Anesthesiology

Microlaryngoscopy

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What the Anesthesiologist Should Know before the Operative Procedure

The goal of the procedure is to obtain visual exposure of the pharynx and larynx for surgical examination, diagnosis, or treatment. The surgical laryngoscope is different from the standard blade used in anesthesia airway management. The scope (Lindholm, Jackson, anterior commissure) effectively retracts soft tissue structures and is left in place via suspension against the chest or a Mayo stand for the duration of the procedure. The surgical laryngoscope also provides a conduit for passage of instruments such as an endoscope or a bronchoscope for evaluation of the tracheobronchial tree and esophagus for pathology or obstruction. For cancer screening, the procedure commonly involves "pan endoscopy." This entails microdirect laryngoscopy, bronchoscopy, and esophagoscopy.

Clinical indications for the procedure will inform preoperative assessment and anesthetic planning.

Category 1: Diagnostic

a) Oropharyngeal or laryngeal cancer, b) hoarseness/dysphonia, c) dysphagia, d) larygneal trauma, or e) stridor

Category 2: Therapeutic

a) Vocal cord collagen/fat injection, b) excisional biopsy or ablation of pharyngeal, glottic lesion, c) tracheal dilation, d) esophageal dilation, or e) clot evacuation

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Risk is typically minimal for a modest delay (days) of most cases for critical medical issues. This excludes emergent cases as described below in which even a short delay of hours is typically untenable.

Emergent: Patients for emergent microlaryngoscopy should be assumed to have a difficult airway unless otherwise demonstrated. Examples of emergent microlaryngoscopy indications include laryngeal trauma, fracture, or dislocation and acute airway obstruction for vocal cord dysfunction, airway hematoma/bleeding, or edema. Any delay in management could be life threatening.

Urgent: Diagnostic and therapeutic procedures for malignant lesions should be performed without unnecessary delay, but appropriate diagnostic tests and therapeutic interventions can be considered within a reasonable time-frame.

Elective: Procedures to treat chronic conditions (e.g., collagen injection for vocal cord dysfunction) are elective and all appropriate preoperative optimization should be completed prior to surgery.

2. Preoperative evaluation

Malignancy of the head and neck is a primary indication for the procedure. Patients may be treated with radiation prior to the procedure. Patients may present for repeat procedure after a major head and neck operation. In both situations, information from a prior anesthetic record regarding the airway and standard airway indications may not be relevant to the present circumstance and a new primary assessment and discussion with the previous operative surgeon (if possible) are imperative.

Medically unstable conditions warranting further evaluation include peripheral vascular disease (including carotid stenosis), acute coronary syndrome, uncompensated congestive heart failure, significant arrhythmia such as rate uncontrolled atrial fibrillation, pneumonia, severe exacerbation of asthma, or obstructive pulmonary disease. Delaying surgery may be indicated if significant metabolic disease can be treated and optimized prior to surgery without delay that would adversely impact prognosis. Examples include electrolyte abnormality, leukopenia secondary to recent chemotherapy, and hypo/hypervolemia.

3. What are the implications of co-existing disease on perioperative care?

b. Cardiovascular system

Acute/unstable conditions: Should not be performed in patients with hemodynamic instability save for the exceptional circumstance of acute airway obstruction or laryngeal trauma.

Baseline coronary artery disease or cardiac dysfunction - Goals of management: Use opioids and esmolol to blunt heart rate responses to laryngoscopy; maintain blood pressure within 10% of baseline.

c. Pulmonary

COPD: Common in this patient population. Continue oral steroids on day of surgery if chronic use. No role for stress-dose steroids in majority of patients. Use inhaler medications on the day of surgery. Consider avoiding high-frequency jet ventilation if significant bullous disease, home oxygen use, or other markers of severe disease and chronic hypoxemia. Consider delay of surgery if pulmonary function is significantly worsened from baseline or signs and symptoms of acute respiratory infection are present.

Reactive airway disease (Asthma): Use inhalers on the day of surgery. Patients with fixed or dynamic airway obstruction due to vocal cord dysfunction or tracheal stenosis may be initially and incorrectly diagnosed with reactive airway disease. Signs and symptoms of reactive airway disease often overlap and care should be taken not to postpone necessary surgical assessment and intervention in anticipation of a resolution of symptoms.

d. Renal-GI:

N/A

e. Neurologic:

Acute issues: Procedure involves neck extension, manipulation of the larynx, and potential pressure on cervical spine. A nonemergent procedure should not be performed in a patient with an unstable cervical spine. The use of sandbags for neck stabilization may be considered in emergent cases. In most cases, a C-collar with not permit adequate access to the airway for laryngeal exposure.

