Intestinal and Cerebral Oxygenation during Severe Isovolemic Hemodilution and Subsequent Hyperoxic Ventilation in a Pig Model

2002 ◽  
Vol 97 (3) ◽  
pp. 660-670 ◽  
Author(s):  
Jasper van Bommel ◽  
Adrianus Trouwborst ◽  
Lothar Schwarte ◽  
Martin Siegemund ◽  
Can Ince ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Delivery ◽  
Oxygen Supply ◽  
Cerebral Oxygenation ◽  
Oxygen Extraction ◽  
Control Group ◽  
Isovolemic Hemodilution ◽  
Systemic Oxygen ◽  
Fraction Of Inspired Oxygen ◽  
Hyperoxic Ventilation

Background During severe isovolemic hemodilution, determination of critical hematocrit levels for the microvascular oxygenation of different organs might provide more insight into the effect of the redistribution of blood flow and oxygen delivery on the oxygenation of different organs. The effect of an increased amount of dissolved oxygen on tissue oxygenation during severely decreased hematocrit levels is not clear. Methods Fifteen anesthetized pigs were randomized between an experimental group (n = 10), in which severe isovolemic hemodilution was performed with 6% hydroxyethylstarch (1:1), and a time-matched control group (n = 5). Systemic, intestinal, and cerebral hemodynamic and oxygenation parameters were monitored. Microvascular oxygen partial pressure (muPo(2) ) was measured in the cerebral cortex and the intestinal serosa and mucosa, using the oxygen-dependent quenching of Pd-porphyrin phosphorescence. In the final phase of the experiment, fraction of inspired oxygen was increased to 1.0. Results Hemodilution decreased hematocrit from 25.3 +/- 3.0 to 7.6 +/- 1.2% (mean +/- SD). Systemic and intestinal oxygen delivery fell with the onset of hemodilution; intestinal oxygen consumption deceased at a hematocrit of 9.9%, whereas the systemic oxygen consumption decreased at a hematocrit of 7.6%. During hemodilution, the intestinal and cerebral oxygen extraction ratios increased from baseline with 130 and 52%, respectively. Based on the intersection of the two best-fit regression lines, determined by a least sum of squares technique, similar critical hematocrit levels were found for systemic oxygen consumption and the cerebral and intestinal mucosa muPo(2); the intestinal serosa muPo(2) decreased at an earlier stage (P < 0.05). Hyperoxic ventilation improved the muPo(2) values but not systemic or intestinal oxygen consumption. Conclusions During isovolemic hemodilution, the diminished oxygen supply was redistributed in favor of organs with a lower capacity to increase oxygen extraction. It is hypothesized that redirection of the oxygen supply within the intestines resulted in the preservation of oxygen consumption and mucosal muPo(2) compared with serosal muPo(2).

scholarly journals Using dual-calibrated functional MRI to map brain oxygen supply and consumption in multiple sclerosis

2021 ◽  
Author(s):  
Hannah L Chandler ◽  
Rachael C Stickland ◽  
Michael Germuska ◽  
Eleonora Patitucci ◽  
Catherine Foster ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Oxygen Consumption ◽  
Healthy Volunteers ◽  
Oxygen Supply ◽  
Oxygen Extraction Fraction ◽  
Oxygen Extraction ◽  
Group Differences ◽  
Lesion Volume ◽  
Brain Physiology ◽  
Significant Difference

Evidence suggests that cerebrovascular function and oxygen consumption are altered in multiple sclerosis (MS). Here, we quantified the vascular and oxygen metabolic MRI burden in patients with MS (PwMS) and assessed the relationship between these MRI measures of and metrics of damage and disability. In PwMS and in matched healthy volunteers, we applied a newly developed dual-calibrated fMRI method of acquisition and analysis to map grey matter (GM) cerebral blood flow (CBF), oxygen extraction fraction (OEF), cerebral metabolic rate of oxygen consumption (CMRO2) and effective oxygen diffusivity of the capillary network (DC). We also quantified physical and cognitive function in PwMS and controls. There was no significant difference in GM volume between 22 PwMS and 20 healthy controls (p=0.302). Significant differences in CBF (PwMS vs. controls: 44.91 +/- 6.10 vs. 48.90 +/- 5.87 ml/100g/min, p=0.010), CMRO2 (117.69 +/- 17.31 vs. 136.49 +/- 14.48 μmol/100g/min p<0.001) and DC (2.70 +/- 0.51 vs. 3.18 +/- 0.41 μmol/100g/mmHg/min, p=0.002) were observed in the PwMS. No significant between-group differences were observed for OEF (PwMS vs. controls: 0.38 +/- 0.09 vs. 0.39 +/- 0.02, p=0.358). Regional analysis showed widespread reductions in CMRO2 and DC for PwMS compared to healthy volunteers. There was a significant correlation between physiological measures and T2 lesion volume, but no association with current clinical disability. Our findings demonstrate concurrent reductions in oxygen supply and consumption in the absence of an alteration in oxygen extraction that may be indicative of a reduced demand for oxygen (O2), an impaired transfer of O2 from capillaries to mitochondria, and/or a reduced ability to utilise O2 that is available at the mitochondria. With no between-group differences in GM volume, our results suggest that changes in brain physiology may precede MRI-detectable GM loss and thus may be one of the pathological drivers of neurodegeneration and disease progression.

