Tuesday May 16, 2006
Potassium level via A-line
Potassium level via arterial line may not be as reliable as through peripheral venous punture. See this interesting case report (click reference) published in British Journal of Anaesthesia, where radial arterial line consistently showed K level of 7.4 - 9.3 mEq/L without any clinical signs. Simultaneous venous sample level was 4.4 mEq/L. When cannula was slightly withdrawn, arterial potassium level came back as 4.1 mEq/L (c/w venous sample).
It was postulated that the tip of the cannula could have impinged against the vessel wall so that during withdrawal of the sample a high shear rate could have caused haemolysis of red blood cells leading to an increased potassium concentration in the blood samples.
References: click to get abstract/article
1. Apparent hyperkalaemia from blood sampled from an arterial cannula - British Journal of Anaesthesia 2004 93(3):456-458