Surgery Medical School Crash Course (Unabridged) - 09 A_T_F

Head and neck surgery requires specialized anesthesia techniques. Surgeons performing these surgeries may be plastic or cosmetic surgeons, ophthalmologic surgeons, otologic surgeons, oral and maxillary facial surgeons, or craniofacial surgeons. Anesthesiologists must manage the airway and ventilation during these surgeries. Patients with certain medical conditions, such as uncontrolled hypertension or lung disease, may not be good candidates for certain techniques. Patients with obstructive sleep apnea may be more sensitive to medications and have difficulty waking up after surgery. Head and neck cancer patients may have additional complications, such as airway swelling and difficulty swallowing. Preoperative evaluation and imaging tests help determine the best airway management strategy. The anesthesia plan for head and neck surgery requires collaboration between the surgeon and anesthesiologist. Various devices and techniques are used to ensure a clear and protected surgical field. G Chapter 6, Head and Neck Surgery. This chapter is devoted to head and neck surgery. Head and neck surgery is unique in that specialized anesthesia techniques need to be used to ventilate and to provide anesthesia for the patient as both the surgeon and the anesthesiologist need to have access to the patient's head and neck area. Surgeons who perform head and neck surgery may be plastic or cosmetic surgeons, ophthalmologic surgeons, otologic surgeons, oral and maxillary facial surgeons, or craniofacial surgeons. Anesthesia for Head and Neck Surgery. There are many types of surgery associated with head and neck surgery, from basic procedures like a tonsillectomy to highly precise surgeries of the larynx, nerves of the head and neck, and image-guided surgeries of the skull and brain. There is extremely sophisticated transoral robotic surgeries for laryngeal cancer and surgeries for patients who have obstructive sleep apnea. When surgeries are being done on the head and neck, it is up to a well-trained anesthesiologist to manage the airway and ventilation, when this is the exact place where the surgeon will also need to have surgical access. Before the surgery, the anesthesiologist must take a thorough history and do anesthesia-directed physical examination. There are many medical conditions that are of particular concern for patients undergoing surgery to the head and neck. For example, patients who have uncontrolled hypertension, cerebrovascular conditions, coronary artery disease, chronic renal disease, or advanced liver disease, techniques that involve a controlled hypotension and intraoperative hypotension should be avoided. Patients with lung disease and ventilation-perfusion mismatch problems may not be good candidates for intraoperative techniques that include spontaneous ventilation, apneic intermittent ventilation, or jet-type ventilation. Obstructive sleep apnea, or OSA, is a widespread problem among patients who have head and neck procedures, and the condition may not be diagnosed at the time of surgery. Patients with OSA tend to be more sensitive to opiate medications and sedatives and will have a harder time waking up after surgery. Patients who have dysfunction of cranial nerves 10, 11, and 12 may have an increased risk of aspiration or obstruction of the airway upon anesthesia induction, and may have difficulties with airway management in head and neck surgeries. Other issues associated with head and neck surgery involve the treatment of patients with head and neck cancer. Many of these patients are smokers or drink alcohol, which may make them predisposed to heart disease, lung disease, liver disease, and other health problems that are associated with having surgery. These patients are also commonly anemic, so they need to have a CBC and electrolytes performed prophylactically. Radiation for head and neck cancers often cause airway swelling, dry mouth, difficulty swallowing, and poor oral intake, which makes them at risk for hypotension secondary to anesthesia. Radiation if given for head and neck cancer may also make tracheal intubation and mask ventilation more problematic because of tissue fibrosis, poor compliance of the tissues, an inability to open the mouth fully, and problems extending their neck. Glottic and epiglottic edema can make intubation challenging. The anesthesiologist must evaluate the airway carefully because these patients will invariably have challenging airway concerns. A history of a past airway intubation that was difficult is the best predictor of having a difficult airway issue again. Patients who've had an easy intubation in the past may have difficulty in the airway management because of disease progression. Difficulty aeration can occur in up to 12% of head and neck cancer patients. Head and neck cancer patients may have difficulty with video laryngoscopy, or VL, when compared to normal patients. The patient with