Diastolic shock index and clinical outcomes in patients with septic shock

Abstract

Background: Loss of vascular tone is a key pathophysiological feature of septic shock. Combination of gradual diastolic hypotension and tachycardia could reflect more serious vasodilatory conditions. We sought to evaluate the relationships between heart rate (HR) to diastolic arterial pressure (DAP) ratios and clinical outcomes during early phases of septic shock.Methods: Diastolic shock index (DSI) was defined as the ratio between HR and DAP. DSI calculated just before starting vasopressors (Pre-VPs/DSI) in a preliminary cohort of 337 patients with septic shock (January 2015 to February 2017) and at vasopressor start (VPs/DSI) in 424 patients with septic shock included in a recent randomized controlled trial (ANDROMEDA-SHOCK; March 2017 to April 2018) was partitioned into five quantiles to estimate the relative risks (RR) of death with respect to the mean risk of each population (assumed to be 1). Matched HR and DAP subsamples were created to evaluate the effect of the individual components of the DSI on RRs. In addition, time-course of DSI and interaction between DSI and vasopressor dose (DSI*NE.dose) were compared between survivors and non-survivors from both populations, while ROC curves were used to identify variables predicting mortality. Finally, as exploratory observation, effect of early start of vasopressors was evaluated at each Pre-VPs/DSI quintile from the preliminary cohort.Results: Risk of death progressively increased at gradual increments of Pre-VPs/DSI or VPs/DSI (One-way ANOVA, p < 0.001). Progressive DAP decrease or HR increase was associated with higher mortality risks only when DSI concomitantly increased. Areas under the ROC curve for Pre-VPs/DSI, SOFA and initial lactate were similar, while mean arterial pressure and systolic shock index showed poor performances to predict mortality. Time-course of DSI and DSI*NE. dose was significantly higher in non-survivors from both populations (repeated-measures ANOVA, p < 0.001). Very early start of vasopressors exhibited an apparent benefit at higher Pre-VPs/DSI quintile.Conclusions: DSI at pre-vasopressor and vasopressor start points might represent a very early identifier of patients at high risk of death. Isolated DAP or HR values do not clearly identify such risk. Usefulness of DSI to trigger or to direct therapeutic interventions in early resuscitation of septic shock need to be addressed in future studies.

Letter to the Editor: Stroke volume is the key measure of fluid responsiveness

“…Accordingly, despite a calculated fall in cardiac output, the patient above may have significantly increased ventricular oxygen delivery with intravenous fluids, especially if there is co-morbid coronary artery disease and/or ventricular hypertrophy. These principles could partly explain recent data associating diminished diastolic shock index (i.e., HR divided by diastolic blood pressure) with improved outcome [ 4 ]. In other words, low HR and high diastolic pressure is a good prognosticator in septic shock.…”

The diastolic shock index works… but, what is it?

“…On the basis that "DAP depends [directly] on vascular tone and [inversely] on the duration of the cardiac cycle [i.e., the reciprocal of HR]" [1], the authors targeted the DAP, with the following goals: to assess the state of the vascular tone; to predict the severity and clinical outcomes of patients undergoing septic and other vasodilatory shock states; and to guide early vasopressor therapy.…”

“…If the DSI, in particular, is to represent the vascular tone [1], then the units of the quantity representing it should be of [Time −1 ] × [Pressure −1 ], which, evidently do not correspond to any mechanical property of the vascular wall related to its "tone" (whether it is wall tension, arterial resistance, or arterial compliance), which leads to the third and final point.…”

“…The recent study by Ospina-Tascón et al [ 1 ] presents a novel hemodynamic index—the “diastolic shock index” (DSI), defined as the ratio of heart rate (HR) and diastolic arterial pressure (DAP)—distinguishing itself from the “classical” and “modified” shock indices [ 2 ], which are based on the systolic and the mean arterial pressure, respectively.…”

Diastolic shock index (DSI) works… and it could be a quite useful tool

“…We thank Dr. Dalmau for his interest in our recent manuscript [1]. Vasodilatory shock is fundamentally characterized by a failure of peripheral vascular smooth muscle cells to constrict, resulting in altered tissue perfusion and organ dysfunction.…”