Endocrine diseases and the airway

Endocrine Diseases and the Airway P. Allan Klock, Jr, and Andranik Ovassapian RWAY MANAGEMENT is the cornerstone of safe anesthesia delivery. Endocrine disorders such as diabetes mellitus, acromegaly, obesity, a n d thyroid disorders including goiter and malignancies may adversely affect the airway and increase the risk of difficult intubation. Given the thorough review of the pathophysiology of various endocrine diseases in other parts of this monograph, this article will focus solely on how these disorders affect the airway and its management.

DIABETES MELLITUS The high incidence of difficult rigid laryngoscopy in patients with diabetes mellitus has been reported] The diabetic stiff joint syndrome characterized by short stature, joint rigidity, and tight waxy skin is a major contributing factor to difficult intubation) The stiff joint syndrome results from glycosylation of tissue proteins caused by long-standing hyperglycemia, which causes crosslinking of collagen. The incidence of difficult intubation is reported to be as high as 30% in long-standing diabetics. 2"3 Patients with diabetic stiff joint syndrome have difficulty in approximating their palms and cannot bend their fingers backward. When the cervical spine is involved, atlanto occipital joint motion and head extension are restricted, making rigid laryngoscopy and tracheal intubation quite difficult. Joint stiffness of the hand can be evaluated with the palm test. The palm of the hand is placed against a flat surface to see how much of the patient' s palm makes contact with the flat surface. 4 The correlation of the degree of difficult intubation with joint stiffness judged by the palm test was reported by Reissell. 5

risk to develop upper airway obstruction during anesthesia. Positive pressure ventilation by face mask is more difficult in these patients because of decreased chest wall compliance. Morbidly obese patients are also at increased risk of regurgitation and aspiration both because of increased intraabdominal pressure and the high incidence of patients with gastric fluid volume of more than 25 mL and gastric fluid pH of less than 2.5. 7,8 All these risk factors make airway management difficult and more prone to major complications in the morbidly obese. Buckley et al9 reported a 13% incidence of difficult intubation in morbidly obese patients, although Bond ~~found no relationship between obesity and difficult intubation. Should a surgical airway become necessary, finding the landmarks and accessing the airway quickly could be extremely difficult. Weight alone may not be as important as its distribution. Patients with massive weight in their lower abdomen and hip region may behave differently than patients with an obese upper body and neck area. A short, thick, immobile neck produced by cervical spine fat pads will interfere with rigid laryngoscopy, irrespective of the patient's total body weight] ~ In consideration of all of the factors discussed, securing the airway in morbidly obese patients with a short, thick neck and limited neck extension may be safer if performed before induction of general anesthesia, t~ The fiberoptic bronchoscope has made awake intubation a relatively easy, highly successful technique. Mclntyre's 12 statement in 1968, "The anatomical structure of the obese patient is an intimidating sight in the operating room" remains equally valid today.

ACROMEGALY OBESITY Morbid obesity is associated with a number of physiologic changes that increase the risk of anesthesia and surgery. Obese patients have increased intraabdominal pressure, decreased functional residual capacity, and decreased total lung capacity. 6 The obese patient with a large tongue and redundant folds of oropharyngeal tissue is at increased

Although several serious conditions may arise from hypothalamic-pituitary dysfunction, only exFrom the University of Chicago, Chicago, IL. Reprints not available. Copyright 2002, Elsevier Science (USA). All rights reserved. 0277-0326/02/2101-0002535.00/0 doi: l O.l O53/sane.2002.32031

Seminars in Anesthesia, Perioperative Medicine and Pain, Vol 21, No 1 (March), 2002: pp 3-7

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cessive growth hormone has a significant effect on the airway. Acromegaly caused by excessive growth hormone secretion after closure of the epiphysial growth plates may have the most significant impact on the airway of any endocrine disease. Patients with acromegaly have coarsening of the facial features caused by progressive growth of the facial bones and cartilaginous structures. Airway difficulty and tongue enlargement are common in acromegalic patients. 13 Mask ventilation may be difficult because of redundant folds of tissue in the oro- and hypopharynx, enlargement of the nose, or tongue and laryngeal stenosis. 13'14 However, not all studies show difficult mask ventilation. 15,16 Direct laryngoscopy is difficult in approximately 26% of patients with acromegaly because of an enlarged tongue and mandible. ~7 Proper positioning for direct laryngoscopy may also be impaired by poor neck mobility. The distance from the incisors to the laryngeal opening may be longer than expected because of the enlarged mandible. In addition, there may be sub-clinical stenosis below the vocal cords, necessitating the use of a smaller than anticipated endotracheal tube. TM Fiberoptic intubation has been successful in a number of series of acromegalic patients. 14,.7,19 With proper topical anesthesia and carefully titrated sedation, the airway can be safely secured while allowing the patient to breathe spontaneously and maintain normal airway architecture. Excess growth hormone before closure of epiphysial growth plates results in gigantism. In these patients, an extra-large laryngoscope blade, longercut endotracheal tube, and extra-large face mask should be at hand before induction of anesthesia.

