Enhancement of blood flow in experimental microvascular free flaps

Role of priming stresses and Hsp70 in protection from ischemia-reperfusion injury in cardiac and skeletal muscle

Ischemia-reperfusion injury limits the survival of muscle involved in tissue trauma or transfers during microsurgical reconstruction. Priming stresses such as ischemic preconditioning or mild hyperthermia have frequently been associated with improved survival of ischemic-reperfused cardiac muscle, such protection coinciding with induction of the stress-related heat shock protein 70 (Hsp70). Little is known about the response of skeletal muscle to priming stresses. This review summarizes the current knowledge on the use of priming stresses as protective strategies against the consequences of ischemia-reperfusion in cardiac and skeletal muscle and the potential role of Hsp70.

Effect of a thromboxane synthetase inhibitor UK-38,485 on the tolerance of skin flaps of primary ischaemia

The harmful effects of ischaemia or skin flaps were modified using the thromboxane synthetase inhibitor UK-38,485. The epigastric island flaps of Sprague-Dawley rats (n = 288) were subjected to 10, 12 or 14 h of total pedicle occlusion, or 3, 5 or 7 h of venous occlusion of the sole vascular pedicle. Within each time period, rats received intravenous doses of either physiological saline (controls) or UK-38,485 at the beginning or end of the ischaemic episode. Flaps treated with UK-38,485 overall had a higher survival rate than control ischaemic flaps (P less than 0.001). This applied both to total (arterial) ischaemia (P less than 0.001) and partial (venous) ischaemia (P less than 0.01). There was no significant difference between treatment given at the beginning or at the end of the ischaemic episode. These results may be explained by reduced platelet aggregation and thrombosis in the microvasculature due to the lower thromboxane/prostacyclin ratios for treated flaps. The possible inter-relationship of the prostanoids with free radical mechanisms in the no-reflow phenomenon is also discussed.

Laser-Doppler versus fluorometry in the postoperative assessment of a cutaneous free flap

To find the optimal means for monitoring the vascularity of a cutaneous free flap in the postoperative period, we have experimentally compared laser-Doppler velocimetry and fluorometry. Using the rat groin model, five groups were evaluated: 1. flap isolation without division of the pedicle vessels (island flap); 2) flap isolation, division, and repair of the pedicle artery and vein (free flap); 3) flap isolation, with ligation of the pedicle artery immediately or 1 hour later; 4) flap isolation, with ligation of the pedicle vein immediately or 1 hour later; 5) flap isolation, with ligation of the pedicle artery and vein immediately or 1 hour later. The laser-Doppler processes the signal by combination of the root mean square and differential amplification. The fluoroscan gives an index in relation to the fluorescence of a control area. The results obtained with both methods correlated well with findings in clinical situations. However, the laser-Doppler readings were more rapid and sensitive than those with fluorometry. We suggest that laser-Doppler velocimetry is a superior means of monitoring the vascular status of a free tissue transfer or digital replant.