Arterial Blood Oxygen Content Research Articles

STATE OF HAEMODYNAMICS AND OXYGEN BUDGET IN THE PERIOPERATIVE PERIOD IN PATIENTS WITH OSTEOARTHRITIS AND CONCOMITANT CARDIAC PATHOLOGY DURING TOTAL HIP ARTHROPLASTY SURGERY DEPENDING ON THE TYPE OF SURGICAL ACCESS

Summary. Aim. To compare the hemodynamic status and oxygen budget in patients with osteoarthritis and comorbid cardiac pathology during total hip arthroplasty, based on the type of surgical approach used. Materials and Methods. The study analyzed the treatment outcomes of 90 patients with stage 3-4 osteoarthritis of the hip who underwent total cemented hip arthroplasty. All patients were divided into two groups according to the surgical approach (traditional posterior or modified posterior). The study was conducted at the following stages: before surgery, immediately after surgery, 24 hours post-surgery, and one week after surgery. The following parameters were recorded: hemodynamic parameters (heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and central venous pressure) and oxygen budget parameters (hemoglobin (Hb), lactate, hematocrit (Ht), oxygen saturation of hemoglobin in arterial and venous blood (SaO2 and SvO2), partial pressure of oxygen in arterial and venous blood (paO2 and pvO2)). Based on these data, the following indices were calculated: left ventricular ejection fraction (LVEF), cardiac index (CI); oxygen content in arterial and venous blood (CaO2 and CvO2), arteriovenous oxygen content difference (C(a-v)O2), oxygen transport (TO2), oxygen consumption (VO2); systemic perfusion pressure (SPP), blood flow power (BFP), oxygen reserve (OR), and circulatory reserve (CR). Results. The use of the modified posterior approach positively influenced hemodynamic parameters. After the surgery and on the 7th day post-surgery, SPP was significantly lower with the modified posterior approach. The CI was also significantly affected by the modified posterior approach. Throughout the study, except for the first stage, CI was significantly higher when using the modified posterior approach. LVEF increased significantly with both approaches, but on the 7th day post-surgery, it was significantly higher in the second group. BFP did not statistically differ between the two groups throughout the study, but its energy efficiency was lower, primarily due to the arteriovenous oxygen content difference (C(a-v)O2). C(a-v)O2 was the same before surgery for both approaches. At subsequent stages of the study, the differences between the groups increased, and on the 7th day, they were the most significant, with C(a-v)O2 being lower after using the modified posterior approach. The energy efficiency of blood flow was assessed by calculating OR and CR. Both indicators were significantly higher during the study, except at the preoperative stage, when using the modified posterior approach. Conclusions. Our study clearly demonstrates the benefits of implementing the modified posterior approach in total hip arthroplasty for patients with osteoarthritis and comorbid cardiac pathology. This approach improves hemodynamic and oxygen budget parameters compared to the traditional approach, which can significantly impact treatment outcomes for patients with cardiac comorbidity and reduce the number of postoperative complications.

Overdot and overline annotation must be understood to accurately interpret O2MAX physiology with the Fick formula.

Few formulas have been used in exercise physiology as extensively as the Fick formula, which calculates the rate of oxygen consumption (i.e., V.O2) as the product of cardiac output (Q.) and the difference in oxygen content in arterial and mixed venous blood (ΔaO2). Unfortunately, the physiology of maximum V.O2 (V.O2MAX) is often misinterpreted due to a lack of appreciation for the limitations represented by the oft-ignored superscript annotations in the Fick formula. The purpose of this perspective is to explain the meaning of the superscript annotations and highlight how such annotations influence proper interpretation of V.O2MAX physiology with the Fick formula. First, we explain the significance of the overdots above V.O2 and Q., which indicate a measure per unit of time. As we will show, the presence of an overdot above Q. and lack of one above ΔaO2 denotes they are different types of ratios and should be interpreted in the context of one another-not in contrast to each other as is commonplace. Second, we discuss the significance of the overline above the "" in ΔaO2, which indicates the venous sample is an average of blood that comes from mixed sources. The mixed nature of the venous sample has major implications for interpreting the influence of oxygen diffusion and blood flow heterogeneity on V.O2MAX. Ultimately, we give recommendations and insights for using the Fick formula to calculate V.O2 and interpret V.O2MAX physiology.

IMPACT OF PARAVERTEBRAL BLOCKADE ON THE COURSE OF EARLY POSTOPERATIVE PERIOD FOLLOWING SURGICAL INTERVENTION FOR LUNG MALIGNANCIES UNDER INHALED SEVOFLURANE ANESTHESIA

