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9 Cards in this Set
- Front
- Back
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Why obtain blood gases?
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Assess the oxygenation capacity of the cardiopulmonary system
Assessment of oxygen pressure to guide therapy Assessment of adequacy of ventilation Assessment of acid-base status Assessment of Hb concentration, electrolytes and glucose |
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Oxygen Content in the Blood
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You determine this via summing the diffused oxygen in the blood and the oxygen bound to Hb;
diffused blood is low |
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Weakness of Oxyhemoglobin dissociation curve?
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It assumes that Hb is functioning properly.
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Oxygen delivery to tissues
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Your blood delivers almost 1L/min but tissues only use 270mL/min
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Ways to measure Hg saturation?
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Co oximeter - gold standard, but not practical to be in each OR, measures fractional Hb; limited by # of wavelengths of light, can't detect SulfHb
Pulse oximeter - simple, recorded every 5 minutes, although does not record if Hb is afunctional; measure functional Hb; false high reading w/ pts with CO poisoning and methemoglobin Intravascular - measures functional Hb, Blood Gas machine |
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Carboxyhemoglobin
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CO competes with O2 for binding site
Decreased oxygen delivery Clinical signs: 5% COHb - Impaired visual and temporal discrimination 8% COHb - Alterations in mood and sleep loss of short term memory, mild hypotension, sinus tachacardia, pvc’s 20% COHb - Headache and weakness atrial flutter/fibrillation, T-wave inversion, 40% to 60% COHb - unconsciousness and death (Smokers normal have 2-4%) |
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Methemoglobin
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Fe++ is oxidized to Fe+++
Fe+++ cannot bind O2 One Fe+++ molecule causes the affinity of the other 3 molecules of Fe++ to increase their binding affinity for oxygen - not releasing it to tissue. Oxygen content is reduced Oxygen delivery may be reduced without compensatory increase in cardiac output sources of methhemoglobin Local Anesthetics benzocaines (topical anesthetics) Drugs primaquine (anti-malarial) dapsone (treating Pneumocystis Carinii) nitrites and nitrates (diet or drugs) nitroglycerine sodium nitroprusside Smoke inhalation |
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Clinical signs and symptoms of MethHb
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0.6% - 1.5% MetHb - normal
10% - 15% MetHb - cyanosis is obvious blood is chocolate brown in color 20% - 45% MetHb - dizziness, shortness of breath, fatigue, lethargy, headache and syncope 45% - 55% MetHb - depressed consciousness 55% - 70% MetHb - seizures, coma, dysrhythmias > 70% MetHb - results in Death Blood is chocolate brown Treated w/ Methylene Blue |
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Sulfhemoglobin
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Sulfur atom incorporated into the porphyrin ring
incapable of binding oxygen at that site green pigmentation favors sickling in HbS Decreased oxygen content Decreased oxygen delivery without cardiovascular compensation Mainly found in industrial compounds and some drugs Sign = cyanosis No treatment except transfusion |
