Roles of angiotensin II as vasopressor in vasodilatory shock

Micro-lightguide spectrophotometry assessment of hepatic and intestinal microcirculation in endotoxemic rats during intravenous treatment with angiotensin II

INTRODUCTION

During septic shock, impairment of microcirculation leads to enhanced permeability of intestinal mucosa triggered by generalized vasodilation and capillary leak. Intravenous angiotensin II (AT-II) has been approved for the treatment of septic shock; however, no in-vivo data exist on the influence of AT-II on hepatic and intestinal microcirculation.

MATERIAL AND METHODS

Sixty male Lewis rats were randomly assigned to six study groups (each n = 10): sham, lipopolysaccharide-induced septic shock, therapy with low- or high-dose AT-II (50 or 100 ng/kg/min, respectively), and septic shock treated with low- or high-dose AT-II. After median laparotomy, hepatic and intestinal microcirculation measures derived from micro-lightguide spectrophotometry were assessed for 3 h and included oxygen saturation (SO2), relative blood flow (relBF) and relative hemoglobin level (relHb). Hemodynamic measurements were performed using a left ventricular conductance catheter, and blood samples were taken hourly to analyze blood gasses and systemic cytokines.

RESULTS

AT-II increased mean arterial pressure in a dose-dependent manner in both septic and non-septic animals (p < 0.001). Lower hepatic and intestinal SO2 (both p < 0.001) were measured in animals without endotoxemia who received high-dose AT-II treatment, however, significantly impaired cardiac output was also reported in this group (p < 0.001). In endotoxemic rats, hepatic relBF and relHb were comparable among the treatment groups; however, hepatic SO2 was reduced during low- and high-dose AT-II treatment (p < 0.001). In contrast, intestinal SO2 remained unchanged despite treatment with AT-II. Intestinal relBF (p = 0.028) and interleukin (IL)-10 plasma levels (p < 0.001) were significantly elevated during treatment with high-dose AT-II compared with low-dose AT-II.

CONCLUSIONS

A dose-dependent decrease of hepatic and intestinal microcirculation during therapy with AT-II in non-septic rats was observed, which might have been influenced by a corresponding reduction in cardiac output due to elevated afterload. While hepatic microcirculation was reduced during endotoxemia, no evidence for a reduction in intestinal microcirculation facilitated by AT-II was found. In contrast, both intestinal relBF and anti-inflammatory IL-10 levels were increased during high-dose AT-II treatment.

Multimodal strategy to counteract vasodilation in septic shock

Early initiation of a multimodal treatment strategy in the management of vasopressors during septic shock has been advocated to reduce delays in restoring adequate organ perfusion and to mitigate side effects associated with the administration of high-dose catecholamines. We provide a review that summarises the pathophysiology of vasodilation, the physiologic response to the vascular response, and the different drugs used in this situation, focusing on the need to combine early different vasopressors. Fluid loading being insufficient for counteracting vasoplegia, norepinephrine is usually the first-line vasopressor used to restore hemodynamics. Norepinephrine sparing is discussed in further detail through the concomitant use of adrenergic, vasopressinergic, and renin-angiotensin systems and the optimisation of endothelial reactivity with methylene blue. A blueprint for the construction of new studies is outlined to address the question of vasopressor selection and timing in septic shock.

The Role of Angiotensin II in Poisoning-Induced Shock-a Review

Background

Shock in drug poisoning is a life-threatening condition and current management involves fluid resuscitation and vasopressor therapy. Management is limited by the toxicity of high-dose vasopressors such as catecholamines. Clinical trials have shown the efficacy of angiotensin II as an adjunct vasopressor in septic shock. The aim of this review is to assess the use of angiotensin II in patients with shock secondary to drug overdose.

Methods

Medline (from 1946), Embase (from 1947) and PubMed (from 1946) databases were searched until July 2021 via OVID. Included studies were those with shock due to drug poisoning and received angiotensin II as part of their treatment regimen. Of the 481 articles identified, 13 studies (case reports and scientific abstracts) were included in the final analysis with a total of 14 patients. Extracted data included demographics, overdose drug and dosage, angiotensin II dosage, time of angiotensin II administration, haemodynamic changes, length of hospital stay, mortality, complications, cardiac function and other treatment agents used.

Results

Thirteen studies were included consisting of 6 case reports, 6 scientific abstracts and 1 case series. Overdose drugs included antihypertensives (n = 8), psychotropics (n = 4), isopropanol (n = 1) and tamsulosin (n = 1). Out of a total of 14 patients, 3 patients died. Ten patients had their haemodynamic changes reported. In terms of MAP or SBP changes, three patients (30%) had an immediate response to angiotensin II, four patients (40%) had responses within 30 min, one patient (10%) within two hours and two patients (20%) did not have their time reported. Two patients were shown to have direct chronotropic effects within 30 min of angiotensin II administration. The median hospital stay for patients was 5 days (IQR = 4). The time from overdose until angiotensin II administration ranged from 5 to 56 h. Other vasopressors used included phenylephrine, noradrenaline, adrenaline, vasopressin, dobutamine, dopamine, methylene blue and ephedrine. A median of 3 vasopressors were used before initiation of angiotensin II. Twelve patients received angiotensin II as their final treatment.

Conclusions

Angiotensin II may be useful as an adjunct vasopressor in treating shock secondary to drug poisoning. However, the current literature consisted of only very low-quality studies. To truly assess the utility of angiotensin II use in drug-induced poisoned patients, further well-designed prospective studies are required.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13181-022-00885-4.