The aim of the study is to investigate the impact of paravertebral blockade on the quality of anti-stress protection of general inhalation anaesthesia based on sevoflurane during operations in patients with lung malignancy. Material and methods. We examined 60 individuals of an average age 55±5.6 years, whose physical status was assessed as class II – III according to the ASA classification. The patients underwent open surgical procedures, including frontal or pneumonectomy, or partial lung resection. The patients were divided into 2 groups depending on the method of anaesthesia: SF group (sevoflurane) (n = 29) received inhaled anaesthesia with sevoflurane; SF+PVB group (n = 31) received the combination of inhaled anaesthesia with PVB. The following indicators were assessed: time of the first administration of the analgesic after surgery, pain intensity by the visual analogue scale (VAS), perfusion systemic pressure (PST), cardiac index (CI), oxygen content in arterial and venous blood, blood lactate levels, indicators of circulatory energy efficiency, cortisol, insulin and HOMA index levels. Indicators were recorded before the surgical operation, at the wake-up stage, on the 1st and 5th days following the operation. Results. In the SF+PVB group, the intensity of pain in the postoperative period was significantly lower than in the SF group. In the SF+PVB group, there was no necessity for administering narcotic analgesics on the first day, while in the SF group, the dose of morphine was 0.27±0.04 mg/kg∙day, the first administration was performed 65.5±10.3 minutes after surgery. CI during surgery and in a day was significantly higher in the SF+PVB group, and the arteriovenous difference in oxygen content was significantly lower. The energy efficiency of blood circulation at the same stages was significantly higher in the SF+PVB group. In the same group, there was a significantly lower concentration of markers of stress responses (cortisol levels and HOMA index). Conclusions. The use of paravertebral blockade under the general anaesthesia based on sevoflurane during operations in patients with lung malignancies contributes to a significant reduction in the pain intensity in the postoperative period; eliminates the need to use narcotic analgesics; provides significantly more stable hemodynamics and significantly more adequate oxygen supply during the operation and in the postoperative period; significantly reduces the intensity of stress reactions as well as significantly improves the energy efficiency of blood circulation.

Association Between Blood Donation and Improved Sleep Quality Among Blood Donors in Aseer Region

Background: High altitude like Aseer region has many challenges, where exposure to hypoxia is the most reported challenge. The ambient hypoxia activates a number of physiologic consequences including hyperventilation, increased resting heart rate and stimulation of erythrocyte production with the goal of preserving the oxygen content of arterial blood at or above sea level values. Aim: The current study aims to assess the association between blood donation and improved sleep quality among blood donors in Aseer Region, southern of Saudi Arabia. Methods: A cross-sectional study was carried out using self-administered questionnaire during the period from May to August 2022 targeting all Saudi population aged 18 years or more living in Aseer region. The study questionnaire was uploaded online using social media platforms by the researchers and their colleagues till no more answers were obtained. The study questionnaire included participants’ personal data, medical history, blood donation data including frequency, causes and associated symptoms. Sleep quality was assessed using Pittsburgh Sleep Quality Index (PSQI). Results: A total of 447 participants fulfilling the inclusion criteria completed the study questionnaire. Participants ages ranged from 18 to 60 years with mean age of 26.9 ± 12.7 years old. A total of 215 (48.1%) participants reported donating blood which was only once among 68 (31.6%), and 2-3 times among 82 (38.1%). Regarding overall sleep quality among blood donors in Aseer region, Saudi Arabia, exactly 116 (54%) of the study participants with blood donation history were poor sleepers while 99 (46%) were good sleepers. Better sleep quality was significantly associated with more frequent blood donation times. Conclusion: In conclusion, the current study showed that sleep quality among Aseer residents after blood donation was much lower than reported incidence especially among participants who donated blood more than once. Also, the attitude toward blood donation was good where nearly 1 out of each 2 participants donated blood for moral issues. Key words Blood donation, sleep hygiene, relation, Aseer region, high altitude

The effectiveness of hypo-hyperoxic training in the medical rehabilitation of patients who have undergone COVID-19

BACKGROUND: Interval hypo-hyperoxic training is a new promising technology in medical rehabilitation, including the rehabilitation of patients with post-COVID syndrome. However, the mechanisms of therapeutic action of interval hypo-hyperoxic training in the recovery period after suffering COVID-19 have not been fully studied. The effectiveness of interval hypo-hyperoxic training largely depends on the method of interval hypo-hyperoxic training.
 AIM: to develop modes and study the effectiveness of the use of interval hypoxic training in patients with post-COVID syndrome.
 MATERIALS AND METHODS: The performed open randomized comparative study involved patients with a diagnosis of post-COVID syndrome ― "Condition after COVID-19" according to the ICD (code U09.9). Patients of the main group, against the background of a course of traditional rehabilitation treatment, received interval hypo-hyperoxic therapy from the OXYTERRA device. In the comparison group, patients received only a traditional course of rehabilitation treatment. The study was conducted for 4 months. To assess the effectiveness of interval hypo-hyperoxic training before and after the course of rehabilitation, we studied the dynamics of the parameters of the circulatory system and the function of external respiration.
 RESULTS: 50 patients (19 women, 31 men, mean age 61.77.7 years) were randomly divided into the main group (n=30) and the comparison group (n=20). All patients completed a full course of rehabilitation. It was established that the course of training with interval hypo-hyperoxic training contributed to an increase in the oxygen capacity of the blood, an increase in the oxygen content in arterial blood, a decrease in heart rate, normalization of the level of systolic and diastolic pressure, restoration of stroke and minute blood volume parameters in patients of the main group. Interval hypo-hyperoxic training caused an improvement in the functional state of the bronchopulmonary system (p 0.049). There was an improvement in the activity of the central ergotropic and humoral-metabolic mechanisms of heart rhythm regulation, correction of the activity of the sympathetic link of regulation and the modulating effect of the parasympathetic division on the heart rhythm, normalization of the vagosympathetic balance coefficient.
 CONCLUSION: The use of interval hypo-hyperoxic training in the recovery period in patients with post-COVID syndrome according to the developed method caused a stable improvement in the clinical condition, which lasted from 3 to 6 months after the completion of complex rehabilitation.

