Patients who are at high risk of carotid artery injury during surgery, should be identified pre-operatively based on multiple criteria incorporating prior treatment history and tumor characteristics (Table 3). These include prior radiation to the skull base or brain, invasive sellar and parasellar tumors, tumor histology (meningioma, fibrous adenoma, chordoma, chondrosarcoma, etc…), history of previous skull base surgery , tortuosity and complexity of parasellar carotid artery anatomy and close distance between the two ICA , dehiscent bone covering the parasellar carotid artery, protruded and bulged carotid artery into the sphenoid air cell, displacement of carotid artery by tumor and, adherence of tumor to the artery wall and tumor with intimate contact to the artery wall and degree of adherence/encasement, bony anatomy of the sphenoid sinus and bony septations within the sinus reaching the carotid artery bony covering, vascular anomalies of the parasellar carotid artery prior to surgery (aberrant branch off the medial carotid wall , aneurysm or pseudoaneurysm of carotid artery , ectasia , intimal dissection), previous trauma to the skull base , prior history of dopamine agonist therapy (e.g. cabergoline or bromocriptine) pre-operative plan for extended exposure.
Once a tumor has been considered potentially high-risk, proper measures must be employed to cope with the situation both pre-operatively and intra-operatively on a step-by-step checklist. The carotid artery checklist is divided into two components – pre-injury checklist and injury checklist (Figure 1). The pre-injury checklist prepares the operating room staff to anticipate resuscitation efforts, such as establishing large bore venous access, readying blood available for transfusion, and alerting the neuro-interventional radiology team.3 6 The carotid injury timeout took on average less than five minutes to complete, in addition to the standard timeout and did not significantly impact the overall length of surgery.
Adjuncts in surgery are also necessary including neuromonitoring (somatosensory evoked potentials and electroencephalography). Endonasal aneurysm clips are prepared alongside additional hemostatic material: aneurysm clips and endonasal applier, nasal packing equipment (Merocel packs), Muslin gauze, Muscle patch (muscle crusher from ENT/plastics)[9]. Proper anesthesia preparations should also be checked. This includes: arterial catheter for continuous BP monitoring, vasopressors, two large bore IVs (or central line) available for fluid resuscitation and transfusion and if needed providing a safe central venous access before surgery, Heparin 5,000 units (available if needed), Adenosine 6mg or 12mg (available if needed), Burst suppression agents such as Pentobarbital, Etomidate, or Propofol (available if needed), Neuromonitoring prepared to assess EEG. (Table 4)
In the case of a suspected carotid artery injury, the operating room staff should be prepared to follow necessary protocol. Once the injury is controlled and the bleeding has stopped, muscle graft is harvested, and the Neuro-interventional team is contacted[9]. Muslin gauze should be prepared and ready to use as needed[9]. While surgeons are working in the surgical field, anesthesiologists should start increasing blood pressure (SBP>120mmHg) if the carotid is compressed or clamped to ensure adequate cerebral blood flow is maintained. In addition, anesthesiologists should be prepared to transfuse PRBCs, FFP. And platelets as necessary. Heparin 5,000 units IV should be ready to be administered if carotid breach takes place. If needed, Adenosine 6mg or 12mg should be ready to be used in case of cardiac pause. Burst EEG suppression should be induced using Pentobarbital, Etomidate, or Propofol. Following surgery, the patient should remain intubated, and, with the anesthesiologist present, the operating room staff should prepare transport of NeuroIR and be ready to contact Respiratory Therapy for transport, as well as radiology (to arrange for head CT after angiography). The Intensive Care Unit (ICU) should be prepared to set up possible 1:1 nursing support, serial H&H, tight SBP management (120-140mmHg), ASA and Plavix if stent is placed, and daily TCDs. Surgeon should contact intensivist and update status of patient, in addition plan for repeat CTA or MRA to monitor for pseudoaneurysm (Figure 1).
High risk pituitary/endonasal surgery should be performed at a Pituitary Center of Excellence (COE), with a multidisciplinary team[8]. Pre-operative assessment of these cases in our comprehensive tumor board helps prepare the surgical team to identify which patients require a carotid injury timeout. These operations are performed with our ENT colleagues, as we value the importance of four-handed surgery with two sets of eyes helping prevent errors and valuable expertise should injury occur. Similarly, the neurosurgeon must take into consideration which cases should be scheduled alongside high-risk tumors – if any – as well as the condition of the surgeon (fatigue, conflicting meetings, etc…) up to the moment of incision. A well-prepared surgeon is equally important relative to an experienced operating room team, including the surgical technician, circulating nurse and the neuro-anesthesiologist. A fluid operating room setting, with readily available instruments and supplies can make a significant difference during a critical event in surgery.
Certain operating room technology is absolutely critical in endonasal surgery. Intraoperative image guidance system (i.e. neuronavigation), is very helpful in re-operation cases as well as or invasive tumors where normal anatomy is distorted. A “real-time” neuro navigation adjunct is the Doppler ultrasound probe. This has been shown to significantly decrease severe vascular injury, when employed frequently[4]. Fluorescence imaging can be helpful to identify vascularity of the regional anatomy (using indocyanine green – ICG – fluorescence), though this has not been shown to be of critical importance other than to assess flap perfusion. (Table 5)