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Print version ISSN 0034-7094
On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.56 no.2 Campinas Mar/Apr. 2006
Hoarseness after tracheal intubation*
Ronquido después de la entubación traqueal
Regina Helena Garcia Martins, M.D.I; José Reinaldo Cerqueira Braz, TSA, M.D.II; Norimar Hernandes Dias, M.D.III; Emanuel Celice Castilho, M.D.IV; Leandro Gobbo Braz, M.D.III; Lais Helena Camacho Navarro, M.D.III
Assistente Doutora da Disciplina de Otorrinolaringologia, FMBUNESP
IIProfessor Titular do Departamento de Anestesiologia, FMBUNESP
IIIMédico do Hospital das Clínicas; Pós-Graduando (nível doutorado) do Programa de Pós-Graduação em Cirurgia, FMBUNESP
IVMédico do Hospital das Clínicas; Doutor em Cirurgia, FMBUNESP
AND OBJECTIVES: To describe the main causes of hoarseness after undergoing
CONTENTS: Hoarseness is one of the most common postoperatory symptoms after tracheal intubation and the effects vary in terms of duration, depending on the factors that caused it and on how severe the damage to the laryngeal structures. This study performed a brief check-up of the anatomical structures of the larynx, describing the main traumatic lesions in the region following tracheal intubation. It also emphasized the importance of caring for the larynx, as well as undergoing early diagnosis and treatment.
CONCLUSIONS: Traumatic lesions of the laryngeal structures that occur during intubation are the most common causes of hoarseness. As such, it is important to perform an early diagnosis and adopt preventive measures.
Key words: COMPLICATIONS: dysphonia; hoarseness; INTU-BATION, Tracheal.
Y OBJETIVOS: Describir las principales causas del ronquido después
de la Entubación Traqueal.
CONTENIDO: El ronquido después de la entubación traqueal es uno de los síntomas más frecuentes en el proceso postoperatorio, pudiendo presentar duraciones que varían, dependiendo de los factores de causa y de la gravedad del comprometimiento de las estructuras de la laringe. Fue realizada una breve revisión de las estructuras anatómicas de la laringe, donde fueron descritas las principales lesiones traumáticas de ese órgano, provenientes de la entubación traqueal y se destacó la importancia de sus cuidados, como también el diagnóstico y tratamiento precoces.
CONCLUSIONES: Las lesiones traumáticas de las estructuras de la laringe durante la entubación son causas frecuentes de ronquido, siendo importante el diagnóstico precoz y la adopción de medidas preventivas.
One of the most common symptoms during the postoperative period is hoarseness, which may occur in anywhere from 14.4% to 50% of patients that underwent tracheal intubation 1,2. In the vast majority, this symptom is temporary and lasts on mean two to three days. Postoperative hoarseness may have an effect on the patient's degree of satisfation as well as on their activities after leaving the hospital. However, in 10% of the cases, hoarseness becomes a permanent phenomenon, bringing changes in lifestyle for the patient, who had a normal voice before surgery. Hence, it is important to establish the main causal factors involved in this process and to be aware of the resources available for diagnosis and treatment.
ANATOMICAL, MORPHOLOGICAL AND PHYSIOLOGICAL ASPECTS OF THE LARYNX TO CONSIDER
The larynx is a muscle-cartilaginous structure in which a delicate and intrinsic muscle structure interconnects with cartilages to promote the opening of the vocal folds during breathing and the closing of the folds during phonation and swallowing preventing food from entering airway. The innervation of the intrinsic muscles of the larynx is made up inferior laryngeal nerves and recurrent laryngeal nerves, which were branches of the vagus nerve. Only the cricothyroid muscle receives innervation from the superior laryngeal nerve.
The epithelium that lines the vocal folds is of the stratified squamous variety and is made up of many layers of thin, flat cells and basic round cells. The cells of the more superficial layers are constantly renewing themselves and have microprojections (Figures 1 and 2). The epithelium lies above a basement membrane that separates the epithelium from the lamina propria (Figure 3) 3,4 .
