Acid Base 1 Flashcards
What effect does low pH on the body if it is out of control acutely? [4]
Acutely:
* Negatively inotropic
* ‘Air hunger’: panting away
* Part of critical illness syndrome – generalised cellular dysfunction
* Affects body K+ distribution (to counter H+ coming into cell)
What happens when low pH is out of control chronically? [3]
- Effect of bones and stone formation
- Associated with progression of kidney disease
- Paradoxical relationship with mortality
Name 3 ways that acid is constantly being added to body [3]
- Cellular respiration: after Co2 & H20 produced - get CA converting to HCO3- & H+. Roughly 15mol/d
- Dietary acid (titrable): amino acids from diet protein. Roughly 60mmol/d of sulphuric and phosphoric acid from diet
- 3) Other physiological and pathological states – eg exercise (lactic acid), ketoacidosis (uncontrolled diabetes - use ketones instead of glucose as fuel source, which are acidid)
Why would sepsis cause acidosis?
In sepsis: constrict small arterioles of limbs, gut and skin: they’re all metabolizing anaerobically: lactic acid
What are the 4 main buffer systems in you body?
- Plasma proteins
- Bone
- Intracellular phosphates (e.g. ATP)
- Bicarbonate - useful because measurable
What is Henderson-Hasselbach equation in the body for pH blood plasma? [1]
How does infusing a Ptx with acid effect the Ptx? [1]
Causes decrease of serum bicarbonate. Drives equation to left: causes increase in PCO2: blow off the acid as CO2 because now hyperventilation
How do you clear Acid from the body? [2]
The lungs
* High pCO2 and low pH both independently increase ventilation
* Clears ‘volatile acid’
* Does not regenerate bicarbonate buffer
* Quick
The kidneys
* Can dramatically increase the amount of acid secretion in urine
* This regenerates bicarbonate buffer
* The only method for excreting ‘titrable’ acid
* Slower
Mechanism of reabsorbing HCO3- at PCT ?
Excrete acid in urine
Regenerate HCO3- at DCT & CD?
What is the name of the cells where this occurs?
What are the two main urinary buffers? [2]
In alpha intercalated cells:
- the α-intercalated cell (IC) of the collecting duct (CD) is critical for renal acid secretion and helps maintain acid-base balance.
- pushes out protons into urine. BUT can only does this for certain amount.
- Need urinary buffers to be excreted to soak up the protons, so can keep excreting them.
Two main urinary buffers:
- Titrable acid (NaH2PO4)
- Ammonium system – can generate more buffer. NH3 NH4+
Hyperventilation causes acid / alkolosis?
Hypoventilation causes acid / alkolosis?
Hyperventilation causes alkolosis: expelling more CO2
Hypoventilation causes acidosis
How can you cause metabolic acodosis? [4]
Adding Acid to your body:
- Ingestion of acid (Aspirin)
- Generation of acid (lactic acid, ketones)
- Retention of acid (renal failure)
Loss of bicarbonate:
- Gut – eg diarrhoea, Kidneys - RTA
How do you calculate anion gap?
What is normal anion gap? [1]
Cations - Anions
Normal is 16
What is hyperchloremic metabolic acidosis?
What is the most common cause? [1]
More rare cause? [1]
Normal anion gap acidosis is an acidosis that is not accompanied by an abnormally increased anion gap.
Caused by loss of HCO3- WITH a compensatory rise in Chlorine
Most common cause: diarrhoea
Also caused by: renal tubular acidosis
What is high anion gap acidosis?
Caused by? [4]
Addition of exogenous acid: NO COMPENSATORY RISE IN Cl-
Commonest causes:
* Lactic acidosis
* Ketoacidosis
* Renal failure
* Poisoning
