Question 20

College Answer

a) List the likely causes of this man's shock state.

• Hypovolaemia
  • Ongoing blood loss related to trauma including missed injuries
  • Ongoing blood loss related to the emergency splenectomy
  • Under-resuscitation prior to ICU admission
• Cardiogenic causes
  • Cardiac contusion
  • Myocardial ischaemia with pre-existing heart disease
  • Primary arrhythmia unlikely cause as rate only 140
• Obstructive causes
  • Cardiac tamponade
  • Tension pneumothorax
  • Fat embolism syndrome (less likely with compound tibial fracture)
  • PE (less likely in acute stage)
• Distributive shock states (sepsis, spinal) and anaphylaxis unlikely with cold peripheries

b) List the clinical features that would help distinguish between these likely causes

• Hypovolaemia (ongoing bleeding / under-resuscitation)
  • Jugular venous pressure not visible
  • Positive response to passive leg raise
• Cardiac tamponade
  • Evidence of pulsus paradoxus upon auscultation in determining blood pressure
  • Raised jugular venous pressure upon inspiration (Kussmaul's sign)
  • Muffled heart sounds
• Cardiac contusion
  • Evidence of heart failure (raised jugular venous pressure, fine inspiratory crackles) 25
• Tension pneumothorax
  • Surgical emphysema
  • Tracheal deviation away from side of pneumothorax
  • Quiet breath sounds on side of side of pneumothorax

c) What echocardiographic features are associated with the causes you have described?

• Hypovolaemia
  • Reduced left ventricle end diastolic area
  • LV end systolic cavity obliteration
  • Reduced inferior vena cava diameter with pulse variation
• Cardiac tamponade
  • Right atrial systolic collapse and right ventricular diastolic collapse
  • Increased pericardial fluid
  • Swinging heart
  • Dilated IVC
• Cardiac contusion
  • Regional wall motion abnormalities
• Tension pneumothorax
  • Reduced left ventricle end diastolic area
  • Distended superior vena cavae

Discussion

This is a question about the different causes of shock in trauma, and their relevant features, with a focus on the early use of ultrasound.

Questions a) and b) clearly favour the candidate who has recently done the EMST and is familiar with the ATLS manual, which is the best source for this sort of thing. I made my own summaries when I did that course.

Because questions a) and b) are rather straightforward, I will focus more on the echocardiographic investigation of shock in trauma.

A certain James Lai (FRCA, FANZCA) has published a brilliant set of slides for public delectation, which does this topic justice.

A 2011 study has also demonstrated that fluid assessment can be carried out quickly and effectively using IVC diameter and IVC respiratory variation, although in this study a surgical intensivist or an ultrasonographer (rather than an ED registrar) were performing the study. To address this concern, the same group later demonstrated that even a shaved ape could be trained to perform a limited goal-directed TTE.

Interestingly, there are also many studies of transoesophageal echo in trauma. One is tempted to salute the bravery of the man who would jam a TOE probe down into a trauma patient. However, it certainly seems to be helpful. A study comparing transthoracic and trasoesophageal assessment has demonstrated that TOE is significantly more accurate, and that TTE in severe chest trauma usually gives unsatisfactory images.

Ferrada, Paula, et al. "Transthoracic focused rapid echocardiographic examination: real-time evaluation of fluid status in critically ill trauma patients."Journal of Trauma and Acute Care Surgery 70.1 (2011): 56-64.

Ferrada, Paula, et al. "Limited transthoracic echocardiogram: so easy any trauma attending can do it." Journal of Trauma and Acute Care Surgery 71.5 (2011): 1327-1332.

Chirillo, Fabio, et al. "Usefulness of transthoracic and transoesophageal echocardiography in recognition and management of cardiovascular injuries after blunt chest trauma." Heart 75.3 (1996): 301-306.