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![SpO2 Vs SaO2 Contd...
• SpO2 == HbO2
HbO2 + Hb
• SaO2 == HbO2
HbO2+ Hb+COHb+MetHb+SfHb+COSfHb
SaO2 == SpO2[1-SaCO]… (Nellcor equation)
Non functional Hb is 2-3%
In heavy smoker it may be up to 15%](https://image.slidesharecdn.com/abgpresentationbydj-171118172053/75/ABG-by-DJ-20-2048.jpg)
![Step 3. For a respiratory disturbance,
determine whether it is acute or chronic.
• Acute respiratory disturbances change pH
0.08 units for every 10 mmHg deviation from
normal.
• Therefore, in acute respiratory acidosis, the
pH will fall by 0.08 x [(PCO2 - 40)/10]
• In acute respiratory alkalosis, the pH will rise
by 0.08 x [(40-PCO2)/10]](https://image.slidesharecdn.com/abgpresentationbydj-171118172053/75/ABG-by-DJ-40-2048.jpg)
![Step 3. Contd…
• Chronic respiratory disturbances only change
pH 0.03 units for every 10 mmHg deviation
from normal
• Therefore, in chronic respiratory acidosis, pH
will fall by 0.03 x [(PCO2 - 40)/10]
• In chronic respiratory alkalosis, the pH will rise
by 0.03 x [(40-PCO2)/10]](https://image.slidesharecdn.com/abgpresentationbydj-171118172053/75/ABG-by-DJ-41-2048.jpg)
![Evaluating Oxygenation in ABGs
• Determine the A-a gradient
• A-a Gradient =
• [(Patm - PH2O) x FiO2] - (PCO2/RQ) - PaO2
• Patm = 760 mmHg
• PH2O = 47 mmHg
• FiO2 = 0.21 on room air at sea level
• PCO2 is taken from the blood gas measurement
• RQ can be assumed to be 1 (possible range
from 0.7 to 1.0)](https://image.slidesharecdn.com/abgpresentationbydj-171118172053/75/ABG-by-DJ-63-2048.jpg)
Uploaded byDharmendra Joshi
ABG by DJ
This document provides an overview of arterial blood gas (ABG) analysis, including: 1. ABG analysis measures oxygen, carbon dioxide, pH, and bicarbonate levels in arterial blood to evaluate respiratory and metabolic function. 2. It is ordered to assess patients with breathing issues, lung disease, or those on oxygen therapy to monitor treatment effectiveness. 3. Normal ABG results include a pH of 7.35-7.45, PaO2 of 80-100 mmHg, PaCO2 of 35-45 mmHg, and bicarbonate of 22-26 mmol/L. Abnormal results can indicate respiratory or metabolic acidosis/alkalosis helping clinicians
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![ARTERIAL BLOOD GAS [ABG] ANALYSIS PURPOSES, PROCEDURES](https://cdn.slidesharecdn.com/ss_thumbnails/arterialbloodga1-250329163652-107ce59f-thumbnail.jpg?width=640&height=640&fit=bounds)
ABG by DJ
- 1. ABG Arterial Blood GasAnalysis (A Basic Approach) Dr. Dharmendra Joshi (DJ) Dr. Basanta Sapkota
- 2. “Life is astruggle, not against sin, not against the Money Power, not against malicious animal magnetism, but against hydrogen ions." - H.L. MENCKEN
- 3. Table of Contents 1.Definition 2. Purpose 3. Information provided by ABG 4. Normal results 5. Why ABG is ordered? 6. Extraction and Analysis 7. Step wise approach to ABG 8. Acid Base Disorders
- 4. Pulse Oximetry ‘The5th Vital Sign’ • Non-invasive • Instantaneous • Ubiquitous • SaO2 < 95% the usual cutoff for normal versus ‘abnormal’ • Limitations: – Patient must have pulse – Detects only significant decreases in PO2 – Does not comment on content
- 5. ABG: Definition: • Bloodgas analysis, also called Arterial Blood Gas (ABG) analysis, is an invasive test which measures the amount of oxygen (O2) and carbon dioxide (CO2) in the blood, as well as the acidity (pH) of the blood.
- 6. Most Dyspneic PatientsDon’t Require ABG Analysis • When cause of dyspnea is established – Asthma, CHF, restrictive lung disease, etc. • When dyspnea is so severe as to warrant immediate mechanical ventilation – The decision to intubate and mechanically ventilate is almost always one based on clinical, not laboratory, grounds.
