Comparison of Changes in Thoracic Fluid Content Between On-Pump and Off-Pump CABG by Use of Electrical Cardiometry

Abstract

Objectives: To compare the changes in thoracic fluid content, PaO₂/F_IO₂ ratio, plateau pressure, compliance, and postoperative ventilation duration in off-pump coronary artery bypass grafting (OPCAB) and on-pump coronary artery bypass grafting (ONCAB).

Design: Prospective observational study.

Setting: Tertiary-care cardiac center.

Participants: Over an 18-month period, from December 2019 to May 2021, 111 patients who underwent CAB grafting were enrolled. Group I constituted OPCAB patients and Group II the ONCAB patients.

Interventions: After induction, the authors measured thoracic fluid content (TFC), pulmonary compliance, airway pressures, and the PaO₂/F_IO₂ ratio before skin incision (T₁) and after skin closure (T₂). The input, output, as well as the duration of postoperative ventilation, also were recorded.

Results: At T₂, the ONCAB group had a significantly higher change in TFC than the OPCAB group (5.4 ± 1.86 kOhm^-1v 4.32 ± 1.84 kOhm^-1, p = 0.012). The fluid balance was significantly higher in the OPCAB group compared with the ONCAB group (2,159.21 ± 108.73 mL v 1,792.50 ± 151.88 mL, p = 0.0001). The decrease in PaO₂/F_IO₂ ratio was significantly lower in the OPCAB group compared with the ONCAB group (-71.34 ± 23.42 v -123.65 ± 36.81, p = 0.000). The increase in plateau pressure, decrease in compliance, and postoperative ventilation period were significantly higher in the patients who underwent ONCAB than the patients who underwent OPCAB (p < 0.05).

Conclusion: The change in TFC was greater in the ONCAB group, despite the fact that the fluid balance was higher in the OPCAB group. A higher TFC in ONCAB led to lower PaO₂/F_IO₂ ratio, lower compliance, higher plateau pressures, and longer postoperative ventilation.

Keywords: PaO(2)/F(I)O(2); off-pump coronary artery bypass grafting; on-pump coronary artery bypass grafting; thoracic fluid content.