Urea clearance: a new method to register local changes in blood flow in rat skeletal muscle based on microdialysis.

SUMMARY: Increasing evidence suggests that local blood flow should be monitored during microdialysis (MD) as the recovery of analytes is affected by local blood flow. At present ethanol clearance is the standard technique for this purpose, but it is not functional at very low perfusion velocities. Here, we introduce a technique for MD whereby local tissue blood flow is recorded by the use of urea clearance (changes inflow/outflow concentration), in conjunction with measurements of tissue metabolism (glucose, lactate and puruvate). MD probes were inserted into the gracilis muscle of 15 rats and perfused with a medium containing urea (20 mmol l(-1)). Changes in muscle blood flow were made by addition of noradrenaline (5 microg ml(-1)) to the perfusion medium at two perfusion velocities (0.6 and 0.4 microl min(-1)). The clearance of urea from the perfusion medium was then calculated and examined in relation to the dose of noradrenaline and to the coexisting changes in extracellular metabolites. The results showed reproducible and dose-dependent changes in blood flow that were induced by noradrenaline. These were characterized by dose-dependent changes in the urea clearance as well as blood-flow-specific changes in the MD metabolic markers (reduction in glucose and increase in lactate). The sensitivity for blood flow changes as assessed by urea clearance (MD) was increased at 0.4 compared with the 0.6 microl min(-1) perfusion speed. The results indicate that inclusion of urea to the perfusion medium may be used to monitor changes in skeletal muscle blood flow at low perfusion velocities and in parallel assess metabolic variables with a high recovery (>90%).

Acidosis in muscle tissue distal to vascular contusion despite unchanged global blood flow in rats: an uncoupling of microvascular blood flow and metabolism?

Studies using a contusion trauma model have shown that the femoral artery of the rat remains patent in 85% despite a severe vessel injury. A significant increase in tissue oxygenation (PtO2) has been found despite only a minor effect on blood flow (<20% decrease) on the muscle surface distal to the injury indicating a disturbed relationship between microvascular blood flow and metabolism. The aim of the present study was to further study the interplay between microvascular blood flow and metabolism within the distal muscle using an ethanol clearance technique (blood flow) in conjunction to the determination of an ischemia marker (lactate) by use of microdialysis. Although skeletal muscle blood flow remained unaltered as assessed by ethanol clearance, skeletal muscle lactate levels increased significantly (P<0.001) post-trauma in both legs. The increase was initially higher, faster and the increase over time larger in the trauma leg as compared to the control leg (P<0.001). These findings indicate a systemic effect of the trauma. Further, it suggests a functional impairment of the relationship between microvascular blood flow and/or muscle metabolic processes when the trauma is directed towards the supplying blood vessel. The reason for this anaerobic insult as found in this study compared to the presence of a local increase in PtO2 in the trauma leg as shown in our previous study is suggestive of an microvascular blood flow and tissue metabolism uncoupling.

Severe contusion of the femoral vessels in rats alters tissue oxygenation and microvascular blood flow regulation in the skeletal muscles of the limb.

BACKGROUND: Severe contusion of an artery often presents clinical problems in that it affects flow distal to the injury. However, the effect of a contusion on the microvascular flow regulation in the distal part of the limb is still largely unknown. METHODS: A multipoint microelectrode technique was used to assess both tissue oxygenation (PtO2) and microflow (hydrogen clearance) on the skeletal muscle surface in a standard contusion injury to the femoral vessels in rats. RESULTS: A significant increase in and an altered distribution of (PtO2) as well as a reduction in and altered distribution of microflow on the muscle surface distal to the injury was found in all animals (n = 27) compared with the uninjured control leg. These findings could not be reproduced experimentally by sympathectomy or when the adjacent skeletal muscle alone was injured. CONCLUSION: The results suggest that the changes observed distal to the injury are of vascular origin, possibly as a result of endothelial damage at the site of the contusion.