Stroma-free hemoglobin: its presence in plasma does not improve oxygen supply to the resting hindlimb vascular bed of hemodiluted dogs

1991 ◽  
Vol 69 (11) ◽  
pp. 1656-1662 ◽  
Author(s):  
George P. Biro ◽  
Peter J. Anderson ◽  
Scott E. Curtis ◽  
Stephen M. Cain
Keyword(s):  
Vascular Resistance ◽  
Oxygen Delivery ◽  
Oxygen Supply ◽  
Oxygen Extraction ◽  
Free Hemoglobin ◽  
Hemoglobin Solution ◽  
Arterial Blood ◽  
Vascular Bed ◽  
Critical Oxygen ◽  
Plasma Phase

In hemodilution, red cell spacing in the microcirculation is increased, flow distribution may become more heterogeneous, and, as a result, oxygen supply to tissues may suffer. We tested the hypothesis that oxygen extraction from diluted blood may be enhanced by the presence of hemoglobin in the plasma phase in relatively low concentrations. In anesthetized dogs, the hindlimb vascular bed was isolated and perfused with the animal's own blood by a roller pump. One group of dogs (n = 6) was hemodiluted (hematocrit = 15.0 ± 1.0%) with a 6% solution of dextran. A second group of dogs (n = 6) was similarly hemodiluted (hematocrit = 16.0 ± 0.4%) with dextran containing stroma-free hemoglobin solution whereby plasma-phase hemoglobin concentration was raised to 1.1 ± 0.1 g∙dLé−1. Systemic hemodynamic observations were made repeatedly over the subsequent 2.5 h, while blood flow to the hindlimb was progressively reduced in stepwise decrements. The hemoglobin-hemodiluted group showed increased systemic arterial blood pressure and total peripheral resistance when compared with the control (dextran diluted) group. The isolated hindlimb also showed evidence of increased vascular resistance in the hemoglobin-treated group. In each individual animal, critical oxygen delivery and extraction were determined by finding the intercept of the supply-independent and supply-dependent portions of the oxygen uptake/oxygen delivery relationship. Neither the critical oxygen delivery rates (5.75 ± 0.83 vs. 6.41 ± 0.53 mL∙kg−1 min−1) nor critical oxygen extraction ratios (0.75 ± 0.03 vs. 0.76 ± 0.04) were found to be significantly different in the two groups. We conclude that hemoglobin in solution in the plasma at a concentration of about 1 g∙dL−1 induces significant increase in vascular resistance and fails to augment oxygen extraction from diluted blood by the resting hindlimb.Key words: stroma-free hemoglobin solution, oxygen extraction, vasoconstriction, isolated hindlimb vascular bed, oxygen supply.

Hyperoxic Ventilation Reduces 6-Hour Mortality at the Critical Hemoglobin Concentration

2004 ◽  
Vol 100 (1) ◽  
pp. 70-76 ◽  
Author(s):  
Jens Meier ◽  
Gregor I. Kemming ◽  
Hille Kisch-Wedel ◽  
Stefan Wölkhammer ◽  
Oliver P. Habler
Keyword(s):  
Oxygen Supply ◽  
Oxygen Demand ◽  
Hemoglobin Concentration ◽  
Acute Normovolemic Hemodilution ◽  
Oxygen Fraction ◽  
Normovolemic Hemodilution ◽  
Fraction Of Inspired Oxygen ◽  
The Individual ◽  
Hyperoxic Ventilation ◽  
Adequate Tissue

