A complete review of preclinical and clinical uses of the noble gas argon: Evidence of safety and protection

The noble gas argon (Ar) is a “biologically” active element and has been extensively studied preclinically for its organ protection properties. This work reviews all preclinical studies employing Ar and describes the clinical uses reported in literature, analyzing 55 pertinent articles found by means of a search on PubMed and Embase. Ventilation with Ar has been tested in different models of acute disease at concentrations ranging from 20% to 80% and for durations between a few minutes up to days. Overall, lesser cell death, smaller infarct size, and better functional recovery after ischemia have been repeatedly observed. Modulation of the molecular pathways involved in cell survival, with resulting anti-apoptotic and pro-survival effects, appeared as the determinant mechanism by which Ar fulfills its protective role. These beneficial effects have been reported regardless of onset and duration of Ar exposure, especially after cardiac arrest. In addition, ventilation with Ar was safe both in animals and humans. Thus, preclinical and clinical data support future clinical studies on the role of inhalatory Ar as an organ protector.

Anesthetic management of transcatheter aortic valve implantation.

Transcatheter aortic valve implantation (TAVI) is an emergent technique for high-risk patients with aortic stenosis. TAVI poses significant challenges about its management because of the procedure itself and the population who undergo the implantation. Two devices are currently available and marketed in Europe and several other technologies are being developed. The retrograde transfemoral approach is the most popular procedure; nevertheless, it may not be feasible in patients with significant aortic or ileo-femoral arterial disease. Alternatives include a transaxillary approach, transapical approach, open surgical access to the retroperitoneal iliac artery and the ascending aorta. A complementary approach using both devices and alternative routes tailored to the anatomy and the comorbidities of the single patient is a main component for the successful implementation of a TAVI program. Anesthetic strategies vary in different centers. Local anesthesia or general anesthesia are both valid alternatives and can be applied according to the patient's characteristics and procedural instances. General anesthesia offers many advantages, mainly regarding the possibility of an early diagnosis and treatment of possible complications through the use of transesophageal echocardiography. However, after the initial experiences, many groups began to employ, routinely, sedation plus local anesthesia for TAVI, and their procedural and periprocedural success demonstrates that it is feasible. TAVI is burdened with potential important complications: vascular injuries, arrhythmias, renal impairment, neurological complications, cardiac tamponade, prosthesis malpositioning and embolization and left main coronary artery occlusion. The aim of this work is to review the anesthetic management of TAVI based on the available literature.

Remifentanil in critically ill cardiac patients.

Remifentanil has a unique pharmacokinetic profile, with a rapid onset and offset of action and a plasmatic metabolism. Its use can be recommended even in patients with renal impairment, hepatic dysfunction or poor cardiovascular function. A potential protective cardiac preconditioning effect has been suggested. Drug-related adverse effects seem to be comparable with other opioids. In cardiac surgery, many randomized controlled trials demonstrated that the potential benefits of the use of remifentanil not only include a profound protection against intraoperative stressful stimuli, but also rapid postoperative recovery, early weaning from mechanical ventilation, and extubation. Remifentanil shows ideal properties of sedative agents being often employed for minimally invasive cardiologic techniques, such as transcatheter aortic valve implantation and radio frequency treatment of atrial flutter, or diagnostic procedures such as transesophageal echocardiography. In intensive care units remifentanil is associated with a reduction in the time to tracheal extubation after cessation of the continuous infusion; other advantages could be more evident in patients with organ dysfunction. Effective and safe analgesia can be provided in case of short and painful procedures (i.e. chest drain removal). In conclusion, thanks to its peculiar properties, remifentanil will probably play a major role in critically ill cardiac patients.