Cervical Hyperextension Causes Acute Cerebral Congestion in Non-Anesthetized Healthy Adults: An Observational Self-Controlled Design Study.

Background and Objectives: Severe complications associated with cervical hyperextension during general anesthesia have been reported. The question is whether some of the cerebral/spinal ischemic complications could be partially related to the position itself. Cerebral oximetric monitoring, combined with optic nerve sheath diameter and cognitive function in non-anesthetized healthy volunteers, should provide more extensive information about the effects of cervical hyperextension, independent of anesthesia. Materials and Methods: 51 healthy volunteers with no vertebrobasilar abnormalities completed the study and were included in statistical analysis. Primary outcomes were cervical blood flow and cerebral relative hemoglobin change. The secondary outcomes were optic nerve sheath diameter and cognitive function assessment. After baseline Doppler ultrasonography of the cervical vessels, Mini-Mental State Examination, Montreal Cognitive Assessment, and optic nerve sheath diameter measurements at T0, volunteers underwent cervical hyperextension > 30°, with assessments repeated at the first and 30th minutes (T1, T30). Relative total, oxi-, and deoxyhemoglobin changes were assessed every 5 min. Results: Peak systolic velocities in the jugular veins at T1 and T30 were significantly lower than those at baseline (p1 and p2 < 0.001). After hyperextension, deoxyhemoglobin changes significantly increased at T1 and T30 (p1 < 0.001). The optic nerve sheath diameter increased at T30 compared to the baseline (p < 0.001). Cognitive scores improved at T30 (p = 0.044 and p < 0.001, respectively). Conclusions: Cervical hyperextension causes a significant increase in relative total and deoxyhemoglobin changes, which are related to acute cerebral congestion by severely impairing cerebral venous flow. A significant change in optic nerve sheath diameter indirectly indicates increased intracranial pressure.