Neonatal intestinal oxygen consumption during arterial hypoxemia

1983 ◽  
Vol 244 (3) ◽  
pp. G278-G283
Author(s):  
D. I. Edelstone ◽  
D. R. Lattanzi ◽  
M. E. Paulone ◽  
I. R. Holzman
Keyword(s):  
Intestinal Tract ◽  
Concentration Difference ◽  
Fick Principle ◽  
Arterial Blood ◽  
Wide Range ◽  
O2 Extraction ◽  
Neonatal Lambs ◽  
O2 Supply ◽  
Oxygen Requirements ◽  
O2 Delivery

In 12 chronically catheterized neonatal lambs, we determined intestinal tract blood flow (Qi) and O2 consumption (VO2i) at O2 contents of arterial blood (CaO2) ranging from 15.3 to 3.2 ml O2/dl blood. We measured Qi with the radioactive microsphere technique and computed intestinal O2 delivery (DO2i), VO2i, and O2 extraction (VO2i/DO2i) using the Fick principle. In lambs breathing air, mean Qi = 214 ml X min-1 X 100 g intestine-1, DO2i = 27.0 ml O2 X min-1 X 100 g-1, O2 extraction = 21%, and VO2i = 5.6 ml O2 Xmin-1 X 100 g-1. During reductions in CaO2, Qi and DO2i decreased. Intestinal O2 extraction increased sufficiently, however, so that VO2i was maintained over the range of CaO2 from 15.3 to about 6.5 ml O2/dl blood. VO2i was independent of Qi at Qi greater than 160 ml X min-1 X 100 g-1. When CaO2 was reduced below values of 6.5 ml O2/dl blood, corresponding to Qi less than 160 ml X min-1 X 100 g-1, VO2i fell in association with increases in the H+ concentration difference between mesenteric venous and arterial blood. These data indicate that the intestinal tract of the neonatal lamb can meet its oxygen requirements when O2 supply varies over a wide range. When O2 availability reaches a critically low level, intestinal anaerobic metabolism develops as the O2 supply to the neonatal intestinal tract becomes inadequate for the O2 demand.

Analysis of oxygen delivery and uptake relationships in the Krogh tissue model

1989 ◽  
Vol 67 (3) ◽  
pp. 1234-1244 ◽  
Author(s):  
P. T. Schumacker ◽  
R. W. Samsel
Keyword(s):  
Blood Flow ◽  
Critical Point ◽  
Real Data ◽  
Whole Body ◽  
O2 Uptake ◽  
Highly Sensitive ◽  
O2 Extraction ◽  
O2 Supply ◽  
Experimental Findings ◽  
O2 Delivery

Normally, tissue O2 uptake (VO2) is set by metabolic activity rather than O2 delivery (QO2 = blood flow X arterial O2 content). However, when QO2 is reduced below a critical level, VO2 becomes limited by O2 supply. Experiments have shown that a similar critical QO2 exists, regardless of whether O2 supply is reduced by progressive anemia, hypoxemia, or reduction in blood flow. This appears inconsistent with the hypothesis that O2 supply limitation must occur by diffusion limitation, since very different mixed venous PO2 values have been seen at the critical point with hypoxic vs. anemic hypoxia. The present study sought to begin clarifying this paradox by studying the theoretical relationship between tissue O2 supply and uptake in the Krogh tissue cylinder model. Steady-state O2 uptake was computed as O2 delivery to tissue representative of whole body was gradually lowered by anemic, hypoxic, or stagnant hypoxia. As diffusion began to limit uptake, the fall in VO2 was computed numerically, yielding a relationship between QO2 and VO2 in both supply-independent and O2 supply-dependent regions. This analysis predicted a similar biphasic relationship between QO2 and VO2 and a linear fall in VO2 at O2 deliveries below a critical point for all three forms of hypoxia, as long as intercapillary distances were less than or equal to 80 microns. However, the analysis also predicted that O2 extraction at the critical point should exceed 90%, whereas real tissues typically extract only 65–75% at that point. When intercapillary distances were larger than approximately 80 microns, critical O2 extraction ratios in the range of 65–75% could be predicted, but the critical point became highly sensitive to the type of hypoxia imposed, contrary to experimental findings. Predicted gas exchange in accord with real data could only be simulated when a postulated 30% functional peripheral O2 shunt (arterial admixture) was combined with a tissue composed of Krogh cylinders with intercapillary distances of less than or equal to 80 microns. The unrealistic efficacy of tissue O2 extraction predicted by the Krogh model (in the absence of postulated shunt) may be a consequence of the assumed homogeneity of tissues, because real tissues exhibit many forms of heterogeneity among capillary units. Alternatively, the failure of the original Krogh model to fully predict tissue O2 supply dependency may arise from basic limitations in the assumptions of that model.

