College answer

a) Type of fluid: 
Fluid resuscitation of patient with moderate to severe burns consists of an isotonic crystalloid solution, such as Hartmann‟s solution or plasmalyte. Large volumes of 0.9% NaCl may be associated with hyperchloremic metabolic acidosis. 
The colloids (albumin) are more expensive, and do not improve survival, compared to crystalloids. 
The use of hypertonic saline does not provide better outcomes than isotonic saline. 
 
    Estimating fluid requirements:                                
No formula provides a precise method for determining the burn victim's fluid requirements; the formulas described provide only a starting point and guide to initial fluid resuscitation. Patient age, severity of burns and co-morbidities can substantially alter the actual fluid requirements of individual patients. 
Parkland (or Baxter or consensus) Formula (most widely used):  
Fluid requirement (ml) = 4 x body weight x percentage of burns. (Only deep) 
One half of the calculated fluid is given over the first eight hours and the remaining over the next 16 hours. 
The rate of infusion should be as constant as possible; sharp decrease in infusion rates can cause vascular collapse and increase in edema. 
Modified Brooke Formula: Fluid requirement (ml) over the initial 24 hours = 2 x body weight x percentage of burns. 
This formula may reduce the total volume used in fluid resuscitation without causing harm. 
Following initial resuscitation, IV fluids are administered to meet baseline fluid needs and maintain urine output. 
Care should be taken to avoid fluid overload, as associated with pulmonary edema, peripheral edema leading to compartment syndrome. 
Inadequate resuscitation suggested by poor urine output should be managed by judicious fluid boluses and an increase in the infusion rate. 
 
b) List the diagnostic possibilities  
Cardiogenic Shock (severe myocardial suppression caused by burns, pre-existing myocardial dysfunction) 
Cyanide toxicity 
Compartment Syndrome, including abdominal compartment 
Carbon monoxide poisoning 
Blast injury 
Ingestion of toxins (ethylene glycol, methanol, salicylates) 
Acute Liver Failure 
 
Additional Examiners' Comments: 
Most of the candidates answered this question very well. Candidates who did not pass showed knowledge gaps, poor synthesis of knowledge and poorly structured answers. 

Discussion

This question closely resembles Question 21 from the first paper of 2014, with the exception of the fact that this time an ABG was also offered.The ABG does not add very much to the process of answering this question, and therefore the discussion section for Question 21 is reproduced here with minimal modification.A detailed dissection of fluid resuscitation for the burns patient  is performed in the Required Reading section. Physiologic consequences of burns is also covered there. The ABG looks like a metabolic acidosis, which would accompany any sort of shock state - and so the "Causes of Shock in the Acute Burns Patient" table was still relevant here.

a)

In brief:

Fluid resuscitation end point:

• urine output of 0.5-1.0 ml/kg/hr (Paratz et al, 2014)
• MAP >65mmoHg

Choice of fluids:

• Resuscitation should use a balanced solution to avoid hyperchloraemic acidosis (Walker et al, 2001)
• Most formulae recommend Ringer's Lactate; the locally available version is Hartmanns
• The disadvantage of crystalloid is the potential need for massive volume
• Historically, significantly more fluid is given to burns patients  then is predicted by any formula (Mitra et al, 2006). This is known as "fluid creep" and is associated with significant complications, of which the most serious is abdominal compartment syndrome.
• Colloid (eg. albumin) is also recommended by many of the formulae
• The advantage of colloid is that it may alleviate "fluid creep" and achieve haemodynamic goals more rapidly and with less volume
• There is no evidence that albumin improves survival or organ dysfunction (Melinyshyn et al, 2013)
• The theoretical advantage of hypertonic saline is earlier achievement of haemodynamic goals and the avoidance of burns-associated hypernatremia. However, hypertonic saline solutions were associated with a fourfold increase in the risk of renal failure and a twofold increase in the risk of death (Huang et al, 1995)

Resuscitation formulae

It is probably worth adding that this patient is at high risk of inhalational injury. He was unconscious, and sharing a small enclosed space with his fire. Naver et al (1985) demonstrated that patients with smoke inhalation injury and airway burns require a larger volume of fluid resuscitation. The total volume is increased up to 35% - 65%.

b)

Causes of shock in the unconscious burns patient with metabolic acidosis

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

In more detail: