Background:

Hypotension is a common event in patients under general anesthesia during lumbar spine fusion surgery. The reduction of venous drainage followed by the postural changes is the main reason. The venous return reduced when the intrathoracic pressure is positive. Volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) are two traditional ventilation modes in operating room, with different respiratory mechanics. The two ventilation modes have different influences on intrathoracic pressure and consequently venous return. A double-blinded, randomized, parallel group controlled clinical trial was conducted to examine the hemodynamic and respiratory effects of two different ventilation modes in lumbar spine fusion surgery.

Methods:

Forty-eight patients scheduled for posterior lumbar spine fusion surgery at Zhongda Hospital, Southeast University were randomly allocated into two groups to receive either the VCV mode or PCV mode [vital volume (VT) 8 mL/kg, and partial pressure of end-tidal carbon dioxide (PETCO2) 35-45 mmHg]. The respiratory mechanics [peak airway pressure (Ppeak) and dynamic compliance (Cdyn)] and hemodynamic changes were measured every 10 min for 120 min. All participants and relevant staff were blinded to the randomization.

Results:

The data of 19 of 22 patients in the VCV group and 18 of 20 in the PCV group were analyzed. Compared to VCV group, cardiac output (CO) and central venous pressure (CVP) in the PCV group were higher; however, the difference was not significant. There’s no statistically difference in systemic vascular resistance index (SVRI) values of both the groups. The mean blood pressure (MBP) of the PCV group was higher than that of the VCV group from 90 min after the patients were turned to the prone position until the endpoint. The Cdyn and Ppeak of the PCV group were higher than those of the VCV group. Additionally, there was a positive correlation between Cdyn and CO (r=0.744, P=0.006).

Conclusions:

With better respiratory mechanic and hemodynamic stability, PCV was a better choice for patients undergoing lumbar spine fusion surgery.

Trial registration:

Chinese Clinical Trial Registry ChiCTR-TRC-14005086.