Literature Updates

Supra-Epiglottic Upper Airway Volume in Elderly Patients with Obstructive Sleep Apnea Hypopnea Syndrome

In this study, the authors compared upper airway volume in elderly patients with OSAS treated with CPAP vs. without CPAP. Sixty elderly volunteers (20 with OSAS, 20 with OSAS treated with CPAP, and 20 controls) underwent MRI. There was no significant differences in supra-epiglottic upper airway volume between OSAS, CPAP treated patients with OSAS and controls. The retropalatal distance and anteroposterior to transverse diameter ratio differed between OSAS, CPAP treated patients and controls. There was a significant correlation between BMI and retropalatal distance.

Pain Intensity and Opioid Utilization in Response to CPAP Therapy in Veterans with Obstructive Sleep Apnea on Chronic Opioid Treatment

This retrospective case-control study compared 113 patients with OSA taking opioids for non-malignant pain vs. a control group of patients with OSA who were not taking opioids at a VA sleep center. Pain intensity was assessed prior to CPAP treatment and at 12-month follow-up. Opioid intake was assessed using the morphine equivalent daily dose (MEDD) and CPAP adherence was assessed. CPAP adherence was lower in opioid treated patients vs. control (37% vs. 55%, p=0.01). Greater pain intensity was associated with CPAP non-adherence. CPAP treatment did not reduce pain intensity of consumption of opioids in veterans with chronic pain and OSA.

Comparison of Sugammadex Versus Neostigmine Costs and Respiratory Complications in Patients with Obstructive Sleep Apnea

In this prospective study, 74 patients undergoing otolaryngological procedures for OSA were randomized to receive sugammadex or neostigmine to reverse neuromuscular blockade at the end of surgery. Postoperative complications including respiratory (desaturation, re-intubation, unplanned ICU admission) and cardiovascular complications were higher in those receiving neostigmine vs. sugammadex. The total costs were higher in the neostigmine vs. sugamadex group due to the higher cost to treat complications in the group receiving neostigmine.

Effects of γ-Aminobutyric Acid Type A Receptor Modulation by Flumazenil on Emergence from General Anesthesia

Using a rodent model of emergence from general anesthesia, flumazenil or saline control was administered to animals following isoflurane anesthesia.  Animals receiving flumazenil were found to emerge more quickly from anesthesia and to demonstrate electroencephalographic patterns consistent with waking sooner.  Post-anesthesia changes in sleep time and NREM sleep time in saline treated animals were not detected in animals receiving flumazenil.

Continuous Positive Airway Pressure Mitigates Opioid-Induced Worsening of Sleep-Disordered Breathing Early after Bariatric Surgery

In a randomized crossover trial, 33 patients completed postoperative polysomnography in the postanesthesia care unit following bariatric surgery.  64% demonstrated sleep disordered breathing during recovery.  CPAP administration was associated with decreased apnea hypopnea index, fewer oxygen desaturations, and amelioration of the respiratory depressant effects of sleep-wake transitions and opioid administration.  No significant hemodynamic effects of CPAP were observed.

The STOP BANG Questionnaire and the Risk of Perioperative Respiratory Complications in Urgent Surgery Patients: A Prospective, Observational Study

STOP BANG positivity was associated with increased intraoperative (21% vs. 6%) and postoperative (57% vs. 34%) respiratory complications in adult patients undergoing urgent surgery under general anesthesia and the association remained significant after multivariate analysis.  Patients with positive STOP BANG scores also had longer average hospital stays (6 vs. 4 days).

Sleep Apnoea and the Brain: A Complex Relationship

Intermittent hypoxia, reoxygenation, and hypercapnia or hypocapnia occur in both adults and children during untreated apnoea and hypopnoea, along with changes in cerebral blood flow and sleep fragmentation. These effects can result in cognitive deficits with functional effects on work and school efficiency. The assessment of how obstructive sleep apnoea affects cognition depends on the specificity and sensitivity of the tests, which are rarely developed specifically for obstructive sleep apnoea. In this Review, we discuss both the neural adaptive and maladaptive processes in response to hypoxaemia. The net result on cognitive and emotional performance depends on the stage of this dynamic process, effects on other body systems, cognitive reserve, and idiosyncratic susceptibility. We also explore the contribution of fragmented sleep, and the disruption of sleep structure, with focus on the effect at different times in the development of disease. This Review will address the gap in the underlying pathophysiology of new clinical and translational findings, and argue their contribution to the inherent complexity of the association between obstructive sleep apnoea and the brain.

Circadian Gene Variants Influence Sleep and the Sleep Electroencephalogram in Humans

The sleep electroencephalogram (EEG) is highly heritable in humans and yet little is known about the genetic basis of inter-individual differences in sleep architecture. The aim of this study was to identify associations between candidate circadian gene variants and the polysomnogram, recorded under highly controlled laboratory conditions during a baseline, overnight, 8 h sleep opportunity. A candidate gene approach was employed to analyze single-nucleotide polymorphisms from five circadian-related genes in a two-phase analysis of 84 healthy young adults (28 F; 23.21 ± 2.97 years) of European ancestry. A common variant in Period2 (PER2) was associated with 20 min less slow-wave sleep (SWS) in carriers of the minor allele than in noncarriers, representing a 22% reduction in SWS duration. Moreover, spectral analysis in a subset of participants (n = 37) showed the same PER2 polymorphism was associated with reduced EEG power density in the low delta range (0.25-1.0 Hz) during non-REM sleep and lower slow-wave activity (0.75-4.5 Hz) in the early part of the sleep episode. These results indicate the involvement of PER2 in the homeostatic process of sleep. Additionally, a rare variant in Melatonin Receptor 1B was associated with longer REM sleep latency, with minor allele carriers exhibiting an average of 65 min (87%) longer latency from sleep onset to REM sleep, compared to noncarriers. These findings suggest that circadian-related genes can modulate sleep architecture and the sleep EEG, including specific parameters previously implicated in the homeostatic regulation of sleep.

Changes in the Composition of Brain Interstitial Ions Control the Sleep-Wake Cycle

Wakefulness is driven by the widespread release of neuromodulators by the ascending arousal system. Yet, it is unclear how these substances orchestrate state-dependent, global changes in neuronal activity. Here, we show that neuromodulators induce increases in the extracellular K(+) concentration ([K(+)]e) in cortical slices electrically silenced by tetrodotoxin. In vivo, arousal was linked to AMPA receptor-independent elevations of [K(+)]e concomitant with decreases in [Ca(2+)]e, [Mg(2+)]e, [H(+)]e, and the extracellular volume. Opposite, natural sleep and anesthesia reduced [K(+)]e while increasing [Ca(2+)]e, [Mg(2+)]e, and [H(+)]e as well as the extracellular volume. Local cortical activity of sleeping mice could be readily converted to the stereotypical electroencephalography pattern of wakefulness by simply imposing a change in the extracellular ion composition. Thus, extracellular ions control the state-dependent patterns of neural activity.

Association Between Type of Sedation and the Adverse Events Associated with Gastrointestinal Endoscopy: An Analysis of Five Years’ Data from a Tertiary Center in the USA

This is a retrospective, single institution study, based in the analysis of more than 70000 procedures. A total of 163 adverse events were reported including 13 cases of cardiac arrest. The analysis shows that propofol anesthesia was associated with more incidence of adverse events than midazolam-fentanyl combined. It might look controversial although several factors still need to be considered.