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GMS Current Topics in Otorhinolaryngology - Head and Neck Surgery

Deutsche Gesellschaft für Hals-, Nasen-, Ohrenheilkunde, Kopf- und Halschirurgie e.V. (DGHNOKHC)

ISSN 1865-1011

Perioperative risks and their management in patients with sleep-related breathing disorders

Review Article

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  • corresponding author Harald V. Genzwuerker - Clinic of Anaesthesiology and Intensive Care Medicine, University Hospital Mannheim, Germany
  • Juergen Meinhardt - Clinic of Anaesthesiology and Intensive Care Medicine, University Hospital Mannheim, Germany

GMS Curr Top Otorhinolaryngol Head Neck Surg 2006;5:Doc05

The electronic version of this article is the complete one and can be found online at: http://www.egms.de/en/journals/cto/2006-5/cto000032.shtml

Published: October 5, 2006

© 2006 Genzwuerker et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Abstract

Patients with sleep apnea syndromes pose several challenges to the anaesthetist. These are resulting from comorbidity, but mainly from special requirements for pre-, intra- and postoperative management.

Frequently, the diagnosis is not known or not diagnosed adequately, making careful preoperative evaluation of the patient by the anaesthetist imperative to identify patients at risk. Besides cardiovascular complications, problems with airway maintenance must be expected, calling for adequate planning. Several general considerations for anaesthesiologic management should be taken into account. The use of short acting pharmacologic agents is recommended to reduce the risk of postoperative episodes of hypoxia following general anaesthesia.

Close cooperation of anaesthesia and the surgical specialties involved is the basis for safe management of patients with sleep related syndromes.

Keywords: sleep apnea syndrome, anaesthesia, airway management, hypoxia


1. Background

Sleep apnea syndromes can be generally divided into central and obstructive types. As far as cardiovascular, respiratory and central nervous manifestations are concerned, the different forms are very similar, so the main focus will be on the obstructive sleep apnea syndrome (OSAS). By definition, OSAS is a problem of the upper airways. Epidemiologic studies find an incidence of 1% to 4% in mid-age adults. Men are suffering from sleep apnea syndromes approximately twice as frequently as women. Familiar disposition and genetic components could be identified. [1], [2] The correct diagnosis is made in only a small percentage of patients.

Patients with sleep apnea syndrome require a specific perioperativen management. Due to nightly sleep apnea episodes with consecutive hypoxemia, physiologic changes involving mainly cardiovascular organs and the central nervous system are induced. The diagnosis of OSAS implies an increased probability of intubation difficulties as well as problems with airway maintenance. In addition, patients with sleep apnea syndromes pose several challenges to the anaesthetist, resulting from the special requirements of the surgical intervention planned as well as from the increased likelihood of relevant pre-existing comorbidity [3]. Still, a common lack of awareness of the problems in OSAS patients with the implications for perioperative management can frequently be found.

Three different groups of patients undergoing surgery with general anaesthesia can be identified considering the (co-)diagnosis of obstructive sleep apnea syndromes:

  • Patients with diagnosed OSAS
  • Patients with symptoms suggestive for OSAS
  • Patients without symptoms or in whom symptoms were not recognized preoperatively

Surgical procedures can be OSA related or for any other diagnosis requiring an intervention (e.g. abdominal or orthopaedic surgery, urology). Common goal in all patients will be to avoid inadequate ventilation and oxygenation resulting in hypoxemia as well as hemodynamic changes such as tachycardia, arrhythmia and hypertension that will also lead to increased morbidity and mortality. This calls for comprehensive perioperative management including preoperative phase, induction of anaesthesia, phase of the surgical intervention, recovery from anaesthesia, and postoperative monitoring and care. The goal is to identify patients with a relevant risk profile in time to allow the anaesthesist to assist with a consequent risk reduction.

1.1 Sleep physiology

Diaphragmal contraction causes inspiration due to the resulting negative pressure. Concomittant narrowing of oro- and hypopharynx is compensated by a pre-inspiratory increase in oropharyngeal muscle tone in healthy individuals. During sleep, this muscle tone is less pronounced. Even under physiologic conditions, an increase of resistance in oro- and hypopharynx results. At the same time, hypoxia or hypercapnia induce a small increase of respiratory minute volume.

