|Year : 2008 | Volume
| Issue : 2 | Page : 140-147
Perioperative Management of Patients with Obstructive Sleep Apnoea - A Review
Fauzia A Khan1, Mohammad Ali2
1 Professor, Department of Anaesthesiology, Aga Khan University, Karachi, Pakistan
2 Senior Instructor, Department of Anaesthesiology, Aga Khan University, Karachi, Pakistan
|Date of Acceptance||10-Feb-2008|
|Date of Web Publication||19-Mar-2010|
Fauzia A Khan
Department of Anaesthesiology, Aga Khan University,Stadium Road, PO Box 3500, Karachi 74800
Source of Support: None, Conflict of Interest: None
Obstructive sleep apnoea (OSA) is a sleep disorder of particular concern to anaesthetist. Its exact prevalence is not known but it is said to affect 5% of the population in the west. It is a syndrome characterized by periodic, partial, or complete obstruction of the upper airway during sleep. The diagnostic gold standard is polysomnography.
The anaesthetic implications include the presence of comorbidities like cardiovascular, respiratory and cerebrovascular sequelae. Obesity is a commonly associated condition. Effects of sedatives, hypnotics and other anaesthetic drugs are of major concern and there are potential complications associated with the postoperative period. The purpose of this review is to update the readers on the recent literature available on the topic. The American Society of Anesthesiologists has recently suggested guidelines on the perioperative management of these patients.
Keywords: Obstructive sleep apnoea, Obesity
|How to cite this article:|
Khan FA, Ali M. Perioperative Management of Patients with Obstructive Sleep Apnoea - A Review. Indian J Anaesth 2008;52:140-7
| Introduction|| |
The presence of obstructive sleep apnoea (OSA) presents a major challenge to the anaesthetists. The association of OSA with obesity has long been recognized but the first detailed description of episodic diurnal and nocturnal manifestations of Pickwickiain syndrome were given by Gastaut et al in 1966  . The problem now appears to be more common in general population than originally thought, and this has been confirmed by several epidemiological studies , .
There are anaesthetic implications for preoperative evaluation and medication, intra-operative management, post operative care and pain management in patients with OSA. These patients are likely to have several co-morbidities of importance to the anaesthetist. Patient may also present for surgery without prior diagnosis  . The effects of sedatives, analgesics, and anaesthetics can worsen OSA by several mechanisms and there is increased risk of anaesthetic and post operative complications.
This review will discuss the current definition, incidence, anaesthetic management of the disorder, and availability of current guidelines.
| Definition|| |
There is no broad consensus definition. An attempt was made in 1999 to address this issue  . In this particular report "apnoea" was defined as a cessation of airflow exceeding 10 second duration. "Obstructive sleep apnoea (OSA)" was defined as persistent efforts without air flow. The term "obstructive sleep apnoea syndrome" (OSAS) was applied when OSA was accompanied by day time sequelae e.g. excessive day time sleepiness.
A recent practice guideline by American Society of Anesthesiologists (ASA) defines obstructive sleep apnoea (OSA) as a syndrome characterized by periodic, partial or complete obstruction of the upper airway during sleep  .
| Incidence|| |
The epidemiological data shows the prevalence of OSAS at about 5% in general population in western countries  and 1-9% in surgical patients  . Eighty to 90% of patients probably, still remain undiagnosed  . The incidence is higher in males, obese patients and in patients with upper airway malignancies  . In a recent survey of Canadian anaesthesiologists, 67% of respondents provided perioperative care to one to five OSA patients per month  .
The incidence data from the subcontinent is scarce. One study from Delhi, reports the incidence of OSA to be 13.7%, and for OSA syndrome as 3.57%  . Another from Mumbai reports a higher incidence of OSAS of 7.5%  . A preliminary study from Karachi, Pakistan reports the incidence in one centre to be the same as in the west, in patients studied in a sleep lab  .
| Brief pathophysiology|| |
A narrow and floppy upper airway is the basis of OSA. Sleep specially rapid eye movement sleep makes the airway more floppier and narrower due to muscle relaxation, resulting in partial or complete obstruction  . Each cycle is followed by arousal, and in severe cases this scenario is repeated hundreds of times every night. These repeated cycles of hypoxemia and hypercarbia may result in several potential sequelae like pulmonary hypertension  , systemic hypertension, ischemic heart disease, right heart failure  , gastro-oesophageal reflux, intra-cranial hypertension  , polycythemia and right heart failure, all of which are of potential anaesthetic significance.