potential airway problems needs a comprehensive preoperative airway assessment starting with a thorough history and looking at the physical characteristics of the upper airway. There are several assessment tools available that have limited usefulness in patients with head and neck pathology as they do not account for lower airway difficulties, aspiration risks, or tongue pathology, all of which can worsen adequate airway access delivery. Signs that a patient has airway obstruction should be looked for, including things like shortness of breath while at rest or exercising, difficulty swallowing, stridor, voice changes, and cough. Coarse, scratchy voices are associated with glottic disease, while muffling of the voice may be an indication of supraglottic disease. There may be physical evidence of respiratory disease, such as the use of intercostal muscles, agitation, and tachypnea. Pharyngeal restriction can manifest as having drooling, expiratory snoring, and dysphagia. The finding of inspiratory stridor at rest represents the most worrisome finding as it suggests a reduction in airway diameter of at least 50%. Lower airway problems may also be a problem in patients having head and neck problems. There can be narrowing of the trachea or tracheobronchial tree, which can complicate intubation and ventilation. Preoperative Endoscopy and Imaging Tests. If patients are suspected of having a difficult intubation and airway management, they should have a routine chest x-ray, magnetic resonance imaging or MRI, flexible nasal laryngoscopy, or computerized tomography, CT scanning, of the head and neck area. The results help define any structural narrowing, the mobility of the vocal cord, and any laryngeal or tracheal problems that might be helpful in maximizing ventilation and intubation techniques. Preoperative nasal endoscopy is generally required for head and neck surgery, although Preoperative Endoscopic Airway Evaluation, or PEAE, can be done by the anesthesiologist before surgery. This can provide extremely precise information about the anatomy of the upper airway and laryngeal anatomy to facilitate the formation of the airway management strategy and can tell if supraglottic airway management strategies are possible. Surgical Issues in Head and Neck Surgery. The anesthesia plan for head and neck surgery needs input from the head and neck surgeon and the anesthesiologist together. Strategies must be done to evaluate the airway, and the selection of airway management devices must be undertaken. Backup strategies must be identified if problems arise in surgery. The airway is often shared by the surgeon and the anesthesiologist. The airway must be protected from surgical debris, irrigation fluid, and bleeding. For this reason, a throat pack may be necessary, and the endotracheal tube must be carefully sized to avoid leakage or extubation during the surgery. Most patients will require an endotracheal tube of at least size 6, with nasal intubation required for many oral and pharyngeal surgeries. For patients requiring microlaryngeal surgery, a small 5 mm sized endotracheal tube is used that will make way for the introduction of surgical instruments. It should be securely taped to the lower jaw to prevent displacement of the tube during laryngeal surgery. There are specialized endotracheal tubes that are safe for use with lasers, and will preserve the nerve integrity during surgery. Supraglottic airways are preferred instead of endotracheal tubes to provide a smoother reawakening from surgery. Many head and neck surgeries require a completely still surgical field that will allow for surgical access that is free from restrictions. For this reason, the breathing circuit should connect to the endotracheal tube just above the head, so the surgical field is spared from having anesthesia instrumentation in the field. Blood pressure and pulse oximetry measurements should be taken from the opposite side of the surgeon to avoid disturbing the surgery. The choice of anesthesia technique usually involves general anesthesia for head and neck surgeries. This protects the airway, ensures good air exchange, eliminates patient movement, provides complete amnesia for the patient, and doesn't disturb the surgeon. The main things monitored in surgery include blood pressure, an EKG rhythm strip, oxygen saturation, capnography, and patient temperature. Continuous pressure arterial monitoring can be used with an intra-arterial catheter placement for patients with coronary artery disease, cerebrovascular disease, kidney failure, high blood pressure, and cerebrovascular disease. A central venous catheter may be put in place when fluid status is needed to be precise and can help identify hypotension and can tighten the control of fluid administration for patients with chronic renal insufficiency. A processed electroencephalogram can be used to access the degree of anesthesia, particularly in older, frail patients or in patients undergoing