Lack of pre-inspiratory activation of oropharyngeal muscles and consecutive apnea due to obstruction of the upper airways results in an increase in respiratory efforts, triggered by hypoxia and hypercapnia. The negative airway pressure increases, further promoting oropharyngeal obstruction. The velo-pharyngeal closing pressure correlates well with the extent of desaturation [4]. Arousal of the patient causes an increase in oropharyngeal muscle tone that eliminates the obstruction.

During the postoperative phase, impairment of sleep pattern can be found: while normal sleep in adults consists of 4 to 6 sleep cycles (REM- and non-REM-phases), episodes of deep sleep and REM-phases are reduced in the first nights following surgery. 4 to 5 nights later, a compensatory excess of deep sleep phases and a REM-sleep rebound can be measured [5].

1.2 Concomitant diseases

Patients with OSA frequently present with concomitant symptoms or diseases. Whether these are result or cause of the syndrome remains unclear in a high percentage of patients [3].

During the preoperative interview, patients should be questioned for snoring, sleep disorders, sudden arousal with respiratory distress, nycturia, nightmares and nightly sweating. During daytime, excessive fatigue, but also loss of power, changes in personality, dryness of mouth in the morning and headaches as well as sexual dysfunctions can be found.

Typical cardio-circulatory and pulmonary concomitant diseases are hypertension, a variety of arrhythmias, coronary syndromes, congestive heart failure, or polycythemia. These diseases already lead to a raised perioperative risk that increases in the presence of OSA. Cardiovascular changes are the main reason for OSA-related mortality that can be as high as 37% within 8 years [6].

When certain conditions and chronic diseases are present, the incidence of sleep apnea syndromes is heightened. Obstructive components can be found in morbidly obese patients, and when macroglossia, nasal septum deviations, tonsillar hypertrophy, nasopharyngeal tumors or laryngeal deformations, but also diabetes, chronic renal failure, thyroid hypofunction, regular alcohol consumption or intake of certain drugs (e.g. benzodiazepines) are part of the patient's history. Central sleep apnea syndromes are frequently associated with neuromuscular diseases like myasthenia gravis, myotonic muscle dystrophies, phrenicus palsy, or with neurological disorders like brainstem tumors or bleeding, encephalitis or head trauma.

1.3 Clinical diagnostics

Besides patient history and clinical symptoms, polysomnographic monitoring will provide the most important informations regarding presence and extent of a sleep apnea syndrome. Consequently, patient referral to an accredited sleep laboratory should be considered in all patients presenting with symptoms when planned for elective interventions (that are not part of the therapy of a polysomnographically diagnosed OSA) due to the increase perioperative anaesthesiologic risk.

A few key questions can help to identify patients that might suffer from an undiagnosed OSA: besides questioning the patients or their partners about snoring, questions regarding witnessed apneas, fatigue and headaches in the morning, fatigue during the day and a tendency to fall asleep should be part of a focused interview [3].

1.4 OSA therapy

As in any other concomitant disease, continuation of domestic therapy should be part of the anaesthesiologic management of OSA patients. In sleep apnea syndromes, the therapy aims at elimination of airway obstruction to allow uninterrupted sleep without desaturation or hypoventilation. This concept must continue in the immediate postoperative phase, making diligent information about the therapeutic measures in each individual patient mandatory. Knowledge of the OSA treatment concept will in return also allow judgement of the necessity of a staged anaesthesiologic management as described below.

1.4.1 General measures

Abstinence from alcohol and sedatives are basic principles of OSA treatment. Benzodiazepines will influence the activity of the genioglossic muscle [7], alcohol reduces the tone of oropharyngeal muscles, increase apneas and delays arousal [8], [9].

Although OSA may occur without concomitant obesity, weight reduction is an important part of treatment in obese patients. Cardiopulmonary diseases should be as adequately treated as in all patients undergoing surgical interventions.

