Authors

1. Newsom, Cresilda RN MSN CCRN CPAN
2. Brennan, Patricia RN PhD

Abstract

Review question/objective: The objectives are to evaluate whether the use of dexmedetomidine in obstructive sleep apnea patients decreases:

a) respiratory adverse events,

b) overall use of narcotics,

c) and pain levels

Background: Obstructive Sleep Apnea (OSA) is a common sleep-related breathing disorder and its prevalence has been increasing throughout the world because of obesity and the increasing age of the general population.1 Pharyngeal occlusion associated with intermittent hypoxia and sleep disruptions are classic signs of obstructive sleep apnea.2 During sleep, an occurrence of airway obstruction with periods of apnea lasting 10 seconds or more for five or more times per hour will result in a diagnosis of OSA.3 Lack of knowledge about the disorder, OSA is frequently undiagnosed even with its high prevalence in western society.4 In the perioperative period, patients with OSA are at increased risk of several complications due to hypoxemia from prolonged periods of apnea; complicated intubation due to abnormal neuromuscular tone; redundant soft tissue or an increase in upper airway adipose tissue; and a delay in postoperative recovery due to repetitive episodes of upper airway obstruction.5 Morbidly obese patients have a higher incidence of OSA and potentially decreased tissue oxygenation. This inadequate post-operative ventilation may increase the risk of morbidity and mortality.6 Due to the depressing effects of opioid narcotics on the OSA patient's ventilation, avoiding the use of narcotics and using alternative types of analgesics or sedatives must be explored. Since most patients with sleep apnea are undiagnosed, they face a significant risk especially in the perioperative period. Medications used during surgery including anesthesia and sedation are known to increase the risk of pharyngeal collapse, decreased ventilatory response, and impaired arousal response which can lead to increased episodes of sleep apnea, especially in the perioperative period.7

Several population-based cohort studies conducted in the United States, Europe, Australia and Asia have documented a high prevalence of OSA across a wide spectrum of severity in adults.8 A study by Young et al. reported the prevalence rates of OSA in the middle-aged population to be as high as 20-30%. Notably, it is estimated that 82% of men and 93% women who suffer from moderate to severe sleep apnea are undiagnosed.9 Obesity, diabetes, race, heredity, ethnicity, smoking, and nasal congestion are some of the potential risk factors for OSA.10 Prevalence rates for OSA in African Americans are much higher when compared to Caucasians with a similar body weight, while Asians, despite their lower body weight, have the same prevalence rates of OSA as their North American counterparts.11,12 Wong et al.7 attributed differences in craniofacial structure as a reason for these racial differences. A greater restriction in skeletal measurements including a smaller maxilla, smaller and retro positioned mandible, and a short, steeper anterior cranial base are more common facial features in Asian compared to Caucasian populations.7

Surgical patients with OSA have higher rates of complications depending on the type of surgery. In a study comparing OSA patients with non-OSA patients matched for age, sex, and body mass index (BMI), Squadrone et al.13 found an increased risk of postoperative complications (39% compared to 18%), a higher rate of transfer to ICU (24% compared to 9%), and longer hospital stays for those in the OSA group. The OSA group also showed an overall greater usage of medical resources that resulted in an increased medical burden for OSA patients compared to individuals without OSA.14 This indicates a significant opportunity for cost savings and quality improvement should solutions be identified to address these issues.

Findings derived from the literature suggest that OSA patients should be identified preoperatively and provided the necessary treatment precautions to eliminate perioperative complications and adverse events.15,16 In 2006, the American Society of Anesthesiologists developed guidelines for the diagnosis and management of OSA. A checklist format of 14 categorized questions examining factors that are thought to be present and contributing to OSA were established as a result of these guidelines and examined certain patient physical characteristics, identification of airway obstruction during sleep, and complaints of somnolence. Compared to a sleep study or polysomnography, which is the "gold standard" for diagnosing OSA, the sensitivity of the task force's checklist ranged from 79% to 87%.17 As a result, the STOP-BANG Questionnaire was subsequently developed which is a more efficient, concise screening tool. A 96% sensitivity was found and several studies including a meta-analysis supported and recommended the STOP-BANG as a preoperative screening tool on the basis of its ease of use and excellence in predicting severe OSA.18 Using the STOP-BANG Questionnaire preoperatively, a recent cohort study identified high risk OSA patients as having a higher rate of postoperative pulmonary and cardiac complications when compared to patients who are at low risk for OSA (19.6% compared to 1.3%) including a significantly higher length of hospital stay.19

Due to narcotic pain medications' excellent analgesic effects, opioids remain one of the best postoperative pain treatments available. However, narcotic pain medications, even in small doses, can reduce ventilatory function in patients with OSA and without OSA.6 An alternative way of reducing pain using non-narcotic medications such as dexmedetomidine should be explored in order to reduce opioid consumption and the risk of postoperative complications in the OSA patient population.

Dexmedetomidine (Dex) is a medication that has an analgesic effect without causing any respiratory depression.20 A reduction in norepinephrine release which reduces the heart (HR) and mean arterial blood pressure (MAP) can also be attributed to dexmedetomidine's sympatholytic effect.21 Most often used as a sedative for patients requiring short-term sedation while on mechanical ventilation, Dex is used in intensive care units as a highly selective [alpha]2-adrenergic receptor agonist.22 Its ability to have reduced respiratory side effects is the main reason Dex is used over opioids.

Questions remain on how to effectively manage pain in OSA patients.23 Managing post-operative pain in patients with OSA must be carefully supervised. This includes minimizing the side effects of analgesic treatment, particularly opioids. A multimodal or balanced approach to anesthesia is highly recommended due to the various physiological mechanisms of postoperative pain.24 There are several undesirable side effects of opioids including respiratory depression. In order to improve post-operative outcomes, using opioid-sparing analgesics may prove beneficial. Improved pain control and a decrease in postoperative morphine requirements have been achieved after continuous infusions of dexmedetomidine at rates between 0.4mcg/kg/hr and 0.7mcg/kg/hr.25 Dexmedetomidine, with its opioid-sparing effect, may possibly reduce episodes of apneic events in OSA patients whilst providing adequate analgesia. There is also reason to believe that the use of dexmedetomidine may be associated with fewer postoperative complications and may facilitate recovery after surgery in OSA patients.

Possible outcomes to be measured in this review will include postoperative pain levels as measured by Visual Analog Scores (VAS) 0 to 100, where 0 corresponds to no pain and 100 corresponds to worst possible pain. The use of VAS 0 to 10 will be converted to VAS 0 to 100. The use of verbal or numerical rating scales (NRS) will also be considered and converted to VAS. Apneic or respiratory events will be defined as respiratory rates of less than 8 per minute, and an overall reduction in opioid use will be measured by significant reduction in dose of opioid administered via any route up to 48 hours after end of surgery.

A previous systematic review conducted on sedatives and anesthetics on OSA patients have yielded limited results when the intervention is specific to the use of dexmedetomidine.²⁶ Another systematic review regarding the use of dexmedetomidine is underway however its focus will not be on patients with OSA and the outcomes being measured will be on post operative pain levels alone.²⁷ This systematic review is therefore needed in order to investigate the assumption that dexmedetomidine can decrease the overall use of narcotics and reduce the incidence of apneic events for those who are either diagnosed or who are high risk for OSA patients undergoing surgery.