| Pre-operative screening for OSAS|| |
Early identification of OSAS is important in the surgical patient population. A recent publication by Kaw et al recommends that heavy snoring, sudden awakening from sleep with a choking sensation and witnessed apnoea by a bed partner should be a routine component of the pre-operative visit  . ASA guidelines  recommend history of snoring, headaches, and day time somnolence in addition to above. Physical examination may reveal associated features like nasal obstruction, tonsillar hypertrophy, retrognathia and obesity. These features may not be a reliable predictor of the severity. In addition to airway assessment physical examination should include neck circumference and tongue volume.
Polysomnography still remains the gold standard for diagnosing the disorder if feasible in a given clinical situation. Alternative screening tools like overnight oximetry have been explored by some authors . Nocturnal oximetry only identified one third of those who experienced post operative complications  . A study by Fidan et al recommends polysomnography in all surgical patients who have two or more major symptoms of OSA present  . Nasopharyngoscopy is sometimes performed to assess the benefits of surgery  .
If sleep studies are available, the results of the sleep lab assessment in terms of mild, moderate or severe disease should be used to determine the anaesthetic management  . Scoring systems to estimate peri-operative risks have been proposed but not validated  . In case of diagnosed sleep apnoea the severity of apnoea, treatment received and patient's compliance with the treatment and complications of OSA should be reviewed.
If the patient is suspected to have OSA and sleep studies are not available or the surgery is emergency, patients should be treated as though they have moderate sleep apnoea  .
Anaesthetic management should be carefully planned in consultation with the surgeon.
| Preoperative preparation|| |
The recommendation of the American Society of Anesthesiologists state that preoperative continuous positive airway pressure (CPAP) should be considered in severe OSA and in patients who do not respond to CPAP, non invasive positive pressure ventilation (NIPPV) is of benefit  .
Patients who have had prior corrective surgery e.g. uvulopalatopharyngoplasty should still be assumed at higher risk until a normal sleep study pattern has been obtained. Weight loss should be considered when feasible.
| Premedication|| |
Preoperative sedation with benzodiazepines for anxiolysis may cause considerable relaxation of the upper airway musculature. It causes an appreciable reduction of the pharyngeal space which may lead to a higher risk of preoperative phases of hypopnoea and consecutive hypoxia and hypercapnia , . Oxygen saturation needs to be monitored during preoperative period and patient should be kept in a monitored area. In patients on CPAP there is no real contraindication to premedication as their CPAP may be applied if they get sleepy and oxygen can be added if necessary  .
Many patients with OSA are morbidly obese. This places them at increased risk for aspiration of acidic gastric fluid at the time of induction of anaesthesia. These patients should receive medications to suppress gastric acid production, neutralize the acid, or to stimulate emptying of the stomach  .
| Perioperative management|| |
The anaesthetic care of patients with OSA is challenging because anaesthetic drugs profoundly influence control of an already dysfunctional respiratory system, and presence of significant co-morbidities. Hypertension and cardiovascular diseases is more common often than other patients  .
No evidence exists regarding perioperative risk in patients with sleep apnoea whether it depends on the type of anaesthetic technique employed  . It is generally believed that regional anaesthesia (RA) is preferable over general anaesthesia (GA) whenever possible. Regional anaesthesia minimally affects respiratory drive and can reduce the effect of anaesthetic agents on subsequent sleep patterns as well as maintain arousal responses during apnoeic episodes. Regional anaesthesia may obviate the need for sedative and opioid drugs both intraoperatively and postoperatively  . One should be ready for airway management because the regional technique may result in unconsciousness or respiratory paralysis unintentionally  . Landmarks may be difficult to identify if the patient is obese.