- 7. Purpose: • Evaluates howeffectively the lungs are delivering O2 to the blood and how efficiently they are eliminating CO2 from it. • Indicates how well the lungs and kidneys are interacting to maintain normal blood pH (acid- base balance). • Assess respiratory disease and other conditions that may affect the lungs, and to manage patients receiving oxygen therapy (respiratory therapy).
- 8. Purpose: Contd… • Providesinformation on kidney function too. • Determine the pH of the blood and the partial pressures of carbon dioxide (PaCO2) and oxygen (PaO2) within it. • Assess the effectiveness of gaseous exchange and ventilation, be it spontaneous or mechanical.
- 9. Purpose: Contd… • Assessmetabolic status of the patient, giving an indication of how they are coping with their illness. • It would therefore seem logical to request an ABG on any patient who is or has the potential to become critically ill. • This includes patients in critical care areas and those on wards who 'trigger' early-warning scoring systems.
- 10. Limitations of ABGs •ABGs measure gas partial pressures (tensions) – Remember: PO2 is not the same as content! A severely anemic patient may have an oxygen content reduced by half while maintaining perfectly acceptable gas exchange and therefore maintaining pO2
- 11. Limitations of ABGs:Contd… • Technical issues – They hurt, – Sampling from a vein by mistake, – Finding an arterial pulse can be difficult in very hypotensive patients, – Complications such as arterial thrombosis are possible, but rare.
- 12. Information provided byABG • PaCO2 • This is the partial pressure of carbon dioxide dissolved within the arterial blood. • It is used to assess the effectiveness of ventilation. A high PaCO2 (respiratory acidosis) indicates underventilation, a low PaCO2 (respiratory alkalosis) indicates hyper- or over ventilation. • The normal range for a healthy person is 4.7-6.0 kPa or 35-45 mmHg although in chronic pulmonary diseases it may be considerably higher and still normal for that patient.
- 13. Information provided byABG Contd... • PaO2 • This is the partial pressure of oxygen dissolved within the arterial blood and will determine oxygen binding to haemoglobin (SaO2). • It is of vital importance but is not used in determining patients' acid base status and normally low readings indicate hypoxaemia. • The normal range: 9.3-13.3 kPa or 80-100 mmHg.
- 14. Information provided byABG Contd... • SaO2 • Oxygen saturation measures how much of the haemoglobin (Hb) in the red blood cells is carrying oxygen (O2). • Although similar to SpO2 (measured by a pulse oximeter), it is more accurate. • The normal levels are 97% and above, although levels above 90% are often acceptable in critically ill patients.
- 15. Information provided byABG Contd... • pH • The pH measures hydrogen ions (H+) in blood. • The pH of blood usually between 7.35 to 7.45. A pH of less than 7.0 is called acid and a pH greater than 7.0 is called basic (alkaline). So blood is slightly basic.
- 16. Information provided byABG Contd... • HCO3 (Bicarbonate) • HCO3 is a chemical (buffer) that keeps the pH of blood from becoming too acidic or too basic & indicates whether a metabolic problem is present (such as ketoacidosis). • A low HCO3 - indicates metabolic acidosis, a high HCO3 - indicates metabolic alkalosis. • HCO3 - levels can also become abnormal when the kidneys are working to compensate for a respiratory issue so as to normalize the blood pH • Normal range: 22–26 mmol/l
- 17. Information provided byABG Contd... • Base Excess (BE) • The base excess is used for the assessment of the metabolic component of acid-base disorders, and indicates whether the patient has metabolic acidosis or metabolic alkalosis. • A negative base excess indicates that the patient has metabolic acidosis (primary or secondary to respiratory alkalosis). • A positive base excess indicates that the patient has metabolic alkalosis (primary or secondary to respiratory acidosis). • Normal range: -3 to +3 mmol/l
- 18. Information provided byABG Contd... • Other informations: • Some electrolytes (e.g., Na+, K+, Ca++) • Lactate • Other assorted calculated results.
