Investigating the Influence of Haemolysis on the Potassium Concentration After Capillary Blood Sampling

K@Home_1 a working package of the FFG project "K@Home - potassium home monitoring for patients with heart- and kidney insufficiency". In the project K@Home a potassium measuring system serveable by the patients even of the home monitoring should be developed.

Aim from K@Home is to allow an everyday home monitoring of the potassium value by the development of potassium-test stripe, like with the diabetes patients who supervise their blood sugar level by measurements with glucose-test stripe from a drop of capillary blood from the finger berry and with it the emergencies and hospital admissions to reduce or to prevent. It is fact that haemolysis has a strong influence on the measured potassium concentration. It is likely that by using capillary blood a haemolysis appears and therefore distorted potassium concentrations are measured.

In the study K@Home_1 it is a matter of evaluating, how high the degree of the haemolysis in capillary blood is, and in this fact to what extent leads to wrong potassium values. The results from this study will be a basic component for the sensor development.

After clarification the approval the Informed Consent is signed and the inclusion as well as exclusion criteria (incl. demography, concomitant medication and medical history) or vital parameters (blood pressure, pulse, size, weight), are raised. An urine-pregnancy test is also carried out for the exclusion of a pregnancy in women capable of bearing children. It is not necessary that the subjects seem sober on the study day.

With 22 healthy subjects capillary and venous blood is taken within the scope of one single study round. Blood is taken from the test persons by trained specialist staff of two fingertips of each hand (a total of four fingertips). The capillary blood sampling occurs in 200 µ l Lithium-Heparin Sarsted Microvettes and in each case the first drop of blood is rejected. To guarantee a light blood decrease without strong mechanical pressure, the hands are warmed up before the capillary sampling required with the help of an electric blanket or by warm water roughly on room temperature.