Chronic disease: Patients with degenerative or autoimmune joint disease (e.g., rheumatoid arthritis) involving the cervical spine should be assessed prior to the procedure.

f. Endocrine:

Endocrine: Rarely an issue in this patient population,

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Patients with head and neck cancer have frequently been treated with radiation therapy. The scarring caused by the radiation may decrease laryngeal mobility and may also produce radiation necrosis of the bone and temporomandibular joint and soft tissue scarring. The overall result is decreased mobility of structures that are manipulated during laryngoscopy to achieve an adequate view of the glottis.

4. What are the patient's medications and how should they be managed in the perioperative period?

In most elective cases, discontinue medications that may interfere with coagulation. Even minor bleeding in the airway can have functional significance in the glottis. These include aspirin, NSAIDs, heparin, low molecular weight heparin, clopidogrel, warfarin, garlic, ginseng, and gingko. The risk-benefit ratio of discontinuation of antiplatelet medications should be reviewed with the surgeon and appropriate consultants for patients with coronary stents.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

See anticoagulants above.

i. What should be recommended with regard to continuation of medications taken chronically?

i. Continue all medications for blood pressure and heart rate control.

ii. Continue all pulmonary medications and especially medications for reactive airway disease such as beta-agonist inhalers, anticholinergic inhalers, and inhaled or oral corticosteroids.

iii. Continue renal medications.

iv. Continue neurologic medications.

v. Continue psychiatric medications. Avoid indirect sympathomimetic agents (e.g., ephedrine) in patients taking MAOIs or TCAs.

j. How To modify care for patients with known allergies -

N/A

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products. See core chapter in this text on anaphylaxis.

l. Does the patient have any antibiotic allergies- [Tier 2- Common antibiotic allergies and alternative antibiotics]

Prophylactic antibiotics not routinely used.

Clindamycin (600 mg) is the most commonly used alternative in patients with cephalosporin allergy.

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia (MH)

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents:

  1. Proposed general anesthetic plan:

  2. Ensure MH cart available: [MH protocol]

  3. Family history or risk factors for MH:

5. What laboratory tests should be obtained and has everything been reviewed?

There are no essential laboratory tests necessary for routine microlaryngoscopy unless the patient has a history of coagulopathy or liver dysfunction in which case, platelet count, PTT, and PT/INR should be checked prior to surgery. Potassium should be checked in patients taking diuretic medications, ARB, or ACE inhibitor antihypertensives and patients with renal dysfunction. Clinically significant bleeding is exceptionally rare in patients undergoing this procedure with the exception of laser treatment of lesions associated with hereditary hemorrhagic telangiectasia. Hemoglobin need only be tested in patients with suspicion of acute anemia. A type and screen is needed in rare cases.

Hemoglobin levels:

See above.

Electrolytes:

See above.

Coagulation panel:

See above.

Imaging:

Preoperative cardiac or vascular imaging seldom indicated unless high clinical suspicion of cardiac or carotid vascular disease. MRI or CT of the larynx helps to characterize the anatomic location and extent of the lesion but rarely impacts clinical management.

Other tests:

ECG in patients with history of hypertension, cardiovascular disease, or age over 50, Chest x-ray only if acute respiratory infection or pulmonary edema/effusion is suspected.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

General anesthesia is the preferred approach for the vast majority of cases. Monitored anesthesia care with targeted blocks and local anesthetic applied to the airway can be considered in selected circumstances. For example: (1) history of patient reaction to general anesthesia (e.g., severe postoperative cognitive dysfunction), (2) avoidance of apnea and intubation in a patient with a tenuous airway, or (3) strong patient preference.

Neuraxial

None. Cervical epidural has been reported in a single case series for tracheal resection but this would be a highly exceptional choice reserved for peculiar indications.

Peripheral nerve block

Benefits: Maintenance of spontaneous ventilation, maintain ability to follow commands, decrease hemodynamic insult from induction of general anesthesia.

Drawbacks: Patient will be awake for a highly stimulating procedure in an unusual position; only procedures of limited invasiveness and duration are feasible; cannot protect airway from blood and secretions generated during the procedure; consumes considerable time and requires experienced provider and equipment for block placement; coughing during the procedure can result in injury from the suspension laryngoscope.