- 19. SpO2 SaO2 • SpO2and SaO2 are often used interchangeably, but they are not same. • When O2 saturation is measured by pulse oximeter..... SpO2 • When O2 saturation is measured by CO- oximeter..... SaO2 • SpO2 is also called functional arterial O2 saturation and SaO2 as fractional arterial O2 saturation. • Only true CO-oximeter can determine an accurate value for SaO2
- 20. SpO2 Vs SaO2Contd... • SpO2 == HbO2 HbO2 + Hb • SaO2 == HbO2 HbO2+ Hb+COHb+MetHb+SfHb+COSfHb SaO2 == SpO2[1-SaCO]… (Nellcor equation) Non functional Hb is 2-3% In heavy smoker it may be up to 15%
- 21. Normal Results • pH:Measurement of acidity or alkalinity, based on the hydrogen (H+) 7.35-7.45 • partial pressure of oxygen (PaO2): The partial pressure oxygen that is dissolved in arterial blood. 80-100 mm Hg
- 22. Normal Results Contd… •partial pressure of carbon dioxide (PaCO2): The amount of carbon dioxide dissolved in arterial blood. 35-45 mm Hg • oxygen content (O2CT): 15-23% • oxygen saturation (SaO2): The arterial oxygen saturation. 94-100%
- 23. Normal Results Contd… •Bicarbonate (HCO3 -): The calculated value of the amount of bicarbonate in the blood. 22-26 mEq/L • The base excess indicates the amount of excess or insufficient level of bicarbonate. -2 to +2mEq/L (A negative base excess indicates a base deficit in blood)
- 24. Why ABG isordered? • Blood gas tests are ordered for patients with symptoms of an O2/CO2 or pH imbalance, such as difficulty breathing or shortness of breath & also if known to have a respiratory, metabolic, or kidney disease or experiencing respiratory distress to evaluate oxygenation and acid/base balance. • Patients who are “on oxygen” (have supplemental oxygen) may have their blood gases measured at intervals to monitor the effectiveness of treatment.
- 25. Why ABG isordered? Contd... • Head or neck trauma, injuries that may affect breathing. • Prolonged anesthesia – particularly for cardiac bypass surgery or brain surgery – during and for a period after the procedure.
- 26. Buffers • There aretwo buffers that work in pairs: H2CO3 NaHCO3 Carbonic acid base bicarbonate • These buffers are linked to the respiratory and renal compensatory system.
- 27. Respiratory Buffer Response •H2CO3 level • Blood pH • Rate & depth of ventilation (Lungs) • Activation of the lungs to compensate for an imbalance starts to occur within 1-3 minutes
- 28. Renal Buffer Response •The kidneys excrete or retain bicarbonate(HCO3 -). • If blood pH decreases, the kidneys will compensate by retaining HCO3 - • Renal system may take from hours to days to correct the imbalance.
- 29. Extraction • Usually extractedby a phlebotomist, nurse, respiratory therapist or Doctor. • Commonly from the radial artery because: - it is easily accessible, - can be compressed to control bleeding, - has less risk for occlusion.
- 30. Extraction Contd... • Thefemoral artery (or less often, the brachial artery) is also used, especially during emergency situations or with children. • Blood can also be taken from an arterial catheter already placed in one of these arteries.
- 31. Extraction and analysis: •IF ULNER/RADIAL ARTERY IS USED ---MODIFIED ALLEN’S TEST • MODIFIED ALLEN’S TEST 1. INSTRUCT PATIENT TO CLENCH HIS FIST, 2. USING YOUR FINGER APPLY OCCLUSIVE PRESSURE ON BOTH RADIAL & ULNER ARTERY, 3. WHILE APPLYING OCCLUSIVE PRESSURE TO BOTH ARTERY, HAVE THE PATIENT RELAX HIS HAND.BLANCHING OF PALM &FINGER SHOULD OCCUR,
- 32. MODIFIED ALLEN’S TESTContd… 4. RELEASE THE OCCLUSIVE PRESSURE ON ULNER ARTERY & NOTICE FLUSHING OF HAND WITHIN 7-10 SEC.THIS DENOTE THAT ULNER ARTERY SUPPLY IS ADEQUATE &IT’S SAFE TO PRICK RADIAL ARTERY. IF IT DOES NOT OCCUR IT MEANS ULNAR ARTERY SUPPLY IS NOT SUFFICIENT & RADIAL ARTERY IS NOT SAFE TO PRICK.
- 33. Extraction and analysis:Contd... 1. The syringe is pre-packaged and contains a small amount of heparin, to prevent coagulation or needs to be heparinised, by drawing up a small amount of heparin and squirting it out again. 2. Once the sample is obtained, care is taken to eliminate visible gas bubbles, as these bubbles can dissolve into the sample and cause inaccurate results.