Diagnostic value of right heart and pulmonary artery catheterization in patients with suspected pulmonary hypertension. Part 2. Invasive study of parameters of hemodynamics and oxygen transport

The aim – evaluate the parameters of pulmonary and systemic hemodynamics obtained in patients with various forms of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) in Ukraine.Materials and methods. The study included 195 patients: IPAH was in 68 patients; PAH associated with connective tissue diseases (CTD) – in 21 patients; PAH associated with HIV infection – in 4 patients; PAH associated with portal hypertension (PH) – in 4 patients; PAH associated with congenital heart disease – in 25 patients; CTEPH – in 51 patients, pulmonary hypertension (PH) associated with left heart disease (LHC) – in 5 patients and 17 patients who were excluded from the diagnosis of PH. From 2014 to 2019, these patients underwent 220 procedures of right heart catheterization (RHC) in accordance with current European Guidelines. Also, all patients underwent echocardiographic examination and determined the gas composition of blood and indicators of acid-base balance using the ABL 735 analyzer, calculated the parameters of the affinity of hemoglobin to oxygen (p50).Results and discussion. The lowest level of arterial blood oxygen saturation was in the group of patients with PH due to LHD – 88.9 % (p<0.05); in other groups it averaged 94–97 %. The oxygen content in arterial blood was the lowest in the group of patients with PH due to LHD – 15.7 ml/L (p<0.05); in other groups this indicator was equal to 17.4–18.7 ml/L. The lowest oxygen saturation of mixed venous blood (SvO2) was in the PAH group associated with HIV – 58 % (p<0.05), and close to critical (< 65 %) SvO2 level was observed in the IPAH group – 66.3 %. CTEPH – 66.0 %. The highest level of this indicator was in the PAH group associated with portal hypertension – 81.1 %. The arterio-venous difference was highest in the PAH associated with HIV group – 5.6 ml/L, and the smallest in the PAH associated with PH group – 2 ml/L. On the other hand, the oxyhemoglobin dissociation curve was almost normal in all groups, except for the group of patients with PAH associated with portal hypertension.Conclusions. The most severe disorders of hemodynamics and oxygen transport were observed in the group of PAH patients associated with HIV compared with other forms of PAH and CTEPH. The IPAH and CTEPH groups were similar in terms of hemodynamics, despite a different pathophysiological mechanism. In the group of patients with PAH associated with CTD, the results of the RHC were slightly better than in the group of patients with IPAH, reflecting that the hemodynamic component is not the leading one for prognosis in these patients. Also, the performance of the right ventricle was significantly higher in patients with PAH compared with the group without PH.

Birth is Associated with Reduced Coronary Capacity in Sheep

The transition from fetal to neonatal life is among the most universal and rapid changes in physiology encountered in mammalian life. In this study, we sought to directly characterize the effects of birth on the function and capacity of the coronary vasculature in a large animal model of cardiac development. We hypothesized that significant increases in coronary reserve and oxygen delivery would accompany the increased demands placed on the myocardium by the challenges of postnatal life, including dramatic increases in pulmonary blood flow, left ventricular preload, and cardiac output. Near term fetuses (N = 7), and term-born lambs (N = 5) of mixed western breed ewes were instrumented with catheters (aortic arch, right atrium, left atrium), inflatable occluders (inferior vena cava, postductal thoracic aorta), and a Transonic flow probe (left circumflex coronary artery). Studies (unanesthetized) were carried out at least 3 days later (135-136 days gestation (term = 147 days)) or 5-6 d postnatal. Pressure-flow relationships were determined at rest or at maximal adenosine-induced hyperemia. The mass of myocardium served by the artery from which flow was measured was determined by postmortem Evan's Blue perfusion; all reported flow values are normalized to this mass. Cardiac work is the double product of driving (aortic minus right atrial) pressure. We define coronary conductance as the slope of the pressure-flow relationships, and coronary flow reserve as the fold change in coronary flow between resting and hyperemic conductance. Differences between fetuses and neonates were assessed by the Mann-Whitney U-test and considered significant when p < 0.05. Basal cardiac work was significantly greater after birth, as heart rate and driving pressure were 1.3 and 1.6-fold greater in neonate than fetus (p = 0.009, p = 0.003, respectively). Resting coronary flow was 1.8-fold lower in the neonate than the fetus (p = 0.048). Despite a 1.6-fold increase in arterial blood oxygen content (p = 0.006), baseline oxygen delivery per work in the neonate was less than half that in the fetus (p = 0.005; Figure 1A). Pressure-flow relationships (Figure 1B) likewise showed a reduction in coronary conductance from fetus to neonate both at rest (2.3-fold, p = 0.073) and with adenosine hyperemia (2-fold, p = 0.048). Estimated hyperemic coronary flow at resting daily pressures were decreased by 1.6-fold in the neonate (p = 0.03). Coronary flow reserve was similar between fetuses and lambs (p = 1; Figure 1C). Despite the increased cardiac demands of postnatal life, these results suggest that there is not an increase in coronary reserve or capacity following birth. Rather, we find evidence of lower resting and maximal coronary flow in the postnatal period such that flow reserve is maintained. This evidence of an actively regulated decrease in coronary capacity shows the functional consequence of a known reduction in capillary to fiber ratio occurring in the myocardium between birth and maturity. Future studies of myocardial perfusion focusing on microvascular structure and function are therefore warranted.

