Fluid and electrolyte therapy

Question 1

Colloids

Common indications

Answer 1

1. Colloids are used to expand circulating volume in states of cirulatory compromise (including shock), however we prefer crystalloid formulaiton (e.g. saline) for this indication
2. In cirrhotic liver disease- albumin is used to prevent effect hypovolaemia in large-volume paracentesis (ascitic fluid drain)

Question 2

Colloids

MOA

Answer 2

• Colloid is a solution containing a large osmotically active molecule such as albumin
• Large moleclues can’t readily diffuse out of vessels and their osmotic effect hold infused fluid in the plasma
• In practice most people requiring fluid resus have leaky capilaries (sepsis) in which albumin would diffuse out anyway
• Large-volume paracentesis (>5L of fluid) in cirrhotic liver disease can produce adverse haemodynamic effects
• It is customary to administer HAS (human albumin solution) to prevent this

Question 3

Colloids

Adverse effects

Answer 3

• Excessive administration of colloid fluids may cause a fall in cardiac output and precipitate cardiac failure by increasing L-ventricular filling beyond max contractility on the starling curve
• Most colloids contain a significant amount of sodium (e.g. 154 mmol/L) and this may produce oedema

Question 4

Colloids warnings

Warnings

Answer 4

• Fluid volume should be reduced in patient with HF due to risk of worsening myocardial contractility
• In renal impairment, it is vital to monitor fluid balance closely to avoid overload

Question 5

Colloids

Communication and administration

Answer 5

• Explain that you are offering treatment with a drip because they are unable to take enough PO
• As appropriate encourage the Pt to drink more
• Report any irritation, swelling or wetness
• Cirulatory compromise: Haemodynamic status (pulse, BP, JVP, CRT, UO) before and after therapy

Question 6

Glucose

Common indication

Answer 6

1. Provide water IV to patients who can not take enough PO (orally)
2. Treat hyperglycaemia when severe or no oral tolerability (10,20 and 50%)
3. Used with insulin to treat hyperkalaemia, Calcium gluconate may also be given acts as a caridac stabiliser (Shift K+ into cells, remove K from body)
4. Reconstitution and dilution of drugs intended for administration by injection or infusion

Question 7

Glucose

MOA

Answer 7

• 5% solution- simple means of providing water IV. Formulation is isotonic and prevents osmolysis
• High concentration can be used for hypoglycaemia,
• In hyperkalaemia insulin (actrapid normally) is given to stimulate Na/K/ATPase and shift potassium into the cells, with the glucose used to prevent hypoglycaemia

Question 8

Glucose

Adverse effects

Answer 8

• Glucose 50% is highly irritating to veins and may cause local pain, phlebitis and thrombosis therefore can only be given via a central line
• Hyperglycaemia will occur if glucose administration exceeds its utilisation (which is most likely in patients with diabetes mellitus)

Question 9

Glucose

Warnings

Answer 9

• In patients at risk of thiamine deficiency, giving IV glucose can cause Wernicke’s encephalopathy
• If IV glucose treatment is needed, thiamine (pabrinex) must also be given
• In renal failure, close monitoring of fluid balance is essential to avoid overload
• Administering a significant volume of hypotonic fluid to a patient with hyponatreamia (more susceptible in kids) may precipitate hyponatraemic encephalopathy

Question 10

Glucose

Important interactions

Answer 10

• Glucose and insulin have an antagonistic effect, be careful in diabetics on insulin therapy
• Concurrent use may be required

Question 11

Potassium IV

Common indication

Answer 11

1. For prevention of potassium depletion in patients unable to take adequate amounts orally
2. For treatment of established potassium depletion and hypokalaemia that is severe (<2.5mmol/L), symptomatic or causing arrhythmias

Question 12

Potassium IV

MOA

Answer 12

• The normal potassium requirements to prevent depletion is ~1mmol/kg/day in adults
• In patients unable to tolerate dietary intake, who instead receive Na + H20 IV they need K supplementation
• K depletion and hypokalaemia may be caused by diarrhoea, vomiting or 2’ hypoaldosteronism
• Hypokalaemia can result in arrhythmias, muscle weakness, paralysis and death
• IV K should be given with glucose as -ve charged ION (Cl-) cause greater retention of K+ in serum. Where as glucose stimulates insulin which promotes K into the cell

Question 13

K

Adverse effects

Answer 13

• Hyperkalaemia- arrhythmais
• Irritant to veins

Question 14

IV K

Warnings

Answer 14

• It is unnecessary and potentially dangerous to prescribe potassium for the prevention of K depletion in pts with renal impairment or oliguria (susceptible to hyperkalaemia)
• Extreme caution should be exercised when giving K to these patients

Question 15

IV K

Interactions

Answer 15

• Additive effect with other Potassium Elevating Drugs
  
  • E.g. Oral potassium, aldosterone antagonist, K-sparing diuretic, ACEI and ARBs

Question 16

IV K

Communication and monitoring

Answer 16

• Tell Pts that they will need close monitoring and regular blood tests
• regulalry U&Es are required on a daily basis
• ECG- arrhythmias
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