- 34. Extraction and analysis:Contd... 3. The sealed syringe is taken to a blood gas analyzer. If the sample cannot be immediately analyzed, it is chilled in an ice bath in a glass syringe to slow metabolic processes which can cause inaccuracy. 4. Samples drawn in plastic syringes should not be iced and should always be analyzed within 30 minutes. 5. The machine used for analysis aspirates this blood from the syringe and measures the pH and the partial pressures of oxygen and carbon dioxide. The bicarbonate concentration is also calculated.
- 35. Extraction and analysis:Contd... 6. Results usually available for interpretation within five minutes. 7. After the blood has been taken, apply pressure to the puncture site for 10-15 minutes to stop the bleeding, and then places a dressing over the puncture. 8. Observe the patient for signs of bleeding or circulation problems.
- 36. Contraindication for arterialpuncture I. INFECTION AT SITE. II. ALLEN’S TEST NEGATIVE. III. ON ANTICOAGULANT THERAPY. IV. SEVERE PERIPHERAL VASCULAR DISEASE. V. DISTAL TO SURGICAL SHUNT.
- 37. Step wise approachto ABG • Step 1: Acidemic or Alkalemic? • Step 2: Is the primary disturbance respiratory or metabolic? • Step 3. Asses to PaO2. A value below 80mm Hg indicates Hypoxemia. For a respiratory disturbance, determine whether it is acute or chronic. • Step 4. For a metabolic acidosis, determine whether an anion gap is present. • Step 5. Determine if there is compensatory mechanism working to correct pH
- 38. Step 1: Acidemicor Alkalemic? • Assess the pH –acidotic/alkalotic • If above 7.5 – alkalotic • If below 7.35 – acidotic
- 39. Step 2: Isthe primary disturbance respiratory or metabolic? • Assess the paCO2 level. • pH decreases below 7.35, the paCO2 should rise. • If pH rises above 7.45 paCO2 should fall. • If pH and paCO2 moves in opposite direction – primary respiratory problem. • Assess HCO3 value. • If pH increases the HCO3 should also increase. • If pH decreases HCO3 should also decrease. • They are moving in the same direction, primary problem is metabolic.
- 40. Step 3. Fora respiratory disturbance, determine whether it is acute or chronic. • Acute respiratory disturbances change pH 0.08 units for every 10 mmHg deviation from normal. • Therefore, in acute respiratory acidosis, the pH will fall by 0.08 x [(PCO2 - 40)/10] • In acute respiratory alkalosis, the pH will rise by 0.08 x [(40-PCO2)/10]
- 41. Step 3. Contd… •Chronic respiratory disturbances only change pH 0.03 units for every 10 mmHg deviation from normal • Therefore, in chronic respiratory acidosis, pH will fall by 0.03 x [(PCO2 - 40)/10] • In chronic respiratory alkalosis, the pH will rise by 0.03 x [(40-PCO2)/10]
- 42. Appropriateness of Respiratory Responseto Metabolic Acidosis • Predicted Change in PCO2 = (1.5 x HCO3) + 8 (+-2) • If patient’s PCO2 is roughly this value, his or her response is appropriate. • If patient’s PCO2 is higher than this value, they are failing to compensate adequately.
- 43.
- 44. Base Excess • Isa calculated value estimates the metabolic component of an acid based abnormality. • It is an estimate of the amount of strong acid or base needed to correct the metabolic component of an acid base disorder (restore plasma pH to 7.40 at a PaCO2 40 mmHg)
- 45. Formula • With thebase excess is 10 in a 50kg person with metabolic acidosis mM of HCO3 needed for correction is: = 0.3 X body weight X BE = 0.3 X 50 X10 = 150 mM
- 46. Step 4. Fora metabolic acidosis: Anion Gap Determination • Calculation of AG is useful approach to analyze metabolic acidosis • AG = (Na+ + K+) – (Cl- + HCO3 -) • It represents the unmeasured anion in plasma. • Normal value: 10-12mmol/l
- 47. REMEMBER High Anion Gap– causes: • K etoacidosis • U remia • S epsis • S alicylate & other drugs • M ethanol • A lcohol (Ethanol) • L actic acidosis • E thylene glycol
- 48.