Renal microvascular oxygen tension during hyperoxia and acute hemodilution assessed by phosphorescence quenching and excitation with blue and red light.

The kidney plays a central physiologic role as an oxygen sensor. Nevertheless, the direct mechanism by which this occurs is incompletely understood. We measured renal microvascular partial pressure of oxygen (PkO2) to determine the impact of clinically relevant conditions that acutely change PkO2 including hyperoxia and hemodilution. We utilized two-wavelength excitation (red and blue spectrum) of the intravascular phosphorescent oxygen sensitive probe Oxyphor PdG4 to measure renal tissue PO2 in anesthetized rats (2% isoflurane, n = 6) under two conditions of altered arterial blood oxygen content (CaO2): 1) hyperoxia (fractional inspired oxygen 21%, 30%, and 50%) and 2) acute hemodilutional anemia (baseline, 25% and 50% acute hemodilution). The mean arterial blood pressure (MAP), rectal temperature, arterial blood gases (ABGs), and chemistry (radiometer) were measured under each condition. Blue and red light enabled measurement of PkO2 in the superficial renal cortex and deeper cortical and medullary tissue, respectively. PkO2 was higher in the superficial renal cortex (~ 60 mmHg, blue light) relative to the deeper renal cortex and outer medulla (~ 45 mmHg, red light). Hyperoxia resulted in a proportional increase in PkO2 values while hemodilution decreased microvascular PkO2 in a linear manner in both superficial and deeper regions of the kidney. In both cases (blue and red light), PkO2 correlated with CaO2 but not with MAP. The observed linear relationship between CaO2 and PkO2 shows the biological function of the kidney as a quantitative sensor of anemic hypoxia and hyperoxia. A better understanding of the impact of changes in PkO2 may inform clinical practices to improve renal oxygen delivery and prevent acute kidney injury.

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation.

Adequate oxygen delivery to a tissue depends on sufficient oxygen content in arterial blood and blood flow to the tissue. Oximetry is a technique for the assessment of blood oxygenation by measurements of light transmission through the blood, which is based on the different absorption spectra of oxygenated and deoxygenated hemoglobin. Oxygen saturation in arterial blood provides information on the adequacy of respiration and is routinely measured in clinical settings, utilizing pulse oximetry. Oxygen saturation, in venous blood (SvO2) and in the entire blood in a tissue (StO2), is related to the blood supply to the tissue, and several oximetric techniques have been developed for their assessment. SvO2 can be measured non-invasively in the fingers, making use of modified pulse oximetry, and in the retina, using the modified Beer–Lambert Law. StO2 is measured in peripheral muscle and cerebral tissue by means of various modes of near infrared spectroscopy (NIRS), utilizing the relative transparency of infrared light in muscle and cerebral tissue. The primary problem of oximetry is the discrimination between absorption by hemoglobin and scattering by tissue elements in the attenuation measurement, and the various techniques developed for isolating the absorption effect are presented in the current review, with their limitations.

Relationships between Physiologic and Neuropsychologic Functioning after Fontan

To investigate potential relationships between neuropsychologic functioning and cardiac, gastroenterologic/hepatologic, and pulmonary complications in the single ventricle heart disease (SVHD) post-Fontan population. Following the initiation of a Fontan Multidisciplinary Clinic, patients with SVHD were evaluated systematically according to a clinical care pathway, and data from multiple subspecialty evaluations were collected prospectively from 2016 to 2019. Biomarkers of cardiology, pulmonary, and hepatology/gastroenterology functioning were abstracted, along with neuropsychologic testing results. Bivariate correlations and regression analyses examined cross-sectional relationships between physiologic predictors and neuropsychologic outcomes. The sample included a cohort of 68 youth with SVHD age 3-19years, after Fontan palliation. Sleep-disordered breathing was related to poorer visual-motor integration skills (r=-0.33; P<.05) and marginally related to poorer executive functioning (r=-0.33; P=.05). Lower arterial blood oxygen content was related to poorer executive functioning (r=.45; P<.05). Greater atrioventricular valve regurgitation was related to lower parent-rated adaptive functioning (ρ=-0.34; P<.01). These results were maintained in regression analyses controlling for history of stroke and/or seizures. We demonstrated associations between neuropsychologic functioning and potentially modifiable aspects of physiologic functioning in a prospectively evaluated cohort of patients with SVHD with Fontan physiology. Our findings emphasize the importance of multidisciplinary screening and care after a Fontan procedure and suggest avenues for intervention that may improve patient outcomes and quality of life.