THYROID TUMOR AND GOITER Any patient presenting for thyroid or parathyroid surgery should have a careful airway examination. The character of the voice should be noted, and the patient should be asked to cough. Compression or traction of the recurrent laryngeal nerve may lead to preoperative vocal cord dysfunction. Postoperative nerve dysfunction caused by transsection will be permanent, whereas transient dysfunction may be caused by a neurapraxia from surgical manipulation. Unilateral recurrent laryngeal nerve dysfunction will prevent the ipsilateral vocal cord from adducting appropriately and obtaining the proper level of tension. This will lead to

a change in voice quality and will prevent the patient from being able to cough properly. Although the voice change is mostly a nuisance, impaired pulmonary toilet caused by a weak cough can be serious in a patient with chronic bronchitis or other pulmonary compromise. Bilateral recurrent laryngeal nerve dysfunction is a medical emergency because the patient is unable to abduct the cords properly. Because of the venturi effect, the cords are drawn toward the midline during inspiration. This leads to airway obstruction and inspiratory stridor requiring emergent reintubation or placement of a surgical airway such as a tracheostomy or cricothyrotomy. Goiters are usually detected in patients with hyperthyroidism. Most goiters in the United States are relatively small and have little clinical significance. Occasionally, a large, long-standing goiter may cause tracheomalacia that may be problematic during anesthetic induction, emergence, and recovery. Patients presenting with a large goiter may be best treated with fiberoptic intubation under topical anesthesia and sedation. This allows the patient to maintain normal respiratory mechanics until the endotracheal tube can be passed beyond the diseased part of the airway. Fiberoptic intubation also allows inspection of the vocal cords and the subglottic airway, providing useful information for intra- and postoperative care. Extrinsic compression of the trachea may reduce its internal diameter. It may be helpful to have a variety of small endotracheal tubes available. Finally, if significant tracheomalacia is discovered, the patient should be extubated wide awake while breathing spontaneously. A goiter may also have a significant retrotracheal component. This may be difficult to detect on physical examination. The retrotracheal tissue forces the trachea anteriorly, making direct laryngoscopy difficult. Fiberoptic intubation may also prove challenging because the interarytenoid band is lifted so far anterior to the posterior pharyngeal wall that passage of the fiberoptic bronchoscope through the vocal cords during an oral intubation is difficult. The authors have experience with one case of retrotracheal goiter in which a fiberoptic intubation via a nasal approach was successful; a prior attempt via the oral route had failed. Goiters may be asymmetric, pushing the larynx laterally. Fiberoptic or direct laryngoscopy may be facilitated by having an assistant apply gentle pressure

ENDOCRINE DISEASESAND THE AIRWAY over the thyroid cartilage (or overlying goiter) to direct the laryngeal opening toward the midline. Some patients have a retrosternal component of their goiter. The patient should be queried for symptoms of positional dyspnea, particularly associated with the supine position. A retrosternal goiter may be palpated by placing one's fingers over the trachea just above the sternal notch. The patient is then instructed to swallow. This will cause the trachea to move in a cephalad direction, moving the goiter under the examiner's fingers. Most serious disorders that affect the airway will be detected with a thorough history and physical examination. Many patients will have a preoperative computed tomography (CT) scan to detect the extent of the goiter or the extent of local spread of a malignancy. Review of the CT scan to evaluate the extent of airway involvement will aid the anesthesiologist in formulating an appropriate airway management plan.

THYROIDECTOMY AND THE LARYNGEAL MASK AIRWAY Direct visualization of vocal cord movement with recurrent laryngeal nerve stimulation was suggested by Riddell 2~ in 1970 to prevent bilateral recurrent nerve palsy during thyroid surgery. The available anesthetic and airway management techniques would not allow observation of vocal cord movement during general anesthesia. The laryngeal mask airway (LMA) combined with fiberoptic bronchoscopy provides the opportunity for continuous observation of the vocal cords during surgery without interfering with anesthesia and ventilation. The tip of the fiberscope is positioned just above or between the two epiglottic bars of the LMA, allowing good visualization of the vocal cords. Stimulation of the recurrent laryngeal nerve causes movement of the vocal cords when innervation is undisturbed. Use of the LMA with the fiberoptic bronchoscope in thyroid surgery was first reported in 1991. 21'22 Hobbiger and associates 23 studied the role of the LMA in thyroid and parathyroid surgery in 97 patients. In 50% of the patients, electrical stimulation of the recurrent laryngeal nerve was combined with visual observation of vocal cord movement through the fiberoptic bronchoscope. Stimulation of recurrent laryngeal nerve was necessary in 10% of patients to avoid nerve damage during difficult surgical dissection. In another 40%

