Lab Case 177 Interpretation

30 year old female presents from an inpatient drug rehabilitation facility after being drowsy overnight and having low saturation.  She is intubated on arrival.

Metabolic Acidaemia pH7.2 and HCO3 12

Compensation – Expected PCO2 =1.5xHCO3+8 =26 (actual PCO2 =25)

AG = Na – (Cl+K) =22

Delta Gap = Change in AG/Change in HCO3 = 0.83

Expected PAO2 =(713xFIO2)-(PCO2X1.25) = 681

A-a gradient = PAO2- PaO2 =611 (Normal Age/4 +4 =11.5)

Description The ABG of this patient shows a metabolic acidaemia with adequate respiratory compensation. It is a high anion gap metabolic acidosis with no other metabolic disturbances as shown by a delta gap of 0.8.

There is a markedly elevated A-a gradient.

The patients sodium is on the higher end of normal and chloride is mildly elevated. The lactate is moderately elevated

Interpretation:In this clinical context the HAGMA is likely due to the lactic acidosis, which could be caused by underlying

-sepsis – due to skin lesions or pneumonia

-hypoxia –due to pneumonia, aspiration, non cardiopulmonary oedema (from heroin),PE

-toxins search and treat suspected OD

The saturation of the patient prior to intubation is not known, so one must consider complications related to the intubation causing low saturation and PaO2 – recall DOPES (dislodgement, obstruction, patient (pneumothorax, collapse, bronchospasm), equipment, stacked breathes)

The mildly raised chloride and upper normal sodium is likely secondary to dehydration.

Definition of septic shock and sepsis as per Sepsis 3

Sepsis – infection related acute increase of 2 or more points from baseline in the Sequential Organ Failure Assessment (SOFA) score

Septic Shock – infection associated with persistent hypotension (without specifying blood pressure thresholds) requiring vasopressors to maintain adequate tissue perfusion, along with a lactate of >2mmol/l

qSOFA (quick SOFA) uses the following criteria:

-Hypotension: SBP less than or equal to 100 mmHg

-Altered mental status (any GCS less than 15)

-Tachypnoea: RR greater than or equal to 22

Quick SOFA cannot be used outside of ICU as a predictive score.  Its predictive value has not been assessed in ED patients.  However it has been suggested that the quick SOFA score be used in ED as a screening test to identify patients with possible sepsis who are at higher risk of deterioration and therefore require more urgent care.



Macdonald, SPJ, Williams JM et al. Review Article: Sepsis in the Emergency Department – Part 1: Definitions and Outcomes. Emerg. Med. Australasia. 2017; 29; 6: 619-625