ICU必备课件1 PPT课件.ppt

CO2 Expected
CO2 Less Abnormal
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Acidosis
Compensated Metabolic Acidosis
Compensated Respiratory Acidosis
Respiratory Acidosis
Mixed Respiratory Metabolic
blood HCO3 which results in availability of renal tubular HCO3 for H+ excretion
pH < 7.Biblioteka Baidu5 HCO3 < 22
Causes of Metabolic Acidosis
renal failure diabetic ketoacidosis lactic acidosis excessive diarrhea cardiac arrest
Respiratory acidosis metabolic alkalosis
Respiratory alkalosis metabolic acidosis
In respiratory conditions, therefore, the kidneys will attempt to compensate and visa versa.
Buffers
There are two buffers that work in pairs
H2CO3 Carbonic acid
NaHCO3 base bicarbonate
These buffers are linked to the respiratory and renal compensatory system
Respiratory Alkalosis
Mixed Respiratory Metabolic
Alkalosis
CO2 Change opposes
Abnormality
Compensated Metabolic Alkalosis
Respiratory Acidosis
pH 7.30 PaCO2 60 HCO3 26
Causes of Respiratory Acidosis
emphysema drug overdose narcosis respiratory arrest airway obstruction
Metabolic Acidosis
failure of kidney function
Respiratory Alkalosis
pH 7.50 PaCO2 30 HCO3 22
Metabolic Acidosis
pH 7.30 PaCO2 40 HCO3 15
Metabolic Alkalosis
pH 7.50 PCO2 40 HCO3 30
What are the compensations?
Metabolic Component
Function of the kidneys
base bicarbonate Na HCO3 Process of kidneys excreting H+ into the urine and reabsorbing
HCO3- into the blood from the renal tubules 1) active exchange Na+ for H+ between the tubular cells and glomerular filtrate 2) carbonic anhydrase is an enzyme that accelerates hydration/dehydration CO2 in renal epithelial cells
Acidosis
ABG Interpretation
Alkalosis
CO2 Change c/w
Abnormality
CO2 Normal
CO2 More Abnormal
CO2 Expected
CO2 Less Abnormal
Metabolic Alkalosis
Compensated Respiratory Alkalosis
What Is An ABG?
pH [H+]
PCO2 Partial pressure CO2 PO2 Partial pressure O2 HCO3 Bicarbonate BE Base excess
SaO2 Oxygen Saturation
Acid/Base Relationship
This relationship is critical for homeostasis Significant deviations from normal pH ranges are
Respiratory Alkalosis
too much CO2 exhaled (hyperventilation) PCO2, H2CO3 insufficiency = pH pH > 7.45 PCO2 < 35
Causes of Respiratory Alkalosis
hyperventilation panic d/o pain pregnancy acute anemia salicylate overdose
Metabolic Alkalosis
plasma bicarbonate pH > 7.45 HCO3 > 26
What is an ABG
Arterial Blood Gas Drawn from artery- radial, brachial, femoral It is an invasive procedure. Caution must be taken with patient on anticoagulants. Helps differentiate oxygen deficiencies from primary ventilatory deficiencies from primary metabolic acid-base abnormalities
Four-step ABG Interpretation
Step 4:
Determine if there is a compensatory mechanism working to try to correct the pH.
ie: if have primary respiratory acidosis will have increased PaCO2 and decreased pH. Compensation occurs when the kidneys retain HCO3.
ABG INTERPRETATION
Debbie Sander PAS-II
Objectives
What’s an ABG? Understanding Acid/Base Relationship General approach to ABG Interpretation Clinical causes Abnormal ABG’s Case studies Take home
Acidosis
pH < 7.35 PCO2 > 45 HCO3 < 22
Alkalosis
pH > 7.45 PCO2 < 35 HCO3 > 26
Respiratory Acidosis
Think of CO2 as an acid failure of the lungs to exhale adequate CO2 pH < 7.35 PCO2 > 45 CO2 + H2CO3 pH
Four-step ABG Interpretation
Step 1: Examine PaO2 & SaO2 Determine oxygen status Low PaO2 (<80 mmHg) & SaO2 means hypoxia NL/elevated oxygen means adequate oxygenation
~ PaCO2 – pH Relationship
80
7.20
60
7.30
40
7.40
30
7.50
20
7.60
ABG Interpretation
Acidosis
CO2 Change c/w
Abnormality
CO2 Normal
CO2 Change opposes
Abnormality
CO2 More Abnormal
Case Study No. 2
60 y/o male comes ER c/o SOB. Tachypneic, tachycardic, diaphoretic and Cyanotic. Dx acute resp. failure and ABG’s Show PaCO2 very high, low pH and PaO2 is moderately low. The blood gas document Resp. failure due to primarily ventilatory insufficiency.
Respiratory Component
function of the lungs
Carbonic acid H2CO3 Approximately 98% normal metabolites are in the form
of CO2 CO2 + H2O H2CO3
excess CO2 exhaled by the lungs
Four-step ABG Interpretation
Step 2: pH
acidosis alkalosis
<7.35 >7.45
Four-step ABG Interpretation
Step 3: study PaCO2 & HCO 3 respiratory irregularity if PaCO2 abnl & HCO3 NL metabolic irregularity if HCO3 abnl & PaCO2 NL
Causes of Metabolic Alkalosis
loss acid from stomach or kidney hypokalemia excessive alkali intake
How to Analyze an ABG
1. PO2
NL = 80 – 100 mmHg
Acid/Base Relationship
H2O + CO2 H2CO3 HCO3 + H+
Normal ABG values
pH PCO2 PO2 HCO3 BE SaO2
7.35 – 7.45 35 – 45 mmHg 80 – 100 mmHg 22 – 26 mmol/L -2 - +2 >95%
poorly tolerated and may be life threatening Achieved by Respiratory and Renal systems
Case Study No. 1
60 y/o male comes ER c/o SOB. Tachypneic, tachycardic, diaphoretic and Cyanotic. Dx acute resp. failure and ABG’s Show PaCO2 well below nl, pH above nl, PaO2 is very low. The blood gas document Resp. failure due to primary O2 problem.
2. pH
NL = 7.35 – 7.45 Acidotic <7.35 Alkalotic >7.45
3. PCO2
NL = 35 – 45 mmHg Acidotic >45 Alkalotic <35
4. HCO3
NL = 22 – 26 mmol/L Acidotic < 22 Alkalotic > 26