5 of patients, stimulation of the nerve was used to confirm integrity of the nerve or for teaching purposes. Seven patients required postoperative intubation, two of which were unplanned. 23 Concerns about LMA use in thyroidectomy include difficulties in placement when a large thyroid mass has distorted the upper airway anatomy. 24 The LMA may be displaced by surgical manipulation and will not support the tracheal airway in cases of tracheomalacia. Fiberoptic observation of the trachea after completion of thyroid resection was helpful in identifying one patient with tracheomalacia in a series of 6 patients at high risk of developing tracheomalacia. 25 With this application, unnecessary tracheostomy was avoided in the remaining five patients. The failure rate of the LMA for thyroidectomy has been reported between 7% to 15%. 22,23 If airway maintenance becomes a problem during thyroidectomy using the LMA, the trachea may be intubated through the LMA with a 6-mm endotracheal tube. The exact role of the LMA in thyroid surgery is not established yet, and more experience and clinical studies are needed. However, the value of the LMA in assisting fiberoptic evaluation of the entire airway during the perioperative period and examination of vocal cord function after head and neck surgery is well established.

PARATHYROID DYSFUNCTION Hyperparathyroidism and its accompanying hypercalcemia has little effect on the airway. In contrast, hypoparathyroidism after parathyroidectomy resulting in hypocalcemia can produce life-threatening seizures, laryngeal strider, and laryngeal spasm. These complications may be preceded by distal paresthesias and muscle spasms or tetany. Trousseau's sign (carpopedal tetany after application of a tourniquet to an extremity) or Chvostek's sign (contracture of the facial muscles caused by tapping of the facial nerve at the angle of the jaw) usually precede the appearance of airway complications of hypocalcemia and can provide early warning of impending airway difficulty. If the patient has adequate oxygenation and ventilation, laryngeal muscle dysfunction caused by hypocalcemia may be treated with intravenous 10% calcium gluconate at a rate of 10 mL/min for 1 to 2 minutes. 26 The patient will requia'e emergent intubation or placement of a surgical airway if improvement is not immediate or if oxygenation is

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inadequate. Muscle relaxants will be required to allow adequate vocal cord abduction if oral or nasal intubation is planned.

COMPLICATIONS OF THYROID OR PARATHYROID SURGERY The patient is at risk for 3 special postoperative complications after surgery on the neck, thyroid, or parathyroid glands. Removal of too much parathyroid tissue may result in unintentional hypocalcemia. Although the half-life of parathyroid hormone is only 20 minutes, the nadir in serum calcium usually occurs 24 to 36 hours after surgery. 27 Treatment for significant hypocalcemia was outlined previously. Secondly, the patient may suffer from unilateral or bilateral recurrent laryngeal nerve injury. As stated in the thyroid section, unilateral injury usually is not immediately life threatening, whereas bilateral nerve injury will require emergent re-intubation or placement of a surgical airway. The third complication that is specific to neck surgery is the formation of a hematoma that can compromise the airway. The skin overlying the neck is relatively loose and elastic so a subcutaneous hematoma by itself usually has little effect on the airway. In contrast, the strap muscles in the neck are less distensible so a hematoma deep to the strap muscles can significantly compromise the airway. The function of surgical drains should be assessed quickly, and suction should be applied if possible. If the patient's condition does not improve quickly, the sutures closing the strap muscles should be opened immediately to evacuate the hematoma. This usually results in immediate release of airway obstruction. The surgical incision can be re-opened at the bedside. It is important to recognize that the sutures in the skin and the underlying strap muscles must be cut to evacuate the hematoma compressing the airway. If airway obstruction continues because of tissue edema, the trachea should be reintubated.

KEYS TO SUCCESS The patient with endocrine disease presents the anesthesiologist with a number of challenges. A thorough history and careful examination will provide warning of many potential pitfalls in airway management. The CT scan of the neck and/or chest should be reviewed before induction of anesthesia

because it may show difficulties not apparent on physical examination. Awake fiberoptic intubation is the technique of choice in several clinical situations. It will allow the anesthesiologist and surgeon to diagnose preexisting vocal cord dysfunction, extrinsic tracheal compression, or tracheal deviation. Of course, the fiberscope will facilitate intubation in a number of patients who may be difficult to intubate with direct laryngoscopy. Given that goiters and acromegaly may result in subglottic stenosis, having smaller tubes available may aid in safe intubation. Proper preparation should allow the anesthesiologist to develop and execute an anesthetic plan that is sate and comfortable for the patient.

