Lumbar Spinal Drain
One of the more significant complications of thoracoabdominal aortic surgery is ischemic spinal cord injury (SCI). The result of this can be paralysis and lack of sensation to both lower extremities. This can present immediately after surgery (acute) or be delayed for several days (postponed). Placing a lumbar cerebrospinal fluid (CSF) drain can reduce the risk of SCI by reducing the intraspinal pressure (or ICP) and allowing more perfusion to the spinal cord. Spinal cord perfusion is determined by mean arterial pressure minus intracranial pressure (SCP = MAP - ICP). ICP can be replaced with central venous pressure (CVP) in this equation, depending on which is higher.
The risk of SCI post-TAAA surgery increases with advance age, emergent cases, patients with extensive aortic disease (including previous aortic intervention), and patients with comorbidities such as diabetes and chronic kidney disease. TAAA repair can be performed open or endovascularly. The rate of SCI appears to be about 4% low with endovascular vs. open techniques.
The blood supply to the spinal cord is comprised of a single anterior spinal artery and two posterior spinal arteries. There is also a network of segmental arteries that provide collateral flow. The artery of Adamkiewicz is a major contributor to the anterior spinal artery in the thoracic region, as it arises from T9-12 vertebral level in most people.
During open TAAA repairs, clamping the aorta will result in disruption of collateral blood supply to the spinal cord and increases blood pressure in the head and neck. This causes increased CSF production and an increase in ICP and CVP. Collectively this can reduce spinal cord perfusion. During endovascular repair, clamping is avoided but you can have occlusion of segmental branches of the aorta (ie. Intercostal arteries) by the endograft. Delayed presentations are more common with endovascular approach and can present 48 hours post-op.
CSF drainage was first proposed in 1988 to prevent SCI and has continued to be a favorable approach for TAAA repairs. Ideally the spinal cord perfusion pressure is maintained above 70 mmHg. This means maintaining MAPs around 80-100 mmHg and CSF pressure below 10 mmHg. This may require draining 5-10cc’s every 30 to 60 minutes. Normally, the rate of drainage should not exceed 15 ml/hr. The complication of draining too much too quickly is potential herniating of the brain.
