Acid-Base Lab Questions Flashcards
What is the direction of change in the parameters below during respiratory acidosis?
during:
aHCO3– : Generation and Compensation
stHCO3– : Generation and Compensation
BE: Generation and Compensation
Respiratory Acidosis
- aHCO3– Generation [↑]: Respiration↓→pCO2↑→H2CO3 right shift
- aHCO3– Compensation [↑↑]: H2CO3 right shift +PCT reabsorption↑
- stHCO3– Generation [unchanged]: Only Metabolism dependent
- stHCO3– Compensation [↑]: PCT reabsorption↑
- BE Generation [unchanged]: No Metabolic Base Deficit/Excess
- BE Compensation [positive]: PCT reabsorption↑
*Renal Compensation will start after 8~ Hrs - Synthesis of PCT proteins.
Diabetic ketoacidosis. How and why do the indicated parameters deviate from normal?
pH, pCO2, BE, aHCO3–, st HCO3–, AG, se K+
Diabetic Ketoacidosis
- pH [↓]: Worsen if uncompensated by lung/kidney or untrearted.
- pCO2 [↓]: As ventilation increases, in DKA:Kussmal Breaths.
- BE [↓]: less negative as renal bicarbonate reabsorption increases.
- aHCO3–[**↓**]: Depletion by Ketosis, renal compensations slows it.
- st HCO3–[**↓**]: Depletion by Ketosis, renal compensations slows it.
- AG[↑]: Ketones releasing H+, become Anions!
- se K+[↑]: Insulin↓ → Na+/K+ Pumps↓, also, Acidosis → H+/K+↑
*Not an official Lab question*
What are the steps to elvauate acid-base disorders?
Five steps to evaluate acid base disorder:
- Did pH change? How? - Acidemia/Alkalemia
- Did pCO2 or St.HCO3- change? Respiratory/Metabolic
- Anion Gap? (Can prove metabolic source: AG/Non-AG acidosis)
- Winter’s Formula? (Additional respiratory derangment to metabolic problem), ExpectedpCO2 = (1.5 x HCO3-)+8 (+/-2) .
- Corrected Bicarbonate (Additional metabolic derangment?) CorrectedHCO3− =aHCO3 + (AG -12).
*Not an official Lab question*
What is the ROME mneumonic?
ROME
- Respiratory Opposite: pCO2 and pH change the oppsite way!
- Metabolic Equal: st.Bicarbonate and pH change the same way!
Traumatic Shock:
- One day after the trauma symptoms of shock-lung develop.
- Identify the type and analyze the different stages of the acid-base imbalance!
- Based on the parameters:
Traumatic Shock:
- First two hours: Acidemia (pH↓), Metabolic Origin (HCO3-↓), BB depleted and low and BE is strongly negative, pCO2 is low - Winters Formula shows normal respiratory compensation:
ExpectedpCO2 = (1.5 x HCO3-)+8 (+/-2) , (pCO2 =~pH last 2 digits)
- One day later: Acidemia (pH↓),Mixed Acidosis - HCO3-↓ + pCO2 is higher than Expected, Would lead to Hyperkalemia!
A 35-year-old woman reports to the ED with shortness of breath. She has cyanosis of the lips. She has had a productive cough for 2 weeks. Her temperature is 39 oC, blood pressure 110/76 mmHg, heart rate 108 bpm, respirations 32/min, rapid and shallow.
Breath sounds are diminished in both bases, with coarse bronchi in the upper lobes. Her ABG results are:
pH=7.44, pCO2=28 mmHg, aHCO3−=18 mmol/l, stHCO3− = 20 mmol/l,
AG = 12 mmol/l, pO2 = 54 mmHg
How do you interpret her ABG result? What other test would you order to verify your diagnosis?
Hypoxic Respiratory Failure leading to disorders:
- Respiratory Alkalosis: pH~↑, pCO2↓, pO2↓, Winter’s Formula: ExpectedpCO2 = 1.5x18+8 = 35mmHg → pCO2 < ExpectedpCO2!
