Sleep and critical illness: a review

Critical illness and stays in the Intensive Care Unit (ICU) have significant impact on sleep. Poor sleep is common in this setting, can persist beyond acute critical illness, and is associated with increased morbidity and mortality. In the past 5 years, intensive care clinical practice guidelines have directed more focus on sleep and circadian disruption, spurring new initiatives to study and improve sleep complications in the critically ill. The global SARS-COV-2 (COVID-19) pandemic and dramatic spikes in patients requiring ICU level care also brought augmented levels of sleep disruption, the understanding of which continues to evolve. This review aims to summarize existing literature on sleep and critical illness and briefly discuss future directions in the field.

Predictors of Respiratory Support Use in Emergency Department Patients With COVID-19-Related Respiratory Failure

BACKGROUND

Given the known downstream implications of choice of respiratory support on patient outcomes, all factors influencing these decisions, even those not limited to the patient, warrant close consideration. We examined the effect of emergency department (ED)-specific system factors, such as work load and census, on the use of noninvasive versus invasive respiratory support.

METHODS

We conducted a multi-center retrospective cohort study of all adult subjects with severe COVID-19 requiring an ICU admission from 5 EDs within a single urban health care system. Subject demographics, severity of illness, and the type of respiratory support used were obtained. Using continuous measures of ED census, boarding, and active management, we estimated ED work load for each subjects' ED stay. The subjects were categorized by type(s) of respiratory support used: low-flow oxygen, noninvasive respiratory support (eg, noninvasive ventilation [NIV] and/or high-flow nasal cannula [HFNC]), invasive mechanical ventilation, or invasive mechanical ventilation after trial of NIV/HFNC. We used multivariable logistic regression to examine system factors associated with the type of respiratory support used in the ED.

RESULTS

A total of 634 subjects were included. Of these, 431 (70.0%) were managed on low-flow oxygen alone, 108 (17.0%) on NIV/HFNC, 54 (8.5%) on invasive mechanical ventilation directly, and 41 (6.5%) on NIV/HFNC prior to invasive mechanical ventilation in the ED. Higher severity of illness and underlying lung disease increased the odds of requiring invasive mechanical ventilation compared to low-flow oxygen (odds ratio 1.05 [95% CI 1.03-1.07] and odds ratio 3.47 [95% CI 1.37-8.78], respectively). Older age decreased odds of being on invasive mechanical ventilation compared to low-flow oxygen (odds ratio 0.96 [95% CI 0.94-0.99]). As ED work load increased, the odds for subjects to be managed initially with NIV/HFNC prior to invasive mechanical ventilation increased 6-8-fold.

CONCLUSIONS

High ED work load was associated with higher odds on HFNC/NIV prior to invasive mechanical ventilation.

Meticillin-resistant Staphylococcus aureus contamination of healthcare workers' uniforms in long-term care facilities

Meticillin-resistant Staphylococcus aureus (MRSA) and other multiply resistant bacteria are frequently isolated in long-term care facilities (LTCFs). This study evaluated the contamination of staff clothing in three LTCFs. Over 500 samples were taken from uniforms and their pockets and these samples showed a high level of MRSA contamination. Wearing plastic aprons and managing pocket contents improved the contamination rate. Our results highlight the continued importance of hand hygiene, since staff have frequent contact with their uniforms and could potentially contaminate their hands before care.

Improved erythrocyte lysis assay in microtitre plates for sensitive detection and efficient measurement of haemolytic compounds from ichthyotoxic algae

Haemolytic substances produced by ichthyotoxic algae often are unknown in molecular structure or specific mechanism of toxicity. Detection and quantification of such substances are dependent on bioassays, using markers that are sensitive for haemolytic impairment and generation of a recordable response. The erythrocyte lysis assay (ELA) represents an advantageous bioassay in this respect, because the lytic response can be measured photometrically by the amount of released haemoglobin. The aim of the present study was to establish an improved assay based on the ELA principle, for sensitive determination of haemolytic substances of microalgae and for high sample throughput. For this purpose we adapted the ELA to a 96-well microtitre plate format, which significantly reduced the sample volumes and allowed rapid processing of samples. Further improvement was achieved by measuring absorption of lysed erythrocytes at 414 nm, which significantly increased the sensitivity of the ELA compared to the measurements at 540 nm that are usually applied in this type of assay. Using carp (Cyprinus carpio) erythrocytes it was possible to detect haemolysis induced by 4 microg ml(-1) of saponin and as little as two haemolytic Alexandrium tamarense cells. It is suggested that this improved ELA in microtitre plates be used as a low-cost monitoring tool for detection and analysis of potential harmful algae. Furthermore, this ELA can be useful as a sensitive screening system for substances of pharmacological interest, e.g. selectively acting cytolytic antibiotics.