total intravenous anesthesia. An adequate depth of sedation must be monitored, especially when neuromuscular blocking agents are contraindicated. In intubating head and neck surgical patients, direct laryngoscopy should be used, but few attempts at intubation should be indicated, as the airway is likely to bleed and become edematous. Video laryngoscopy is recommended for difficult intubations to increase the chances of a successful first attempt at intubation. The surgeon can do the intubation with a direct laryngoscope or rigid bronchoscope if other attempts fail. Flexible scope intubation has also been employed. Supraglottic airways. Supraglottic airways or SGAs may be difficult to insert in head and neck surgeries, especially in those who have had neck irradiation, inability to fully open the mouth, or pathology of the glottis, hypopharyngeal tissue, and subglottic pathology. Another type of SGA can be used called the laryngeal mask airway or LMA. It has the advantage of having improved ventilation and a reduction in aspiration risk. Bougie introducers can be used for insertion of SGAs in order to maximize airway placement with the first attempt. Similar SGAs, such as the combitube and laryngeal tubes, LTs, are often employed in head and neck surgery who have limited ability to open their mouths or have a lot of bleeding of the upper airway when rapid intubation in necessarily. They are often used by pre-hospital staff as it provides fast intubation with minimal expertise in insertion. Optical laryngoscopy and a flexible scope can help with severely compromised airways. The glottis can be visualized and the flexible scope can be easily manipulated, especially with an optical stylet or flexible scope to work through distorted glottis anatomy or airway cancers. This way, there is less chance of disturbing the tumor. A transtracheal jet ventilation device can be used through the trachea. It is placed before general anesthesia and offers good tracheal oxygen insufflation in complicated cases. A cricothyrotomy catheter can similarly ventilate the patient using a low-pressure oxygen source, such as an ambu bag or anesthesia breathing circuit set to low pressures. In rare cases, the surgeon must perform a tracheostomy before going ahead with head and neck surgery in patients with severely compromised airways, either before the procedure or after recovering from the procedure. It can be done under local anesthesia with or without sedation. Anesthesia induction. There are many medications and techniques that can be used to induce anesthesia in head and neck surgery. IV induction is done using propofol with good success. Other patients can have inhalation induction, but this isn't as successful as IV induction. Patients with advanced airway blockage don't inhale the induction agents very well and have difficulty obtaining adequate anesthesia. Inhalation anesthesia needs the approval of the surgeon and should be used for patients with non-collapsing lesions and an intact surgical airway. Intraocular blocking medications can be used in the induction procedure to enhance intubation, but should be avoided intraoperatively when neuromonitoring is used. The main goals of head and neck anesthesia with IV or inhalation anesthesia include the following. The maintenance of a stable degree of anesthesia during surgical stimulation of the airway. The minimization of bleeding. The maintenance of a still operative field. The prevention of nausea and vomiting. The ability to smoothly recover from anesthesia. And the ability to quickly recover from the anesthesia so they can be discharged to home. The choice of anesthetic agents can be inhalation anesthetics, intravenous anesthetics, or both. Propofol has the primary advantage of reducing the post-anesthesia nausea and vomiting, which can be severely dangerous in the post-operative head and neck patient. Total intravenous anesthesia using opiates and propofol are the preferred ways of promoting anesthesia, but require EEG monitoring to ensure adequate anesthesia. Rapid anesthesia can be given with the IV use of both propofol and an opiate, such as remafentanil, sufentanil, alfentanil, or fentanyl for pain control. The muscle tone of the pharyngeal muscles and laryngeal muscles is depressed when fentanyl and propofol are used, which reduces the hormonal stress response in head and neck surgery so that hypotension can be facilitated in surgery. There is usually a faster recovery when compared to inhalation anesthesia, and less nausea and vomiting after awakening. IV anesthesia is almost the only adequate anesthesia when jet ventilation or intermittent apnea ventilation is undertaken. Opioids are used to help maintain anesthesia. The drug used depends on the type of head and neck surgery being performed, the length of the procedure, the expected amount of intraoperative stimulation of the patient's pain reflexes, and the expected amount of postoperative pain. Opiate-based