OSA Overview

Central sleep apnea (CSA) occurs when the muscles of respiration fail to act, though the airway remains open. This form of SDB affects only 5-10% of the sleep apnea population. Complex and mixed apnea (CompSA) is a combination of OSA and CSA.
Obstructive sleep apnea is the most common form of sleep apnea. Approximately 1 in 5 patients have mild OSA 1 in 15 have moderate to severe OSA.

Apnea is defined as a cessation of airflow for 10 seconds or longer. Hypopnea is a decrease in airflow lasting > 10 seconds with a 30% reduction in airflow and with at least a 4% oxygen desaturation. The Apnea Hypopnea Index (AHI) is determined during a sleep study and is defined as the number of apneas and hypopneas that occur per hour of sleep and typically reflects the severity of the SDB. An AHI of 5 to 14 events per hours is considered mild, 15-30 events is considered moderate, and any greater than 30 events per hour is considered severe.

Clinical signs and symptoms of Sleep Apnea are marked by excessive daytime sleepiness, loud snoring, witnessed apneas, nocturnal choking and coughing, restless sleep/heavy sweating as a fight or flight response resulting in increase strain on your muscles from arousals. In addition, OSA patients often suffer from morning headaches caused by nocturnal hypoxia.

Hypertension
With repeated apneas throughout the night, the blood becomes hypoxic and is insufficient for the heart to work/pump properly which can cause a back up of blood in the right side of the heart causing the sympathetic nervous system to go into “overdrive.” The muscles contract, which causes the para-sympathetic nervous system to slow down and the sympathetic nervous system to surge (happens many times through night), and we see an increase in Sympathetic Nerve Activity. This causes blood pressure to drop very low then shoot up increasing to an unhealthy level. We see this high BP sustained in the daytime. High BP is said to have a dose- response relationship with sleep apnea (Lavie et al. Obstructive sleep apnoea syndrome as a risk factor for hypertension: population study. BMJ 2000;320:479-483) and Impotence - Male hormones are typically released during slow wave sleep (stage 3-4); if you never achieve stage 3-4 sleep because you have apneas, you would release insufficient levels of hormones (Goncalves et al. Erectile dysfunction, obstructive sleep apnea syndrome and nasal CPAP treatment. Sleep Med 2005;6(4):333-339)

Surgical Risks
The administration of medications commonly used in anesthesia, sedation, and analgesia can result in airway obstruction in all patients, but patients with OSA are at greater risk. Anesthesia removes a person’s ability to maintain their vital functions and reflexes. Through the use of narcotics and fluorinated inhalations agents, autonomic reflexes are blunted, patients become unresponsive, airways obstruct and ventilator control becomes reflexive. The result is cardiovascular instability, partial or complete airway obstruction, and dampened ventilatory drive. The use of paralytics only compounds these problems by causing complete relaxation of the pharyngeal muscles and atonicity of the diaphragm. The result is a floppy, unprotected airway and no independent ventilation. The anesthesiologist is trained to induce an adequately deep plane of anesthesia (induction), support the vital systems while a patient is anesthetized (maintenance) and to wake the patient up at an appropriate time (emergence). It is during both induction and emergence that problems arise with patients who have OSA.

Residual anesthetic agents combined with narcotic analgesia can compromise the patient's airway. Patients with OSA often have airways that are difficult to manage both on induction and on emergence from general anesthesia.(20) Cardiac arrhythmias are common during this time, with sinus arrhythmias occurring most commonly.(21) In addition, patients are often given narcotic analgesics to control pain postoperatively and are often sent home completely unmonitored with their analgesics. Should an obstructive apneic event occur in these unmonitored conditions, the narcotic analgesic may leave the patient unable to arouse enough to resume breathing.

Numerous studies confirm the importance and complexity associated with perioperative management of sleep apnea patients to minimize the risks of postoperative respiratory complications. Statistics show that more than 20% of elective surgery patients are at risk for OSA.1 (1 Yuan et al, University Health Network, Pre-operative Risk of Sleep Apnea in Elective Surgical Patients). Because the overwhelming majority of sleep apnea cases have not been identified, it is crucial that hospital staff learn to effectively identify this condition and properly monitor affected patients perioperatively, as well as to recognize the implications and appropriate care of OSA patient in their care. In addition, many sleep apnea sufferers are unaware of their condition, thus it is not sufficient simply to ask if a patient has sleep apnea. Instead, health care professionals must ask proper screening questions of their patients, especially those individuals at risk for sleep apnea and those children undergoing a tonsillectomy and adenoidectomy, before making decisions on patient care.

In response to the associated risks and adverse reports, guidelines and recommendations featuring the management of sleep apnea patients are emerging quickly. The American Society of Anesthesiologist developed guidelines that were approved at a 2005 annual ASA meeting and focused on the importance of managing sleep apnea patients preoperatively.