A simple and highly efficient fixation method for Chrysochromulina polylepis (Prymnesiophytes) for analytical flow cytometry

BACKGROUND

To study the fragile Prymnesiophyte species Chrysochromulina polylepis by flow cytometry (FC), we needed an effective fixation method. This method must guarantee a high yield of fixed cells to achieve acceptable measurement times by FC and to allow quick processing of many samples. Moreover, we wanted a method that allows for storage of fixed samples when FC analysis cannot be done immediately.

METHODS

Different aldehydes and methanol were tested at different final concentrations. Gravity sedimentation and centrifugation were applied to achieve higher cell concentrations. Storage of fixed samples was tested under different conditions.

RESULTS

0.25% glutaraldehyde (GA) fixation yielded a recovery rate of about 90%. The signals obtained by FC analysis were excellent. It is possible to centrifuge GA-fixed cells and to store them for several weeks.

CONCLUSIONS

GA is the fixative of choice for FC analysis of C. polylepis (and possibly other small delicate species) because it yielded highly significant recovery rates and high-quality FC signals. Cells can be centrifuged to increase the cell concentration, thereby achieving short measurement times with FC. The possibility of long-term storage of fixed cells presents an additional advantage if FC analysis cannot be done immediately.

A tissue-like culture system using microstructures: influence of extracellular matrix material on cell adhesion and aggregation

Special microenvironmental conditions are required to induce and/or maintain specific qualities of differentiated cells. An important parameter is the three-dimensional tissue architecture that cannot be reproduced in conventional monolayer systems. Advanced tissue culture systems will meet many of these demands, but may reach their limits, especially when gradients of specific substances over distinct tissue layers must be established for long-term culture. These limitations may be overcome by incorporating microstructures into tissue-like culture systems. The microstructured cell support presented consists of a flat array of 625 cubic microcontainers with porous bottoms, in which cells can be supplied with specific media from both sides of the tissue layer. Permanent cell lines and primary rat hepatocytes have been used to test the culture system. In order to define reproducible conditions for tissue formation and for cell adherence to the structure, several ECM (extracellular matrix) components were tested for coating of microstructured substrata. The described tissue culture system offers great flexibility in adapting the cell support to specific needs.

Expression of yeast but not human apurinic/apyrimidinic endonuclease renders Chinese hamster cells more resistant to DNA damaging agents

Abasic sites represent ubiquitous DNA lesions that arise spontaneously or are induced by DNA-damaging agents. They block DNA replication and are considered to be cytotoxic and mutagenic. The key enzymes involved in the repair of abasic sites are apurinic/apyrimidinic (AP) endonucleases which process these lesions in an error-free mechanism. To analyze the role of AP endonuclease in the protection of mammalian cells against DNA damaging agents, we have transfected both the human (APE) and the yeast (APN1) AP endonuclease in Chinese hamster cells and compared the effects of expression of these genes in stable transfectants as to survival of cells and formation of chromosomal aberrations. Although APE was markedly expressed on RNA and protein level, nuclear extracts of human APE transfectants did not show a higher AP endonuclease activity than the parental line and became not more resistant to the cell killing and clastogenic effect of methyl methanesulfonate (MMS) and hydrogen peroxide (H2O2). In contrast, cells transfected with the yeast APN1 gene expressed higher AP endonuclease activity and became clearly more resistant to the cytotoxic and chromosome breakage inducing activity of the agents. The results indicate that the excision repair capacity and correspondingly the mutagen resistance can be elevated by introducing, in mammalian cells, a yeast DNA repair gene and verify that AP sites are both cytotoxic and clastogenic lesions.