O2 delivery to contracting muscle during hypoxic or CO hypoxia

1987 ◽  
Vol 63 (2) ◽  
pp. 726-732 ◽  
Author(s):  
C. E. King ◽  
S. L. Dodd ◽  
S. M. Cain
Keyword(s):  
Blood Flow ◽  
Gastrocnemius Muscle ◽  
Dissociation Curve ◽  
Muscle Preparation ◽  
O2 Uptake ◽  
Oxyhemoglobin Dissociation Curve ◽  
O2 Extraction ◽  
O2 Supply ◽  
O2 Delivery ◽  
Oxyhemoglobin Dissociation

The consequences of a decreased O2 supply to a contracting canine gastrocnemius muscle preparation were investigated during two forms of hypoxia: hypoxic hypoxia (HH) (n = 6) and CO hypoxia (COH) (n = 6). Muscle O2 uptake, blood flow, O2 extraction, and developed tension were measured at rest and at 1 twitch/s isometric contractions in normoxia and in hypoxia. No differences were observed between the two groups at rest. During contractions and hypoxia, however, O2 uptake decreased from the normoxic level in the COH group but not in the HH group. Blood flow increased in both groups during hypoxia, but more so in the COH group. O2 extraction increased further with hypoxia (P less than 0.05) during concentrations in the HH group but actually fell (P less than 0.05) in the COH group. The O2 uptake limitation during COH and contractions was associated with a lesser O2 extraction. The leftward shift in the oxyhemoglobin dissociation curve during COH may have impeded tissue O2 extraction. Other factors, however, such as decreased myoglobin function or perfusion heterogeneity must have contributed to the inability to utilize the O2 reserve more fully.

Adrenergic vasoconstriction augments tissue O2 extraction during reductions in O2 delivery

1994 ◽  
Vol 76 (4) ◽  
pp. 1454-1461 ◽  
Author(s):  
L. A. Maginniss ◽  
H. Connolly ◽  
R. W. Samsel ◽  
P. T. Schumacker
Keyword(s):  
Blood Volume ◽  
Supply And Demand ◽  
Sympathetic Tone ◽  
Whole Body ◽  
Metabolic Demand ◽  
O2 Extraction ◽  
Limit Blood Flow ◽  
Anesthetized Dogs ◽  
O2 Supply ◽  
O2 Delivery

When systemic O2 delivery is reduced, increases in systemic O2 extraction are facilitated by sympathetically mediated increases in vascular resistance that limit blood flow to regions with low metabolic demand. Local metabolic vasodilation competes with this vasoconstriction, thereby effecting a balance between tissue O2 supply and demand. This study examined the role of sympathetically mediated vasoconstriction on the critical level of O2 extraction in hindlimb and whole body during progressive reductions in O2 delivery. In anesthetized dogs, the left hindlimb was vascularly isolated and its O2 delivery was decreased in stages by reducing the speed of an occlusive pump. In a normovolemic group (n = 6), blood volume was maintained to minimize sympathetic tone while flow to the hindlimb was reduced. In a hypovolemic group (n = 6), blood volume was removed in stages to augment sympathetic tone progressively while flow to the limb was reduced simultaneously. A phenoxybenzamine group (n = 6) was identical to the hypovolemic group, except that alpha-adrenergic effects were inhibited with phenoxybenzamine (3 mg/kg). The systemic critical O2 extraction ratio in the phenoxybenzamine group (0.60 +/- 0.06) was less than for the hypovolemic group (0.71 +/- 0.04; P = 0.004). In the hindlimb, critical O2 extractions were significantly less in the normovolemic (0.46 +/- 0.17) and phenoxybenzamine (0.49 +/- 0.10) groups compared with the hypovolemic group (0.72 +/- 0.10; P < or = 0.008).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of varying hematocrit on intestinal oxygen uptake in neonatal lambs

1985 ◽  
Vol 248 (4) ◽  
pp. G432-G436 ◽  
Author(s):  
I. R. Holzman ◽  
B. Tabata ◽  
D. I. Edelstone
Keyword(s):  
Blood Flow ◽  
Anaerobic Metabolism ◽  
Lactate Production ◽  
Oxygen Availability ◽  
Intestinal Blood Flow ◽  
Oxygen Extraction ◽  
Base Line ◽  
Wide Range ◽  
O2 Extraction ◽  
Neonatal Lambs

