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. ,
Temperature Monitoring
Head and neck cancer surgeries, especially with free flap reconstruction, are long duration surgeries, which may involve significant blood loss, and temperature fluctuations may be expected. In addition, since only the head area of the body is exposed during the surgery, there exists a risk of hyperthermia. Nasopharyngeal or esophageal monitoring might be difficult with the risk of displacement of the monitoring device during surgery.
Periintubation Oxygenation
Preoxygenation
Patients with head and neck cancer are anticipated difficult airways and hence preoxygenation is vital. One could use a face mask, or in some cases where the adequate fitting of a face mask is not possible due to facial defects, alternate methods of preoxygenation like high-flow nasal cannula oxygen (HFNCO) may be used.
Apneic Oxygenation
Apneic oxygenation is a technique to constantly replete oxygen stores during the period of apnea. This helps prolong the safe apnea time during which the airway can be secured. Apneic oxygenation can be delivered using a high-flow nasal oxygenation technique called Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) or alternately by supraglottic jet oxygenation and ventilation (SJOV).
Commonly Used Tracheal Tubes
RAE Tubes
The North Pole endotracheal tube made of ivory, which curves away from the surgical site, is the most commonly used ETT for nasal intubation in head and neck cancer surgeries. These tubes are much softer than the routine polyvinyl chloride (PVC) tubes and cause less trauma during insertion. However, they are opaque and obscure any tube blockade and due to the preformed curve, suctioning is not easily performed through the ETT. Moreover, the length, narrower lumen, and preformed curve add to the resistance during spontaneous breathing. Hence it is recommended to cut these tubes along the prelabeled black mark to reduce airway resistance and facilitate suctioning in the postoperative period. The insertion of North Pole ETT over the fiberoptic bronchoscope is also difficult due to the curvature. The North Pole tube needs to be straightened manually to be loaded over the bronchoscope. Due to some of the limitations mentioned above, some prefer to use PVC tubes for tracheal intubation, though they are stiffer.
Flexometallic Tubes
The advantage of flexometallic ETTs is that they are nonkinkable and less traumatic. However, these tubes are floppy making them difficult to insert. These tubes are particularly useful during laryngectomy surgery when the end stoma is being fashioned, to keep away from the field of surgery.
Electromyographic Tube
Intraoperative nerve monitoring (IONM) is being increasingly used to help identify nerves. The common indication includes thyroid surgery, partial laryngectomy, neck dissection, carotid endarterectomy, and so on. These are standard PVC tubes with conductive silver ink electrodes. There is a dark black cross-band that guides in electromyographic (EMG) tube placement. These tubes have a minimum outer diameter of 8.8 mm and hence are preferentially used for oral intubation.
Plan for Airway Management—Awake Versus Asleep
It is essential to make a plan for airway management prior to the induction of anesthesia. The decision of whether to secure the airway awake or asleep is crucial. This planning should include careful history taking, assessment of the airway with a review of airway imaging, and a discussion with the surgeon. If the airway management is planned under general anesthesia, a backup plan for rescue ventilation in case of inability to perform tracheal intubation, including equipment and preparedness for performing an emergency cricothyroidotomy, in case of complete ventilation failure should be made. Patients with intraoral surgery usually require a nasal ETT. Skull base fractures and bleeding disorders (risk of epistaxis) are relative contraindications.
Tracheostomy Under Local Anesthesia
In patients in whom there is a prior plan for tracheotomy, for example, a laryngectomy where the glottic opening is severely reduced or a plan for extensive resection where the airway patency is likely to be compromised postoperatively, the patient may undergo tracheostomy under local anesthesia prior to administration of general anesthesia.
Awake Tracheal Intubation
ATI is considered the gold standard in patients with an anticipated difficult airway. It is prudent to familiarize oneself with various available techniques. The recent guidelines for ATI in adults help practitioners to better plan, perform, and address complications related to the procedure. A combination of sedation, topicalization, oxygenation throughout the procedure, and proper performance of the procedure is key to success.
