Venous Oxygen Partial Pressure Research Articles

Mechanisms of cardiac collapse at high temperature in a marine teleost (Girella nigrians)

Heat-induced mortality in ectotherms may be attributed to impaired cardiac performance, specifically a collapse in maximum heart rate (fHmax), although the physiological mechanisms driving this phenomenon are still unknown. Here, we tested two proposed factors which may restrict cardiac upper thermal limits: noxious venous blood conditions and oxygen limitation. We hypothesized elevated blood [K+] (hyperkalemia) and low oxygen (hypoxia) would reduce cardiac upper thermal limits in a marine teleost (Girella nigricans), while high oxygen (hyperoxia) would increase thermal limits. We also hypothesized higher acclimation temperatures would exacerbate the harmful effects of an oxygen limitation. Using the Arrhenius breakpoint temperature test, we measured fHmax in acutely warmed fish under control (saline injected) and hyperkalemic conditions (elevated plasma [K+]) while exposed to hyperoxia (200% air saturation), normoxia (100% air saturation), or hypoxia (20% air saturation). We also measured ventricle lactate content and venous blood oxygen partial pressure (PO2) to determine if there were universal thresholds in either metric driving cardiac collapse. Elevated [K+] was not significantly correlated with any cardiac thermal tolerance metric. Hypoxia significantly reduced cardiac upper thermal limits (Arrhenius breakpoint temperature [TAB], peak fHmax, temperature of peak heart rate [TPeak], and temperature at arrhythmia [TARR]). Hyperoxia did not alter cardiac thermal limits compared to normoxia. There was no evidence of a species-wide threshold in ventricular [lactate] or venous PO2. Here, we demonstrate that oxygen limits cardiac thermal tolerance only in instances of hypoxia, but that other physiological processes are responsible for causing temperature-induced heart failure when oxygen is not limited.

Therapeutic Hypothermia for Refractory Hypoxemia on Venovenous Extracorporeal Membrane Oxygenation: An In Silico Study.

Patients with respiratory failure may remain hypoxemic despite treatment with venovenous extracorporeal membrane oxygenation (VV-ECMO). Therapeutic hypothermia is a potential treatment for such hypoxia as it reduces cardiac output () and oxygen consumption. We modified a previously published mathematical model of gas exchange to investigate the effects of hypothermia during VV-ECMO. Partial pressures were expressed as measured at 37°C (α-stat). The effect of hypothermia on gas exchange was examined in four clinical scenarios of hypoxemia on VV-ECMO, each with different physiological derangements. All scenarios had arterial partial pressure of oxygen (PaO2) ≤ 46 mm Hg and arterial oxygen saturation of hemoglobin (SaO2) ≤ 81%. Three had high with low extracorporeal blood flow to ratio (). The problem in the fourth scenario was recirculation, with normal . Cooling to 33°C increased SaO2 to > 89% and PaO2 to > 50 mm Hg in all scenarios. Mixed venous oxygen saturation of hemoglobin as % () increased to > 70% and mixed venous partial pressure of oxygen in mm Hg () increased to > 34 mm Hg in scenarios with low . In the scenario with high recirculation, and increased, but to < 50% and < 27 mm Hg, respectively. This in silico study predicted cooling to 33°C will improve oxygenation in refractory hypoxemia on VV-ECMO, but the improvement will be less when the problem is recirculation.

Effect of long-duration oxygen vs room air during labor on umbilical cord venous partial pressure of oxygen: a randomized controlled trial

There are limited data to guide the duration and dose of oxygen supplementation for pregnant women undergoing labor. To assess the effect of maternal long-duration high-concentration oxygen administration during labor on umbilical cord venous partial pressure of oxygen. This randomized clinical trial was conducted between January and October of 2021 in the obstetrics wards of 3 tertiary teaching hospitals in Beijing, China. Women undergoing the latent phase of labor with no existing medical conditions or obstetrical complications who were admitted for delivery were eligible. The women who met inclusion criteria with category I fetal heart rate tracings in labor were randomized in a 1:1 ratio to oxygen or room air. The oxygen group received 10 L of oxygen per minute by simple, tight-fitting face mask until delivery. The room-air group received room air only, without a face mask. The primary outcome was the umbilical cord venous partial pressure of oxygen. A total of 661 women were screened, and 521 were excluded; 140 participants with category I fetal heart rate tracings were enrolled and randomized to oxygen (N=70) or room air (N=70). A total of 135 women with valid paired umbilical cord venous and arterial gas values were included in the umbilical cord venous partial pressure of oxygen and arterial pH analyses. All 140 women were included in the fetal heart rate tracings analysis. Baseline characteristics were similar between the oxygen and room-air groups. The duration of oxygen exposure was approximately 322±147 minutes. There were no differences between the oxygen and room-air groups in the umbilical cord venous partial pressure of oxygen (mean difference, 1.1 mm Hg; 95% confidence interval,-1.0 to 3.2; P=.318) or the proportion of participants with category II fetal heart rate tracings (81.4% vs 78.6%; relative risk, 1.04; 95% confidence interval, 0.88-1.22; P=.672). However, the umbilical cord arterial pH was significantly lower in the oxygen group than in the room-air group (median, 7.23; interquartile range, 7.20-7.27 vs median 7.27; interquartile range, 7.20-7.30; P=.005). Maternal long-duration high-concentration oxygen administration during labor did not affect either the umbilical cord venous partial pressure of oxygen or fetal heart rate pattern distribution but resulted in a deterioration of the umbilical cord arterial pH at birth.

