A number of medical conditions can present special challenges to the anesthesiologist. This chapter reviews, in synopsis format, some of the more common conditions likely to affect airway management.
Diabetes and the Airway
The link between diabetes mellitus and difficult laryngoscopy has only been described in recent years. About one third of long term type diabetics (juvenile onset) will present with laryngoscopic difficulties. This is due at least in part to diabetic “stiff joint syndrome” characterized by short stature, joint rigidity, and tight, waxy skin. The fourth and fifth proximal pharyngeal joints are most commonly involved. Patients with diabetic stiff joint syndrome have difficulty in approximating their palms and cannot bend their fingers backward (“prayer sign”).
When the cervical spine is involved, limited atlanto- occipital joint motion may make laryngoscopy and intubation quite difficult. Glycosylation of tissue proteins from chronic hyperglycemia result in abnormal cross-linking of collagen is believed to be responsible . Joint involvement in diabetics is sometimes evaluated using a “palm test” which determines how much of a patient’s palm can be made to make contact with a flat surface. Reissel et al. studied laryngoscopic conditions in 62 diabetic patients given a fentanyl/ thiopental/ vecuronium induction for renal transplantation or vitrectomy surgery. Joint stiffness, as judged by the “palm test” was shown to correlate with difficulty in laryngoscopy.
Nichol and Zuck point out that “almost all of the extension of the head on the neck that is helpful to the laryngoscopist takes place at the atlanto-occipital joint”. In some cases of patients presenting with an “anterior larynx” (which Nichol and Zuck view as a misnomer) head extension is limited by abutment of the occiput against the posterior tubercle of the atlas, with the result that the cervical spine bows forward at laryngoscopy pushing the larynx anteriorally. The same effect may occur in stiff joint syndrome patients, not because of abutment of the atlas against the occiput, but because of cervical spine joint immobility.
Obstructive Sleep Apnea
Obstructive sleep apnea (OSA) consists of absent nasal and oral airflow during sleep despite continuing respiratory effort. This is generally due to backward tongue movement and pharyngeal wall collapse (glossoptosis) secondary to interference with the normal coordinated contraction of pharyngeal and hypopharyngeal muscles. Enlargement of the tongue, tonsils and/or adenoids is often contributory. OSA is diagnosed by finding at least 30 episodes of apnea (of duration at least 10 seconds) in a 7 hour study period. Many, but not all, patients are obese. From an anaesthetic viewpoint, OSA patients are particularly at risk for airway obstruction during the induction and recovery phases of anaesthesia. Management options range from heightened clinical monitoring to use of artificial airway devices (e.g. nasopharyngeal airway, Grudel airway), to carrying out induction and recovery in a sitting or semi-sitting position to minimize pharyngeal wall collapse.
Patients 20% over their ideal weight are obese. When they are 100% over this weight they are said to be “morbidly obese”. The obese patient has a reduced functional residual capacity (FRC) with reduced pulmonary oxygen stores, leading to rapid desaturation when apnea occurs. Obese patients with a short thick neck, a large tongue and/or redundant folds of oropharyngeal tissue may be difficult to intubate and are at increased risk to develop airway obstruction. Positive pressure ventilation may be more difficult in these patients because of decreased chest wall compliance (restrictive lung defect). The increased work of breathing associated with obesity leads patients to take smaller tidal volumes and breath at an increased respiratory rate, leading to atelectasis, ventilation/perfusion mismatching, and increased degrees of airway closure. Should a surgical airway become necessary, the situation is made much more difficult as the surgeon attempts to identify the trachea deep in a mound of adipose tissue. Very obese patients are at increased risk of regurgitation/aspiration both because of increased intraabdominal pressure and the high incidence of patients having gastric fluid volumes greater than25 ml and gastric fluid pH less than 2.5.
