Diastolic Shock Index: A clinically relevant predictor of poor outcome in septic shock?
/Ospina-Tascón GA, Teboul J-L, Hernandez G, et al. Diastolic shock index and clinical outcomes in patients with septic shock. Ann Intensive Care 2020;10(1):41. 10.1186/s13613-020-00658-8
P: A total of 761 patients from two separate cohorts found to have septic shock
I: Diastolic shock index
C: Comparison to a variety of well adopted markers of morbidity and mortality, including systolic shock index, SOFA score, APACHE II score, lactate, etc.
O: There was an association between increased diastolic shock index score and mortality at 90 days and performed similarly to more advanced measures of morbidity and mortality in septic shock including lactate levels and SOFA scores.
Background
Early recognition and resuscitation of patients in septic shock are critical skills for an emergency medicine physician. Many clinical decision-making tools have been developed and validated in their use to identify and define those who are in sepsis or septic shock, as well as predict a patient’s overall risk of morbidity and mortality, including tools like the SIRS criteria and SOFA score. However, in many cases, such tools require the combination of objective clinical and laboratory findings. In the setting of septic shock, hypotension is correlated with vasodilation that leads to altered blood flow (1). The pathologic vasodilation observed in sepsis is thought to result from failure of the vascular smooth muscle to constrict appropriately, leading to hypotension as well as tissue hypoperfusion (2). The diastolic blood pressure is determined by vascular tone, and thus it can be assumed that a decrease in the diastolic blood pressure should correlate with the pathologic vasodilation in septic shock. As a result, the authors of this study hypothesized that the relationship between heart rate and the diastolic blood pressure (i.e. the diastolic shock index) could provide providers a tool to quickly identify patients that are at risk for unfavorable outcomes.
Methods
This was a retrospective cohort study utilizing two separate patient cohorts. The first, considered the “primary cohort”, included 337 patients with septic shock requiring vasopressor support in a single ICU from a hospital in Columbia, South America. The second cohort included 424 patients with septic shock included in the recent randomized control trial, the ANDROMEDA-SHOCK trial (3). This cohort included patients from 28 hospitals in 5 different South American countries. Patients in the primary cohort were identified using the Surviving Sepsis Campaign: International Guidelines for Management of Severe Sepsis and Septic Shock: 2012 (4) while those included in the ANDROMEDA-SHOCK trial were identified using The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis 3.0) (5). Patients were excluded under the following criteria: patients <18 years old, pregnant patients, patients with liver failure (prothrombin time >15 seconds or INR > 1.5 and hepatic encephalopathy), advanced liver cirrhosis, atrial fibrillation, presence of ventricular dysrhythmia, use of pacemaker, and those with do-not-resuscitate orders.
The variable of interest was the diastolic shock index (DSI), calculated as the ratio between HR:Diastolic blood pressure. In the primary cohort, the DSI was calculated prior to the initiation of vasopressor therapy whereas the DSI was calculated at the randomization point for those in the ANDROMEDA-SHOCK cohort. In both populations, DSI was again calculated at the 2-hour, 4-hour, and 8-hour post vasopressor initiation. DSI levels were then distributed into 5 different quintiles. Researchers conducted a variety of different statistical analyses to calculate the relative risk of mortality associated with a given DSI quintile, as well as broke the DSI calculation into its components and studied the relationship of DSI, HR, and DAP with death at 90 days.
Results/Conclusion
A total of 761 patients were included in the analysis. The general characteristics between the two cohorts were comparable. Researchers found that increases in DSI were associated with increased risk of mortality 90 days in both study groups. When new partitions were performed using the components of DSI separately (diastolic blood pressure and heart rate), researchers found that there was a decrease in the relative risk of mortality as long as the HR decreased and/or the diastolic blood pressure increased or stayed the same (i.e., decreased DSI values). When compared to other measures of mortality in sepsis including lactate, SOFA, and APACHE II scores, DSI performance did not differ significantly. However, mean arterial pressure, isolated diastolic blood pressure, and the systolic shock index were found to be poor predictors of mortality. Researchers conducted a logistic regression model / Chi-Square test to evaluate early vasopressor initiation on 90-day mortality and found that early initiation of vasopressors was associated with more favorable outcomes in those with high DSI values.
