Background: Cardiac surgery is associated with a substantial risk of major adverse events. Although carbon dioxide (CO₂)-derived variables such as venous-to-arterial CO₂ difference (ΔPCO₂), and PCO₂ gap to arterial–venous O₂ content difference ratio (ΔPCO₂/C_(a−cv)O₂) have been successfully used to predict the prognosis of non-cardiac surgery, their prognostic value after cardiopulmonary bypass (CPB) remains controversial. This hospital-based study explored the relationship between ΔPCO₂, ΔPCO₂/C_(a−cv)O₂ and organ dysfunction after CPB.

Methods: We prospectively enrolled 114 intensive care unit patients after elective cardiac surgery with CPB. Patients were divided into the organ dysfunction group (OI) and non-organ dysfunction group (n-OI) depending on whether organ dysfunction occurred or not at 48 h after CPB. ΔPCO₂ was defined as the difference between central venous and arterial CO₂ partial pressure.

Results: The OI group has 37 (32.5%) patients, 27 of which (23.7%) had one organ dysfunction and 10 (8.8%) had two or more organ dysfunctions. No statistical significance was found (P = 0.84) for ΔPCO₂ in the n-OI group at intensive care unit (ICU) admission (9.0, 7.0–11.0 mmHg), and at 4 (9.0, 7.0–11.0 mmHg), 8 (9.0, 7.0–11.0 mmHg), and 12 h post admission (9.0, 7.0–11.0 mmHg). In the OI group, ΔPCO₂ also showed the same trend [ICU admission (9.0, 8.0–12.8 mmHg) and 4 (10.0, 7.0–11.0 mmHg), 8 (10.0, 8.5–12.5 mmHg), and 12 h post admission (9.0, 7.3–11.0 mmHg), P = 0.37]. No statistical difference was found for ΔPCO₂/C_(a−cv)O₂ in the n-OI group (P = 0.46) and OI group (P = 0.39). No difference was detected in ΔPCO₂, ΔPCO₂/C_(a−cv)O₂ between groups during the first 12 h after admission (P > 0.05). Subgroup analysis of the patients with two or more failing organs compared to the n-OI group showed that the predictive performance of lactate and Base excess (BE) improved, but not of ΔPCO₂ and ΔPCO₂/C_(a−cv)O₂. Regression analysis showed that the BE at 8 h after admission (odds ratio = 1.37, 95%CI: 1.08–1.74, P = 0.009) was a risk factor for organ dysfunction 48 h after CBP.

Conclusion : ΔPCO₂ and ΔPCO₂/C_(a−cv)O₂ cannot be used as reliable indicators to predict the occurrence of organ dysfunction at 48 h after CBP due to the pathophysiological process that occurs after CBP.

背景：心脏手术与重大不良事件的重大风险相关。尽管二氧化碳 (CO ₂ ) 衍生变量，例如静脉-动脉 CO ₂差异 (ΔPCO ₂ ) 和 PCO ₂间隙与动脉-静脉 O ₂含量差异比 (ΔPCO ₂ /C _(a-cv) O ₂ ) 已成功用于预测非心脏手术的预后，但其在体外循环 (CPB) 后的预后价值仍存在争议。这项基于医院的研究探讨了 CPB 后 ΔPCO ₂、ΔPCO ₂ /C _(a-cv) O ₂与器官功能障碍之间的关系。

方法：我们前瞻性地招募了 114 名接受 CPB 的择期心脏手术后的重症监护病房患者。根据CPB后48小时是否发生器官功能障碍，将患者分为器官功能障碍组（OI）和非器官功能障碍组（n-OI）。ΔPCO ₂定义为中心静脉和动脉 CO ₂分压之间的差值。

结果：OI组有37例（32.5%）患者，其中27例（23.7%）有1个器官功能障碍，10例（8.8%）有2个或2个以上器官功能障碍。没有发现统计学意义（磷= 0.84)重症监护病房 (ICU) 入院时 n-OI 组的ΔPCO ₂ (9.0, 7.0–11.0 mmHg) 和 4 (9.0, 7.0–11.0 mmHg), 8 (9.0, 7.0–11.0 mmHg)和入院后 12 小时（9.0、7.0–11.0 mmHg）。在 OI 组中，ΔPCO ₂也显示出相同的趋势 [ICU 入院 (9.0, 8.0–12.8 mmHg) 和 4 (10.0, 7.0–11.0 mmHg), 8 (10.0, 8.5–12.5 mmHg) 和入院后 12 h ( 9.0、7.3–11.0 毫米汞柱）、磷= 0.37]。在 n-OI 组中未发现 ΔPCO ₂ /C _(a-cv) O _{2 的}统计学差异（磷 = 0.46) 和 OI 组 (磷= 0.39）。在入院后的前 12 小时内，两组之间的ΔPCO ₂、ΔPCO ₂ /C _(a-cv) O ₂没有检测到差异（磷> 0.05）。与 n-OI 组相比，有两个或更多器官衰竭的患者的亚组分析表明，乳酸和碱过量 (BE) 的预测性能有所改善，但 ΔPCO ₂和 ΔPCO ₂ /C _(a-cv) O ₂的预测性能没有改善. 回归分析显示入院后 8 小时的 BE（优势比 = 1.37，95%CI：1.08-1.74，磷 = 0.009) 是 CBP 后 48 小时器官功能障碍的危险因素。

结论 ：由于CBP后发生的病理生理过程，ΔPCO ₂和ΔPCO ₂ /C _(a-cv) O ₂不能作为预测CBP后48小时器官功能障碍发生的可靠指标。