Applied physiology at the bedside to drive resuscitation algorithms

Dynamic arterial elastance measured with pressure recording analytical method, and mean arterial pressure responsiveness in hypotensive preload dependent patients undergoing cardiac surgery: A prospective cohort study

BACKGROUND

Organ perfusion is a factor of cardiac output and perfusion pressure. Recent evidence shows that dynamic arterial elastance is a reliable index of the interaction between the left ventricle and the arterial system and, in turn, of left ventricular mechanical efficiency. A practical approach to the assessment of dynamic arterial elastance at the bedside is the ratio between pulse pressure variation and stroke volume variation, which might predict the effect of a fluid challenge on the arterial pressure in patients undergoing cardiac surgery.

OBJECTIVE

To evaluate the ability of dynamic arterial elastance, measured by the pressure recording analytical method (PRAM), to predict the response of mean arterial pressure (MAP) to a fluid challenge.

DESIGN

Prospective observational study.

SETTING

Cardiac surgery patients in a university hospital.

PATIENTS

Preload-dependent (pulse pressure variation ≥13%), hypotensive (MAP ≤65 mmHg) patients, without right ventricular dysfunction, at the end of cardiac surgery.

INTERVENTIONS

A 250 ml fluid challenge infused over 3 min.

MAIN OUTCOME MEASURES

A receiver-operating characteristic curve was generated to test the ability of the baseline (before fluid challenge) dynamic arterial elastance (primary endpoint) and all other haemodynamic variables (secondary endpoint) to predict MAP responsiveness (≥10% increase in MAP) after a fluid challenge.

RESULTS

Of 270 patients undergoing cardiac surgery, 97 (35.9%) were preload-dependent, hypotensive and received a fluid challenge. Of these 97 patients, 50 (51%) were MAP responders (≥10% increase in MAP) and 47 (48%) were MAP nonresponders (<10% increase in MAP). Baseline dynamic arterial elastance (mean ± SD) had an area under the curve of 0.64 ± 0.06 [95% confidence interval (CI), 0.53 to 0.73; P = 0.017]. A dynamic arterial elastance at least 1.07 with a grey zone ranging between 0.9 and 1.5 had 86% sensitivity (95% CI, 73 to 94) and 45% specificity (95% CI, 30 to 60) in predicting MAP increase.

CONCLUSION

In a hypotensive preload-dependent cardiac surgery cohort without right ventricular dysfunction, dynamic arterial elastance measured by PRAM can predict pressure response for values greater than 1.5 or less than 0.9.

An Assessment of Research Priorities to Dampen the Pendulum Swing of Burn Resuscitation

On June 17 to 18, 2019, the American Burn Association, in conjunction with Underwriters Laboratories, convened a group of experts on burn resuscitation in Washington, DC. The goal of the meeting was to identify and discuss novel research and strategies to optimize the process of burn resuscitation. Patients who sustain a large thermal injury (involving >20% of the total body surface area [TBSA]) face a sequence of challenges, beginning with burn shock. Over the last century, research has helped elucidate much of the underlying pathophysiology of burn shock, which places multiple organ systems at risk of damage or dysfunction. These studies advanced the understanding of the need for fluids for resuscitation. The resultant practice of judicious and timely infusion of crystalloids has improved mortality after major thermal injury. However, much remains unclear about how to further improve and customize resuscitation practice to limit the morbidities associated with edema and volume overload. Herein, we review the history and pathophysiology of shock following thermal injury, and propose some of the priorities for resuscitation research. Recommendations include: studying the utility of alternative endpoints to resuscitation, reexamining plasma as a primary or adjunctive resuscitation fluid, and applying information about inflammation and endotheliopathy to target the underlying causes of burn shock. Undoubtedly, these future research efforts will require a concerted effort from the burn and research communities.