- 49. Reduced anion gap •Increased ‘unmeasured’ cations • Rare • Hypermagnesaemia • Lithium toxicity • Xs protein – Myeloma – Waldenstrom’s macroglobulinaemia – (Ig’s are strong cations)
- 50. Normal anion gap •Disorders of bicarbonate homeostasis • Hyperchloraemia causes the acidosis • GI losses – Vomitting – Diarrhoea • Renal losses – Renal tubular acidosis – Acetazolamide • Iatrogenic NaCl
- 51. Step 5. Determineif there is compensatory mechanism working to correct pH • Primary respiratory disturbances i.e primary changes in PaCO2 invoke compensatory metabolic responses i.e Secondary changes in HCO3 and vice versa. • A patient can be uncompensated or partially compensated or fully compensated, • pH has returned within normal range- fully compensated though other values may be still abnormal,
- 52. Step 5 Contd... •Be aware that neither the system has the ability to overcompensate, • If patient have primary respiratory acidosis will have increased PaCO2 and decreased pH, Compensation occurs when the kidneys retain HCO3. • The body’s attempt to return the acid/base status to normal (i.e. pH closer to 7.4).
- 53. Compensation: • Primary ProblemCompensation • respiratory acidosis metabolic alkalosis • respiratory alkalosis metabolic acidosis • metabolic acidosis respiratory alkalosis • metabolic alkalosis respiratory acidosis
- 54. Is there appropriatecompensation? Is it chronic or acute?
- 55. Respiratory Acidosis – Acute:for every 10 increase in pCO2 -> HCO3 increases by 1 and there is a decrease of 0.08 in pH MEMORIZE – Chronic: for every 10 increase in pCO2 -> HCO3 increases by 4 and there is a decrease of 0.03 in pH
- 56. Respiratory Alkalosis – Acute:for every 10 decrease in pCO2 -> HCO3 decreases by 2 and there is a increase of 0.08 in pH MEMORIZE – Chronic: for every 10 decrease in pCO2 -> HCO3 decreases by 5 and there is a increase of 0.03 in pH
- 57. Assess the PaCO2 •In an uncompensated state – when the pH and PaCO2 moves in the same direction: the primary problem is metabolic. • The decreasing PaCO2 indicates that the lungs acting as a buffer response (blowing of the excess CO2) • If evidence of compensation is present but the pH has not been corrected to within the normal range, this would be described as metabolic disorder with the partial respiratory compensation.
- 58. Assess the HCO3 •The pH and the HCO3 moving in the opposite directions, primary disorder is respiratory and the kidneys acting as a buffer response: are compensating by retaining HCO3 to return the pH to normal range.
- 59. pH PaCO2 HCO3 - Resp.AcidosisNormal but<7.40 Resp.Alkalosis Normal but>7.40 Met. Acidosis Normal but<7.40 Met. Alkalosis Normal but>7.40 Fully Compensated
- 60. Partially Compensated pH PaCO2HCO3 - Res.Acidosis Res.Alkalosis Met. Acidosis Met.Alkalosis
- 61. HOW TO KNOWTHE DISORDER pH PaCO2 HCO3ˉ Respiratory Acidosis Acute < 7.35 > 45 Normal Partly Compensated < 7.35 > 45 > 26 Compensated ~ Normal > 45 > 26 Respiratory Alkalosis Acute > 7.45 < 35 Normal Partly Compensated > 7.45 < 35 < 22 Compensated ~ Normal < 35 < 22 Metabolic Acidosis Acute < 7.35 Normal < 22 Partly Compensated < 7.35 < 35 < 22 Compensated ~ Normal < 35 < 22 Metabolic Alkalosis Acute > 7.45 Normal > 26 Partly Compensated > 7.45 > 45 > 26 Compensated ~ Normal > 45 > 26
- 62. Evaluating Oxygenation • Whatis a ‘normal’ PO2? – Oxygenation gradually deteriorates during life, – Several calculations available for determining ‘normal’ based on patient age. • PaO2 = 104.2 - (0.27 x age) • i.e., 30 year old ~ 95 mmHg 60 year old ~ 88 mmHg • Note: Some patients with previous (and now resolved) severe pulmonary diseases may never recover their full lung function, so any sense of ‘normal’ needs to be tempered with historical information
