Acid Base 2 Flashcards
What is the presentation of acute metabolic acidosis?
pH < 7.2
Hyperventilation
Bradycardia/HF
Obtundation/confusion
What acidic pH is incompatible with life?
6.7
What is the presentation of chronic metabolic acidosis?
pH 7.2 - 7.34
Relatively asx
What are causes of chronic metabolic acidosis?
Renal tubular acidosis
Chronic renal insufficiency
What are the causes of bone demineralization?
Children = Rickets (growth failure, weight loss) Adults = Osteopenia (RTA, CRI)
What does a metabolic acidosis with a normal anion gap represent?
Decreased HCO3
Increased Cl
Keeps electroneutrality
What is a cause of metabolic acidosis with a normal anion gap?
Excessive diarrhea
Intrinsic Renal Disease (RTA)
What is a clinically relevant anion gap?
greater than 17
How does excessive diarrhea cause hyperchloremic metabolic acidosis?
Pancreatic secretions are rich in bicarbonate
Excessive loss of bicarb results in excessive reabsorption of H+
Cl reabsorbed (as part of this exchange) = minimizes gap
How does intrinsic renal disease cause hyperchloremic metabolic acidosis?
Normally, H+ ions are almost entirely eliminated by kidneys
RTA = inability to eliminate H+
Prevents reabsorption of bicarb, and Cl is retained
What is another name for a metabolic acidosis with a normal anion gap?
Hyperchloremic metabolic acidosis
What causes an increased anion gap in metabolic acidosis?
Presence of organic acids (lactic acids, ketoacids, and uremic acids) or toxins
Acids/toxins consume bicarb becoming anions
See a decreased bicarb with increased chlorine
What does MUDPILES stand for?
Methanol Uremia DKA Propylene glycol Isoniazid Lactic acid Ethanol Salicylates
What are the sources that increase the anion gap?
DKA
Uremia
Ethanol
Lactic acidosis
What is the treatment strategy for severe metabolic acidosis?
pH < 7.2
Goal pH = 7.2
Goal HCO3 = 10-12
Give IV sodium bicarb
What is the dose of bicarb in a vial?
50meq/50mL
How do we calculate the sodium bicarbonate dosage?
(0.5L/kg x wt) x (Goal bicarb - current bicarb)
What is the target serum bicarb for severe metabolic acidosis?
10-12 in 24 hours
Administer 50% over 4 hours, then last 50% over next 20 hours
What is the target serum bicarb for moderate metabolic acidosis?
22-24 over 3-5 days
What are problems with administered bicarb IV?
Systemic overshoot (excessive dosing in DKA, lactic acidosis, ARF, ?Ethanol)
Severe hypernatremia
Extravasation
What is a problem with administering oral bicarb
GI intolerance
What is the treatment strategy for moderate metabolic acidosis?
pH 7.2 - 7.34
Goal pH = 7.4
Goal bicarb = 22-26
Give oral bicarb
What is severe alkalosis?
pH > 7.6
What pH is incompatible with life?
> 7.7
What os the presentation of metabolic alkalosis?
Hypovolemia
Hypervolemia
pH > 7.6
What are the affects of a pH > 7.6?
Cardiac arrhythmias NM irritability (tetany/tremors)
What are the causes of metabolic alkalosis?
Increased bicarb retention
Increased bicarb concentration
Hyperaldosteronism
What causes bicarb retention?
Loss of H+ ions
Nasogastric suctioning
Vomiting
What causes increased bicarb concentrations?
Diuretics from contraction alkalosis
What diseases cause hyperaldosteronism?
Cushing’s
Hyperaldosteronism
How does hyperaldosteronism cause metabolic acidosis
Promote hyper renin states
If a patient has metabolic alkalosis and is hypovolemic, how do we treat them?
IV NaCl
If a patient has metabolic acidosis and is euvolemic, how do we treat them?
Aldosterone antagonist
If a patient has a pH greater than 7.6, how do we treat them?
Hydrochloric acid
What is the presentation of respiratory alkalosis?
Hyperventilation
CNS (agitation/anxiety, lightheadedness)
CV (chest pain)
What are the results of hyperventilation?
Decreased CO2
Lightheadedness, confusion, syncope
N/V
Muscle cramps, tetany
What are the causes of hyperventilation?
CNS mediated
Medications
Others
What CNS causes are associated with hyperventilation?
Pain Anxiety Fever Head trauma CVA
What medications are associated with hyperventilation?
Theophylline
Nicotine
Catecholamines
What are other causes of hyperventilation?
Severe anemia
High altitude
Hyperthyroidism
What is the treatment strategy if the patient has respiratory alkalosis and their pH is < 7.6?
Remove underlying cause
When do we give O2 in respiratory alkalosis?
PaO2 < 50
What is the treatment for respiratory alkalosis with a pH > 7.6?
Mechanical ventilation
What is severe acidosis?
pH < 7.2
What acidosis is incompatible with life?
< 6.7
What is the cause of respiratory acidosis?
Failure of lungs to eliminate CO2 Ventilatory failure (Obstructive lung dz/NM dz) Perfusion failure (Massive PE)
What is the presentation of respiratory acidosis?
Compatible with life despite paCO2 80-100
No longer dependent on Co2 for respiratory drive
Dependent on O2 for respiratory drive
What patients are highly susceptible to acute respiratory decompensation?
Acute respiratory infections
Narctoic analgesics
Sedative/hypnotics
O2 (CO2 narcosis)
When do we give mechanical ventilation?
Acute respiratory acidosis
PaCO2 > 80
or
PaO2 < 40
When do we give O2 in respiratory acidosis?
Chronic respiratory acidosis
PaO2 < 50