Lung perfusion during veno-venous extracorporeal membrane oxygenation in a model of hypoxemic respiratory failure

BackgroundVeno-venous extracorporeal membrane oxygenation (ECMO) provides blood oxygenation and carbon dioxide removal in acute respiratory distress syndrome. However, during ECMO support, the native lungs still play an important role in gas exchange, functioning as a second oxygenator in series with ECMO. The hypoxic vasoconstriction mechanism diverts regional blood flow within the lungs away from regions with low oxygen levels, optimizing ventilation/perfusion matching. ECMO support has the potential to reduce this adaptive pulmonary response and worsen the ventilation/perfusion mismatch by raising venous oxygen partial pressure. Thus, the objective of this study was to evaluate the effect of ECMO on regional pulmonary perfusion and pulmonary hemodynamics during unilateral ventilation and posterior lung collapse.MethodsFive Agroceres pigs were instrumented, monitored and submitted to ECMO. We used the Electrical Impedance Tomography (EIT) to evaluate lung ventilation and perfusion in all protocol steps. Effects of ECMO support on pulmonary hemodynamics and perfusion involving two different scenarios of ventilation/perfusion mismatch: (1) right-lung selective intubation inducing collapse of the normal left lung and (2) dorsal lung collapse after repeated lung lavage. Data including hemodynamics, respiratory, lung perfusion/ventilation, and laboratory data over time were analyzed with a mixed generalized model using the subjects as a random factor.ResultsThe initiation of ECMO support provided a significant reduction in Mean Pulmonary Artery Pressure (PAPm) in both situations of ventilation/perfusion mismatch. However, distribution of lung perfusion did not change with the use of ECMO support.ConclusionsWe found that the use of ECMO support with consequent increase in venous oxygen pressure induced a significant drop in PAPm with no detectable effect on regional lung perfusion in different scenarios of ventilation/perfusion mismatch.

Physiological responses of juvenile Colossoma macropomum after different periods of air exposure

The objective of this work was to evaluate the physiological responses of juvenile Colossoma macropomum exposed to air for different periods of time. Juveniles weighing 74.78 ± 17.39 g were acclimated for 15 days in 30-L tanks in a recirculating aquaculture system (RAS) at a density of 6 animals/tank. The animals were then fasted for 24 h prior to the air exposure test and six juveniles were captured for blood collection to establish basal levels of the parameters. Next, 24 animals were exposed to air for 30 min and the other 24 for 60 min. Blood samples were taken from six animals of each exposure treatment immediately after exposure (IAE), and the other animals returned to their tanks. Subsequent blood samples were taken for six animals (n = 6) per exposure time at 1 h (1hAE), 24 h (24hAE) and 48 h (48hAE) after air exposure. No mortality was recorded. Hematocrit and hemoglobin did not vary according to air exposure time, collection time or the interaction between these two factors. There was an interaction of the factors times of exposure to air and times of collection for glucose where was higher for the 60 min exposure compared to the 30 min exposure at the 1hAE collection, while after 24hAE the levels did not differ from basal. For lactate there was also an interaction between the factors being higher for the 60 min exposure compared to the 30 min exposure at IAE and 1hAE. Blood pH varied among the collections, with a lower value at 1hAE for the 60 min exposure. The parameters PvCO2 (venous carbon dioxide partial pressure) and PvO2 (venous oxygen partial pressure) were inversely proportional; while PvCO2 increased, PvO2 decreased after collection 1hAE. Values of HCO3− (bicarbonate) differed between exposure times and varied among collections. The electrolytes Cl− (Chloride) and K+ (Potassium) varied among collections in relation to basal, however, they did not differ between exposure times. The value for Na+ (Sodium) for the 60 min exposure at IAE was higher than basal, and only 24hAE was different from basal for both exposures. Ca2+ (Calcium) values differed between exposure times (30 and 60 min) in the 24hAE collection, however, values did not differ from basal. Exposure to air caused physiological, biochemical, gasometric and electrolytic in juvenile C. macropomum. These animals can be considered resistant to this stress due to their ability to restore physiological.

Increased FIO2 influences SvO2 interpretation and accuracy of Fick-based cardiac output assessment in cardiac surgery patients: A prospective randomized study.

