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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
4
|
| pubmed:dateCreated |
1995-11-21
|
| pubmed:abstractText |
The p50 and derived indexes, calculated by using the Siggaard-Andersen algorithm from a single measurement of arterial blood gas tensions and hemoglobin-oxygen saturation, are used to assess tissue oxygen availability in critical illness. We tested the accuracy of the Siggaard-Andersen p50 algorithm over a wide range of pathophysiologic conditions. Blood gases, cooximetry, and calculation of standard and in vivo p50 were performed at multiple saturations, CO2 tensions, and H+ concentrations on blood with normal (standard p50 of 26.1 and 26.7 mm Hg), increased (19.0 and 25.4), and reduced (33.9 and 38.2) hemoglobin-oxygen affinity, as well as on high-affinity blood from two patients with diabetic ketoacidosis (16.7 and 20.8). Log p50 in vivo/pH plots were constructed to determine the Bohr effect. Except in the normal affinity specimens (coefficient of variation < 1.7%), standard p50 values showed high variability (coefficient of variation > 5.9%), with saturation-linked bias and distortion of the Bohr effect. Standard p50 was overestimated by up to 11 mm Hg as saturation approached 97%. Although base deficit correction of the stored specimens (6.9 < pH < 7.1) restored the Bohr effect and improved the accuracy of standard p50 calculations (coefficient of variation = 4.4% and 2.9%), saturation-linked bias persisted. We conclude that Siggaard-Andersen p50 calculations may be misleading when there are disturbances of hemoglobin-oxygen affinity and acid-base balance, owing to changes in shape of the hemoglobin-dissociation curve. When metabolic acidosis occurs with high hemoglobin-oxygen affinity, as can occur in critical illness, indexes derived by the Siggaard-Andersen algorithm on arterial blood may greatly overestimate oxygen availability.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
AIM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Oct
|
| pubmed:issn |
0022-2143
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| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
126
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
365-72
|
| pubmed:dateRevised |
2004-11-17
|
| pubmed:meshHeading |
pubmed-meshheading:7561445-Acid-Base Imbalance,
pubmed-meshheading:7561445-Algorithms,
pubmed-meshheading:7561445-Arteries,
pubmed-meshheading:7561445-Critical Illness,
pubmed-meshheading:7561445-Humans,
pubmed-meshheading:7561445-Hydrogen-Ion Concentration,
pubmed-meshheading:7561445-Models, Biological,
pubmed-meshheading:7561445-Oxygen,
pubmed-meshheading:7561445-Oxyhemoglobins,
pubmed-meshheading:7561445-Protein Binding,
pubmed-meshheading:7561445-Regression Analysis
|
| pubmed:year |
1995
|
| pubmed:articleTitle |
Siggaard-Andersen algorithm-derived p50 parameters: perturbation by abnormal hemoglobin-oxygen affinity and acid-base disturbances.
|
| pubmed:affiliation |
Department of Anesthesiology and Intensive Care, University of Queensland, Royal Brisbane Hospital, Australia.
|
| pubmed:publicationType |
Journal Article
|