WATER, ELECTROLYTES AND ACID BASE BALANCE

Question 1

Average total body water in L?

Answer 1

42L

Question 2

Volume of water intravascular?

Answer 2

3L

Question 3

Main intracellular and extracellular ion?

Answer 3

Intracellular - potassium

Extracellular - sodium

Question 4

Hydrostatic pressure?

Answer 4

Intercapillary blood pressure

Question 5

Oncotic pressure?

Answer 5

Pressure exerted by plasma proteins

Question 6

Causes of oedema?

Answer 6

Increased hydrostatic pressure

Decreased oncotic pressure

occluded lymphatics

Increased vascular permeability

Question 7

Difference between crystalloids and colloids?

Answer 7

Crystalloids - sodium chloride and contains low molecular weight molecules completely dissolved and moves freely between interstitium and intravascular

Colloids - contain larger molecular weight substance and has a longer-lasting effect - Haemorrhage, burns and sometimes septicaemia

Question 8

What determines effective arterial blood volume?

Answer 8

Cardiac output and peripheral vascular resistance

Question 9

Loop diuretics?

Answer 9

FUROSEMIDE

Decrease sodium and chloride reabsorption in the ascending loop of Henle

Question 10

Thiazide Diuretic?

Answer 10

HYDROCHLOROTHIAZIDE

Decreased reabsorption of sodium in the distal convoluted tubule but associated with hypercalcaemia

Question 11

Aldosterone antagonist?

Answer 11

SPIRONOLACTONE

Inhibits the effects of aldosterone

Question 12

Potassium sparring Diuretics?

Answer 12

AMILORIDE

Not the strongest diuretics but prevents the exchange of sodium for potassium in the distal tubule

Question 13

Calculated plasma osmolatlity?

Answer 13

(2x plasma sodium) + (urea) + (glucose)

Question 14

Normal range of plasma osmolarity?

Answer 14

285 - 300 mosmol/kg

Question 15

Where are osmoreceptors found?

Answer 15

Hypothalamus

Question 16

Range of serum sodium?

Answer 16

135 to 145

Question 17

Causes of hypernatraemia?

Answer 17

Reduced water intake or increased water loss

increased administered sodium

Elderly, neonates or comatose patients not given enough fluids

Question 18

Management of hypernaetraemia?

Answer 18

Dextrose

Question 19

Types of hyponaetraemia?

Answer 19

Hypovolaemia - lose both water and sodium but more sodium

Dilutional - Excessive body water in relation to sodium by over-generous infusion of 5% glucose in post op patients

Question 20

At what sodium level does hyponatraemia show symptoms?

Answer 20

<120mmol/L

Question 21

symptoms of hypernatraemia?

Answer 21

Nausea, vomiting, fever or confusion

Question 22

Symptoms of hyponaetramia?

Answer 22

Muscle spasma and weakness

irritability

Nausea

Headache

Seizures

Question 23

Range of potassium?

Answer 23

3.5 to 5 mmol/L

Question 24

What can increase potassium?

Answer 24

Lysis or RBC or abnormal RBC disorders

Renal impairment of K excretion or drugs that interfere with this process

Question 25

Clinical features of high potassium?

Answer 25

Muscle spasms and paralysis Metabolic acidosis with kussamals respiration - low deep sighing inspiration and expiration ECG - Tall T wave, reduced P wave, wide QRS and since wave which is pre-cardiac arrest

Question 26

Causes of decreased potassium?

Answer 26

Diuretics and hyperaldosteronism

Question 27

Symptoms of low potassium?

Answer 27

Asymptomatic unless severe Cardiac arrhythmia, muscle weakness or predisposed digoxin toxicity

Question 28

Increased magnesium?

Answer 28

Rare and iatrogenic - renal patients given medication containing magnesium Causes neruo, cardiac and reps depression Stop the **Mg treatment, IV calcium gluconate** (relieve toxic effects of too much Mg), **Dextrose**

Question 29

Low magnesium?

Answer 29

Loss of serum magnesium from the Gut or kidneys - severe diarrhoea, malabsorption, bowel resection or intestinal resection Or diuretics, alcohol or osmotic stress - glycosuria in DM - Causes low calcium and potassium, inhibits the secretion of PTH and leads to PTH resistance

Question 30

Buffers of H+?

Answer 30

Haemoglobin proteins Bicarbonate Phosphate

Question 31

The enzyme used in acid-base conversions?

Answer 31

Carbonic anhydrase

Question 32

Respiratory acidosis?

Answer 32

Retention of CO2 due ventilatory failure

Question 33

What does the white box of the flenley acid-base nomogram show?

Answer 33

The approximate limits of arterial pH and PCO2 in normal individuals

Question 34

Respiratory alkalosis?

Answer 34

Hyperventilation so lots of CO2 is removed

Question 35

Metabolic acidosis?

Answer 35

Accumulation of any acid e.g. lactic acid Hyperventilation, hypertension, cerebral dysfunction - confusion and fits Anion gap normally 6 to 12 - if normal in the presence of acidosis - HCL being retained or NaHCO3 is being lost and if anion gap is greater then it is due to exogenous acid lactic acidosis (septicemic and cardiogenic shock), DKA (ketones), Renal tubular acidosis (Failure of the kidneys to acidity urine), Uraemic acidosis (reduced capacity to excrete H+ and NH4+)

Question 36

Metabolic alkalosis?

Answer 36

Associated with potassium or volume depletion D, V, Diuretic use or hyperaldosteronism Cerebral dysfunction and respiratory depression Replace with fluids