Acid-Base balance Flashcards
Define buffer system
A buffer is a solution that can maintain a nearly constant pH if its diluted or if strong acids/bases added
Buffer solution consists of mixture of weak acid + its conjugate base or weak base + its conjugate acid
acid-base balance= is the regulation of hydrogen ion (H+)
Know the H+ concentration and pH of plasma
normal blood pH level of a healthy person ranges from 7.35 to 7.45
Thus at a normal blood pH of 7.4, [H+] is 40 nmol/l, whereas at pH 7.0 it is 100 nmol/l
**pH of ECF: 7.35 - 7.45 **= pH levels compatible with life
- If plasma levels fall below < 7.35 (acidaemia) = results in acidosis (reflects acidic nature of body)
n.b. Acidaemia - aemia to do with blood
If plasma levels > 7.45 (alkalaemia) - results in alkalosis
Alteration outside these boundaries affects all body systems due to impacts on tertiary structures of proteins which are responsible for their function so tissues can’t properly function
this can result in circulatory collapse, coma + death
what is pH
- Acidity/alkalinity of a solution is measured as pH
- The more acidic a solution the greater [H+] and lower pH (acid is a proton donor)
- The more alkaline a solution the lower [H+] and higher pH
- Water has pH of 7 so neutral (base is a proton acceptor)
n.b. a conjugate pair consits of an acid + base that differ by H+
calculate:
pH= -log[H+]
n.b. Log10 of 2 =0.3 so a doubling/halving of [H+] causes shift in pH of 0.3
pH is proportional to 1/[H+] or inversely proportional to [H+]
define strong acid vs weak acid
strong acid=dissociates fully in solution to give H+ (irreversible)
weak acid= partially dissociates to give H+ (reversible)
what is the major buffer system of the intracellular fluid
The major buffer that occurs in the ICF is the phosphate buffer
its responsible for renal regulation mechanisms in urine
H+ + HPO42- ⇋ H2PO4-
- Can accept H+ and move from left to right
explain the control of blood pH by carbonic acid-hydrogencarbonate buffer system
The H2CO3/HCO3- buffer is present in blood plasma, maintaining the pH between 7.35 and 7.45
H2CO3= carbonic acid {a weak acid} (can donate H+/ proton donor)
H2CO3-> H+ + HCO3-
kidneys have two main ways to maintain acid-base balance: their cells reabsorb bicarbonate HCO3− from the urine back to the blood and they secrete hydrogen (H+) ions into the urine. By adjusting the amounts reabsorbed and secreted, they balance the bloodstream’s pH.
if something is wrong with the lungs we have problems with carbonic acid (respiratory acidosis is when we can’t remove enough co2 from body)
n.b. co2 makes blood more acidic
HYDROGEN CARBONATE same as BICARBONATE
how does a protein buffer system work?
protein’s acidic + basic side chains can give/take up H+
- If pH climbs - carboxyl group (COOH) of aa acts as weak acid and releases H+ (n.b. to make something more basic we need to get rid of H+)
- If pH drops - amino group (NH2) acts as weak base and absorbs H+
what is a normal level of co2
Normal CO2 level: 35-45mmHg= 4.7-6.0kPa
Respiratory regulation - lungs
* Help regulate acid-base balance by eliminating retaining CO2
* May alter rate/depth of respirations in order to hold on/get rid of more CO2
* By chaning breathing can change pH rapidly - occurring within mins
what is normal bicarbonate level in body?
Normal HCO3- level: 22 - 26 mEq/L
Renal regulation - kidneys
* Long-term regulator of acid-base balance
* Slower to respond - may take hours/days to correct pH but have bigger capacity for amount of acid thye can excrete
* Kidneys maintain balance by excreting/conserving HCO3- + H+
patient has:
-temperature
-coughing up green
* pH - 7.33
* pO2 - 9.6 kPa
* pCO2 - 6.7 kPa
what is the diagnosis?
respiratory acidosis
-probs respiratory pneumonia
he’s struggling to breathe out the co2- causing acidity
-it cld be COPD
Case 1
* pH - 7.33 - low, so acidosis
* pO2 - 9.6 kPa - low
* pCO2 - 6.7 kPa - high, respiratory indicator
HCO3- - 32 mmol/L - high metabolic alkalinity is trying to compensate high pCO2
Patient super overexcited screaming after concert
* pH - 7.46
* pO2 - 12 kPa
* pCO2 - 3 kPa
HCO3- - 20 mmol/L
what is the diagnosis
respiratory alkalosis
as a result of hyperventilating so patient may have passed out
causes cld be
-emphysema/pneumonia
-extreme anxiety,stress or pain
-elevated body temp
-overventilation from ventilator
Case 2
* pH - 7.46 - high
* pO2 - 12 kPa - is okay
* pCO2 - 3 kPa - low, respiratory indicator
HCO3- - 20 mmol/L - low, not aligned with her alkalosis, kidney trying to improve by acidity
a patient is frequently vomiting. You take arterial blood gas and there results are:
* pH - 7.49
* pO2 - 11 kPa
* pCO2 - 5.9 kPa
* HCO3- - 30 mmol/L
what is likely diagnosis
patient vomiting, losing lots of gastric acid; metabolic alkalosis
- pH - 7.49 - high, so alkalosis
- pO2 - 11 kPa - is okay
- pCO2 - 5.9 kPa - is okay
HCO3- - 30 mmol/L - high, so metabolic