Issues: (1) Placement of needles in the airway for blocks can cause bleeding that may precipitate airway obstruction or impair surgical visualization. This is especially true if abnormal tissue (i.e., tumor) is in the area of the nerve to be blocked; (2) local anesthetic toxicity can occur when large doses are used; (3) microdirect laryngoscopy under local anesthesia is a lost art. Since seldom done, this requires careful planning and discussion by the perioperative team.

One approach consists of nebulized lidocaine (2%-4%, 8 L/min flow) followed by targeted blocks of the superior laryngeal and glossopharyngeal nerves. Diffuse atomization of lidocaine (2%-4%) to the posterior oropharynx with nebulization may substitute for discreet nerve blocks. Supplemental local infiltration may be necessary for areas such as the lip and gingiva against which the laryngoscope rests. Additional lidocaine can be delivered into the airway or directly onto the vocal cords once the laryngoscopic view has been obtained.

Adjuvant sedation (see MAC below) will be helpful but must be selected and titrated so as to avoid airway compromise until the laryngoscopic view has been confirmed.

b. General Anesthesia

Advantages of general anesthesia include immobile patient, profound cough suppression, relaxation of soft tissues that may ease exposure, and ability to perform invasive resection and laser ablation; can send frozen sections.

Mask ventilation is frequently challenging and visualization of the glottic opening for intubation can be difficult in some patients with standard MacIntosh or Miller blades; prior surgical resection or previous radiation therapy decreases mobility of structures.

The video laryngoscope (e.g., Glidscope) may be helpful to visualize the glottis and avoid insult to friable lesions in patients with airway masses or postradiation changes.

Discussion of airway with surgeon must take place in all cases. The development of an airway team familiar with the techniques and experience of the operating surgeon may optimize management.

Surgeon should be immediately available at the time of induction for most cases.

Some patients have had prior tracheostomy or laryngectomy. In most cases jet ventilation can be performed via the in-site tracheostomy tube or the tracheostomy tube is removed and replaced with a wire-reinforced endotracheal tube; the reinforced tube should not be larger in diameter than the in situ tracheostomy tube; patients should be counseled that there is a small possibility that they may recall the replacement of the tracheostomy tube at the end of the case as it is prudent to wait for the return of spontaneous ventilation prior to exchange of a cuffed endotracheal tube for an uncuffed tracheostomy tube.

Options for airway management are varied. Assume that periodic interruption of ventilation will be necessary. Primary rational for selection of airway type is the nature of the lesion and the surgical plan. Difficult of intubation and ease of obtaining surgical laryngoscopic view are other important issues. Endotracheal intubation with a small-bore tube (5.0, 6.0) is one option. Larger tubes typically obscure the surgical view and access. MLT tubes maintain length despite narrow bore and are often used but are too long to be placed over the lighted surgical stylet. A laser tube should be used for laser cases. Repeated extubation/intubation by the surgeon under suspension laryngoscopy with intermittent apnea may be necessary if endotracheal intubation is used.

In rare circumstances surgical visualization cannot be achieved. In some cases the planned procedure (diagnostic biopsy, excisional biopsy) can be performed with a flexible bronchoscope via an LMA or a videolaryngoscope may assist visualization.

High-frequency jet ventilation is used with great success. Ventilation can be accomplished through a metal or airway exchange catheter positioned through the laryngoscope, via a transtracheal catheter placed through the cricothyroid membrane, via a Luer-Lok elbow fitting attached to an endotracheal tube, tracheostomy tube, or LMA, or via specialized larynoscope with a ventilation port.

Use of automated jet ventilators (e.g., Accutronic Monsoon) is generally safer than manual jet devices. Use allows pressure limited delivery with automatic shutoff for high pressures. Devices capable of delivering a humidified jet stream should be used when extended jet ventilation is planned to avoid airway desiccation, decreased mucociliary function, and tracheomucositis.

Limitations of jet ventilation include the inability to measure minute ventilation or continuous capnometry and the risk of barotrauma.

Position and type of jet conduit and driving pressure are primary variables for efficacy. Pressures of 15-30 psi (1-2 atm) are typically safe and adequate for most patients combined when used with inspiratory time of 30%-50% frequency of 100-150 breaths per minute. Supraglottic ventilation is more efficacious than is subglottic.

Maintenance of an open pathway for exhaled air is an absolute requirement for safe use of jet ventilation. Particular vigilance for the possibility of lung hyperinflation should be observed in patient with significant stenosis and the jet catheter should not be positioned distal to the narrowing. Patients with significant lung disease, baseline hypoxemia, and morbid obesity may be more likely to fail a trial of jet ventilation but should not be automatically excluded.