Background Acute normovolemic hemodilution reduces the circulating erythrocyte mass and, thus, the hemoglobin concentration. After extreme acute normovolemic hemodilution to the critical hemoglobin concentration (Hbcrit), oxygen demand of the tissues is no longer met by oxygen supply, and death occurs with increasing oxygen debt. The aim of the current study was to investigate whether ventilation with 100% oxygen (fraction of inspired oxygen [FiO2] = 1.0; hyperoxic ventilation) initiated at Hbcrit could restore adequate tissue oxygenation and prevent death. Methods Fourteen anesthetized pigs ventilated with room air (FiO2 = 0.21) were hemodiluted by exchange of whole blood for 6% hydroxyethyl starch (200,000:0.5) until the individual Hbcrit was reached. Hbcrit was defined as the onset of oxygen supply dependency of oxygen consumption and was identified with indirect calorimetry. For the next 6 h, animals were either ventilated with an FiO2 of 0.21 (n = 7) or an FiO2 of 1.0 (n = 7). Results All animals in the 0.21 FiO2 group died within the first 3 h at Hbcrit (i.e., 6-h mortality 100%). Death was preceded by an increase of serum concentrations of lactate and catecholamines. In contrast to that, six of the seven animals of the 1.0 FiO2 group survived the complete 6-h observation period without lactacidosis and increased serum catecholamines (i.e., 6-h mortality 14%; FiO2 0.21 vs. FiO2 1.0, P &lt; or = 0.05). After 6 h at Hbcrit, the FiO2 was reduced from 1.0 to 0.21, and five of the six animals died within the next 3 h. Conclusion In anesthetized pigs submitted to lethal anemia, hyperoxic ventilation enabled survival for 6 h without signs of circulatory failure.

Capillary density in mammals in relation to body size and oxygen consumption

1961 ◽  
Vol 200 (4) ◽  
pp. 746-750 ◽  
Author(s):  
Knut Schmidt-Nielsen ◽  
Pamela Pennycuik
Keyword(s):  
Oxygen Consumption ◽  
Body Size ◽  
Small Mammals ◽  
Oxygen Delivery ◽  
Oxygen Supply ◽  
Size Range ◽  
Small Animal ◽  
Capillary Density ◽  
High Rate ◽  
High Metabolic Rate

The high metabolic rate per gram of tissue in small mammals requires that oxygen be supplied to the tissues at a higher rate than in larger animals. The high rate of oxygen delivery in the small animal can be accomplished by a) higher capillary density and b) higher unloading tension for oxygen. Both these factors in the oxygen supply vary with body size in such a manner that delivery of oxygen to the tissues is facilitated in the small animal. This paper gives comparative data on capillary density in muscles from 10 mammals of various size. The smallest mammals have significantly higher capillary densities, but the trend is not evident throughout the size range examined. It is therefore reasonable to assume that the factors that relate capillary density and body size are overshadowed by variables such as activity, domestication, cold acclimation, etc., and, perhaps primarily, the size of the muscle fibers, which (although dependent on body size) varies considerably with the type of muscle and its use.

The oxygen consumption/oxygen delivery curve in severe preeclampsia: Evidence for a fixed oxygen extraction state

1993 ◽  
Vol 169 (6) ◽  
pp. 1448-1455 ◽  
Author(s):  
Michael A. Belfort ◽  
John Anthony ◽  
George R. Saade ◽  
Nathan Wasserstrum ◽  
Richard Johanson ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Delivery ◽  
Severe Preeclampsia ◽  
Oxygen Extraction

Effect of Acute Respiratory Acidosis on the Limits of Oxygen Extraction during Hemorrhage

1996 ◽  
Vol 85 (4) ◽  
pp. 817-822 ◽  
Author(s):  
Michael E. Ward
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Oxygen Content ◽  
Oxygen Delivery ◽  
Tissue Oxygenation ◽  
Respiratory Acidosis ◽  
Oxygen Availability ◽  
Oxygen Extraction ◽  
Oxygen Extraction Ratio ◽  
Critical Oxygen

Background Hypercapnia can impair cells' capacity to maintain energy status anerobically and enhances the risk of hypoxic injury when oxygen availability is reduced. The ability to maintain tissue oxygenation is determined by both bulk blood flow and the efficiency of oxygen extraction. Bulk blood flow is maintained during hypercapnia through increased sympathetic activity. The effect of hypercapnia on oxygen extraction, however, is unknown. This study evaluates the effect of hypercapnia on cells' capacity to adapt to reductions in oxygen availability by increasing oxygen extraction. Methods In three groups of paralyzed, mechanically ventilated dogs that were anesthetized with alpha-chloralose, the concentration of carbon dioxide in the inhaled gas mixture was adjusted to achieve normocapnia, moderate hypercapnia (Paco2 = 72 +/- 3 [SE] mmHg) or severe hypercapnia (Paco2 = 118 +/- 4 [SE] mmHg). Stepwise hemorrhage was induced until each dog's blood pressure was destabilized. At each stage in the hemorrhage protocol, the oxygen delivery, oxygen consumption, and oxygen extraction ratios (ratio of arteriovenous oxygen content difference to arterial oxygen content) were determined. Results At the point of onset of delivery dependence of oxygen consumption, the oxygen delivery rate (critical oxygen delivery) was 7.8 +/- 1.5 (SE) ml.kg-1.min-1 and the oxygen extraction ratio (critical oxygen extraction ratio) was 0.72 +/- 0.04 (SE) in the normocapnic dogs. Moderate hypercapnia had no effect on these parameters. In the severely hypercapnic dogs, the critical values for oxygen delivery and extraction ratios were 12.5 +/- 1.8 (SE) ml.kg-1.min-1 and 0.54 +/- 0.035 (SE), respectively (P &lt; 0.05 for differences from the normocapnic dogs). Conclusions The results identify a previously unrecognized threat to tissue oxygenation and emphasize the importance of ensuring adequate oxygen delivery when adopting mechanical ventilatory strategies that permit respiratory acidosis to develop.