Introduction:The study aimed to reveal how the fraction of inspired oxygen (FIO2) affected the value of mixed venous oxygen saturation (SvO2) and the accuracy of Fick-equation-based cardiac output (Fick-CO).Methods:Forty two adult patients who underwent elective cardiac surgery were enrolled and randomly divided into 2 groups: FIO2 < 0.7 or >0.85. Under stable general anesthesia, thermodilution-derived cardiac output (TD-CO), SvO2, venous partial pressure of oxygen, hemoglobin, arterial oxygen saturation, arterial partial pressure of oxygen, and blood pH levels were recorded before surgical incision.Results:Significant differences in FIO2 values were observed between the 2 groups (0.56 ± 0.08 in the <70% group and 0.92 ± 0.03 in the >0.85 group; P < .001). The increasing FIO2 values lead to increases in SvO2, venous partial pressure of oxygen, and arterial partial pressure of oxygen, with little effects on cardiac output and hemoglobin levels. When comparing to TD-CO, the calculated Fick-CO in both groups had moderate Pearson correlations and similar linear regression results. Although the FIO2 <0.7 group presented a less mean bias and a smaller limits of agreement, neither group met the percentage error criteria of <30% in Bland-Altman analysis.Conclusion:Increased FIO2 may influence the interpretation of SvO2 and the exacerbation of Fick-CO estimation, which could affect clinical management.Trial Registration:ClinicalTrials.gov ID number: NCT04265924, retrospectively registered (Date of registration: February 9, 2020).

The effectiveness of different respiration models to the amplitude of waveform information in arterial blood gas

Objective: The objective is to find the characteristics of arterial blood sample waveform in different respiration models. Methods: Six post-operative patients with normal heart function and negative Allen test, were 4 male and 2 female, (59.00±16.64)year, (71.67±0.37)kg, left ventricular ejection fraction(LVEF) (61.33±2.16)%, had been placed the arterial catheterization and central venous catheterization for continuous collecting arterial in 3 different kinds of respiration models: normal breathing, no breathing and deep breathing. We selected two breaths cycles of waveform from each patient for data calculations of magnitudes and time interval. Compare the adjacent highest and lowest values of patients to verify whether there are periodic wave-like signal changes in arterial and venous blood gas in the three breathing states. In addition, statistical t-test analysis was performed on the change amplitude of the periodic wave-like signal of the patient's arterial and venous blood gas to compare whether there is a difference. Results: The heart beat numbers for drawing blood into pipe were 15-16, and all covered more than 2 breathing cycles. There were significant changes of arterial PaO2 (i.e. the highest high values compare to the next lowest values, P<0.05) in three different breathing models(normal, no breathing and high breathing), the magnitudes of which were (9.96±5.18)mmHg, (5.33±1.55)mmHg and (13.13±7.55)mmHg, with (8.09±2.43)%, (5.29±2.19)% and (10.40±2.68)% from their mean respectively. PO2 in venous blood gas did not show wavy changes under normal breathing, 20 s breath holding and high tidal volume ventilation. The amplitudes were (1.63 ± 0.41) mmHg, (1.13 ± 0.41) mmHg and (1.31 ± 0.67) mmHg, which were (3.91 ± 1.22)%, (2.92 ± 1.12)%, (3.33 ± 1.81)%, respectively, which were significantly lower than that of arterial blood gas under the same state, but there was no significant difference between groups. Conclusion: With continuous beat-by-beat arterial blood sampling and ABG analyzing method in three different breathing models, We obtain a clear evidence of the biggest periodic parameters ABG waveform in high breathing models, which followed by normal breathing models, no breathing was the smallest, and the wave variation amplitude of venous oxygen partial pressure was not obvious in the three respiratory states, which implies the oscillatory information of the arterial blood with comes from the gas exchanging in the lung.

Maternal oxygen exposure may not change umbilical cord venous partial pressure of oxygen: non-random, paired venous and arterial samples from a randomised controlled trial

BackgroundDespite the widespread use of oxygen (O2) in intrauterine resuscitation, the obstetric scientists’ understanding of O2 therapy is full of contradictions. We tested the hypothesis that higher maternal arterial partial pressure of oxygen (PO2) is associated with higher umbilical cord venous PO2 (UvPO2).MethodsThis is a planned secondary analysis of a randomised controlled trial (RCT), 443 normal women were 1:1 randomly allocated to receive 2 L/min O2 or room air from the onset of second stage to delivery. We reported that maternal 2 L/min O2 exposure cannot affect the umbilical cord arterial pH or the fetal heart rate (FHR) pattern. In 217 non-random samples, we found 2 L/min O2 exposure increased the maternal arterial PO2 to the median 150 mmHg (hemoglobin would be saturated). The primary outcome for this analysis was UvPO2 in these non-random samples.ResultsThere were no significant differences between the O2 group (N = 107) and the control group (N = 110) in the UvPO2 (median 30.2, interquartile 25.4–35.2 versus median 28.3, interquartile 23.4–35.3, mmHg, P = 0.379). There were also no significant differences between room air and different percentiles of O2 exposure duration (< 25th, ≧ 25th < 50th, ≧ 50th < 75th, ≧ 75th percentile) in the UvPO2.ConclusionsMaternal O2 exposure at super-physiological levels (median arterial blood PO2 150 mmHg) in normal labor may not change the UvPO2.Clinical trial registrationClinicalTrials.govNCT02221440, first posted in 20 August 2014.

