SHOCK
Answer: B
The etiology of shock may not be initially apparent. Remember how a patient may “COHDe”: cardiogenic, obstructive, hypovolemic, distributive. These broad categories may help at the bedside to guide immediate intervention.
Goal-directed echocardiography (GDE) gives the emergency physician an immediate and dynamic snapshot of cardiac shock physiology through a systemic approach by asking yes or no questions:
The etiology of shock may not be initially apparent. Remember how a patient may “COHDe”: cardiogenic, obstructive, hypovolemic, distributive. These broad categories may help at the bedside to guide immediate intervention.
Goal-directed echocardiography (GDE) gives the emergency physician an immediate and dynamic snapshot of cardiac shock physiology through a systemic approach by asking yes or no questions:
- Examine the pericardial space. Is there fluid, or a fat pad?
- Is the RV a normal size and contracting normally?
- Is the septum a normal size and moving normally?
- Is the LV a normal size and contracting normally?
- Does the anterior MV leaflet approximate the septum (sign of good LV function)?
- Is the aortic root normal size; is there a dissection flap?
- Is the LA a normal size?
The general category, in conjunction with the above GDE questions can offer the clinician a presumptive diagnosis and direct him to the immediate priorities in management. A review of what cardiac ultrasound can do for you:
Cardiogenic shock
Cardiac Arrest
Acute coronary syndrome
Not sensitive or specific, but may offer more information, such as:
Obstructive shock
Tamponade
Tamponade is a clinical diagnosis that may be verified by echo:
Pulmonary Embolism
PE cannot be ruled out by echocardiography, but submassive and massive PE result in acute cor pulmonale:
Aortic Dissection
Transthoracic echo cannot rule out aortic dissection, but it might rule it in – consistent features include:
LV Function
A gross qualitative assessment of LV function can be made by visual inspection of:
Hypovolemic shock
Hypovolemia
In additional to a small, collapsing IVC, you may see:
Distributive shock
Shock may be multifactorial – for example, septic shock may include components of cardiogenic (inflammatory myocardial depression), obstructive (acute cor pulmonale from ARDS), hypovolemic (fluid losses), and distributive (SIRS). Knowledge of the components of shock will help to drive interventions and balance competing treatment priorities.
In our patient, we see moderate pericardial effusion, IVC dilation (from poor diastolic filling), and aortic root dilation, which together suggest aortic dissection with tamponade physiology. An aortic flap if seen would clench the diagnosis.
In summary and simplified: in the shocked, dyspneic, or arrested patient look for:
1. Pericardial effusion (with or without signs of tamponade)?
2. Enlarged RV (with or without hypokinesis and paradoxical septal motion)?
3. LV size and IVC size (e.g. small LV suggests hypovolemia)?
4. LV systolic function (mild/moderate/severe impairment)?
References
Bowra J. Basic echocardiography. Ultrasound for Critical Care. Sydney Adventist Hospital. 2011.
Schmidt GA, Koenig S, Mayo PH. Shock: ultrasound to guide diagnosis and therapy. Chest. 2012 Oct;142(4):1042-8. doi: 10.1378/chest.12-1297.
A similar case with cine loop:
http://onlinelibrary.wiley.com/store/10.1111/j.1553-2712.2008.00217.x/asset/supinfo/ACEM_217_sm_videoclips1.mov?v=1&s=829e36d48dbe222d45a0e75d19dbffa9c5ef2248
(From: Hayes A, Fluman KR, Sandhu HS, Liao MM. Emergency Bedside Ultrasound Diagnosis of Nontraumatic Cardiac Tamponade—A Case of Type A Aortic Dissection. Acad Emerg Med. 2008; 15(9): doi.org/10.1111/j.1553-2712.2008.00217.)
