Introduction to Critical Care Ultrasound

Introduction to critical care US SAH & RNSH 2011 Critical Care Ultrasound Course

Goals of today's course
Understand critical care ultrasound
Understand its limitations (& your own)
Learn the basics of lung, IVC and cardiac sonography
Learn the arrest / shock / breathless algorithms
Perform a 3-minute screen

A real case (My road to Damascus)
shocked 30 yr old male
breathless & severe chest pain
mildly febrile , heart racing
unresponsive to O2 / fluid / antibiotics
Recovering from a common cold
no RFs for the usuals
getting worse in front of us

Initial investigations
CXR clear
ECG non specific
ABG markedly abnormal gas exchange

Atypical pneumonia? Or a PE?

OK, let ’ s get a scan.
Too unstable for CT / VQ scan
Cardiology: ‘ too busy ’
Radiology: ‘ we don ’ t do echo ’

#*%* !!!

Get out the ED US machine!
Lungs
IVC
Heart
Leg veins

Lungs clear

Non-collapsing IVC

RV > LV

Results
Lungs clear
Distended IVC
High pressure dilated RV > LV
DVT
Diagnosis?

Massive PE
Working diagnosis: massive PE (not atypical pneumonia)
Treatment: ED thrombolysis
Rapid improvement

Essential features of any bedside test in critical care
Improves accuracy of diagnosis in the critically ill (prehospital, ED, ICU)
Guides treatment / resuscitation / procedures
Rapid
Simple
Repeatable

BSL ECG O2 Sats

Bedside Critical Care US (CCUS)

Why?
A simple 3-minute ultrasound can assist in diagnosis and resuscitation
It may not give you the final diagnosis
But it buys you the time to perform a more detailed assessment once stabilised
EG a focused TTE
EG a CT scan

What is critical care US?
A rapid, patient -focused bedside US scan
Initial rapid scan: lungs / IVC / heart (curved probe) / other areas as appropriate
Then, after initial resuscitation, a more rigorous look at specific areas as indicated:
Heart / Lungs / Abdomen / Leg veins

Why isn't focused TTE enough?
Focused TTE
1. Just looks at heart
2. Cardiac probe / preset
3. Difficult windows
4. Slow learning curve
5. Takes several minutes
6. No cardiac windows = no information
7. Adapted from formal TTE
Rapid CCUS screen
1. Heart / lung / IVC / veins
2. Curved probe / abdo preset
3. Simple windows
4. Rapid learning curve
5. Takes 3 minutes
6. Works even if you can't see the heart / IVC
7. Purpose-built & validated for critical care

Does the screen really take 3 minutes?

Why isn't focused TTE enough?
Cardiac sonographer: 'the DDx between pericardial & left pleural fluid can be subtle'

Duh! Just look at the left thorax

This is why focused TTE isn ’ t enough
Cardiologists look after the heart -> echocardiography just looks at the heart
Critical care doctors look after the entire patient -> so our US scan should look at the patient , not just an organ

Whole-body ultrasound

Current standard of critical care ultrasound
LUNG
IVC
HEART
+other regions as appropriate

An important note
Cardiologist: 'Why do you want an urgent echo? Echo can't rule out a PE'
ED physician: 'But this will rule out a massive PE'
If it's a PE making the patient critically unwell, then it won't be a small one.

Top tip: bloody sick = bloody obvious We're not looking for small pneumothorax or mild CCF ('rule-in', not 'rule-out') If the patient is unstable, the US signs should be obvious

A formal echocardiogram
It doesn't use M-mode or Doppler
It doesn't look for subtle disease
It includes other windows & other organs to synthesize the answer
The holy grail
It is not validated in those with minor degrees of illness (eg mild CCF)
It will sometimes be wrong in the critically ill
It's just another tool
What this isn't

Limitations of critical care US
Algorithm: only validated in critically unwell patients
Patient: suboptimal position & still being resuscitated!
Time (none!)
Sonographer
Image acquisition
Image interpretation

So: the golden rules 1. 'Resus-only': Patient must be critically unwell: shocked / breathless / peri-arrest. That's because the US signs of some of these diseases are only reliably present if severe eg massive PE, severe pneumonia. If formal studies are needed after resus, get them. 2. Clinical context is paramount. Make a differential diagnosis list before you switch on the machine. All data must be considered (eg FBC with Hb = 4). 3. Only ask questions that you can answer. Leave the fancy stuff (eg valve disease) to others. 4. Repeat scans are crucial during resuscitation & each time clinical picture changes.

