The volatile anesthetic sevoflurane inhibits activation of neutrophil granulocytes during simulated extracorporeal circulation

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Abstract

Extracorporeal circulation (ECC) is an essential tool for the execution of cardiac operations. However, ECC is also associated with undesirable side effects. These include the induction of a systemic inflammatory response associated with leukocyte activation and cytokine release as well as potentially life-threatening complications. The volatile anesthetic sevoflurane has been reported to exert anti-ischemic and anti-inflammatory effects. We therefore investigated whether sevoflurane modulates the ECC-triggered inflammatory response.

Heparinized human blood was circulated for 90 min in a normothermic (37 °C) ex vivo ECC circuit. An air–oxygen mixture was administered via an oxygenator in controls (n = 5). Sevoflurane (2 vol.%) was added to the gas mixture in a second group (n = 5). At baseline and after 30, 60 and 90 min of ECC, blood samples were taken. In each sample whole blood counts were determined. Expression of the activation-indicating Mac-1 receptor on granulocytes and monocytes as well as leukocyte–platelet aggregate formation was measured in flow cytometry. Levels of the granulocyte activation marker PMN-elastase and of the cytokines IL-1β, IL-8 and TNF-α were analyzed using ELISA.

ECC induced significant increases in Mac-1 expression on granulocytes (p < 0.001) and PMN-elastase release (p < 0.001). Sevoflurane decreased granulocyte Mac-1 expression during ECC (p < 0.05) and inhibited the ECC-induced PMN-elastase release (p < 0.05). Sevoflurane had no effect on whole blood cell counts, leukocyte–platelet aggregate formation and cytokine release during ECC.

Sevoflurane inhibits granulocyte activation during ex vivo ECC and therefore has the potential to decrease the ECC-triggered inflammatory response. This promising finding warrants further investigation under clinical conditions.

Highlights

► Extracorporeal circulation (ECC) induces granulocyte activation associated with systemic inflammation. ► The volatile anesthetic sevoflurane inhibits granulocyte activation during ex vivo ECC. ► Sevoflurane has the potential to decrease the ECC-triggered inflammatory response in clinical routine.

Introduction

Extracorporeal circulation (ECC) is employed in many cardiac surgical procedures to maintain stable circulatory parameters of the patient. Therefore, ECC is an essential tool for the successful execution of cardiac operations. However, ECC is also associated with adverse side effects. These include the induction of a systemic inflammatory response caused by the contact of blood components with the artificial surfaces of the ECC circuit. ECC-associated inflammation can result in potentially life-threatening complications including dysfunction of lung, myocardium, kidney and liver, which can cause multi-organ failure and significant mortality [1], [2], [3], [4].

The mechanism of ECC-induced inflammation is multifactorial. ECC causes activation of white blood cells including neutrophil granulocytes and results in release of inflammatory mediators including cytokines [1]. Upon activation neutrophils upregulate surface expression of the Mac-1 receptor (CD11b/CD18) and release cytotoxic enzymes including polymorphonuclear (PMN) elastase from intracellular granules into their surrounding [4].

Volatile anesthetics including sevoflurane have been reported to protect the myocardium against ischemia as well as reperfusion injury in clinical [5] and experimental studies [3]. Furthermore, it has been reported that sevoflurane may have the potential to inhibit pro-inflammatory events in the setting of cardiac surgery [6]. Nevertheless, it is unclear whether routine administration of sevoflurane in concentrations employed during balanced anesthesia may also inhibit ECC-induced inflammation.

On this background, the aim of our study was to investigate whether sevoflurane administration may modulate the ECC-triggered inflammatory response during ex vivo ECC. Sevoflurane was administered via the oxygenator of the ECC circuit according to standard clinical procedures. The effect of sevoflurane on the activation of leukocytes, their interaction with platelets and on cytokine release was investigated.

Section snippets

Methods

Study and blood sampling procedures were approved by the Research and Ethics Unit of the University of Tübingen, Germany (project number 270/2010BO1, approval date: 05/02/2011). Written informed consent was obtained from all subjects before blood sampling.

Effect of ECC and sevoflurane on whole blood cell counts

Addition of the ECC priming volume to whole blood results in hemodilution. In order to investigate the extent of ECC-induced hemodilution in our experiments, whole blood counts were determined. Compared to undiluted baseline values, similar decreases of hematocrit, erythrocyte and white blood cell as well as platelet counts after start of ECC were observed for controls and sevoflurane-treated samples.

Sevoflurane treatment had no further effect on whole blood count parameters (Fig. 1A–D).

Sevoflurane decreases Mac-1 expression on granulocytes during ECC

The

Discussion

In our current study, we investigated the effect of the volatile anesthetic sevoflurane on inflammatory events during ex vivo ECC. To address this topic, we systematically analyzed blood cell counts, release of leukocyte activation markers, leukocyte–platelet binding and generation of pro-inflammatory cytokines. Our results clearly indicate that ECC induces Mac-1 expression on neutrophil granulocytes and PMN-elastase release. Notably, both ex vivo ECC-induced effects were inhibited by treatment

Conflicts of interest and sources of funding

This work was funded from internal financial resources of the Department of Anesthesiology and Intensive Care Medicine in Tübingen.

The authors report no conflicts of interest.

References (31)

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Authors contributed equally to this work.

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