Fluid and Electrolyte Requirements in Disease Flashcards
What is the normal pH range of arterial blood?
7.35-7.45
What is the pH of extracellular fluid?
7.4
At what pH levels would death occur?
less than 6.8
more than 8.0
What pH level classifies as acidosis (acidemia)?
below 7.35
What pH level classifies as alkalosis (alkalemia)?
above 7.45
What would small changes in pH cause major disturbances to?
- enzyme functions (only function at narrow pH ranges)
- affect electrolytes (Na+, K+, CL-)
- affect hormones
- affect bone synthesis, re-absorption
Which organs help regulate pH and how?
- Lungs - through carbonic acid-bicarbonate buffer system
- changing respiratory rates changes PCO2 - Kidneys - through renal compensation
Does the body produce more acid or more bases?
more acid
Why does the body produce more acid?
- acid taken with food
- acids produced by metabolism of lipids/proteins
- cellular metabolism produces CO2
How to calculate pH?
pH = - log [H+]
What is buffering?
buffer system consist of weak acid and anion
What are the 3 buffering systems?
- Protein buffer system - amino acids, H+
- Carbonic acid-bicarbonate
- buffer changes caused by organic and fixed acids - Phosphate
- buffer pH in the ICF
What are the common acids?
- carbonic acid
- sulfuric/phosphoric acid
- organic acids
What happens when carbonic acid affects of ECF?
- CO2 reacts with water to form carbonic acid
- inverse relationship between pH and conc of CO2
When is sulfuric/phosphoric acid generated?
- during catabolism of amino acids
What are some organic acids?
- lactic acid
- ketone bodies
Explain protein buffering in terms of pH increasing and decreasing:
pH climbs = carboxyl group of amino acid acts as weak base
pH drops = amino group acts as weak base
What does the haemoglobin buffer system do?
prevents pH changes when PCO2 is rising or falling
Explain what happens in the carbonic acid-bicarbonate buffer system:
- classic chemical buffer
- body eliminates chemicals from either end of chemical reaction to maintain pH
- effective in converting carbonic acid to CO2 through carbonic anhydrase
- then removes CO2 through respiration
What is the chemical reaction of carbonic-acid-bicarbonate buffer system
H+ + HCO3- H2CO3 H2O + CO2
How is the alkali removed when in access?
through kidneys
How fast does the buffer function work?
almost instantaneously
How fast does respiratory mechanism take to do corrections?
several minutes to hours
How fast does renal mechanism take to do corrections?
several hours to days
What is the principle effect of acidosis?
depression of CNS through decrease in synaptic transmission
What generally happens in acidosis?
- weakness
- deranged CNS function = greatest threat
- severe state causes: disorientation, coma, death
What are the responses to acidosis? (alkalosis is opposite)
- increase respiratory rate to lower CO2
- other buffer systems absorb H+
- secrete H+ in kidneys
What does alkalosis cause?
- over excitability of central/peripheral nervous systems
- numbness
- lightheadedness
- can cause: nervousness, muscle spasm, tetany, convulsions, loss consciousness, death
What does the Bohr effect observe?
the relationship of Oxyhaemoglobin and pO2
When do respiratory acid-base disorders occur?
when abnormal respiratory function cause rise/fall in CO2 in ECF
When do metabolic acid-base disorders occur?
- generation of organic or fixed acids
- anything affecting concentration of bicarbonate ions in ECF
- bicarbonate loss during chronic diarrhea
When does respiratory acidosis occur?
from excessive levels of CO2 in body fluids
When does respiratory alkalosis occur?
- relative rare condition
- associated with hyperventilation
what is hypercapnia?
high levels of CO2 in blood
What are chronic conditions of respiratory acidosis?
- depression of respiratory center in brain that controls breathing rate - drugs/head trauma
- paralysis of respiratory/chest muscles
- emphysema
what are the acute conditions of respiratory acidosis?
- adult respiratory distress syndrome
- pulmonary edema
- pneumothorax
What do the kidneys specifically elimate and retain to compensate respiratory acidosis?
eliminate H+, retain bicarbonate ion
Respiratory acidosis signs/symptoms:
- breathlessness
- restlessness
- lethargy, disorientation
- tremors, convulsions, coma
- respiratory rate rapid then gradually depressed
- skin warm, flushed, due to vasodilation from excess CO2
Respiratory acidosis treatment?
- restore ventilation
- IV lactate solution
- treat underlying dysfunction/disease
What is hypocapnea?
when pCO2 is less than 35mmHg
What is the primary cause of respiratory alkalosis?
hyperventilation
What conditions stimulate respiratory centre in regards to respiratory alkalosis?
- oxygen deficiency at high altitudes
- pulmonary disease + congestive heart failure by hypoxia
- acute anxiety
- fever, anaemia
- early salicylate intoxication
- cirrhosis
- gram-negative sepsis
Respiratory alkalosis treatment?
- treat underlying cause
- breath into paper bag
- IV chloride containing solution (Cl- ions replace lost bicarbonate ions)
When does metabolic alkalosis occur?
- when HCO3- concentrations become elevated (by repeated vomiting)
What are the symptoms of metabolic acidosis?
- headache
- nausea
- vomiting
- coma, death
What can be done to compensate metabolic acidosis?
- increase ventilation
- renal excretion of H+
- K+ exchange with H+ in ECF
- H+ into cells, K+ out of cells
Metabolic acidosis treatment?
IV lactate solution
What can cause metabolic alkalosis?
- excessive vomiting (lose stomach acid)
- excessive use of alkaline drugs
- certain diuretics
- endocrine disorders
- heavy ingestion of antacids
- severe dehydration
What can be done to compensate metabolic alkalosis?
- can’t count on kidneys since it usually occurs with renal dysfunction
- hypoventilation limited by hypoxia
BASICALLY, NOT MUCH CAN BE DONE???
What are the symptoms of metabolic alkalosis?
- respiration = slow/shallow
- hyperactive reflexes, tetany
- often related to depletion of electrolytes
- atrial tachycardia
- dysrhythmias
Metabolic alkalosis treatment?
- Electrolytes to replace lost ones
- IV chloride containing solution
- Treat underlying disorder
How to diagnose acid-base imbalances?
- Note pH low or high
- Decide which values (pCO2 or HCO3-) is outside normal ranges and is the cause of the problem
- if its change in pCO2 = respiratory problem
- If change in HCO3- = metabolic problem