- 63. Evaluating Oxygenation inABGs • Determine the A-a gradient • A-a Gradient = • [(Patm - PH2O) x FiO2] - (PCO2/RQ) - PaO2 • Patm = 760 mmHg • PH2O = 47 mmHg • FiO2 = 0.21 on room air at sea level • PCO2 is taken from the blood gas measurement • RQ can be assumed to be 1 (possible range from 0.7 to 1.0)
- 64. Evaluating Oxygenation withABGs Check A-a Gradient No Yes Is the patient hypoxic? Hypoventilation Normal Elevated Check A-a Gradient No defect Compensated Defect. i.e., patient is hyper- ventilating or on supplemental O2 Other Defect Normal Elevated
- 65. ~ PaCO2 –pH Relationship 80 7.20 60 7.30 40 7.40 30 7.50 20 7.60
- 66. pH < 7.35 Acidosis pH> 7.45 Alkalosis pCO2 > 45 Respiratory HCO3 < 22 Metabolic pCO2 < 35 Respiratory HCO3 > 26 Metabolic PaCO2 ↑10 →HCO3 ↑3.5 PaCO2 ↑10 →HCO3 ↑1 PaCO2 ↓10 →HCO3 ↓4 PaCO2 ↓10 →HCO3 ↓2 PaCO2 ↑7 →HCO3 ↑10 Urine Cl < 10 Cl ResponsiveAnion Gap < 12 Non-Anion Gap Anion Gap > 12 Anion Gap Urine Cl > 10 Cl Unresponsive Interpreting ABGs Osm Gap > 10 Methanol Ethylene Glycol Osmolar Gap < 10 Ketoacidosis Lactic acidosis Uremia Aspirin/salicylate tox Diarrhea Renal tubular acidosis Acetazolamide Total parenteral nutrition Ureteral diversion Pancreas transplant CNS depressants Neuromuscular disorder Thoracic cage abnormalities Obstructive lung disease Obesity/hypoventilation syndrome Myxedema coma Anxiety/pain Sepsis CNS (stroke) Aspirin OD Chronic liver disease Pulmonary embolism Pregnancy Hyperthyroidism Loss of body fluids: Vomiting Nasogastric suctioning Diuretic use Excess body fluids: Exogenous steroids Cushing’s syndrome Hyperaldosteronism Bartter’s syndrome =Na - (Cl+HCO3) Acute Chronic PaCO2 ↓15 →HCO3 ↓10 Compensation: If: ΔPCO2/ΔHCO3 = CO2/HCO3ratio Then it IS comp. Acute Chronic (2xNa) + (Glu/18) + (BUN/2.8) = calculated serum osmoles HCO3 loss Extra H+
- 67. ABG Vs VBG ArterialBlood Gas • PAINFUL • Arterial injury • Thrombosis with distal ischemia • Hemorrhage/hematoma • Aneurysm formation • Median nerve damage • Infection • Needle stick injury • Reflex sympathetic dystrophy Venous Blood Gas • Samples can be drawn simultaneously at time of veni puncture • Should be done without tourniquette • More difficult to obtain in pulseless patients • Controversy regarding level of agreement with arterial values
- 68. ABG Vs VBG 1.To measure pH, bicarb, or base excess, especially in hemodynamically stable patients, a VBG is equivalent and there is no need for an ABG. On average for pH the difference is about 0.02 - 0.03. So for average DKA patient, no ABG is needed. 2. A VBG is a good screening tool for hypercarbia, with a venous PCO2 < 45 mmHg having about 100% sensitivity. However, VBG cannot tell about the degree of hypercarbia reliably. If an absolute number needed, ABG is the way to go.
- 69. ABG Vs VBGContd... 3. For hypoxia, or workup requiring calculations of oxygen tension, ABG is done (hypoxic arrest, calculating A-a gradients) 4. Studies are raising the concern for increased mortality in patients who have hyperoxia after return of circulation after cardiac arrest. These patients need ABG’s to guide the vent settings. The increased mortality in these patients has even been seen within the first hour.
- 71. Acid Base Disorders 1.Respiratory Acidosis 2. Respiratory Alkalosis 3. Metabolic Acidosis 4. Metabolic Alkalosis
- 72. Respiratory Acidosis • LowerpH and an increased PCO2 and is due to respiratory depression (not enough oxygen in and CO2 out). • pH decrease (<7.35) • PCO2 increase (>45mmHg) • Any condition that results in hypoventilation can cause respiratory acidosis.