In A (7,550 X) you can see the epithelium made up of flattened, juxtaposed cells. In B (42,000 X) you can observe details on the epithelial cells with superficial microfolds. In C (17,000X), you can see the cells from the basal layer with nuclei perpendicular to the basal membrane and the cytoplasm rich in mitochondria (thin arrow). The basal membrane is regular, thin and continuous (thick arrow).
The lamina propria is a laminar structure with some unique characteristics. Didactically speaking, it is made up of three layers. The superficial layer is known as the Reinke space and is composed of less dense collagen, few cells, some fibroblasts and very few capillaries. This space allows for the wave-like movement of the mucous above the superficial lamina, which is important in determining vocal quality. Some surgical procedures or even congenital epithelial irregularities may lead to the destruction, the atrophy or fibrosis of the Reinke space, which in turn may prevent adequate movement of the mucous layer over the superficial lamina which in turn have an important role in determining vocal quality. The intermediate and deep layers of the lamina propria are made up of dense collagen fibres and elastic fibres (Figure 4); they constitute the vocal ligament, located above the vocal muscle (thyroid arytenoid muscle) 5,6.
The vocal folds have very few lymphatic vessels, meaning that an edema on the inside will take long to be reabsorbed, thereby resulting, many times, in secondary lesions, such as vocal polyps.
The structure of the glottis is V-shaped, where in the anterior portion, which is positioned obliquely at an angle, projects itself towards the cervical regions in front of the thyroid cartilage. The posterior region of the glottis is in close contact with the superior sphincter of the esophagus and, often times, is affected in patients with gastroesophageal reflux due to the constant acidic reflux in the region.
LARYNGEAL LESIONS: CAUSAL FACTORS AND REPERCUSSIONS IN VOCAL QUALITY
It is relatively common to see scientific articles aiming at many different complications involving tracheal intubation that are often the cause of symptoms related to the respiratory tract. In the literature, there are accounts of broken teeth, lesions in the mucous membranes of the lips, tongue, palate, floor of the mouth, uvula, esophagus, larynx and trachea, among other lesions 7-11. Consequently, the postoperative pharyngolaryngotracheal symptoms such as throat aches, difficulty talking, coughing, secretions increase and pain upon swallowing are common. Hoarsness, however, is a very common symptom due to the high incidence of laryngeal lesions during tracheal intubation, especially when neuromuscular blockers are not used 2.
The sensitive structures of the larynx may be affected for countless reasons. The trauma during intubation may occur in emergency situations or situations in which the glottis is hard to expose, thereby resulting in laserations and hematomas on the vocal folds, as well as luxations of the arytenoid cartilages and muscle disinsertions 12.
Another important factor that causes complications in the respiratory tract is the period that the tracheal cannula remains in contact with the mucous membranes of the larynx and trachea. The incidence of complications involving tracheal intubation is said to increase significantly after the seventh day of intubation, when the recommendation for the tracheotomy is put discussed 13-17. Holzki 7 studied lesions in the respiratory tract related to intubation in children and found that they occur in 20% of cases, especially in children undergoing intubation for more than 25 days. This percentage increases if the caliber of the cannula is larger; in fact, according to the author, they are the main cause of laringotracheal traumatism. Hence, the choice of the cannula's diameter is another important point to consider, seeing as, due to the V-shape of the glottis, the posterior of the larynx will be in close contact with the cannula. When one uses large-caliber tracheal cannulas, the region may suffer the consequences of an ischemy caused by compression of the cannula on the mucous layer. In these cases, one will observe necrosis and superficial ulceration of the mucous layer immediately following extubation. According to Holzi 7, the most serious complication brought about by tracheal intubation is a necrosis on the circumference of the cricoid cartilage which evolves into subglottic stenosis.
The use of stainless steel spiral reinforced cannula in head and neck surgeries involving both oral and nasal intubation decrea-ses the incidence of potential tracheal lesions because they are more malleable and do not result in compressions or folds.