1.4.2 CPAP

Many patients with sleep apnea syndromes will profit from an increase airway pressure during the night. Usually, nasal masks will be used. The CPAP level determined in a sleep laboratory should be administered during the postoperative phase using the patient's CPAP machine. The patients as well as the ward taking care of postoperative treatment have to be informed about the necessity to use such devices. Using CPAP therapy, the mortality of OSA can be reduced [6].

1.4.3 Drug therapy

In mild forms of OSA, drug therapy may be indicated. A tricyclic antidepressant (protryptilin, an inhibitor of norepinephrine re-uptake) is used. By suppression of REM sleep phases and optimization of oropharyngeal muscle activity, a reduction of OSA symptoms can be achieved. Due to the increased risk of hypertension and arrhythmias, a careful evaluation of risk and benefit is required. Of the few other substances that can be used for specific OSA treatment, theophylline is best known. As in patients with chronic obstructive lung disease, the narrow therapeutic range must be considered.

1.4.4 Oxygen therapy

By nightly oxygen administration, the extent of desaturations can be reduced. This purely symptomatic therapeutical approach can be considered when the more effective CPAP therapy is not tolerated ot has to be interrupted due to the type of surgical intervention (e.g. correction of nasal septum deviation with consecutive tamponade). Length of apneas is not influenced by oxygen administration.

1.4.5 Surgical therapy

Part of the OSA patients treated by anaesthetists is undergoing surgical interventions to correct documented anatomical aberrations. Depending on the extent of the sleep apnea syndrome and the obstruction(s) identified, the surgical intervention can consist of a combination of several interventions with a wide range of invasiveness, calling for diligent anaesthesiologic management: from correction of nasal septum deviation or tonsillectomy to partial resection of the epiglottis, all interventions applicable to the upper airway can be found. In a small percentage of patients, a surgical airway (tracheostomy) can be necessary to effectively treat severe forms of OSA.


2. Anesthesiologic principles

As in the preparation of any surgical interventions, preoperative evaluation and definition of perioperative management aims at risk reduction for the individual patient, considering general findings, the option to influence certain conditions and the urgency of the surgical intervention. Besides patient needs, the specific requirements of the surgical procedures also have to be considered.

2.1 Airway maintenance

75% of complications in OSA patients pertain to the airway [10]. Extensive guidelines for airway management have been introduced in 1992 by the American Society of Anesthesiologists (ASA) and were updated in 2002 [11]. The airway management guideline of the Germany Society of Anaesthesiology and Intensive Care Medicine (DGAI) published in May 2004 sets standards for airway maintenance that must be met in patients with OSA as well as in all other patients [12].

First step in managing the difficult airway is preoperative identification of patients at risk. Evidence on screening tests is controversial. All patients with diagnosed OSA or a suspicion based on clinical signs such as obesity, limited mouth opening or a large tongue should be considered as patients with difficult airway until proven otherwise [13]. Known problems with airway maintenance (e.g. anaesthesia records or an anaesthesia pass) should be included in planning the strategy for airway management. An airway history should be obtained whenever possible - with a few specific questions this can be achieved even in emergency situations.

Adequate preparation will help to reduce the risk of patients with a difficult airway to suffer anaesthesia related damage during the course of the surgical intervention. If in a patient problems with airway management are known or suspected, information about specific risks and treatment strategies should be given. For induction of anaesthesia, an experienced anaesthetist should be present, all required equipment available, and a strategy (see airway management algorithm Figure 1 [Fig. 1]) for airway maintenance should be defined. Preoxygenation should be performed with a tight fitting facemask for at least three minutes. By administering supplemental oxygen whenever possible during the process of establishing a secure airway as well as in the postoperative phase after extubation, the risk of hypoxemia can be reduced further.

2.1.1 Stratregy for airway maintenance

There are several basic management choices when faced with a suspected or known difficult airway: awake fiberoptic intubation vs. induction of general anaesthesia followed by intubation attempts, preservation vs. ablation of spontaneous ventilation, invasive vs. non-invasive techniques for oxygenation and airway maintenance.

2.1.2 Strategy for patients with known/suspected difficult airway

One important strategy to reduce anaesthesia related morbidity and mortality in patients with known or suspected difficult airway is avoiding the necessity for invasive airway management. Local or regional anaesthesia should be preferred when the surgical intervention permits.

