Non-Invasive Shock: Differentiating Shock in the Emergency Department

Shock is a common final pathway for many disease states, occurring when oxygen and nutrient
delivery are not sufficient to maintain normal cellular function. The incidence of shock in
the emergency department (ED) is approximated to be 1-3% of ED patients(1), and it carries a
high mortality, ranging from 20-50% depending on the underlying cause of shock(2). Early
recognition and treatment of shock significantly improves outcomes in critically ill
patients(2, 3), and so the majority of efforts to this point have focused on identifying
patients with shock.

The many etiologies of shock may be grouped into several broader categories: cardiogenic,
distributive, hemorrhagic, hypovolemic, anaphylactic, and neurogenic. These categories cause
shock through different mechanisms, but they have a significant amount of clinical overlap
(4-7), making differentiating the cause of shock challenging for the emergency provider.
While some overlap also exists between the treatments for these categories, several have
vastly different therapeutic approaches. Since the early treatment of shock influences
outcomes(2, 3, 8, 9), identifying the correct etiology to treat should logically impact
outcomes as well, although this has not been studied in shock patients. However, Moore, et
al., did show that physicians were only able to correctly identify the cause of hypotension
in 25% of hypotensive patients in the ED, speaking to both the difficulty in diagnosing shock
etiologies and the high percentage of patients with undifferentiated shock(10).

Recently, a number of different devices and biomarkers have been suggested to have clinical
utility in differentiating shock and guiding resuscitation(11-13). These devices have
potential to aid in the differentiation of shock.

We will conduct a prospective, observational study of patients found to have shock and
"near-shock" physiology in the emergency department. We will identify patients meeting our
inclusion criteria which will identify shock and "near shock" patients. Inclusion criteria
will include: HR > 120, SBP < 90, or a shock index (HR/SBP) > 1 for at least five minutes.
Patients that do meet vital sign requirements, but have a lactate > 4 mmol/L, will also be
included.

Enrolled patients will undergo physiologic assessments using echocardiography, Microscan,
Non-invasive cardiac output monitor (NICOM), and extremity temperature device, as well as a
blood draw for biomarker assessment.

Inclusion Criteria:

- 18 years old

- determined to have shock physiology, which will be defined by vital sign requirements
including SBP < 90 despite appropriate resuscitation (e.g 2 L of normal saline) for at
least five minutes.

- Patients that do meet vital sign requirements and vasopressor initiation will also be
included

Exclusion Criteria:

- patients determined to have atrial fibrillation with rapid ventricular response or
supraventricular tachycardia, and the patient is discharged when the ventricular rate
is corrected.

- Patients will also be excluded if found to have to alcohol withdrawal, intoxication,
or psychiatric agitation without organic cause.

- Patients with SBP < 90 mm/hg who have been documented to have chronic low blood
pressure and their blood pressure is at baseline