Question 2

College answer

1. Spurious

1. Damped or poorly functioning, zeroed, arterial line
2. Inappropriate sized cuff
   1. Check line, cuff size
   2. Measure second site, alternative modality

2. Hypovolemia

1. Review volumes of administered fluids to date
2. Confirm size and depth of burn
3. Check calculations for fluid resuscitation are correct
4. Rising haematocrit, ECHO findings

i. Increase fluid resuscitation rate

3. Bleeding from occult/missed injury

a. Review/repeat trauma imaging

i. Blood product resuscitation, correction of coagulopathy ii. Operative/Interventional radiology interventions to treat cause

4. Sepsis             
   1. Too early for burn sepsis – possible intraabdominal or thoracic blast injury
      1. Broad spectrum antibiotics and source control
5. Distributive
   1. High cervical spine injury
      1. Review imaging, vasopressors
   2. Anaphylaxis to drugs
      1. Review history, examine for rash/bronchospasm, adrenaline c. Cyanide toxicity

i. Mixed venous oxygen, empirical antidote administration

Cardiogenic

1. 1. Takustubo, underlying cardiac disease, blast injury, myocardial toxins
      1. ECHO, ECG, Inotropic support

5. Obstructive
   1. Tension pneumothorax
      1. CXR, drainage

b. Abdominal compartment syndrome

i. Bladder pressure, escharotomies, laparotomy/laparostomy

c. Tamponade

i. Echo and pericardiocentesis

Examiners comments: 

 Most candidates were not able to amalgamate the three crucial aspects of this patient i.e., trauma in a burns patient in the setting of a closed area explosion.

 Many focused solely on the burns with little reference to the trauma. 

 Many used a generic ABCD template without applying it to the patient.

 Many answer structures were haphazard with an initial list of the causes followed by the management, with the result that the management for a number of the differentials were missed.

 The best answers used a table or bulleted list approach taking about causes as well as management.

Discussion

Though the college describes this as an "explosion", it is highly unlikely that this patient was exposed to a blast wave (as usually household explosions are of the deflagration variety) and so the discussion will focus mainly on the investigations and management of burns-related hypotension. Blast injury is mentioned in the list as an aside, in response to the comment that most answers "focused solely on the burns with little reference to the trauma".

Thus:

Possible causes of shock in this patient (table adapted from "Causes of Shock in the Trauma Patient")

Type of shock	Cause	Diagnostic strategy
Artifact of measurement	Blood pressure measurement is inaccurate	Check pulse Check for disagreement between measurement modalities (eg. art line and NIBP)
Cardiogenic	Cardiac contusion (blast)	S3 Pericardial rub Anterior ST changes
	Myocardial infarction	ECG changes cardiac enzyme elevation
	Arrhythmia	Irregular pulse, bradycardia or tachycardia ECG
Obstructive	Cardiac tamponade	Raised JVP, CVP Pulsus paradoxus JVP rises on inspiration (Kussmaul's sign) Muffled heart sounds
	Tension pneumothorax	Surgical emphysema Tracheal deviation away from side of pneumothorax Quiet breath sounds on side of side of pneumothorax
	Fat embolism (blast)	Confusion Petechial rash over face, axillae, root of neck Hypoxia
Neurogenic	Spinal injury	hypotension without compensatory tachycardia warm extremities paralysis
Hypovolemic	Massive blood loss	Jugular venous pressure not visible Positive response to passive leg raise
	Massive fluid shift	As above (i.e. dynamic predictors suggest fluid responsiveness)
Distributive	Anaphylaxis (induction drugs)	angioedema urticaria facial swelling wheeze

Management, therefore, will consist of the following steps:

• Confirm blood pressure measurement invasively (i.e. insert an art line)
• Exclude immediately lifethreatening causes of shock:
  • Tension pneumothorax (examination)
  • Cardiac tamponade (TTE)
• Estimate fluid requirements using the modified Parklands Formula
• Assess fluid responsiveness via multimodal approach (combination of dynamic and static tests, including physical examination, ABG lactate, pulse pressure variation and passive leg raise)
• Offer a combination of crystalloid and colloid (expecting protein losses to be substantial)
• Vasopressors may be required (a vasodilated state formerly known as SIRS may develop)