Unit:
Faculty of MedicineLibrary of the School of Health Sciences
Dissertation committee:
Κασσιανή Θεοδωράκη, Kαθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Εριφύλη Αργύρα, Kαθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Ιωάννης Βασιλείου, Kαθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Αθανασία Τσαρουχά, Αναπληρώτρια Kαθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Χρυσούλα Στάϊκου, Kαθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Σερένα Βαλσάμη, Αναπληρώτρια Kαθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Μαρτίνα Ρεκατσίνα, Επίκουρη Kαθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Original Title:
Διερεύνηση της μεταβολής των επιπέδων του εκπνεόμενου ΝΟ και των ηωσινόφιλων στο αίμα ασθενών που υποβάλλονται σε θυρεοειδεκτομή με δύο διαφορετικές μεθόδους διατήρησης της αναισθησίας
Translated title:
Effect of general anesthesia maintenance with propofol or sevoflurane on fractional exhaled nitric oxide and eosinophil blood count: a prospective, single blind, randomized, clinical study on patients undergoing thyroidectomy
Summary:
Nitric oxide (NO) is a free radical in gas state, which plays an important role in a variety of processes relevant to respiratory physiology. The generation of NO follows both enzymatic and non-enzymatic pathways. NO enzymatic production is catalyzed by three distinct isoforms of NO synthase: (i) neuronal NOS-1 (nNOS), mainly expressed in central and peripheral neurons, (ii) inducible NOS-2 (iNOS), expressed by many cell types as response to cytokines and other agents, and (iii) endothelial NOS-3 (eNOS), mostly expressed by endothelial cells.
Non-enzymatic pathways, which are not clearly understood, produce NO through the reduction of NO3 (nitrate) to NO2 (nitrite). An imbalance between iNOS and its constitutive isoforms (nNOS and eNOS) has been implicated in the pathophysiology of many cardiopulmonary diseases, since it can lead to excessive NO synthesis.
While physiological levels of NO possess anti-inflammatory properties,
when increased due to the aforementioned upregulation of iNOS, NO becomes a proinflammatory mediator. In fact, high concentrations of NO can be transformed into peroxynitrite radicals in the presence of oxygen-derived free radicals and play a significant role in the cellular damage associated with overproduction of NO.
Airways of patients with bronchial hyperreactivity may respond in an exaggerated way to a variety of stimuli, while airway instrumentation in such patients may lead to life-threatening bronchospasm, adding to the burden of morbidity this population may suffer in case they undergo general anesthesia for a surgical or diagnostic procedure.
Fractional exhaled NO (FeNO) has been used in the diagnosis of asthma, especially of the eosinophilic phenotype, and has also proved useful in guiding treatment of asthmatic individuals.
Additionally, non-asthmatic patients experiencing bronchospasm intraoperatively or postoperatively display higher levels of exhaled NO, a fact suggesting that the upregulation of the production of NO may play a role in airway hyperreactivity.
Increased levels of FeNO have also been found to correlate with sputum eosinophilia and eosinophilia in bronchoalveolar lavage fluid. Furthermore, an increase in exhaled NO concentration has been used as an early marker of lung inflammation and injury in models of sepsis or acute lung injury induced by toxins . Therefore, exhaled NO can be considered an efficient method for the prediction of airway hyperresponsiveness perioperatively, even in patients without known respiratory disease .
Additionally, it may be considered as an invaluable non-invasive biomarker reflecting early airway injury and inflammation.
Propofol, an intravenous anesthetic agent, can modify NO production by inhibiting the inducible production of NO in lipopolysaccharide-stimulated macrophages [15,16].
It has also been shown to exert protective effects in acute lung injury in experimental models. There is also evidence that some intravenous anesthetics can influence chemotaxis of eosinophils in vitro.
Similarly, volatile anesthetics have been shown to attenuate the expression of inflammatory mediators and to alleviate bronchial hyperresponsiveness. Sevoflurane-borne protection could also be mediated via the suppression of the iNOS/NO pathway, as decreased levels of NO metabolites have been demonstrated in plasma or lung perfusate of sevoflurane-pretreated rat models.
The variation of exhaled NO and eosinophils in surgical patients undergoing anesthesia has not been studied before. We hypothesized that there is a different effect of intravenous and inhalational techniques on the potential for airway hyperresponsiveness perioperatively, as this can be assessed by the measurement of exhaled NO and eosinophil blood count.
If this is the case, it could also affect the selection of anesthetic maintenance techniques for patients with known hyperreactive airways. Therefore, the aim of the present study was to investigate the differential impact of two general anesthesia maintenance techniques on the exhaled NO and eosinophil blood count of patients without respiratory disease or airway hyperreactivity.
Main subject category:
Health Sciences
Keywords:
Fractional exhaled NO, Sevoflurane, Propofol, Eosinophil blood count, Thyroidectomy
Number of references:
169
