A 37-year-old male has been admitted to your ICU following an explosion in his garage. He has suffered a mixture of partial and deep burns estimated at 35% total body surface area, and he has been intubated in the Emergency Department. After one hour of resuscitation in your unit he remains hypotensive with a blood pressure of 80/50 mmHg.

List the potential causes and outline how you would diagnose and manage them.
 

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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
  1. 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
      1. Increase fluid resuscitation rate
  1. Bleeding from occult/missed injury
    1. Review/repeat trauma imaging
      1. Blood product resuscitation, correction of coagulopathy
      2. Operative/Interventional radiology interventions to treat cause
  1. Sepsis
    1. Too early for burn sepsis – possible intraabdominal or thoracic blast injury
      1. Broad spectrum antibiotics and source control
  1. Distributive
    1. High cervical spine injury
      1. Review imaging, vasopressors
    2. Anaphylaxis to drugs
      1. Review history, examine for rash/bronchospasm, adrenaline
    3. Cyanide toxicity
      1. Mixed venous oxygen, empirical antidote administration
  1. Cardiogenic
    1. Takustubo, underlying cardiac disease, blast injury, myocardial toxins
      1. ECHO, ECG, Inotropic support
  1. Obstructive
    1. Tension pneumothorax
      1. CXR, drainage
    2. Abdominal compartment syndrome
      1. Bladder pressure, escharotomies, laparotomy/laparostomy
    3. Tamponade
      1. Echo and pericardiocentesis

Examiners Comments:

Frequently poorly structured answer, with a list of causes of hypotension, then repeated with diagnosis and management. Worked better when candidates classified each category of shock, then described individual diagnosis and management within each category. Often the question had not been carefully read, and the time already spent in ED and ICU was ignored; then a simplistic EMST initial approach to trauma was given.

Discussion

This question resembles Question 26 from the second paper of 2016, except the patient is not unconscious and there is no ABG to interpret.  

Let this be an exercise in generating differentials.

  • Wrong BP measurement (eg. arterial line is not zeroed)
  • Cardiogenic shock
    • Due to cytokine storm of severe burns
    • Due to carbon monoxide toxicity (i.e. severe tissue hypoxia)
    • Due to cyanide toxicity (i.e. mitochondrial failure)
    • Due to a myocardial infarction (due to increased myocardial oxygen consumption in context of burns, on top of pre-existing ischaemic heart disease)
  • Abdominal compartment syndrome (over-resuscitation)
  • Tension pneumothorax (explosion)
  • Spinal injury neurogenic shock (unrecognised due to unconsciousness)
  • Blood loss from some internal injury or due to DIC
  • Under-resuscitated burns shock (i.e. fluid shifts)
  • SIRS vasoplegia
  • Anaphylaxis to some drug given in hospital

If one were to offer more detail, one would have to tabulate one's answer, which would handily answer complaints about a lack of structure, because nothing says "structure" like a table.

Causes of Shock in the Acute Burns Patient
Type of shock Cause Diagnostic strategy Management
Artifact of measurement Arterial blood pressure measurement is inaccurate Compare with non-invasive measurement and physical examination
  • Re-zero and recalibrate the arterial line
  • Resite arterial line or change the transducer
Cardiogenic Cytokine-induced myocardial dysfunction
Alternatively, cardiac dysfunction can be associated with cyanide and carbon monoxide toxicity		 TTE, ECG, cardiac output measurement by PiCCO or PA catheter
  • Fluid resuscitation
  • Commence inotrope infusion
  • Correct rhythm if in AF
  Myocardial infarction TTE, ECG, cardiac enzymes
  • Consider IABP
  • Thrombolysis or anticoagulation likely contraindicated given the potential need for escharotomy or debridement
Obstructive Abdominal compartment syndrome Measure the intra-abdominal pressure;
calculate total fluid resuscitation (it is associated with over-resuscitation)
  • Maintain MAP with vasopressors
  • Consider opening the abdomen
  • Consider diuresis (although, at this stage the urine output is limited by poor renal perfusion)
 

Massive pulmonary embolism (unlikely - too early - more likely in the chronic recovery from burns)

 TTE, CVP trace, ECG, CTPA
  • Consider emergency embolectomy
  • Thrombolysis or anticoagulation likely contraindicated given the potential need for escharotomy or debridement
  Tension pneumothorax
(likely, if there the patient was in some sort of  explosion)

Physical examination;

CXR
  • Emergency decompression
  • Chest drain
Neurogenic Spinal injury due to fall; may have gone unrecognised given that the patient was found unconscious Physical examination features, CT, MRI
  • Commence vasopressor infusion
Hypovolemic Blood loss Examination of the patient, FBC, DIC screen
  • Replace blood products and red cells
  • Fluid resusiciation
  • Maintain normal acid-base balance and normothermia
  • Correct coagulopathy
  Under-resuscitated burns shock Compare fluid resuscitation with predicted expectations as based on the formulae
  • Replace appropriate volume
  • Aim for urine output 0.5-1.0ml/kg
  • Consider albumin, and to hell with the evidence
Distributive Vasoplegia due to SIRS SVRI measurements by PiCCO
  • commence vasopressor infusion; consider methylene blue
  Anaphylaxis Physical examination findings suggestive of angioedema
  • Adrenaline IM or as infusion
  • Withdrawal of the trigger substance
  • Corticosteroids and antihistamines
Cytotoxic Cyanide toxicity due to smoke inhalation Lactate levels; cyanide levels
  • hydroxycobalamin
  • dicobalt edetate
  • sodium thiosulfate
  • methaemoglobinaemia

References

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Huang, Peter P., et al. "Hypertonic sodium resuscitation is associated with renal failure and death." Annals of surgery 221.5 (1995): 543.

Sun, Ye-Xiang, et al. "Effect of 200 mEq/L Na+ hypertonic saline resuscitation on systemic inflammatory response and oxidative stress in severely burned rats." Journal of Surgical Research 185.2 (2013): 477-484.

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Walker, Steven C., et al. "Balanced Electrolyte Solution Reduces Acidosis as Compared to Normal Saline in the Resuscitation of Perioperative Burn Patients." Anesthesiology 95 (2001): A375