Effects of dobutamine on cardiovascular function and oxygen delivery in standing horses.

Dobutamine is routinely used to improve cardiovascular function in anaesthetized horses. However, dobutamine in conscious horses is insufficiently investigated. Ten research horses that were already instrumented for a preceding trial were included into the study. Cardiovascular variables were recorded and blood samples taken after instrumentation (Baseline), before starting dobutamine and after 10min of dobutamine infusion (2µgkg-1 min-1 ). A significant increase in systemic blood pressure, mean pulmonary artery pressure and right atrial pressure, and a decrease in heart rate were observed with dobutamine compared with baseline measurements. Arterial and mixed venous haemoglobin and oxygen content, as well as mixed venous partial pressure of oxygen increased. No significant changes in cardiac output, stroke volume, systemic vascular resistance, arterial partial pressure of oxygen, or oxygen consumption, delivery and extraction ratio were detected. Concluding, dobutamine increased systemic blood pressure without detectable changes in stroke volume, cardiac output or systemic vascular resistance in conscious horses.

TRANSCUTANEOUS OXYGEN MONITORING IN LOUISIANA PINE SNAKES (PITUOPHIS RUTHVENI)

Hypoxic physiological states may occur during anesthetic events of snakes but accurate monitoring of oxygenation is challenging. Oxygenation levels of nine Louisiana pine snakes (Pituophis ruthveni) were assessed using transcutaneous regional oxygen saturation (rSO2) at the level of the liver (rSO2Liver) and at the halfway point of the body (rSO2Half ). Reflectance pulse oximetry measured SpO2, with a sensor overlying the heart. Values were compared with the venous partial pressure of oxygen (PvO2). Measurements were taken during four phases, simulating an anesthetic event: phase 1, breathing room air; phase 2, while supplied with supplemental oxygen via face mask; phase 3, during ketamine and dexmedetomidine sedation; and phase 4, after receiving atipamezole. There were no significant changes in any oxygenation parameters between concurrent phases, but respiratory rate significantly decreased (P = 0.02) between phases 1 and 2. Strong positive associations were found between both rSO2Liver and rSO2Half when compared with PvO2 irrespective of phase (r = 0.72, r = 0.63 respectively), but not with SpO2 (r = 0.3). Strength of correlation varied with each phase but was uniformly strongest for rSO2Liver. The measurement of rSO2 appears superior compared with traditional pulse oximetry for assessing oxygenation levels of snakes.

Koyunlarda Detomidin-Butarfanol-Ketamin ve Atipamezol’ün Klinik, Kardiyorespiratorik, Hematolojik Parametreler Üzerine Etkileri

The aim of this study was to evaluate the sedative-anesthetic effects of detomidine (D) 30 µg/kg, intramuscular (IM), butorphanol (B) 0.2 mg/kg IM and ketamine (K) 5 mg/kg, IM combination in sheep. Five female and nine male healthy (1-2 years old) Akkaraman sheep were used as animal material. Detomidine and butorphanol were used to produce sedation. Ten minutes later K was administrated for anaesthesia. The anaesthetic effect of the drugs was reserved by atipamezole (AT) 30 µg/kg, IM administration at 30 minutes after K injection. The sedative effects of DB demerged in 3 minutes after injection and anaesthetic effects (by the lack of pain stimuli) were visible in 5 minutes after K injection. Heart rate, body temperature and amplitude P values significantly decreased until the administration of AT. Contrarily, respiratory rate, PR interval and R amplitude values increased during anesthesia. Partial venous oxygen pressure (PO2) and Partial venous carbon dioxide pressure (PCO2) values decreased during anaesthesia. There were no significant alterations seen for hematological parameters including hemoglobin (Hg), white blood cell (WBC), red blood cell (RBC) and hematocrit (Ht) values in sheep. As a result, BDK anaesthetic combination depresses the cardiorespiratoric system but produces adequate sedation and anaesthesia for sheep. AT can be safely used for this anaesthetic combination in sheep.

Risk Analysis of Perioperative Death in Lung Transplant Patients With Severe Idiopathic Pulmonary Hypertension

ObjectiveTo investigate the risk factors for perioperative mortality in patients with severe idiopathic pulmonary hypertension (IPAH) undergoing lung transplantation (LTx). MethodsTwenty-two IPAH patients were included in the study and were divided 2 groups: a case group with early death post LTx (n = 5, 22.7%) and the remaining 17 recipients (87.3%), who did not die at perioperative time (the control group). All the preoperative clinical data and surgical procedures were analyzed using an independent t-test and Fisher's exact probability test. ResultsAll the patients had over class III heart function rated by World Health Organization classification. Both groups had significantly reduced capacity of 6-min walking distance (6 MWD), decreased oxygen saturation, increased N-terminal probrain natriuretic peptide (NT-proBNP), certain frequent syncope, hemoptysis, and lower extremity edema. In addition, cardiac catheterization examination demonstrated that all patients had elevated pulmonary artery systolic pressure, mean pulmonary artery systolic pressure, and right atrial pressure. Furthermore, reduced mixed venous oxygen saturation and partial pressure of oxygen were seen in oxygen inhalation in a dose of 5 L/min in both groups. Cardiovascular morphological changes in both groups by cardiac ultrasonography included dilated diameter of the right ventricle and the main pulmonary artery. However, the right ventricular ejection fraction and stroke volume were notedly dropped. Distended inferior vena cava and enhanced frequency of hypertensive tricuspid regurgitation velocity response to stress were seen, and pericardial effusion was developed in both groups of patients. Nevertheless, a paired t-test (n = 5 vs n = 17) showed no significance between groups (P > .05), while there was a significant difference in frequencies of brief loss of consciousness (P < .01). Serum sodium concentration, cardiac index (CI), inner diameter of the left ventricle at end diastolic phase, and inner diameter ratio of RV/LV were 116.80 ± 5.76 mmol/L vs 29.88 ± 7.28 mmol/L (P = .002), 1.30 ± 0.07 L/min/m2 vs 1.58 ± 0.26 L/min/m2 (P = .030), 28.80 ± 3.70 mm vs 34.76 ± 5.43 mm (P = .033) and 1.81 ± 0.28 mmol/L vs 1.43 ± 0.26 (P = .011) between case and control group, respectively. ConclusionsAll patients with IPAH waiting for lung transplantation were in critical condition. The highest death risks at perioperative time in IPAH patients were high frequencies of syncope, hyponatremia, lower CI, inner diameter of the left ventricle, and upward RV/LV ratio.

Cerebral Hyperperfusion and Metabolic Regulation in Response to Hypoxia: Do ATP‐Sensitive Potassium Channels Play a Role?

ATP‐sensitive K+ channels (K+ATP) mediate hypoxia‐induced cerebral vasodilatation and hyperperfusion in animals, a compensatory mechanism that maintains the oxidative metabolic stability of the brain. We then tested whether K+ATP blockade attenuates the increase in cerebral blood flow (CBF) in humans and leads to a shift towards brain non‐oxidative metabolism during isocapnic hypoxia (IH). Seven men (25 ± 4 yrs.) were exposed to 5‐min of normoxia and IH (10% O2) before (BG) and 3 h after Glibenclamide oral administration (AG – 5 mg). Invasive mean arterial pressure (MAP), radial artery and right jugular venous blood saturation, oxygen (PO2) and carbon dioxide (PCO2) partial pressure, glucose and lactate levels, and internal carotid (ICA) and vertebral (VA) artery blood flow (BF, Doppler ultrasound) were quantified over the last 30 s. In another protocol, 5 male subjects (24 ± 4 yrs.) underwent the same procedures before (BPL) and 3 h after placebo ingestion (APL – 5 mg of starch). CBF ((ICA BF + VA BF)×2 (mL/min)), cerebral metabolic rate of O2 (CMRO2), oxygen‐glucose (OGI) and oxygen‐carbohydrate (OCI) indexes were determined in each trial. IH provoked similar arterial desaturation (ΔBG −18.3 ± 6.0 vs. ΔAG −17.9 ± 3.5%, p = 0.784) and PaO2 reduction (ΔBG −80.6 ± 4.8 vs. ΔAG −77.6 ± 9.0 mmHg, p = 0.351). MAP and PaCO2 remained unchanged under both conditions. Smaller increases in ICA (ΔBG +111 ± 94 vs. ΔAG +66 ± 68 mL/min, p = 0.021) and VA BF (ΔBG +44 ± 38 vs. ΔAG +26 ± 39 mL/min, p=0.035) were observed under K+ATP blockade. IH‐induced increase in CBF (ΔBG +310 ± 215 vs. ΔAG +184 ± 150 mL/min, p = 0.017) was attenuated and followed by a smaller increase in CMRO2 (ΔBG +18.9 ± 14.8 vs. ΔAG +4.5 ± 12.2 mmol/100 g/min, p = 0.015). There was no IH‐induced shift to cerebral non‐oxidative metabolism as OGI and OCI did not change. CBF and metabolic responses to IH did not differ between BPL and APL. Therefore, our findings indicate that K+ATP play a role in the human cerebral hyperemia and maintenance of the brain metabolic stability during isocapnic hypoxia.Support or Funding InformationCNPq, CAPES, FAPERJ, FINEPThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of controlled hypoxemia or hypovolemia on global and intestinal oxygenation and perfusion in isoflurane anesthetized horses receiving an alpha-2-agonist infusion

