Is Regional Oxygen Saturation Effective in Predicting Perfusion Parameters and Patient Outcomes in Liver Resection

Intraoperative tissue ischemia correlates with morbidity and mortality in critically ill patients. Therefore, measurement of tissue oxygenation is important in improving postoperative survival. Although values such as pulse oximetry, blood gas analysis, mixed venous oxygen saturation are routinely used to measure systemic oxygenation, regional tissue oxygen saturation measurement has not yet taken place in clinical practice.

The noninvasive measurement of human tissue oxygenation was first performed in 1874 by Karl Von Vierordt, with the detection of the reduction in the amount of infrared radiation passing through an ischemia-affected hand. The first portable oximeter was developed by Glen Milliken in 1942, but the device has only been used as an experimental tool in the aeronautical and physiology laboratory.

Adequate oxygen delivery (QO2) to meet the metabolic needs (VO2) of a tissue undergoing aerobic metabolism is critical for the long-term viability of this tissue. This condition was first described by Adolph Fick. For example, as the metabolic rate increases in peripheral tissues such as skeletal muscle, oxygen delivery will increase, so the amount of oxygen in the venous capillaries decreases and the arteriovenous oxygen difference increases. In addition, according to Fick's law, it is predicted that tissue oxygen delivery will increase with increasing oxygen gradient in microvascular tissue. Various invasive and/or expensive techniques have been developed to understand the balance between oxygen supply and consumption in peripheral tissue according to Fick's law. MR, PET, and arterial/venous catheterization are examples of these.

NIRS (Near Infrared Spectroscopy) Technology NIRS was first used in clinical practice in 1985 to measure cerebral oxygenation in preterm infants. It was developed to measure regional and systemic oxygenation noninvasively and continuously.

Its working principle is based on the measurement by attenuation of light of a certain wavelength (700-1000 nm) by chromophores such as hemoglobin in the sampled tissue by absorbing it in the tissue. The NIRS signal is mainly derived from hemoglobin in the entire vascular space, primarily small vessels (arterioles, capillaries, and venules). As a result, it provides the measurement of tissue hemoglobin or saturation (StO2) by measuring oxy and deoxy hemoglobin in the tissue. NIRS can also assist in estimating the amount of tissue hemoglobin by reflecting either the total tissue hemoglobin (HbT) or the absolute tissue hemoglobin index (THI).

InSpectra Tissue Spectrometer InSpectra Tissue Spectrometer Model 1615 probe (Hutchinson Technology Inc. Hutchinson, MN, USA); It measures the StO2 value by placing it in the area where somatic oxygenation will be measured. In studies with this device, measurements were made mostly in the thenar region, masseter and deltoid muscle.

Basal StO2 values in the thenar region have been shown to be 86%±6% in healthy subjects. In previous studies, the demonstration of peripheral hypoperfusion with the measurement of StO2 in skeletal muscle has been shown as an early indicator of conditions such as shock and hypovolemia. In addition, there are studies in the literature in which morbidity and mortality follow-up by measuring StO2 in critical patient follow-up such as sepsis. It has been shown that StO2 values below 75% are associated with adverse clinical outcomes in septic patients. In some studies conducted with trauma patients, StO2 measurement after the vascular occlusion test was found to be ineffective as an indicator of early hypoperfusion. In major surgeries such as cardiac surgery and colon resection, significant results have been found by monitoring morbidity, mortality, and postoperative complications with peripheral perfusion measurement. In the literature, hepatic StO2 measurement has been made in pediatric cases and experimental studies; There is no study in which somatic oxygenation measurement was performed in liver resection surgeries in adult patients.

O3TM Regional Oximeter System The O3TM Regional Oximeter System (O3 System, Masimo Corporation, Irvine, CA) is a non-invasive oximeter used to measure and monitor regional oxygen saturation (rSO2) in tissue. O3 sensors are used to measure somatic oxygen saturation in adult patients weighing 40 kg or more.

Parameters that can be measured with this device: rSO2, AUC index ( area under the curve), baseline, delta baseline (Δbase), delta SpO2 (ΔSpO2), Delta HHb (ΔHHb), Delta O2Hb (ΔO2Hb), Delta cHb (ΔcHb).

rSO2 is displayed as a percentage and is a measurement of the regional tissue oxygen saturation value in the local tissue at the sensor site.

Delta SpO2 is also displayed as a percentage and is found by calculating the difference between SpO2 and rSO2.

The delta baseline reflects the change of current rSO2 values relative to the rSO2 value initially shown as a percentage. In order to measure this value, basal rSO2 measurement should be made by pressing the "set baseline" button when the device is connected to the patient.

AUC (min-%) measures the time and depth that the patient stays below the user-defined rSO2 low alarm limit (LAL). Time (minutes) refers to the time the patient stays below the LAL rSO2 value. Depth (%) expresses the magnitude of the difference between the patient's rSO2 level and the LAL rSO2. AUC; It increases when the rSO2 value falls below the defined LAL value. AUC has not been studied in the literature yet, and it has been observed in clinical experience that tissue oxygenation becomes critical when the AUC value is around 500.

Delta HHb, Delta O2Hb and Delta cHb; these features are displayed when the head is selected as the sensor region.

Since tissue hypoperfusion may develop especially in the vascular clamp stage of liver resection surgeries, it is thought that the measurement of peripheral tissue oxygenation in standard monitoring may have a positive effect on patient outcomes.

In the present observational study, the investigators will evaluate the effects of hepatic and renal StO2 measurement on early hypoperfusion and postoperative survival in hepatectomy cases, and peripheral tissue oxygen saturation measurement with StO2 InSpectra Tissue Spectrometer Model 1615 probe (Hutchinson Technology Inc. Hutchinson, MN, USA) and O3TM Regional Oximeter System) The investigators aimed to observe by doing it with O3 System, Masimo Corporation, Irvine, CA) devices. The secondary aim of the study is that these values; age, anatomical region, ASA physical condition, whether it will be affected by the vascular clamp duration and its correlation with the risk of developing postoperative complications.