Anaesthetic Considerations in the Patient with Rheumatoid Arthritis
Rheumatoid arthritis (RA) is a multisystem autoimmune disease with many anesthetic implications. Patients with RA may challenge the anesthesiologist at the time of tracheal intubation because cervical spine instability. In addition, temperomandibular joint (TMJ) or arytenoid joint immobility may limit safe access to the airway. The preoperative anesthetic assessment must focus on possible airway difficulties. Patients must be questioned and examined to ellicit evidence of neck pain, limitation of cervical spine movement, nerve root impingement or spinal cord compression. Lateral C-spine flexion-extension X-rays are indicated in patients with cervical spine symptamotology to assess the possibility of cervical spine subluxation. The need for these X-rays in completely asymptomatic patients remains controversial; however, one should keep in mind case reports of neurological damage following direct laryngoscopy and intubation in asymptomatic patients. Patients with cervical spine instability should generally be intubated and postioned awake before surgery to avoid neurological injury. The TMJs must be examined to ensure that mouth opening and anterior subluxation of the mandible will permit direct laryngoscopy. Patients demonstrating stridor or hoarseness require awake direct or indirect laryngoscopy to assess the possibility of arytenoid involvement and determine the size of the glottic opening. Finally, the larynx may be displaced from its usual location by erosion and generalized collapse of the cervical vertibrae.
Zenker’s diverticulum is an esophageal outpouching for which patients sometimes seek a surgical repair. Because food and other material may settle in the diverticulum, there is a concern that any pouch material may find itself into the airway with the induction of anaesthesia. Some patients can manually empty the pouch themselves; others may benefit from suction catheter placement in the pouch prior to induction (easier said than done). One key thing to remember, however, is this: application of cricoid pressure (such as is done in a rapid sequence induction) may actually dislodge any pouch contents into the oropharynx.
The acromegalic patient suffers from an excess of growth hormone, usually from a pituitary adenoma. If this condition occurs prior to closure of the epiphipeal growth plates, giantism may occur. Once the growth plates have fused in adolescence, the patient may take on acromegalic features. From the viewpoint of airway management in the acromegalic patient, three concerns exist: (1) the tongue may be enlarged, (2) redundant folds of tissue may be present in the oropharynx and (3) laryngeal stenosis occurs more frequently than in the general population. These factors may make laryngoscopy and intubation somewhat more difficult and increase the likelihood of airway obstruction during anaesthetic induction and recovery. Should true giantism be encountered clinically (often for resection of a pituitary adenoma), the following potential problems should also be considered:
- possible need for an extra-long OR table
- possible need for an extra large laryngoscope
- ETTs may need to be cut longer then usual
- an extra large face mask may be necessary
Pregnancy carries with it the following airway considerations:
- Failed intubation (1:300-1:500 parturients) occurs approximately five times more frequent than in the general population. External assessment of the parturient’s airway does not reliably predict difficult intubation.
- Patient is generally regarded as a “full stomach” after 16-20 weeks gestational age, with concern of aspiration.
- Airway edema may be present, especially if the patient is preeclamptic, so that a smaller than usual ETT may be required.
- One-third to one-half of pregnant women in the supine position develop airway closure during normal tidal ventilation thus predisposing them to hypoxemia . Increased oxygen consumption (20% higher at term than in the nonpregnant state) associated with pregnancy also increases the likelyhood that a parturient will become hypoxic during induction of anesthesia.
- Big breasts may interfere with intubation.
During anaphylactic (or anaphylactoid) reactions, massive release of histamine and other noxious substances from mast cells and basophils produce “leaky capillaries” which result in interstitial fluid buildup (edema). When edema of any portion of the airway results, respiratory obstruction can occur. Airway-related clinical manifestations may include dyspnea, stridor and facial edema. Erythema, urticaria, bronchospasm and hypotension may also be present. While many older textbooks advocate establishing a surgical airway, early intubation is now the usual recommendation if the airway appears to be at risk. Another airway-related problem which may occur in anaphylaxis is bronchospasm, sometimes with sufficient severity that air entry is so poor that wheezing is not present and ventilation may be next to impossible. As always, the primary drug treatment in life-threatening anaphylaxis is epinephrine (2-4 mcg/kg), either IV, SQ, or IM and repeated at 5 – 10 minute intervals based on the patient’s clinical response.