BackgroundAim of this prospective experimental study was to assess effects of systemic hypoxemia and hypovolemia on global and gastrointestinal oxygenation and perfusion in anesthetized horses. Therefore, we anesthetized twelve systemically healthy warmblood horses using either xylazine or dexmedetomidine for premedication and midazolam and ketamine for induction. Anesthesia was maintained using isoflurane in oxygen with either xylazine or dexmedetomidine and horses were ventilated to normocapnia. During part A arterial oxygen saturation (SaO2) was reduced by reducing inspiratory oxygen fraction in steps of 5%. In part B hypovolemia was induced by controlled arterial exsanguination via roller pump (rate: 38 ml/kg/h). Mean arterial blood pressure (MAP), heart rate, pulmonary artery pressure, arterial and central venous blood gases and cardiac output were measured, cardiac index (CI) was calculated. Intestinal microperfusion and oxygenation were measured using laser Doppler flowmetry and white-light spectrophotometry. Surface probes were placed via median laparotomy on the stomach, jejunum and colon.ResultsPart A: Reduction in arterial oxygenation resulted in a sigmoid decrease in central venous oxygen partial pressure. At SaO2 < 80% no further decrease in central venous oxygen partial pressure occurred. Intestinal oxygenation remained unchanged until SaO2 of 80% and then decreased. Heart rate and pulmonary artery pressure increased significantly during hypoxemia. Part B: Progressive reduction in circulating blood volume resulted in a linear decrease in MAP and CI. Intestinal perfusion was preserved until blood loss resulted in MAP and CI lower 51 ± 5 mmHg and 40 ± 3 mL/kg/min, respectively, and then decreased rapidly.ConclusionsUnder isoflurane, intestinal tissue oxygenation remained at baseline when arterial oxygenation exceeded 80% and intestinal perfusion remained at baseline when MAP exceeded 51 mmHg and CI exceeded 40 mL/kg/min in this group of horses.Trial registry number33.14-42,502-04-14/1547.

Hyperbaric oxygen therapy is not associated with oxidative stress assessed using plasma F2-isoprostanes and isofurans

Background and aimsHyperbaric oxygen (HBO) therapy is increasingly used in medical practice as a means of enhancing the formation of collagen matrix and angiogenesis, thus promoting healing in wounds and necrotic tissue. However, there are concerns that oxygen can also associate with increased production of oxygen free radicals and oxidative stress. F2-Isoprostanes (F2-IsoPs) formed by non-enzymatic oxidation of arachidonic acid (AA) are reliable measures for assessing oxidative stress in vivo. In addition, under conditions of high oxygen tension isofurans (IsoFs) are preferentially formed from AA and are considered to better reflect oxidative stress in the setting of high oxygen tension. This study aimed to measure plasma IsoFs and F2-IsoP in patients receiving HBO therapy to treat osteonecrosis secondary to radiation therapy. Our hypothesis was that IsoFs would continue to rise with increasing oxygen pressures in contrast to F2-IsoPs whose synthesis would be reduced. MethodsTwelve patients receiving hyperbaric therapy to treat osteonecrosis secondary to radiation therapy were studied during hyperbaric treatment. Blood samples were collected prior to, during and after cessation of HBO therapy that lasted for 119min. Seven serial blood samples were collected for measurement of plasma F2-IsoPs and IsoFs, blood gases and haemoglobin. ResultsOxygen saturation and venous oxygen partial pressure (PvO2) rose significantly during hyperbaric therapy. However, there were no significant changes in plasma IsoFs or F2-IsoPs during the hyperbaric therapy session. ConclusionIn this study of patients with osteonecrosis, HBO therapy at a maximum pressure of 2.4atm with up to 100% oxygen did not worsen oxidative stress assessed using plasma F2- IsoFs and IsoPs.

Comparison of the effects of phenylephrine and norepinephrine in patients with restrictive transfusion

Objective To compare the effects of phenylephrine and norepinephrine in patients with restrictive transfusion. Methods 65 patients undergoing laparoscopic resection of rectal cancer were selected.According to the random number table method, the patients were randomly divided into 32 cases of observation group(phenylephrine composite restriction infusion) and 33 cases of control group(norepinephrine combined restrictive transfusion). The operation and hemodynamics of the two groups at different time points were compared.At T0, T1, T2, the central venous blood and arterial blood were collected, the central venous blood saturation(ScvO2), arterial blood lactate(Lac), central venous oxygen partial pressure(PcvO2), PaO2, Hb concentrations, venous oxygen content(CcvO2), arterial oxygen content(CaO2), arteriovenous oxygen content difference(Ca-cvO2) and oxygen uptake rate(ERO2) were compared between the two groups. Results The ASA levels(Ⅰ/Ⅱgrade) of the observation group and the control group were 11 cases/21 cases and 13 cases/20 cases, respectively, the difference was not statistically significant(χ2=5.298, P=0.052). The BMI of the observation group and the control group were (20.61±1.65)kg/m2, (21.57±1.42)kg/m2, respectively, the difference was not statistically significant(t=0.652, P=1.980). The fluid replacement of the observation group and the control group were (1 162±113)mL, (1171±104)mL, respectively, the difference was not statistically significant(t=1.734, P=0.065). The blood loss of the observation group and the control group were (276±41)mL, (294±42)mL, respectively, the difference was not statistically significant(t=0.083, P=1.023). The urine volume of the observation group and the control group were (524±113)mL, (532±109)mL, respectively, the difference was not statistically significant(t=1.834, P=0.053). The operation time of the observation group and the control group were (192±24)min, (197±21)min, respectively, the difference was not statistically significant(t=1.367, P=0.073). The MAP at T1-T2 of the two groups increased, the CVP of the two groups was significantly higher at T1, the HR of the two groups was significantly higher at T2.The MAP, CVP, HR between the two groups had no significant differences(all P>0.05). The levels of ScvO2, PcvO2 and PaO2 at T1 were significantly higher than those at T0, on the contrary, the levels of ScvO2, PcvO2 and PaO2 at T2 were significantly lower than those at T0, and the Hb in the observation group was significantly lower at T1-T2, the Hb in the control group was significantly lower at T1-T2, which in the observation group was lower than the control group, the differences were statistically significant(all P 0.05). There were statistically significant differences in CcvO2, CaO2, Ca-cvO2 and ERO2 between the two groups at different time points(all P<0.05). Conclusion Phenylephrine is more effective than norepinephrine in limiting infusion in elderly patients, and it has more obvious effects on tissue oxygen metabolism. Key words: Infusions, intravenous; Norepinephrine; Deoxyepinephrine