Premedication
To reduce the risk of bleeding in case of nasal intubation, topical vasoconstrictor agents such as pure alpha-agonist agents (oxymetazoline, xylometazoline) can be used. Antisialagogue agents such as glycopyrrolate given intravenously reduce the amount of secretions and ensure a dry field for better visibility during the procedure. In addition, it prevents the local anesthetic from getting diluted with secretions and aids better absorption. These agents should be administered at least 15 min prior to the procedure giving enough time for its action.
Sedation
Patients with head and neck malignancies might have a compromised airway, and hence anesthesiologists should be judicious with the use of sedation. However, mild sedation helps in tolerating awake intubation and increases the success of the procedure. The preferred sedatives for awake intubation include intravenous infusion of dexmedetomidine or remifentanil, mainly due to shorter duration of action, easy titrability, and an increased safety margin. Proper patient counseling prior to the procedure is paramount and increases patient tolerability, often with no requirement for sedation.
Anesthetizing the Airway
Intranasal 2% lignocaine jelly, viscous lignocaine gargle (concentration, 2%), pressurized bottles using 10% lignocaine, and atomizers can be used to anesthetize parts of the airway for awake intubation. The airway can further be anesthetized using the “SprAY as you GO (SAYGO)” technique. This is, however, performed while performing fiberoptic bronchoscopy. The local anesthetic is injected through the suction port of the scope using a syringe or via an epidural catheter passed through the suction port with the tip distal to the tip of the bronchoscope. It anesthetizes the part of the airway distal to scope. More invasive techniques include translaryngeal injection of lidocaine and regional nerve blocks such as glossopharyngeal nerve block, and superior laryngeal nerve block can also be used to anesthetize the airway prior to performing awake intubation. However, these invasive techniques are not routinely recommended or required when good topical anesthesia is used.
Oxygenation
During ATI, nasal oxygen should be continued throughout the procedure. The use of HFNCO especially when sedation is administered can increase the margin of safety.
Types of Awake Tracheal Intubation
i. Intubation With the Flexible Bronchoscope
Most patients, especially with oral pathologies, require a nasal ETT. The flexible bronchoscope (FB) can be used to intubate these patients nasally. A retromolar technique of insertion may also be used. The ETT is mounted over the scope after adequate lubrication, and the scope is introduced along the base of the nose in case of nasal intubation, and between the molars and cheeks in case of retromolar intubation, and guided through the vocal cords. This procedure takes time and requires a skilled operator. The passage of the ETT over the scope through the vocal cords is not performed under vision. Combining this technique with a videolaryngoscopy (VL) or DL can overcome this limitation. Excess secretions, bleeding, or difficulty in maneuvering the scope around the tumor may make this procedure challenging
ii. Awake Video-laryngoscopy
Awake VL is gaining popularity as an alternate technique to awake FB intubation because it is easier to perform and takes less time. A meta-analysis comparing awake intubation using VL and FB found VL to be associated with shorter intubation time. There was no reported difference between the two techniques regarding the first attempt success rate, rate of complication, and level of patient satisfaction. However, most studies in this meta-analysis did not include patients with trismus or intraoral cancers where the use of VL may not always be feasible and FB-guided intubation still remains the gold standard.
iii. Retrograde Intubation
This involves the passage of an ETT over a guide (epidural catheter/guide wire) passed in a retrograde manner through the cricothyroid membrane/transtracheal puncture using an epidural needle or intravenous cannula (16/18 G) into the nasal or oral cavity. This procedure needs patient cooperation and at least 0.5 cm of mouth opening to retrieve the retrograde guide. Though the intubation is completely blind, the success rate is higher than blind nasal as the ETT is railroaded over a guide present in the trachea. Complications include injury to vocal cords, bleeding secondary to aberrant vessels from superior thyroid artery, and injury to the thyroid gland. ,
iv. Blind Nasal Intubation
This involves blindly guiding the ETT through the nose towards the larynx. The ETT passage is guided by the help of the patient’s breath sounds or an Et co 2 trace during spontaneous breathing. This procedure requires skill and experience and has a low success rate. Complications include trauma to oral, pharyngeal, and laryngeal structures, as the tube is passed blindly into the trachea.
