Angiotensin II for Septic Shock Treatment

Angiotensin II for Septic Shock Treatment: Effects On Macro- and Microcirculation A Randomized, Controlled Pilot Trial (ANGSTROM Trial)

This study aims to investigate the effect of angiotensin II on microcirculation and peripheral perfusion in patients with septic shock.

Shock is a syndrome characterized by acute circulatory failure resulting in impaired peripheral tissue perfusion. Distributive shock is the most common type of shock and is usually caused by severe sepsis. Distributive shock is characterized by profound vasodilatation leading to decreased arterial blood pressure and impaired organ perfusion despite high cardiac output. The use of vasopressors is an essential management line for distributive sock. Two groups of vasopressors are usually used for management of shock: catecholamines and vasopressin-like peptides. There is a continuous need for other vasopressors because: 1- Available vasopressors have narrow therapeutic window. 2- Patients with severe hypotension refractory to the currently available classes usually die. A third system is usually engaged in the physiology of shock which is Renin-Angiotensin-aldosterone system. Angiotensin II is a natural hormone which is a potent vasopressor; moreover, angiotensin II stimulates the production of both antidiuretic hormone and adrenocorticotropin hormone. In a pilot study, angiotensin II was reported as an effective rescue vasopressor in septic shock patients on multiple vasopressors. Angiotensin II improved mean arterial pressure and helped in reduction of the doses of catecholamines. In a recent large randomized controlled trial, angiotensin II improved blood pressure in catecholamine-resistant distributive shock patients. Microcirculation is the primary site of oxygen and nutrient exchange. Maintenance of microcirculatory perfusion is a prerequisite for preservation of organ function. Multiple organ failure is common in patients with distributive shock despite maintenance of parameters of global perfusion due to disrupted microcirculatory perfusion. Furthermore, restoration of microcirculatory perfusion was correlated with improvement in survival. This study aims to investigate the effect of angiotensin II on peripheral microcirculation in patients with septic shock.

Patients will receive Angiotensin II at a starting dose of 20 ng/Kg/min. During the first 30 minutes after randomization, the angiotensin II infusion will be titrated to achieve a mean arterial pressure of 65-75 mmHg while the norepinephrine infusion will be withdrawn and stopped. Following a stabilization of 60 minutes, the angiotensin II infusion is titrated to achieve a mean arterial pressure of 85-95 mmHg. Following a 30 minutes wash-in period and a 60 minutes stabilization period, a third set of measurements will be taken. Then, the angiotensin II infusion will be withdrawn in small steps and replaced by a norepinephrine infusion which will then be titrated to achieve a mean arterial pressure of 65-75 mmHg. Then, the final set of measurements will be taken.

Patients will receive normal saline infusion in addition to norepinephrine infusion. The same mean arterial pressure levels (65-75 mmHg > 85-95 mmHg > 65-75 mmHg) will be achieved by titration of the norepinephrine infusion. Identical wash-in and stabilization periods will be kept as in the study group. Measurements will be taken at the same time points as in the study group. The maximum dose of norepinephrine applied will be 0.7 mcg/kg/min.

Mean flow index measured by Side stream dark field imaging optical probe (Microscan; MicroVision Medical, Amsterdam, Netherlands). Briefly, after gentle cleansing of the tongue by isotonic-saline-drenched gauze, avoiding pressure artifacts, 5 steady images of at least 20 seconds each will be obtained and stored under a random number. Offline blind analysis of each video will be done using a dedicated software (Automated Vascular Analysis 3.0; Academic Medical Center, University of Amsterdam, The Netherlands). The microvascular flow index (MFI) will be used to quantify microvascular blood flow. In this score, flow is characterized as absent (0), intermittent (1), sluggish (2), or normal (3), for each patient the values from 5 videos will be averaged. Since our investigation will be focused on small vessels, calculations will be separately performed for vessels with a diameter less than 20 ųm.

Proportion of perfused vessels measured by Side stream dark field imaging optical probe (Microscan; MicroVision Medical, Amsterdam, Netherlands). Briefly, after gentle cleansing of the tongue by isotonic-saline-drenched gauze, avoiding pressure artifacts, 5 steady images of at least 20 seconds each will be obtained and stored under a random number. Offline blind analysis of each video will be done using a dedicated software (Automated Vascular Analysis 3.0; Academic Medical Center, University of Amsterdam, The Netherlands)

Perfused vessel density measured by Side stream dark field imaging optical probe (Microscan; MicroVision Medical, Amsterdam, Netherlands). Briefly, after gentle cleansing of the tongue by isotonic-saline-drenched gauze, avoiding pressure artifacts, 5 steady images of at least 20 seconds each will be obtained and stored under a random number. Offline blind analysis of each video will be done using a dedicated software (Automated Vascular Analysis 3.0; Academic Medical Center, University of Amsterdam, The Netherlands)

Inclusion Criteria: Septic shock patients. Aged above 18 years. With cardiac index > 2.4 L/min/BSA 1.73 m2. On high dose vasopressors (defined as norepinephrine infusion above 0.1 mcg/Kg/min) Exclusion Criteria: Acute coronary syndrome. Impaired cardiac contractility Bronchospasm. Major burns Liver failure. Active bleeding.