Delivery of volatile agents to maintain a consistent depth of anesthesia is challenging. Volatile agents alone at typical doses are less effective at suppressing airway reflexes that intravenous/opioid combinations. Higher (1.5-2 MAC) doses may be effective but will delay emergence. Use of pharmacologic muscle relaxation is more likely to be necessary with volatile agents. Use of volatile agents may be optimal if general anesthesia with maintenance of spontaneous ventilation is desired. Escape of volatile agents into the operating room may be deleterious to staff and the operating room environment.

Total intravenous anesthesia with propofol and remifentanil is very effective in blunting airway reflexes, minimizing autonomic responsiveness, and achieving immobility. Muscle relaxation can typically be avoided. Higher remifentanil doses allow a lower propofol effect-site concentration due to anesthetic synergy, thereby minimizing wake-up time.

Succinylcholine is the muscle relaxant of choice when required. The duration of action of the widely available nondepolarizing muscle relaxants invariably outlasts the length of the procedure.

In high-risk patients (i.e., those with a history of awareness, alcohol, chronic opioid, benzodiazepine use, or physiologically impaired), use of a processed EEG monitor may be considered to guide anesthetic dosing.

Discussion with the surgeon should be undertaken if use of laser is planned. Intubation with a laser tube or jet ventilation should be planned. Regardless of modality, inspired fraction of oxygen should be reduced as low as tolerated during laser surgery to reduce the risk of airway fire. Inspired fraction of oxygen should be confirmed by direct communication between surgeon and anesthesiologist prior to each period of laser application. Nitrous oxide is combustible and should also be avoided during laser application. Providers should be versed in management of airway fires.

c. Monitored Anesthesia Care

a. See peripheral nerve block.

b. Any level of sedation risks obstruction in a tenuous airway.

c. Amnesia may be less reliable when selective sedation approaches are used. Amnesia is not a primary goal when considering the consequences of unintentional oversedation and airway compromise.

d. Approaches to sedation that minimize this risk and allow targeted, gradual are preferred to define bolus administration (i.e., a "standard sedation").

e. Dexmedetomidine, a selective alpha-2-adrenoreceptor agonist, provides reliable anxiolysis and cooperative hypnosis when delivered as an infusion of 0.3-1.0 mcg/kg/h after a loading dose of 0.5-1 mcg/kg over 10 minutes.

f. Remifentanil, a potent mu-opioid selective agonists, can be used effectively to blunt coughing, autonomic responsiveness, and breakthrough pain. Remifentanil carries significant risk of respiratory depression. This can be diminished significantly by slow titration to allow carbon dioxide to gradually accumulate as minute ventilation slows. An infusion, titrated gradually to effect, of 0.02-0.2 mcg/kg/min is typically adequate. A bolus of 0.2-0.5 mcg/kg can be used to more rapidly achieve target effect-site concentrations. Continuous capnometry should be used throughout the procedure.

g. The clinical effects of coadministration of midazolam or propofol with remifentanil for sedation are unpredictable. Oversedation or apnea can occur.

6. What is the author's preferred method of anesthesia technique and why?

What prophylactic antibiotics should be administered?

Not typically indicated for this procedure.

What do I need to know about the surgical technique to optimize my anesthetic care?

Anticipate rapid changes in levels of stimulus. The placement of the laryngoscope blade is highly stimulating. Recognize that if suspension of the patient is accomplished via attachment of the scope to the Mayo stand bed height should not be changed unless requested by the surgeon as this will displace the scope. This includes the inability to use head up or reverse Trendelenburg position to improve ventilatory dynamics. Procedure is typically very short (10-15 minutes) but can be longer if frozen sections are sent. The final step of the procedure is usually application of pledgets soaked with vasocontrictors to the surgical airway to confirm adequate hemostasis. In high-volume centers, anesthesia efficiency will be critical to surgical flow. Consideration should be given to induction in the rotated bed position (rotated 90/180 degrees), tucking of arms as needed, and placement of the patient head on a foam ring prior to induction.

What can I do intraoperatively to assist the surgeon and optimize patient care?

Surgeon may abruptly request transient apnea, cessation of jet ventilation, intubation, airway maneuver, or alternate size of endotracheal tube. A key to successful anesthetic management is constant communication with the surgeon including thorough preoperative discussion of airway management.