anesthetics include the suppression of airway reflexes, a decreased need for IV anesthesia, better controlled hypotension during surgery, decreased patient movement in surgery, neuromonitoring facilitation, easy emergence from anesthesia, and better pain control after surgery. Inhalation anesthetics include sevoflurane, which is preferred over desflurane and isoflurane because it irritates the airways the least and there is the least postoperative coughing and better recovery from anesthesia. There is an increased risk of vomiting after awakening from anesthesia with inhalational anesthetics, so sometimes propofol is added to the inhalational drugs to reduce this side effect. Good controlled hypotension with a systolic blood pressure of just under 100 is desirable for head and neck surgeries to decrease bleeding in the surgical field. The need for controlled hypotension and the degree of hypotension desired is discussed with the surgeon and it must be avoided in patients with cerebrovascular disease, uncontrolled high blood pressure, significant atherosclerotic heart disease, chronic renal disease, and advanced liver disease. Things that can induce hypotension during surgery include intravenous remifentanil and propofol. These usually work without having to resort to vasoactive medications for the management of excessive hypotension. These medications have a low risk of rebound hypertension and tachycardia after they are withdrawn after the surgical procedure. Other choices of medication include beta blockers, nitroprusside, calcium channel blockers, alpha-adrenergic agonists, magnesium sulfate, and high-dose inhalational anesthetics. Ventilation Techniques There are several ways to successfully ventilate the patient that can improve surgical access during surgery to the larynx, including supraglottic ventilation, infraglottic ventilation, transtracheal jet ventilation, and apneic intermittent ventilation. Jet ventilation involves both high-frequency and low-frequency ventilation. High-frequency jet ventilation is used more often and is exclusively the procedure of choice for transtracheal and infraglottic ventilation. The rate can be as high as 150 breaths per minute with extremely small tidal volumes. This allows for minimal motion of the larynx and a still surgical field. There is increased dead space ventilation so there is a risk for carbon dioxide retention. Infraglottic jet ventilation is the most commonly used jet ventilation procedure. It makes use of a 3-4 cm double-lumen catheter or metal cannula placed in the trachea with the use of laryngoscopy. The end tidal carbon dioxide level can be intermittently monitored through one of the lumens to measure the patient's carbon dioxide retention. Supraglottic jet ventilation uses a jet nozzle placed just above the glottic opening. The advantage is a low risk for barotrauma to the patient's airway. It is inserted by the surgeon using direct laryngoscopy allowing for full view of the larynx. There is increased movement of the vocal cords with this anesthesia technique and the end tidal carbon dioxide level cannot be determined. Transtracheal jet ventilation bypasses the larynx altogether. A long catheter or a rovucin type cannula is inserted directly into the cricothyroid membrane. In intermittent apneic ventilation, the endotracheal tube is temporarily and intermittently removed by the surgeon to have clear access to the surgical field. It must be replaced using an endoscope to intermittently ventilate the patient. Disruptions for postoperative nausea and vomiting. Patients having head and neck surgery should have aggressive management for postoperative nausea and vomiting. Vomiting and even retching can cause the patient's venous pressure and will increase the risk for hematoma formation, disruption of any grafts placed, and postoperative bleeding. The best way to avoid these complications is to use an intravenous 5-HT agonist. Intravenous anesthesia with propofol, intravenous dexamethasone, and a scopolamine patch for extremely high risk patients. Pain control after head and neck surgery. Pain control after surgery begins during the surgical procedure and can even begin before the surgery commences. The opiate given is based on patient factors and on the expected amount of postoperative pain the patient will have. After surgery, acetaminophen or gabapentin can be given, along with non-steroidal anti-inflammatory drugs, NSAIDs, and intravenous, oral, or intramuscular opiate analgesics. Some patients will do well with peripheral nerve blocks or local anesthetic infiltration of the surgical area. Emerging from anesthesia. Emerging from anesthesia should be smooth and should be associated with rapid awakening and uncomplicated extubation that doesn't involve patient coughing, bucking, or straining. Careful monitoring of the blood pressure needs to take place to avoid postoperative hypertension. There are more complications with head and neck