Perinatal exposure to ethanol in rats induces permanent disturbances of breathing and chemosensitivity during adulthood

Perinatal exposure to drugs of abuse, including alcohol (ethanol), is known to impinge the development of respiratory function. However, most studies described the short-term effects of these exposures, focusing mostly on the early postnatal life. After exposure to ethanol during gestation and lactation we have previously shown that 3–4 week-old rat exhibit chronic hypoventilation and an altered response to hypoxia at the end of ethanol exposure. However, whether these deficits are reversible following ethanol withdrawal remained unknown. Here, we investigated through whole-body plethysmography the respiratory activity of 2 months-old rats exposed to ethanol from gestation to weaning followed by one month of ethanol withdrawal. After ethanol withdrawal, rats persistently exhibited a significant reduction in respiratory frequency without change in tidal volume associated to a lower arterial blood oxygen content. In addition, the response to hypoxia in these rats was reduced whereas the response to hypercapnia remained unaltered. In conclusion perinatal exposure to ethanol in rats, unlike exposure to cocaine, morphine or nicotine, is characterized by selective alterations of basal respiratory activity and chemosensitivity that persist long after withdrawal.

Effect of Perioperative Optimization of Arterial Oxygen Content and Perfusion Pressure on the Function of the Transplanted Kidney in the Retrospective Study of Excretory Function and Assessment of New Markers of Kidney Damage: IL-18, Neutrophil Gelatinase-Associated Lipocalin, and Clusterin

IntroductionThe concept of anesthesia, in which kidney perfusion is optimized, the use of nephrotoxic drugs is avoided, and general anesthesia with protective and preconditioning properties of the graft is applied, is a key element of the therapeutic strategy in kidney transplantation (KTx). Material and methodA total of 86 patients (mean age: 49.4 ± 14.0 years, 66% men) with end-stage renal disease who underwent KTx between 2012 and 2015 were included in this retrospective study. Our aim was to assess the effect of oxygen content in arterial blood and selected hemodynamic parameters on the graft function and the occurrence of delayed graft failure. ResultsNo differences were found in baseline characteristics, indication for transplantation, and surgical technique used among study population. No correlation was found between oxygen delivery exponents and both standard markers of renal function and new biochemical markers (eg, IL-18, clusterin, and neutrophil gelatinase-associated lipocalin [NGAL]). DiscussionIn our study, hemodynamic parameters measured at scheduled intervals did not exceed the physiological range, which might have been the reason for the lack of correlation between the function of graft and the described hemodynamic conditions. At the same time, in the observed ranges of perfusion pressure during optimization of the oxygen content, no correlations were found with the postoperative function of the transplanted kidney. That observation could be a valuable conclusion for reducing the tendency of maintaining high blood pressure with the abuse of catecholamines, especially vasoconstrictors, and volume therapy, whose negative effect on tissue perfusion is unequivocal.

Energy of blood circulation during blood loss

The state of circulatory energy in blood loss has been studied in 44 patients with spleen injury. Kinetic (final diastolic and systolic volumes of the left ventricle, heart rate), dynamic (effective arterial and central venous pressure, total peripheral resistance), hemic (oxygen content in arterial and venous blood) parameters of blood circulation, as well as the level of lactate reflecting the degree of hypoxia were studied. The energy indicators of blood circulation were determined: the power consumed by tissues, the oxygen reserve (reflecting the correspondence of the oxygen consumed by tissues to their needs) and the integral energy indicator - circulatory reserve. It has been determined that with an increase in blood loss, the energy indicators of blood circulation decrease: the power consumed by tissues decrease to (48.0±6.1); (41.1±8.7) and (23.5±9.3) mW/m2, the oxygen reserve decrease to (0.43±0.04); (0.37±0.05) and(0.27+0.07), the circulatory reserve decrease to (229+93); (180±41) and (47±25) mW/m2 respectively at blood loss 20 %, 30 % and 40 % of blood volume. Apparently 20 % blood loss is the maximum amount of blood loss in relation to compensatory possibilities of autoregulation of blood circulation. 30 % blood loss causes more strain on the compensatory mechanisms, at 40 % blood loss the possibility of autoregulation is exhausted. All patients with blood loss up to 20 and up to 30 % of the blood volume survived in the future, with 40 % blood loss 30 % of patients could not be saved. In all deceased patients the circulatory reserve was below 50 mW/m2. It has been determined that a decrease in the circulatory reserve to 100 mW/m2 or lower is a serious threat to life and requires great intensive therapy for blood loss, the level of the circulatory reserve of 50 mW/m2 is not compatible with life, that is, it corresponds to irreversible hemorrhagic shock. Keywords: blood loss, hypovolemia, circulatory energy, blood flow power, oxygen reserve, circulatory reserve.