Airway problems posed by mediastinal masses provide some of the greatest challenges faced by clinical anesthesiologists. Anesthesia is needed primarily for diagnostic biopsies and staging of neoplasms but also occasionally for relief of acute airway obstruction. The choice of anesthesia is guided by the etiology and location of the mass (extent and effect on adjoining(SP) airway or cardiovascular structures). All patients require a meticulous preoperative assessment that includes careful history and physical exam aimed at delineating symptoms or signs that may indicate compression of major airways, the great vessels or the heart itself. For emergency relief of airway compromise, one may have to precede with rigid bronchoscopy as a means of relieving the obstruction and determining the extent of airway compression. In elective or semi-elective circumstances preoperative laboratory investigations should include ECG, CXR, contrast CT scan of the thorax and, if indicated by the patient’s symptoms or signs, an echocardiogram and/or pulmonary flow volume loops with the patient sitting and supine (where available).
Great clinical judgement and experience must be exercised by the anesthetist and surgeon in choosing a suitable anesthetic plan. In general, short acting agents should be used so that the patient returns to a “fully awake” state immediately postoperavely. In instances where the mass is small and does not compress ajoining structures one may procede with an intravenous induction and institute positive pressure ventilation. On the other hand, one must be cognizant (SP) that airway or vascular compression may worsen during general anesthesia. Thus a prudent approach may include topical anesthesia of the airway followed by awake fibreoptic intubation of the trachea or inhalational induction and spontaneous ventilation supplemented by manual assistance. Seriously ill patients may requre diagnostic biopsy or airway intrumentation with local anesthesia alone as the risks of general anesthesia may outweigh any possible benefits. In any event, a surgeon experienced with rigid bronchoscopy must be present at induction if the potential for airway compression is substantial. If the airway is “lost” under anesthesia, placing the patient in the lateral decubitus or prone position may relieve the obstruction, however, rapid intubation of the airway with a rigid bronchoscope is usually most effective.
Significant obstruction of the superior vena cava by tumor (SVC syndrome) is indicated by cyanosis, engorged veins and\or edema of the upper body. Patients with SVC syndrome are especially prone to airway obstruction, hypotension and massive hemorrhage. Ideally: patients should be kept in a semi-upright position to reduce airway edema; diagnostic tissue should be obtained under local anesthesia; packed red cells should be available in the operating room; large bore intravenous access should be obtained in the lower extremities and; arterial catheter should be inserted preoperatively.
MEDIASTINAL MASSES: Practical Points
- Signs and symptoms indicating airway compromise include: stridor, orthopnea, dyspnea, cyanosis, cough, decreased breath sounds and wheezes.
- Signs and symptoms indicating critical cardiovascular compression include: fatigue, neck/facial edema, faintness, JVD, headache, papilleadema, dyspnea, pulsus paradoxus, orthopnea, postural changes in BP and pallor.
- If there is SVC obstruction, don’t put an IV in the arms; the main source of venous return is the IVC, so the main IV will have to go in a leg.
- With an anterior mediastinal mass, the mass compresses the mediastinal structures to varying degrees. Compression is maximal with the patient lying supine, and would be expected to be less with the patient lying prone or on his or her side. If the patient seems to be getting into trouble when positioned supine, consider placing the patient on his or her side, or even prone.
- With SVC obstruction the face may become edematous and venous engorgement is present. The edema is a concern from the viewpoint of airway management – special concern must be given to these patients when they are extubated. The venous engorgement is potentially a problem when nasal intubation is being considered (popular for fiberoptic intubation); the engorgement of nasopharyngeal veins may lead to troublesome epistaxis.
- Echocardiography serves to evaluate myocardial contractility and for assessment of tumor encasement of the heart and great vessels.
