CSF Drainage Spinal Cord Protection — FRCA Final MCQ

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HardCardiothoracic AnaesthesiaCSF Drainage Spinal Cord ProtectionFRCA Final

A 60-year-old man undergoes open thoracoabdominal aortic aneurysm repair with prophylactic cerebrospinal fluid drainage. During aortic cross-clamping, mean arterial pressure is maintained at 80 mmHg. Spinal cord perfusion pressure is approximated by mean arterial pressure minus CSF pressure, and the protocol aims to maintain it at or above 70 mmHg. What is the highest CSF-pressure target that should be used as the upper limit?

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Correct answer: E — 10 mmHg

The correct answer is E: 10 mmHg. Spinal cord perfusion pressure is approximated as mean arterial pressure minus CSF pressure. With a MAP of 80 mmHg and a required SCPP of at least 70 mmHg, CSF pressure must not exceed 10 mmHg. This also corresponds to the commonly used prophylactic target during open descending thoracic and thoracoabdominal aortic repair. A target of 5 mmHg is unnecessarily low for routine prophylaxis and may encourage excessive drainage, increasing the risk of headache, intracranial hypotension or haemorrhage. Targets of 15–25 mmHg would produce calculated SCPP values of only 65–55 mmHg and therefore fail the stated perfusion goal. CSF drainage remains one component of multimodal protection alongside adequate arterial pressure, distal perfusion and surgical strategies.

Reference: Bilal H, O'Neill B, Mahmood S, Waterworth P. Is cerebrospinal fluid drainage of benefit to neuroprotection in patients undergoing surgery on the descending thoracic aorta or thoracoabdominal aorta? Interactive Cardiovascular and Thoracic Surgery. 2012;15:702-708. https://pubmed.ncbi.nlm.nih.gov/34318127/