > 0.05; no AKI vs. AKI stage I/AKI stage II, p > 0.05; AKI stage I vs. AKI stage II/AKI stage III, p > 0.05.

Figure 3

Percentage of patients developing the need for renal replacement therapy in relation to their VOT occlusion slope at baseline; p = 0.045.

Figure 4

Forrest plot showing the unadjusted and adjusted odds ratios regarding the prediction of renal replacement therapy. APACHE II, acute physiology and chronic health evaluation.

Figure 5

The VOT occlusion slopes at baseline regarding 28-day mortality for patients receiving RRT (A) and patients not needing RRT (B), as well as the VOT recovery slopes at baseline regarding 28-day mortality for patients receiving RRT (C) and patients not needing RRT (D), using Kaplan–Meier survival curves; level of significance measured by p.