EFFECT OF INORGANIC-IONS ON THE OXYHEMOGLOBIN DISSOCIATION CURVE OF SEVERELY ILL PATIENTS

We have shown that the administration of inorganic potassium phosphate s (Pi) to patients with severe diabetic ketoacidosis was able to incre ase the P-50 (the PO2 necessary to achieve a hemoglobin saturation of 50%) by a non diphosphoglycerate (DPG) mediated effect [12]. This sugg ests that the oxyhemoglobin dissociation curve (ODC) may be determined not only by pH, temperature, CO2 content and DPG but also by plasmati c ions. In order to test this hypothesis we have determined the ODC on whole blood in two groups of subjects, 49 control subjects with match ing age and sex and 49 patients suffering from liver cirrhosis, acute pancreatitis, septic shock and acute respiratory distress syndrome. Th e patients had many ionic disorders induced either by their diseases o r by the applied treatment. The mean ODC of the patients did not diffe r from the normal values, In contrast. the dispersion of PO2 around th e saturations values was increased from 5 to 80% saturation. A forward regression analysis showed that the DPG level and the levels of inorg anic phosphates and natrium (Na+) played a significant role in determi ning the position of the ODC according to the following equation: P-50 (mmHg) = 34.5 + 0.225 DPG + 0.62 Pi 0.09 Na+, where DPG is in micromo l.gHb(-1) and Pi and Na+ in mEq.(l-1). In separate experiments we show ed that the Bohr effect as expressed in d (log PO2)/dpH amounted to -0 .53, -0.46 and -0.42 for SO2 equal to 5%, 50% and 95%, respectively. T he corresponding values for the temperature effect was expressed in d (log PO2)/dT amounted to 0.028, 0.024, and 0.020 respectively. The fac t that ions play an role in regulating the position of the ODC of pati ents with ionic disorders may have therapeutical implications, prevent ive or curative.