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Abstract
A procedure for the preparation of a Stroma-Free Hemoglobin Solution (SFHS) is given. The stability of this SFHS containing Methemoglobin Reductase, can be improved by addition of NADH. The characteristics of the stable SFHS can be manipulated by varying independently the concentrations of bicarbonate and Inositol-Hexa-Phosphate. This way the desired acid-base behaviour and position of the Oxygen Hemoglobin Equilibrium Curve (OHEC) can be obtained.
Three SFHS were prepared with acidotic, alkalotic or normal acid-base characteristics and all SFHS had an OHEC in the normal position (actual p50 3.33–3.87 kPa). Results show that:
- stability of SFHS is 1 year, xHi <2.5% after 1 year.
- p50 decreases about 15% per year.
- Hill's coefficient, nHill, is constant, but differed between levels; the mean values for nHill are 2.0 for the acidotic level, 2.2 for the normal and 2.4 for the alkalotic level.
- temperature coefficients for SFHS are:
d(pH)/dt =-0.016 pH/°C, d(pCO2)/dr = 6.2%/°C and d(pO2)/dt = 7.2%/°C.
Oxygen and carbon dioxide tonometered SFHS, of which the pH was measured with the reference method for pH measurement in blood was used on several blood gas analyzers to demonstrate the suitability for pH, pCO2 and pO2 measurement. The SFHS, which contained oxyhemoglobin, carboxyhemoglobin and methemoglobin, was also used as a control material for hemoglobin meters and CO-Oximeters.
It is concluded that SFHS behaves blood-like with respect to pH, pC2 and pO2 as well as total hemoglobin, oxygen saturation, carboxyhemoglobin and methemoglobin measurements. In contrast to hemoglobin-free aqueous control material, it buffers oxygen in a blood-like manner. Its shelflife is limited compared to the generally used aqueous control materials, but it is sufficient for repetitive use in clinical laboratories.