Muscle Recovery Following Aortic Surgery Induced ICUAW.

To identify determinants of 'good and bad recovery' from ICUAW and build knowledge around the timing of these processes. Also, the investigators want to discover the effects of ICUAW on physical function and HRQoL following aortic surgery.

The aim is to identify determinants of recovery from intensive care unit-acquired weakness (ICUAW) and to discover the effects of ICUAW on physical function and health-related quality of life (HRQoL) after critical illness. This phenomenon has become more evident over recent years and still requires extensive research.

ICUAW is an umbrella term for more specifically, polyneuropathy and myopathy. Recent research has found that 50% of patients undergoing elective cardiac surgery lose significant muscle mass (9.6% in the wasters group) within the first seven days. These patients are receiving relatively uncomplicated surgery yet still suffering from muscle breakdown, which cannot be described by inactivity alone. ICUAW can lead to a significant increase in mortality, morbidity, hospital-acquired infections and pressure ulcers. Risk factors for ICUAW include neuromuscular blocking agents, hyperglycaemia, inactivity and sepsis. The correlation between a relatively homogenous (cardiac surgical) group and patient-centred outcomes during recovery such as functional ability and health-related quality of life (HRQoL) has been little studied.

Patients undergoing elective aortic valvular surgery at St Bartholomew's Hospital London will be recruited for the study. We have chosen the cardiac surgical model due to being a homogenous cohort where the time of insult from surgery from the cardiac bypass, can be measured in correlation with ICUAW. Due to the clamped aorta within the operation, prolonged periods of reduced blood flow to the body occurs, and therefore an element of ischaemia and reperfusion can lead to muscle wasting. Rectus Femoris cross-sectional area (RFcsa) will be measured at pre-determined intervals and the images then greyscaled and muscle quality assessed. To assess and quantify 'good and bad recovery,' we will correlate these tests with functional capacity and HRQoL. Additionally, Blood and urine samples will be taken at pre-defined intervals to observe for markers of oxidative stress, organ injury and molecular profiles. Muscle biopsies will be taken during surgery and observed for histological and fibre profiles.

The primary objective is to identify determinants of recovery from ICUAW and to discover the effects of ICUAW on physical function and health-related quality of life (HRQoL) after aortic valvular surgery. Specifically, to observe the cross-sectional area of the Rectus Femoris (RFcsa) and correlate this with muscle strength and HRQoL during the recovery phase. The RFcsa, hand-held dynamometry, knee straightening dynamometry, Free Fat Mass Index, standing and lying vital capacity and the short physical performance battery (SPPB) will be observed. Also, HRQoL will be measured using the reintegration to normal living index (RNLI), hospital and anxiety depression score (HADS), EQ-5D-5L (EuroQol research foundation). The primary endpoint will be once all these data are gathered and analysed.

The secondary aim is to understand the molecular and genomic profile of blood samples and the histology of the muscle biopsies. The secondary objective will be supported with additional data from urine analysis (Albumin-creatinine ratio, ACR). The secondary endpoint will be once these data are gathered and analysed.

Eligibility Criteria:
Inclusion Criteria:

* Above the age of 18
* Receiving elective aortic valvular surgery at Barts Health NHS Trust

Exclusion Criteria:

* Previous Stroke
* Neuromuscular disease
* Malignancy
* Underlying neuromuscular disease
* Paediatrics
* Non-consenting adults