Medical Research: Emerging Concepts and Applications Vol. 1

Background: Reduced skeletal-muscle quantity is associated with adverse postoperative outcomes in older adults. Point-of-care ultrasound provides a portable method for assessing rectus femoris morphology. This study compared rectus femoris cross-sectional area (RF-CSA) and rectus femoris muscle thickness (RF-MT) as exploratory markers of 30-day postoperative morbidity in older patients undergoing major surgery.

Methods: This single-centre prospective observational cohort study included 84 patients aged 60 years or older, classified as American Society of Anesthesiologists physical status I-III, and scheduled for major surgery lasting more than two hours under general or spinal anaesthesia. Preoperative RF-CSA and RF-MT were measured by standardised B-mode ultrasonography at 60% of the distance between the anterior superior iliac spine and the superior border of the patella. A low-RF-CSA classification was assigned using sex-specific thresholds derived from a previously published chronic kidney disease cohort and was treated as a marker of low muscle quantity rather than a complete diagnosis of sarcopenia. Six 30-day outcomes and a composite of the first five outcomes were evaluated.

Results: Twenty-three participants had low RF-CSA and 61 had preserved RF-CSA. Prolonged hospital stay (>7 days) occurred in 18/23 (78.3%) participants with low RF-CSA and 6/61 (9.8%) with preserved RF-CSA. ICU ventilatory support occurred in 7/23 (30.4%) versus 3/61 (4.9%), inotropic or vasopressor support in 12/23 (52.2%) versus 4/61 (6.6%), and composite morbidity in 20/23 (87.0%) versus 6/61 (9.8%). For prolonged stay, the prespecified RF-CSA thresholds yielded 75.0% sensitivity, 91.7% specificity, 78.3% positive predictive value, and 90.2% negative predictive value. Continuous RF-CSA showed greater descriptive discrimination than RF-MT (area under the curve 0.912 vs 0.656). In Firth penalised models adjusted for age, sex, ASA class, surgical category, and operative duration, low RF-CSA remained associated with prolonged stay (adjusted odds ratio 8.42, 95% confidence interval 2.05-34.60) and composite morbidity (adjusted odds ratio 6.72, 95% confidence interval 1.92-23.50).

Conclusion: Lower preoperative RF-CSA was associated with prolonged hospitalisation and selected postoperative morbidity outcomes in this exploratory cohort. RF-CSA showed better descriptive discrimination than RF-MT for prolonged hospital stay, but the findings are cohort-specific and require prospective multicentre validation before clinical implementation.