extubation, including laryngeal spasm, post-extubation airway swelling, postoperative blockage of the airway, and the emergent need for reintubation. Postoperative care. Many head and neck procedures are outpatient procedures in which the patient is discharged to their home after anesthesia recovery. Pain, nausea, and vomiting must be managed in the post-anesthesia care unit and should be anticipated that it might occur at home, so medications for nausea and vomiting to be taken home are a priority. If the extubation is smooth and if no reintubation is necessary, the patient only needs a few hours of monitoring before getting a ride home. Types of head and neck surgery. Head and neck surgery has evolved greatly over the last several decades. A main type of head and neck surgery is called EHNS, or minimally invasive and endoscopically performed head and neck surgery. This allows the surgeon to remove laryngeal and pharyngeal tumors using cameras and internal incisions only that do not affect the patient's external experience, speech abilities, and swallowing abilities. The endoscope involves a long, thin tube with a lighted microscopic camera at the end that allows the surgeon to visualize the internal pharyngeal structures. The endoscope is inserted through the mouth and there is good visualization of any tumors of the larynx or pharynx. State-of-the-art and precision surgical instruments are also inserted through the mouth so the complete surgery can be done internally. The main advantage of this type of surgery is a minimum of bleeding, decreased pain, fewer inpatient hospital stays, faster recovery to a normal diet, and a much improved cosmetic appearance after the surgical procedure. The EHNS procedure may be so successful that no chemotherapy or radiation might be necessary after the surgery. There are two types of EHNS. The first type is transoral robotic surgery and the second type is transoral CO2 microsurgery. Both treatments have made vast improvements in the surgical management of throat cancers. In transoral robotic surgery or TORS, the surgeon uses a joystick and a console to manipulate robotic tools using three-dimensional imaging of the throat. There are generally four robotic arms, one of which is a high-definition camera system, while the other three involve the use of tiny surgical instruments that perform the actual surgery. It eliminates errors made by hand tremoring of the surgeon that could occur in a regular procedure. Transoral laser microsurgery or TLM has been around since the early 1970s. It is used widely for cancers of the larynx and pharynx. It is done under general anesthesia using an endoscope inserted through the mouth. There are no external scars. A microscopic camera visualizes the tissues, and tiny instruments precisely perform the surgery. A CO2 laser beam is used for the cutting, which generates only a small amount of heat, so it doesn't cause a thermal injury to surrounding tissues but does improve hemostasis. Endoscopic thyroid and neck surgery can be performed for non-cancerous removal of thyroid tumors. An open incision is made in the neck, and either endoscopic or robotic techniques are used to perform minimally invasive thyroid surgery. It doesn't work for thyroid cancer. The operative field is highly magnified with the endoscope, so the surgery can be easily performed with precision, so the surgeon doesn't have to strain the eyes to see the small thyroid tumor. Robotic thyroidectomy can be used to remove certain types of thyroid tumors. There are several small incisions placed near the neck in discrete locations, so the patient doesn't have a visible neck scar. Modern technology is used that allows the surgeons to safely remove the thyroid tumors using robotic instruments that avoid hand tremor that might occur in a longer or more complex surgery. The thyroid gland is magnified by a factor of 10, so the tumor can be precisely removed without damaging normal thyroid tissue. The only tumors that can be used with robotic surgery are non-cancerous tumors that are less than 3 centimeters in size. Minimally invasive video-assisted thyroidectomy, or MEVAT, uses a small neck incision that is less than 1 inch in length. An endoscope is used to project the operative field on a screen with 10 times magnification, making it easier to work on this delicate and small organ. Endoscopic skull-based tumor surgery is a specialized type of surgery designed to reach areas deep within the patient's skull. Head and neck surgeons work alongside neurosurgeons to perform this type of procedure. Patients with cancerous and non-cancerous tumors of the base of the skull can be removed endoscopically with small incisions and precise delivery of surgical instruments. Doing this type of surgery does not eliminate the need for radiation therapy or chemotherapy, but allows for faster healing so these therapeutic modalities can be started sooner. Key Takeaways Patients with head and neck surgery