Is ultrasound useful in shock?

Jo McDonnell

Aim

Highlight what you could have a go at…

Highlight what the sonoboys could do for you to help assess your patient

Shock

Clinical situation where there is hypoperfusion of the cells and tissues

Background

Patients with shock have high mortality rates and these rates are correlated to the amount and duration of hypotension.

Diagnosis and initial care must be accurate and prompt to optimise patient outcomes.

Studies have demonstrated that initial integration of bedside ultrasound into the evaluation of the patient with shock results in a more accurate initial diagnosis with earlier definitive treatment.

Bedside USS allows direct visualisation of pathology or abnormal physiological states.

Remember…

Ultrasound is a tool to aid diagnosis, but it won’t tell you everything…

When using it we should always have a clinical question you would like it to answer

Case 1:

75 yo male, unwell, chest pain, SOB, dirty productive cough

Lung cancer, angina and CCF

pyrexic at 38.2

HR 110

BP 80/50

Swollen pitting oedema bilaterally

Case 1-

What clinical question can the probe answer for you

with this patient?

RUSH

Rapid ultrasound in shock and hypotension- US protocol published with aim to differentiate classification of shock

Perera P et al, Emerg Med Clin N Am 2010

H eart

I vc

M orrisons pouch/FAST

A orta

P neumothorax

Himap-THE PUMP

Contractility- Hyperdynamic LV- sepsis, hypovolaemia Hypodynamic- late sepsis, cardiogenic shock What’s the RV like? – collapsing? Dilated?

Obstructive shock

Gross valvular dysfunction

Cardiac assessment

Parasternal long axis

Transducer at left sternal edge between 2nd -4th intercostal space

Probe marker pointing to patients R shoulder

Probe aligned along the long axis: from R shoulder to cardiac apex.

Useful view to assess contractility

Transducer at 4th-6th intercostal space in the midclavicular to anterior-axillary line.

Probe directed towards patient’s right shoulder with the marker directed towards the left shoulder.

Important view to give relative dimensions of L and R ventricle.

Normal ventricular diameter ratio of R ventricle to L ventricle is <0.7.

Pericardial Tamponade

Remember tamponade is a clinical diagnosis based on patient’s haemodynamics and clinical picture.

Ultrasound may demonstrate early warning signs of tamponade before the patient becomes haemodynamically unstable.

Haemodynamic effects Its PRESSURE NOT SIZE THAT COUNTS! Rate of formation affects pressure-volume relationship and

is therefore more important than volume of fluid.

Tamponade using ultrasound

A moderate-large effusion.

Right atrial collapse Atrial contraction normal in atrial systole Collapse throughout diastole or inversion is abnormal.

RV collapse during diastole when meant to be filling (‘scalloping’ seen)

Whats seen in the IVC…

hImap

IVC

Where to put the probe…

Probe position Subxiphoid Orientate probe in

longitudinal plane with probe indicator to patient’s head

Slightly to right of midline

Bowel gas causing problems….

The FAST view…

Probe goes longitudinally in right mid axillary line with marker towards head.

Look for IVC running longitudinally adjacent to the liver crossing the diaphragm

Track superiorly until it enters the RA confirms it’s the IVC not the aorta

Assessing the IVC

During inspiration, intrathoracic pressure becomes more negative, abdominal pressure becomes more positive, resultant increase in the pressure gradient between the supra and infra-diaphragmatic vena cava, increases venous return to the heart.

Given the extrathoracic IVC is a very compliant vessel this causes diameter of IVC to decrease with normal inspiration.

In patients with low intravascular volume, the inspiration to expiration diameters change much more than those who have normal or high intravascular volume.

Estimating the CVP

Right atrial pressures, representing central venous pressure, can be estimated by viewing the respiratory change in the diameter of the IVC.

American society of Echocardiography 2010 guidelines

Subxiphoid long; shocked and dry

Subxiphoid transverse view of the IVC and aorta

Complicating the picture

Valvular disease

Pulmonary hypertension

Increased intraabdominal pressure

hiMAp eFAST/Aorta scan

himaP

Multiple studies have shown ultrasound to be more sensitive than supine CXR for the detection of pneumothorax.

Sensitivities ranged from 86-100% with specificities from 92-100%.

Furthermore USS can be performed more rapidly at the bedside.

Detection with ultrasound relies on the fact that free air is lighter than normal aerated lung tissue, and thus will accumulate in the nondependent areas of the thoracic cavity. (ie anteriorly when patient is supine).

To get the lung window

Patient should be supine.

Use high frequency linear array or a phased array transducer.

Position in the midclavicular line, 3rd to 4th intercostal space with probe oriented longitudinally.

Position between ribs.

Pneumothorax

Abdominal and cardiac evaluation with sonography in the hypotensive patient (ACES)

Our case…

H- no pericardial effusion

I- 1cm and collapses >50%

M- Free fluid in the LUQ/RUQ

Aorta- no AAA

P – No pneumothorax

Next time…Give the probe a go…