Limitations
Though an interesting study, there are a variety of limitations that exist that may have contributed bias into the study. First, this study has a retrospective design. Though researchers attempted to control for a variety of variables, including volume of resuscitation prior to vasopressor initiation, volume of resuscitation from vasopressor initiation to 8 hours, initial arterial lactate, and a variety of additional variables, the retrospective nature of the study subjects it to bias. Additionally, this study lacks external validity and generalizability, as it took place on a single continent in a select few hospital settings. Similarly, the exclusion criteria are relatively strict, for example, researchers exclude patients with acute or chronic atrial fibrillation, an arrhythmia common in those who are acutely and critically ill. However, one may expect this to bias their results towards the mean, and by excluding these patients they may have lacked increased statistical power. Breaking up their DSI values into quintiles further suggests a lack of inherent statistical power in the study, and a study with a larger sample size is important in research moving forward. Last but not least, blood pressure measurements were obtained using noninvasive means, which may have led to inappropriate / inaccurate diastolic blood pressure measurements.
Takeaway
Further research on this topic should be considered in order to offer truly practice-changing evidence. However, the question asked by the researchers is one that has the potential to have a major clinical impact. The diastolic shock index is something that can be calculated less than 30 seconds after the patient enters the resuscitation bay. As such, it does not rely on various laboratory values in order to create a clinically beneficial prediction tool. If one’s index of suspicion is high enough for septic shock, and the patient has an elevated DSI, it may cause the provider to pause for a moment and consider aggressive resuscitation and possibly early vasopressor use. However, as was mentioned above, this study merely suggests a correlation between elevated DSI values and mortality, but it does not provide a practical cut off that can be universally applied to patients presenting with septic shock. This study should prompt the reader to think critically about the clinical and physiologic plausibility of the DSI and its utility in sepsis management. However, further research must be done to validate its clinical use.
References
Vincent JL, De Backer D. Circulatory shock. N Engl J Med. 2013;369(18):1726-34.
Siegel JH, Greenspan M, Del Guercio LR. Abnormal vascular tone, defective oxygen transport and myocardial failure in human septic shock. Ann Surg. 1967;165(4):504-17.
Hernández, Glenn, Gustavo A. Ospina-Tascón, Lucas Petri Damiani, Elisa Estenssoro, Arnaldo Dubin, Javier Hurtado, Gilberto Friedman et al. "Effect of a resuscitation strategy targeting peripheral perfusion status vs serum lactate levels on 28-day mortality among patients with septic shock: the ANDROMEDA-SHOCK randomized clinical trial." Jama 321, no. 7 (2019): 654-664.
Dellinger, R. Phillip, Mitchell M. Levy, Andrew Rhodes, Djillali Annane, Herwig Gerlach, Steven M. Opal, Jonathan E. Sevransky et al. "Surviving Sepsis Campaign: international guidelines for management of severe sepsis and septic shock, 2012." Intensive care medicine 39 (2013): 165-228.
Singer, Mervyn, Clifford S. Deutschman, Christopher Warren Seymour, Manu Shankar-Hari, Djillali Annane, Michael Bauer, Rinaldo Bellomo et al. "The third international consensus definitions for sepsis and septic shock (Sepsis-3)." Jama 315, no. 8 (2016): 801-810
Authorship
Written by: Josh Ferreri, MD, PGY-3 University of Cincinnati Department of Emergency Medicine
Peer Review and Editing: Jeffery Hill, MD MEd
Cite As
Ferreri, J. Hill, J. (March 30, 2023). Diastolic Shock Index: A clinically relevant predictor of poor outcome in septic shock? TamingtheSRU. https://www.tamingthesru.com/blog/2023/3/30/diastolic-shock-index-a-clinically-relevant-predictor-of-poor-outcome-in-septic-shock
