A new protective solution for hypothermic storage of free vein grafts in cardiovascular surgery

Hypothermia and rewarming after hypothermic exposure alter venous relaxation

Hypothermia has pathophysiological consequences on endothelial and smooth muscle cell function. This study investigates the impact on venous relaxation of hypothermia and rewarming following hypothermic exposure. In vitro isometric relaxation responses of norepinephrine precontracted rabbit external jugular veins to a panel of endothelium-dependent and -independent agonists were assessed in controls at 37 degrees C, and in an experimental group after cooling to 20 degrees C and after rewarming to 37 degrees C. On cooling, the endothelium-dependent responses to acetylcholine became multiphasic with initial contraction at low concentrations followed by relaxation at higher concentrations, the maximum of which was significantly diminished compared to controls. Incubation with indomethacin did not affect this response. Rewarming re-established a monophasic dose-dependent acetylcholine induced relaxation response but the maximal response was significantly augmented. This augmentation in relaxation on rewarming could be prevented by preincubation with indomethacin. The maximal response to calcium ionophore was reduced at 20 degrees C and augmented upon rewarming to 37 degrees C. All veins relaxed in a dose-dependent manner to the non-endothelium-dependent agonists forskolin and sodium nitroprusside; the maximal responses were significantly reduced at 20 degrees C and returned to normal upon rewarming. This study suggests that short-term exposure of venous tissue to hypothermia impairs the vessel's ability to produce endothelium-dependent relaxation. Rewarming does not re-establish normal endothelium-dependent relaxation but results in an enhanced, partially indomethacin-sensitive, response which appears to be independent of changes in non-endothelium-dependent mediated relaxation.

Influence of perioperative storage solutions on long-term vein graft function and morphology

It has been shown that suboptimal preparation of a vein graft prior to its insertion results in immediate morphologic and functional damage to the endothelial cells but not to the underlying smooth muscle cells. However, little is known about whether such perioperative injury to the vein grafts influences the subsequent development of intimal hyperplasia and smooth muscle cell contractility. This study examines the influence of storage in saline solution or Ringer's lactate on the development of intimal hyperplasia and vasomotor function in experimental vein grafts. Twenty-six New Zealand white rabbits had a carotid vein bypass graft performed after the veins had been immersed (15 minutes) in either heparinized saline solution (Sal; n = 13) or Ringer's lactate (RL; n = 13), and each group was harvested after 28 days for either histologic (n = 8) or functional studies (n = 5; four 5 mm rings/graft). Saline storage of the vein graft resulted in a 38% increase in the thickness of the intimal hyperplasia (113 +/- 2 vs. 83 +/- 2 microns, Sal vs. RL; mean +/- SEM; p < 0.05) without a change in medial thickness (87 +/- 5 vs. 86 +/- 8 microns, Sal vs. RL; p > 0.05). The two sets of vein grafts showed no difference in sensitivity to norepinephrine, serotonin, and bradykinin.(ABSTRACT TRUNCATED AT 250 WORDS)