Diagnostic Investigation and Prediction of Shock

Patients frequently present to emergency departments (EDs) with critical illness and injury. Shock is a life-threatening emergency, which requires urgent and rapid assessment, diagnosis and treatment, and can be classified into distributive-septic (62%), distributive-non-septic (4%), hypovolaemic (16%), cardiogenic (16%) and obstructive (2%). Sepsis is the leading cause of in-hospital death, and approximately 80% of these patients are admitted through the ED. In Chinese patients presenting to an ED in Hong Kong we have previously derived and validated a simple, a priori, pragmatic, quantitative method for recognising and classifying shock - Li's Practical Shock (LiPS) tool. This method has been validated against ICU admission and early mortality. However, it was derived in a single population in a single centre, and requires further validation and refined in other settings. Further, it does not sub-classify patients beyond 'normal, cold and warm shock', does not guide next steps in treatment, and the assessment of the peripheries is very subjective.

Evaluating the true underlying patient haemodynamics such as cardiac output, cardiac power and peripheral pressures gives vital clues to the hidden seriousness of illness and is a guide to better management. Few EDs in the world assess such haemodynamics. After evaluating a haemodynamic protocol one centre in Australia was able to reduce its death rate for septic shock at 30 days from 38% to 7%. We would like to evaluate whether the same would occur if applied across EDs in Wales. However, before we can do that we need to strengthen our understanding of haemodynamics, and of relevant protocols and non-invasive devices that help us to acquire such information.

There are many unanswered questions such as:

• Do Uscom-derived haemodynamic variables measured in the ED predict patients who at high risk of death, admission to ICU, and have shock?
• Does a refined LiPS definition better predict mortality and ICU admission?
• Do advanced haemodynamic predictors and/or refined LiPS predict better than experienced physicians the presence and classification of patients with shock, mortality and ICU admission?

This study will answer two main questions:

1. What is the probability that a patient has shock?
2. What type of shock does the patient have?

We propose:

1. To investigate whether advanced haemodynamic variables using USCOM predict 7-day mortality and ICU admission.
2. To investigate whether advanced haemodynamic variables using USCOM improve the detection and classification of shock.
3. To validate and refine Li's a priori Pragmatic Shock (LiPS) method for detecting and classifying shock.
4. To evaluate clinical experience for shock.
5. To inform on the feasibility of future studies

After ethics and institutional approval is obtained from we will conduct a prospective, single-centre, cohort study on 354 adult patients with possible shock associated with an acute illness or injury who present to the Emergency Department of the University Hospital of Wales, and follow them up for 7 days. 354 is a credible number to confirm that the strategy works.

Written consent will be obtained either from the patient or a relative wherever possible but a waiver of consent apply to patients who, because of confusion, unconsciousness or severe disability, may be unable to give consent. In these cases, consent will first be sought from a second doctor and/or nurse. Thereafter, consent will be obtained from the patient or a relative as soon as practically possible.

The challenge is to discover a strategy that has a sensitivity >67% and specificity >72% for determining in-hospital mortality in clinically deteriorating or potentially shocked patients.