Interference of the general anesthetics propofol and isoflurane on lung morphology in mice septic

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1 Interference of the general anesthetics propofol and isoflurane on lung morphology in mice septic Davim A 1., Santos E 2 1 Departament of Anatomy. Centro Universitário do Rio Grande do Norte UNI-RN 2 Departament of Biochemistry. Universidade Federal do Rio Grande do Norte - UFRN Abstract Abdominal sepsis is a common post-operative condition found in intensive care units and actually represents a major public health problem in the world. Sepsis can lead to tissue injury in organs intensely vascularized due to increased microvascular permeability. In order to investigate the contribution of general anesthetics in this acute pulmonary injury, we performed a morphological study in an experimental model of sepsis. Male mice were divided in three groups: negative control and treated with propofol or isoflurane. Afterwards, the animals underwent surgery to induce sepsis through the technique of CLP and the lungs were submitted to a histological evaluation after broncho-alveolar lavage. For statistical analysis we used the ANOVA and Turkey tests. Results shown that lung cell migration was more intense in the isoflurane group. Moreover, the animals submitted to anesthesia with propofol showed greater integrity of the lung parenchyma. According to these results, we can conclude that in experimental model of sepsis, the use of propofol anesthetics is less noxious for the lung parenchyma when compared to inhaled isoflurane anesthetics. Introdution Anesthesia is a reversible condition of comfort, stability and physiological immobility of the patient before, during and after a surgical procedure (Goodman & Gilman In 2005). One of the fundamental ways of achieving the basic conditions of anesthesia is through the use of general anesthetics, which act on the pain associated with loss of consciousness. Propofol (2,6-diisopropylphenol) is a general anesthetic of the intravenous type, insoluble, which is administered in the form of emulsion and metabolized by the liver in the inactive forms of sulfates and glucuronides that are excreted through the kidneys (Barbosa, 2007). This anesthetic confers antioxidant activity and is commonly used to induce and maintain general anesthesia (Green et al., 1994, Chung et al., 2011). Studies have shown that the use of general anesthetics can 2012 by MEDIMOND s.r.l. P212C

2 148 XXII International Symposium on Morphological Sciences modulate the inflammatory response by inhibiting the production of pro-inflammatory cytokines, but the mechanism of action of these drugs in sepsis still remains poorly understood (Chung et al., 2011). Another form of general anesthetics is inhaled, which make use of a combination of gas and volatile liquid, generally esters. These are administered according to the pathophysiology of the patient, associated with the profiles of the drug s side effects (Nora, 2008). Isoflurane (1-chloro-2,2,2-trifluoroethyl ether), is a widespread anesthetic due to rapid induction and post-anesthetic recovery, besides its approximately 99% unchanged elimination by lung (Inge et al., 2007). In current clinical practice, an extremely important factor in reducing post-surgical complications is the precautions against installation and the possible proliferation of an inflammatory process. However, when such process occurs, the vascularized tissues respond physiologically to the injury via soluble mediators and cellular components that will work together to attempt to contain and eliminate the causative agents of such injury (Abbas and Lichtman., 2005). Tissue damage caused by these agents triggers a series of molecular events resulting in the production of pro-inflammatory mediators, including cytokines, which recruit neutrophils, as well as generation of free radicals, all contributing to the oxidative stress leading to tissue injury (Victor et al, 2004, Yu et al., 2002). The engagement of leukocytes to tissues is extremely important in the response to inflammation, however exacerbated accumulation of these cells in tissues can cause a variety of pathologies, among which a diversity of tissue injury, such as the kidney and lung (Chopra et al., 2009). Some cases of acute lung injury may be associated with forms of sepsis, caused mainly by increased lung microvascular permeability (Xie et al.,1997, Xie et al, 2000). Sepsis is characterized by a systemic inflammatory response to infection and is associated with multiple organic factors (Chen at al., 2005). Production of chemokines and pro-inflammatory cytokines at the site of inflammation is an important factor for the engagement and activation of leukocytes (Echtenacher et al., 1990; Bagby et al., 1991; Eskandari, et al., 1992). However, high levels of some of these cytokines may cause a systemic inflammatory response syndrome (SIRS), multi-organic dysfunction culminating in an increase in morbidity and mortality of individuals (Martineau et al., 2000). In the body s response to installation of a sepsis, neutrophils represent the first line of defense against agents known to cause these processes, and its main function is to protect the host from injuries caused by the invading microorganisms. In surgical procedures, these cells have a key role in reducing the risk of inflammation during and after surgical trauma (Stevenson et al., 1990; Wakefield et al., 1993). There is, however, evidence of interference of general anesthetics on the inflammatory response (Stevenson et al., 1990), under which light this study is aimed at evaluating the effect of general anesthetics propofol and isoflurane on the morphology of the lung in septic mice. Materials and methods This experiment was approved by ethics committee on the use of animals at the Federal University of Rio Grande do Norte, UFRN, Brazil, under reference number 036/2009. A total of 45 male mice of the Swiss strain were used, weighing 30 ± 5g. The animals were divided into three groups: a negative control group, other group submitted to anesthesia with propofol and another with isoflurane. Sepsis was induced by the CLP technique (cecal ligation puncture) as described by Benjamin et al, 2002,