The purpose of ASA guideline is to improve the perioperative care and reduce the risk of adverse outcomes in patients with OSA who receive sedation, analgesia or anesthesia for diagnostic or therapeutic procedures. The ASA stated that the guidelines should be implemented on patients who are judged to be at the greatest risk, apply to both inpatient and outpatient settings, apply to procedures performed in the operating room and other locations where sedation or anesthesia are administered. In addition, after pre-op evaluation, the anesthesiologist and surgeon should jointly decide whether to:

– Manage the patient perioperatively based on clinical criteria alone
– Obtain sleep studies or conduct a more extensive airway examination, and initiate indicated OSA treatment in advance of surgery

² (2 Report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Obstructive Sleep Apnea)
Furthermore, the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has also highlighted the importance of ensuring the safety of sleep apnea patients in the perioperative setting. The Joint Commission released for review a list of DRAFT Goals and Requirements that were considered for potential inclusion in the 2008 National Patient Safety Goals. One of the draft goals included requiring organizations to reduce the risk of post-operative complications for patients with obstructive sleep apnea
In the future it is believed the JCAHO will introduce National Patient Safety Goals regarding the perioperative management of OSA patient.

How can you protect your patients?
Many hospitals have already developed and introduced a screening process and perioperative management protocol to identify OSA patient preoperatively, monitor and often treat OSA patients postoperatively. It is important to learn from others, but do what works for your institution and your physicians to be successful. The first step is to establish a multidisciplinary team to assess the risk in your organization and develop a method to identify surgical patients with sleep apnea and modify their care to ensure the patient’s safety. Preadmission screening and testing provides the opportunity to help identify OSA patients before an adverse event occurs. It is recommended that anesthesiologists should work with surgeons to develop a protocol whereby patients in whom the possibility of obstructive sleep apnea is suspected on clinical grounds are evaluated long enough before the day of surgery to allow preparation of a preoperative management plan.
• Manage the patient preoperatively based on clinical criteria alone
• Obtain sleep studies and initiate indicated OSA treatment in advance of surgery
• In either situation consider:
– Severity of OSA
– Invasiveness of procedure
– Postoperative requirements of narcotics
There are many effective tools available to identify patients at risk for OSA. The Berlin Questionnaire is a tool used in recent studies. The questionnaire is self-administered, comprised of ten questions, to identify patients and assesses, presence and frequency of snoring behavior, wake-time sleepiness or fatigue, history of obesity and/or hypertension
Patients with persistent and frequent symptoms in any two of the three risk categories are considered “high risk” and should be followed up with diagnostic testing for OSA 3 published studies using the Berlin questionnaire demonstrated 18-27% of elective surgical patients at high risk for OSA
– Berlin Questionnaire identified 26.7% at high risk for OSA; n=5921 (Yegneswaran et al, Univ of Toronto; ASA 2006)
– Berlin Questionnaire identified 24% at high risk for OSA; n=318; elective surgery in general, ortho, urology, plastics, ophthalmology and neuro2 (2 Yuan et al, University Health Network, Pre-operative Risk of Sleep Apnea in Elective Surgical Patients)
– Modified Berlin identified 18% at high risk for OSA; n=2687; 80% confirmed by home diagnostic PSG3 (3 Finkel et al, Washington Univ in St Louis, ASA 2006)
Preoperative evaluation should include a medical record review, patient and family interview, physical examination and often may even include a screening using an objective screening device or a formal sleep study in the lab if time permits.

Perioperative management of the sleep apneic patient also includes close physical monitoring, including cardiac monitor and pulse oximetry in order to quickly recognize when and if the patient experiences some form of respiratory compromise associated with the administration of anesthesia, opiates and sedatives , until the patient is extubated and fully awake. Often, hospitals mandate extended PACU and/or Outpatient stays are necessary to ensure patient safety and prevent adverse events post discharge. In many cases, the anesthesiologist will minimize the opiates given during procedure.

In addition to preoperative screening, patient monitoring and perioperative treatment, it is important for the patient to get formally diagnosed and treated for OSA upon discharge. Diagnosing and treating OSA improves quality of life for patients, reduces health care costs and reduces long-term morbidity and mortality. In addition, many studies show that early treatment with CPAP reduces the need for intubation, the ICU length of stay and the incidence of pneumonia, infection, and sepsis in patients who develop acute hypoxemia after elective abdominal surgery. (Duggan M and Kavanagh BP. Pulmonary atelectasis. Anesthesiology 2005; 102:838854). One study demonstrated that the intubation rate in the group of patients treated with oxygen plus CPAP was lower than in the group of patients treated with oxygen alone. Accordingly, several studies have shown that, in patients with postoperative hypoxemic respiratory failure, CPAP improves gas exchange, minimizes atelectasis formation, and increases functional residual capacity FRC.

Because of the known benefits of postoperative CPAP treatment, hospitals with a perioperative management advise patients who use CPAP to use their device continuously until the morning following surgery; for discharge to hospital, consider initiation of CPAP in postoperative period; for discharge to home, monitor the patient at least 2 hrs after last IV or IM narcotic prior to discharge.

Conclusions
• OSA is an independent risk factor for postoperative complications
• Make preoperative screening for OSA routine
• Complications likely can be minimized with pre- and postoperative protocols
• Further research is needed to improve screening and optimize postoperative care
• Multidisciplinary collaboration is needed to improve patient safety