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Mild hypothermia reduces cardiac post-ischemic reactive hyperemia.

Olivecrona GK, Götberg M, Harnek J, Van der Pals J, Erlinge D - BMC Cardiovasc Disord (2007)

Bottom Line: The LAD was then occluded for ten minutes in all pigs.The peak flow seen during post-ischemic reactive hyperemia (during the first minutes of reperfusion) was significantly reduced by 43 % (p < 0.01) in hypothermic pigs compared to controls.Mild hypothermia significantly reduces post-ischemic hyperemia in a closed chest pig model.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cardiology, Lund University, Lund, Sweden. goran.olivecrona@med.lu.se <goran.olivecrona@med.lu.se>

ABSTRACT

Background: In experimentally induced myocardial infarction, mild hypothermia (33-35 degrees C) is beneficial if applied prior to ischemia or reperfusion. Hypothermia, when applied after reperfusion seems to confer little or no benefit. The mechanism by which hypothermia exerts its cell-protective effect during cardiac ischemia remains unclear. It has been hypothesized that hypothermia reduces the reperfusion damage; the additional damage incurred upon the myocardium during reperfusion. Reperfusion results in a massive increase in blood flow, reactive hyperemia, which may contribute to reperfusion damage. We postulated that hypothermia could attenuate the post-ischemic reactive hyperemia.

Methods: Sixteen 25-30 kg pigs, in a closed chest model, were anesthetized and temperature was established in all pigs at 37 degrees C using an intravascular cooling catheter. The 16 pigs were then randomized to hypothermia (34 degrees C) or control (37 degrees C). The left main coronary artery was then catheterized with a PCI guiding catheter. A Doppler flow wire was placed in the mid part of the LAD and a PCI balloon was then positioned proximal to the Doppler wire but distal to the first diagonal branch. The LAD was then occluded for ten minutes in all pigs. Coronary blood flow was measured before, during and after ischemia/reperfusion.

Results: The peak flow seen during post-ischemic reactive hyperemia (during the first minutes of reperfusion) was significantly reduced by 43 % (p < 0.01) in hypothermic pigs compared to controls.

Conclusion: Mild hypothermia significantly reduces post-ischemic hyperemia in a closed chest pig model. The reduction of reactive hyperemia during reperfusion may have an impact on cardiac reperfusion injury.

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Related in: MedlinePlus

Base excess (BE) collected in a peripheral artery and the Coronary Sinus. Base excess (BE) was measured in a peripheral artery (A) and in the Coronary Sinus (CS), (B). There was no difference between normothermic (n = 8) and hypothermic pigs at baseline. During early (+1 minute) and late (+10 minutes) reperfusion there was a significant reduction in BE in the normothermic group in samples from the peripheral artery (A). In samples from the CS, there was a marked reduction in BE in both groups during early reperfusion, which then nearly returned back to baseline at late reperfusion with no difference between the groups (B).
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Figure 3: Base excess (BE) collected in a peripheral artery and the Coronary Sinus. Base excess (BE) was measured in a peripheral artery (A) and in the Coronary Sinus (CS), (B). There was no difference between normothermic (n = 8) and hypothermic pigs at baseline. During early (+1 minute) and late (+10 minutes) reperfusion there was a significant reduction in BE in the normothermic group in samples from the peripheral artery (A). In samples from the CS, there was a marked reduction in BE in both groups during early reperfusion, which then nearly returned back to baseline at late reperfusion with no difference between the groups (B).

Mentions: Blood gas analysis showed a significant decrease in peripheral arterial base excess (BE) at one and ten minutes following reperfusion in the control group compared to the hypothermic group, (Figure 3a). Samples collected in the Coronary Sinus showed a prominent reduction in BE in both groups at one minute after reperfusion. BE did not differ significantly between the groups (Figure 3b). Other measurements of blood gas analysis did not show any significant differences in regard to O2 saturation or pH between the groups (not shown).