Effects of different early infusion rate on hemodynamics of patients undergoing non-stop coronary artery bypass grafts

Objective To investigate the effects of different infusion rate of early infusion on the hemodynamics of patients undergoing coronary artery bypass grafting. Methods Forty-six patients with coronary artery disease who underwent coronary artery bypass surgery were randomly divided into two groups: observation group and control group. After the conventional anesthesia was stable, the patients in the control group were given continuous infusion of 2-3 ml/(kg·h) of normal saline. The patients in the observation group were successfully dissociated 5-7 ml/(kg·h) of liquid infusion before the internal mammary artery was successfully dissociated, then 2-3 ml/(kg·h) speed of liquid infusion was given. Results There was no significant difference in clinical data between the two groups. The hemodynamic parameters such as mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume variation (SVV) and central venous pressure (CVP) in the observation group were significantly better than those in the control group during the operation. The total dose of noradrenaline (NE) and adrenaline (E) in the observation group was significantly lower than that in the control group (t=3.908, 7.452, P=0.043, 0.002). The levels of venous blood oxygen partial pressure (PvO2) and continuous central venous saturation (ScvO2) in the observation group were significantly higher than those in the control group (t=4.099, 3.679, 4.208, 2.214, P=0.046, 0.037, 0.032, 0.049), and the lactic acid level and oxygen uptake rate were significantly lower in the observation group than in the control group. The peak values of lactate and creatinine in the observation group were significantly lower than those in the control group (t=3.709, 2.311, P=0.038, 0.048). The levels of 24-h BNP in the control group were significantly higher than those in the observation group (t=4.911, P=0.041). The level of cTnⅠ in the observation group was significantly lower than that in the free internal mammary artery at 24 h after operation (t=7.224, P=0.011), but no significant difference was found in the control group at 24 h after operation (t=1.097, P=0.087). Conclusion The early and appropriate addition of salt solution, and limiting the amount of fluid during the bypass surgery in non-stop coronary artery bypass surgery can effectively stabilize the hemodynamic state, improve the state of oxygenation and reduce myocardial injury. Key words: Non-stop coronary artery bypass surgery; Restrictive infusion; Tissue oxygenation

Effect of parecoxib sodium pretreatment combined with dexmedetomidine on early postoperative cognitive dysfunction in elderly patients after shoulder arthroscopy: A randomized double blinded controlled trial

Study objectiveTo evaluate effect of parecoxib sodium pretreatment combined with dexmedetomidine on early postoperative cognitive dysfunction in elderly patients after shoulder arthroscopy. DesignRandomized, double-blind study. SettingUniversity-affiliated teaching hospital. PatientsOne hundred and fifty-two elderly patients scheduled for shoulder arthroscopy. InterventionsAt 15min before the induction of anesthesia, 152 patients received intravenously parecoxib sodium 40mg and dexmedetomidine at a dose of 0.5μg/kg over 15min, followed by a continuous infusion at a rate of 0.5μg/kg/h until the end of surgery. Then all patients who received postoperative patient-controlled intravenous analgesia were divided 2 groups: sufentanil(0.04μg/kg/h, S group), sufentanil (0.04μg/kg/h) plus dexmedetomidine(0.06μg/kg/h) (SD group). MeasurementsThe mini–mental status examination score in SD group was significantly higher than S group at 1, 2 and 7days after surgery. The incidence of postoperative cognitive dysfunction during 7days after surgery in S and SD groups was respectively 17.1% and 6.7%. Compared with the S group, the visual analogue scale scores at rest and upon movement were significantly lower at 6, 14, 24, 36 and 48h after surgery in SD group; analgesia pump liquid amount during 24h after surgery and number of rescue analgesia during 48h after surgery were significantly lower in SD group. Jugular venous oxygen partial pressure and jugular venous oxygen saturation values in SD group were significantly higher than S group at postoperative 24h. The occurrence of nausea and vomiting within 48h after surgery in SD group were significantly lower than S group. We found no complications including respiratory depression and sinus bradycardia within 48h after surgery in all patients. ConclusionsParecoxib sodium pretreatment combined with dexmedetomidine could reduce the incidence of early postoperative cognitive dysfunction in elderly patients. This might be related to the improvement of postoperative analgesia effect and cerebral oxygen metabolism in patients.

