Effect of Ultrasound-Guided Quadratus Lumborum Block on Diaphragmatic Excursion in Patients Undergoing Abdominal Surgery

Abstract

Background: Quadratus lumborum block (QLB) provides effective analgesia after abdominal surgery, but its effect on diaphragmatic function remains unclear. This study evaluated changes in diaphragmatic excursion following ultrasound-guided QLB.

Methods: This prospective observational study included 100 adults undergoing elective abdominal surgery under general anaesthesia with QLB. Diaphragmatic excursion was assessed using M-mode ultrasonography at baseline and predefined postoperative intervals. Pain scores, rescue analgesia, oxygen saturation, and respiratory complications were recorded.

Results: Mean diaphragmatic excursion decreased from 1.82 ± 0.35 cm at baseline to 1.68 ± 0.33 cm at 30 minutes (p<0.001), improving to 1.75 ± 0.34 cm at 2 hours and 1.80 ± 0.35 cm at 6 hours. Reduction was >20% in only 7% of patients. Rescue analgesia was required in 23%. Patients with >20% reduction had lower SpO₂ (95.9 ± 1.5% vs 97.6 ± 1.2%; p=0.001) and greater supplemental oxygen requirement (42.9% vs 7.5%; p=0.019). Pulmonary complications occurred in 2%.

Conclusion: QLB provided satisfactory postoperative analgesia with a mild, transient reduction in diaphragmatic excursion. Diaphragmatic movement approached baseline by 6 hours, with clinically significant respiratory complications being uncommon.