Major Vascular Anatomy of the Orbit

The ophthalmic artery is an unusual source of orbital hemorrhage unless the optic nerve is transected as is performed in enucleation or orbital exenteration surgery. In these settings, identification of the optic nerve stump can be facilitated through use of malleable (ribbon) retractors, and hemostasis can be achieved with bipolar cautery of the artery.

Laceration of the ethmoidal arteries can lead to serious orbital hemorrhages during orbital or sinus surgery. During a planned orbital approach to the medial orbital wall, it is both safe and helpful to ligate the anterior ethmoidal artery via a subperiosteal approach before further posterior dissection. The location of this vessel is consistently ∼24 mm from the anterior lacrimal crest at the frontoethmoidal suture line. Although this vessel is not always present, knowledge that a middle ethmoidal artery may be encountered can prevent further unwanted hemorrhage. The posterior ethmoidal artery lies in close proximity to the optic canal and optic nerve. Therefore, efforts to ligate this vessel may lead to unwanted damage to the optic nerve and should be attempted only with great care. A useful mnemonic to aid recall of these important anatomic relationships is 24 to 12 to 6: the anterior ethmoidal being 24 mm from the anterior lacrimal crest, posterior ethmoidal located 12 mm posterior to this, and the optic canal positioned 6 mm behind. However, the anatomy, number, and location of these vessels relative to bony landmarks are variable, and these measurements should only be considered rough guidelines.

These vessels are readily encountered while reflecting the periorbita (periosteum inside the orbit) off of the lateral orbital wall and floor. Pre-emptive ligation with bipolar cautery can save time during dissection because shearing these vessels often results in retraction of the visible stump within the bone. If this occurs, monopolar cautery or bone wax can restore hemostasis. However, monopolar cautery should be used with caution near the orbital roof because this can damage the dura and result in a cerebrospinal fluid leak even in the absence of bone disruption.

Ligation of the superior ophthalmic vein can trigger significant ocular congestion, elevated intraocular pressure, and ultimately, compromise of visual function. Compromise of the inferior ophthalmic vein, however, does not result in significant morbidity. This vein is often transected during manipulation of structures passing through the inferior orbital fissure.

Preoperative Assessment

Optimization of preoperative factors can significantly lessen the risk of orbital hemorrhage. Although it is ideal to stop all anticoagulants before orbital surgery, surgery can still be pursued with concomitant use albeit with greater risk. Aspirin and warfarin discontinuation should only be pursued under the direction of the primary care practitioner or cardiologist because the risk of stopping (eg, cardiac and cerebrovascular) may outweigh the perceived benefit of lessening the risk of hemorrhage. Surgical planning for patients on newer anticoagulants, such as dabigatran, rivaroxaban, and apibaxan, presents significant challenges because these agents are neither easily assayed nor reversed. Antidotes are neither US Food and Drug Administration approved nor fully effective at this time. The most important predictor of orbital hemorrhage is a patient history of a prior bleeding abnormality during surgery.

The degree of orbital hyperemia can often be characterized on imaging performed with contrast. Consultation with interventional neuroradiology can be helpful in the setting of highly vascular orbital lesions to consider interruption of inflow and outflow pathways before excision. Precise intraluminal delivery of thrombogenic agents can improve the safety profile before excision of orbital vascular tumors.

Although a rare occurrence, the risk of orbital hemorrhage should be outlined in the informed consent process for any eyelid, orbital, and sinus surgery because of the potential for devastating consequences. Patients should be instructed to decrease exertional and provocative activities in the 2 weeks after these surgeries because they increase orbital vascular congestion and can predispose to the development of postoperative orbital hemorrhage. These activities include strenuous exercise, sexual activity, bending the head below chest level, squeezing of facial muscles, lifting greater than 10 pounds, and other Valsalva maneuvers.

Overview of Endoscopic Surgery of the Orbit

Endoscopic surgery of the orbit provides optimal magnification and illumination during orbital surgery to all those in attendance and is ideal for education, training, and involvement of the entire operative team in the surgery. Traditional open approaches often only allow the operating surgeon adequate views, albeit at lower magnification. The use of modern navigation technologies as an adjunct to endoscopy can increase the safety profile of surgery through confirmation of anatomic landmarks with radiologic images. The small expense of navigation devices is greatly outweighed by their benefit.

Causes of Orbital Hemorrhage

Disruption of smaller blood vessels that supply orbital tissues results in slower development of orbital hemorrhages. These bleeds may not present until after surgery but can still have devastating consequences secondary to development of compartment syndrome and resultant tissue ischemia.

