CIRCUMPOLAR HYPOXIA: A REVIEW PAPER

An increasing number of authors devote their work to the study of circumpolar hypoxia. Conclusions about the mechanisms of its occurrence based on the results of the work are ambiguous. Some researchers believe that hypoxia in the North is due to oxygen defi ciency and rarefi ed air. Others believe that hypoxia in the North is not associated with a decrease in the partial pressure of oxygen in the air, since it diff ers little from other regions, except for the highlands. Also, a number of authors are of the opinion that circumpolar hypoxia is associated with increased tissue oxygen consumption. It is believed that the main cause of hypoxemia in the North is a violation of the diff usion of oxygen and carbon dioxide through the alveolar-capillary membrane of the lungs. It has been established that the genesis of circumpolar hypoxia is of a mixed nature and is a systemic phenomenon, which must be taken into account when developing measures to accelerate adaptation for living in the North.

Correlation of Venous Oxygen Saturations from Noninvasive Hematocrit Monitoring Using Blood Gas Measured Oximetry in Chronic Pediatric Hemodialysis Patients

<b><i>Introduction:</i></b> Noninvasive hematocrit monitoring (NIVHM) during pediatric hemodialysis (pedHD) provides data in real time regarding changes in hematocrit and blood volume and also provides venous oxygen saturations. The latter has been proposed to indicate changes in tissue oxygen consumption. It is not known how well NIVHM oxygen saturations (O2sat) approximate blood gas measured oximetry saturation (mO2sat) in the course of pedHD. We aimed to assess the validity and reliability of NIVHM O2sat compared to mO2sat. <b><i>Methods:</i></b> This is a prospective study in 15 patients &#x3c;21 years old with &#x3e;90 days on hemodialysis (HD) without congenital heart disease. HD access was fistula (AVF) in 4 patients and tunneled catheters in the remainder. Pulse oximetry (spO2) was continuously monitored; mO2sat was measured via oximetry in a blood gas analyzer and NIVHM O2sat values collected at the start, middle, and end of HD treatment. <b><i>Results:</i></b> A total of 45 dyad measurements were obtained. NIVHM O2sat correlated well with mO2sat (<i>R</i> = 0.89, <i>p</i> &#x3c; 0.0001); the same was seen at pre, mid, and post HD time points (<i>R</i> = 0.86–0.95, <i>p</i> &#x3c; 0.001). NIVHM O2sat was lower than mO2sat; with catheter as access, the difference was 9.3 ± 8.6 (CI: 12.3–6.22, <i>p</i> &#x3c; 0.0001) and with AVF was 2.1 ± 0.78 (CI: 2.6–1.7, <i>p</i> &#x3c; 0.0001). Bland-Altman analysis demonstrated the difference but did not show any systematic bias. Continuous monitor of spO2 showed no hypoxia. <b><i>Discussion/Conclusion:</i></b> Intradialytic NIVHM O2sat correlates well with mO2sat but yield lower values. Future studies can include NIVHM O2sat changes as a surrogate for central venous O2 saturation changes and potentially yield useful information regarding tissue oxygen consumption in pedHD patients.

PREOPERATIVE CORRECTION OF SYMPTOMS OF ENDOGENOUS INTOXICATION AND VIOLATIONS OF THE OXYGEN STATUS IN PATIENTS WITH COLORECTAL CANCER

The purpose of the study is to propose a method of preoperative correction of the symptoms of endogenous intoxication syndrome and associated respiratory disorders in patients with colorectal cancer. The study involved 68 patients having a surgery for colorectal cancer of different localization, with an increased leukocyte index of intoxication by V.K.Ostrovsky in preoperative period. The first group patients (37 subjects) in the preoperative preparation program took Cytoflavin® according to the developed scheme. The second group patients (31 subjects) had a standard preoperative preparation. As result of the research, there was revealed a positive effect of the proposed method of preoperative preparation on hematological parameters of endogenous intoxication (decrease in values of the parameters of Calf-Caliph, Ostrovsky and integral index of intoxication) and parameters of oxygen status, which changes indicated a decrease in tissue hypoxia (decrease in tissue oxygen consumption). The positive effect of the proposed method of preoperative preparation was observed in the postoperative period (reduced severity of respiratory disorders and hematological symptoms of endogenous intoxication).

Microcirculation and Macrocirculation in Cardiac Surgical Patients

Background. The aim of our study was to investigate the relationship between microcirculatory alterations after open cardiac surgery, macrohemodynamics, and global indices of organ perfusion.Methods. Patients' microcirculation was assessed with near-infrared spectroscopy (NIRS) and the vascular occlusion technique (VOT).Results. 23 patients undergoing open cardiac surgery (11 male/12 female, median age 68 (range 28–82) years, EuroSCORE 6 (1–12)) were enrolled in the study. For pooled data, CI correlated with the tissue oxygen consumption rate as well as the reperfusion rate (, and , , resp.). In addition, both total oxygen delivery (DO2, mL/min per m2) and total oxygen consumption (VO2, mL/min per m2) also correlated with the tissue oxygen consumption rate and the reperfusion rate. The tissue oxygen saturation of the thenar postoperatively correlated with the peak lactate levels during the six hour monitoring period (, ). The tissue oxygen consumption rate (%/min) and the reperfusion rate (%/min), as derived from the VOT, were higher in survivors compared to nonsurvivors for pooled data [23 (4–54) versus 20 (8–38) ] and [424 (27–1215) versus 197 (57–632) ], respectively.Conclusion. Microcirculatory alterations after open cardiac surgery are related to macrohemodynamics and global indices of organ perfusion.

AN IMPROVED MODEL FOR THE DIFFUSION OF OXYGEN INTO RESPIRING WOOD

Diffusion is an essential component of gas exchange at the cellular and tissue level, and a mathematical analysis of diffusion is therefore important to model biological processes in many systems. When several factors affect diffusion, finding an explicit non-steady-state equation can be difficult or impossible. In an earlier work (J Biol Systems15:63–72), we described such a function for a system where oxygen diffuses from the air into a body that consumes oxygen, assuming that the exchange surface is flat. Here, an explicit solution is limited to the case where tissue oxygen consumption decreases linearly with oxygen concentration and reaches 0 only when all oxygen has been consumed. The objective of this article is the analysis of gas diffusion into a respiring tissue that is cylindrical, which applies to tree stems and is a more realistic approximation for many other organs. This approach differs from diffusion along a flat surface, resulting in formally completely different explicit solutions, and is more flexible allowing for different relationships between oxygen concentration and tissue oxygen consumption.