Literature Updates from November 2015

Intermittent Hypoxia Causes Inflammation and Injury to Human Adult Cardiac Myocytes

The authors compared the cellular responses of cultured human adult cardiac myocytes exposed to intermittent hypoxia and different conditions of continuous hypoxia and normoxia. Intermittent and constant severe hypoxia, but not constant mild hypoxia or normoxia, induced inflammation and cell injury in the myocytes as evidenced by lower cell count and viability, and greater cytokine secretion. The greatest cell injury occurred with intermittent severe hypoxia.

Memory Engram Cells Retain Memory Under Retrograde Amnesia

This work outlines circuitry involved in memory formation using a dual genetic reporter system for labeling learning-dependent cells, a mouse model of contextual fear learning and delivery of an amnestic agent. The authors determine that if an amnestic agent is given shortly after the conditioning shock, the animals behave as though they had never experienced the shock (do not freeze when a tone is administered in a cage) and have neurons in the circuit with decreased synaptic strength and spine density. But, optogenetic activation of the circuits that were active during (specific) memory formation causes the mouse to freeze (as though it remembered the shock). Therefore, although the memory of the fearful event (tone-shock) is established even if an amnestic agent is given, the ability to access the memory (recall) seems to be the inhibited process. The authors propose that intact neuronal connectivity patterns are important for memory formation and that synaptic strength may be involved in memory retrieval.

Effects of Sleep and Wake on Astrocytes:
clues from Molecular and Ultrastructural Studies

This paper investigates the relationship between sleep/wake states and astrocyte maintenance of the dendritic spine niche. In the awake or chronic sleep restriction states, synaptic associations are maintained indicating a role for the astrocyte in preserving synapses. This work provides a mechanistic glimpse of how the sleep state may be responsible for synaptic pruning important for long-term potentiation or long-term depression in memory consolidation.

Routine Postoperative Monitoring After Bariatric Surgery in Morbidly Obese Patients with Severe Obstructive Sleep Apnea: ICU Admission is Not Necessary

In this study, the authors investigated the need for ICU admission after bariatric surgery. OSA has a known incidence of 70-80% in bariatric surgery patients. To prevent complications, many of these people are admitted to the ICU for observation. However, this could potentially increase overall cost of hospitalization and waste a scarce resource such as the ICU. Of the 794 patients in this study, 151 had severe sleep apnea and where admitted to the ICU. There were no deaths, re-intubations or other complications. The authors suggest, based on the findings in this study, that routine ICU use after laparoscopic bariatric surgery may be unnecessary.

Sleep Loss and Circadian Rhythm Disruption in the Intensive Care Unit

In this manuscript, the authors provide a nice discussion on the reasons why patients in the ICU have sleep disorders and how these disorders manifest in critically ill patients. The authors provide an interesting discussion of how being admitted to the ICU promotes and perpetuates sleep disorders and provide a discussion on what can be done to possibly prevent sleep deterioration in the ICU. This is a very interesting read for those just getting into the interface between sleep and critical care medicine. Interested readers should also seek previous works by Dr. Pisani who is currently at one of the nation’s most productive research centers for sleep in the ICU.

The Influence of Care Interventions on the Continuity of Sleep of Intensive Care Unit Patients

In this small study of 12 patients, the authors evaluate the influence of care on sleep using filming techniques and actigraphy. The authors noted 28 different types of care interventions of which 42.8 percent caused awakening for sleep. The examination revealed that there were 1.8 interventions per patient per hour.  Administration of oral medications and food were the interventions that caused higher frequencies of awakenings.  Health care providers need to rethink planning of interventions to help aid sleep. They off a few suggestions on how an ICU could do this.

Non-pharmacological Interventions for Sleep Promotion in the Intensive Care Unit

In this extensive review, the authors examined 30 studies, many of which were randomized controlled trails,  that evaluated the effects of non-pharmacological interventions for sleep promotion in patients admitted to the ICU who were 18 years of age or older.  In these studies, there were at total of 1569 patients.  The authors we able to review many interventions and their effects on sleep. They concluded that the quality of existing evidence pertaining to using non-pharmacological interventions for promoting sleep on critically ill adult patients was low or very low. However, they did find that earplugs or eye mask may have a small benefit on sleep and delirium in the ICU.

Remission and Incidence of Obstructive Sleep Apnea from Middle Childhood to Late Adolescence

The greater importance of middle childhood obesity compared to snoring in predicting adolescent OSA provides support for screening, preventing, and treating obesity in childhood.

Understanding the Anatomic Basis for Obstructive Sleep Apnea Syndrome in Adolescents

Increased size of the pharyngeal lymphoid tissue, rather than enlargement of the upper airway soft tissue structures, is the primary anatomic risk factor for OSAS in obese adolescents. These results are important for clinical decision making and suggest that adenotonsillectomy should be considered as the initial treatment for OSAS in obese adolescents.

Quality of Life and Obstructive Sleep Apnea Symptoms After Pediatric Adenotonsillectomy

Adenotonsillectomy compared with watchful waiting resulted in significantly more improvements in parent-rated generic and OSAS-specific QoL measures and OSAS symptoms.