Clinical Study of Acute Vasoreactivity Testing in Patients with Chronic Thromboembolic Pulmonary Hypertension.

Background:The clinical significance of acute vasoreactivity testing (AVT) in patients with chronic thromboembolic pulmonary hypertension (CTEPH) remains unclear. We analyzed changes in hemodynamics and oxygenation dynamics indices after AVT in patients with CTEPH using patients with pulmonary arterial hypertension (PAH) as controls.Methods:We analyzed retrospectively the results of AVT in 80 patients with PAH and 175 patients with CTEPH registered in the research database of Beijing Chao-Yang Hospital between October 2005 and August 2014. Demographic variables, cardiopulmonary indicators, and laboratory findings were compared in these two subgroups. A long-term follow-up was conducted in patients with CTEPH. Between-group comparisons were performed using the independent-sample t-test or the rank sum test, within-group comparisons were conducted using the paired t-test or the Wilcoxon signed-rank test, and count data were analyzed using the Chi-squared test. Survival was estimated using the Kaplan-Meier method and log-rank test.Results:The rates of positive response to AVT were similar in the CTEPH (25/175, 14.3%) and PAH (9/80, 11.3%) groups (P > 0.05). Factors significantly associated a positive response to AVT in the CTEPH group were level of N-terminal pro-brain natriuretic peptide (≤1131.000 ng/L), mean pulmonary arterial pressure (mPAP, ≤44.500 mmHg), pulmonary vascular resistance (PVR, ≤846.500 dyn·s−1·m−5), cardiac output (CO, ≥3.475 L/min), and mixed venous oxygen partial pressure (PvO2, ≥35.150 mmHg). Inhalation of iloprost resulted in similar changes in mean blood pressure, mPAP, PVR, systemic vascular resistance, CO, arterial oxygen saturation (SaO2), mixed venous oxygen saturation, partial pressure of oxygen in arterial blood (PaO2), PvO2, and intrapulmonary shunt (Qs/Qt) in the PAH and CTEPH groups (all P > 0.05). The survival time in patients with CTEPH with a negative response to AVT was somewhat shorter than that in AVT-responders although the difference was not statistically significant (χ2 = 3.613, P = 0.057). The survival time of patients with CTEPH who received calcium channel blockers (CCBs) was longer than that in the group with only basic treatment and not shorter than that of patients who receiving targeted drugs or underwent pulmonary endarterectomy (PEA) although there was no significant difference between the four different treatment regimens (χ2 = 3.069, P = 0.381).Conclusions:The rates of positive response to AVT were similar in the CTEPH and PAH groups, and iloprost inhalation induced similar changes in hemodynamics and oxygenation dynamics indices. A positive response to AVT in the CTEPH group was significantly correlated with milder disease and better survival. Patients with CTEPH who cannot undergo PEA or receive targeted therapy but have a positive response to AVT might benefit from CCB treatment.

Agreement and Correlation between Arterial and Central Venous Blood Gas Following Coronary Artery Bypass Graft Surgery.

Arterial blood sampling, used to assess patients in acute conditions, may result in complications such as thrombosis and embolism. However, it can be replaced by venous blood sampling, but there is a dearth of information on this. To assess the correlation and agreement between the arterial and central venous blood gases analyses in patients undergoing elective Coronary Artery Bypass Graft (CABG) surgery. In this cross-sectional study, 100 ICU patients undergoing elective CABG surgery were recruited. 2 mm arterial and a 2 mm venous blood samples were obtained from each patient's arterial and central venous lines, respectively. To predict Arterial Blood Gas (ABG) values based on central Venous Blood Gas (VBG) values, the linear regression analysis was used and for evaluating their agreement Bland-Altman method was used. In total of 200 samples were obtained. The mean and Standard Deviation (SD) of age was 58.9±9.1 years and 51% of the participants were female. There was a strong correlation between ABG and central VBG values regarding pH, partial Pressure of Carbon Dioxide (PCO2), Bicarbonate (HCO3) and Base Excess (BE) (r= 0.73, r=0.74, r=0.67 and r=0.71, respectively; p<0.001); however, the correlation between the arterial and venous Partial Pressure of Oxygen (PO2) and Oxygen Saturation (SO2) was moderate (r=0.29, p=0.005 and r=0.27, p=0.006, respectively). The Bland-Altman analysis showed an excellent agreement between all the variables (p<0.001). Central VBG analysis cannot replace ABG analysis in measuring exact PO2 status, necessitating arterial sampling in some matters, but with respect to the accuracy of pulse oximetry measurements in determining the exact PO2 status, for the rest of the indices a central VBG rather than an ABG can be utilised for determining patient's acid-base status. Particularly in patients who are hospitalised for a long time and have a central venous catheter in place like patients who have undergone CABG, thus reducing the risk and need for invasive arterial sampling.