Awake fiberoptic intubation with spontaneous ventilation after topical anaesthesia of nose and larynx is the safest method in these patients when intubation is necessary. If the procedure fails due to lack of patient cooperation, presence of anatomical aberrations or massive secretion, the options must be considered (Urgency of surgical intervention? Postponement possible? Invasive airway access necessary?). A surgical airway may be considered first choice in some patients due to the postoperative requirements of airway maintenance.

Before induction of general anaesthesia in these patients the tight seal of the facemask should be checked, as mask ventilation is the first approach at oxygenation when intubation attempts fail. If problems with mask ventilation occur, supraglottic airway devices such as laryngeal mask airway or laryngeal tube should be used for they allow a better airway seal. When intubation difficulties occur, intermittent ventilation via facemask or a supraglottic airway device must be performed to avoid hypoxemia due to repeated intubation attempts.

Whenever the glottis can not be identified, the reason should be identified: Is mouth opening limited? Can the tongue be pushed aside sufficiently? Is identification of the epiglottis possible? Can the laryngeal inlet be identified by directed external manipulation? "Blind" intubation attempts without reliable view of relevant parts of the glottis should not be attempted to avoid trauma and swelling, endangering airway maintenance further.

2.1.3 Life-threatening situations

The presence of a preformulated strategy to ensure oxygenation of the patient and airway maintenance is mandatory in all situations requiring urgent intubation.

The anaesthetist can face two different scenarios: patients with severe obstruction of the airway, cyanosis and/or hypoxemia on first encounter that cannot be ventilated with a facemask or intubated (combination possible: "cannot ventilate, cannot intubate"). In other patients, general anaesthesia is induced and the anaesthesia team is surprised by difficulties because predictive signs are missing or were overlooked.

The strategy for emergencies should be basically the same as above, but the choice of techniques should be limited to those that the medical personnel involved are most acquainted with. In any patient requiring urgent oxygenation, supraglottic airway devices should be considered early due to the better separation of respiratory and alimentary tract when compared to mask ventilation. Fiberoptic intubation via supraglottic airway devices can be an option after ventilation and oxygenation are assured. Many surgical procedures in fastened patients can be performed with ventilation via laryngeal mask airway or laryngeal tube, making additional intubation attempts dispensable. However, if ventilation problems are caused by glottic obstruction (tumor, edema), supraglottic airway devices cannot reliably secure the airway. In these cases, tracheostomy, cricothyrotomy or translaryngeal jet ventilation should be considered. Close cooperation with the ENT specialists will allow further risk reduction when a surgical airway is (or maybe) necessary.

2.1.4 Extubation of the difficult airway

Different factors influence the strategy for further treatment of the patient after successful management of the difficult airway: the patient´s condition, the surgical intervention, documented or suspected trauma of the upper airway. While removal of the tracheal tube will not be a problem, reinsertion in case of any airway obstruction will as a rule be more difficult than the initial intubation.

As soon as airway maintenance was achieved in a patient with a difficult airway, the equipment must be rechecked and completed as necessary to allow adequate reaction in case of peri- or postoperative airway problems. To reduce mucosal swelling, the use of steroids and nonsteroidal anti-inflammatory drugs (e.g. diclofenac) is recommended. This co-medication has been established as a standard in the own department for all patients undergoing surgery for therapy of sleep-related disorders.

Patients with a difficult airway must be awake and communicative for extubation. Protective airway reflexes must have returned, and spontaneous ventilation must be sufficient with tidal volumes resulting in adequate oxygenation. After profound suctioning, the cuff of the tracheal tube should be deflated and the tube should be closed to test whether swelling may lead to airway obstruction after tube removal. If no breath sounds are audible around the tube, there is a high risk that the patient can not be ventilated sufficiently after extubation. Under those circumstances, the patient should remain intubated, and the patient should be taken to the intensive care unit where measures must be undertaken to reduce mucosal swelling. With persisting edema in the upper airways, tracheostomy must be considered. In all patients with breath sounds audible around the tube, extubation can be performed when the criteria above are met. All material for airway management as well as the personnel must be present during this phase.