When tracheal cannula with cuffs are used, it is recommended that the pressure inside remain lower than the pressure of the capillary perfusion, that is, lower than 30 cmH2O 18-22. Castilho et al. 22, after a hystological analysis of the tracheal mucous of dogs in contact with the cuff, observed epithelial lesions when compared to normal respiratory epithelium, such as areas with superficial erosion and where cilius fall, even when using a very low pressure of 13 cmH2O. It is important to emphasize that a large part of these lesions are resolved naturally and spontaneously due to the epithelium's ability to renew itself. However, in some circumstances, the evolution of this process may cause greater damages and lead to laryngeal lesions of varying degrees of gravity, as is the case with patients who are diabetic or debilitated, which systemic infections or changes in hemodynamics.
Among the most common laryngeal lesions involving intubation you can find:
Edema and Hematoma
This occurs in the Reinke space and prevents the ideal wave-like movement of the mucous, thereby causes changes in vocal quality. Due to low lymphatic drainage in the region, reabsorbing an edema that occupies the Reinke space may be a slow process, which makes vocal recovery more difficult. In the postope-rative period, the patient may attempt to speak with a clearer voice and feel frustrated, triggering additional strains on the muscles and tension around the cervical and laryngeal musculature. If this inadequate pattern of phonation is maintained and becomes an habit, the continuous traumatic impact on the vocal folds while talking will resulting secondary lesions on the mucous layer of the larynx, such as vocal polyps (Figure 5). In the beginning of this process, it is recommended and highly beneficial for the patient to not use his or her voice. Systemic corticoids are potent anti-inflammatory agents and should be taken for a few days, as long as it is recommended for the patient in question. Many secondary lesions need to be surgically removed through endoscopy in order to be completely treated.
Lacerations in the laryngeal mucous layer may scar due to fibrosis and adhesions. When scarring occurs in the anterior commissure of the glottis, the scars do great damage to the voice, because they get in the way of the phonatory process (Figure 6). On the other hand, scarring processes which involve the posterior portion of the glottis may lead to a narrowing of the glottis, resulting in symptoms such as dyspnea and a weak, feeble voice. There are situations in which the arythenoid muscles are damaged and the fibrosis that is created in those places prevents the complete abduction of the vocal folds, which then stay fixed at the middle region, simulating a case of laryngeal paralysis (Figure 7). An endoscopic exam will allow the doctor to clarify the diagnosis in order to decide upon the adequate course of treatment in each of these cases.
Lacerations that reach the deeper layers of the lamina propria and the vocal ligament are particularly detrimental to the wave-like movement of the mucous, leading to changes in vocal quality and preventing voice modulation.
The tracheal rings also run the risk of laceration by the distal extremity of the intubation cannula.
Muscle Traumatism (Paresis and Muscle Paralysis)
When the lesion following a tracheal intubation extends to the intrinsic muscles of the larynx, temporary or permanent paresis or paralysis of the vocal folds may ensue. The unilateral paralyses have a severe impact on voice emissions, because the paralyzed vocal fold is located more to the side compared to the healthy fold, preventing ideal contact between both folds during phonation. In these conditions, the voice becomes feeble and debilitated, resulting in fatigue and exhausted muscle strain during phonation. In bilateral paralysis, respiratory symptoms of dyspnea predominated, since both vocal cords are prevented from abducting. In these cases, the voice itself is not affected very much. Traumatic laryngeal paralysis tend to evolve naturally and spontaneously. However, if this does not occur, surgical treatment may be necessary.
Because of their location on the posterior region of the glottis, arytenoid cartilages are more vulnerable to intubation traumas. These sub-luxations lead to assymetry in the vocal folds and in the way they move. It is possible to obtain, most of the time, a satisfactory closing of the glottis and to regain partial or total vocal quality by developing compensatory muscle mechanisms in the vocal folds. Some patients with laryngeal assymetries develop secondary lesions, such as vocal cord nodules, due to the constant muscle compensation during phonation.
