Non-volitional assessment of tibialis anterior force and architecture during critical illness
Bronwen Connolly, Matthew Maddocks, Victoria MacBean, William Bernal, Nicholas Hart, Philip Hopkins, Gerrard F Rafferty
Published in the journal Muscle and Nerve, December 2017
After being admitted into the intensive care unit (ICU) some patients experience muscle weakness and as a result they struggle to walk properly and perform other daily tasks. This weakness is not always a direct result of the condition for which the patient was admitted. The term intensive care unit-acquired weakness (ICU-AW) is the name given to functionally unfit muscles of patients who have been admitted to ICU for which there is no other reasonable explanation. ICU-AW is a serious problem as it means the quality of life of patients after their ICU stay can be impaired as their muscle weakness can be quite severe and limit what they can do.
This research was used to investigate whether admission to ICU is the cause of muscle weakness many patients experience after their stay. The researchers tested this by assessing the size and strength of a muscle at the front of the shin. This muscle is easy to access without disrupting patients’ treatment. It is also responsible for balance and walking therefore the researchers found it to be an important muscle to focus on as patients who experience weakened shin muscles can have negatively impacted lives. Moreover, researchers decided to use testing techniques that don’t involve conscious effort from the patient as it meant eliminating limitations such as patient cooperation and motivation, making the research more reliable.
The study included thirteen adults who had been admitted to ICU and who required breathing support for at least 48 hours. Patients’ shin muscle size and strength was assessed on two occasions seven days apart in order to see whether any weakness developed during their ICU stay.
If patients’ ICU stay caused their muscles to decline in ability, like the term ICU-AW suggests, then the researchers would have seen a decrease in strength of their shin muscle. What the results showed, however, was that there was weakness present at the start of their ICU admission, with no further decline in muscle strength during admission, though the muscles did decrease somewhat in size. This finding led the researchers to suggest that ‘critical illness-associated weakness’ would be a more reflective term than ICU-acquired weakness. Of course, it is important to note that due to the small number of patients studied used the data isn’t entirely conclusive as the small sample may not be representative of all patients who experience weakness after an ICU stay.
This study suggests that the ICU environment may not be the cause of the weakness patients experience. This highlights the need for further research into ICU-AW so that more about the condition can be learned; this could lead to a possible way to prevent it from developing in the first place.
This summary was produced by Iva Koshova, Year 13 student from Harris Academy, Greenwich, as part of our departmental educational outreach programme.