P002: SITTING POSITION CRANIOTOMY IN PATIENT WITH PATENT FORAMEN OVALE
Nicole Fares, MD; Caroline Nikolaidis, MD; Wakim Giselle, MD
University of Miami/Jackson Memorial
Background: The sitting position is frequently utilized for shoulder surgeries, posterior cervical spine surgeries, and posterior fossa craniotomies. While the sitting position provides numerous surgical benefits, it has been associated with complications including venous air embolism (VAE), potentially leading to obstructive effects on pulmonary circulation as well as systemic embolization. An intracardiac right-to-left shunt as with patent foramen ovale (PFO) is considered an absolute contraindication to sitting position craniotomy due to the additional risk for a paradoxical air embolism in which the air embolism enters the arterial vasculature. This presentation describes the perioperative management of an otherwise healthy 27 year old female with a symptomatic pineal gland mass causing hyperprolactinemia and headaches who was discovered to have a PFO preoperatively, and proceeded to undergo posterior fossa craniotomy in the sitting position.
Methods: Prior to surgery, the patient underwent transthoracic echocardiogram (TTE) for routine preoperative assessment, which revealed a small interatrial shunt upon agitated injection of saline. This finding as well as the associated risks of sitting position was discussed with the neurosurgery team, who maintained that the case must proceed in the sitting position. Risks were also discussed with the patient, who also agreed to surgery. Thus, the case proceeded, and the patient was induced under general anesthesia with a post induction arterial line placed. Transesophageal echocardiogram (TEE) was performed by the cardiac anesthesiology team, which confirmed the presence of a PFO, and was used to monitor for the presence of VAE for the duration of surgery.
Results: VAE was not detected on TEE throughout the duration of surgery, and metrics including end tidal CO2 and ECG showed no abnormalities at any point. No neurologic deficits were noted on post-operative exams.
Discussion: Although the risk for a significant VAE on a patient in the semi-seated position is feared, the presence of a PFO provides an additional potential complication of a paradoxical air embolism which enters systemic vasculature. Systematic reviews have shown the incidence of paradoxical air embolisms to be 0-14% even at the higher rate venous air embolisms occur (35-45%) in patients with a patent foramen ovale, therefore measures should be taken to minimize these risks, detect a VAE or PAE early, and provide swift treatment. Options for management of a patient with a known PFO scheduled for a non-emergent surgery requiring sitting position include percutaneous PFO closure 2-4 weeks prior to surgery, which is generally low risk and well tolerated. If unable to close the PFO, a modified sitting position is recommended where the patient’s head is minimally elevated. Transesophageal echocardiography is the most sensitive modality for early detection of a venous air embolism, followed by a precordial doppler which is less invasive and then pulmonary arterial catheter placement. Volume loading with a colloid has also been demonstrated to reduce VAE incidence due to reduction in negative venous pressure at the wound level. Neck compression, although shown to be effective at reducing VAE incidence, has associated risks including brain swelling, vagal response, and arterial occlusion.