Influences of acute hypervolemic hemodilution on serum levels of S-100β protein, NSE and POCD in elderly patients with spinal surgery

To explore the influences of acute hypervolemic hemodilution(AHH) on serum levels of S-100β protein, neuron specific enolase(NSE) and postoperative cognitive dysfunction POCD in elderly patients with spinal surgery. A total of 80 cases elderly patients requiring elective spinal operation were divided into AHH group and C group according to random digits table, 40 cases in each group, with ASA grade I-II. The patients in AHH group were infused 6% hydroxyethyl starch 130/0.4 at a rate of 20 ml/min after anesthesia induction, and blood volume increased by about 20%, the patients in C group were not received AHH, anesthesia and surgical methods were the same as those in AHH group. Intraoperative blood volume, allogeneic blood transfusion and urine volume were recorded. Mean arterial pressure(MAP), heart rate(HR), central venous pressure(CVP) at preoperative 1 d, 1 h after the start of surgery, end of operation, 12 h after surgery were observed. Arterial blood oxygen content (CaO₂), venous blood oxygen content (CjvO₂), arteriovenous oxygen content difference (Da-jvO₂), and cerebral oxygen uptake(CERO₂) were measured at 1 d before surgery, 15 min after surgery, 45 min after surgery, end of surgery. Mini-mental state examination(MMSE) score and serum levels of S-100β protein, NSE were measured at 1 d before surgery, 1, 3, 7 d after surgery. POCD rates of two groups were recorded. Intraoperative blood loss and allogeneic blood transfusion in AHH group was significantly lower than those in C group(P<0.05), and the urine volume was significantly higher than that in C group (P<0.05). Compared with preoperative 1 day, MAP was decreased and CVP was increased at end of surgery in AHH group, compared with C group at the same time, MAP was lower and CVP was higher in AHH group, but both were in normal range. Compared with preoperative 1 day and C group, the levels of Da-jvO₂ and CERO₂ in AHH group was decreased at 15, 45 min after the start of the operation and end of surgery(P<0.05). Compared with preoperative 1 day, MMSE scores of two groups at 1 day after surgery was decreased (P<0.05), the levels of S-100β protein and NSE were increased(P<0.05), and restored at 3, 7 days after surgery. There was statistical difference in MMSE scores, the levels of S-100β protein, NSE at 1 day after surgery between two groups (P<0.05). There was no statistical difference in POCD rate between two groups(P>0.05). AHH can significantly reduce intraoperative blood loss and blood transfusion in elderly patients with spinal surgery, and decrease the levels of S-100β protein and NSE, does not increase the risk of the occurrence of POCD.

Integrative monitoring of systemic hemodynamics and the oxygen-transport status and the choice of the intensive therapy tactics in patients, suffering an ischemic cerebral insult

Objective. To elaborate the intensive therapy tactic in patients, suffering ischemic cerebral insult (ICI) depending on changes in the systemic hemodynamics indices and the oxygen-transportation status.Маterials and methods. In 42 patients, suffering the ICI of middle severity, ageing 45 - 88 years old, the integrative monitoring of the neurological state severity, systemic hemodynamics indices and the oxygen-transportation status on background of targeted intensive therapy was conducted.&#x0D; Results. In the patients, suffering initial hypoxemia, a hypokinetic heart index (HI) - (2,0±0,1) l×min-1×m-2 and the lowered systemic delivery of oxygen (DO2) - (356±21) ml×min-1×m-2were revealed. Prophylactic oxygenation is needed if the value of the oxygen content in arterial blood (SаO2) exceeds 95% and DO2 is lesser than 520 ml×min-1×m-2. Aiming the achievement of eukinetic values of the HI, correction of vascular spasm and antihypertensive therapy was conducted, using alpha-adrenoblocking agent (urapydil) up to stabilization of the DO2 indices on the level of 520-600 ml×min-1×m-2. In hyperoxidal state a hyperkinetic HI - (3.6±0.1) l×min-1×m-2 and a raised DO2 - (699±14) ml×min-1×m-2 were revealed. Prophylactic oxygenation is not indicated if the value of the SаO2 index exceeds 95% and DO2 exceeds 600 ml×min-1×m-2. Aiming to achieve eukinetic values of HI it is mandatory to conduct antihypertensive therapy, using therapy with аlpha-beta-аdrenoblocking agent (labetalol).&#x0D; Conclusion. Targeted intensive therapy, oriented towards balance with general oxygenation of the organism tissues, normalizes the oxygen-transport homeostasis in shortest terms, what impacts the results of treatment in patients, suffering ICI, immediately.

Hemoconcentration During Maximum Exercise in Miners with Chronic Intermittent Exposure to Hypobaric Hypoxia (3800 m)

To evaluate the effect of maximum exercise on hemoconcentration in miners with chronic intermittent hypobaric hypoxia (CIHH) at 3800 m. Sixteen miners with CIHH at high altitude (3800 m) were subjected to maximum exercise levels on a cycle ergometer, increasing exercise load by 50 W every 3 minutes at sea level and high altitude (3800 m). During exercise, arterial oxygen saturation and heart rate were measured. Blood samples were taken at each step to measure hemoglobin concentration and hematocrit. Arterial blood oxygen content was also calculated. At sea level, a decrease in arterial oxygen saturation to 92.1% ± 2.5% was observed at 150 W and the hematocrit, hemoglobin concentration and oxygen content were not altered. At high altitude, arterial oxygen saturation decreased, reaching 88.2% ± 4.9% at 50 W and remained constant during the entire exercise protocol. Hemoglobin concentration and hematocrit increased reaching 16.4 ± 0.9 g/dL and 48.8% ± 1.6%, respectively, at 100 W and were maintained until recovery. Arterial oxygen content was constant during exercise and increased in the recovery period. An increase in hemoglobin concentration during exercise compensates for the decline in arterial oxygen saturation, meanwhile arterial oxygen content remains constant.