Golden rules 5. 90% = 100%: Every test has its limitations. In a periarrest patient, no study will be 100% accurate. If this bothers you, don't practise critical care. RNSH respiratory physician: 'Would you really thrombolyse a critically ill patient with suspected PE on the basis of bedside US?' ED physician answer: 'I spent years doing just that without the benefit of US. Anything that improves my accuracy suits me fine.'

Golden rules 6. When in doubt, be a doctor. You were a clinician before you were a sonographer. If the clinical picture & scan findings don’t agree, believe the clinical picture. ‘ What would I diagnose if I didn’t have an US machine?’

The golden rules 1. 'Resus-only' 2. Clinical context is paramount. 3. Only ask questions that you can answer. 4. Repeat scans are crucial. 5. 90% = 100% 6. When in doubt, be a doctor.

7. A fool with a stethoscope will be a fool with an ultrasound

Critical care US
It’s not the Holy Grail
Just another tool
Rapid
Safe
Accurate
Not difficult

Thanks to Daniel Lichtenstein Paul Atkinson Conn Russell Rob Reardon Vicki Noble Russell McLaughlin (for rule #7)

References
Blaivas M, Lyon M, Duggal S. A Prospective Comparison of Supine Chest Radiography and Bedside Ultrasound for the Diagnosis of Traumatic Pneumothorax. Acad Emerg Med 2005; 12(9): 844-9.
Jones AE, Craddock PA, Tayal VS, Kline JA: Diagnostic accuracy of left ventricular function for identifying sepsis among emergency department patients with nontraumatic symptomatic undifferentiated hypotension. Shock 24:513-7,2005.
Kaul S, Stratienko AA, Pollock SG, Marieb MA, Keller MW, Sabia PJ: Value of two-dimensional echocardiography for determining the basis of hemodynamic compromise in critically ill patients: a prospective study. J Am Soc Echocardiogr 7:598-606,1994.
Kohzaki S et al. The aurora sign: an ultrasonographic sign suggesting parenchymal lung disease. The British Journal of Radiology 76 (2003), 437–443
Lichtenstein D. Whole Body Ultrasonography in the Critically Ill. Springer, 2 nd ed. !st published 1992.
Lichtenstein D, Meziere G. A lung ultrasound sign allowing bedside distinction between pulmonary edema and COPD: the comet-tail artifact. Intensive Care med 1998; 24(12): 1331-4.
Lim et al. Ring-down artifacts posterior to the right hemidiaphragm on abdominal sonography: sign of pulmonary parenchymal abnormalities. J Ultrasound Med. 1999; 18: 403-410
Moore CL, Rose GA, Tayal VS, Sullivan DM, Arrowood JA, Kline JA: Determination of left ventricular function by emergency physician echocardiography of hypotensive patients. Acad Emerg Med 9:186-93,2002.
Plummer D, Heegaard W, Dries D, Reardon R, Pippert G, Frascone RJ: Ultrasound in HEMS: its role in differentiating shock states. Air Med J 22:33-6,2003.
Randazzo MR, Snoey ER, Levitt MA, Binder K: Accuracy of emergency physician assessment of left ventricular ejection fraction and central venous pressure using echocardiography. Acad Emerg Med 10:973-7,2003.
Reissig A, Kroegel C. Transthoracic Sonography of Diffuse Parenchymal Lung Disease: The Role of comet-tail artefacts. J Ultrasound Med 2003; 22(2): 173 -80.
Rose JS, Bair AE, Mandavia D, Kinser DJ: The UHP ultrasound protocol: a novel ultrasound approach to the empiric evaluation of the undifferentiated hypotensive patient. The American journal of emergency medicine 19:299-302,2001.
WINFOCUS WORKING GROUP 4. Shock state discussion paper, 3 rd world congress on US in EM and critical care, Paris 2007
Yanagawa Y, Nishi K, Sakamoto T, Okada Y: Early diagnosis of hypovolemic shock by sonographic measurement of inferior vena cava in trauma patients. The Journal of trauma 58:825-9,2005.
http://www.uptodate.com/contents/thoracic-ultrasound-indications-advantages-and-technique?source=preview&selectedTitle=4%7E150&anchor=H1492303#H1492303

PS Even if I hand't performed an US, I probably still would ’ ve thrombolysed him.

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Introduction to Critical Care Ultrasound

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