Acid-Base Disorders Part 1 (Andelin) Flashcards
72-year-old male with CC of SOB with PMH of COPD.
BP 155/92, RR 28, HR 115, O2 96% on 4 L.
ABG: pH 7.21 pCO2 77 HCO3 30
Respiratory acidosis likely due to COPD exacerbtion
24-year-old with CC of vomiting and confusion with PMH of DM1.
BP 90/55 RR 32 HR 130 O2 100% on RA
ABG: pH 7.18 pCO2 22 HCO3 8
Metabolic acidosis likely due to Diabetic Ketoacidosis
39-year-old male with CC of rapid breathing with PMH of anxiety.
BP 133/85 RR 30 HR 105 O2 100% on RA
ABG: pH 7.55 pCO2 25 HCO3 21
Respiratory alkalosis likely due to a panic attack
81-year-old female with CC of trouble breathing with PMH of CHF. Received furosemide for 3 days.
BP 118/76 RR 14 HR 85 O2 96% on 2L
ABG: pH 7.50 pCO2 48 HCO3 36
Metabolic alkalosis likely due to a loop diuretic
When is it indicated to order an Arterial Blood Gas (ABG)?
Concerned about any acid-base disturbances:
respiratory distress or tachypnea
abnormal serum bicarb
confusion
salicylate overdose/DKA
What is the body’s normal arterial pH?
Arterial pH is maintained between 7.35-7.45
Where is carbonic anhydrase located inside the body?
present in the lung alveoli and renal tubular epithelial cells
What happened to the pH when bicarb is increased?
When bicarb is increased, so is the pH
can lead to alkalosis (think hyperventilation or kidneys compensation)
What happens to pH when PCO2 is increased?
When PCO2 is increased, the pH is decreased.
can lead to acidosis (think hypoventilation - not breathing off the CO2 appropriately or DKA)
How do the lung regulate pH?
by controlling PCO2 concentration
increased RR, increased CO2 blown off, decrease PCO2 in the blood (relieves acidosis, but can lead to alkalosis)
decreased RR, decreased CO2 blown off, increase PCO2 in the blood (relieves alkalosis, but can lead to acidosis)
How do the kidneys regulate pH?
by excreting either acidic or alkaline urine
increased HCO3 excreted, decrease HCO3 in blood, the pH will decrease
increased H+ excreted, decrease H+ in blood, the pH will increase
Normal range for HCO3
24 mEq/L (22-26)
Normal range for PCO2
40 mmHg (35-45)
Low pH and Low HCO3
Metabolic Acidosis (the low HCO3 is causing the low pH) check anion gap; order BMP (Na/Cl/HCO3)
High pH, High HCO3
Metabolic Alkalosis
Low pH, High PCO2
Respiratory Acidosis (the high CO2 is causing the low pH)
High pH, Low PCO2
Respiratory Alkalosis
KCU standard normal anion gap
KCU normal 5-16 mEq/L (need BMP)
Winter’s Formula
Expected compensation formula for Metabolic acidosis:
PCO2 = 1.5[HOC3] + 8 +/- 2
Metabolic Alkalosis compensation formula
For each 1.0 mEq/L increase in HCO3 from normal (24) expect pCO2 increase of 0.7 mmHg (so almost same increase just a little less)
Expected HCO3 compensation for ACUTE respiratory acidosis
Acute Respiratory Acidosis: (caused by pCO2)
For every 10 mmHg increase in pCO2; HCO3 should be increased by 1
Expected HCO3 compensation for ACUTE respiratory alkalosis
Acute Respiratory Alkalosis: (caused by pCO2)
For every 10 mmHg decrease in pCO2; HCO3 should decrease by 2
Expected HCO3 compensation for CHRONIC respiratory acidosis
Chronic Respiratory Acidosis: (caused by pCO2)
For every 10 mmHg increase in pCO2; HCO3 should be increased by 3.5
Expected HCO3 compensation for CHRONIC respiratory alkalosis
Acute Respiratory Alkalosis: (caused by pCO2)
For every 10 mmHg decrease in pCO2; HCO3 should decrease by 5
Metabolic Acidosis symptoms
Results in low pH
Hyperventilation (Kussmaul respirations)
Headache, lethargy, stupor, coma
Causes of metabolic acidosis (3 overview causes)
Increased production/ingestion of acid
Increased loss of bicarbonate
Decreased renal excretion of acid
Pathophysiology of high anion gap metabolic acidosis
HAGMA mostly due to increased production of acid (commonly lactic acid)
Pathophysiology of normal anion gap metabolic acidosis
NAGMA mostly due to loss of bicarbonate or decrease excretion of acid (more acid left in body)
High anion gap metabolic acidosis differential diagnosis
GOLD MARK
G - Glycols
O - Oxoproline (chronic acetaminophen use)
L - L type Lactic acidosis
D - D type Lactic acidosis (short bowel syndrome)
M - Methanol
A - Aspirin/salicylate toxicity
R - Renal failure
K - Ketoacidosis (DKA)
Normal anion gap metabolic acidosis differential diagnosis
DURHAAM
D - Diarrhea *
U - Ureteral diversion or fistula
R - Rental Tubular Acidosis (RTA)**
H - Hyperalimentation
A - Acetazolamide (CA inhbitior)
A - Addison’s disease
M - Miscellanous
When do you order a urine chloride test?
You order to narrow down the differential diagnosis of metabolic alkalosis.
Low Urine chloride <20 mEq = saline responsive
High Urine chloride >20 mEq = saline resistant
Metabolic Alkalosis Differential diagnosis with LOW urine chloride
Low Urine chloride <20 mEq = saline responsive
Vomiting* (losing HCl from stomach)
Remote thiazide or loop diuretic use** (K+ losing)
Volume depletion
Posthypercapnic alkalosis
Metabolic Alkalosis Differential diagnosis with HIGH urine chloride
High Urine chloride >20 mEq = saline resistant
Recent thiazide or loop diuretic use
Hyperaldosteronism
Bartter syndrome*
Gitelman syndrome*
Liddle syndrome*
Respiratory acidosis symptoms
Symptoms are typically asymptomatic but when occur are often symptoms of hypercapnia
Progressive symptoms as pCO2 increases and pH decreases such as SOB, somnolent, headaches, agitation, hyper-solmnolent, coma (CO2 narcosis)
Respiratory acidosis differential diagnosis
Hypoventilation due to:
COPD
Acute Lung disease (pneumonia, PE)
CHF
Inappropriate ventilation settings
CNS lesion
Sedative medication (narcotics/opioids)
Respiratory alkalosis symptoms
Paresthesia
Lightheadedness
Carpopedal spasms
Respiratory alkalosis differential diagnosis
Hyperventilation due to:
Anxiety/panic attacks*
Hypoxia (elevated altitude)
Salicylate overdose (early - aspirin)
Pregnancy*
PE*
Altitude sickness
Hypoxia from high altitude (headache, nausea, lightheadedness)
Hyperventilation to increase O2 can lead to decrease CO2 and cause respiratory alkalosis (increased pH)
The brain senses this increase pH and inhibits ventilation (limiting oxygenation now)
Treated with acetalozamide
Acetalozamide
Drug used to prevent/treat altitude sickness that causes respiratory alkalosis. It is a carbonic anhydrase inhibitor that acts on the PCT to remove HCO3 loss (excretion) to decrease pH (towards metabolic acidosis)
Acute and chronic respiratory acidosis
Recurrent vomiting (losing HCl from the stomach so low urine chloride test <20 mEq/L)
High anion gap metabolic acidosis with inappropriate compensation
Metabolic alkalosis with appropriate compensation
