Upload
cora-holmes
View
228
Download
6
Embed Size (px)
Citation preview
ABG CASE STUDIES & INTERPRETATION
Dr. Saidunnisa M.D.,Associate Professor in
Biochemistry
It’s not magic understanding ABG’s, it just
takes a little practice!
Acid base imbalances
• Metabolic acidosis• Metabolic alkalosis • Respiratory acidosis• Respiratory alkalosis
Metabolic• METABOLIC ACIDOSIS: Decrease the HCO3
- --> the pH goes down.
• Compensation: Respiratory Alkalosis (hyperventilation) will bring the pH back near normal. Hyperkalemia (K+ increased)
• Causes: Diarrhea, DKA, LA, renal failure.• METABOLIC ALKALOSIS: Increase the HCO3
- --> the pH goes up.
• Compensation: Respiratory Acidosis (hypoventilation) can help to bring the pH back near normal.Hypokalemia (K+ decreased)
METABOLIC ALKALOSIS
– CAUSES: • Vomiting: Lose enough stomach acid to produce
alkalosis. • Diuretics: Loop diuretics and thiazides can lead to
hypokalemia ------> secondary metabolic alkalosis.• Antacids overuse
ANION GAP• Essentially, the difference between the
concentrations of cations (Na+ primarily +k+) and anions (Cl-, HCO3
-) in the blood.
• High Anion Gap: Metabolic Acidosis. It indicates that you have added acids to the blood: salicylic acid, formic acid, lactic acid, oxalic acid, sulfuric acid.
• Normal Anion Gap: Respiratory Acidosis. It occurs when you ultimately become acidotic because of losing HCO3
-.
Causes of anion gap metabolic acidosis
• Methanol• Uremia• Diabetic ketoacidosis• Paraldehyde• Isopropyl alcohol
• Lactic acidosis• Ethylene glycol• Salicylates• Rhabdomyolysis
The Delta/Delta: AG/ HC03
• Rationale: For each unit INCREASE in AG (above
normal), HC03 should DECREASE one unit (below normal)
• “Normal” values: AG = 18, HC03 = 24
Respiratory
• RESPIRATORY ACIDOSIS: Increase the PCO2---> the pH goes down. Hypoventilation. Compensation: Metabolic Alkalosis can help bring the pH back near normal.
• Causes: pneumonia, Bronchitis, Asthma, COPD.
• RESPIRATORY ALKALOSIS:Decrease the PCO2-> the pH goes up. Hyperventilation. Compensation: Metabolic Acidosis can help bring the pH back near normal.
RESPIRATORY ALKALOSIS
• Causes: • High altitude.
• Neuromuscular disease
• Respiratory center depression
• Inadequate mechanical ventilation
• Sepsis
• Burns
ABG DisordersDisorderDisorder ChangeChange CompensatioCompensatio
nn
Respiratory Respiratory AcidosisAcidosis
Pa COPa CO22 HCOHCO3 3
(Metabolic alkalosis)(Metabolic alkalosis)
Respiratory Respiratory AlkalosisAlkalosis
Pa COPa CO22 HCOHCO3 3
(Metabolic acidosis)(Metabolic acidosis)
Metabolic Metabolic AcidosisAcidosis
HCOHCO3 3 Pa COPa CO22
(Respiratory alkalosis)(Respiratory alkalosis)
Metabolic Metabolic AlkalosisAlkalosis
HCOHCO33 Pa COPa CO2 2
(Respiratory acidosis)(Respiratory acidosis)
Metabolic acidosis
Metabolic acidosis• Metabolic acidosis: Is caused by a decrease in
HCO3- concentration in blood.• Causes: 1. Increased production of acids: LA, kA, Salicylate
poisoning.2.Loss of HCO3-: Via GIT eg Diarrhea and kidneys RTA.3.Blood profile: pH decreased [HCO3-] decreased Pco2 decreased
• Buffering: Excess acids are buffered in both ECF and ICF.
• In ECF buffered primarily by HCO3- thus decreasing the [HCO3-] and causing decrease in pH predicted by H-H equation.
• In ICF excess acids are buffered by organic phosphate and proteins usually H+ is for exchanged K+ causing hyperkalemia.
• Compensation: • Respiratory compensation: decrease in pH
stimulates respiratory center causing hyperventilation which produces decrease in PCO2.
• Renal Compensation: excess H+ is excreted as titratable acid and NH4+.
• Treatment: lactate containing solution which converts HCO3- ion the liver.
Assessment of acid base status
• Direct arterial blood measurements: ABG pH
pCO2
pO2
• Derived measures: Bicarbonate (HCO3
-) Normal Values: pH =7.35-7.45 (7.4)
HCO3-=22 - 26mEq / L (24mEq / L)pCO2 = 35 - 45mm Hg (40mm Hg )Anion Gap: 14-18 (18)
NB: use heparinised blood, measured within 10 minutes
Metabolic alkalosis
Respiratory acidosis
Respiratory Alkalosis
Metabolic Acidosis
pH 7.30
PaCO2 40
HCO3 15
Metabolic Alkalosis
pH 7.50
PCO2 40
HCO3 30
Respiratory Acidosis
pH 7.30
PaCO2 60
HCO3 26
Respiratory Alkalosis
pH 7.50
PaCO2 30
HCO3 22
What are the compensations?
• Respiratory acidosis metabolic alkalosis
• Respiratory alkalosis metabolic acidosis
• In respiratory conditions, therefore, the kidneys will attempt to compensate and visa versa.
