Renal Oxygenation (rSO2) Population Parameter Estimates in Premature Infants Routinely Monitored With Near-Infrared Spectroscopy

The Association Between Renal Desaturation Measured Using Near-Infrared Spectroscopy and Postoperative Acute Kidney Injury: A Systematic Review

OBJECTIVES

The objective of this systematic review was to clarify the status of near-infrared spectroscopy (NIRS) in monitoring perioperative renal regional tissue oxygen saturation (rSO2) and determine whether there is evidence supporting its use in predicting postoperative acute kidney injury (AKI).

DESIGN

A systematic search of electronic databases was conducted to identify all clinical studies that utilized NIRS to monitor renal rSO2 during the perioperative period to observe postoperative AKI.

SETTING

Studies published online as of May 31, 2024, were included in the review.

PARTICIPANTS

Studies involving human participants undergoing surgery with a predefined outcome of AKI were included.

INTERVENTIONS

Regional tissue oxygen saturation was measured using NIRS.

MEASUREMENTS AND MAIN RESULTS

A total of 144 records were identified in the primary search after removing duplicates. After screening, 18 studies were included in the analysis, consisting of 3 case-control studies and 15 prospective cohort studies. Thirteen reports focused on pediatric surgery, whereas five reports focused on adult surgery. Sixteen studies involved cardiovascular surgery with cardiopulmonary bypass, and two studies focused on liver surgery. All studies received a quality score of 7 or above. Significant heterogeneity and mostly short follow up periods were noted.

CONCLUSION

Renal desaturation may indicate AKI in patients; however, further studies are required to substantiate this relationship. Additional clinical trials are necessary to evaluate normal values and establish the exact threshold of renal rSO2 that signifies a meaningful decline in renal function.

Renal Regional Oxygen Saturation and Acute Kidney Injury in Neonates with Perinatal Asphyxia

OBJECTIVE

 Neonates with moderate-to-severe perinatal asphyxia often develop acute kidney injury (AKI). Additionally, therapeutic hypothermia (TH) can affect renal blood flow. This study aimed to evaluate the association between renal regional oxygen saturation (rSrO2) during TH and AKI in neonates with moderate and severe perinatal asphyxia.

STUDY DESIGN

 This retrospective longitudinal study included neonates with moderate-to-severe asphyxia who required TH. The primary outcome was the occurrence of AKI, classified as a rate of decrease in creatinine levels of <33% at 72 hours of TH. rSrO2 was continuously monitored by near-infrared spectroscopy during the hypothermia and rewarming phases. Data analysis involved dividing the average rSrO2 levels into 12-hour periods. We analyzed the association between AKI and rSrO2 levels using univariate and multivariate logistic regression models. Furthermore, we assessed the predictive capacity of rSrO2 for AKI by analyzing the area under the receiver operating characteristic curve.

RESULTS

 Ninety-one patients were included in the study. On average, patients with AKI exhibit lower rSrO2 levels during TH. Specifically, rSrO2 levels within the first 12 hours and between 25 and 72 hours of TH demonstrated the highest predictive capability for AKI. Multivariate logistic regression analysis revealed that rSrO2 levels within the initial 12 hours (adjusted odds ratio [aOR] = 1.11, 95% confidence interval [CI]: 1.01-1.21) and between 61 and 72 hours (aOR = 0.85, 95% CI: 0.78-0.92) were significantly associated with AKI.

CONCLUSION

 An increase in rSrO2 during the first 12 hours of TH and lower rSrO2 levels between 61 and 72 hours of treatment were associated with the development of AKI in asphyxiated neonates undergoing TH.

KEY POINTS

· Neonates with asphyxia often develop AKI.. · Renal saturations are affected by hypothermia and asphyxia. · Patients with AKI initially show higher rSrO2, then lower rSrO2.. · Monitoring rSrO2 identifies early AKI..

Changes in regional tissue oxygen saturation values during the first week of life in stable preterm infants

OBJECTIVES

Near infrared spectroscopy (NIRS) is a non-invasive method for monitoring regional tissue oxygen saturation (rSO2). The purpose of this study is to investigate the changes that occur in cerebral, splanchnic, and renal rSO2 and fractional tissue oxygen extraction (FTOE) in stable preterm infants in the first week of life.

METHODS

Prospective observational study of infants born 30-34 weeks gestation at NYU Langone Health between November 2017 and November 2018. Cerebral, renal, and splanchnic rSO2 were monitored from 12 to 72 h of life, and at seven days. Subjects were divided into gestational age (GA) cohorts. Average rSO2, splanchnic cerebral oxygen ratio (SCOR), FTOE, and regional intra-subject variability was calculated at each location at five different time intervals: 0-12 h, 12-24 h, 24-48 h, 48-72 h, and one week of life.

RESULTS

Twenty subjects were enrolled. The average cerebral rSO2 ranged from 76.8 to 92.8 %, renal rSO2 from 65.1 to 91.1 %, and splanchnic rSO2 from 36.1 to 76.3 %. The SCOR ranged from 0.45 to 0.94. The strongest correlation between the GA cohorts was in the cerebral region (R2=0.94) and weakest correlation was in the splanchnic region (R2=0.81). The FTOE increased in all three locations over time. Intra-subject variability was lowest in the cerebral region (1.3 % (±1.9)).

CONCLUSIONS

The cerebral region showed the strongest correlation between GA cohorts and lowest intra-subject variability, making it the most suitable for clinical use when monitoring for tissue hypoxia. Further studies are needed to further examine rSO2 in preterm infants.

