D 3 ‐Creatine Derived Skeletal Muscle Mass Correlates With Grip Strength in (Pre)frail Older Adult Patients Undergoing Cardiac Surgery
Neetika Bharaj, Sarkis J. Hannaian, José A. Correa, Mariana De Sa Tavares Russo, Daina Avizonis, Todd A. Duhamel, Rakesh C. Arora, Emmanuel Moss, Jonathan Afilalo, Tyler A. Churchward‐VenneABSTRACT
Background
(Pre)frail older adult patients undergoing cardiac surgery experience disproportionate mortality and prolonged length of stay, underpinned by low skeletal muscle mass (SMM), which is central to the underlying frailty pathophysiology. Conventional methods for assessing SMM have well‐recognized limitations in this population. The D 3 ‐creatine (D 3 ‐Cr) dilution method offers a non‐invasive, direct estimate of total‐body SMM. Pre‐surgery D 3 ‐Cr derived SMM and its relationship with strength, physical performance and multidimensional health status measures in (pre)frail older adult patients undergoing cardiac surgery have not been explored.
Methods
Seventeen (pre)frail older adult patients (16 male, 1 female; median 75 [interquartile range: 67–75] years; body mass index 28.7 [24.2–29.9] kg/m 2 ; Clinical Frailty Scale 3 [3, 4]) ingested a single 30‐mg oral dose of D 3 ‐Cr 3.5 [3.0–4.3] days prior to scheduled elective or non‐emergent (inpatient) cardiac surgery. Spot urine was collected pre‐dose and 48–72 h post‐dose, and D 3 ‐creatinine (D 3 ‐Crn) and unlabelled creatine and creatinine were quantified by liquid chromatography–tandem mass spectrometry. Total‐body SMM was estimated using a published spillage‐correction algorithm; both a height‐adjusted and body weight–adjusted SMM index were calculated as SMM divided by height squared and SMM divided by body weight. Spearman's rank correlations (r s ) between strength, physical performance outcomes and multidimensional health status measures and (i) absolute SMM, (ii) height‐adjusted SMM index and (iii) body weight–adjusted SMM index were calculated; bias‐corrected and accelerated bootstrap (10 000 resamples) provided 95% confidence intervals (CIs). Kendall's τ was also calculated as a sensitivity analysis.
Results
Median absolute total‐body SMM derived from D 3 ‐Cr dilution was 31.7 [27.4–40.9] kg, and the corresponding height‐adjusted and body weight–adjusted SMM index was 10.8 [9.7–13.7] and 41.7 [36.1–47.4]. Handgrip strength positively associated with absolute SMM, r s = 0.61 (95% CI [0.12, 0.91], n = 14, p = 0.02) and height‐adjusted SMM index, r s = 0.55 (95% CI [0.03, 0.88], n = 14, p = 0.04), but not body weight–adjusted SMM index. The 5× sit‐to‐stand, 4‐m gait speed, balance, Short Physical Performance Battery score, length of stay, SF‐36 physical functioning score and Mini Nutritional Assessment score were not significantly associated with absolute, height‐adjusted or body weight–adjusted SMM (all p ≥ 0.10).
Conclusions
The D 3 ‐Cr dilution method can be applied for the pre‐operative assessment of SMM in (pre)frail older cardiac surgery patients. Handgrip strength tracked with both absolute and height‐adjusted D 3 ‐Cr derived SMM, providing preliminary support for an association between D 3 ‐Cr derived muscle mass and grip strength in older cardiac surgery patients.