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Major surgery for cancer includes laryngectomy, radical neck dissection, hemimandibulectomy, and radical sinus surgery. Anesthesia management was reviewed in detail by Morrison and coworkers,[94] McRae, [102] and Dougherty and Nguyen.[103] Joseph and colleagues[104] reviewed the complications of anesthesia for head and neck surgery.
These patients are often heavy users of alcohol and tobacco and have bronchitis, pulmonary emphysema, and cardiovascular disease. Weight loss, malnutrition, anemia, dehydration, and electrolyte imbalance can be significant. These patients may present difficult endotracheal intubation and airway management problems, as discussed later and in Chapter 42 .
The use of an inhaled anesthetic dilates the bronchi, depresses the airway reflexes, permits the use of high concentrations of oxygen, and may produce moderate hypotension (systolic blood pressure of 85 to 90 mm Hg). When a 10- to 15-degree head-up tilt is added, the resulting moderate hypotension may be sufficient to diminish blood loss. Induced hypotension is not without risk in debilitated patients and may be unnecessary and dangerous.[94] [105]
Remifentanil is a short-acting mu-opioid analgesic. The drug is very effective in controlling the hemodynamic response to intubation and stress responses during surgery.[106] [107] [108] These properties have led to its becoming a popular drug for many ear, nose, and throat procedures such as panendoscopy. Although many anesthetic techniques involving remifentanil have been described, two popular choices are as follows:
Manipulation of the carotid sinus may elicit a vagal reflex that causes bradycardia, hypotension, or even cardiac arrest. Trauma to the right stellate ganglion and cervical autonomic nervous system during right radical neck surgery can prolong the QT interval and may lower the threshold for ventricular fibrillation. [109] Severe tachyarrhythmia and cardiac arrest have been reported in these cases, especially in association with hypokalemia.
Open neck veins create the possibility of air emboli during head and neck surgery (see Chapter 53 ), but the incidence of air emboli during this type of surgery is low. An end-tidal CO2 monitor indicates a sudden decrease, and a precordial Doppler probe picks up the murmur of venous air embolism. Hypotension and arrhythmias are late signs of air emboli.[94] Treatment includes the following: increasing venous pressure through the use of positive-pressure ventilation or jugular vein compression; slight Trendelenburg, left lateral positioning; use of 100% oxygen; and if possible, aspiration of the air through a central venous catheter.
Postoperative considerations consist of care of the tracheostomy, use of humidified oxygen, and institution of chest physical therapy. A chest radiograph establishes the position of the tracheostomy tube and checks for pneumothorax, subcutaneous emphysema, and hematoma.
Changing a tracheotomy tube after a fresh tracheotomy can be dangerous but may be required because of a cuff leak or obstruction of the tube from secretions. The new tube may enter a false passage instead of the trachea. If the false passage is ventilated, the resulting subcutaneous emphysema soon removes all possibility of easily reestablishing the airway. Tissue support is lacking in a fresh tracheostomy. With removal of the tube, the tissues collapse and obscure the passage. Accordingly, the clinician should be familiar with precautions when dealing with a fresh tracheostomy tube, as follows.
For the first week or so, all tube changes should be carried out in the operating room by an experienced surgeon under good lighting with a full set of surgical instruments. An anesthesiologist should also be present in case oral intubation is needed. The patient should be preoxygenated. A fiberoptic bronchoscope may be useful in confirming tracheal placement of a tracheostomy tube before attempting positive-pressure ventilation.
Once the tracheotomy site has begun to mature, it is no longer necessary to carry out tube changes in the operating room. A full set of tracheotomy instruments, especially cricoid hooks, should still be available, however. Changing the tube over a tube changer may also be useful,[110] but this technique is not without potential problems.[111]
Complications of thyroid surgery include postoperative bleeding, airway-compressing hematoma, hypocalcemia, and recurrent laryngeal nerve dysfunction. [112] [113] The recurrent laryngeal nerve is at risk for injury during thyroid and parathyroid surgery, and such injury may result in vocal cord paralysis and airway obstruction with a 0.2% to 1.0% incidence of permanent injury.[104] Techniques such as electromyography or nerve action potential monitoring can be used to monitor recurrent laryngeal nerve function during surgery.[114] [115] [116] [117] Such methods are not in routine use in many centers. Another approach is use of the laryngeal mask airway during thyroid surgery to allow fiberoptic visualization of vocal cord movement immediately after surgery or to allow viewing of movement of the arytenoids in response to nerve stimulation.[118] [119]
Hypoparathyroidism with resulting hypocalcemia is another potential complication of thyroid surgery. The parathyroid glands produce parathyroid hormone, which increases serum calcium. Inadequate production of parathyroid hormone may be the result of trauma to the parathyroid glands, devascularization of the parathyroids, or removal of the glands. Patients who are hypocalcemic after thyroid surgery are initially asymptomatic, but carpopedal spasm, tetany, laryngospasm, circumoral paresthesias, mental status changes, seizures, QT prolongation, or cardiac arrest may develop later. Postoperative monitoring of ionized calcium levels in total-thyroidectomy patients is desirable. In addition, Chvostek's and Trousseau's signs may both be sought to confirm hypocalcemia. Chvostek's sign is facial contractions elicited by tapping the facial nerve in the preauricular area. Trousseau's sign is carpal spasm on inflation of a blood pressure cuff.
Septoplasty, polyp removal, and reduction of fractured nasal bones can be performed safely by using local anesthetics combined with sedation.[120] [121] [122] [123]
General anesthesia is usually preferred for procedures such as rhinoplasty, Caldwell-Luc operations, and endoscopic sinus surgery. In particular, entry into the intracranial space, blindness, and internal carotid artery damage may result if the patient moves during endoscopic sinus surgery.[124]
Blood present in the oropharynx at the time of extubation may lead to coughing or laryngospasm. Attempts at positive-pressure ventilation are complicated by concerns that tight application of a facemask over the patient's nose may cause damage. Bleeding can be reduced by using topically applied vasoconstrictive drugs, a head-up position of 15 to 20 degrees, and a mild degree of hypotension. Use of a throat pack intraoperatively will reduce the amount of blood entering the glottis. It may be helpful to extubate the patient while on the side and wide awake. Special mention should be made of blood collections that may occur at the back of the soft palate during and after nasal surgery. After extubation, clots may move from this site and fall into the glottis, thereby leading to complete airway obstruction. Even with direct laryngoscopy, these clots can be missed. Because the clot may be first found only at autopsy, it has been given the name coroner's clot.[125] Suctioning by both the nasal and oral routes will help reduce the incidence of this problem.
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