Acid base Flashcards
List the symptoms of metabolic acidosis
- headache
- Decreased Bp
- Hyperkalemia
- muscle twitching
- Kussmaul respiration (compensatory hyperventilation)
- Nausea, vomitting, Diarrhea
What are the causes of metabolic acidosis?
- Diabetic ketoacidosis
- Severe Diarrhea (looses biocarbonate)
- renal failure
- shock
What is Mrs mitchells diagnosis?
Hyperchloremic (normal anion gap) metabolic acidosis
Complicated with hypovolemia (dehydration)
What are the medical results for someone with metabolic acidosis?
Low pH
HCO3- very low
pCO2 low
Hypokalaemia (plasma potassium level less than 3.5mmol/L)
What is the compensatory mechanism for metabolic acidosis?
compensatory hyperventilation = pCO2 low
What is Hypokalaemia?
(plasma potassium level less than 3.5mmol/L)
What is the name for Mrs mitchells condition the next day
Chronic respiratory alkalosis
Name the 3 compensatory mechanisms used by the body to handle PH changes?
- Physiologic buffer
- Pulmonary compensation
- Renal compensation
What are the the Physiologic buffers?
(weak acid and base salt or weak base and acid salt)
bicarbonate-carbonic acid buffering system,
• intracellular protein buffers,
• phosphate buffers in the bone.
What is the the Pulmonary compensation system?
changes in ventilation changes the partial pressure of arterial carbon dioxide (PCO2) to drive pH towards normal range.
A drop in pH, results in increased ventilation to blow off excess CO2
An increase in pH decreases ventilatory effort, which increases PCO2 and lowers pH back towards normal.
What is the the Renal compensation system?
starts when other mechanisms have been ineffective, generally after about 6 hours of sustained acidosis or alkalosis.
• In acidosis, kidneys excrete H+ in urine and retain HCO3-.
• In alkalosis, kidneys excrete HCO3-and retain H+ in the form of organic acids.
What is the normal blood PH range?
7.35 to 7.45.
Describe the PH and PCO2 for respiratory acidosis
pH is less than 7.35 and PCO2 is above 45 mm Hg
What causes chronic and acute respiratory acidosis?
occurs secondary to a chronic reduction in alveolar ventilation -Chronic COPD
Acute- Over sedation, immobility, respiratory muscle paralysis
Which two factors determine arterial PH in respiratory acidosis?
What is the compensatory mechanism for resp-acidosis?
Relationship between PCO2 and plasma HCO3
Over a period of 1 to 3 days, renal conservation of HCO3- results in an increase in pH.
What causes respiratory alkalosis?
When PCO2 is reduced, causing an increase in pH (increased alveolar ventilation, hepatic disease, pregnancy)
What happens with the compensatory mechanism in chronic respiratory alkalosis?
result in mild reduction in plasma HCO3- levels to maintain a near normal or normal pH. This causes a mixed acid-base disorder.
What is the treatment for respiratory alkalosis?
Fix underlying problem- anxiety
What is Metabolic acidosis?
An increase in amount of absolute body acid ( excess production of acids or excessive loss of bicarbonate, sodium, and potassium)
What can happen with potassium in sever acidosis?
significant overall depletion of total body potassium stores can occur
So I.V. potassium is given to patients early in treatment
(despite elevated serum potassium)
caused by K+ leaving the cell as H+ moves intracellulary as kidneys try to keep sodium)
When does metabolic alkalosis occur?
when HCO3-is increased, usually as the result of excessive loss of metabolic acids. PH is above 7.45
What are the causes of metabolic alkalosis?
diuretics,
prolonged vomiting,
Cushing’s syndrome
How does chloride concentration dictate treatment for metabolic alkalosis?
If chloride concentration is less than 15mmol/L- condition is saline saline-responsive and treatment with 0.9% saline is needed.
Urine chloride levels above 25 mmol/L indicate nonsalineresponsive metabolic alkalosis treatment is based on addressing the underlying problem
What is the compensatory mechanism for metabolic alkalosis?
alveolar hypoventilation causing a rise in PaCO2), which reduces the change in pH
What is the compensatory mechanism for metabolic acidosis?
hyperventilation to decrease the arterial pCO2
What is Mrs mitchells anion gap?
It is normal- 10mmol/L to 8mmol/L
Describe the normal range for anion gap
Normal range 8-16 mmol/L. However, there are always unmeasurable anions, so an anion gap of less than 11 mmol/L is considered normal
What is the equation to calculate serum anion gap?
(Na + K) -(Cl + HCO3)
Name 3 agents which can increase the anion gap
Lactic acidosis
Diabetic ketoacidosis
Alcoholic ketoacidosis
What is the treatment for Mrs Mitchel?l
IV Lactated Ringer’s • Preferred over normal saline as it corrects associated metabolic acidosis • Lactate is metabolised into bicarbonate • Potassium supplementation
Why is Mrs mitchel’s next day so complicated?
Biocarbonate increases- metabolic acidosis is being corrected
PCO2 is lower than expected causing respiratory alkalaemia.
Why?
central chemoreceptors are slow in responding to increase in bicarbonate- compensatory hyperventilation is still functional.
Biocarbonate will enter brain interstitial fluid in 12-24h. This will reduce central chemoreceptor inhibition.
The recovery of pCO2 to normal lags behind the rise in the bicarbonate.
Which percentage of water loss causes heat exhaustion, hallucination and circulator collapse plus heat stroke?
6% heat exhaustion
8% hallucination
10% circulatory collapse and heat stroke
What is the normal range for PCO2?
35–45 mmHg
Less- hypervetilating
More- Hypoventilating
Why does chloride increased during metabolic acidosis?
The lowered bicarbonate concentration, is counterbalanced by increase in plasma chloride concentration. This is why the anion gap is normal.
