Explain what is Aortic Arch Aneurysm ?

Aortic Arch Aneurysm :  Hypothermic circulatory arrest and retrograde cerebral perfusion is the most commonly used technique for arch aneurysm. Femoral artery cannulation is used for arterial return. Separate SVC and IVC cannulation is done for venous return. While cooling on cardio pulmonary bypass, a vent'catheter is introduced through the right superior pulmonary vein. Snares are passed around superior and inferior vena cavae. After clamping the aorta, antegrade cardioplegia is given through the aortic root. While further cooling is being done, methyl prednisolone and thiopental are administered to enhance the neuroprotective effect of deep hypothermia. Mannitol and frusemide are infused for renal protection. Head is packed with ice bags and continuous EEG monitoiing is done. When nasopharyngeal temperature reaches 12-14°C and rectal temperature is 15°C to 18°C and EEG becomes isoelectric circulatory arrest can be performed. The pump is stopped and aortic clamp is removed. Retrograde cerebral perfusion through 'the superior vena caval cannula, is done from the pump at a lower pressure at a rate of 300 to 500 ml/mt, without raising jugular venous pressure above 30 to 35 mm of Hg. The arch aneurysm is opened and as retrograde cerebral perfusion is being done de-oxygenated blood will come out of the carotid arteries. This helps in reducing chances of air embolism to the cerebral arteries. Distal anastomosis of the descending thoracic aorta to an albuminimpregnated graft is done with continuous sutures. The anastomosis is usually reinforced with a narrow strip of PTFE or Dacron graft. The origins of all the three arch vessels cut out together with margins of aorta are then anastomosed to a suitably sized oval opening made on top of the tube graft. Then slowly arterial pump is re-started and blood is allowed to fill the descending aorta and arch. All air is expelled and the proximal end of the tube graft is clamped and perfusion through brachio - cephalic arteries are re-established. Retrograde cerebral perfusion is discontinued and normal cardio pulmonary perfusion and rewarming started. Proximal anastomosis with the ascending aorta is then completed and complete de-airing of heart and ascending aorta done before heart is allowed to eject and establish effective circulation.