- Patient history information (especially symptoms when supine) often tells most of the story. That, together with a CT scan of the thorax and a chest x-ray provide the most important information. Differences between sitting and supine flow volume loops can help test for intrathoracic or extrathoracic obstruction. (However, most pulmonary function labs are not set up to do flow-volume loops in the supine position.) Fiberoptic bronchoscopy also evaluates dynamic AW obstruction. Finally, never forget that patients asymptomatic while awake may obstruct their airway during anaesthesia.
- In emergency situations where there is no time for a more complete assessment, increased emphasis must be placed on the clinical findings, especially signs and symptoms in the supine position. Options to consider in this case: (a) awake FOB for intubation, checking for dynamic airway collapse, and (b) maintenance of spontaneous breathing throughout (muscle relaxants may lead to airway loss).
- Where appropriate, preoperative radiation or chemotherapy should be considered to shrink sensitive tumors and alleviate symptoms.
Epiglottitis is the most dreaded of airway infections, especially in children. Victims are usually children age 2 to 6, often infected with H. flu. These children may appear to be systemically ill (“toxic”) perhaps with a fever and/or perhaps sitting up in a “tripod” position and drooling from difficulty with swallowing. Examining the child’s airway may exacerbate the problem (by increasing airway edema) so tongue depressors and laryngoscopy are not options in the inital management of the child. Anything that might bring the child to cry (for example, needles) should generally be avoided. Consequently (and for other reasons), the usual approach to management involves a careful inhalational induction with the child sitting in the anesthetist’s lap and intubation of the child while he or she is breathing spontaneously under deep halothane anesthesia. If at laryngoscopy the orifice through the epiglottis can’t be identified, one trick is to have someone compress the child’s chest, thus generating a small bubble in the epiglottis that the anesthetist can aim for.
In the past patients were managed by emergency tracheostomy, however contemporary management of children includes short term nasal intubation and intravenous antibiotic therapy. There is considerable disagreement concerning airway management in the adult however there seems to be a growing concensus that the majority of adults are adequately treated in an intensive care unit with inhaled mist, antibiotics and corticosteroids and that tracheal intubation is necessary only if symptoms of respiratory distress develop.
Epiglottitis can occur in adults too (George Washington is said to have died of it) but the situation is less dreadful here because the adult airway is larger. Most people would use awake fiberoptic laryngoscopy to secure the airway in this situation. There is growing experience with conservative management of adult epiglottitis (admission to an ICU for intravenous antibiotic therapy and with avoidance of intubation).
The Airway in HIV-Infected Patients
With increasing frequency, clinicians are becoming aware of airway-related problems in HIV-infected individuals. For example, Kaposi’s sarcoma in AIDS patients has been reported to result in airway obstruction. Similarly, opportunistic infections can also result in airway obstruction. A recent review by Judson and Sahn provides additional information for the interested reader.
Ludwig’s angina is a multispace infection of the floor of the mouth. The infection starts with infected mandibular molars and spreads to sublingual, submental, buccal and submandibular spaces. The tongue becomes elevated and displaced posteriorly, which may lead to loss of the airway, especially when the patient is placed in the supine position. An additional concern is the potential for abscess rupture into the hypopharynx (with possible lung soiling) either spontaneously or with attempts at laryngoscopy and intubation. Airway management options will depend on clinical severity, surgical preferences, and other factors (e.g. CT findings), but elective tracheostomy prior to incision and drainage remains the classical treatment modality (although many experts advocate fiberoptic intubation if at all possible.
Retropharyngeal abscess formation may occur from bacterial infection of the retropharyngeal space secondary to a tonsillar or dental infections . Untreated, the posterior pharyngeal wall may advance anteriorly into the oropharynx, resulting in a dyspnea and airway obstruction. Other clinical findings may include difficulty in swallowing, trismus and a fluctuant posterior pharyngeal mass. An abscess cavity may be evident on lateral neck x- rays with anterior displacement of the esophagus and upper pharynx. Airway management may be complicated by trismus or airway obstruction. Because abscess rupture can lead to soiling of the trachea, contact with the posterior pharyngeal wall during laryngoscopy and intubation should be minimized. Incision and drainage is the mainstay of treatment. Tracheostomy is often, but not always required.