Low oxygen extraction despite high oxygen delivery causes low oxygen consumption in patients with burns recovering slowly from operative hypothermia

Surgery ◽  
1995 ◽  
Vol 118 (1) ◽  
pp. 44-48 ◽  
Author(s):  
T SHIOZAKI ◽  
M OHNISHI ◽  
O TASAKI ◽  
A HIRAIDE ◽  
T SHIMAZU ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Delivery ◽  
High Oxygen ◽  
Oxygen Extraction ◽  
Low Oxygen

Postnatal changes in critical cardiac output and oxygen transport in conscious lambs

1987 ◽  
Vol 253 (1) ◽  
pp. H100-H106 ◽  
Author(s):  
J. T. Fahey ◽  
G. Lister
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Oxygen Transport ◽  
Oxygen Extraction ◽  
Base Line ◽  
Arterial Lactate ◽  
Acid Accumulation ◽  
Systemic Oxygen ◽  
The Right ◽  
Lower Cardiac Output

We lowered cardiac output progressively in a controlled, stepwise fashion in conscious, unsedated lambs to determine the critical cardiac output or systemic oxygen delivery (the level at which oxygen consumption decreased abruptly). With the use of incremental inflation of a balloon-tipped catheter placed in the right atrium to lower cardiac output, we examined the response of oxygen consumption, systemic oxygen transport, fractional oxygen extraction, arterial lactate, and blood pressure. We studied lambs at 2 (n = 5), 4 (n = 5), and 8 wk (n = 6) of age and found that the 4-wk-old lambs reached critical values of cardiac output and systemic oxygen transport with the smallest proportional decreases from base-line values. Therefore, the 4-wk-old lambs were the least tolerant of acute decreases in cardiac output. We also found that fractional oxygen extraction was able to increase even after critical systemic oxygen transport was achieved. Furthermore, we found at every age that lactic acid accumulation began when the critical level of cardiac output was reached.

Tolerance to Acute Isovolemic Hemodilution

2003 ◽  
Vol 99 (1) ◽  
pp. 97-104 ◽  
Author(s):  
Philippe Van der Linden ◽  
Stefan De Hert ◽  
Nathalie Mathieu ◽  
Françoise Degroote ◽  
Denis Schmartz ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Oxygen Delivery ◽  
Oxygen Demand ◽  
Hemoglobin Concentration ◽  
Perioperative Period ◽  
Isovolemic Hemodilution ◽  
Anesthetic Depth ◽  
Output Response ◽  
Critical Oxygen

Background Acceptance of a lower transfusion trigger in the perioperative period requires study of the effects of anesthetic depth on the tolerance to acute isovolemic anemia. Anesthetic agents with negative effects on the cardiovascular system may exert proportionately greater depressant effects on cardiac output response than on tissue oxygen demand, reducing tolerance to acute isovolemic anemia. Methods In the first study, animals were anesthetized with halothane (n = 14; 23.8 +/- 4.8 kg, mean +/- SD). In a second study, animals were anesthetized with ketamine (n = 14; 24.3 +/- 4.7 kg). In each study, dogs were randomly allocated to receive either low or high concentrations of anesthetic. Oxygen delivery and oxygen consumption were determined from independent measurements during a stepwise isovolemic hemodilution protocol. In each dog, critical oxygen delivery was determined from a plot of oxygen consumption versus oxygen delivery using a least-sum-of-squares technique. Critical hemoglobin (hemoglobin) was determined from a plot of hemoglobin versus oxygen consumption using the same method. Results With both agents, the higher anesthetic concentration was associated with decreased oxygen consumption, resulting in a lower critical oxygen delivery. However, critical hemoglobin was significantly higher in the animals receiving the higher anesthetic dosage (1.5 vs. 1.0 minimum alveolar concentration of halothane: 4.1 +/- 1.3 vs. 2.3 +/- 0.5 g/dl, P &lt; 0.05; high- vs. low-dose ketamine: 3.7 +/- 1.4 vs. 2.5 +/- 0.6 g/dl, P &lt; 0.05). This was related to a marked blunting of the cardiac output response to hemodilution in the animals receiving the higher anesthetic dosage. Conclusions Increased anesthetic depth with halothane or ketamine resulted in a decreased tolerance to acute anemia, as reflected by a significant increase in critical hemoglobin concentration.

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