Clinical Signs of Orbital Hemorrhage

Periodic assessment for these signs in orbital and sinus surgery can provide useful information and help to rule out the presence of an orbital hemorrhage. Gentle ballottement of the globe using the tips of the index fingers can help to determine if the orbit is tense. For novice orbital surgeons, performing this maneuver at the start of surgery before incision will provide a baseline for intraoperative assessment of orbital and globe pressure. Precise measurement of intraocular pressure is provided by an automated tonometer, such as a Tono-Pen (Reichert Technologies, Buffalo, NY, USA), which are commonly used by ophthalmic surgeons. Intraocular pressures less than 21 mm Hg are considered normal, and transient pressure readings less than 30 mm Hg rarely cause permanent vision loss. The risk of permanent vision loss increases proportionately as the intraocular pressure increases.

Abnormalities in the size and shape of the pupil may be a sign of excessive pressure on the globe or retrobulbar structures, including the ciliary ganglion. Periodic assessment of pupil size and shape can help detect this and in this way serves as an adjunct measure of intraorbital pressure. Local infiltration of epinephrine-containing local anesthetics can lead to papillary dilation and may interfere with this assessment. Dynamic changes in pupil size noted intraoperatively usually respond to removal of surgical instruments from the orbit and a reduction in intraorbital pressure. A fixed, dilated pupil may be a sign of irreversible damage to the optic nerve and or ciliary ganglion.

Intraoperative Techniques for Hemostasis

Identification of the source of hemorrhage is often facilitated through the use of malleable retractors and neurosurgical cottonoids, which provide a barrier to orbital fat from entering the surgical field. Allowing saline to pool in the orbit is a useful technique to determine if hemostasis has been achieved and to detect the point source, which may be seen streaming from within the fluid compartment.

Anesthesia providers can reduce the occurrence and rate of hemorrhage through the use of head-up positioning (reverse Trendelenburg) and lowering of the mean arterial pressure. Although these factors may be overlooked in the search for hemorrhage, they can often be extremely helpful. Deep extubation and antiemetic agents can help reduce coughing and vomiting, which can both lead to increased intracranial pressure. Steroids and serotonin antagonists are particularly effective for postoperative nausea.

Hemostatic Techniques

Monopolar (Bovie) cautery is broadly effective but results in greater tissue disruption secondary to the generation of thermal damage to the radial field surrounding the tip. Bipolar cautery lessens surrounding tissue disruption but requires greater access for careful administration secondary to the size of the forceps. Bayonet forceps are very useful within the deep orbit.

Bone wax is extremely effective in sealing hemorrhage from bone-perforating vessels. Effort should be made to remove excess material because it may cause unwanted inflammation.

Administration of vasoconstrictors via topical and injectable routes helps to reduce vascular congestion and intraoperative bleeding. They can be administered after bleeding is discovered, but will take several minutes before they reach their maximal effect.

Chemical coagulants and matrix coagulators are particularly helpful in the setting of brisk hemorrhage when a point source is unable to be identified. Hydrogen peroxide is useful for diffuse oozing and leads to vasoconstriction and thrombus formation through aggregation of neutrophils and platelets. Thrombin can be introduced via infused cottonoids or on gelfoam-soaked wedges. Floseal is distributed as a highly viscous paste that easily adheres to different surfaces. The authors have had success with a premade mixture of 5000 units thrombin, 8 mL saline, and surgifoam powder as an alternative to Floseal at reduced cost. Surgicel and Avitene can provide a matrix for clot formation but may add unnecessary volume to the orbit. Administration of hemostatic materials into the orbit should be limited to that which is required for hemostasis because residual material may lead to granuloma formation.

Approaches to the Orbit for Rapid Control of Ethmoidal Hemorrhage

Transorbital endoscopic techniques can be extremely useful for the treatment of ongoing orbital hemorrhage. If the hemorrhage is due to sinus surgery, a transorbital approach transfers the procedure to a dry field, where the anterior, middle, and posterior ethmoidal arteries can be easily visualized and ligated. The vector of this approach, coplanar with the vessels, is highly favorable and provides excellent freedom of instrument motion. The ligation can be performed with small vascular clips or bipolar cauterization. When the posterior ethmoidal vessels are involved, visualization of the optic nerve is advisable before ligating the vessels, directly or with surgical navigation.

CT performed without contrast can help to localize the site of blood deposition. Hemorrhages are localized to the intraconal, extraconal, or subperiosteal compartments of the orbit. Intraconal hemorrhages are often focal, but drainage is not advised because of the proximity of critical ocular structures, including extraocular muscles and nerves, ciliary body, and the optic nerve. Extraconal hemorrhages are usually more diffuse and difficult to drain. Subperiosteal hemorrhages often collect in a well-defined compartment and are amenable to drainage with an increased safety profile. The term retrobulbar hemorrhage encompasses all the entities described above ( Fig. 1 ).

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Hemostatic Materials and Devices
2. Treatment of Hereditary Hemorrhagic Telangiectasia–Related Epistaxis
3. Hemostasis in Otologic and Neurotologic Surgery
4. Management of Carotid Blowout from Radiation Necrosis

Stay updated, free articles. Join our Telegram channel

Join