Angiotensin in ECMO patients with refractory shock

Refractory vasodilation and catecholamine resistance are common in septic shock. Changes in receptor signaling, excessive production of nitric oxide, and absolute or relative deficiencies of vasoactive hormones, including cortisol, vasopressin, and angiotensin II, play a role. Angiotensin II (Ang II) was previously available as a vasopressor but removed from the market in the 1990s. Interest was re-ignited following the Angiotensin II for the Treatment of Vasodilatory Shock (ATHOS-3) study, a randomized controlled trial in patients with refractory shock which confirmed that Ang II was effective at maintaining mean arterial pressure and reducing norepinephrine requirements without an increase in side effects [1]. Patients receiving renal replacement therapy also had improved survival and faster recovery of renal function [2]. Recent literature noted the potential role of Ang II in other types of shock [3].

The major physiological effects of Ang II relate to maintenance of hemodynamic stability and fluid and electrolyte regulation (Table 1). Angiotensinogen, the precursor of angiotensin, is produced primarily by the liver and released into the systemic circulation where it is converted to angiotensin I (Ang I). Ang I is cleaved into Ang II, predominantly by angiotensin converting enzyme (ACE), an endothelium bound protein that is primarily expressed in the pulmonary and renal capillary beds. In patients with acute respiratory distress syndrome, ACE insufficiency has been reported [4]. In veno-arterial ECMO, a proportion of blood bypasses the lungs, which further limits the conversion of Ang I to Ang II. Other conditions associated with reduced Ang II levels include Gram-negative sepsis where endotoxinemia can deactivate ACE. Importantly, low levels of Ang II and ACE are associated with increased mortality [5].

Table 1 Main physiological effects of angiotensin II

We report the successful management of seven patients (four male; mean age 36 years) with severe cardiorespiratory failure and refractory shock treated with extracorporeal membrane oxygenation (ECMO) who received Ang II in the context of the ATHOS-3 trial [1] or a compassionate use program (Table 2). Following initiation of Ang II, a profound effect on blood pressure was seen and the doses of vasopressors were reduced quickly. Time to cessation of vasopressors and catecholamines ranged from 16 h to 8 days. Six patients were discharged home alive.

Table 2 Patient characteristics

In conclusion, in patients with severe cardio-respiratory failure requiring ECMO, treatment with Ang II in addition to standard supportive care enabled rapid decatecholaminization. Underlying ACE deficiency may be a contributing factor. Further studies are necessary to confirm the findings.