Acid Base Balance

Question 0

What is acid base balance and why is it important

Answer 0

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.

Question 1

Normal pH in arterial blood

Answer 1

7.35 - 7.45 (slightly alkaline)

or can be reported as hydrogen ion level: 35 - 45 nmmol/l

Question 2

Regulation of pH is by 3 systems

Answer 2

1. Buffer system
2. Respiratory system
3. Renal system

Question 3

Examples of buffers

Answer 3

haemoglobin
phosphates
plasma proteins
carbonic acid-bicarbonate system

Question 4

What are buffers

Answer 4

Weak acids or bases that change strong acid or acid or alkali into weaker ones

Question 5

function of buffer systems

Answer 5

Resist pH changes by replacing strong acids with weaker one
1st line defence
Work instantaneously but short term measure only

Question 6

The most important organ system involved in the control of hydrogen ions

Answer 6

The Respiratory system

Question 7

Function of the respiratory system in the control of ph

Answer 7

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

Question 8

If alveolar ventillation falls PaCo2 —–

Answer 8

rises

Question 9

If alveolar ventilation rises PaCo2 ——-

Answer 9

falls

Question 10

The partial pressure of — and —- controls ventilation

Answer 10

Co2 and H2

Question 11

Renal regulation of pH is achieved by:

Answer 11

Excretion of hydrogen ions

Reabsorption of bicarbonate

Question 12

Respiratory acidosis occurs when

Answer 12

hypoventilation causes retention of Co2 leading to excess carbonic acid and Hydrogen io > 45 nmol/l

ph down, PaCo2 up
Retention of Co2

Question 13

Causes of respiratory acidosis

Answer 13

1. Respiratory causes - asthma, pneumonia, PE, COPD, airway obstruction, under-ventilation with a mechanical ventilator
2. Non respiratory causes - Pain, spinal cord injury and Altered conscious state eg due to opiates,excess alcohol, head injury, brain tumour, sedation

Question 14

Symptoms of respiratory acidosis (CAPtin M)

Answer 14

altered mental state
tachycardia
peripheral vasodilation
Muscle twitching
cardiac arrythymias

Question 15

Respiratory alkalosis occurs when

Answer 15

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

Question 16

Symptoms of respiratory alkalosis (PIAS)

Answer 16

parathesia and numbness, impaired consciousness, arrythmias and siezures

Question 17

Causes of respiratory alkalosis

Answer 17

anxiety states
conditions that cause hypoxia eg shock, early sepsis, pulmonary disease
brain stem injury
over ventilation with a mechanical ventilator

Question 18

Metabolic acidosis occurs when

Answer 18

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

Question 19

Causes of metabolic acidosis

Answer 19

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.

Question 20

symptoms of metabolic acidosis (HFRAD)

Answer 20

headache
fatigue
reduced conscious level
arrythmias
deep respirations

Question 21

Metabolic alkalosis is less common than other acid base imbalances and occurs when

Answer 21

there is an excess of bases or deficit of acids in the body leading to ph > 7.45 (hydrogen

Question 22

Causes of metabolic alkalosis

Answer 22

Severe vomiting or diarhohea
Loop diuretics eg frusssemide
excessive ingestion of antacids

Question 23

Symptoms of metabolic alkalosis (WCCR)

Answer 23

Weakness
Confusion and convulsions
reduced respiratory rate

Question 24

Two type of compensation-

Answer 24

1. 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.

Question 25

What is acid base balance and why is it important

Answer 25

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.

Question 26

What are buffers

Answer 26

Weak acids or bases that change strong acid or alkali into weaker ones