[The use of the Siggaard-Andersen model of the oxyhemoglobin dissociation curve in patients in the immediate period following open heart surgery]. / Primenenie modeli krivoi dissotsiatsii oksigemoglobina Siggaard-Andersen u bol'nykh v blizhaishem periode posle operatsii na otkrytom serdtse.

A total of 300 patients have been examined on the first-third day after surgical correction of acquired heart valve defects, aortocoronary bypass surgery, and left ventricular postinfarction aneurysm resection performed using cardiopulmonary bypass technique. The parameters of the cardio-respiratory system and the value of parameter a in Siggaard-Andersen oxyhemoglobin dissociation curve (ODC) model have been studied. It has been shown that in some patients (about 5%) arterial blood hemoglobin saturation with O2 was lower than the corresponding blood pO2. In respiratory failure, parameter a decreases and the arterial part of ODC is shifted to the left, while in circulatory failure and hypoxia, parameter a of the venous blood increases and the curve is shifted to the right. The corresponding disorders corrected, the shifts are normalized. In severe postoperative complications and critical conditions additional (beside Bohr's effect and 2,3-diphosphoglycerate /2,3-DPG/ impact) ODC shifts, if any, are less marked. A statistically significant and considerable shift in parameter a of arterial ODC segment, as compared to venous one, has been observed. This ODC deviation from the model cannot be accounted for by pH, pCO2 or 2,3-DP impact. It can't be so far excluded that the effect observed might be partially due to regular errors of the measuring devices. However, it might turn out to be a new phenomenon of compensatory ODC shape changes in patients with acute cardiorespiratory disorders.

[Hemoglobin-oxygen affinity in acute respiratory and circulatory disorders in patients following open heart surgery]. / Srodstvo gemoglobina k kislorodu pri ostrykh narusheniiakh dykhaniia i krovoobrashcheniia u bol'nykh posle operatsii na otkrytom serdtse.

Hemodynamic parameters, lung gas exchange, hemoglobin, acid-base balance, gases, blood lactate and pO2 have been studied in 105 patients with acute cardiorespiratory disturbances (CRD) after open heart surgery. The actual P50 was determined by the venous point, using the Severinghaus blood gas analyser. The method of multidimensional regression analysis was used to study the contribution of some factors determining oxyhemoglobin dissociation curve (ODC) shift. It has been shown that CRD are characterized not only by Bohr's effect and temperature impact but also by ODC shifts, which cannot be accounted for by changes in erythrocyte 2,3-diphosphoglycerate concentration. As hypoxia is universal for any CRD the index of mixed venous blood saturation with O2 (Sv-O2) was considered as a factor determining hypoxic ODC shift and a numerical contribution of hypoxia to P50 changes has been determined. The coefficient in delta Sv-O2 was 0.0025-0.0030 15% Sv-O2 changes were in Bohr's effect equivalent to ODC shift, with pH changing by 0.1. The role of hypoxia in the changes of Hb-O2 affinity in CRD is discussed.

[The 2,3-diphosphoglycerate content and its influence on hemoglobin-oxygen affinity in patients following open heart surgery]. / Soderzhanie 2,3-difosfoglitserata i ego vliianie na srodstvo gemoglobina k kislorodu u bol'nykh posle operatsii na otkrytom serdtse.

70 patients have been examined in the early postoperative period after aortocoronary bypass surgery and surgical correction of acquired heart valve defects. 2,3-diphosphoglycerate (DPG) concentration was shown to increase in acute postoperative disturbances. The increase was most pronounced in reduced oxygen transport to tissues. However, with 2,3-DPG synthesis and metabolism slowed down, its concentration did not always correspond to the real state of the cardio-respiratory system. Changes in H+ concentration played a certain role in the regulation of 2,3-DPG content. In patients with cardio-respiratory disturbances 2,3-DPG concentration increased by 0.55 mcM/ml on average, with plasma pH increased by 0.1. No such regularity has been observed in patients with uncomplicated postoperative period. A positive correlation has been established between changes in 2,3-DPG concentration and the position of oxyhemoglobin dissociation curve. Considerable fluctuations in P50 value standard in cardiorespiratory disturbances have been observed. However 2,3-DPG effect was not the only mechanism causing these fluctuations.

[The Bohr effect during an uncomplicated course of the early postoperative period in heart surgery patients]. / Effekt Bora pri neoslozhnennom techenii rannego posleoperatsionnogo perioda u kardiokhirurgicheskikh bol'nykh.

48 patients have been examined in the early postoperative period after open heart surgery (25 patients after correction of acquired heart valve defects and 23 patients after aortocoronary bypass surgery on 2-6 coronary arteries). Gas exchange parameters, hemodynamics, hemoglobin, gases, acid-base balance were studied and P50 was determined with the Severinghaus blood gas analyzer. Using a multidimensional regression analysis, the regularities of P50 changes in uncomplicated postoperative period have been investigated (namely coefficients of temperature and Bohr's shifts of oxyhemoglobin dissociation curve have been studied). It has been shown that the main factors responsible for P50 changes in patients with uncomplicated postoperative period are Bohr's effect (i. e. the impact of pH and pCO2) and the body temperature. With pH and T changes, the coefficients were close to classical ones: -0.37, -0.42 and 0.035, respectively. In Bohr's effect the coefficient, as determined by multidimensional regression analysis, was not very reliable, which was due to its low value (about 0.001).

[Regulation of blood oxygen transport function in patients after open-heart surgery]. / Reguliatsiia kislorodtransportnoi funktsii krovi u bol'nykh posle operatsii na otkrytom serdtse.

The oxygen transport function of the blood was studied in 223 patients in the early postoperative period after open-heart surgery, which included correction of acquired cardiac valve defects and aortocoronary bypass. The studied parameters comprised central hemodynamics, pulmonary gas exchange, oxygen supply and utilization, acid-base status, blood gas and lactate content, as well as erythrocytic 2,3-diphosphoglycerate (DPG); Boehringer Mannheim reagents (FRG) were used. The venous blood P50 was calculated using a Severinghaus device. It was found, that the Bohr effect and temperature changes are the major factors controlling the Hb affinity to oxygen. No coefficient modifications in pH and T were detected. Patients with cardiac and pulmonary disorders showed, along with the Bohr effect and temperature influences, an additional shift of the oxyhemoglobin dissociation curve. A positive relationship was revealed between the 2,3-DPG level and standard P50 value. However, the coefficient was low (0.010) at 2,3-DPG and insufficiently stable. It is most probable, that 2,3-DPG mediates the buffer effect eliminating the drastic P50 deviations and is not completely responsible for additional ODC shifts in cardiopulmonary disorders. A quantitative relationship between hypoxia and Hb affinity to oxygen was revealed. The coefficient at SO2 Y varied from -0.0025 to -0.0030 by one percent of changes in the latter. Reduction in SO2 by 15 percent in cardiopulmonary patients was equivalent to the Bohr effect at a pH fall by 0.1 unit.