Anesthesia for Head and Neck Cancer Surgeries

Introduction

Head and neck malignancies are a heterogeneous group of malignancies extending from the upper aerodigestive tract up to the larynx, including the thyroid gland, salivary glands, and paranasal sinuses. They account for more than 650,000 cases worldwide. Considering the current burden of head and neck malignancies and increasing survival, most anesthesiologists would be faced with providing anesthesia to these patients for both oncologic and nononcologic procedures. Difficult airway management, intraoperatively shared airway, prolonged duration of the surgery, and postoperative airway management are the main concerns for the anesthesiologist. The management of head and neck cancer patients is constantly evolving with respect to the type of surgery, reconstruction, and newer adjuvant therapies. Hence, it is imperative that we understand the anatomic and physiologic changes related to the head and neck cancer itself and its associated therapies. In this chapter, we will discuss the various anesthetic and other considerations during head and neck cancer surgery. These recommendations should supplement the routine evaluation and management of a patient undergoing major surgeries.

Cancer Surgery

Surgery remains the mainstay of treatment in head and neck cancer surgeries. Depending on the extent of surgeries and the stage of tumor, radiation or cisplatin/cetuximab-based chemotherapy may also be administered. Debulking surgery may be performed for palliation of symptoms and airway patency. The main goal of cancer surgery is to obtain disease-free margins. Hence unlike nononcologic procedures, surgical excision may often be extensive and accompanied by lymph node dissection, and often require reconstructive procedures.

Neck Dissection

The most common site of cancer spread is the cervical group of lymph nodes, which are commonly excised during head and neck cancer surgery. The patient may undergo a partial/selective, modified, or radical neck dissection along with the removal of the surrounding muscles, nerves, and veins.

Reconstructive Procedures

Plastic flap reconstructions are often required for cosmetic purposes and to help with chewing and swallowing. These may be pedicle flaps where the original blood supply of the structure is retained or they may be free flaps, which require microvascular anastomosis.

Applied Anatomy

One of the main concerns for the anesthesiologist following head and neck cancer surgery is the maintenance of a patent airway after surgical resection. Thus it is important to have an understanding of the role of various structures in maintaining a viable and patent airway. The mandible, maxilla, and the tongue form the external boundary of the airway. The genial tubercle over the mandible provides attachment to genioglossus and geniohyoid muscles, which maintain airway patency. Any loss of these structures may lead to the collapse of the airway, similar to that seen during rapid eye movement sleep. ^,

The pharyngeal muscles are crucial in ensuring that the food bolus enters safely into the esophagus. This is accompanied by the simultaneous anterior movement of the epiglottis to close the laryngeal inlet. Superior constrictors close the soft palate and the middle and inferior constrictors contract to push food into the esophagus. In addition, pharyngeal muscles also act as sphincters preventing regurgitation of food from the esophagus.

Preoperative Assessment and Optimization

Other than the routine assessment and optimization prior to major surgery, there are some special considerations in head and neck cancer patients.

Airway Assessment

A careful history of the signs and symptoms related to the airway is vital. The presence of progressive dysphagia, hoarseness of voice, or breathlessness/discomfort on lying supine may be a sign of a compromised airway. Laryngeal cancers may present with stridor and difficulty in breathing. These may present as emergencies and may sometimes require an immediate tracheostomy.

Apart from routine airway examination such as Malampatti grading, thyromental distance, and so on, there are special considerations during airway assessment in head and neck cancer patients that need to be evaluated carefully.

Primary Tumor

Proliferative intraoral lesions along the airway may add to difficulty at both bag-mask ventilation and laryngoscopy. These tumors can also bleed during laryngoscopic manipulation, especially tumors involving the base of the tongue and the vallecula. A thorough examination of the oral cavity should be performed to examine the size, location, and extent of oral tumor. In addition to looking at dentition, check for the presence of fibrous bands and any other conditions in the oral cavity. Lesions lower down in the airway can be assessed by viewing the imaging.

Facial Defects

Previous surgeries, the external proliferation of tumors, radiation, and so on, may lead to improper fit/seal of a face mask, making mask ventilation difficult, and sometimes even lead to bleeding due to manipulation.

