Effects of fentanyl on diaphragm muscle force in patients undergoing knee arthroplasty: a randomised double-blind...

Opioids exert important negative effects on respiration, evident across a range of behaviours. The present study evaluated whether fentanyl administration decreases diaphragm muscle forces across levels of inspiratory loading in adult patients undergoing elective knee arthroplasty surgery.

Adult patients undergoing elective knee arthroplasty with no pulmonary pathology were randomly assigned to a fentanyl dose (25, 50, or 100 μg) in a double-blind, single-institution clinical trial. Ultrasound-based shear wave elastography was used to measure diaphragm Young's modulus (E). The primary outcome was change in the difference in E achieved across levels of inspiratory loading (E range) before randomisation and 10 min post-fentanyl (ΔE range) as a measure of fentanyl-induced changes in diaphragm force-generating capacity.

Sixty-nine patients (average age 69 yr) were randomised, with final data analysis in 22, 22, and 19 patients from the 25, 50, and 100 μg groups, respectively. The ΔE range was compared across dose groups using analysis of covariance, with the pretreatment E range included as the covariate. The estimated treatment effect (95% confidence interval) for 50 μg vs 25 μg, and for 100 μg vs 25 μg was -0.7 (-9.5, 8.1) and -5.3 (-14.1, 3.6), respectively. There was no statistically significant effect of fentanyl on ΔE range (P=0.432).

Fentanyl did not reduce the E range generated by the diaphragm muscle during inspiratory pressure-threshold loading, possibly reflecting relatively low levels of inspiratory loading or the presence of a fentanyl effect even at the lowest dose used (25 μg) in this older patient population.

NCT05856136.