Another case of tamponade:
http://sonocloud.org/watch_video.php?v=SY4MAA9OKSMX
Tamponade with plethoric IVC:
http://sonocloud.org/watch_video.php?v=4DAHBHXD31AO
Cardiogenic shock
Cardiac Arrest
- Pulseless electrical activity (PEA): differentiates between “true PEA” (complete electromechanical dissociation – electrical activity without ventricular contraction) or “pseudo-PEA” (severely depressed cardiac output with measureable aortic pressures and ventricular activity)
- Echo can show mechanical capture in difficult emergency cardiac pacing cases
- Cardiac standstill on echo may guide termination of efforts
Acute coronary syndrome
Not sensitive or specific, but may offer more information, such as:
- Wall motion abnormalities
- Alternative causes of chest pain
- Mechanical complications of myocardial infarction
Obstructive shock
Tamponade
Tamponade is a clinical diagnosis that may be verified by echo:
- IVC dilation and diastolic RA or RV collapse
- Pericardial effusions are darker, present in more than one view, often all around the heart; pericardial fat is heterogeneous and lacks the characteristics of effusion
Pulmonary Embolism
PE cannot be ruled out by echocardiography, but submassive and massive PE result in acute cor pulmonale:
- RV size and motion: is the RV as large as the LV?
- Septal motion: RV pushes septum towards LV (‘D’ sign)
- IVC distended
Aortic Dissection
Transthoracic echo cannot rule out aortic dissection, but it might rule it in – consistent features include:
- Pericardial effusion
- Dilated aortic root
- Visible dissection flap
LV Function
A gross qualitative assessment of LV function can be made by visual inspection of:
- LV wall thickening in systole (if it no wall thickening, LV function is abnormal)
- Relative shrinking of the LV chamber in systole (qualitative ejection fraction)
- Systolic excursion (up-down movement) of the mitral annulus on the four chamber view
- Proximity of the anterior mitral valve leaflet to the interventricular septum in diastole
Hypovolemic shock
Hypovolemia
In additional to a small, collapsing IVC, you may see:
- LV is small
- LV is hyperdynamic with systolic obliteration of the chamber – the ‘kissing ventricle’
Distributive shock
- Refers to pathologic systemic vasodilation: neurogenic, anaphylaxis, adrenal insufficiency, toxic, or due to the systemic inflammatory response syndrome
- This will be a clinical diagnosis; echo can help to evaluate other or concomitant categories of shock
- Bringing it all together
Shock may be multifactorial – for example, septic shock may include components of cardiogenic (inflammatory myocardial depression), obstructive (acute cor pulmonale from ARDS), hypovolemic (fluid losses), and distributive (SIRS). Knowledge of the components of shock will help to drive interventions and balance competing treatment priorities.
In our patient, we see moderate pericardial effusion, IVC dilation (from poor diastolic filling), and aortic root dilation, which together suggest aortic dissection with tamponade physiology. An aortic flap if seen would clench the diagnosis.
In summary and simplified: in the shocked, dyspneic, or arrested patient look for:
1. Pericardial effusion (with or without signs of tamponade)?
2. Enlarged RV (with or without hypokinesis and paradoxical septal motion)?
3. LV size and IVC size (e.g. small LV suggests hypovolemia)?
4. LV systolic function (mild/moderate/severe impairment)?
References
Bowra J. Basic echocardiography. Ultrasound for Critical Care. Sydney Adventist Hospital. 2011.
Schmidt GA, Koenig S, Mayo PH. Shock: ultrasound to guide diagnosis and therapy. Chest. 2012 Oct;142(4):1042-8. doi: 10.1378/chest.12-1297.
A similar case with cine loop:
http://onlinelibrary.wiley.com/store/10.1111/j.1553-2712.2008.00217.x/asset/supinfo/ACEM_217_sm_videoclips1.mov?v=1&s=829e36d48dbe222d45a0e75d19dbffa9c5ef2248
(From: Hayes A, Fluman KR, Sandhu HS, Liao MM. Emergency Bedside Ultrasound Diagnosis of Nontraumatic Cardiac Tamponade—A Case of Type A Aortic Dissection. Acad Emerg Med. 2008; 15(9): doi.org/10.1111/j.1553-2712.2008.00217.)
Another case of tamponade:
http://sonocloud.org/watch_video.php?v=SY4MAA9OKSMX
Tamponade with plethoric IVC:
http://sonocloud.org/watch_video.php?v=4DAHBHXD31AO