Trismus

Fibrosis along the temporomandibular joint, due to radiation therapy of the primary tumor itself, submucous fibrosis due to tobacco chewing, and so on, may hinder mouth opening ( Fig. 21.1 ) Unlike trismus secondary to inflammation, this may not be relieved after induction of general anesthesia, thus making orotracheal intubation and supraglottic airway insertion often impossible. Trismus may be graded as follows: interincisal mouth opening up to or greater than 35 mm (M1), between 25 and 35 mm (M2), between 15 and 25 mm (M3), and opening less than 15 mm (M4).

Ankyloglossia

As the tumor infiltrates the root of the tongue, it hinders the protrusion of the tongue. Due to the restricted tongue movement, lateral displacement of the tongue may not be possible during direct laryngoscopy (DL), which may lead to poor glottis view and failed intubation.

Dentition

The tumor, radiation, tobacco chewing, and so on, may lead to loosening, weakening, and destruction of the teeth. Both mask ventilation and laryngoscopy may be difficult in edentulous patients.

Selection of the Nostril for Tracheal Intubation

The presence of intranasal anomalies such as spurs, septal deviation, nasal polyps, concha bullosa, and increased size of the turbinates should be ruled out both clinically and using imaging (computed tomography [CT] scan or anterior/posterior rhinoscopy) to select the more suitable nare for smooth passage of the tracheal tube nasally. Patient history and clinical examination should be performed to assess comfort while breathing and the blast of air on the back of the hand while alternately occluding the nare should be felt after administration of a nasal vasoconstrictor. This may also help in preventing trauma during nasal intubation. In case of equal patency, the nostrils opposite to the side of surgery should be selected especially for maxillectomies where the hard palate will be excised. Moreover, if there is no surgical preference, the right nostril should be preferred over the left, as in the case of the right nostril the bevel faces the nasal septum. This reduces the risk of damage to the nasal turbinates.

Tracheomalacia

A long-standing large thyroid mass may weaken the tracheal cartilage and longitudinal elastic fibers. The trachea becomes soft and susceptible to collapse in such cases. A narrowing of >50% along the posterior wall is significant and such patients may have a complete collapse of the airway under anesthesia, and may require tracheostomy or intraoperative aortopexy/bronchopexy to maintain a patent airway postoperatively. Patients commonly present with asthma-like symptoms which may be continuous or intermittent. Symptoms include prolonged and labored breathing, wheezing, or coughing. A thorough clinical examination and pulmonary function test should be performed to rule out respiratory conditions. Bronchoscopy, fluoroscopy, multislice helical CT imaging, or magnetic resonance imaging can be used to confirm the diagnosis preoperatively.

Airway Imaging

History and clinical examination should be complemented with reviewing the airway imaging. Most patients with head and neck cancer have had some prior airway imaging performed for disease evaluation.

X-ray helps determine the site and size of the mass and presence of compression or deviation of the airway, especially when anterior-posterior and lateral views are compared. Further investigations may be required to confirm the findings.

CT scan findings help assess the extent of disease and airway compromise. The CT scan can also be used to assess the patency of either nostril and the presence of aberrant spurs, which could cause tracheal cuff damage during a nasotracheal intubation.

An ultrasound of the neck performed preoperatively, especially in patients with difficult airways, helps identify the cricothyroid membrane, its anatomy, and any associated aberrant vessels. This might be extremely helpful if the need for emergency cricothyroidotomy arises.

Virtual endoscopy is a radiologic simulation of the anatomy of the airway extending from the oropharynx up to the carina. Previous CT scan images are reconstructed to create a video (3D “fly-through”) of the airway anatomy. This further improves our interpretation of the 2D CT scan images and helps better identify a difficult airway to make an appropriate airway management plan.