Blind techniques should be discouraged in the era of VL- and FB-guided intubations to avoid complications and improve intubation success rates.
Tracheal Intubation After General Anesthesia
Depending on the plan of airway management, the induction of general anesthesia may vary. More commonly used techniques include TIVA or balanced anesthesia using a combination of inhaled and intravenous anesthetics, analgesics such as opioids, and sedatives such as benzodiazepine. Muscle relaxants should be used at the time of induction of anesthesia to improve glottis view during DL. Since head and neck surgeries are superficial surgeries, they do not require profound relaxation during the further course of the surgery.
Fluid Management
A large-bore venous cannula is essential to rapidly replace lost volume when required. Current studies indicate that GDFT using dynamic markers of fluid resuscitation, such as stroke volume variation (SVV), pulse pressure variation (PPV), and so on, help in reducing the amount of fluid given intraoperatively, postoperative complications, and hospital stay especially in free flap surgeries. The most commonly used fluids include PlasmaLyte-A and Ringer’s lactate.
Blood Transfusion
The need for intraoperative blood transfusion depends on the preoperative hemoglobin values and intraoperative blood loss. Concerns exist regarding blood transfusion and increased incidence of flap failure. Although a study by Stahel et al. found that keeping a hematocrit trigger as low as 25% did not increase the risk of flap-related complications, this still remains a bone of contention. A recent study by Kim et al. found on multivariate analysis that the lowest perioperative hemoglobin was independently associated with flap failure, and that blood itself was not associated with the increased flap failure rate. A transfusion trigger value of 7 gm% for is usually practiced in stable patients.
Vasopressor Use
For most major resections, the inability to maintain normal blood pressures despite adequate fluid resuscitation is an indication for starting vasopressors, which are slowly tapered as the blood pressure normalizes. The real concern with the use of vasopressors is flap failure due to vasospasm when used in free flap surgeries. Physiologically, hypoperfusion will reduce oxygen delivery across the organ and also increase the risk of flap failure. However, a recent study by Fagin and Petrisor, found that 85% of cases undergoing free flap surgeries require vasopressor boluses, and use of vasopressor intraoperatively was not associated with an increase in flap failure or pedicle compromise rate. ,
Analgesia
Opioids form the mainstay of intraoperative analgesia in these patients. In addition, they also improve tube tolerance. Other adjuvants such as NSAIDs, acetaminophen, and so on, add to multimodal analgesia. With the recent shift towards opioid-free anesthesia, the role of N-methyl- d -aspartate (NMDA) antagonists, such as ketamine, and alpha-2 agonists such as dexmedetomidine, gabapentin, pregabalin, and lidocaine is increasing to reduce perioperative opioid requirements.
Nerve Blocks ,
Inferior alveolar nerve block may be given intraoperatively for mandibular surgeries. In addition, there are various intraoral and extraoral techniques for maxillary and mandibular nerve blocks used for maxillofacial surgeries. Superficial cervical plexus block can be used for neck dissection surgeries. However, these techniques are rarely practiced.
Prophylaxis for Postoperative Nausea and Vomiting
Depending on the risk factors for postoperative nausea and vomiting (PONV), prophylaxis should be administered. Anesthetic management using TIVA reduces the risk of nausea and vomiting intraoperatively. 5-HT 3 receptor antagonists, steroids, scopolamine patch, and NK-1 receptor antagonists can also be used to reduce the incidence of PONV.
Postoperative Airway Management Plan: Tracheostomy Versus Tracheal Tube
Tracheostomy was traditionally considered a safer technique for airway management in patients undergoing head and neck cancer surgeries. Postoperative edema, reduced airway caliber, altered anatomy, and postoperative bleeding are the main reasons for advocating a tracheostomy ( Fig. 21.3 ). However, airway complications are high in patients with a tracheostomy. The alternative to tracheostomy is a delayed extubation strategy in select patients, where the ETT is kept overnight, allowing the edema to settle and the patient is extubated the next morning ( Fig. 21.4 ).
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