Successful maintenance of key physiological parameters in preterm lambs treated with ex vivo uterine environment therapy for a period of 1 week

Extremely preterm infants born at the border of viability (22-24 weeks' gestation) have high rates of death and lasting disability. Exvivo uterine environment therapy is an experimental neonatal intensive care strategy that provides gas exchange using parallel membranous oxygenators connected to the umbilical vessels, sparing the extremely preterm cardiopulmonary system from ventilation-derived injury. In this study, we aimed to refine our exvivo uterine environment therapy platform to eliminate fetal infection and inflammation, while simultaneously extending the duration of hemodynamically stable exvivo uterine environment therapy to 1 week. Merino-cross ewes with timed, singleton pregnancies were surgically delivered at 112-115 days of gestation (term is ∼150 days) and adapted to exvivo uterine environment therapy (treatment group; n= 6). Physiological variables were continuously monitored; humerus and femur length, ductus arteriosus directional flow, and patency were estimated with ultrasound; serial blood samples were collected for hematology and microbiology studies; weight was recorded at the end of the experiment. Control group animals (n= 7) were euthanized at 122 days of gestation and analyzed accordingly. Bacteremia was defined by positive blood culture. Infection and fetal inflammation was assessed with white blood cell counts (including differential leukocyte counts), plasma and lung proinflammatory cytokine measurements, and lung histopathology. Five of 6 fetuses in the treatment group completed the 1-week study period with key physiological parameters, blood counts remaining within normal ranges, and no bacteremia detected. There were no significant differences (P > .05) in arterial blood oxygen content or lactate levels between exvivo uterine environment therapy and control groups at delivery. There was no significant difference (P> .05) in birthweight between control and exvivo uterine environment groups. In the exvivo uterine environment group, we observed growth of fetal humerus (P < .05) and femur (P < .001) over the course of the 7-day experimental period. There was no difference in airway or airspace morphology or consolidation between control andexvivo uterine environment animals, and there was no increasein the number of lung cells staining positive for T-cell marker CD3+. Five preterm lambs were maintained in a physiologically stable condition for 1 week with significant growth and without clinically significant bacteremia or systemic inflammation. Although substantial further refinement is required, a life support platform based around exvivo uterine environment therapy may provide an avenue to improve outcomes for extremely preterm infants.

Abstract TP418: Red Blood Cell Transfusion Increases Cerebral Oxygen Delivery After Subarachnoid Hemorrhage Regardless of Hemoglobin Level

Introduction: Impaired oxygen delivery (DO 2 ), as a result of reduced cerebral blood flow (CBF), is the hallmark of delayed cerebral ischemia (DCI) following subarachnoid hemorrhage (SAH). Anemia further contributes to reductions in DO 2 and places the brain at risk for infarction. Transfusion, by raising hemoglobin (Hgb) and oxygen content of arterial blood, may be able to reduce the risk of ischemia. However, it is unknown whether an Hgb threshold exists above which CBF will fall sufficient to negate any benefit of transfusion on DO 2 . In this physiologic proof-of-principle study we evaluated whether transfusion improves DO 2 and reduces brain vulnerable to ischemia across a broad range of Hgb values. Methods: 47 SAH patients with/at-risk for DCI with Hgb 7-13 g/dl were transfused 1 unit of red blood cells (RBCs). 15 O-PET imaging was used to measure CBF, DO 2 , and oxygen extraction fraction (OEF) before and after transfusion. Vulnerable brain regions were defined as those with baseline DO 2 &lt; 4.5 ml/100g/min (equivalent to CBF of 25 ml/100g/min at low-normal Hgb). Results: Baseline Hgb was 9.7 g/dl (range 6.9-12.5) and CBF was 43±11 ml/100g/min. After transfusion, Hgb rose by 12% and global DO 2 by 10% (from 5.0 to 5.5 ml/100g/min, p=0.001), with CBF only marginally lower; response to transfusion was not dependent on Hgb level. Transfusion resulted in a greater (16%) rise in DO 2 , associated with a larger reduction in OEF, in vulnerable brain regions (p=0.005 for low vs. normal regions), even after adjusting for Hgb. Number of vulnerable regions was reduced from median 9 to 4 per patient (p=0.005). Conclusions: Transfusion of RBCs to patients at-risk for DCI improves cerebral oxygen delivery, preferentially to vulnerable regions and reduces brain at-risk for ischemia. This physiologic benefit does not appear limited to those with severe anemia but persists to Hgb as high as 13 g/dl. Our findings suggest that restrictive transfusion practices may not be appropriate in this population. Prospective trials are needed to determine if these physiologic benefits outweigh risks of transfusion and translate into clinical prevention of DCI.