3 Sao Paulo, Brazil, February, Figure 1 Migration of sepsis-induced inflammatory cells into the peritoneal cavity in mice using the propofol (intravenous) and isoflurane (inhaled). with some modifications. The mice were anaesthetized intravenously with propofol anesthetic and using the Oxigel 717/0101, fan 1530 inhalant anesthesia apparatus for the isoflurane. After the 8 hours interval of sepsis induction, the animals were sacrificed and underwent peritoneal wash with 5 ml of sterile saline solution at 0.9% and subsequent cell count in a Neubauer chamber. For analysis of cell migration to the lungs of the animals, an opening was made on the trachea and 1.0 ml of saline was injected through a cannula and the solution immediately aspirated for cell count. Once the washing procedure was completed, the lungs were removed for histological analysis. For statistical analyzes of the results we used ANOVA and Tukey s tests using the Sigma Stat version V. 3.10, 2004 program. Results After the cell count of peritoneal wash, significant statistical differences were observed between all groups (p < 0.05). Fig 1. When compared to the count of inflammatory cells in bronchoalveolar wash fluid, no significant differences were observed between control and propofol groups (p > 0.05), but a significant difference (p< 0.001) was observed when the propofol group was compared to isoflurane - Fig 2. When the histological analysis of the lungs was performed, it was found that the animals anesthetized with propofol presented greater parenchyma integrity, with few

4 150 XXII International Symposium on Morphological Sciences Figure 2 Migration of sepsis-induced inflammatory cells to the lung. Figure 3 Histological analysis of lung parenchyma in the control group (A) and propofol group (B). ruptured terminal bronchioles. The isoflurane group, however, presented rupture of the alveolar epithelium and absence of intact bronchioles (Fig. 3 and 4). Discussion Selection of anesthetics for use in surgical procedures is based on a combination

5 Sao Paulo, Brazil, February, Figure 4 Histological analysis of lung parenchyma in the control group (A) and isoflurane group (C) of the type of surgery, the pathophysiology of the patient and the side effects of the drug, but the choice of anesthetic does not depend only on these factors. From the results found in this study, emphasis should be given to the importance of evaluating the pro-inflammatory or anti-inflammatory effects that general anesthetics can induce. This is because these drugs are known to act on the modulation of inflammatory response and the deleterious effects on tissue, depending of the anesthetics used, may contribute to increased morbidity or mortality of patients, especially those with a clinical history of respiratory diseases. Considering the results achieved in this study, we conclude that the anesthetic propofol, administered intravenously, gave greater protection of the operated animals, agreeing with the findings of Chung et al, 2011, who observed that the anesthetic propofol efficiently protected the renal tissue in a model of sepsis by efficiently inhibiting the expression of TNF- and MCP-1 in septic mice when induced by LPS. Also in their studies, Chung found that propofol reduced the generation of free radicals and cell death when stimulated by LPS. Studies by Heemskerk et al., 1997; Kohan et al., 1994 and Zager et al. 2006, using a kidney injury test, have also shown that propofol significantly inhibited the expression of cytokines and chemokines that recruit neutrophils to the tissue, which eventually provided protection to the tissue. Conclusion The results obtained in this study confirm the effectiveness of the anesthetic propofol, which was more efficient in tissue protection in comparison to isofluran, due to its minor effect on cell migration over the site of inflammation and significantly reduced the tissue damage. Bibliographic References CHING-HUA YEH, CHUNG-HIS HSING, WILLY CHOU et al. Propofol increases bone morphogenetic protein-7 and decreases oxidative stress in sepsis-induced acute kidney injury. Nephrol Dial Transplant; 26: , 2010.

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