[Myocardial preconditioning with volatile anesthetics. General anesthesia as protective intervention?]

[Inhalational anesthetics]

Inhalational anesthetics have been used for induction and maintenance of general anesthesia for more than 150 years. All of the currently used inhalational anesthetics are chlorinated and fluorinated derivatives of ether. Dosing is carried out using the minimal alveolar concentration (MAC) concept. The pharmacokinetic properties of the various inhalational anesthetics are governed by the specific distribution coefficients. Mechanisms of action include specific modulations of various receptors of the central nervous system as well as an unspecific interaction with the cell membrane. Organ toxicity of modern inhalational anesthetics is considered to be minimal. The role of inhalational anesthetics in the context of postoperative nausea and vomiting (PONV) has been reassessed in recent years. The superiority of inhalational anesthetics over intravenous hypnotics with respect to intraoperative awareness is undisputed. The organ protective mechanism of preconditioning is an exclusive property of inhalational anesthetics among all the currently available hypnotics.

The mechanisms of cardio-protective effects of desflurane and sevoflurane at the time of reperfusion: anaesthetic post-conditioning potentially translatable to humans?

Myocardial conditioning is actually an essential strategy in the management of ischaemia-reperfusion injury. The concept of anaesthetic post-conditioning is intriguing, its action occurring at a pivotal moment (that of reperfusion when ischaemia reperfusion lesions are initiated) where the activation of these cardio-protective mechanisms could overpower the mechanisms leading to ischaemia reperfusion injuries. Desflurane and sevoflurane are volatile anaesthetics frequently used during cardiac surgery. This review focuses on the efficacy of desflurane and sevoflurane administered during early reperfusion as a potential cardio-protective strategy. In the context of experimental studies in animal models and in human atrial tissues in vitro, the mechanisms underlying the cardio-protective effect of these agents and their capacity to induce post-conditioning have been reviewed in detail, underlining the role of reactive oxygen species generation, the activation of the cellular signalling pathways, and the actions on mitochondria along with the translatable actions in humans; this might well be sufficient to set the basis for launching randomized clinical studies, actually needed to confirm this strategy as one of real impact.

Decreased effectiveness of ischemic heart preconditioning in the state of chronic inflammation

There is growing evidence, that beneficial effects of ischemic heart preconditioning (IPC) may be lost or limited due to diabetes, hyperlipidemia, hypertension, atherosclerosis, heart failure and senility. It is plausible, that these conditions interfere with the biochemical pathways underlying the IPC response, but the detailed explanation is not clear. Pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), monocyte chemotactic protein-1 (MCP-1), histamine and many other agents used in a single dose before prolonged ischemia mimic IPC. However prolonged exposure to preconditioning mimetics leads to tolerance (tachyphylaxis). In the state of such tolerance ischemic preconditioning is no longer protective. Studies suggest that diabetes, hyperlipidemia, hypertension, atherosclerosis, heart failure and older age are accompanied by increased plasma levels of pro-inflammatory cytokines, MCP-1 and other inflammatory mediators. Therefore, we raised the hypothesis, that the reported lack of benefits of IPC in the listed states may be due to tolerance to IPC developed during prolonged exposure of the myocardium to preconditioning mimetics.

Effects of hyperoncotic or hypertonic-hyperoncotic solutions on polymorphonuclear neutrophil count, elastase- and superoxide-anion production: a randomized controlled clinical trial in patients undergoing elective coronary artery bypass grafting

BACKGROUND

Hypertonic-hyperoncotic solutions may be an effective treatment for systemic inflammatory response syndrome (SIRS). With regard to the immunomodulatory effects of these drugs, previous studies demonstrated controversial results. Therefore, the present study investigated the influence of different hyperoncotic and hypertonic-hyperoncotic solutions on polymorphonuclear neutrophil leukocyte (PMNL) count, elastase and superoxide-anion production in patients undergoing elective coronary artery bypass grafting (CABG) with cardiopulmonary bypass.

METHODS

Fifty patients scheduled for elective CABG with cardiopulmonary bypass were randomly assigned to five groups: (i) NaCl 0.9%, 750 ml/m(2) body surface area (BSA); (ii) hydroxyethylic starch 10%, 250 ml/m(2) BSA and NaCl 0.9%, 400 ml/m(2) BSA; (iii) dextran 10%, 250 ml/m(2) BSA and NaCl 0.9%, 300 ml/m(2) BSA; (iv) hypertonic sodium chloride 7.2%/hyperoncotic hydroxyethylic starch 10%, 150 ml/m(2) BSA; and (v) hypertonic sodium chloride 7.2%/hyperoncotic dextran 10%, 150 ml/m(2) BSA. Blood samples were drawn from arterial, central venous and coronary artery sinus catheters peri-operatively. PMNL count, superoxide-anion production and elastase were recorded.

RESULTS

PMNL counts and elastase activity increased in all groups after reperfusion. Superoxide-anion production showed only minor changes. Between groups, no significant differences were demonstrated.

CONCLUSIONS

Infusion of clinically relevant doses of hypertonic-hyperoncotic solution did not affect PMNL count, elastase- or superoxide-anion production during elective CABG with cardiopulmonary bypass.