After tracheal intubation patients may develop vocal cord granuloma, usually at the vocal apophysis, at the level of the posterior of the glottis, where the cannula was in close contact with the laryngeal mucous membrane (Figure 8) 23. Granuloma can be unilateral or bilateral, with a smooth surface and pedunculated, in which case they are mobile. The vocal symptoms arise 15 to 20 days after the removal of the tracheal tube, but there may not be symptoms if the granuloma are small. When they implant themselves in the anterior portion of the glottis, they result in damage to vocal emissions (Figure 9). They can also be related with stenosis of the glottis (Figure 10). Pontes et al. 24, while studying the etiology of laryngeal granulomas, found the following factors to be among the main causes: vocal abuse (33.3%), gastroesophageal reflux (30.3%), tracheal intubation (22.7%) and idiopathic origins (9%).
An endoscopic examination will allow the doctor to determine the exact location of the granulomas' implantation in order to recommend the appropriate surgical procedure.
Laryngeal stenosis is an important cause of hoarseness after intubation and due to the difficulty in treatments, it is one of the most feared. All factors mentioned above may contribute to its appearance. As well as the serious effects it has on the voice, the patient also experiences intense dyspnea. Brichet et al. 16 stressed that, in many cases, the initial diagnosis can be mistaken for bronchospasm, pulmonary embolism or acute myocardial infarction, since the patient arrives for the check-up sweating, with intense respiratory discomfort, heart palpitations, dyspnea and cyanosis.
According to the literature, most authors state that the incidence of stenosis after intubation is between 5% and 8%. With the development of new types of tracheal cannula in the last few years and a higher level of awareness regarding the importance of preventive measures, there have been even lower incidences registered. Walner et al. 14 conducted a retrospective study in 544 newborns admitted into intensive care units. They found that 281 babies had undergone tracheal intubation for a period averaging 11 days, and none of them showed signs of subglottic stenosis. It must be taken into account, however, that the tracheal cannula used in infants do not have cuffs and, therefore, are less traumatic than those used on adult patients.
In most cases, the patient suffering from laryngeal stenosis evolves to tracheotomy and the permanent correction is achieved by way of a laryngotracheoplasty 25,26. For treating lighter cases, in which the cicatricial ring is not very thick and less than 1 cm wide, one can try a radial incision with laser or endoscopic dilations 16. The external laryngotracheal approach is reserved for the more severe cases. These last few years, some have suggested the topical use of Mitomycin C in the area affected by the stenosis 27,28. Mitomycin C is an antibiotic drug with antiproliferation properties that stop the fibroblasts from migrating, thereby, also stopping the formation of fibrosis. Ribeiro et al 28 conducted a study on lab rats comparing the scarring of surgical pressure ulcers with and without the application of topical Mitomycin C. The authors found a clear decrease in fibroblast migration as well as in fibrosis formation for the animals that had been submitted to Mitomycin C, testifying to the effectiveness of the drug.
The causes of hoarseness after intubation vary greatly, as does their severity. It is important to emphasize the need to exercise extreme caution during the tracheal intubation procedure, choose a cannula with an appropriate caliber, use neuromuscular blocksers during intubation, monitor the neuromuscular block during anesthesia, monitor the cuff pressure and keep the patient on an adequate level of sedation or anesthesia.
In the case of extensive lesions on the larynx, one should not hesitate to decide in favor of an early tracheotomy, getting rid of the damaged mucous layer that had been in contact with the tracheal tube and promoting epithelial recovery.
Due to the high level of morbidity associated to tracheal intubation, a laryngeal mask is sometimes used by anesthesiologists (when appropriate) in patients that use their voice in their professional activities, such as singers and reporters, seeing as the cuffs in this case are not in contact with the glottic structures 29.
Performing a voice evaluation and routine endoscopy in patients undergoing tracheal intubation is an important measure in the early diagnosis of laryngeal and tracheal complications; indeed, this allows for the prevention of a great many of them.
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for publication 24 de maio de 2005
Accepted for publication 16 de Janeiro de 2006
* Received from Disciplina de Otorrinolaringologia e Departamento de Anestesiologia da Faculdade de Medicina de Botucatu, Universidade Estadual Paulista (FMB-UNESP), Botucatu, SP.