Functional Endoscopic Sinus Surgery (FESS) is performed in one of the most anatomically compact and delicate regions of the body. For anesthesiologists, every millimeter of this surgical field carries significance, not only because of its proximity to critical structures but also due to the array of reflexes that may be triggered and the need to balance surgical visibility with patient safety.

Anatomical Relevance: Why Every Millimeter Matters

The orbit lies just millimetres from the operative field, making it highly vulnerable. Injury here can cause orbital hematoma or even vision loss. Additionally, orbital pressure or trauma may trigger the oculocardiac reflex (OCR), manifesting as bradycardia or even asystole. Anesthesiologists must remain vigilant and prepared to interrupt surgery and treat OCR promptly.

The optic nerve, though less frequently involved, is particularly sensitive to ischemia. Prolonged hypotension can lead to irreversible vision loss, so sustained drops in blood pressure should be avoided.

Breaching the anterior cranial fossa is another risk. A tear here may produce a cerebrospinal fluid (CSF) leak, predisposing to meningitis or pneumocephalus. Manipulation near this region may also activate the trigeminocardiac reflex (TCR), causing profound bradycardia or hypotension. Close hemodynamic control and careful observation for CSF leaks are therefore essential.

The ethmoid roof, especially in Keros type III anatomy, represents another danger zone. Its deeper olfactory fossa makes it more susceptible to breach, with the dual risk of CSF leak and TCR activation. Maintaining adequate anesthesia depth and ensuring gentle surgical technique are crucial protective strategies.

The lamina papyracea, the paper-thin medial wall of the orbit, is extremely fragile. Breach can result in retrobulbar hemorrhage and provoke OCR. If the reflex does not resolve with cessation of stimulus, atropine should be administered promptly.

The vascular supply of the sinuses, notably the anterior and posterior ethmoidal and sphenopalatine arteries, can cause troublesome bleeding if injured. Anesthesiologists can support the surgical field by positioning the patient in reverse Trendelenburg (15–30 degrees) and maintaining low-normal mean arterial pressures using total intravenous anesthesia (TIVA).

Finally, the sphenoid sinus sits beside two vital neighbours: the optic nerve and the internal carotid artery. Breach here carries catastrophic consequences. To minimize risk, anesthesiologists should avoid blood pressure surges during drilling and maintain stable anesthetic depth.

Pathophysiology-Driven Anesthesia Planning

Different subtypes of chronic rhinosinusitis (CRS) bring their own challenges to the anesthetic plan.

Patients with CRS with nasal polyps (CRSwNP) typically exhibit Type 2 inflammation characterized by eosinophilia and cytokines such as IL-4, IL-5, and IL-13. This produces friable, edematous mucosa. Airway stimulation can easily provoke laryngospasm or bronchospasm. In these patients, deep extubation under good oxygenation is often preferred to minimize coughing and bleeding.

In CRS without nasal polyps (CRSsNP), the mucosa is more fibrotic, though bleeding may still trigger gagging or swallowing. Oropharyngeal packing helps reduce the risk of blood tracking into the pharynx.

Biofilm-associated CRS is driven by persistent low-grade inflammation. These patients may have poorer mucosal healing, particularly if perfusion is compromised. For them, prolonged hypotension should be avoided and adequate tissue oxygenation maintained throughout surgery.

Reflexes in FESS: Sudden Physiological Challenges

FESS is notorious for reflex-mediated responses. Four are particularly important for anesthesiologists.

The trigeminocardiac reflex (TCR) is triggered by manipulation of trigeminal branches, usually V1 or V2. It produces bradycardia, hypotension, and even asystole. Adequate anesthesia depth reduces the risk, and in selected patients, anticholinergic prophylaxis may be considered. If the reflex occurs, surgery should pause, anesthesia should be deepened, and atropine or glycopyrrolate administered.

The oculocardiac reflex (OCR) arises from orbital pressure or breach of the lamina papyracea. It results in bradycardia or junctional rhythms, sometimes progressing to asystole. The preventive strategy is to avoid orbital pressure. If it occurs, manipulation should cease and atropine given.

The swallow or gag reflex may be triggered when blood or irrigation enters the pharynx. This leads to hypertension, coughing, or desaturation. The best prevention is a throat pack and sufficient anesthesia depth. Suctioning before emergence is essential.

Finally, laryngospasm may occur when blood contacts the vocal cords during light anesthesia. The airway may obstruct completely, causing desaturation and bradycardia. Smooth emergence and suctioning before cuff deflation are critical preventive steps. If it occurs, management includes 100% oxygen, jaw thrust, and CPAP; persistent spasm requires succinylcholine.

Creating the Optimal Surgical Field

FESS demands a clear, dry surgical field, which requires careful anesthetic strategies. Controlled hypotension is a cornerstone, with mean arterial pressures between 60 and 70 mmHg in healthy adults.

TIVA with propofol and remifentanil is often preferred, offering smooth titration and less interference with reflexes. Positioning the patient in reverse Trendelenburg by 15–30 degrees further reduces venous congestion. Ventilation strategies should include mild hypocapnia (PaCO₂ of 33–35 mmHg) to decrease mucosal blood flow.

Airway management is also key. Preformed RAE tubes, well-secured, keep the surgical field unobstructed and reduce the risk of kinking. A throat pack, inserted after induction and removed before extubation, prevents aspiration of blood.

Emergence must be managed smoothly. Administering intravenous lidocaine (1–2 mg/kg) before extubation blunts the cough reflex, minimizing bleeding. Finally, suctioning should always be performed under direct vision before cuff deflation to reduce the risk of laryngospasm.

Conclusion

Anesthetic management of FESS requires more than routine vigilance. It demands a precise understanding of nearby anatomy, anticipation of sudden reflex-mediated events, tailoring the anesthetic approach to the underlying pathophysiology of CRS, and applying strategies that optimize the surgical field while preserving patient safety. In this high-stakes, millimetre-sensitive surgery, the anesthesiologist plays a central role in orchestrating stability and ensuring successful outcomes.