Supplemental remifentanil during coronary artery bypass grafting is followed by a transient postoperative cardiac depression

[Cardioprotection in cardiac surgical patients : Everything good comes from the heart]

BACKGROUND

Despite substantial success in the anesthetic and surgical management of cardiac surgery, patients frequently show postoperative complications and organ dysfunctions. This is highly relevant for mid- to long-term outcomes.

OBJECTIVES

To evaluate cardioprotective strategies that may offer effective protection in vulnerable cardiac surgery patients.

METHODS

To demonstrate recent cardioprotective approaches for cardiac surgery patients, aiming to modulate the body's own protective mechanisms in cardiac surgery patients.

RESULTS

Both cardioplegia and hypothermia belong to the well-established protective strategies during myocardial ischemia. Volatile anesthetics have been repeatedly shown to improve the left ventricular function and reduce the extent of myocardial injury compared to a control group with intravenous anesthesia. Furthermore, patients receiving volatile anesthetics showed a significantly shortened stay in the ICU and in hospital after cardiac surgery. In contrast, numerous other protective strategies failed translation into the clinical practice. Despite the published reduction of troponin release after remote ischemic preconditioning, two recent large-scale randomized multicenter trials were unable to demonstrate a clinical benefit.

CONCLUSIONS

Beside the use of cardioplegia and hypothermia, the use of volatile anesthetics is well-established during cardiac surgery because of its conditioning and protective properties. Regardless of the promising results derived from experimental studies and small clinical trials, the majority of other approaches failed to translate their findings into the clinic. Therefore, systematic experimental studies are needed to identify potential confounding factors that may affect the protective effects.

Peri-operative cardiac protection for non-cardiac surgery

Cardiovascular complications are an important cause of morbidity and mortality after non-cardiac surgery. Pre-operative identification of high-risk individuals and appropriate peri-operative management can reduce cardiovascular risk. It is important to continue chronic beta-blocker and statin therapy. Statins are relatively safe and peri-operative initiation may be beneficial in high-risk patients and those scheduled for vascular surgery. The pre-operative introduction of beta-blockers reduces myocardial injury but increases rates of stroke and mortality, possibly due to hypotension. They should only be considered in high-risk patients and the dose should be titrated to heart rate. Alpha-2 agonists may also contribute to hypotension. Aspirin continuation can increase the risk of major bleeding and offset the benefit of reduced myocardial risk. Contrary to the initial ENIGMA study, nitrous oxide does not seem to increase the risk of myocardial injury. Volatile anaesthetic agents and opioids have been shown to be cardioprotective in animal laboratory studies but these effects have, so far, not been conclusively reproduced clinically.

Pharmacological and nonpharmacological treatment after cardiac surgery

Open-heart surgery has become a common procedure. Postcardiac surgery management is a critical issue and represents a crucial period in terms of physical recovery. Cardiac rehabilitation is increasingly considered as an integral component of the continuum of care for patients with cardiovascular disease. Its usefulness is now widely accepted, and therefore, it is recommended in most contemporary cardiovascular clinical practice guidelines. Similarly, early pharmacological management can modulate the pathophysiological alterations after cardiac surgery, leading to an improvement in the early and long-term outcome. In this review, we will present recent advances in postcardiac surgery management, focusing on the pathophysiology of the perioperative period and on recent evidences in pharmacological and rehabilitative strategies.

Morphine and remifentanil-induced cardioprotection: its experimental and clinical outcomes

During the past few decades, a large number of animal studies demonstrated that commonly used opioids could provide cardioprotection against ischemia-reperfusion (I/R) injury. Opioid-induced preconditioning or postconditioning mimics ischemic preconditioning (I-Pre) or ischemic postconditioning (I-Post). Both δ- and κ-opioid receptors (OPRs) play a crucial role in opioid-induced cardioprotection (OIC). Down stream signaling effectors of OIC include ATP-sensitive potassium (K_ATP) channels, protein kinase C (PKC), tyrosine kinase, phosphatidylinositol-3-kinase (PI3-kinase), extracellular signal regulated kinase1/2 (ERK1/2), glycogen synthase kinase-3β (GSK-3β), and mitochondrial permeability transition pore (MPTP), among others. Recently, various reports also suggest that opioids could provide cardioprotection in humans. This review will discuss OIC using mostly morphine and remifentanil which are widely used during cardiac anesthesia in addition to the clinical implications of OIC.

