It had been reported the cervical spondylotic myelopathy may lead to the development of hypertension. Decompression surgeries ameliorated neurological symptoms as well as the blood pressure. The cause may be the abnormality of autonomic dysfunction developed after myelopathy. However, the evidence was weak. We have noticed a tendency of hypotension during anesthesia in patients undergroing cervical spine surgeries, especially in surgeries of long levels and hypertensive patients. Thus we postulate the autonomic activity is abnormal in patients with cervical myelopathy. Sympathetic hyperactivity developed in order to maintain adequate perfusion to the cervical cord. When patients are under anesthesia, the sympathetic tone is suppressed, thus leading to severe hypotension that require the treatment of inotropic treatment. Heart rate variability (HRV) is a good index of autonomic activity. Thus we plan to Therefore we will measure the HRV (analysis of ECG) and baroreflex activity (analysis of arterial line during the anesthesia) in patients undergoing cervical spine surgeries for decompression of cord compression perioperatively. The primary end-point is the comparison of severity of cord compression between normotensive and hypertensive patients with cervical myelopathy. The secondary end-point is to compare blood pressure and HRV pre- and postoperatively. The third end-point is to elucidate the causative factors for severe hypotension during anesthesia.
