Flashcards in Acid Base Physiology Deck (36):
What are the golden rules of Acid Base Physiology ?
1. PCO2 and HCO3 always change in the same direction
2. The secondary physiologic compensatory mechanisms must be present. If not, its a mixed disorder
3. The compensatory mechanisms never fully correct pH, they bring it back to normal. If they overcorrect it is a mixed disorder
Metabolic Acidosis, Describe the three main types of etiology
Reduced Bicarbonate: Caused by decreased renal acid excretion, Direct Bicarb loss in the urine or feces, ( Type 2 renal acidosis and Intestinal fistulas / Diarrhea ) Or increased acid generation (Lactic Acids and Keto acids)
What will type 1 renal tubular acidosis cause and how ?
Distal renal tubule acidosis has a defective H/ATPase
How will renal failure cause metabolic acidosis ?
It will decrease NH4 excretion which will cause acidosis by using up the bicarbonate.
What are the causes of respiratory acidosis ?
Buffering mechanisms that raise bicarbonate
Increased NH4 excretion causes generation of new bicarbonate
What more common causes will a H & P show you that will que you in to respiratory acidosis ?
COPD, Smoking, Chronic Muscle Myeopathy
What causes respiratory alkylosis ?
Reduced Carbon dioxide due to increased alveolar ventilation. ( Hyperventilation)
Buffering processes that lower plasma bicarbonate.
When kidneys reduce net acid excretion.
Most common cause of chronic alkylosis ?
Chronic vomiting ?
This will cause a loss of H+ from the stomach bile. Inducing metabolic alkylosis
What will hyperaldosteronism cause ?
Excessive water reabsorption but aldosterone also induces H+ secretion which can cause metabolic alkylosis
How do Cl changes relate to Bicarb changes ?
They move in opposite directions.
1. Bicarb is elevated what two diseases could this be ?
What would you do next ?
Metabolic alkylosis, or respiratory acidosis in the chronic phase when the kidney has compensated.
Examine the patient, is he throwing up or not breathing ect.
What is the bodies major adaptive response to an acid load ?
Is Na affected by acid base disorders ?
No, not directly
Is plasma Cl affected in acid base disorders ?
Yes, it is altered in all acid base disorders. Except in increased metabolic gap ionic disorders.
How is the body's phosphate homeostasis maintained ?
By the excretion of dietary phosphate. This mechanism accounts for the excretion of 10 - 40 mEq of phosphate per day.
What happens in the plasma when strong acids dissociate ?
The H+ is buffered by bicarbonate and the A- will be excreted in the urine or reabsorbed by the kidney.
What happens when the anion is retained by the kidney ?
There will be an unmeasured anion concentration retained in the plasma. This is called an increased plasma anion gap.
What is total CO2 measure ?
CO2 and bicarbonate, normally 25-26 and will exceeds plasma bicarb.
Normal value for Bicarbonate ?
What kind of buffering system are humans ?
[ pH ] H+ =
24 [ ( CO2 / HCO3 ) ]
What is the easy way to convert pH to H+ concentration ?
[ H+ ] = 80 - pH decimal digits
Normal pH ?
7.35 - 7.45
Normal pCO2 ?
36 mmHg - 44 mmHg
22 - 26 mmHg
Metabolic disorders affect ?
Respiratory Disorders ?
Affect CO2 levels and there will be slight bicarbonate level changes
What is the major urine buffer ?
Phosphate and Ammonia
Low bicarbonate with normal anion gap, + Urine anion gap =
Renal Tubular Acidosis
Low Bicarbonate with Raised Serum anion gap ?
Renal retention of A- after strong acid dissociation.
Lactic acidosis, diabetic acidosis, Alcoholic Keto-acidosis, Poisoning, Uremic acidosis
Low bicarbonate level with a normal anion gap and a negative urine anion gap ?
Non renal wasting
Diahrrhea, External loss of pancreatic and billary secretions
Urine anion gap measures ?
Urine Na + K - Cl
NH4+ levels in the Urine indirectly, When NH4 is excreted Cl will follow lowering the UAG
Is Cl altered by acid base disorders ?
Is Na altered by acid base disorders ?