THE WRITTEN EMERGENCY MEDICINE FELLOWSHIP COURSE
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OK. Now, there are a couple of caveats to this week's solve.

1. That wasn't a particularly difficult blood gas. You need to be able to work through this level at a minimum for the exam.
2. The answer below is written without a calculator. So most of the calculations are generally accurate (i.e. close estimations)
3. You won't get a question like this in the real exam, that is a "interpret this ABG to it's fullest extent". BUT, when you see an ABG you should have a systematic approach to both interpreting it, and to inferring the necessary medical facts from it. That's what this week's exercise is designed to test.

So, see how your answer compares. Questions, comments etc via the VSG please.
1. ACID-BASE BALANCE
 
critical acidaemia
critical hypocarbia
critically low bicarbonate
            expect CO2 = 8 + 1.5 x 3.1 = 12.5 .: diagnose appropriate resp compensation
            ANION GAP = 126 – 93 = 33 HIGH
            DELTA RATIO = (33 – 12)/(24 – 3) = 21/21 = 1.0 .: Dx Isolated RAGMA
 
Therefore diagnose RAGMA with appropriate respiratory compensation.
 
2. Aa GRADIENT
 
FiO2 = .4 .: FiO2 = 300mmHg
Aa grad           = 300 – 1.25 X 13 – 260
                        = 300 – 16 – 260 = 24mmHg
Expect for an 11yo = 6-7mmHg. .: this is slightly raised in the context of critical illness and is inconsistent with a presentation of asthma
 
3. ELECTROLYTES
 
Moderate hyponatraemia
            Correct for glucose = 126 + (31 – 5)/3 = 134mmol/L
Critical hypokalaemia – danger of arrhythmia
            Correct for pH K+ should equal 5 + 5x0.5 = 7.5mmol/L
            .: this patient has a life threatening hypokalaemia
Mild hypochloraemia
            Electrical equilibration for NAGMA
Normal renal indices
Hyperlactataemia
            Possible type A – dehydration
            Type B1 – intercurrent sepsis
            Type B2 – salbutamol use
Critical hyperglycaemia
 
4. INTERPRET
 
Therefore:
RAGMA plus hyperglycaemia suggests new Dx type I diabetes
This patient is critically ill
Issues:
  1. Diabetes requires insulin (actrapid) 0.05-0.1IU/kg.hr infusion
  2. Life threatening hypokalaemia will worsen with insulin & as pH corrects, therefore replace early 10mmol repeat to maintain K+ >3.5mmol/L on VBG
  3. Intercurrent medical issues:
    1. Sepsis: cover Abx eg ceftriaxone 50mg/kg
    2. Dehydration: gentle fluid resuscitation
      1. This child is shocked – bolus 10-20ml/Kg crystalloid for cap refill 2s and HR <120
      2. Then maintenance fluid + 5-10% (I personally would use Hartmann’s in this instance as it is Eukalaemic – Luke)
  4. Urgent consults from:
    1. Intensive care
    2. Paediatrics/endocrinology
  5. Clear explanation to parents of serious nature of event, document same

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