If general anaesthesia is the only option, controlled ventilation with tracheal intubation should be the choice. There is compelling evidence in the literature that obese OSA patients are, in general, more difficult to intubate than normal controls. Obesity, short thick neck and excess pharyngeal tissue deposits in the lateral pharyngeal walls are causative factors for difficult intubation. Benumof recommends that all patients who have a trachea that is difficult to intubate should be regarded as having OSA until excluded by clinical features and, where doubt exists, sleep studies  .
| Intubation technique|| |
The equipment for management of a difficult airway should be in place before induction of general anaesthesia. Orotracheal tubes in various sizes, gum elastic bougie as well as a McCoy laryngoscope and a laryngeal mask airway are necessary. Fibreoptic devices may be helpful but have no impact in acute emergency situations. A strategy or algorithm for establishing a secure airway should be defined. With the increased index of suspicion of difficult intubation in patients with OSA, the decision to do tracheal intubation with the patient awake or under general anaesthesia must be individualized on the basis of a complete preoperative airway evaluation. If difficulty with either mask ventilation or tracheal intubation is expected, then, according to the ASA Difficult Airway Algorithm, intubation and extubation should be performed while the patient is awake .
If tracheal intubation is to be done while the patient is awake using flexible fiberscope, it is essential that the patient be properly prepared by topical and nerve block anaesthesia of the upper airway.
If intubation is to be done with the patient asleep, the patient should be fully preoxygenated because an obese patient with a relatively small functional residual capacity (FRC) and high oxygen consumption desaturates much more rapidly during obstructive apnoea than does a normal patient  . Effective preoxgygenation is achieved by delivering FIO2 = 1.0 for more than three minutes duration with a properly sealed face mask  . Oxygen insufflation into the pharynx via a small nasopharyngeal catheter during laryngoscopy of the obese patient may further delay the onset of arterial oxygen desaturation  .
Patient should be in sniffing position before induction of GA. Use of optimal external laryngeal manipulation during laryngoscopy may improve the laryngeal view  . Mask ventilation may require two anaesthesia providers. The airway pressure relief valve and mask seal should be set in a way to deliver CPAP (5-15 cm H2O)  .
In the context of difficult airway one should be ready for "cannot ventilate, cannot intubate" situation. Equipment (cricothyrotomy set, jet ventilator) and personnel (ENT surgeon) to deal with this situation should be readily available.
| Rapid sequence induction in sleep aponea|| |
In a recent review article, Freid concluded that rapid sequence induction remains important in obese and sleep apnoea syndrome patients with symptomatic gastroesophageal reflux or other predisposing condition such as diabetes mellitus, pregnancy, emergency surgery, and gastrointestinal conditions. In the case of elective surgery in a fasted patient with no risk factors other than obesity or sleep apnoea syndrome, the requirement for rapid sequence induction is debatable. Cricoid pressure is probably efficacious but has not been proven in a randomized, controlled trial to prevent gastric aspiration. The clinician should be aware of the possibility that cricoid pressure will worsen mask ventilation and laryngoscopy and be prepared to loosen or release the pressure if mask ventilation or intubation is compromise  .
| The effect of anaesthetic drugs|| |
There is evidence that many anaesthetic agents cause exaggerated responses in patients with sleep apnoea. Drugs such as thiopentone, propofol, opioids, benzodiazepines, and nitrous oxide may reduce the tone of the pharyngeal musculature that acts to maintain airway patency , .
The choice of induction and maintenance agents is probably not important although it would seem sensible to avoid large doses of longer acting drugs, especially neuromuscular blocking agents. Anaesthesia techniques using shorter acting drugs are attractive because it would be reasonable to expect a more rapid return to baseline respiratory function when shorter-acting drugs are used. Opioids should be used judiciously although the availability of CPAP will obviate potential difficulty postoperatively, particularly if the patient is already familiar with it  .
| Intraoperative monitoring|| |
There is no evidence to suggest that patients with OSA need more aggressive, intensive, or invasive intraoperative monitoring than normal patients. The intensity of monitoring should be dictated by the type of surgery planned and by the presence of other co-morbidities. If the patient with sleep apnoea is morbidly obese, an intra-arterial catheter may be necessary if noninvasive blood pressure monitoring is unreliable or not feasible for technical reasons
| Extubation|| |
Depending upon surgical procedure, condition of the patient and any documented or suspected trauma to the upper airway due to airway manipulations, leaving the patient intubated for a short period of postoperative mechanical ventilation should be considered.
