Blood gas, swan and cardiac arrest

Q; During cardiac arrest, which blood gas is more reliable?

A) Femoral artery (Arterial Blood Gas)
B) Pulmonary artery (Venous Blood Gas)


Answer:  B

During massive shock state arterial blood gas (ABG) does not accurately reflect the acid-base status as well as oxygenation at tissue levels. During such situation - given pulmonary artery catheter (PAC) is present - PH from PAC is the true indicator of the level of shock. In such scenarios, PH from ABG can be falsely high and can be very misleading. Unfortunately, PAC is not always present.

#hemodynanmic
#acid-base


References: 

1. Weil MH, Rackow EC, Trevino R, et al. Difference in acid-base state between venous and arterial blood during cardiopulmonary resuscitation. N Engl J Med 1986; 315:153. 

2. Adrogué HJ, Rashad MN, Gorin AB, et al. Assessing acid-base status in circulatory failure. Differences between arterial and central venous blood. N Engl J Med 1989; 320:1312.