2.1.5 Documentation

All problems during airway maintenance should be adequately documented in the patient´s chart. The patient should be informed about the problem, and an anaesthesia pass should be issued. The information should be included in the discharge letter to ensure availability of these relevant facts for future surgical interventions.

2.2 Preoperative evaluation

As in any patient seen preoperatively by an anesthetist, diligent patient history and clinical examination offer the most reliable informations concerning the anesthesia-related risk during the surgical intervention [14]. As mentioned above, in OSA patients special consideration should be given to signs of difficult intervention: compared to the general population, the Mallampati score is higher, neck circumference is wider, and mobility of the cervical spine is reduced [15].

ECG and chest x-ray should be requested only when indicated. In patients with sleep apnea syndromes, the ECG can be helpful when signs of ventricular hypertrophy or coronary heart disease are present. A chest x-ray can show signs of cardiomegaly or dilation of pulmonary arteries. When blood tests are ordered, parameters pertaining to polycythemia should be obtained.

Additional diagnostic procedures (echocardiographia, pulmonary function, blood gas analysis) should be ordered, when clinical examination produces pathological findings and when consequences for perioperative management can be expected from these additional tests. Pulmonary function and blood gas analysis are normal in most patients with OSA. In patients with a central sleep apnea syndrome (Pickwick syndrome), blood gas analysis can be helpful to judge the likelihood of the need for postoperative ventilatory support.

2.3 Co-medication

Continuation or interruption of the patient's chronic drug therapy is oriented on general principles. As mentioned above, specific medication for treatment of OSA is infrequently used.

Concomitant diseases must be adequately treated. As in all patients with signs of coronary heart disease or other cardiac impairments undergoing anesthesia for surgical interventions, the indication for beta blockers should be seen liberally to reduce the risk of cardiovascular complications not only during the procedure, but also in the 48 hours following the intervention.

2.4 Choice of narcotics

Some general considerations should be made to choose the drugs for preoperative, intra- and postoperative treatment. In general, short-acting and controllable substances should be preferred to avoid postoperative complications. Relative overdosing of opioids and/or muscle relaxants can lead to respiratory incidents in the early postoperative phase.

2.4.1 Premedication

Routine use of sedatives, especially benzodiazepines must be weighed up against the risks: increased OSA symptoms versus reduction of sympathetic nerve system activation. In the own department, midazolam (3.75 to 7.5 mg) 30 minutes preoperatively are frequently used. In obese patients or when signs of oesophageal reflux are present, antacids and protone pump inhibitors should be considered.

2.4.2 Anaesthetics and sedatives

Even in healthy individuals, midazolam can lead to central and obstructive apnea phases. For other benzodiazepines, inhalational agents and intravenous anaesthetics, reduction of oropharyngeal muscle tone could also be demonstrated [16], [17]. In OSA patients, an increase in symptoms following anaesthesia using these substances can be expected.

2.4.3 Opioids

The dose related risk of apnea phases is a side effect of all opioids. With predisposition in the presence of OSA, the incidence increases. The dose of intraoperative opioids correlates well with the rate of upper airway obstructions following extubation [10]. Nitrous oxide and inhalational agents can be used to reduce opioid requirements.

2.4.4 Muscle relaxants

The oropharyngeal muscles are especially sensitive to non-depolarizing muscle relaxing substances. Even small doses as used for priming can lead to airway obstruction. This also pertains to a residual effect of muscle relaxants in the postoperative phase that my lead to ventilatory distress after extubation. Antagonists should be used when signs of partial neuromuscular blockade are present in the postoperative phase.

2.4.5 Inhalational agents

So far, no correlation could be demonstrated for inhalationals agents and the likelihood of oropharyngeal airway obstruction. Sevorane, isoflurane and desflurane can be used for balanced anaesthesia in OSA patients. By reduction of required opioid doses, the risk of postoperative apnea phases can be reduced.

2.4.6 Local anaesthetics

The use of local anaesthetics in the oropharynx for topical anaesthesia can lead to an increase in length of apnea phases due to reduced activation of pharyngeal mechanoreceptors [18], [19].

