Bone Embolism During Neurosurgery in Sitting Position

Carbon dioxide field flooding reduces the hemodynamic effects of venous air embolism occurring in the sitting position

PURPOSE

Although the utility of the sitting position is undisputed for biomechanical and ergonomic reasons, it has been debated in recent years for its risks, particularly venous air embolism (VAE). In order to reduce the hemodynamic effect of VAE, we changed the composition of the surgical field air partially replacing nitrogen with carbon dioxide (CO2) that better dissolves in human tissues.

METHODS

First, we tested our method on a test dummy in the sitting position. Infrared CO2 sensors were placed close to the wound opening and on the facial mask of the surgeon. An oxygen sensor was connected to a computer for data recording (ALTAIR(®), MSA Safety). This model showed that 10 L/min CO2 flow provides efficient air displacement, maintaining safety for the surgeon. We reproduced the above-described surgical field environment in ten consecutive cases of posterior fossa surgery performed in the sitting position. A homogeneous group of ten patients operated in the sitting position with standard setting environment was used for control. We intraoperatively monitored VAE with trans-esophageal echocardiography (TEE), end-tidal CO2 (ETCO2), CO2 arterial pressure (PaCO2), and hemodynamic changes.

RESULTS

Although the percentage of VAE was 70% in both groups, hemodynamic effects occurred in 10% of cases in the study group and in 40% of cases in the control group.

CONCLUSIONS

Our preliminary study shows that a CO2-enriched sitting position surgical microenvironment significantly reduces the hemodynamic effects of VAE, more likely because arterial CO2 emboli are more soluble and consequently much better tolerated than air emboli.

Subretinal Bone Formation in a Patient with Giant Cell Tumor of the Sphenoid

BACKGROUND/AIMS

To report a case of subretinal bone formation after the treatment with denosumab for a giant cell tumor of the sphenoid, which had recurred after surgical resection.

METHODS

The clinical history and fundus findings including imaging, histologic and immunohistochemical features of the primary tumor and subretinal lesion were reviewed.

RESULTS

A 14-year-old boy was evaluated for a suprasellar mass. Resection of the lesion showed giant cell tumor of bone (GCT). An MRI study at the 1-month follow-up appointment showed tumor progression, and denosumab was initiated. Two months after the initial presentation, the patient developed a worsening scotoma of the right eye. Dilated fundus examination showed a yellow-tan-colored subretinal mass temporal to the fovea. The subretinal lesion was removed and showed lamellar bone with associated fibrocellular tissue.

CONCLUSION

Denosumab therapy for GCT of the sphenoid may be associated with subretinal bone formation.