Clinical Details
A 63 year old man presented to a private hospital with significant pain in his right side. A CT scan confirmed the clinical assessment of a leaking abdominal aneurysm. Previous health was good. Initial pathology results included Hb 142 g/l, Na⁺ 137, K⁺ 3.8 Cl^- 103, bicarbonate 23, urea 5.1 and creatinine 0.10 mmol/l. He was transferred to a public hospital for surgery. Arterial blood gases were collected midway through the procedure (with FIO2 1.0 & end-tidal pCO2 37mmHg):

Assessment
 The patient’s previous health was good so all the acid base changes would be expected to be acute. Consideration of the clinical circumstances strongly support a metabolic acidosis (due to lactic acidosis related to poor perfusion) and a respiratory acidosis (due to inadequate alveolar ventilation).

Immediate management is to significantly increase the minute ventilation to decrease the arterial pCO2. This will result in a rapid improvement in the acidaemia and also and more significantly improve the intracellular acid-base state towards normal.

Firstly, initial clinical assessment (on the first gas results):

To be completed in the future when I update these remaining Cases to the new format.

Secondly, the acid-base diagnosis: 
1. pH: A significant acidaemia indicates that an acidosis is present
2. Pattern: The pattern of an elevated pCO2 and              bicarbonate level means a mixed acidosis must be present.
3. Clues:  
4. Compensation:  
5. Formulation:  
6. Confirmation: 
 

Finally, the Clinical Diagnosis:

 Diagnosis