Measurement of Tissue Oxygenation Using Near-Infrared Spectroscopy in Patients Undergoing Hemodialysis

Summary

We present a protocol to measure regional oxygen saturation (rSO₂) in hemodialysis (HD) patients by using a near-infrared spectroscopy monitor. The rSO₂ value is an index of tissue oxygenation. This noninvasive and real-time monitoring could be useful for confirming changes in organ oxygenation during HD.

Abstract

Near-infrared spectroscopy (NIRS) has recently been applied as a tool to measure regional oxygen saturation (rSO₂), a marker of tissue oxygenation, in clinical settings including cardiovascular and brain surgery, neonatal monitoring and prehospital medicine. The NIRS monitoring devices are real-time and noninvasive, and have mainly been used for evaluating cerebral oxygenation in critically ill patients during an operation or intensive care. Thus far, the use of NIRS monitoring in patients with chronic kidney disease (CKD) including hemodialysis (HD) has been limited; therefore, we investigated rSO₂ values in some organs during HD. We monitored rSO₂ values using a NIRS device transmitting near-infrared light at 2 wavelengths of attachment. The HD patients were placed in a supine position, with rSO₂ measurement sensors attached to the foreheads, the right hypochondrium and the lower legs to evaluate rSO₂ in the brain, liver and lower leg muscles, respectively. NIRS monitoring could be a new approach to clarify changes in organ oxygenation during HD or factors affecting tissue oxygenation in CKD patients. This article describes a protocol to measure tissue oxygenation represented by rSO₂ as applied in HD patients.

Introduction

Near-infrared spectroscopy (NIRS) has been used to evaluate regional oxygen saturation (rSO₂), a marker of tissue oxygenation, especially cerebral oxygenation in various clinical settings^1,2,3 and has recently been applied to patients undergoing hemodialysis (HD)^{4,5,6,7,8,9,10,11}. Cerebral rSO₂ is reportedly associated with cognitive function in patients undergoing HD or those with non-dialyzed chronic kidney disease (CKD)^11,12. However, thus far, the use of NIRS monitoring has been limited in patients with CKD.

As NIRS monitoring is real-time and noninvasive, we assessed its usefulness as a monitoring device in patients undergoing HD. Although NIRS is mainly used to measure cerebral rSO₂, we also investigated rSO₂ values in other organs during HD. Specifically, the rSO₂ measurement sensors were attached to the forehead, the right hypochondrium and the lower legs to evaluate rSO₂ in the brain, liver and lower muscles, respectively. The results showed that NIRS monitoring could be a new approach to clarify changes in organ oxygenation during HD or factors affecting tissue oxygenation in CKD patients.

To date, continuous monitoring was performed during HD, blood volume monitoring, central venous oxygen saturation, thoracic admittance and electronic stethoscope-guided estimated blood pressure (BP) in clinical settings^13,14,15; however, there are limitations for the prediction of hypotension or the wide use of devices. In contrast, the new noninvasive approach here could provide real-time information on intradialytic oxygen dynamics in individual organs. Therefore, this monitoring method may allow the detection of transient organ ischemia in the early phases of intradialytic hypotension and may also permit the safe performance of HD. This article describes a protocol to measure tissue oxygenation represented by rSO₂, as applied in patients undergoing HD.

Protocol

All participants provided written informed consent. The study was approved by the Institutional Review Board of the Saitama Medical Center, Jichi Medical University, Japan (RIN 15–104).

1. Device for the monitoring of rSO₂

1. Prepare a NIRS device for measuring tissue oxygenation. This device has four channels and can perform measurement in up to four organs at the same time.
2. Prepare a measurement sensor for NIRS monitoring, to evaluate rSO₂ values in each organ via transmitting near-infrared light at two wavelengths of attachment.

2. Attaching the measurement sensor

1. Allow each patient to rest in a supine position for at least 5 minutes before HD.
2. Attach measurement sensors to the forehead, the right hypochondrium and lower legs to evaluate rSO₂ in the brain, liver and lower leg muscles, respectively.
3. Monitoring of cerebral oxygenation
   1. Attach measurement sensors to the forehead of the dominant hemisphere.
4. Monitoring of hepatic oxygenation
   1. Prepare echography to measure the depth to the patients’ liver from the body surface. Confirm that this measurement is within 20–30 mm from the body surface. Next, attach the measurement sensors to the right hypochondrium.
      NOTE: In this device, rSO₂ values should be obtained in deep tissue 20–30 mm from the body surface. In some instances, the liver may be located in more than 30 mm from the body surface due to the presence of thick subcutaneous fat.
5. Monitoring of muscle oxygenation
   1. Attach measurement sensors to the right or bilateral lower legs.
6. Sensor connection and powering the device
   1. Connect each sensor to the leads from the device. Next, turn on the device, and start measuring oxygenation.

3. Puncturing the dialysis shunt and starting monitoring

1. Puncturing the dialysis shunt
   1. Puncture the patients’ dialysis shunt to start HD therapy. At this time, measure BP using a digital blood pressure monitor equipped with the dialysis machine and collect blood samples using syringes.
2. Start monitoring
   1. After starting HD therapy, start monitoring the tissue oxygenation of the three organs: the brain, liver and lower leg muscle.
3. Monitoring of rSO₂ during HD
   1. Observe changes in rSO₂ values of each organ and measure BP regularly in addition to the usual monitoring performed during HD therapy including heart rate, venous pressure and blood volume. Confirm the attachment area and connection between the sensors and leads.

Results

Cerebral rSO₂ values before HD were lower than those in healthy subjects and cerebral rSO₂ in HD patients with diabetes mellitus (DM) were lower than those in HD patients without DM (Figure 1)¹⁶. Furthermore, although tissue oxygenation continues without a decrease of BP during HD, we incidentally observed changes in cerebral and hepatic rSO₂ due to intradialytic hypotension (Figure 2). Due to the continuo...

Discussion

NIRS monitoring has been mainly used to evaluate cerebral rSO₂, especially in cardiovascular or cerebrovascular surgeries, which require extracorporeal circulation. During extracorporeal circulation including HD therapy, some organs could show relative ischemia^7,17,18; however, it remains unclear whether tissue oxygenation becomes low or not. Muscle cramps or abdominal pain during HD could be one of the prodromal symp...

Materials

Name	Company	Catalog Number	Comments
DBB-100NX	Nikkiso	DBB-100NX	Dialysis machine
INVOS 5100c	Covidien Japan	INVOSTM 5100c	tissue oxygenation device
SOMASENSER	Covidien Japan	CV-SAFB-SM/INTL	NIRS sensor