• In chronic respiratory acidosis (COPD) the kidneys increase the elimination of H+ and absorb more HCO3. The ABG will Show NL pH, CO2 and HCO3.
• Buffers kick in within minutes. • Respiratory compensation is rapid
and starts within minutes and complete within 24 hours. Kidney compensation takes hours and up to 5 days.
Acid base disorder-worksheet
Practice ABG’s
Answers to Practice ABG’s
1. Respiratory alkalosis2. Respiratory acidosis3. Metabolic acidosis4.Compensated Respiratory acidosis5. Metabolic alkalosis6. Compensated
Respiratory acidosis
7.Compensated Metabolic alkalosis8. Metabolic acidosis9. Respiratory acidosis10. Metabolic alkalosis
Work sheet
• Diarrhea may lead to----------?• Acid loss due to vomiting and gastric
suction may lead to ____ alkalosis?• Overuse of ____ may lead to
metabolic alkalosis?
STEPS OF ASSESSING ABG
• STEP 1: Diagnose whether it is acidosis or alkalosis- (pH will help)
• STEP 2: Diagnose whether it is metabolic or respiratory(Look at the value of bicarbonate and pCO2)
• STEP3:Diagnose whether compensated or non compensated
STEPS OF ASSESSING ABG
• STEP4: Diagnose whether AG is normal or elevated(apply the formula) [Na+ + K+] + [cl- + HCO3
-]
• STEP 5: Diagnosis Always confirm with possible cause by
reading the history
PROBLEMS FOR DISCUSSION
Problem#1
• 67 year female known diabetic for past 20years presented with sudden onset of severe chest pain and Shortness of breath.
• ABG analysis showed:• pH 7.36
• PCO233 mmHg
• HCO318 mmol/L
• Discuss the probable diagnosis.
Problem #2 A 30-year old man with DM presents with H/O polyuria,
polydipsia, fever, cough, and purulent sputum.
His ABG shows the following Na+140 / Cl- 104 K+7.0 pH: 6.95 pCO2 : 33 Hco3 : 7.0Discuss the probable diagnosis.
Problem#3• 45 year old male was admitted to the emergency
room with complaints of mild vomiting, associated with disorientation and muscular weakness. His blood investigations showed the following
pH =7.20 Na -137meq/lHCO3-=16mEq / L Cl-108meq/lpCO2 = 34mm Hg K -5.8 meq/lGlucose =685mg/dl urea -49 mg/dl
Discuss the probable diagnosis.
Problem #4
• 60 year male presents to the ED from a nursing home. You have no history other than he has been breathing rapidly and is less responsive than usual.
• Na+ 123 Cl- 99 HCO3- 5
• pH 7.31 pCO2 10
• Discuss the probable diagnosis.
Problem # 5 60year old man was admitted with severe abdominal pain,
which started some 2 hours back. Clinically he was in a state of shock with distended abdomen.
Femoral pulses could not be palpable
His ABG shows the follows
pH : 7.05 pCO2: 26.3 mmHg HCO3: 7 mmol/LDiscuss the probable diagnosis.
Problem #6
Young woman was admitted with history of head injury There was Fracture skull along with cerebral injury The Respiratory rate 38/min 3 days later her ABG was:
pH: 7.44 pCO2 : 29.3 mmHg HCO3: 19 mmol/LDiscuss the probable diagnosis.
Problem# 7 A 58-year old man with cirrhosis and Type II DM
presents with fever, abdominal pain and vomiting. His ABG shows the following
Na+149 /K+ 3.0 pH 7.31 Cl- 112/ HCO3
- 12 pCO2 19 Discuss the probable diagnosis.
Any Questions?
Problem-8
• A women who had been vomiting for 3 days was taken to the emergency department, where the following blood values were measured:
• pH: 7.5• Pco2: 48 mm of Hg
• HCo3-: 37meq/l
• What acid base disorder she have? Does she have a simple or a mixed acid base disorder?
Problem-9• A 56 year old woman has a 15 year history of type-I DM. A
recent viral infection results in loss of appetite, fever, and vomiting. Physical examination reveals her mucous membranes are dry and she has decreased skin turgor. She is breathing deeply and rapidly. A urine sample contains glucose and ketones.
• ABG analysis:• pH: 7.07 Na+: 132meq/l, k+ : 5.9meq/l cl-: 94• Pco2: 18 mm of Hg
• HCo3-: 5meq/l
• What acid base disorder she have? Does she have a simple or a mixed acid base disorder?
Problem-10• A 35 year old man is admitted to the hospital for
evaluation of severe epigastric pain. For several days prior to admission he had persistent nausea and vomiting. The following blood values are obtained:
• pH: 7.53 Na+: 137meq/l, k+ : 2.8meq/l cl-: 82• Pco2: 45 mm of Hg
• HCo3-: 37meq/l
• What acid base disorder she have? Does she have a simple or a mixed acid base disorder?
Problem-11• A 68 year old man has smoked three packs of
cigarettes per day for 40 years. He had frequent episodes of asthmatic bronchitis. The following blood values are obtained:
• pH: 7.29 Na+: 139meq/l, Cl-: 95meq/l• Pco2: 70 mm of Hg
• HCo3-: 33meq/l
• What acid base disorder she have? Does she have a simple or a mixed acid base disorder?
Problem-12
• A patient has the following arterial blood values:
• pH: 7.33• Pco2: 70 mm of Hg
• HCo3-: 36meq/l
• What acid base disorder she have? Does she have a simple or a mixed acid base disorder?