- Metabolic Acidosis: aHCO3−↓, stHCO3−↓, AG is normal→Hyperchloremic Acidosis ,Corrected Bicarbonate <22mmHg
- Tests: Xray, Culture, ESR, CRP, WBC count
A 23 year-old woman with exacerbated rheumatoid arthritis enters to the ED. She has frequently vomited lately.
Her medication: Aspirin 3–5 pills/day. Her ABG result:
pH = 7.70, pCO2 = 25 mmHg, aHCO3− = 30 mmol/l, AG = 22 mmol/l
(Calculated pCO2 = 42–44 mmHg.)
What kind of acid-base disorders does she have?
Salicylate Poisining
- Aspirin↑ can causes hyperventilation.
- Respiratory Alkalosis: Hypocapnia (ExpectedpCO2 is higher)
- Vomiting causes loss of Acids.
- Primary Metabolic Acidosis: AG↑ - Aspirin↑ is an Acid→Anion.
- Additional Metabolic Alkalosis: Bicarbonate↑ (lower than corrected)
A 60-year-old male presents to the ED from a nursing home. He has been breathing rapidly and is less responsive than usual. There is nothing else remarkable in the anamnestic data. His serum electrolyte panel and ABG:
Na+ = 123 mmol/l, K+ = 3.9 mmol/l, Cl− = 99 mmol/l
pH = 7.31, pCO2 = 10 mmHg, aHCO3− = 5 mmol/l
(Calculated pCO2 = 13.5–17.5 mmHg)
What kind of acid-base disorders does he have?
- Hyponatremia
- Primary Anion Gap Metabolic Acidosis: AG↑ (19mM) + aHCO3-↓
- Respiratory Alkalosis: Expected pCO2 >actual pCO2 (Hyperventilation)
- Co-Existing Metabolic Acidosis: Corrected Bicarb<22mM
- Could be cause of Addison’s Disease..
A 42 year-old type 1 DM female has flu for four days with incessant vomiting. She presents to the ED two days after stopping insulin due to no food intake. Her serum electrolyte panel and ABG:
Na+ = 130 mmol/l, K+ = 5.5 mmol/l, Cl− = 80 mmol/l, glucose = 15 mmol/l, pH = 7.21, pCO2 = 25 mmHg, aHCO3− = 10 mmol/l.
(Calculated pCO2 = 21–25 mmHg)
What kind of acid-base disorders does she have?
- DKA Metabolic Acidosis: aHCO3−↓, Ketones↑
- Normal Respiratory Compensation: pCO2 as expected
- AG = 130 - (10+80) = 40
- Corrected Bicarconate = 10 + (40-12) = 38
- Additional Metabolic Alkalosis:CorrectedaHCO3− > 26mM, from Vomiting!
- Hyperkalemia, Hypochloremia, Hyperglycemia
A 30-year-old female bone marrow transplanted patient with neutropenic fever has been receiving multiple antibiotics including amphotericin B. She developed rigors and dyspnea.Her serum electrolyte panel and ABG:
Na+ = 125 mmol/l, K+ = 2.5 mmol/l, Cl− = 100 mmol/l,
pH = 7.07, pCO2 = 28 mmHg, aHCO3− = 8 mmol/l.
(Calculated pCO2 = 18–22 mmHg.)
What kind of acid-base disorders does she have?
- Primary AG Metabolic Acidosis: aHCO3↓, AG= 125-100-8=17→AG↑
- Additional Respiratory Acidosis: pCO2>Expected
- Corrected Bicarbonate= 8 + (17-12) = 13
- Additional Metabolic Acidosis:<strong>Corrected</strong>aHCO3< 22mM
*Immunocomp. state → Fungal Infection → Ampho-B Nephrotoxicity→ RTA → Failed Respiratory Compensation (infection) → rigors and dyspnea
