Continuous Heliox Breathing and the Extent of Anatomic Zone of Noreflow and Necrosis Following Ischemia/Reperfusion in the Rabbit Heart

Abstract

Background:Nitrogen may contribute to reperfusion injury. Some studies have shown that helium as a replacement for nitrogen in breathing gas (heliox) reduces cell necrosis after ischemia/reperfusion when used in a preconditioning fashion (intermittent heliox exposure). Our aim was to test whether heliox, breathed continuously throughout the ischemic and reperfusion periods, reduced necrosis and a marker of reperfusion injury, the no-reflow phenomenon.Methods and Results:Anesthetized, open-chest rabbits received 30 min coronary artery occlusion/3 hrs reperfusion. Before CAO rabbits were randomized to heliox (30% oxygen + 70% helium, n=8) or air supplemented with oxygen to achieve blood gas values within physiologic range (n = 8). Rabbits received the appropriate mix during ischemic and reperfusion periods. Infarct size (% risk zone) and no-reflow defect were measured at the end of the reperfusion period. The ischemic risk zone was similar in both groups (28% of left ventricle in heliox and 29% in control). Heliox breathing did not reduce necrosis; infarct size, expressed as a percentage of the risk region was 44±4% in the heliox group and 49±5% in controls, p = 0.68. The extent of the no-reflow defect was not altered by heliox, either expressed as a percent of the risk region (29±4% in heliox and 28±3% in control) or as a percent of the necrotic zone (65±5% in heliox and 59±8% in control).Heliox treatment had no effect on hemodynamic parameters or arterial blood gas values.Conclusion:Continuous heliox breathing does not appear to be cardioprotective in the setting of acute myocardial infarction in the rabbit model. Heliox respiration administered during 30 minutes of ischemia and 180 minutes of reperfusion did not alter infarct size or the extent of no-reflow.

A randomized single‐center controlled trial of synchronized intermittent mandatory ventilation with heliox in newborn infants with meconium aspiration syndrome

“…Helium, which has a low density and high viscosity and mobility due to its physical properties contributing to smaller resistance, is useful in the treatment of MAS to significantly increase ventilation per minute and the expiratory flow, reduce power consumption due to breathing, accelerate the dispersion of oxygen and CO 2 , and improve lung compliance 28–32 . SIMV produces more synchronization and fewer cardiovascular complications in the treatment of MAS 33,34 . The physical characteristics of heliox, that is, low density, are more suitable for the narrow respiratory tract of newborns and can effectively elevate the blood oxygen content 35–37 .…”

“…In the present study, the inflammation markers in the heliox group were improved compared with those in the control group. Helium also has protective effects in experimental cardiac ischemia reperfusion 33,34,40 . Infants with MAS are often complicated with myocardial damage, and laboratory examinations revealed a multifold rise in the myocardial enzyme profile.…”

Reduction of Cardiac Cell Death after Helium Postconditioning in Rats: Transcriptional Analysis of Cell Death and Survival Pathways

“…Again, this is in line with results from infarct size experiments analyzed by TTC staining, in which 30 min of helium during early reperfusion abrogated the protection that was seen after 15 min of HePOC (26). Prolonged episodes of helium inhalation did not protect the rabbit heart against I/R (27), neither did prolonged helium inhalation protect forearm endothelium in a study with male human volunteers (28).…”

Prolonged Helium Postconditioning Protocols during Early Reperfusion Do Not Induce Cardioprotection in the Rat HeartIn Vivo: Role of Inflammatory Cytokines

“…This is a relevant finding when helium-induced cardioprotection would be translated to clinical practice; apparently helium postconditioning is sensitive to the length of helium inhalation. Prolonged helium inhalation during ischemia and 180 min of reperfusion has shown not to reduce infarct size or extent of no-reflow in rabbits [ 13 ]. The negative effects of this study could also be caused by the timing of helium application, inhalation starting at the onset of the ischemic episode.…”