Lab Case 345 interpretation

A 36 year old male BIBA as a priority 1 with altered GCS of 9. Patient is a known diabetic who received COVID vaccine 1 day prior and was vomiting.

Below is the patient VBG:

pH 6.7                                                Na 127 mmol/l

PCO2 24 mmHg                               K 8.3 mmol/l

HCO3 3.3 mmol/l                            Cl 100 mmol/l

B/e -35                                               Lactate 4.4

BSL 50 mmol/l                                  Cr 110 umol/l

  1. Describe and interpret the VBG
  2. If you decided this patient required intubation describe your approach

Answer

pH 6.7 severe acidaemia

HCO3 3.3 metabolic acidosis

Compensation – Expected PCO2 = 1.5 xHCO3 +8 = 12.95

AG = Na – (HCO3 + Cl) = 23.7

Delta ratio = Change in AG/Change in HCO3 = 0.56

Corrected K for pH = for every 0.1 drop in pH, there is a increase in K of 0.5 = 4.8

Corrected sodium = Na + Glucose -5/3 = 142

Raised lactate

The above VBG shows a severe metabolic acidosis with a mixed respiratory acidosis, with a raised AG and a delta ratio suggestive of an underlying NAGMA. The corrected potassium and sodium are within normal limits.  One needs to ensure monitoring of the potassium as treatment is given to correct the DKA and pH.

The likely cause for the HAGMA is a combined ketoacidosis and lactic acidosis. The lactic acidosis is due to dehydration secondary to vomiting.  The common causes for the NAGMA would be diarrhoea, RTA and normal saline. Addisons disease needs to be considered as well, but is unlikely in this case.

Things to consider if one decides to intubate this patient

  • Severe acidaemia for which patient is not fully compensating for
  • Intubation will worsen respiratory acidosis
  • Acidaemia alone can lead to arrhythmias and cardiac arrest
  • Hyperkalaemia worsened by succinylcholine
  • It will be difficult to match patients MV on a ventilator to adequately compensate for the acidosis
  • Altered GCS can be an indication for intubation but if the patient is compliant and maintaining their airway you have time! (and might not even need to intubate)

Preparation for intubation

  • Resuscitate prior to intubation – correct potassium, sodium HCO3 for pH and K correction. Fluid resus as patient will have markedly volume depletion
  • Prepare for cardiac arrest during induction
  • Modification of RSI – bag patient on induction, nondepolarizing muscle relaxants
  • Ventilation will require marked hyperventilation and higher than normal MV – RR to match patients current RR and TV 10ml/kg

 

 

 

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