Background Among patients with acute pulmonary embolism (PE) undergoing mechanical thrombectomy, the cardiac index (CI) is frequently reduced even among those without clinically apparent shock. The purpose of this study was to describe the mixed venous-to-arterial carbon dioxide gradient (CO2 gap), a surrogate of perfusion adequacy, among patients with acute PE undergoing mechanical thrombectomy. Methods This was a single-center retrospective study of consecutive patients with PE undergoing mechanical thrombectomy and simultaneous pulmonary artery catheterization over a 3-year period. Results Of 107 patients, 97 had simultaneous mixed venous and arterial blood gas measurements available. The CO2 gap was elevated (>6 mmHg) in 51% of the cohort and in 49% of patients with intermediate-risk PE. A reduced CI (≤2.2 L/min/m2) was associated with an increased odds (OR = 7.9; 95% CI 3.49-18.1, p < 0.001) for an elevated CO2 gap. There was an inverse relationship between CI and CO2 gap. For every 1 L/min/m2 decrease in the CI, the CO2 gap increased by 1.3 mmHg (p = 0.001). Among patients with an elevated baseline CO2 gap >6 mmHg, thrombectomy improved CO2 gap, CI, and mixed venous oxygen saturation. When the CO2 gap was dichotomized above and below 6, there was no difference in in-hospital mortality (9% vs. 0%; p = 0.10, HR: 1.24; 95% CI: 0.97-1.60; P = 0.085). Conclusions Among patients with acute PE undergoing mechanical thrombectomy, the CO2 gap is abnormal in nearly 50% of patients and inversely related to CI. Further studies should examine the relationship between markers of perfusion and outcomes in this population to refine risk stratification.

中文翻译：

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急性肺栓塞混合静脉-动脉二氧化碳梯度与心脏指数的关系

背景 在接受机械血栓切除术的急性肺栓塞（PE）患者中，即使在临床上没有明显休克的患者中，心脏指数（CI）也经常降低。本研究的目的是描述接受机械血栓切除术的急性肺栓塞患者的混合静脉-动脉二氧化碳梯度（CO2 间隙），这是灌注充足性的替代指标。方法 这是一项单中心回顾性研究，研究对象为连续 3 年接受机械血栓切除术和同步肺动脉插管术的肺栓塞患者。结果 107 名患者中，97 名同时进行了混合静脉和动脉血气测量。51%的队列患者和49%的中危PE患者的CO2缺口升高(＞6mmHg)。CI 降低（≤2.2 L/min/m2）与 CO2 缺口升高的几率增加相关（OR = 7.9；95% CI 3.49-18.1，p < 0.001）。CI 和 CO2 差距之间存在反比关系。CI 每降低 1 L/min/m2，CO2 间隙就会增加 1.3 mmHg (p = 0.001)。在基线CO 2 间隙升高>6mmHg的患者中，血栓切除术改善了CO 2 间隙、CI和混合静脉氧饱和度。当 CO2 差距分为高于和低于 6 时，院内死亡率没有差异（9% 与 0%；p = 0.10，HR：1.24；95% CI：0.97-1.60；P = 0.085）。结论 在接受机械取栓的急性PE患者中，近50%的患者CO2间隙异常，且与CI呈负相关。进一步的研究应检查该人群的灌注标志物与结果之间的关系，以完善风险分层。