Elitsa L. Pavlova1, Rumen A. Marinov2, Varban M. Savov1, Vladimir B. Pilossoff2.
1Medical Physics,Faculty of Physics, Sofia University "St. Kliment Ohridski", Sofia, Bulgaria,
2Department of Children Cardiology and Cardio-surgery, National Cardiology Hospital, Sofia, Bulgaria.
ADDRESS FOR CORRESPONDENCE
Elitsa Lyubomirova Pavlova, Medical Physics, Faculty of Physics, Sofia University, St. Kliment Ohridski, 5 James Boucher Blvd. 1164 Sofia, Bulgaria
Email: elli_pavlova@abv.bg | The aim of this work is to study the dynamics of oxidative stress in blood of children with congenital heart malformations (CHM) before, during and after open-heart surgery. Thirty eight children aged 5 days to 9 years are divided in two groups: 1.Children with large ventricular septal defects and severe heart failure (HF) consisting of 20 patients and 2. Cyanotic children with tetralogy of Fallot (TF) consisting of 18 patients. Blood samples are obtained immediately after arterial cannulation, 20 minutes after switch to cardiopulmonary bypass and 60 minutes after the end of extra-corporal circulation (ECC). All measurements are performed in triplicate, within 4-6 hours after blood sampling (p= 0.01).
Open-heart surgery activates the processes of lipid peroxidation and increases the concentrations of thiobarbituric acid reactive substances (TBARS) about 65%. Their level decreases to initial levels in 60 min after switch to physiological blood circulation in both groups of patients. There is no significant difference in the concentrations of TBARS between the two groups of patients. Oxidative metabolism is restored as a result of reperfusion and extra-corporal circulation. (1, 2, 3)
Lucigenin enhanced chemiluminescence is a sensitive method for detection of superoxide radicals and other reactive oxygen species, especially at the initial stage of oxidative stress. (4, 5) It is well established that oxidation stimulates pro-oxidant reactions, which are compensated by the excretion of tissue antioxidants and antioxidant enzymes .(6) Before open-heart surgery, the intensity of chemiluminescence in blood plasma of HF children is 25% higher than that of patients with TF. During cardio-pulmonary bypass the light emission is slightly changing in TF patients; it is rapidly suppressed in children with HF. This is explained with fewer complications in these patients.
The antioxidant enzyme superoxide dismutase (SOD) gives direct approach for estimation of the damaging superoxide radicals and oxidative stress. (7) The SOD-activity of red blood cells in children with CHM is lower than healthy controls prior to operation (about 15%). This enzyme is suppressed even more in TF children on and after surgery. In HF patients it is induced to higher extent (40%) during surgery and is decreased with 25% after. This is also confirmed by the correlations calculated between the activity of SOD and the intensity of chemiluminescence in blood of HF patients
(rFT = -0.619, rHF = -0.989). Usually, higher concentrations of free radicals are accompanied with low SOD-activity. Nevertheless the decreased SOD-activity in erythrocytes cannot be considered as a direct proof of altered SOD-function in the myocardium.
The total antioxidant activity (TAOA) is determined by the overall effect of water-soluble antioxidants, lipid-soluble antioxidants and antioxidant enzymes. Since antioxidants seem to act co-operatively against oxidative stress in vivo, this method could provide more comprehensive assessment of heart diseases than the evaluation of single antioxidants. The measurements of the TAOA confirm general low antioxidant defense in both groups of children, compared to the healthy controls. TAOA is decreased 20% in the TF group before surgery and is extremely low in HF children (about 50%). In FT patients TAOA is reduced 25% during surgery and is decreased 30% after the operation. The level of TAOA in the HF group keeps stable through the whole studied period. The correlation between TAOA and chemiluminescence confirms the free radical mechanism of tissue damage in heart failure (r= -0.99). After switch off of the cardio-pulmonary bypass, the antioxidant defense is diminished twice. The extra-corporal blood circulation causes oxidative stress, exhausts metabolic antioxidants and diminishes the antioxidant capacity of the organism.
The obtained clinical data show that the markers of inflammation (leukocytes, hematocrit, C-reactive protein) vary and are indicative for activated immune response. All markers of oxidative stress (leukocytes, thrombocytes, C-reactive protein, Ca2+) exhibit extremely high correlation with TAOA.
On the first postoperative day all blood parameters return to initial, pre-operative levels. It should be noticed that open-heart surgery with ECC demands anesthesia and hypothermia (~28oC), which inevitably result in detained metabolism. All data demonstrate a definite time-course of the oxidative stress markers in arterial blood during open-heart surgery.
Oxidative stress is strongly induced in children with CHM. HF and TF patients present different capacity of antioxidant response and dynamics of accumulation of oxidized products .(8, 9, 10)
| | | | Compliance with Ethical Standards | | Funding None | | | | Conflict of Interest None | | |
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| Cite this article as: | | Pavlova E L, Marinov R A, Savov V M, Pilossoff V B. Oxidative Stress in Children Undergoing Surgical Corrections of Congenital Heart Malformations. Pediatr Oncall J. 2009;6: 53-54. |
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