The effects of a shortened postoperative mobilization programme after flexor tendon repair in zone 2.

The effects of a shortened post-operative mobilization programme following flexor tendon repair in zone 2 in the hand were examined in a prospective, randomized study. 91 digits in 82 patients were included in the study. All injured tendons were repaired within 24 hours and all patients were subjected to the same mobilization programme during the first 6 weeks using a passive flexion-active extension régime. After 6 weeks the patients were randomized into two groups; in group A full activity was allowed after 8 weeks while in group B unrestricted use of the injured hand was not allowed until 10 weeks after the tendon repair. Functional results were compared using the Louisville, Tsuge and Buck-Gramcko assessment systems. Grip-strength was measured 16 weeks after repair, subjective assessment of hand function was recorded on a visual analogue scale, and absence from work was registered. No significant differences were observed between the groups regarding functional results, rupture rates, grip strength or subjective assessment, but absence from work was reduced by 2.1 weeks with the shorter mobilization programme. Using the described régime, full activity can be encouraged 8 weeks after flexor tendon repair in zone 2 of the hand without adverse effects on functional results or increased risk of rupture of the repair.

Microvascular surgery after severe contusion of the femoral artery in rats.

Thirty three rats were subjected to severe contusion of the femoral region by a heavy falling object. The injury was directed towards the palpated femoral vessels in a standard way as described in a previous study. One hour after the injury microvascular surgery was performed on the damaged part of the femoral artery. In 17 animals the artery was transected at the centre of the injured part. The ends were then anastomosed without resection. In the remaining 16 animals the damaged part of the artery was resected and a long arterial graft taken from the opposite, uninjured leg was substituted. Postoperatively the animals were observed for two hours. Arterial patency was evaluated immediately after injury, at the end of operation and after one and two hours. After the animals had been killed, transverse sections of the damaged arteries from 28 of the 33 were examined by light microscopy. Signs of severe contusion was found in 82% of the specimens. The overall number of injured arteries was 97%. The patency rate after transection treated by direct suture was 71%, and after resection and vascular grafting it was 100%.

Improved results in zone 2 flexor tendon injuries with a modified technique of immediate controlled mobilization.

The results following primary and delayed primary repair in zone 2 flexor tendon injuries were evaluated in 85 fingers of 79 patients using immediate controlled mobilization post-operatively. In 31 patients a conventional Kleinert technique was used. In the remaining 48 patients a modified technique was used with rubber band traction to all fingers instead of only to the injured one. Also a shorter dorsal splint was used in order to secure extension of the PIP and DIP joints. The results were improved and the time of treatment was reduced.

The effect of severe contusion on the vessels of the femoral region. An experimental morphological study.

Forty-one rats were subjected to a single blow in the femoral region from a heavy falling object. The contusion was directed towards the palpated femoral vessels in a standard manner. Transverse sections of the femoral artery and vein with branches, including adjacent muscle, were taken at 30 min, 24 hours, 2 weeks and 1 and 3 months after the injury and evaluated by light microscopy. The injuries to the femoral vessels and their branches at 30 min and 24 hours varied from partial destruction of the internal elastic lamina only to crush injury of the media together with thrombosis. Bleeding was always present. In the most severely injured arteries the vessel wall had ruptured. The findings at 2 weeks and 1 and 3 months were more discrete. The femoral vessels had remained patent, sometimes with permanent damage to the internal elastic lamina and rearranged architecture of the elastic tissue in the media. In a few cases recanalized thrombi were seen in arterial branches. Fibrosis of the femoral muscle was found at the level of trauma. Despite a single serious blow to the femoral region, however, there was no permanent major injury to the femoral artery or vein.

Pain relief after free flap reconstruction in adriamycin necrosis on the dorsum of the hand. A case report.

A free flap transfer in a case of Adriamycin necrosis on the dorsum of the hand is reported. The advantages of this method of reconstruction are discussed.