What are the most common intraoperative complications and how can they be avoided/treated?

1. Hypoxemia: In most patients a saturation of >90% is adequate for the brief period required to obtain the necessary biopsy, ablation, or assessment. Options to improve oxygenation include (a) increase jet ventilation driving pressure if using HFJV, (b) ask surgeon to introduce pledget distal to jet catheter to generate mild PEEP for re-recruitment, (c) convert from HFJV to positive pressure ventilation via endotracheal tube and deliver recruitment maneuvers and PEEP, (d) abandon procedure if severe.

2. Inadequate glottic exposure: Deepen anesthesia or add muscle relaxant, consider LMA, consider videolaryngoscopy.

3. Inadequate depth of anesthesia: deepen anesthesia.

Complications

Cardiac: None unique to microlaryngoscopy.

Pulmonary: Pneumothorax if using jet ventilation due to lung overinflation with barotrauma. Pediatric patients and those with severe tracheal stenosis, advanced bullous lung disease, may be more susceptible to these complications.

Neurologic: None unique to microlaryngoscopy.

a. Neurologic

b. If the patient is intubated, are there any special criteria for extubation?

Due to the nature of the surgery and the intrinsic airway pathology a patient should be awake with spontaneous ventilation prior to extubation. Deep extubation is generally not performed in this patient population. When jet ventilation is delivered through the surgical laryngoscope, ventilation should be stopped upon removal of the laryngoscope. If mask ventilation was difficult during induction, consideration should be given to intubation by the surgeon prior to the end of the case to allow ventilation throughout emergence. Coughing and bucking during emergence and vigorous suctioning near the surgical site can trigger bleeding and should be minimized. Head-up position during emergence may optimize respiratory dynamics. An endotracheal tube should not be removed and replaced with an uncuffed larygnectomy or tracheostomy tube until resumption of spontaneous ventilation has been confirmed unless the ability to delivery positive pressure ventilation via the uncuffed airway was previously confirmed.

c. Postoperative management

  1. Minimal postoperative analgesic requirements.

  2. Intravenous acetaminophen may be considered for adjunctive analgesia.

  3. Most cases are minimally invasive and performed as outpatients.

  4. Patients who undergo more invasive resection or who have significant obstructive sleep apnea (OSA) should have an extended PACU stay and, if admitted, should be triaged to a monitored bed setting with consideration for continuous pulse oximetry. Use of noninvasive positive pressure ventilation (CPAP/BiPAP) in the PACU and floor is recommended for patients with OSA. This modality should be used with caution in patients who have undergone surgical resection in the airway. Discussion with the surgeon should precede initiation of NIPPV.

  5. Bleeding is the most common perioperative complication. Fastidious hemostasis by the surgical team, typically with Afrin-soaked pledgets and cautery at the end of surgery, is the most reliable method of treatment.

What's the Evidence?

Biro, P. "Jet ventilation for procedures on the airway". Anesthesiol. Clin . vol. 28. 2010. pp. 397-409.

(Current review of the application of jet ventilation in airway surgery including basic physiology, relative risks, and methodology.

Ehran, E, Ugur, G, Gunusen, I, Alper, I, Havas, T. "Propofol – not thiopental or etomidate -- with remifentanil provides adequate intubating conditions in the absence of neuromuscular blockade". Can J Anesth . vol. 124. 2003. pp. 641-5.

(Example of a clinical study demonstrating the relatively unique utility of the combination propofol-remifentanil combinations for intubation without muscle relaxants.)

Klussman, JP, Knoedgen, R, Wittenkindt, C, Damm, M, Eckel, HE. "Complications of suspension laryngoscopy". Ann Otol Rhinol Laryngol . vol. 111. 2002. pp. 972-6.

(Reviews technical and surgical issues of relevance to the anesthesiologist.)

Cook, TM, Alexander, R. "Major complications during anaesthesia for elective laryngeal surgery in the UK: a national survey of the use of high pressure ventilation". Br J Anaesth . vol. 101. 2008. pp. 266-72.

(Reviews major clinical experience with jet ventilation for laryngeal surgery.)

Antila, HM, Illman, HS, Hurme, S, Grénman, R. "Tubeless anesthesia with sevoflurane and propofol in adult laryngeal surgery". Eur Arch Otolaryngol . vol. 268. 2011. pp. 93-9.

(Describes the advantages and limitations of an alternative to total intravenous anesthesia that uses insufflated sevoflurane with spontaneous ventilation.)
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