Influence of Variations in Systemic Blood Flow and Blood Pressure on Cerebral Oxygenation Measured by Cerebral Oximetry
Summary
This study emphasizes on the influence of changes in systemic flow and systemic mean arterial blood pressure (MAP) during cardiopulmonary bypass (CPB) on cerebral oxygenation assessed by near-infrared spectroscopy (NIRS). The aim of the study is to determine whether variations in systemic flow, in MAP, or in both variables at the same time have the greatest impact on the cerebral oxygen saturation.
Description
Cerebral autoregulation is defined as the whole of regulatory mechanisms that maintains a constant cerebral blood flow (CBF) during changes in cerebral perfusion pressure (CPP). Cerebrovascular resistance adjusts when CPP changes in order to keep CBF constant. In contrast with this concept of pressure-mediated autoregulation, it is suggested that cerebral autoregulation is focused on maintaining homeostasis of the cerebral metabolic rate of oxygen (CMRO2). We assume that both flow and pressure contribute to the regulation of CMRO2.
Assessment of cerebral oxygenation - Cerebral oxygen saturation will be monitored with near-infrared spectroscopy (NIRS). NIRS allows simple, continuous and non-invasive measurement of cerebral oxygen saturation (ScO2)and primarily cerebral venous saturation. Cerebral oxygen saturation will be monitored with a FDA-approved devices: INVOS 5100 (Somanetics Corporation, Troy, MI, USA).
To study the effects of changes in pressure and in flow, we need a condition where we can alter these variables separately and in a controlled manner. Therefore this study will be performed during cardiopulmonary bypass (CPB). Pressure will be varied with the administration of routinely used vasoactive substances, while flow will be varied by altering the pump flow manually. We hypothesize that if we change one parameter (pressure or flow), a compensatory mechanism will preserve the CMRO2 homeostasis, with no change in ScO2. On the other hand, if we change both pressure and flow, we expect a significant effect on cerebral oxygen saturation. With 20 % changes in pressure and/or flow, we expect a change in NIRS values of approximately 5 %. Previous studies showed that this kind of reduction is well tolerated by the brain. This means that the proposed changes are within the normal physiological range, and will have no adverse effects.
Study Design
Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Basic Science
Conditions
Cerebral Oxygen Saturation
Intervention
A disposable NIRS (near-infrared spectroscopy) sensor will be applied on the patient's forehead for continuous registration of the cerebral oxygen saturation.
Location
University Hospital Ghent
Ghent
Belgium
9000
Status
Completed
Source
University Hospital, Ghent
Results (where available)
Links
- Source: http://clinicaltrials.gov/show/NCT01424800
- Information obtained from ClinicalTrials.gov on April 02, 2012
Medical and Biotech [MESH] Definitions
Spectroscopy, Near-infrared
A noninvasive technique that uses the differential absorption properties of hemoglobin and myoglobin to evaluate tissue oxygenation and indirectly can measure regional hemodynamics and blood flow. Near-infrared light (NIR) can propagate through tissues and at particular wavelengths is differentially absorbed by oxygenated vs. deoxygenated forms of hemoglobin and myoglobin. Illumination of intact tissue with NIR allows qualitative assessment of changes in the tissue concentration of these molecules. The analysis is also used to determine body composition.
Spectroscopy, Fourier Transform Infrared
A spectroscopic technique in which a range of wavelengths is presented simultaneously with an interferometer and the spectrum is mathematically derived from the pattern thus obtained.
Thermography
Measurement of the regional temperature of the body or an organ by infrared sensing devices, based on self-emanating infrared radiation.
Infrared Rays
That portion of the electromagnetic spectrum usually sensed as heat. Infrared wavelengths are longer than those of visible light, extending into the microwave frequencies. They are used therapeutically as heat, and also to warm food in restaurants.
Spectrophotometry, Infrared
Spectrophotometry in the infrared region, usually for the purpose of chemical analysis through measurement of absorption spectra associated with rotational and vibrational energy levels of molecules. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
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