Acid Base Balance Flashcards
What is acid base balance and why is it important
Homeostatic mechanism which involves the precise regulation of pH at cellular level, which is paramount for survival. Most biochemical reactions within the body are influence by the pH of their environment. Having a normal acid base balance involves having a normal PaCo2 and HCO3 a well as a normal pH.
Normal pH in arterial blood
7.35 - 7.45 (slightly alkaline)
or can be reported as hydrogen ion level: 35 - 45 nmmol/l
Regulation of pH is by 3 systems
- Buffer system
- Respiratory system
- Renal system
Examples of buffers
haemoglobin
phosphates
plasma proteins
carbonic acid-bicarbonate system
What are buffers
Weak acids or bases that change strong acid or acid or alkali into weaker ones
function of buffer systems
Resist pH changes by replacing strong acids with weaker one
1st line defence
Work instantaneously but short term measure only
The most important organ system involved in the control of hydrogen ions
The Respiratory system
Function of the respiratory system in the control of ph
Small changes in ventilation can have profound effect on ph. Co2 is responsible for majority of H ion produced. Breathing eliminates Co2. H ions decrease with breathe more
H ions increase wen breathe less
If alveolar ventillation falls PaCo2 —–
rises
If alveolar ventilation rises PaCo2 ——-
falls
The partial pressure of — and —- controls ventilation
Co2 and H2
Renal regulation of pH is achieved by:
Excretion of hydrogen ions
Reabsorption of bicarbonate
Respiratory acidosis occurs when
hypoventilation causes retention of Co2 leading to excess carbonic acid and Hydrogen io > 45 nmol/l
ph down, PaCo2 up
Retention of Co2
Causes of respiratory acidosis
- Respiratory causes - asthma, pneumonia, PE, COPD, airway obstruction, under-ventilation with a mechanical ventilator
- Non respiratory causes - Pain, spinal cord injury and Altered conscious state eg due to opiates,excess alcohol, head injury, brain tumour, sedation
Symptoms of respiratory acidosis (CAPtin M)
altered mental state tachycardia peripheral vasodilation Muscle twitching cardiac arrythymias
Respiratory alkalosis occurs when
hyperventilation causes excessive CO2 exhalation which will lead to a reduction in carbonic acid and an increase in PH.
Ph up
Co2 down
too much Co2 eliminated,
hyperventilation
Hydrogen
Symptoms of respiratory alkalosis (PIAS)
parathesia and numbness, impaired consciousness, arrythmias and siezures
Causes of respiratory alkalosis
anxiety states
conditions that cause hypoxia eg shock, early sepsis, pulmonary disease
brain stem injury
over ventilation with a mechanical ventilator
Metabolic acidosis occurs when
there is a failure to remove or buffer excess hydrogen ions, leading to a ph of less than 7.35( hydrogen > 45 nmol/L
pH down, HCO3 down
Bicarbonate deficit
Causes of metabolic acidosis
1.Excess acid production {eg starvation where protein metabolism produces acid, lactic acid production in anaerobic metabolism, sever anaemia, diabetic ketoacidois, severe sepsis}
2. Renal failure leading to inadequate excretion of hydrogen ions
Excessive loss of Hco3
3. Excessive loss of Hco3 due to renal failure or losses into the small bowel
4. Ingestion of acid due to poisoning.
symptoms of metabolic acidosis (HFRAD)
headache fatigue reduced conscious level arrythmias deep respirations
Metabolic alkalosis is less common than other acid base imbalances and occurs when
there is an excess of bases or deficit of acids in the body leading to ph > 7.45 (hydrogen
Causes of metabolic alkalosis
Severe vomiting or diarhohea
Loop diuretics eg frusssemide
excessive ingestion of antacids
Symptoms of metabolic alkalosis (WCCR)
Weakness
Confusion and convulsions
reduced respiratory rate
Two type of compensation-
- Respiratory - happens within minutes
In metabolic acidosis breathing increases in depth and rate
In metabolic alkalosis breathing decreases in depth and rate
Renal compensation:
Respiratory acidosis -Kidneys will retain bicarb to offset acidosis
In respiratory acidosis compensation begins in minutes but may take days to reach max effect
Respiratory alkalosis - Kidneys eliminate bicarb to offset alkalosis.
What is acid base balance and why is it important
Homeostatic precise regulation of pH at cellular level, which is paramount for survival. Most biochemical reactions within the body are influence by the pH of their environment. Having a normal acid base balance involves having a normal PaCo2 and HCO3 a well as a normal pH.
What are buffers
Weak acids or bases that change strong acid or alkali into weaker ones
