Intraluminal shunt for the thoracic aorta: blood flow and function in chronic studies

Histological Findings After Aortic Cross-Clamping in Preclinical Animal Models

Spinal cord ischemic injury and paralysis are devastating complications after open surgical repair of thoracoabdominal aortic aneurysms. Preclinical models have been developed to simulate the clinical paradigm to better understand the neuropathophysiology and develop therapeutic treatment. Neuropathological findings in the preclinical models have not been comprehensively examined before. This systematic review studies the past 40 years of the histological findings after open surgical repair in preclinical models. Our main finding is that damage is predominantly in the grey matter of the spinal cord, although white matter damage in the spinal cord is also reported. Future research needs to examine the neuropathological findings in preclinical models after endovascular repair, a newer type of surgical repair used to treat aortic aneurysms.

An Intra-Aortic Shunt Prevents Paralysis During Aortic Surgery in Sheep

INTRODUCTION

Sheep are recommended by the United States Food and Drug Administration as a model for testing cardiovascular tissue, but are particularly prone to spinal cord ischemia and subsequent paralysis during aortic cross-clamping.

METHODS

A shunt consisting of a 9 cm long phosphorylcholine coated 1/4 in. (i.d.) polyvinylchloride tube was inserted through the aortotomy into the aorta to provide blood flow across the operative site. Blood pressure and flow in the distal aorta were measured continuously with an indwelling femoral artery catheter and an ultrasonic aortic flow probe. The hemodynamic effects were measured in seven 45 to 55 kg Suffolk sheep. This shunt was then used to implant decellularized pulmonary artery patches into 25 animals.

RESULTS

Occlusion of the aorta reduced the distal mean aortic pressure from 86.4 +/- 4.6 mmHg to 1.79 +/- 0.4 mmHg (P < 0.001) and opening the intra-aortic shunt restored the distal mean aortic pressure to 67.9 +/- 7.3 mmHg (P = 0.053). Blood flow in the distal aorta was 2.35 +/- 0.37 L/min at baseline and was reduced to -0.01 +/- 0.01 L/min (P < 0.001) with the aorta cross-clamped and returned to 2.49 +/- 0.36 L/min (P = 0.945) when the shunt was opened. Use of this shunt prevented hind leg paralysis in all 24 animals surviving the procedure.

CONCLUSIONS

A simple intra-aortic shunt was effective in restoring blood pressure and flow in the aorta distal to the operative site and prevented hind leg paralysis associated with aortic clamping.

Neuroprotective effects of FK-506, l-carnitine and azathioprine on spinal cord ischemia-reperfusion injury

OBJECTIVE

In our experimental study, we aimed to test the effect of FK506, azathioprine and L-carnitine on protection of spinal cord injury due to ischemia-reperfusion.

METHODS

Twenty-seven Sprague-Dawley male rats were randomly divided into five groups. They were subjected to spinal cord ischemia by clamping the abdominal aorta for 45 min. Thirty minutes before the aortic clamping, group I received 0.5 mg/kg FK506, group II received 100 mg/kg L-carnitine, group III received 4 mg/kg azathioprine, the fourth group was the control group and received only normal saline injection intravenously and the last group was the sham group. Neurological status was scored by using the Tarlov scoring system. Sections of the lumbar cord were harvested for histopathological grades (1-4), having regard to percentage of the apoptotic cells.

RESULTS

Hind-limb motor function had recovered normally 48 h after the operation in all rats which received FK506, azathioprine and L-carnitine prophylactically. In contrast, all rats in the control group had deteriorated to paraplegia by 48 h after the operation (P<0.05). Histopathologic sections in the involved spinal cord segment showed that a greater number of motor neuron cells were preserved and there were less apoptotic cells in the rats that received FK506, azathioprine and L-carnitine than those in control group.

CONCLUSIONS

These results suggest that prophylactic use of FK506, azathioprine and L-carnitine protects motor neuron cells from ischemic spinal cord injury.