Whenever the patient is to be extubated (either in the operating room or later in the recovery room or ICU), the patient should be fully awake. Full recovery from neuromuscular blockade should be proven by a neuromuscular blockade monitor, sustained head lift for 5 seconds and, in the ICU, with an adequate vital capacity and peak inspiratory pressure. The patient should not have a high blood level of opioid as indicated by a respiratory rate less than 12-14 breaths/min while the endotracheal tube is in situ. It is helpful for regional analgesia to be operative at the time of extubation  .
Extubation in the reverse Trendelenburg or semiupright position minimizes compression of the diaphragm by abdominal contents  .
| Postoperative care|| |
There are multiple issues regarding postoperative care of OSA patients which need to be addressed.
| Patient positioning|| |
The elevated head side position to 30° should be used for the OSA patient at all times while in the post anaesthesia care unit (PACU) and throughout his or her hospital stay. Upper body elevation relieves OSA by increasing the stability of the upper airway  . Loadsman suggested a lateral posture during postoperative care for a particular tendency to upper airway obstruction during supine position  .
| Postoperative complications|| |
These patients are more prone to have respiratory (episodic desaturations, hypercapnoea, re-intubations) and cardiovascular (hypertension, arrhythmia, myocardial ischaemia and infarction) complications in postoperative period. These risks are associated with OSA-related as well as non-OSA surgeries. Gupta et al found a twofold increased risk of developing complications in patients with obstructive sleep apnoea who had knee or hip surgery compared with patients without obstructive sleep apnoea after the same operations. Use of nasal continuous airway pressure preoperatively and postoperatively greatly reduced this complication risk  .
| Role of CPAP|| |
Nasal continuous positive airway pressure (NCPAP) should be applied if airway obstruction is persistent despite proper positioning of the patient and nasophryngeal airway. Rennotte et al found that N-CPAP started before surgery and resumed immediately after extubation allowed to safely manage a variety of surgical procedures in patients with OSAS, and to freely use sedative, analgesic, and anaesthetic drugs without major complications. They recommended that every effort should be made to identify patients with OSAS and institute N-CPAP therapy before surgery  . Oxygen can be added to CPAP treatment. The most economical place to add it is via a side port on the CPAP mask where relatively low flows (2-4 liter /min) can produce a high FIO2. This addition does not change the CPAP pressure supplied by most modern machines . During CPAP therapy patients may need direct supervision while they are sedated and not familiar with its use, until they are capable, unaided, of applying their therapy correctly. It may need high dependency unit admission for few days  .
| Location of patient|| |
It is important that the patient with OSA is nursed in the appropriate postoperative environment. This issue is closely related to the patient's analgesic requirements.
Factors to be considered for decision about location of postoperative care are the body mass index (BMI) of the patient, the severity of the OSA, the degree of associated cardiopulmonary disease, intraoperative complications and the postoperative opioid requirement. When all of these factors are mild, then the patient may go to a relatively unmonitored environment. When any of these factors are severe, the patient should go to an intensive care unit (ICU). The large gray zone in between these extremes requires careful judgment. The most suitable postoperative environment is also determined by the particular conditions within each hospital , .
| Role of nasal obstruction|| |
Presence of nasogastric tubes and nasal packing after nasal surgery may pose an extra risk. The presence of a nasogastric tube does not preclude the application of CPAP as the nasal mask can be applied over the tube, which runs under the mask cushion, but leakage and comfort may be a problem. After nasal surgery a nasopharyngeal airway may be passed and the surgeon may pack the nose around it, although it may have limited calibre. In such cases full face continuous positive airway pressure is needed to prevent dangerous apneas , . If serious compromise of upper airway patency is anticipated after upper airway surgery then undue reliance on CPAP is inappropriate. The patient may require prolonged tracheal intubation or, where several days or more of airway compromise is anticipated, tracheostomy should be considered  .
| Postoperative analgesia|| |
The provision of adequate postoperative analgesia is an integral part of the anaesthetic plan. Multimodal analgesia is preferable wherever possible. Obese OSA patients have an increased risk of opioid induced upper airway obstruction. Sedation and narcotic-based analgesia may exacerbate symptoms of sleep apnoea resulting in respiratory depression and respiratory arrest even if given intramuscularly, epidurally or via patient controlled analgesia  . There are no adequately powered studies to guide analgesic therapy of these patients. If narcotics are required for pain control then patient controlled analgesia with no basal rate and restricted dosing may help to limit dosing  .
