An aneurysm is a local bulging of a blood vessel that carries a risk of rupture. Surgery for an aortic aneurysm requires clamping the aorta, the biggest artery in the body. This reduces the supply of blood and oxygen to the spinal cord (ischaemia) and tissue damage can lead to the partial or incomplete paralysis of the lower limbs (paresis) and paraplegia (paralysis of the legs and lower part of the body). These deficits are frequently irreversible. The cerebrospinal fluid (CSF) pressure increases during clamping further decreasing the perfusion pressure of the spinal cord. As more of the blood supply to the spinal cord is interrupted, the likelihood of paraplegia is increased. Various treatments are used to reduce the ischaemic insult to the spinal cord including temporary blood shunts (such as distal atriofemoral bypass and re-connection of intercostal and lumbar vessels), pharmaceutical interventions (to protect the heart and cerebral blood vessels), epidural cooling and CSF drainage. Draining CSF from the lumbar region may lessen the CSF pressure, improve blood flow to the spinal cord and reduce the risk of ischaemic spinal cord injury.
The available evidence does not fully establish CSF drainage as a method of protection. The review authors made a thorough search of the medical literature and identified three randomised trials involving a total of 287 participants operated on for high-risk thoracoabdominal aortic aneurysms. All of the studies used CSF drainage in addition to other measures of spinal cord protection. In the first trial of 98 patients, neurological deficits in the lower extremities occurred in about one third of patients with or without drainage. The deficit was observed within 24 hours of the operation in 21 (68%), and from three to 22 days in 10 (32%). The second trial of 33 patients reported that a combination of CSF drainage and papaverine in the region of the spinal cord (intrathecally) reduced the rate of postoperative neurological deficit compared to controls. In the third trial involving 145 patients, drainage was begun during the operation and continued for 48 hours after surgery. Paraplegia or paraparesis occurred less with CSF drainage (2.7% of patients with drainage versus 12.2% in the control group).