2.4.7 Specific intraoperative medication

In interventions for surgical therapy of oropharyngeal obstruction, routine use of steroids and nonsteroidal anti-inflammatory drugs (e.g. diclofenac) has become standard in the own department based on the consideration that surgical therapy will not cause immediate relief of the obstructive symptoms in the immediate postoperative phase but rather cause narrowing of the upper airway by edema and inflammatory reaction.

Since sympathetic nerve system activation is increased in a majority of patients undergoing surgery for reduction of obstructive components, clonidine (alpha adrenoceptor antagonist) is used in the own department. 75 to 150 µg are administered intraoperatively to reduce postoperative distress and episodes of hypertension in the recovery area.

To reduce the risk of postoperative nausea and vomiting (PONV), a potent antiemetic (dolasetron mesilate) is used based on a risk profiling score [20]. Wretching and vomiting are especially unpleasant for patients after oropharyngeal surgical interventions and increase the risk of bleeding.

2.5 Intraoperative monitoring

Extension of routine monitoring with ECG, non-invasive blood pressure, pulse oximetry, capnography and relaxometry should be considered based on the individual patient's risk profile. Invasive blood pressure monitoring offers advantages when high hemodynamic stability is called for due to underlying cardiovascular disorders. In addition, arterial blood gas analysis can be helpful especially in patients suffering from central sleep apnea syndromes (Pickwick syndrome).

2.6 Choice of anaesthesia technique

As mentioned in the section on airway maintenance, the least invasive anaesthesia technique should be chosen. Whenever possible, regional anaesthesia should be used. If additional sedatives are used for regional anaesthesia, the risk of reduced oropharyngeal muscle tone that can lead to apnea phase must be considered [21].

2.7 Specific measures

A second peripheral venous access has proofen to be valuable in the own department. Since the patients should be rather awake for extubation to allow judgement of protective airway reflexes, involuntary reactions and movements that can lead to dislocation of a peripheral line are common. If problems occur after extubation (up to the need for immediate re-intubation), a secure i.v.-access is mandatory.

The use of an oropharyngeal Guedel airway has been established to avoid occlusion of the endotracheale tube by biting before extubation. The negative pressure caused by massive ventilatory efforts against a closed airway in this situation, but also during airway obstruction triggered by anaesthetic agents can lead to a massive pulmonary edema in the postoperative phase (Low pressure pulmonary edema, Figure 2 [Fig. 2]).


3. Postoperative phase

As soon as the patient has been returned to the bed, an elevated position of the upper body portion should be aimed for to increase pharyngeal diameter and residual functional capacity. CPAP therapy should resumed as soon as possible. This can be a reasonable measure in the recovery area when the patient is still sleepy.

Although postoperative episodes of hypoxia can be found up to 5 days after surgery in general anaesthesia, the risk for patients with OSA is low when the principles explained are followed. Close cooperation between anaesthesia and surgical departments leads to considerable risk reduction not only during the immediate perioperative, but also during the postoperative phase.

Early postoperative desaturation is frequently caused by side effects of anaesthetic agents. Late episodes of desaturation are explained by a REM sleep rebound phenomenon in the postoperative phase. Repeated and extended episodes of apnea die to obstruction can lead to pulmonary edema in OSA patients within the first few days following surgery.

There is no evidence that OSA patients need to be monitored in an intensive care or intermediate care unit postoperatively. When the risk profile of the patient calls for diligent monitoring, adequate postoperative placement must be considered. All other patients can be transferred to regular wards if good cooperation of anaesthesia and surgical departments has been established and standards for postoperative care have been defined.

3.1 Postoperative pain therapy

Nonsteroidal anti-inflammatory drugs and regional anaesthesia (depending on the type of surgical intervention) offer the highest level of safety for OSA patients in the postoperative phase. If opioids have to be used for adequate pain therapy, patients must be monitored more diligently.


4. Conclusions

The management of patients with sleep related breathing disorders challenges the anesthetist: the preoperative phase calls for careful evaluation of patients and diligent planning; during the immediate perioperative phase the increased incidence of problems with airway maintenance must be addressed; for the postoperative phase in the recovery area and the wards taking care of further patient treatment, the special needs of patients with OSA must be taken into account.

Close cooperation of anaesthesia and surgical departments will allow safe management of patients before, during and after surgical interventions.


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