have problems with anesthesia because both the surgeon and the anesthesiologist must work together in the same area. While both inhalational and intravenous anesthesia can be used, intravenous anesthesia is used to minimize nausea and vomiting after surgery. There are several techniques for intubation or the provision of an airway that don't interfere with the intraoperative field. Many head and neck surgeries are done as minimally invasive surgeries that involve less scarring, more precise surgical techniques, and faster recovery. Quiz Number 1. What is the main advantage of robotic thyroidectomy surgeries? A. There is less bleeding than endoscopic thyroidectomy. B. It uses smaller instruments than endoscopic thyroidectomy. C. It can be used to remove cancerous tumors. D. The incisions are discreetly placed so that there are no visible neck scars. Answer D. The main advantage of robotic thyroidectomy is that the incisions can be placed discreetly so there are no visible neck scars. It can't be used on cancerous thyroid tumors. Number 2. What is the main advantage of endoscopic skull-based tumor surgery? A. The surgeon can better visualize the surgical field when compared to conventional surgery. B. The surgery is shorter in duration when compared to conventional surgery. C. Radiation treatments and chemotherapy can be started sooner with this surgery when compared to conventional surgery. D. The surgeon doesn't need to learn any specialized techniques to do this kind of surgery. Answer C. Endoscopic skull-based tumor surgery is technically more difficult but allows for rapid recovery, so if radiation and chemotherapy are recommended, they can be started sooner when compared to conventional surgery. Number 3. What is the rate of ventilations in high-frequency jet ventilation? A. 12 breaths per minute. B. 25 breaths per minute. C. 250 breaths per minute. D. 500 breaths per minute. Answer C. In high-frequency jet ventilation, about 250 breaths per minute are given with small tidal volumes. Number 4. What is the main complication of jet ventilation in head and neck surgery? A. It doesn't allow for good visualization of the larynx. B. There is a risk for hypercapnia. C. Only inhalational anesthetics can be used. D. The patient is not likely to have a still surgical field. Answer B. Because jet ventilation involves the rapid ventilation of small volumes of oxygen, there is a risk of hypercapnia with this procedure. Number 5. Which anesthetic agent offers the least risk for postoperative nausea and vomiting? A. Propofol. B. Sevoflurane. C. Desflurane. D. Isoflurane. Answer A. Propofol involves an intravenous anesthesia, which decreases the risk of postoperative nausea and vomiting. Number 6. Why is it crucial to avoid nausea and vomiting after head and neck surgery? A. These patients cannot afford the fluid losses in vomiting frequently. B. It increases the pain associated with the surgery. C. It can cause hematoma formation and extra bleeding after surgery. D. It can cause the external incisions to break open. Answer C. The main reason why it is important to avoid nausea and vomiting in the postoperative phase is that it can cause hematoma formation and extra bleeding after head and neck surgery. Number 7. What is the main advantage of using jet ventilation in head and neck surgery? A. It is technically easy to do. B. It allows for intermittent apnea during surgery. C. It minimizes blood loss during surgery. D. It allows for a still surgical field. Answer D. The main advantage of jet ventilation in head and neck surgery is that it more easily allows for a still surgical field. Number 8. What is the main deciding factor in the amount of analgesia used in head and neck surgery? A. The goal is to avoid medications that cause hypotension during surgery. B. The choice of opiate must keep the patient from moving during surgery. C. Certain analgesics don't allow for the use of neuromuscular blocking agents. D. The choice of medication is based on the anticipated pain experienced after surgery. Answer D. The main choice of analgesic used in surgery depends on the anticipated pain the patient will experience after surgery. Number 9. Which type of surgeon most likely performs head and neck surgery? A. Oral and maxillofacial surgeons. B. General surgeons. C. Otologic surgeons. D. Neurosurgeons. Answer. A. The main type of surgeon that participates in head and neck surgery are oral and maxillofacial surgeons, although the other types of surgeons may sometimes play a role. Number 10. Why is controlled hypotension important in head and neck surgical procedures? A. It keeps the patient from moving around in surgery. B. It keeps the intracranial blood pressure lower. C. It decreases the amount of bleeding at the site. D. It allows for less anesthetic medication to be used. Answer. C. The main reason for having controlled hypotension in head and neck surgery is that it decreases the amount of bleeding at the surgical site.