Heterogeneous Cardiovascular Responses to Acute Mean Arterial Pressure Augmentation in Septic Shock: The Role of Ventriculo-Arterial Coupling
In septic shock, even with similar MAP targets, patients can have very different cardiovascular responses, which may affect their treatment outcomes.
Where it sits
this study against the rest of the vasopressin corpusSummary and findings
This study measured cardiovascular responses to mean arterial pressure (MAP) augmentation in 32 mechanically ventilated adults with septic shock. MAP was increased from approximately 65 to 85 mmHg using norepinephrine or vasopressin. The findings indicated heterogeneous responses, with 31% showing flow recruitment and 16% experiencing flow deterioration.
Abstract
<title>Abstract</title> <p>Background In septic shock, vasopressor-induced mean arterial pressure (MAP) augmentation is commonly used in septic shock to restore tissue perfusion, but patients may exhibit divergent cardiovascular responses despite achieving similar arterial pressure targets. We hypothesized that this heterogeneity reflects differences in ventricular adaptation to the acute increase in arterial load, as assessed by ventriculo-arterial (VA) coupling. Methods We conducted a prospective physiological observational study in mechanically ventilated adults with fluid-resuscitated septic shock undergoing transient MAP augmentation from approximately 65 to 85 mmHg. MAP was increased by norepinephrine dose escalation or by adding vasopressin, according to clinical judgment. Comprehensive transthoracic echocardiography was performed immediately before and after MAP augmentation. Patients were classified a priori according to relative changes in cardiac output (CO): flow recruitment (> 15% increase), stable flow (− 15% to + 15%), or flow deterioration (> 15% decrease). Changes in effective arterial elastance (Ea), end-systolic elastance (Ees), VA coupling (Ea/Ees), stroke volume, left ventricular ejection fraction (LVEF), myocardial performance index (MPI), isovolumetric contraction time (IVCT), and perfusion variables were analyzed. Results Thirty-two patients were included. Despite comparable increases in MAP, cardiovascular responses were heterogeneous: 10 patients (31%) exhibited flow recruitment, 17 (53%) maintained stable flow, and 5 (16%) developed flow deterioration. Patients with flow deterioration showed a greater increase in Ea and a smaller increase in Ees, resulting in worsening VA coupling (ΔEa/Ees + 0.22 [IQR 0.06–0.43]), whereas VA coupling remained stable or improved in patients with preserved or increased flow (p = 0.031). Flow deterioration was accompanied by reduced stroke volume, decreased LVEF, prolonged IVCT, and worsening MPI. Changes in VA coupling correlated with changes in IVCT (ρ = 0.790, p < 0.0001), MPI (ρ = 0.599, p = 0.0003), LVEF (ρ=−0.431, p = 0.014), and stroke volume (ρ=−0.418, p = 0.017). Tissue perfusion markers changed less consistently across response groups. Conclusions Acute MAP augmentation elicits heterogeneous cardiovascular responses in fluid-resuscitated septic shock. Flow deterioration is characterized by impaired ventricular adaptation to increased arterial load, reflected by worsening VA coupling and systolic performance.</p>
Background
This paper addresses the variability in cardiovascular responses to vasopressor-induced MAP augmentation in septic shock. Prior knowledge indicates that while MAP targets may be similar, individual patient responses can differ significantly. Understanding these differences is crucial for optimizing treatment strategies in septic shock management.
Methods
The study employed a prospective physiological observational design involving 32 mechanically ventilated adults with fluid-resuscitated septic shock. MAP was augmented from approximately 65 to 85 mmHg using norepinephrine or vasopressin based on clinical judgment. Primary outcomes included changes in cardiac output, effective arterial elastance, end-systolic elastance, and various echocardiographic measures.
Results
Despite comparable increases in MAP, the responses were heterogeneous: 31% of patients exhibited flow recruitment, 53% maintained stable flow, and 16% experienced flow deterioration. Patients with flow deterioration showed a significant increase in effective arterial elastance and a smaller increase in end-systolic elastance, leading to a worsening of VA coupling (ΔEa/Ees +0.22 [IQR 0.06–0.43], p=0.031).
Interpretation
The findings suggest that while MAP augmentation is a common practice, the resultant cardiovascular responses can vary widely among patients. The significant correlation between changes in VA coupling and other performance metrics indicates that flow deterioration may reflect a clinically relevant deterioration in cardiac function. However, the small sample size and observational nature of the study limit the strength of these conclusions.
Key findings
- 10 patients (31%) exhibited flow recruitment.
- 17 patients (53%) maintained stable flow.
- 5 patients (16%) developed flow deterioration.
- ΔEa/Ees +0.22 [IQR 0.06–0.43] in patients with flow deterioration.
- Changes in VA coupling correlated with changes in IVCT (ρ=0.790, p<0.0001).
- Flow deterioration was accompanied by reduced stroke volume and decreased LVEF.
Limitations
- small sample size of 32 patients
- observational study design
- potential confounding factors not controlled for
- single-site study may limit generalizability