We chronically catheterized 15 newborn lambs (9.5 +/- 2.8 days) and measured intestinal blood flow (Qi) by the radionuclide microsphere technique at hematocrit levels ranging from 10 to 55%. Seven animals were made progressively anemic and eight polycythemic by means of exchange transfusions. Using the Fick principle, we calculated intestinal oxygen delivery (Di o2), oxygen consumption (Vi o2), and oxygen extraction. Initial base-line values were Qi = 195.5 ml . min-1 . 100 g intestine-1, Di o2 = 22.1 ml . min-1 . 100 g-1, Vi o2 = 4.8 ml . min-1 . 100 g-1, and O2 extraction = 22.5%. As the hematocrit was lowered, Di o2 decreased and O2 extraction increased and vice versa when the hematocrit was raised. Vi o2 remained constant, but Qi did not correlate with changes in hematocrit. However, intestinal blood flow, as a percent distribution of total blood flow, decreased with lower hematocrit levels. At no time was there any evidence of anaerobic metabolism as measured by excess lactate production. Our data indicate that the intestines of neonatal lambs are capable of maintaining their metabolic needs over a wide range of oxygen availability induced by a changing hematocrit. The primary mechanism is through alteration of oxygen extraction. Within the range of our experiments, no critically low oxygen availability was attained at which anaerobic metabolism became significant.

Effects of hyperoxia on maximal leg O2 supply and utilization in men

1993 ◽  
Vol 75 (6) ◽  
pp. 2586-2594 ◽  
Author(s):  
D. R. Knight ◽  
W. Schaffartzik ◽  
D. C. Poole ◽  
M. C. Hogan ◽  
D. E. Bebout ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Venous Blood ◽  
Normal Subjects ◽  
Constant Infusion ◽  
Venous Blood Flow ◽  
O2 Uptake ◽  
Fick Principle ◽  
The Mean ◽  
O2 Supply ◽  
O2 Delivery

We studied O2 transport in the leg to determine if hyperoxia will increase the maximal rate of O2 uptake (VO2max) in exercising muscle. An increase in inspired O2 fraction (FIO2) from 0.21 to 1.00 was postulated to have the following effects: 1) increase the leg VO2max by approximately 5–10%, 2) increase the maximal O2 delivery [arterial O2 concentration.flow (CaO2.Q] by approximately 10%, and 3) raise the leg VO2max in proportion to both the femoral venous PO2 and mean leg capillary PO2. To test these hypotheses, 11 men performed cycle exercise to the highest work rates (WRmax) they could achieve while breathing 100% O2 (hyperoxia), 21% O2 (normoxia), and 12% O2 (hypoxia). Leg VO2 was derived from duplicate measurements of femoral venous blood flow and CaO2 and femoral venous blood O2 concentrations (CVO2) at 20, 35, 50, 92, and 100% WRmax in each FIO2. Femoral venous leg Q (Qleg) was measured by the constant-infusion thermodilution technique, and leg O2 uptake (VO2) was determined by the Fick principle [VO2 = Qleg(CaO2-CVO2)]. Leg VO2max was the mean of duplicate values of VO2 at 100% WRmax for each FIO2. Hyperoxia increased leg VO2max by 8.1% (P = 0.016) and maximal O2 delivery by 10.9% (P = 0.05) without changing Qleg. There was a significant increase in femoral venous PO2 (P < 0.001) that was proportionally greater than the increase in leg VO2max. The results support our first and second hypotheses, providing direct evidence that in normal subjects leg VO2max is limited by O2 supply during normoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathological O2 supply dependence of diaphragmatic and systemic O2 uptake during endotoxemia

1994 ◽  
Vol 77 (3) ◽  
pp. 1093-1100 ◽  
Author(s):  
W. S. Kim ◽  
M. E. Ward ◽  
S. N. Hussain
Keyword(s):  
Escherichia Coli ◽  
Cardiac Output ◽  
O2 Consumption ◽  
O2 Uptake ◽  
Mechanically Ventilated ◽  
Endotoxin Infusion ◽  
Left Hemidiaphragm ◽  
O2 Extraction ◽  
O2 Supply ◽  
O2 Delivery