- 73. Causes of respiratoryacidosis CNS depression – sedatives, narcotics, CVA Neuromuscular disorders – acute or chronic Acute airway obstruction – foreign body, tumor, reactive airway Severe pneumonia, pulmonary edema, pleural effusion Chest cavity problems – hemothorax, pneumothorax, flail chest Chronic lung disease – obstructive or restrictive Central hypoventilation, OSA
- 74. Respiratory Acidosis: Signs&Symptom •Respiratory : Dyspnoea, respiratory distress and/or shallow respiration. • Nervous: Headache, restlessness and confusion. If co2 level extremely high drowsiness and unresponsiveness may be noted. • CVS: Tacycardia and dysrhythmias
- 75. Management of RespiratoryAcidosis • Increase the ventilation. • Causes can be treated rapidly include pneumothorax, pain and CNS depression r/t medication. • If the cause cannot be readily resolved, mechanical ventilation.
- 76. Respiratory Alkalosis • Respiratoryalkalosis, characterized by a raised pH and a decreased PCO2, is due to over ventilation caused by hyperventilating, pain, emotional distress, or certain lung diseases that interfere with oxygen exchange. • pH increases • PCO2 decreases
- 77. Causes of RespiratoryAlkalosis Anxiety, pain, fever Hypoxia, CHF Lung disease with or without hypoxia – pulmonary embolus, reactive airway, pneumonia CNS diseases Drug use – salicylates, catecholamines, progesterone Pregnancy Sepsis, hypotension Hepatic encephalopathy, liver failure Mechanical ventilation Hypothyroidism High altitude
- 78. Respiratory Alkalosis: Signs/Symptoms • CNS:Light Headedness, numbness, tingling, confusion, inability to concentrate and blurred vision. • Dysrhythmias and palpitations • Dry mouth, diaphoresis and tetanic spasms of the arms and legs.
- 79. Management of RespiratoryAlkalosis • Resolve the underlying problem • Monitor for respiratory muscle fatigue • When the respiratory muscle become exhausted, acute respiratory failure may ensue
- 80. Metabolic Acidosis • Metabolicacidosis is characterized by a lower pH and decreased HCO3 -; the blood is too acidic on a metabolic/kidney level. • Causes include diabetes, shock, and renal failure. • pH decreases (<7.35) • HCO3 decreases (<22mEq/l)
- 81. Causes of MetabolicAcidosis • Renal failure • Diabetic ketoacidosis • Anaerobic metabolism • Starvation • Salicylate intoxication
- 82. Metabolic Acidosis: Signs/Symptoms •CNS: Headache, confusion and restlessness progressing to lethargy, then stupor or coma. • CVS: Dysrhythmias • Kussmaul’s respirations • Warm, flushed skin as well as nausea and vomiting
- 83. Management of MetabolicAcidosis • Treat the cause • Hypoxia of any tissue bed will produce metabolic acids as a result of anaerobic metabolism even if the pao2 is normal • Restore tissue perfusion to the hypoxic tissues • The use of bicarbonate is indicated for known bicarbonate - responsive acidosis such as seen with renal failure
- 84. Metabolic Alkalosis • Metabolicalkalosis is characterized by an elevated pH and increased HCO3 - and is seen in hypokalemia, chronic vomiting (losing acid from the stomach), and sodium bicarbonate overdose. • pH increases (>7.45) • HCO3 - increases (>26mEq/l)
- 85. Causes of MetabolicAlkalosis • Excess of base /loss of acid. • Ingestion of excess antacids, excess use of bicarbonate, or use of lactate in dialysis. • Protracted vomiting, gastric suction, hypchoremia, excess use of diuretics, or high levels of aldesterone.
- 86. Metabolic Alkalosis: Signs/Symptoms •CNS: Dizziness, lethargy disorientation, siezures & coma. • M/S: weakness, muscle twitching, muscle cramps and tetany. • Nausea, vomiting and respiratory depression. • It is difficult to treat.
- 87. Management of MetabolicAlkalosis • Remove factors that sustain HCO3 - reabsorption: Restore plasma volume Restore chloride lost Replace potassium in hypokalaemia Stop diuretics • Treat underlying cause.
- 88. • Valuable informationcan be gained from an ABG as to the patients physiologic condition • Remember that ABG analysis is only part of the patient assessment. • Be systematic with your analysis, start with ABC’s as always and look for hypoxia (which you can usually treat quickly), then follow the five steps. • A quick assessment of patient oxygenation can be achieved with a pulse oximeter which measures SaO2.
- 89. It’s not magicunderstanding ABG’s, it just takes a little practice!
- 90.