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Examining the relationship between cerebral oxygen saturation monitoring and renal oxygen saturation monitoring using near-infrared spectrometry in pediatric cardiac surgery / Jeffrey L. Gruenberger.

by Gruenberger, Jeffrey L.

Cerebral arteries.

Cardiopulmonary bypass

Spectroscopy, Near-Infrared

Renal Circulation.

Pediatric cardiology

51 leaves : ill. ; 29 cm.

Thesis advisor: Dr. Ronald Gerrits.

Committee members: Dr. Larry Fennigkoh, Patrick VanderWal.

Background -- Methods -- Results -- Discussion -- References -- Appendices: 6.1 Technical specifications of the INVOS 5100B Cerebral Oximetry System by Somanetics Corporation of Troy, Michigan ; 6.2 Individual raw data values and Minitab statistical software analysis output.

Since 2001, Children's Hospital of Wisconsin has taken the technology of NIRS monitoring for cerebral tissue perfusion and expanded its application to include systemic, or specifically renal, perfusion. In addition to placing one of the Somanetics INVOS Cerebral Oximetry Systema SomaSensora pads mid-cranium, a second SomaSensora pad is placed near mid-posterior thoracic, immediately superior to the T12 vertebra. This area provides the closest proximity access to the renal vessels in pediatrics. By placing the second SomaSensora pad in this location, the effectiveness of cardiopulmonary perfusion on the renal and other systemic tissue can be monitored. While clinical trends and observations have been made over the years of this adapted use, no studies have been performed to analyze whether statistical significance exists between the standard cerebral oxygen saturation monitoring using the NIRS system and the modified renal, or systemic, oxygen saturation monitoring using the NIRS system. This study sought to find whether statistical relationships exist.

Cardiopulmonary perfusion records from twenty patients having the Norwood surgical procedure from July 7, 2006, through March 19, 2007, were reviewed. Correlation between CsO2 and RsO2 was found to be significant (r = 0.422, p < 0.001). Multiple linear regression analyses were performed to determine any significant relationship between the predictor variables of MAP, Q gas, FiO2, CO2, Q Art, Tr, Hct, and Time, and the response variable of RsO2. RsO2 was found to be significantly correlated to only 4 of the 8 predictor values tested, MAP, Q Art, Tr, and Hct. Multiple linear regression p-values were found to be as follows: MAP p = 0.010; Q Art p < 0.001; Tr p < 0.001; Hct p = 0.023.

Although the correlation between x and y was found to be significant, it cannot be stated that CsO2 has a direct correlation to RsO2, or that these values are interchangeable. The finding of significance for the variables MAP, Q Art, Tr and Hct were expected, since, while on-bypass, temperature and perfusion/pump pressure which is related to flow become of greater importance in ensuring proper perfusion, and with the relationship of pressure and flow as defined by Ohm’s Law; and since hematocrit defines the basic carrying capacity of oxygen by the red blood cells. It was unexpected to find no significance for the variables Q Gas, FiO2 and CO2, since these three variables represent the respiratory or gas exchange portion of cardiopulmonary bypass and are as critical to proper perfusion as the actual pumping or flow. Possible explanations for the finding of this lack of significance of these variables for RsO2 are the small study group used and limitation to one surgical procedure, the inequality of the number of data values recorded and analyzed from patient to patient, differences in anatomy and physiology between individual patients, and the use of parametric analysis tests on non-parametric data.

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