Our aim was to assess whether endotoxemia impairs the ability of the diaphragm to extract O2 and whether this defect leads to a greater dependence of O2 uptake on O2 delivery. In two groups of anesthetized mechanically ventilated dogs, the left hemidiaphragm was vascularly isolated. Diaphragmatic blood flow and cardiac output (CO) were measured simultaneously in all animals. Saline (S group) or Escherichia coli endotoxin (100 mg; E group) was infused intravenously over 60 min. In both groups, CO was reduced in stages by controlled hemorrhage, and systemic and diaphragmatic O2 deliveries and consumptions were measured at each stage to construct the O2 delivery-O2 consumption relationships. In the S group, the average systemic O2 delivery below which O2 uptake became supply dependent was 7.2 ml.kg-1.min-1. At this O2 delivery, systemic O2 extraction ratio (ER) averaged 67.9%, whereas the maximum O2 ER was 91.3%. Critical diaphragmatic O2 delivery and critical and maximum diaphragmatic O2 ER, by comparison, averaged 9.0 ml.kg-1.min-1, 65%, and 81.9%, respectively. Endotoxin infusion raised critical systemic O2 delivery to 16.7 ml.kg-1.min-1 (P < 0.05) and reduced critical and maximum systemic O2 ER to 55.5 and 77% (P < 0.05), respectively. Similarly, critical diaphragmatic O2 delivery in the E group increased to 14.8 ml.kg-1.min-1 (P < 0.05), whereas critical and maximum O2 ER declined to 51.8 and 72.8%, respectively (P < 0.05). Thus, endotoxemia impairs diaphragmatic O2 extraction. This, in turn, leads to a greater dependence of diaphragmatic O2 uptake on O2 delivery.

Adenosine infusion does not improve maximal O2 uptake in isolated working dog muscle

1994 ◽  
Vol 76 (6) ◽  
pp. 2820-2824 ◽  
Author(s):  
S. S. Kurdak ◽  
M. C. Hogan ◽  
P. D. Wagner
Keyword(s):  
Vascular Resistance ◽  
Gastrocnemius Muscle ◽  
Venous Blood ◽  
Blood Gases ◽  
O2 Uptake ◽  
Vascular Perfusion ◽  
Fick Principle ◽  
O2 Extraction ◽  
Before And After ◽  
O2 Delivery

We asked whether maximally working muscle could increase O2 extraction at fixed O2 delivery [i.e., improve maximal O2 uptake (VO2max)] when vascular resistance was decreased with adenosine (A) infusion. We postulated that a reduction in vascular resistance at the same blood flow (Q) might result in more uniform vascular perfusion and also possibly increase red blood cell transit time, thereby potentially improving the ability of the tissue to extract O2. Pump-perfused isolated dog gastrocnemius muscle (n = 6) was stimulated maximally at each of two levels of Q: 110 +/- 3 and 54 +/- 4 (SE) ml.100 g-1.min-1 [normal control (C) and ischemia (I), respectively], both before and after giving 10(-2) M of A solution in each case. Arterial and venous blood samples were taken to measure blood gases, and the Fick principle was used to calculate O2 uptake. Resistance decreased significantly after A treatment in both groups (1.2 +/- 0.1 vs. 0.9 +/- 0.1 and 1.3 +/- 0.1 vs. 1.1 +/- 0.1 mmHg.ml-1.100 g.min for C vs. C + A and I vs. I + A, respectively; P < 0.01). O2 delivery was lower with I but did not change at either perfusion rate when A was infused. VO2max also decreased significantly with I but was no different when A was added (13.8 +/- 0.7 vs. 13.8 +/- 0.9 and 8.4 +/- 0.5 vs. 8.2 +/- 0.6 ml.100 g-1.min-1 for C vs. C + A and I vs. I + A, respectively). These results show that the decrease in resistance with A did not lead to changes in VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic hemorrhage augments local O2 extraction in canine intestine

1994 ◽  
Vol 77 (5) ◽  
pp. 2291-2298 ◽  
Author(s):  
R. W. Samsel ◽  
P. T. Schumacker
Keyword(s):  
Blood Volume ◽  
Sympathetic Tone ◽  
Extraction Ratio ◽  
Intestinal Segment ◽  
Intact Group ◽  
O2 Extraction ◽  
Anesthetized Dogs ◽  
O2 Supply ◽  
O2 Delivery ◽  
Adrenergic Effects

