Circulatory compromise

Question 1

Colloids (Plasma substitute)

Common indications

Answer 1

• Colloids are used to expand circulatory volume in states of circulator.y compromise (including shock)
• However, we prefer compound sodium lactate or sodium chloride for this indication
• In Cirrhotic liver disease, albumin is used to prevent effect hypovolaemia in large-volume paracentesis ascites fluid drainage)

Question 2

Colloids (Plasma substitute)

MOA

Answer 2

• In relation to fluid therapy, a colloid is a solution containing a large osmotically active molecule, such as albumin or modified gelatin
• In principle, the large molecule cannot readily diffuse out of vessels, and their osmotic effect ‘holds’ the infused fluid in the plasm.a
• For example, under experimental conditions, 70-80% of a gelatin-based fluid remains in the plasma
• Their effect in expanding circulating volume is therefore potentially greater than that of a crystalloid (e.g. sodium chloride), of which around 20% remains in the plasma after distribution
• In practice, however, most patients requiring volume expansion (e.g. in severe sepsis) have relatively leaky capilaries, and it is likely that some of the gelatin is lost into the interstitium
• There is no convincing evidence that the use of colloids rather than crystalloids improves clinical outcomes, and trials using starch-based colloids have demonstrated harm. We therefore favour crystalloids for this indication
• Large-volume paracentesis (>5L) in cirrhotic liver disease can product adverse haemodynamic effects
• It is customary to adminster human albumin solution (HAS) in an attempt to prevent this, although the evidence supporting this practice is much debated
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Question 3

Colloids (Plasma substitute)

Important adverse effects

Answer 3

• Excessive administration of colloid fluids may cause a fall in cardiac output and precipitate cardiac failure by increasing left ventricular filling beyond the point of maximal contractility on the Starling curve
• Most colloids contain a significant amount of sodium and this may produce oedema
• Gelatins may cause hypersensitivity reactions, including anaphylaxis- another reason to prefer crystalloids, which are non-allergenic

Question 4

Colloids (Plasma substitute)

Warnings

Answer 4

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

Question 5

Colloids (Plasma substitute)

Prescription

Answer 5

• Colloids are prescribed in the infusion section of the drug chart
• Synthetic colloids are generally prescribed by brand name
• You need to specify the volume to be infused and the rate at which it is to be given
• The rate may be described either in mL per hour or as the intended duration for infusion of the total volume
• For example, if deemed appropriate to use a colloid in circulatory compromise or shock, you might prescribe 250mL of Gelofusine to be given over 10 minutes
• In this context of large-volume paracentesis, you should consult with specialist colleagues regarding the need for albumin
• A common regimen is to give 100mL of HAS 20% for every 2L of ascitic fluid drained

Question 6

Colloids (Plasma substitute)

Administration

Answer 6

• Infusions may be adminstered simply through a given set, in which case the flow is controlled with a roller valve and the rate estimated from the number of drips per minute
• Alternatively, and preferably, an infusion pump can be used to control the rate more precisely
• A pressure bag can be applied to help infuse the fluid more rapidly

Question 7

Colloids (Plasma substitute)

Communication

Answer 7

• Explain that you advise treatment with fluid through a drip in order to improve their blood pressure
• Ask the patient to report any irritation, swelling or wetness around the cannula site, as this may indicate that the cannula is no longer functioning correctly

Question 8

Colloids (Plasma substitute)

Monitoring

Answer 8

• Patients requiring expansion of circulating volume are sick and require close monitoring
• It is vital to assess haemodynamic status (e.g. pulse, BP, jugular venous pressure, capillary refill time, urine output) before and after infusion as a guide to further therapy
• Similarly, close monitoring is required in the context of large-volume paracentesis to detect adverse haemodynamic consequences, whether due to ascitic fluid drainage or albumin adminstration

Question 9

Compound sodium lactate (Hartmann’s solution)

Common indications

Answer 9

1. To provide sodium and water intravenously in patients unable to taken enough orally
2. To expand circulating volume in states of circulatory compromise
   
   • This may be done as a fluid challenge, where a selected volume of fluid is infused rapidly
   • Sodium chloride 0.9% and colloids are alternatives

Question 10

Compound sodium lactate (Hartmann’s solution)

MOA

Answer 10

• Compound sodium lactate (more commonly known by its eponymous name Hartmanns) is a balanced salt solution
• Its constituents are designed to mimic serum, at least in terms of electrolytes
• 1L = Na-131 mmol, Cl- 111, K-5, Ca-2 and lactate-29
• In the presence of adequate liver function, the lactate is metabolised to pyruvate and then either glucose or carbon dioxide and water, with the release of bicarbonate in both cases
• The sodium content means it may be used to proved sodium and water IV, and also for the expansion of circulating volume

Question 11

Compound sodium lactate (Hartmann’s solution)

Adverse effects

Answer 11

• Excessive administration of compound sodium lactate can cause a fall in cardiac output and severe heart failure by increasing left ventricular filling beyond the point of maximal contractility on the Starling curve
• Oedema may be caused by providing sodium more rapidly than the patient can excrete it
• This is especially relevant in patients who have received multiple fluid challenges since about 80% of the administered volume will have been lost into tissue fluid
• The main advantages of compound sodium lactate over sodium chloride 0.9% is its lower chloride content
• It is thus less likely to cause hyperchloraemic acidosis

Question 12

Compound sodium lactate (Hartmann’s solution)

Warnings

Answer 12

• Fluid challenge volume should be reduced in patients with heart failure, due to the risk of worsening myocardial contractility in renal impairment, it is vital to monitor fluid balance closely to avoid overload
• Moreover, although the potassium content is low, you should monitor the serum potassium concentration if it is used in this context
• Compound sodium lactate is best avoided in severe liver disease because there may not be sufficient capacity to metabolise lactate

Question 13

Compound sodium lactate (Hartmann’s solution)

Prescription

Answer 13

• Compound sodium lactate is prescribed in the infusion section of the drug chart
• You need to specify the volume to be infused and the rate at which it is to be given
• The rate may be described either in mL per hour or as the intended duration for infusion of the total volume
• For example, in providing sodium IV, you might prescribe 500mL of compound sodium lactate for administration over 4 hours
• This would be equivalent to 66mmol of sodium, covering their daily maintenance requirement
• You would probably also prescribe glucose 5% to provide their remaining water requirement

Question 14

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