Diagnostic Airway Procedures

Patients may often be subjected to diagnostic procedures prior to major surgeries such as an indirect laryngoscopy (IDL) or awake fiberoptic laryngoscopy (FOL) in the outpatient department, or short diagnostic procedures such as direct- or microlaryngoscopy usually under general anesthesia, to assess the extent of the disease and obtain a diagnosis. These are extremely vital procedures that help to delineate the disease and decide on the further course of management. Findings from these procedures will help the anesthesiologist to plan for airway management.

Anemia

Malnutrition, dysphagia, chronic inflammation, and chemotherapy may cause anemia in these patients. Anemia has been associated with poor postoperative outcomes, in particular delayed recovery, intensive care unit (ICU) admission, hospital readmission, and postoperative complications, especially surgical site infection and flap failures (associated with hemoglobin <10 gm% or hematocrit <30%). ^, Depending on the available time prior to the surgery, anemia should be corrected prior to surgery.

Nutrition

Tumors along the aerodigestive tract, dysphagia, radiation-induced mucositis, ulcers, chemotherapy, and cancer cachexia add to the poor nutritional status of patients with head and neck cancer. Improving the nutrition preoperatively is associated with better postoperative outcomes in terms of wound healing, rate of infection, and postoperative complications. Malnutrition can be defined by a BMI of less than 18.5 and/or weight loss greater than 5%–10% of body weight. Nutritional assessment should be performed for all patients prior to surgery and high-risk patients should be referred to a dietician for early intervention. Patients with severe nutritional risk should receive nutritional support for 10–14 days prior to major surgery. All patients should consume a nutritionally balanced diet for at least 5 days prior to surgery.

Previous Cancer Therapies

Previous Surgery

The airway should be carefully evaluated in patients who have undergone previous surgery. The presence of flaps, mandibulectomy, previous tracheostomy, airway defects, and so on, may make both mask ventilation and tracheal intubation challenging. Awake tracheal intubation (ATI) may often be required in these cases.

Radiation

Radiation can significantly alter the airway making airway management difficult. Radiation can lead to fibrosis of the temporomandibular joint leading to trismus. It also affects dentition leading to loss of teeth. Edema secondary to radiation affects the tongue (glossomegaly, glossitis), glottis, and epiglottis. Kheterpal et al. found radiation to the neck an independent risk factor in patients with difficult bag-mask ventilation. Radiation-induced fibrosis in the oropharyngeal region makes the tissue extremely rigid and noncompliant, which presents as poor submental compliance ( Fig. 21.2 ). Obtaining a satisfactory glottic view might be difficult in such patients. Patients receiving head and neck radiation may also have limited neck movement. In addition, considering the possible laryngeal edema and increased risk of bleeding, the anesthesiologist should prefer to use smaller-sized endotracheal tubes (ETTs) in such patients. ^,

Radiation to the neck may lead to atherosclerosis and the risk of carotid artery stenosis, which increases the risk of stroke in these patients. In addition, radiation to the neck region may affect the thyroid follicles leading to hypothyroidism. It may also lead to damage of the baroreceptors, which may lead to extreme hemodynamic instability during the procedure. These effects of radiation may not always be visible, hence anesthesiologists should keep these changes in mind while managing such patients.

Chemotherapy

The two most common chemotherapeutic agents used in head and neck cancer are cisplatin and cetuximab. Other agents include the taxane group (paclitaxel, docetaxel), fluorouracil, and methotrexate. While platinum-based chemotherapy agents, in particular cisplatin, can adversely affect renal functions, the risk with newer agents such as oxaliplatin is lower. After platinum-based chemotherapy, patients should be assessed for renal and electrolyte imbalance, and in cases of significant impairment a nephrologist’s opinion should be sought. A complete blood count should be performed for all head and neck cancer patients to check for anemia and myelosuppression. Neutropenia (counts <1500/mm ³ ) increases the risk of postoperative infection and thrombocytopenia adds to the risk of intraoperative bleeding and should be corrected prior to surgery.

Geriatric Issues

The average age of head and neck cancer patients at presentation is 50–70 years. Hence geriatric considerations during assessment for surgery are essential in these patients. In addition to cardiac and other organ-related dysfunction specific to age, cancer-associated and chemotherapy-related cognitive dysfunction should also be assessed in the geriatric age group.

