Re-thinking resuscitation: leaving blood pressure cosmetics behind and moving forward to permissive hypotension and a tissue perfusion-based approach

Abstract

Definitions of shock and resuscitation endpoints traditionally focus on blood pressures and cardiac output. This carries a high risk of overemphasizing systemic hemodynamics at the cost of tissue perfusion. In line with novel shock definitions and evidence of the lack of a correlation between macro- and microcirculation in shock, we recommend that macrocirculatory resuscitation endpoints, particularly arterial and central venous pressure as well as cardiac output, be reconsidered. In this viewpoint article, we propose a three-step approach of resuscitation endpoints in shock of all origins. This approach targets only a minimum individual and context-sensitive mean arterial blood pressure (for example, 45 to 50 mm Hg) to preserve heart and brain perfusion. Further resuscitation is exclusively guided by endpoints of tissue perfusion irrespectively of the presence of arterial hypotension ('permissive hypotension'). Finally, optimization of individual tissue (for example, renal) perfusion is targeted. Prospective clinical studies are necessary to confirm the postulated benefits of targeting these resuscitation endpoints.

Figure 1

Hydrostatic pressures in circulation. Microcirculation pressure is indicated by shaded area. Values shown to the left and right indicate arterial and venous portions of circulation, respectively. Unlabeled solid curve in both frames represents a normal pressure profile. Left panel: curve A represents maximal arteriolar constriction, and curve B represents arteriolar dilation. Right panel: curves A and B represent decreasing arterial and increasing venous pressures, respectively. Reprinted with permission from the American Physiological Society [21].

Figure 2

Physiologic components of arterial blood pressure (a) and correlation between mean arterial blood pressure and cardiac index (b) in 39 patients with sepsis. The number of pulmonary artery catheter measurements was 15,836.

Figure 3

Hierarchy of resuscitation endpoints. MAP, mean arterial blood pressure.

Figure 4

Bedside considerations of macrocirculatory versus tissue perfusion-based resuscitation endpoints. Hb, hemoglobin; P_aO₂, arterial partial pressure of oxygen; S_aO₂, arterial oxygen saturation; StO₂, tissue (muscle) oxygen saturation.