Anaesthetic requirements and stress hormone responses in acute cord-injured patients undergoing surgery of the injured spine

BACKGROUND AND OBJECTIVE Neuraxial anaesthesia has been shown to produce a sedative and anaesthetic-sparing effect. The purpose of the present study was to determine the effects of acute spinal cord injury on sevoflurane requirement and stress hormone responses during spinal surgery at the level of the injury. METHODS Thirty-five patients with traumatic complete spinal cord injury undergoing spinal surgery at the level of the injury were studied. They were grouped into quadriplegics (above C7, n = 20) and paraplegics (below T1, n = 15) according to the level of injury. Patients (n = 35) with spine trauma without neurological impairment undergoing spinal surgery at the respective level served as controls. The bispectral index score was maintained at 40-50 throughout the surgery. Measurements included end-tidal sevoflurane concentrations, mean arterial pressure, heart rate, and plasma concentrations of catecholamines and arginine vasopressin. RESULTS During the surgery, the mean arterial pressure was significantly lower in both quadriplegics and paraplegics (P < 0.05). The heart rate did not differ significantly in the quadriplegics, but was higher in the paraplegics, compared with their controls. However, end-tidal sevoflurane concentrations and bispectral index score were comparable with controls in both quadriplegics and paraplegics. Throughout the study, the plasma arginine vasopressin concentrations were not altered, although norepinephrine and epinephrine concentrations were lower in the quadriplegics. There were no significant differences in stress hormones between the groups having thoraco-lumbar surgery. CONCLUSION Spinal cord injury neither alters the anaesthetic requirement regardless of the level of injury during spinal surgery at the level of the injury, nor enhances arginine vasopressin release. However, it blunts catecholamine responses in quadriplegics.