Acid-Base Flashcards
Steps in determining the cause
- Acidosis or alkalosis
- Respiratory or metabolic
- Pure or mixed
How to know if an acid-base issue is respiratory or metabolic
- If pH and CO2 go SAME DIRECTION = METABOLIC
- If pH and CO2 go OPPOSITE DIRECTION = RESPIRATORY
Respiratory problem:
Telling if it is pure or mixed
Pure - ∆pH = 0.08 per ∆10 paCO2 ± .02 (OPPOSITE DIRECTION)
Higher? – Metabolic alkalosis also
Lower? – Metabolic acidosis also
Metabolic acidosis:
Telling if it is pure or mixed
Pure - CO2 is decreased
Mixed - CO2 is normal/high
Telling compensation for a metabolic acidosis
pCO2 = 1.5(HCO3) + 8 ± 2
Telling compensation for a metabolic alkalosis
∆pCO2 = 0.7 per ∆1 HCO3 (SAME DIRECTION)
Anion gap equation
Na - Cl - HCO3
Causes of high anion gap met. acidosis
Methanol Uremia Diabetic ketoacidosis Paraldehyde INH Lactic acidosis Ethanol, ethylene glycol Salicylates
3 general categories/causes of metabolic acidosis
- HCO3 loss (GI, renal)
- H+ loading (DKA, lactic acid)
- Less H+ excretion (uremia, RTA)
Causes of lactic acidosis
A = hypoxia (shock, anemia, HF, CO) B1 = systemic Dz (DM, liver, sepsis, seizure) B2 = drugs/toxins (EtOH, methanol, Eth. glyc) B3 = cong. metab. error (G6PD def.)
Tests for cause of pre-renal acidosis
EKG, lactic acid level, cardiac enzymes (HF, MI)
Treatment for metabolic acidosis
Oxygen, loop diuretic (H+ secretion), fluid restriction (edema), HCO3, ACEI (cautious)
Causes of normal anion gap (hyperchloremic) metabolic acidosis
Hyperalimentation Addison's, acetazolamide (HCO3 loss) RTA (low HCO3, high H+) Diarrhea (low HCO3, low K) Ureteral diversion Pancreatic fistula (low HCO3, low K) Spironolactone (H+ retention)
Types of RTA
Proximal = Increased HCO3 excretion
- Myeloma, metal poisoning, Wilson’s
Distal = Decreased H+ secretion
- SLE, Sjogren’s, Toluene
Causes of metabolic alkalosis
Contraction (volume loss -> RAAS -> H+ secretion) Licorice Endocrine Vomiting (loss of acid) Excess base (increased H+ excretion) Refeeding Post hypercapnia Diuretics (increased H+ secretion)
Causes of chlorine LOSS (+ reabsorbed or not)
- Vomiting - will be reabsorbed
- N/G suction - will be reabsorbed)
- Diuretics - will be reabsorbed
- Endocrine - will NOT be reabsorbed
- Severe hypokalemia - will NOT be reabsorbed
Drug to give in case of vomiting –> contraction alkalosis
Spironolactone (for excess aldosterone due to volume depletion)
Weakness –> potential causes?
- Hypothyroid
- Electolyte imbalance (low Na, K, Mg, Ca)
Hypokalemia on EKG
Flattened T wave –> ST depression (severe)
Hyperkalemia on EKG
Elevated T wave –> QRS spacing (severe)
HTN + hypokalemia + metabolic alkalosis = ?
Another clue?
Hyperaldosteronism (Conn’s disease)
Doesn’t respond to saline/fluids
Causes of respiratory acidosis
Anything causing HYPOVENTILATION
- Drugs, CVA, obstruction, COPD, pneumonia, pulmonary edema
Causes of respiratory alkalosis
Anything that causes HYPERVENTILATION:
CNS disease Hypoxia Anxiety Mech. ventilation Progesterone Salicylates, sepsis
Sepsis can cause what acid/base problems?
Lactic (metabolic) acidosis, respiratory alkalosis