Remifentanil in cardiac surgery: a meta-analysis of randomized controlled trials

OBJECTIVE

The authors conducted a review of randomized controlled trials to identify advantages in clinically relevant outcomes in patients undergoing cardiac surgery with remifentanil.

DESIGN

Meta-analysis.

SETTING

Hospitals.

PARTICIPANTS

A total of 1,473 patients from 16 randomized trials.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULT

PubMed, BioMedCentral, and conference proceedings were searched (updated May 2010) for randomized trials that compared remifentanil with fentanyl or sufentanil in cardiac anesthesia. Four independent reviewers performed data extraction, with divergences resolved by consensus. Overall analysis showed that the use of remifentanil was associated with a significant reduction in postoperative mechanical ventilation (WMD = -139 min [-244, -32], p for effect = 0.01, p for heterogeneity < 0.001, I(2) = 89%); length of hospital stay (WMD = -1.08 days [-1.60, -0.57], p for effect < 0.0001, p for heterogeneity = 0.004, I(2) = 71%); and cardiac troponin-I release (WMD = -2.08 ng/mL [-3.93, -0.24], p for effect = 0.03, p for heterogeneity < 0.02, I(2) = 74%). No difference was noted in mortality (3/344 [0.87%] in the remifentanil group vs [1.06%] the control group, OR 0.76 [0.17-3.38], p for effect = 0.72, p for heterogeneity = 0.35, I(2) = 5%).

CONCLUSIONS

Remifentanil reduces cardiac troponin release, time of mechanical ventilation, and length of hospital stay in patients undergoing cardiac surgery.

Perioperative metabolic changes in patients undergoing cardiac surgery

Perioperative metabolic changes in cardiac surgical patients are not only induced by tissue injury and extracorporeal circulation per se: the systemic inflammatory response to surgical trauma and extracorporeal circulation, perioperative hypothermia, cardiovascular and neuroendocrine responses, and drugs and blood products used to maintain cardiovascular function and anesthesia contribute to varying degrees. The pathophysiologic changes include increased oxygen consumption and energy expenditure; increased secretion of adrenocorticotrophic hormone, cortisol, epinephrine, norepinephrine, insulin, and growth hormone; and decreased total tri-iodothyronine levels. Easily measurable metabolic consequences of these changes include hyperglycemia, hyperlactatemia, increased aspartate, glutamate and free fatty acid concentrations, hypokalemia, increased production of inflammatory cytokines, and increased consumption of complement and adhesion molecules. Nutritional risk before elective cardiac surgery-defined as preoperative unintended pathologic weight loss/low amount of food intake in the preceding week or low body mass index-is related to adverse postoperative outcome. Improvements in surgical techniques, anesthesia, and perioperative management have been designed to minimize the stressful stimulus to catabolism, thereby slowing the wasting process to the point where much less nutrition is required to meet metabolic requirements. Early nutrition in cardiac surgery is safe and well tolerated.

Remifentanil-induced mechanical responses and membrane potential changes in human umbilical arteries

BACKGROUND

The aim of this study was to evaluate the characteristic features of the mechanical responses and membrane potential changes induced by remifentanil in human umbilical arteries (HUAs). The ionic mechanisms underlying the electrophysiological responses were pharmacologically assessed using two K(+) channel blockers.

METHODS

Thirty-eight HUAs were obtained. Contraction-relaxation, membrane potential changes and electrical responses of the HUAs were recorded.

RESULTS

Remifentanil produced concentration-dependent relaxation in both endothelium-intact and endothelium-denuded HUA rings. Remifentanil produced a significantly greater relaxation response in intact than in denuded HUA rings. In endothelium-intact rings, pre-treatment with L-nitroarginine [N(w)-NITRO-(L)-ARGININE (L-NO-ARG)] or indomethacin decreased the degree of remifentanil-induced relaxation. Remifentanil (10(-9)-10(-6) mol/l) produced a transient concentration-dependent membrane hyperpolarization, which was not decreased by pre-treatment with L-NO-ARG or indomethacin. It also produced a small concentration-dependent hyperpolarization in the presence of charybdotoxin or tetraethylammonium.

CONCLUSION

In both endothelium-intact and endothelium-denuded HUAs, remifentanil induces concentration-dependent vasorelaxation and simultaneously releases nitric oxide, prostaglandins and possibly an endothelium-derived hyperpolarizing factor. In addition, it produces hyperpolarization in a dose-dependent manner. Hyperpolarization induced by remifentanil involves the activation of Ca(2+)-dependent and Ca(2+)-independent potassium channels regulated by intracellular Ca(2+).