The use of nonsteroidal anti inflammatory drugs, local anaesthetics for incision infiltration, epidural analgesia and peripheral nerve blocks, when appropriate, can minimize the necessity for the administration of large doses of narcotic drugs to achieve adequate analgesia ,.
| Sleep apnoea syndrome in children|| |
The symptoms, polysomnographic findings, pathophysiology and treatment of Obstructive Sleep Apnoea (OSA) in children are significantly different from those seen in adults. It is most commonly associated with adenotonsillar hypertrophy  . Preanaesthesia screening should routinely include a detailed birth and medical history, growth assessment, review of systems for recent respiratory infection, behavioral issues, and school performance. Troublesome behavior often can be addressed by the relief of SA  .
| Premedication|| |
Cultrara and colleagues after a retrospective study suggested that preoperative sedation might be safely administered to children with mild or moderate sleepdisordered breathing, and possibly to children with severe obstructive sleep apnoea (OSA), if children are closely observed prior to surgery. They recommended further prospective studies to confirm their results . Francis et. al in a recent study of 70 children, premedicated with midazolam (0.5 mg.Kg -1 ) planned for adenotonsillectomy for treatment of sleep-disordered breathing concluded that many of these children may safely be pre- medicated . Antireflux medications and antisialagogue drugs are important adjuncts to be considered for the prevention of aspiration and laryngospasm 
| Perioperative management|| |
Both inhaled and intravenous anaesthesia should be carefully titrated to the effect, particularly when used in combination. Children with OSA show an exaggeration of the blunted respiratory drive in response to opioid and benzodiazepine administration  .
Hullett et al compared tramadol with morphine in adenotonsillectomy for OSA in children. They found that children in tramadol group had fewer episodes of desaturation (<94%) in postoperative period therefore they recommended the use of tramadol for this procedure in children with OSA  .
Luscre et al recently described a case series of three children with OSA given monitored anaesthesia care with a combination of ketamine and dexmedetomidine during magnetic resonance imaging. This combination provided effective sedation with no clinically significant haemodynamic or respiratory effects  . Difficult airway may also be anticipated in children with OSA because of craniofacial or known anatomical airway abnormalities. Skilled clinicians and the equipment for managing a difficult airway, such as a fiber-optic laryngoscope as well as a laryngeal mask airway, also should be readily available. Jaw thrust to treat airway obstruction in these patients is the most useful and is superior to the chin lift  .
The greatest concern when extubating a child from deep anaesthesia is laryngospasm. When possible, children with OSA are extubated when they are fully awake. 
| Postoperative care|| |
During the postoperative period, children with OSA are at risk for respiratory failure because of increased episodes of apnoea from baseline, acute airway obstruction, atelectasis, and postobstructive pulmonary edema. Risk factors for respiratory distress after surgery for OSA are, age less than 3 years, bleeding, concurrent respiratory infection, congenital heart defects, craniofacial disease, failure to thrive, history of cor pulmonale, history of premature birth, neuromuscular disease, obesity, other congenital abnormalities or genetic syndrome and severe obstructive sleep apnoea .
Nixon and colleagues reported that despite removal of obstructing lymphoid tissue, upper airway obstruction occurred on the first postoperative night in children with OSA  . Friedman et al have reported success using bilevel nasal CPAP immediately after tonsillectomy and adenoidectomy in children with severe OSA  .
Children who have a history of pulmonary hypertension and cor pulmonale also may be at risk for circulatory failure.
Children with severe OSA or cardiovascular disease should be monitored after surgery in the pediatric intensive care unit. Most children with mild to moderate OSA, however, do not require postoperative monitoring in an intensive care unit  .
| Recent reviews and guidelines|| |
There are some published reviews on the anaesthetic management of OSA in recent literature (2005 onwards). Passannante et al  reviewed the general anaesthetic management of OSA patients in adults and Bandla et al  in children. Bell et al  reviewed the post operative complication in these OSA patients. All these reviews were published in the Anesthesiology Clinics of North America.
Kaw et al  reviewed the perioperative implications for the sleep apnoea surgical patient in the journal, Chest and Mickelson et al  reviewed the pre and post operative management of OSA patients in Otolaryngologeal Clinics of North America (2007).
The only available consensus guidelines are by the American Society of Anesthesiology Task force on the perioperative management of OSA patients which was published in 2006 in Anesthesiology  .
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