When O2 delivery (QO2) to a tissue is reduced, microvascular adjustments facilitate increases in O2 extraction, thereby delaying the onset of O2 supply-limited metabolism until a critically low QO2 is reached. The present study investigated the contribution of the autonomic nervous system to these adjustments by measuring O2 extraction in isolated intestine. In anesthetized dogs, a 30- to 50-g segment of intestine was vascularly isolated and its QO2 was decreased in stages by reducing the speed of an occlusive pump. In a normovolemic group (n = 11), blood volume was maintained to minimize sympathetic tone while flow to the intestine was reduced. In a hypovolemic group (n = 7), blood volume was removed in stages to augment sympathetic tone as flow to the intestinal segment was simultaneously reduced. A hypovolemic alpha-adrenergic-blocked (alpha-blocked) group (n = 6) was identical to the corresponding alpha-adrenergic intact (alpha-intact) group except that alpha-adrenergic effects were inhibited with phenoxybenzamine (3 mg/kg). The systemic critical O2 extraction ratio in the alpha-blocked group (69 +/- 6%) was less than that in the alpha-intact group (77 +/- 7%; P = 0.05). In the intestine, the critical O2 extraction ratio was significantly poorer in the normovolemic (45 +/- 11%) group than in either hypovolemic group (alpha-intact: 69 +/- 3%, P < 0.00005; alpha-blocked: 62 +/- 9%, P < 0.005). These findings demonstrate that systemic hemorrhage significantly augments critical O2 extraction in intestine during progressive local stagnant hypoxia and suggest that nonadrenergic vasoconstrictor mechanisms may play an important role.

O2 transfer from single microvessels to acinar cells in secretin-stimulated pancreas of rat

1996 ◽  
Vol 270 (5) ◽  
pp. H1704-H1711 ◽  
Author(s):  
A. Seiyama ◽  
S. Tanaka ◽  
H. Kosaka ◽  
T. Shiga
Keyword(s):  
Exocrine Pancreas ◽  
Blood Flow Rate ◽  
Cell Velocity ◽  
Wide Range ◽  
O2 Extraction ◽  
Red Blood Cell Velocity ◽  
O2 Supply ◽  
Hb Concentration ◽  
Microvessel Wall ◽  
O2 Transfer

O2 transfer from the inside to the outside of single microvessels in the resting and secretin-stimulated exocrine pancreas of rats was investigated by dual-spot microspectroscopy. Measurements of intravascular hemoglobin (Hb) concentration, O2 saturation of Hb, and velocity of flowing red blood cells were carried out in single microvessels at the edge of the exocrine pancreas of anesthetized rats. The rate of O2 release (Ro2) from a single microvessel wall was constant [approximately 2 nmol.cm-2.s-1] over a wide range of oxyhemoglobin inflow ([HbO2] inflow; 200-700 fmol/s) but decreased almost linearly with an [HbO2] inflow < 200 fmol/s, where [HbO2] inflow is defined as the product of inflowing oxyhemoglobin concentration ([HbO2]) and blood flow rate. When the exocrine pancreas was stimulated with secretin either by superfusion (> or = 0.3 nM) or by intravenous infusion (> or = 0.5 microgram.kg-1.h-1), the Ro2 as well as the pancreatic secretion increased about two times higher than the basal values. With secretin administration, it was found that 1) an inverse relationship between red blood cell velocity and intravascular Hb concentration held and thus 2) [HbO2] inflow was maintained within the basal level (i.e., 200-700 fmol/s). Furthermore, 3) the elevation of Ro2 from single microvessels was accomplished by the increased O2 extraction instead of the increased O2 supply in the microvessels.

Effect of stimulation of ansa subclavia on regional myocardial O2 supply and O2 consumption

1983 ◽  
Vol 244 (1) ◽  
pp. H68-H72
Author(s):  
E. Buchweitz ◽  
H. R. Weiss
Keyword(s):  
Blood Flow ◽  
Regional Blood Flow ◽  
O2 Consumption ◽  
Sympathetic Stimulation ◽  
Flow Measurements ◽  
Fick Principle ◽  
O2 Extraction ◽  
O2 Supply ◽  
Venous O2 Saturation ◽  
Stimulation Of

Cardiac sympathetic nerve stimulation produces increases in various indices of cardiac work and metabolism. To determine how these increased O2 demands are met, the effects of stimulation of the ansa subclavia on regional arterial and venous O2 saturation, O2 extraction, blood flow, and O2 consumption were determined in the hearts of 16 pentobarbital-anesthetized open-chest dogs. Microspectrophotometric observations of small regional arteries and veins in quick-frozen hearts to determine regional O2 extraction were combined with regional blood flow measurements with radioactive microspheres to determine regional myocardial O2 consumption by the Fick principle. Ansa subclavia stimulation produced significant increases in maximum rate of pressure development, heart rate, and blood pressure. Under control conditions, venous O2 saturation was lower and O2 extraction higher in the subendocardial compared with the subepicardial region of the left ventricle. While sympathetic stimulation did not alter the mean O2 extraction or venous O2 saturation values, there were no longer significant subepicardial vs. subendocardial differences in these parameters. Flow and O2 consumption in these regions increased proportionally during stimulation. The ratio of O2 supply to O2 consumption was not significantly altered by ansa subclavia stimulation, indicating that sympathetic stimulation produced no adverse effect in either region.

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