Muscle atrophy in mechanically-ventilated critically ill children

Expression of MuRF1 or MuRF2 is essential for the induction of skeletal muscle atrophy and dysfunction in a murine pulmonary hypertension model

BACKGROUND

Pulmonary hypertension leads to right ventricular heart failure and ultimately to cardiac cachexia. Cardiac cachexia induces skeletal muscles atrophy and contractile dysfunction. MAFbx and MuRF1 are two key proteins that have been implicated in chronic muscle atrophy of several wasting states.

METHODS

Monocrotaline (MCT) was injected over eight weeks into mice to establish pulmonary hypertension as a murine model for cardiac cachexia. The effects on skeletal muscle atrophy, myofiber force, and selected muscle proteins were evaluated in wild-type (WT), MuRF1, and MuRF2-KO mice by determining muscle weights, in vitro muscle force and enzyme activities in soleus and tibialis anterior (TA) muscle.

RESULTS

In WT, MCT treatment induced wasting of soleus and TA mass, loss of myofiber force, and depletion of citrate synthase (CS), creatine kinase (CK), and malate dehydrogenase (MDH) (all key metabolic enzymes). This suggests that the murine MCT model is useful to mimic peripheral myopathies as found in human cardiac cachexia. In MuRF1 and MuRF2-KO mice, soleus and TA muscles were protected from atrophy, contractile dysfunction, while metabolic enzymes were not lowered in MuRF1 or MuRF2-KO mice. Furthermore, MuRF2 expression was lower in MuRF1KO mice when compared to C57BL/6 mice.

CONCLUSIONS

In addition to MuRF1, inactivation of MuRF2 also provides a potent protection from peripheral myopathy in cardiac cachexia. The protection of metabolic enzymes in both MuRF1KO and MuRF2KO mice as well as the dependence of MuRF2 expression on MuRF1 suggests intimate relationships between MuRF1 and MuRF2 during muscle atrophy signaling.

Post-discharge respiratory outcomes of children with acute respiratory distress syndrome

OBJECTIVES

While long-term sequelae of acute respiratory distress syndrome (ARDS) are well-documented in adults, few studies reported post-discharge respiratory complications in pediatric ARDS (PARDS) and none used the recent Pediatric Acute Lung Injury Consensus Conference (PALICC) diagnostic criteria. This study describes the respiratory symptoms, pulmonary function, and health resource use of PARDS survivors at 3 months post-discharge.

DESIGN

Retrospective study.

PATIENT SELECTION

Children less than 18 years admitted to the intensive care unit of Sainte-Justine University Health Center from 1st September 2015 to 1st July 2017, and meeting PALICC diagnostic criteria for PARDS.

METHODS

We evaluated 38 of the 44 children with PARDS in the follow-up clinic at a mean (SD) of 3.4 (2.0) months post-discharge for respiratory symptoms, age-appropriate pulmonary function tests (spirometry or oscillometry, maximal respiratory pressures), and all-cause emergency department (ED) visits or rehospitalizations since discharge.

RESULTS

Fourteen (36.8%) had abnormal respiratory symptoms (most commonly cough between respiratory infections and wheezing), 7 of whom (18.4%) presented new respiratory symptoms since PARDS diagnosis. A mild-to-moderate restrictive pattern was observed in 3 of 10 patients who performed spirometry and mildly decreased maximal inspiratory pressures were noted in 2 of 8 patients who performed these maneuvers. Nine (23.7%) patients consulted in the ED and 4 (10.5%) were rehospitalized post-discharge.

CONCLUSIONS

Despite our cohort's limited sample size, our findings suggest that a significant proportion of PARDS survivors experience abnormal respiratory symptoms, pulmonary function deficits, and recurrent problems requiring medical attention. Larger, multicenter studies are required to identify risk factors associated with poor post-discharge outcomes among PARDS survivors.

Changes in Provider Perceptions Regarding Early Mobility in the PICU

OBJECTIVES

Early mobility in the PICU is safe and feasible. However, PICUs continue to meet barriers to implementing early mobility. PICU providers were surveyed before and after initiating an early mobility protocol to determine perceived barriers and continued challenges in performing early mobility.

DESIGN

This single-center prospective study surveyed PICU providers regarding 26 potential barriers to early mobility using a five-point Likert scale. A survey was distributed 1 month prior to and 6 months after beginning an early mobility protocol.

SETTING

Free-standing academic tertiary care children's hospital.

SUBJECTS

PICU providers of various professions.

INTERVENTIONS

Implementation of PICU-wide early mobility protocol.

MEASUREMENTS AND MAIN RESULTS

Paired pre- and post-early mobility protocol implementation surveys from 97 providers were compared. System-based barriers decreased after implementation of the early mobility protocol, such as lack of guidelines (75-20%; p < 0.01), inadequate training (74-33%; p < 0.01), lack of early mobility orders (72-30%; p < 0.01), and delayed recognition of early mobility candidates (68-35%; p < 0.01). Difficulty coordinating early mobility sessions, although significantly decreased, still remained a concern for 66% of providers in the postsurvey. Lack of resources, specifically staff (85-82%; p = 0.68) and equipment (67-60%; p = 0.36), also remained significant barriers. Presence of an endotracheal tube was a barrier for only 29% of providers' post-early mobility protocol, compared with 69% prior (p < 0.01). Clinical instability remained a top concern (82-79%; p = 0.63) as well as agitation (74-67%; p = 0.23). Day shift providers, with more early mobility exposure, perceived fewer barriers compared with night shift providers. Ninety percentage of post-early mobility survey participants felt that early mobility positively impacted their patients.

CONCLUSIONS

Implementation of an early mobility protocol significantly changed provider perceptions regarding barriers to early mobility. Certain factors, such as staff availability, coordination difficulty, equipment shortage, and patient clinical factors, continue to be significant challenges to early mobility in the PICU population.