The effects of analgesia methods on postoperative diaphragm muscle contraction in patients undergoing laparotomy

Aims: This prospective observational study aimed to evaluate the effects of different postoperative analgesia methods on diaphragm thickening fractions in patients undergoing major elective abdominal surgery. Methods: Sixty-six adult patients scheduled for elective major abdominal surgery due to gastrointestinal tumors were enrolled and divided into three groups according to analgesia methods; intravenous (IV) analgesia, abdominal wall block (B), and a combination of block plus intravenous analgesia (BIV). Diaphragm thickness and diaphragm thickening fractions were measured preoperatively and postoperatively using ultrasound during rest and forced inspiration. The primary parameter was the prevention of diaphragm dysfunction by BIV compared to other methods. The secondary outcome was the change in diaphragm thickening fractions at rest and during maximal inspiration compared to preoperative values. Results: No patients demonstrated clinical diaphragm dysfunction based on contraction indices. However, postoperative diaphragm thickening fractions decreased significantly in the IV group at rest and in the B group during maximal inspiration (p<0.05), whereas no significant reduction was observed in the BIV group. BIV provided significantly better postoperative pain control (lower VAS scores) and was associated with preserved diaphragm thickening fractions, supporting a potential protective effect on diaphragmatic function. Conclusion: Major abdominal surgery leads to a measurable decline in diaphragmatic contractility in patients receiving single-modality analgesia (B or IV), whereas combined BIV analgesia preserves postoperative diaphragm function while improving pain control. These findings suggest that multimodal analgesia may help protect respiratory muscle performance in the early postoperative period.