Mild hypothermia reduces cardiac post-ischemic reactive hyperemia.

Olivecrona GK, Götberg M, Harnek J, Van der Pals J, Erlinge D - BMC Cardiovasc Disord (2007)

Base excess (BE) collected in a peripheral artery and the Coronary Sinus. Base excess (BE) was measured in a peripheral artery (A) and in the Coronary Sinus (CS), (B). There was no difference between normothermic (n = 8) and hypothermic pigs at baseline. During early (+1 minute) and late (+10 minutes) reperfusion there was a significant reduction in BE in the normothermic group in samples from the peripheral artery (A). In samples from the CS, there was a marked reduction in BE in both groups during early reperfusion, which then nearly returned back to baseline at late reperfusion with no difference between the groups (B).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1808476&req=5

Figure 3: Base excess (BE) collected in a peripheral artery and the Coronary Sinus. Base excess (BE) was measured in a peripheral artery (A) and in the Coronary Sinus (CS), (B). There was no difference between normothermic (n = 8) and hypothermic pigs at baseline. During early (+1 minute) and late (+10 minutes) reperfusion there was a significant reduction in BE in the normothermic group in samples from the peripheral artery (A). In samples from the CS, there was a marked reduction in BE in both groups during early reperfusion, which then nearly returned back to baseline at late reperfusion with no difference between the groups (B).
Mentions: Blood gas analysis showed a significant decrease in peripheral arterial base excess (BE) at one and ten minutes following reperfusion in the control group compared to the hypothermic group, (Figure 3a). Samples collected in the Coronary Sinus showed a prominent reduction in BE in both groups at one minute after reperfusion. BE did not differ significantly between the groups (Figure 3b). Other measurements of blood gas analysis did not show any significant differences in regard to O2 saturation or pH between the groups (not shown).

Bottom Line: The LAD was then occluded for ten minutes in all pigs.The peak flow seen during post-ischemic reactive hyperemia (during the first minutes of reperfusion) was significantly reduced by 43 % (p < 0.01) in hypothermic pigs compared to controls.Mild hypothermia significantly reduces post-ischemic hyperemia in a closed chest pig model.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cardiology, Lund University, Lund, Sweden. goran.olivecrona@med.lu.se <goran.olivecrona@med.lu.se>

ABSTRACT

Background: In experimentally induced myocardial infarction, mild hypothermia (33-35 degrees C) is beneficial if applied prior to ischemia or reperfusion. Hypothermia, when applied after reperfusion seems to confer little or no benefit. The mechanism by which hypothermia exerts its cell-protective effect during cardiac ischemia remains unclear. It has been hypothesized that hypothermia reduces the reperfusion damage; the additional damage incurred upon the myocardium during reperfusion. Reperfusion results in a massive increase in blood flow, reactive hyperemia, which may contribute to reperfusion damage. We postulated that hypothermia could attenuate the post-ischemic reactive hyperemia.

Methods: Sixteen 25-30 kg pigs, in a closed chest model, were anesthetized and temperature was established in all pigs at 37 degrees C using an intravascular cooling catheter. The 16 pigs were then randomized to hypothermia (34 degrees C) or control (37 degrees C). The left main coronary artery was then catheterized with a PCI guiding catheter. A Doppler flow wire was placed in the mid part of the LAD and a PCI balloon was then positioned proximal to the Doppler wire but distal to the first diagonal branch. The LAD was then occluded for ten minutes in all pigs. Coronary blood flow was measured before, during and after ischemia/reperfusion.

Results: The peak flow seen during post-ischemic reactive hyperemia (during the first minutes of reperfusion) was significantly reduced by 43 % (p < 0.01) in hypothermic pigs compared to controls.

Conclusion: Mild hypothermia significantly reduces post-ischemic hyperemia in a closed chest pig model. The reduction of reactive hyperemia during reperfusion may have an impact on cardiac reperfusion injury.

Show MeSH
Related in: MedlinePlus