pH of blood dependent on:
cause of arrest
duration of arrest when ABG is taken
the quality of the CPR and ventilation the patient is receiving
temperature of the patient when ABG taken
drugs administered during arrest (ie. Adrenaline and NaHCO3)
Elevated pCO2
often due to inadequate ventilation during resuscitation
Low PaO2
insufficient oxygenation during resuscitation
aspiration
pulmonary edema
PE
primary respiratory pathology
Hyperkalemia Causes
cell death
loss of cell membrane integrity and acidosis
other sources such as missed dialysis
Arterial blood gas analysis
Venous blood gas
Cardiac ultrasound
ECG 
Pulmonary artery catheter
Age adjusted D-dimer
Initial mechanical ventilation settings 
Initial mechanical ventilation settings