Correlation of Renal Tissue Oxygenation to Venous, Arterial, and Capillary Blood Gas Oxygen Saturation in Preterm Neonates

OBJECTIVE

The aim of the study is to assess the correlation of renal regional tissue saturation of oxygen (RrSO2) measured by near-infrared spectroscopy (NIRS) in preterm neonates to venous oxygen saturation (SvO2) obtained from umbilical venous catheters (UVCs), arterial oxygen saturation (SaO2) obtained from umbilical artery catheters (UACs), and capillary oxygen saturation (ScO2) from capillary heel blood draws.

STUDY DESIGN

A secondary analysis of a prospective RrSO2 monitoring study in preterm neonates born <32 weeks gestational age. Neonates with any blood gas obtained during RrSO2 monitoring were included. RrSO2 was compared with simultaneous O2 saturation using non-parametric Mann Whitney U-test and Spearman correlation coefficient.

RESULTS

In 35 neonates, 25 UVC, 151 UAC, and 68 heel capillary specimens were obtained. RrSO2 was lower than the median SvO2 (58.8 vs. 78.9, p <0.01), SaO2 (51.0 vs. 93.2, p <0.01), and ScO2 (62.2 vs. 94.25, p <0.01). RrSO2 values correlated to both SaO2 and ScO2 (r = 0.32; p <0.01, r = 0.26; p = 0.03), but not SvO2 (r = 0.07; p = 0.74).

CONCLUSION

In this secondary analysis, RrSO2 was consistently lower than blood gas O2 saturations and correlated with SaO2 and ScO2 but not SvO2. Lack of a correlation to SvO2 could be due to the small UVC sample size limiting statistical power. Future studies should prospectively evaluate if RrSO2 truly primarily reflects venous oxygenation in preterm neonates.

KEY POINTS

· Renal oxygenation correlates with arterial and capillary oxygen saturation.. · Renal oxygenation did not correlate with venous oxygenation from umbilical venous catheters.. · Studies are needed to determine if renal oxygenation primarily reflects venous or arterial oxygen..

Understanding Near-Infrared Spectroscopy: An Update

Near-infrared spectroscopy (NIRS) is a novel technology that uses infrared light to noninvasively and continuously measure regional oxygen extraction in real time at the bedside. Neonatal research using this device supports its use as an adjunct to routine cardiovascular monitoring because NIRS serves as a surrogate marker for end-organ perfusion and can detect minute changes in cerebral, intestinal, and kidney tissue beds. Multiple conditions affecting premature infants are frequently associated with hypoperfusion; therefore, methods to detect early tissue-specific perfusion alterations may substantially improve the clinician's ability to intervene and prevent further deterioration.

Routine Diaper Change Alters Kidney Oxygenation in Premature Infants: A Non-A Priori Analysis

BACKGROUND

Reduction in oxygen delivery to developing kidneys of premature infants may be an important source for acute kidney injury in premature infants.

PURPOSE

To describe changes in continuous kidney oxygenation (RrSO 2 ) measures before, during, and after routine diaper changes.

METHODS

Non-a priori analysis of a prospective cohort that received continuous measurement of RrSO 2 with near-infrared spectroscopy (NIRS) over the first 14 days of life demonstrating acute RrSO 2 drops surrounding diaper changes.

RESULTS

In total, 26 of 38 (68%) infants (≤1800 g) from our cohort exhibited acute drops in RrSO 2 that temporally correlated with diaper changes. Mean (SD) RrSO 2 baseline prior to each diaper change event was 71.1 (13.2), dropped to 59.3 (11.6) during diaper change, and recovered to 73.3 (13.2). There was a significant difference between means when comparing baseline to diaper change ( P < .001; 95% CI, 9.9 to 13.8) and diaper change to recovery ( P < .001; 95% CI, -16.9 to -11.2). The mean decrease in RrSO 2 during diaper change averaged 12 points (17%) below 15-minute RrSO 2 mean prior to diaper change, with quick recovery to prediaper change levels. No decreases in SpO 2 , blood pressure, or heart rate were documented during the intermittent kidney hypoxic events.

IMPLICATIONS FOR PRACTICE AND RESEARCH

Routine diaper changes in preterm infants may increase the risk for acute reductions in RrSO 2 as measured by NIRS; however, the impact on kidney health remains unknown. Larger prospective cohort studies assessing kidney function and outcomes related to this phenomenon are needed.

Renal oxygenation measured by near-infrared spectroscopy in preterm neonates in the first week

OBJECTIVE

To describe renal regional saturation of oxygen (RrSO₂) values during the first week of life for preterm neonates born at <32 weeks gestational age (GA).

METHODS

RrSO₂ values recorded over the first week of life using near-infrared spectroscopy were retrospectively analyzed in this two-center cohort study of preterm infants without known congenital anomalies of the kidney.

RESULTS

A cohort of 109 neonates with a median GA of 26.9 weeks and a median of 120 (IQR: 87-141) hours of continuous RrSO₂ monitoring were included. Separately fitted trends in RrSO₂ did not differ (p = 0.52) between sites and demonstrated a consistent decrease in RrSO₂ by 20 points (95% CI: 9.6-30.1) during the first 60 h of life, followed by a stabilization of RrSO₂ thereafter. RrSO₂ baseline trends increased by 2.1 (95% CI: 0.8-3.3) percentage points for each additional week GA between 24 and 32 weeks GA.

CONCLUSIONS

Despite differences in adjusted RrSO₂ values between sites, profiles over time are consistent, allowing for the determination of RrSO₂ trajectories in preterm infants. This expected pattern of RrSO₂ changes in the first week may help guide future investigations and interventions to identify and reduce kidney injury in the preterm neonate.

IMPACT

Renal regional saturation of oxygen (RrSO₂) slowly decreases during the first 60 h of age in <32-week preterm neonates. While site differences were identified with respect to absolute values, RrSO₂ trends from two different centers were not different. Lower gestational age neonates have lower RrSO₂ levels during the first week.