2013, Number 2
Med Crit 2013; 27 (2)
Correlation of the ratios PaO2/FiO2 and SpO2/FiO2 in postoperative cardiac surgery at a Cardiovascular Postsurgical Care Unit
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ABSTRACTIntroduction: Traditionally, hypoxemia monitoring in postoperative patient of cardicac surgery is realized by blood gas determination, to determine the arterial oxygen tension and oxygenation index, which is important in cardiac surgery due to the patient will have to face to risk factors and develop lung dysfunction mostly by the complexity and aggressiveness of the extracorporeal circulation that will affect in the prognostic of the patient, despite there have been existed improvements in the myocardial protection, surgical revascularization and mechanical circulatory support techniques, the lung dysfunction incidence will be more frequent when extracorporeal circulation is used. A common way in intensive care to evaluate the acute lung dysfunction valuing the gas exchange has been the PaO2/FiO2 (P/F) index known as Index of Kirby being a good predictor in the acute lung dysfunction. Recently another index has proposed the SpO2/FiO2 (S/F) index to monitor in non invasive way the oxygenation and index that would bring a fast study where is possible to continue monitoring the breath.
Objective: Demonstrate the correlation between the P/F index and the S/F index of postoperative patient of cardiac surgery.
Material and methods: Prospective, cross sectional, observational and comparative study during November 2011 to June 2012. There were included 14 postoperative patients of cardiac surgery in the postsurgical care unit of the «Centro Médico ISSEMYM», Toluca. Which were studied the PaO2, SpO2, FiO2 variables to determine the P/F index and the S/F index. With the following inclusion criteria: patients of any gender over 18 years old, the ones with immediate postoperative patients cardiac surgery, oxygen saturation ‹ 97%. With the following exclusion criteria: patients with chronic obstructive pulmonary disease, state of shock, SpO2 ›97%, oximeter with weak signal or interference. For the postoperative patients of cardiac surgery were performed measurements in four times at 8 hours, 16 hours, 24 hours and 4 hours of PaO2, SpO2 and FiO2, obtaining 56 samples, calculated by a physician of the postsurgical unit the P/F index and the S/F index. Results are expressed in averages ± standard deviation; introducing the studied variables with normal distribution therefore the t Student was used to find the differences between groups, analyzing the correlation between different variables with Pearson.
Results: We included 56 samples obtained in 14 patients whom were not observed variability of the averages of the measured variables and a good correlation with both methods.
Conclusions: There is a statistically significant linear relationship between these variables. Correlation is observed between the PaO2/FiO2 index and the S/F index, with a good association of the measured variables. So we conclude that the S/F index could be used alternately to P/F index in the respiratory monitoring in postoperative patients of cardiac surgery.