Effect of Tobacco and Smoking

Respiratory . Chronic obstructive pulmonary disease (COPD) is common in these patients secondary to chronic smoking. The reversible component of the disease should be optimized prior to surgery to reduce the risk of postoperative pulmonary complications. Any superimposed lung infection should also be treated. While it is desirable to stop smoking 8 weeks prior to surgery, it may not always be possible, and hence a minimum of a 12-h cessation is sufficient to reduce carboxyhemoglobin levels. Further cessation will improve mucociliary clearance and reduce airway reactivity.

Cardiovascular . Smoking is strongly associated with a higher risk of ischemic heart disease, hypertension, and atherosclerosis. It also increases the blood viscosity secondary to hypoxia-induced polycythemia in addition to increasing the number of white blood cells and platelets and fibrinogen levels in the blood. A cardiac assessment in these patients is essential.

Preoperative Pain Assessment and Management

Patients with head and neck cancer may present with preoperative pain secondary to cancer itself or due to therapy. The pain is higher as the cancer grows within the confines of a small space and due to the rich innervation of the region. In fact, 25%–60% of patients with head and neck cancer also suffer from neuropathic pain. Compression of the glossopharyngeal and vagal nerve leads to referred pain in the form of otalgia, tinnitus, and dental pain. The neuropathic component can be addressed using antiepileptics such as gabapentin and pregabalin and antidepressants such as amitriptyline and nortriptyline. Systemic analgesics such as opioids can reduce the severity of pain; however, consideration should be given to minimizing dosing to reduce the risk of side effects. Oral mucositis secondary to chemotherapy/radiation therapy also adds to the acute pain. Associated musculoskeletal pain responds well to nonsteroidal antiinflammatory agents (both systemic and topical) and antispasmodics. In addition, almost 30% of head and neck cancer patients suffer from chronic pain, which is associated with the advanced nature of the disease and associated therapies. Patients may even experience long-term musculoskeletal pain due to fibrosis involving the jaw. ^,

Anesthetic and analgesic requirements are much higher in these patients. Preoperative pain and the use of opioids are risk factors for the misuse of opioids in the postoperative period. Signs of opioid addiction should be identified. These patients should be flagged and monitored closely in the perioperative period. In addition, appropriate investigations should also be ordered to rule out complications secondary to long-term use of medications such as renal function test with the use of nonsteroidal antiinflammatory drugs (NSAIDs). Education regarding the possible ways to identify, prevent, and treat opioid misuse and overdose, starting in the preanesthesia room itself, should be imparted to clinicians.

Patient Education and Counseling

Patient education and counseling should encompass the perioperative period. This includes counseling regarding the surgery, anesthesia, and the recovery process. This improves patient satisfaction and compliance with recuperation. In addition, efforts to educate patients regarding opioid use in the postoperative period and after discharge, methods of safe disposal, and drug-return policies should be undertaken.

Intraoperative Management

Monitoring

The American Society of Anesthesiologists’ (ASA) recommendations for monitoring should be instituted for all patients prior to the induction of anesthesia. This includes continuous electrocardiogram (ECG) monitoring, pulse oximeter monitoring, and noninvasive blood pressure monitoring. BIS monitoring is recommended especially if total intravenous anesthesia (TIVA) is being planned to titrate anesthetic doses. Peripheral nerve stimulation (PNS) is also recommended to titrate muscle relaxant dosing and reversal. More invasive monitoring such as arterial cannulation and central venous cannulation should be reserved for patients with cardiac conditions or when extensive blood loss is anticipated.

Cardiac Output Monitoring

While cardiac output monitoring has shown benefit in other cancer surgeries, the data are comparatively scarce in head and neck cancer patients. Studies have shown the benefit of goal-directed fluid therapy (GDFT) in microvascular free flap surgeries for head and neck cancer patients. While the use of the transesophageal Doppler may be difficult due to proximity with the operating area, pulse contour analysis devices such as LiDCO or FloTrac may be used for dynamic cardiac output monitoring and assessing fluid responsiveness. ^,

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