Wound hematoma after anterior cervical spine surgery: in vitro study of the pathophysiology of airway obstruction.

Airway obstruction by wound hematoma is a serious adverse event associated with anterior cervical spine surgery. Although intrinsic airway edema is the most plausible pathophysiologic mechanism of obstruction, we hypothesized that extrinsic compression of the trachea by a hematoma can result in airway occlusion at an angle to the sagittal plane. A silicone indenter and a servohydraulic test frame were used to apply pressure to the ventral neck of 7 human cadaveric specimens. Increasing pressure was applied in the anteroposterior (AP) and oblique planes until the trachea collapsed, as visualized with fluoroscopy. A paired t test was used to determine any statistically significant differences in maximum pressure or indenter displacement at tracheal occlusion between the 2 test modes. Mean (SD) pressure required to cause complete tracheal collapse was 227.9 (54.8) mm Hg in the AP test mode and 135.6 (73.4) mm Hg in the oblique test mode. The difference was statistically significant (P = .004). Indenter displacement was significantly higher in the AP mode than in the oblique mode (P = .031). The trachea can collapse from external force within a physiologic pressure range when pressure is applied in an oblique orientation. The mass effect of a wound hematoma appears to be a viable mechanism of airway occlusion.