Evaluating the adequacy of fluid resuscitation in patients with septic shock: controversies and future directions

Stroke Volume Optimization: Utilization of the Newest Cardiac Vital Sign: Considerations in Recovery from Cardiac Surgery

The hemodynamic monitoring landscape is rapidly evolving from pressure-based and static parameters to more blood flow-based and dynamic parameters. Consensus guidelines for cardiac surgery state that the pulmonary artery catheter is neither required nor helpful in most patients. In the meantime, critical care has been searching for the alternatives to the pulmonary artery catheter and protocols for use. Best available evidence for any protocol developed suggests the inclusion of stroke volume optimization to determine fluid responsiveness. Additional strategies to using stroke volume to optimize hemodynamics, including case studies, are discussed.

Intensity of Vasopressor Therapy for Septic Shock and the Risk of In-Hospital Death

CONTEXT

Given the high mortality of 30%-60% associated with septic shock, distinguishing which patients do or do not have a reasonable chance of surviving with aggressive treatment could help clinicians and families make informed decisions.

OBJECTIVES

To determine if intensity of vasopressor therapy accurately predicts in-hospital death.

METHODS

This observational cohort study analyzed in-hospital mortality as a function of intensity of vasopressor therapy in a consecutive series of adults with septic shock treated over a four-year period. Receiver operating characteristic curve analysis assessed the overall strength of the intensity-mortality relationship.

RESULTS

A total of 808 patients with septic shock experienced an in-hospital death rate of 41.0% (331/808; 95% CI, 38.5%-44.5%). The greater the peak number of vasopressors required, the higher the death rate, which reached 92.3% (12/13; 95% CI, 79.4%-100.0%) when three different pressors were being infused at full dose. The receiver operating characteristic curve analysis revealed that number of simultaneous vasopressors and vasopressor dose load performed equally well in predicting death or survival.

CONCLUSION

When a standard full dose of a vasopressor fails to normalize blood pressure in a patient with septic shock, escalation begins to yield diminishing returns as the dose and multiplicity of agents approach practical upper limits. Although it is not possible to specify a precise cutoff for limiting vs. intensifying therapy, a mortality of 80% or higher-characterized by two or more concurrent vasopressors at full dose-should prompt shared decision making with the patient's family.

Exploring hemodynamics: a review of current and emerging noninvasive monitoring techniques

The lack of randomized controlled trials suggesting improved outcomes with pulmonary artery catheter use and pressure-based hemodynamic monitoring has led to a decrease in pulmonary artery catheter use. However, an increasing amount of literature supporting stroke volume optimization (SVO) has caused a paradigm shift from pressure-based to flow-based techniques. This article discusses emerging flow-based techniques, supporting evidence, and considerations for use in critical care for methods such as Doppler, pulse contour, bioimpedance, bioreactance, and exhaled carbon dioxide. Regardless of the device chosen, the SVO algorithm approach should be considered, and volume challenges should be guided by dynamic assessments of fluid responsiveness.

Reliability of central venous pressure to assess left ventricular preload for fluid resuscitation in patients with septic shock

Background

Initial fluid resuscitation is an important hemodynamic therapy in patients with septic shock. The Surviving Sepsis Campaign Guidelines recommend fluid resuscitation with volume loading according to central venous pressure (CVP). However, patients with septic shock often develop a transient decrease in cardiac function; thus, it may be inappropriate to use CVP as a reliable marker for fluid management.

Methods

We evaluated 40 adult patients with septic shock secondary to intra-abdominal infection who received active treatment and were monitored using transthoracic echocardiography (TTE) and CVP for 2 days after admission to our intensive care unit (ICU). We measured left ventricular end-diastolic diameter (LVEDD), left atrial diameter (LAD), and the pressure gradient of tricuspid regurgitation (TR∆P). The shock status was treated with volume loading and inotrope/vasopressor administration according to the TTE findings. We assessed left ventricular fractional shortening (LVFS) as an index of left ventricular contractility and TR∆P as an index of right ventricular afterload and then examined the correlation between CVP and LVEDD/LAD/TR∆P.

Results

LVFS decreased to ≤30% in 42.5% and 27.5% of patients with septic shock, and severe left ventricular dysfunction with LVFS ≤20% developed in 12.5% and 15.0% of patients on the first and second ICU days, respectively, despite the use of inotropes/vasopressors. Mild pulmonary hypertension as indicated by TR∆P ≥30 mmHg was present in 27.5% and 30.0% of patients on their first and second ICU days, respectively. There was no significant correlation between CVP and LVEDD/LAD/TR∆P. The hospital mortality rate in this study was 10.0%, although the predicted mortality based on the Acute Physiology and Chronic Health Evaluation II score was 58.7%.

Conclusions

Our results suggest that CVP is not a reliable marker of left ventricular preload for fluid management during the initial phase of septic shock. Assessment of left ventricular preload, right ventricular overload, and left ventricular contractility using TTE seems to be more informative than the measurement of CVP for fluid resuscitation since some patients developed left ventricular dysfunction and/or right ventricular overload.