L5-L6- Acid Base Disorders Flashcards
Normal Value and Range for Bicarbonate?
[HCO3] = 26 +/- 4 mmol/liter
22-30
ARterial blood gas listing and normal values?
pH/PaCO2/PaO2
pH normal = 7.36-7.44
PaCO2= 36-44
PaO2 = 60-90
What/s the HH equation for pH homeostasis?
pH = 6.10 + Log ( [HCO3] / 0.03 PaCO2)
pH = [HCO3] / PaCO2
pH = Kidney/Lung
Acidemia vs ACidosis?
Alkalosis vs alkalemia?
Acidosis - decrease pH
Acidemia - measured pH is <7.36
Alkalosis - increase pH
Alkalemia - measured pH >7.44
What are the three adaptive responses to changes in pH?
**1) Buffer –> hide it! **
- HCO3 binds free H+ and gets consumed so have to make more of it
2) Compensation
- generate secondary disorder to minimize changes in pH
- NEVER brings pH back to normal
- should go away when primary goes away (*except Maintained Metab Alkalosis)
- HCO3 and PaCO2 always change in parallel
3) Elimination in Kidney - takes a while
How does the kidney eliminate H+? In what three areas? when does the urine become acidic? How low can it go?
1) Proximal Convoluted tubule: Urine pH = Serum pH; all bicarb filtered and then H+ secreted and binds it. Brush Border CA eliminates and makes CO2 and H20. Then Reclaim and remake HCO3 bc H+ secretion linked to bicarb creation.
2) Distal Convoluted Tubule: Titratable Acids (Phosphates and Sulfates) increase H+ secretion and make urine slightly more acidic now
3) Collecting Duct: Ammonia Production!!! Excess H+ Secreted here (majority of it!) by CD - I.C. cells and urine becomes very acidic
Lowest pH of urine is 4.4
How can you tell if it is a primary metabolic change or a primary respiratory change?
Primary Metabolic - Changes in pH and Bicarb happen in parallel
Primary Respiratory - changes in pH and Bicarb happen in opposite directions
How can you tell Simple AB disorders?
Simple - single AB disorders and compensation continues only as long as primary does, compensation does NOT return pH to normal, and Compensation MUST be within predicted range!!
How do you know if it’s a mixed disorder?
Mixed - 2 or more primary AB disorders
_Violates the rules of simple: _
- can bring pH back to normal
- Bicarb abd PaCo2 do NOT move in parallel
- compensation persists
- compensaiton NOT in predicted range
How does the GI tract contribute to AB disorders? What does vomiting cause? What does Diarrhea cause?
Normally, Gastric Cells secrete HCl into lumen and Bicarb into blood and Colon Cells secrete Bicarb into lumen and HCl in to blood
Vomiting therefore leads to Alkalosis
Diarrhea therefore leads to Acidosis
What is Metabolic Acidosis? What is the compensation? What are the effects?
How can you tell if renal cause or not?
MA = Decrease in [HCO3} and Decrease pH
Compensation = Decrease PaCO2
_Effects: _
- Oxygen Dissoc crve shifts right and more distributed to tissues
- CNS depression
- Hyperkalemia, Less Cardiac Contractility, Arrhythnmia
- Decreased pulmonary Blood flow
- Renal increase NH3 production and HCO3 production
_URINE PH _
- Acid = non-renal cause
- Alkaline = Renal Cause = Paradoxical Alk Urine = RTA
How do you calculate Anion Gap? What is the normal range for anion gap?
AG = Na - {HCO3 + Cl]
Normal range is 9-13
>13 = High Anion Gap
In General, what are the causes of Metabolic ACidosis? (not specific ones yet)
H+ Gain from either increased production or decreased secretion
- CKD disease and less nephrons
- RTA and H+ impaired
HCO3 Losses from either Diarrhea or RTA!!!
What are the causes of Non-AG Metabolic Acidosis aka Hyperchloremic MA? causes?
HEART CCU
Hyperalimentation - SO4/PO4
Expansion of volume - Saline given
Acetazolamide - Renal cause
RTA - Renal Cause
Diarrhea - GI
Cholestyramine - GI
Carbonic Anhydrase Inhibitor - Renal
Uterosigmoidoscopy - Renal/GI
What are the causes of high anion gap Metabolic acidosis? Biomarkers?
MUDPILES
Methanol - formaldehyde
Uremia - creatinine
Diabetes - ketones
Propylene glycol (given w/drugs for Status Epilepticus)- Increased Osmotic Gap
Lactate
INH/INfection - Medication levels
Ethylene Glycol - Oxalate/Increased Osmotic Gap
Salicylates