Pathophysiology and treatment of high-altitude pulmonary vascular disease.

It is estimated that >140 million people live above 2500 m in various regions of the world.1 There are many challenges to living at high altitude, but chronic exposure to alveolar hypoxia is prominent among them. Inspired Po2 falls from ≈150 mm Hg at sea level to ≈100 mm Hg at 3000 m and 43 mm Hg on the summit of Everest (8400 m).2,3 The body responds by hyperventilating, increasing resting heart rate, and stimulating red cell production in an attempt to maintain the oxygen content of arterial blood at or above sea level values.2 However, hypoxic pulmonary vasoconstriction (HPV) and vascular remodeling, together with increased erythropoiesis, place an increased pressure load on the right ventricle (RV). How well healthy humans adapt to hypoxia depends on their rate of ascent to altitude, the severity and duration of their exposure, and their genetic background. ### Pulmonary Vascular Response to Hypoxia For most mammals, including humans, a rise in pulmonary artery pressure (PAP) is an early and inevitable consequence of ascent to high altitude. Resting mean PAP increases along a parabolic curve from 15 mm Hg at 2000 m to ≈30 mm Hg at 4500 m.4 The exceptions and interindividual variation in the magnitude of response offer a natural experiment that might provide insight into fundamental underlying mechanisms ( vide infra ). The initial rise in PAP on exposure to hypoxia is attributed to HPV. With chronic hypoxia, other mechanisms that likely drive vascular remodeling soon contribute to the elevated pressure (Figure 1A). After 2 or 3 weeks of hypoxia, there is little response to rebreathing 100% oxygen, indicating a structural resistance to pulmonary blood flow rather than one based solely on increased vasomotor tone.6 A fall in PAP on re-exposure to a normal oxygen environment is evident in rats monitored by telemetry over days …

Pulmonary arteriovenous malformations: haemodynamics and shunt closure

The first description of pulmonary arteriovenous malformations (PAVM) was made already in 1897 by Churton [1]. PAVM are abnormal vascular structures that connect the pulmonary arterial bed directly to the pulmonary venous bed, thereby bypassing the pulmonary capillaries and resulting in an intrapulmonary shunt which, depending on number and size of the PAVM, may result in arterial desaturation and paradoxical systemic embolisation [2]. Because the PAVM are thin-walled vascular structures, they are prone to rupture, resulting in haemoptysis. A major step forward in the treatment of PAVM was the use of percutaneous transcatheter embolisation, using femoral venous access [3]. This procedure is safe and reduces the risk of paradoxical thromboembolisation and haemoptysis. Moreover, by reducing shunt flow, arterial oxygen saturation increases. Although percutaneous closure of PAVM has been performed for years, and a surprisingly small effect on pulmonary haemodynamics has been shown [4], the study by Vorselaars and co-workers in the present issue of the Netherlands Heart Journal [5] is the first to investigate the immediate consequences of PAVM closure on systemic haemodynamics. Using Finapres technology, which derives changes in stroke volume and systemic pressure from the pressure wave form as measured on a finger, they describe an overall decrease in stroke volume and cardiac output that corresponds in magnitude with the overall decrease in shunt fraction. This decrease in stroke volume is similar to the decrease in stroke volume, as measured directly by right heart catheterisation, observed in a case study at 4 months follow-up after PAVM [6]. It was speculated that such a decrease in stroke volume helped to explain the absence of an increase in pulmonary artery pressures [4], despite the fact that pulmonary vascular resistance should obviously increase as a consequence of the closure of the low resistance PAVM. The mechanism behind the observed decrease in stroke volume is unclear. It could be speculated that shunt closure and the accompanying increase in pulmonary vascular resistance result in a slight increase in right ventricular afterload, which limits right ventricular output. It is, however, more likely to assume that oxygen is regulated to fulfil the oxygen demand of peripheral tissues; shunt closure increases the oxygen content of arterial blood and hence for the same oxygen delivery, in the presence of improved oxygenation, less flow is required. The latter explanation is in accordance with the observation that the shunt fraction prior to embolisation (14 %) is similar in magnitude to the decrease in cardiac output (10 %) [5]. As pulmonary artery pressure increases during exercise, the driving pressure for the shunt flow increases, resulting in an increased shunt flow, which is accompanied by augmented arterial desaturation during exercise [7–9]. However, exercise capacity is surprisingly well-maintained in patients with PAVM, potentially due to the capability of the right heart to deal with volume overload. Indeed, although most patients report an increased exercise capacity and quality of life following shunt closure, an objective increase in exercise capacity is not found in all patients [10]. It is possible that changes in pulmonary and systemic haemodynamics upon shunt closure, which are relatively small under resting conditions, are exacerbated during exercise. Thus, while the study by Vorselaars in the present issue of the Netherlands Heart Journal provides an important observation in resting patients [5], a comprehensive evaluation of shunt flow, pulmonary and systemic haemodynamics and oxygen saturation during exercise prior to and following shunt closure would be of great benefit to enhance our understanding of the implications of shunt closure on exercise capacity.