Guided Tissue Oxygenation Monitoring Shows No Postoperative Benefit in Off-Pump CABG: Bottomline-CS Trial

The findings were published online in The BMJ on 24 March 2025.

Jiange Han, chief physician and chair from the Department of Anesthesiology, Tianjin Chest Hospital, Tianjin University, Tianjin, China, and colleagues aimed to evaluate whether guiding perioperative management using near-infrared spectroscopy to monitor tissue oxygen saturation, along with haemodynamic monitoring, can help reduce postoperative complications following off-pump coronary artery bypass grafting.

For this purpose, the researchers conducted the Bottomline-CS trial—an assessor-blinded, single-centre randomised controlled study at a tertiary teaching hospital in China. They enrolled 1,960 patients aged 60 years or older undergoing elective off-pump coronary artery bypass grafting. All patients were monitored for tissue oxygen saturation at multiple sites and received haemodynamic monitoring. While both groups received standard care, the intervention group was guided to maintain tissue oxygenation within 10% of preoperative baseline values. In the usual care group, monitoring data were blinded.

The study assessed 30-day composite postoperative complications, with secondary outcomes including individual complications, atrial fibrillation, and hospital stay.

The following were the key findings:

• Of the 1960 patients randomly assigned, data from 967 in the guided care group and 974 in the usual care group were analysed.
• Guided care significantly reduced the time tissue oxygen saturation levels remained outside ±10% of baseline during anaesthesia, with lower values seen at the left forehead (32.4 vs 57.6), right forehead (37.9 vs 62.6), and forearm (14.8 vs 44.7).
• The primary composite outcome occurred in 47.3% of guided care patients and 47.8% of usual care patients, showing no significant difference.
• None of the secondary outcomes showed statistically significant differences between the two groups.
• Pneumonia was less frequent in the guided care group (9.1%) than the usual care group (12.4%), but the difference was not statistically significant after adjustment.

In conclusion, the Bottomline-CS trial evaluated whether perioperative care guided by multisite near-infrared spectroscopy and haemodynamic monitoring could improve outcomes in patients undergoing off-pump coronary artery bypass grafting. The researchers found that while this approach effectively maintained tissue oxygenation close to baseline levels, it did not reduce the incidence of major postoperative complications or impact other outcomes such as atrial fibrillation or hospital stay.

"The narrow confidence interval around the primary outcome reinforces the reliability of these neutral findings. The study does not support the routine use of multisite tissue oxygenation and haemodynamic monitoring as part of standard care in off-pump CABG procedures," they wrote.

Reference: BMJ 2025;388:e082104