Optimal target in septic shock resuscitation

Abstract

Septic shock presents a high risk of morbidity and mortality. Through therapeutic strategies, such as fluid administration and vasoactive agents, clinicians intend to rapidly restore tissue perfusion. Nonetheless, these interventions have narrow therapeutic margins. Adequate perfusion monitoring is paramount to avoid progressive hypoperfusion or detrimental over-resuscitation. During early stages of septic shock, macrohemodynamic derangements, such as hypovolemia and decreased cardiac output (CO) tend to predominate. However, during late septic shock, endothelial and coagulation dysfunction induce severe alterations of the microcirculation, making it more difficult to achieve tissue reperfusion. Multiple perfusion variables have been described in the literature, from bedside clinical examination to complex laboratory tests. Moreover, all of them present inherent flaws and limitations. After the ANDROMEDA-SHOCK trial, there is evidence that capillary refill time (CRT) is an interesting resuscitation target, due to its rapid kinetics and correlation with deep hypoperfusion markers. New concepts such as hemodynamic coherence and flow responsiveness may be used at the bedside to select the best treatment strategies at any time-point. A multimodal perfusion monitoring and an integrated analysis with macrohemodynamic parameters is mandatory to optimize the resuscitation of septic shock patients.

Keywords: Septic shock; capillary refill time (CRT); fluid therapy; lactate; microcirculation; resuscitation.

Figure 1

Relationship between fluid responsiveness, hemodynamic coherence, and flow responsiveness. This conceptual illustration indicates the link between fluid responsiveness and hemodynamic coherence as markers of macrocirculation and microcirculation, and flow responsiveness as a dynamic link between both territories.

Figure 2

Addition of a hemodynamic coherence or flow responsiveness test to a fluid management algorithm for patients with septic shock. CRT, capillary refill time; ScvO₂, central venous oxygen saturation; pCO₂ gap, central venous-arterial pCO₂ gradients.

Figure 3

Algorithm for rational fluid administration during septic shock resuscitation. In this algorithm, fluid administration is initiated after a trigger alerts the clinician of a hypoperfusion signal. If the patient is deemed as fluid responder, fluid challenge is performed, aiming at a predefined target (i.e., CRT normalization). The loop closes with the assessment of safety limits for fluid administration and new assessment of fluid responsiveness, until the target is met. DO₂/VO₂, oxygen delivery/consumption balance; CRT, capillary refill time.

Figure 4

Proposed multimodal assessment of patients’ perfusion status, resuscitation strategy and resuscitation target during septic shock. CRT, capillary refill time; ScvO₂, central venous oxygen saturation; pCO₂ gap, central venous-arterial pCO₂ gradients; DO₂/VO₂, oxygen delivery/consumption balance.