REFERENCES 1. Eleborg L, Norberg AA: Are diabetic patients difficult to intubate? Acta Anaesthesiol Scand 32:508, 1988 (letter) 2. Salzarulo HH, Taylor LA: Diabetic "stiff joint syndrome" as a cause of difficult endotracheal intubafion. Anesthesiology 64:366-368, 1986 3, Hogan K, Rusy D, Springman SR: Difficult laryngoscopy and diabetes mellitus. Anesth Analg 67:1162-1165, 1988 4. Grgic A, Rosenbloom AL, Weber FT, et al: Joint contracture in childhood diabetes. N Eng J Med 292:372, 1975 5. Reissell E: Predictability of difficult laryngoscopy in patients with long-term diabetes mellitus. Anaesthesia 45:10241027, 1990 6. Biting MS, Lewis MI, Liu JI, et al: Pulmonary physiologic changes of morbid obesity. Am J Med Sci 318:293-297, 1999 7. Vaughan RW, Bauer S, Wise L: Volume and pH of gastric juice in obese patients. Anesthesiology 43:686-689, 1975 8. Kallar SK, Everett LL: Potential risks and preventive measures for pulmonary aspiration: New concepts in preoperative fasting. Anesth Analg 77:171-182, 1993 9. Buckley FP, Robinson NB, Simonowitz DA, et al: Anaesthesia in the morbidly obese. A comparison of anaesthetic and analgesic regimes for upper abdominal surgery. Anaesthesia 38:840-851, 1983 10. Bond A: Obesity and difficult intubation. Anaesth Intensive Care 21:828-830, 1993 11. Ovassapian A: The difficult airway, in Ovassapian A (ed): Fiberoptic endoscopy and the difficult airway. Philadelphia, Lippincott-Raven, 1996, pp 185-199 12. McIntyre JWR: Problems for the anaesthetist in the care of the obese patient. Can J Anaesth 15:317-324, 1968 13. Seidman PA, Kolfke WA, Policare R, et al: Anaesthetic complications of acromegaly. Br J Anaesth 84:179-182, 2000 14. Hakala P, Randell T, Valli H: Laryngoscopy and fiberoptic intubation in acromegalic patients. Br J Anaesth 80:345347, 1998 15. Goldhill DR, Dalgleish JG, Lake RIt: Respiratory problems and acromegaly. An acromegalic with hypersommia, acute airway obstruction and pulmonary oedema. Anaesthesia 37: 1200-1203, 1982

ENDOCRINE DISEASES AND THE AIRWAY 16. Singelyn FJ, Scholtes JL: Airway obstruction in acromegaly: A method of prevention. Anaesth Intensive Care 16: 491-492, 1988 17. Schmitt H, Buchfelder M, Radespiel-Troger M, et al: Difficult intubation in acromegalic patients. Incidence and predictability. Anesthesiology 93:110-114, 2000 18. Hassan SZ, Matz GJ, Lawrence AM, et al: Laryngeal stenosis in acromegaly: a possible cause of airway difficulties associated with anesthesia. Anesth Analg 55:57-60, 1976 19. Ovassapian A, Doka JC, Romsa DE: Acromegaly- use of fiberoptic laryngoscopy to avoid tracheostomy. AnesthesioIogy 54:429-430, 1981 20. Riddell V: Thyroidectomy: Prevention of bilateral recurrent nerve palsy. Br J Surg 57:1-11, 1970 21. Tanigawa K, Inoue Y, Iwata S: Protection of recurrent laryngeal nerve during neck surgery: A new combination of neutracer, laryngeal mask airway, and fiberoptic bronchoscope. Anesthesiology 74:966-967, 1991 (letter) 22. Greatorex RA, Denny NM: Application of the laryngeal mask airway to thyroid surgery and the preservation of the

7 recurrent laryngeal nerve. Ann R Coll Surg Engl 73:352-354, 1991 23. Hobbiger HE, Allen JG, Greatorex RG, et al: The laryngeal mask airway for thyroid and parathyroid surgery. Anaesthesia 51:972-974, 1966 24. Palazzo FF, Allen JG, Greatorex RA: Laryngeal mask airway and fibre-optic tracheal intubation in thyroid surgery: A method for timely identification Of tracfieomalacia requiring tracheostomy. Ann R Col! Surg Engl 82:141-142, 2000 25. Wakeling HG, Ody A, Ball A: Large goitre causing difficult intuhation and failure to intubate using the intubating laryngeal mask airway: Lessons for next time. Br J Anaesth 81:979-981, 1998 26. Roizen MF: Anesthetic implications of concurrent disease, in Miller RD (ed): Anesthesia (5th ed). Philadelphia, Churchill Livingstone, 2000, p 932 27. Bringhurst FR, Demay MB, Kronenberg HM: Hormones and disorders of mineral metabolism, in Wilson JD, Foster DW, Kronenberg HM, Lm'sen PR (eds): Williams Textbook of Endocrinology (gth ed). Philadelphia, WB Saunders, 1998, p 1178