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Fluid Administration

Fluids are not benign, harmless substances that can be administered without thought or care

They MUST be thought of as any other drug

  • Ensure correct indication

  • Ensure correct dose and rate

  • Monitor for a response

  • Never just 'Set and Forget!'

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Indications:

  • Fluid Resuscitation

  • Water supplementation​​

  • Electrolyte/glucose/nutrient supplementation

  • Drug administration

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General Features

General Features
Fluid Resuscitation
Maintenance Fluid Administration
General Features

Preparations:

  • Crystalloids

    • Composed of water and electrolytes​

    • May be isotonic or hypotonic

      • Isotonic fluids distribute throughout extracellular fluid space only​

        • 25% will remain within intravascular space​

      • Hypotonic fluids will distribute throughout all fluid compartments

        • 8% will remain within intravascular space​

    • Preparations:

      • 0.9% sodium chloride solution

      • Compound sodium lactate (Hartmanns)

      • 5% Dextrose solution

      • Plasmalyte

  • Colloids

    • Composed of water, electrolytes and large non-diffusable molecules​

    • Theoretical mechanism of maintaining fluid within intravascular space for longer

      • Actual effect likely not large​

      • No morbidity/mortality benefits born out in studies

    • Preparations

      • Blood products

      • 4% Albumin solution​

      • Gelofusine

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A note about CSL:

The lactate contained within CSL solution is the lactate ion without the hydrogen ion

CSL will NEVER contribute to a lactic acidosis, although it may falsely elevate the measured lactate (uncommon)

Lactate is metabolised by the liver; in the presence of significant hepatic impairment, excessive CSL may cause a normal anion-gap metabolic acidosis in a similar way as 0.9% NaCl does normally

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  • Other Intensive Care Assessments​

    • Real-time TTE

      • Measurement of cardiac output following fluid administration​

    • Pulse pressure variation​ or stroke volume variation

      • Requires invasive arterial monitoring​ and mechanical ventilation

      • Use of heart-lung interactions to detect volume responsiveness

        • During positive pressure inspiration, intra-thoracic pressure increases, leading to reduced venous return

        • The lower on the Starling curve a patient is, the more that stroke volume/pulse pressure will vary with phases of ventilation​

        • Stroke volume is determined via arterial waveform analysis using proprietary algorithms

      • A 10% or larger variation through the respiratory cycle may be suggestive of fluid responsiveness

        • As a patient inspires, they generate negative intra-thoracic pressure, increasing venous return to the right heart​

      • Not valid if:​

        • Spontaneous breathing or small tidal volumes​

        • Open chest

        • Sustained arrhythmias

How to Fluid Resuscitate

  1. Identify that the patient has inadequate cardiac output

  2. Identify that the patient is fluid responsive

  3. Administer fluid

    • Initially, 20 - 30 ml/kg​ (including fluid challenge)

    • If unsure, give 500 ml aliquots at a time; you can always give more

    • Should be administered quickly

    • Use isotonic crystalloid solution

      • Hypotonic solutions are not appropriate resuscitation fluids (eg. 5% dextrose)​

      • Colloid solutions are second line fluids and are not indicated in the first instance except in the case of haemorrhagic shock, which calls for blood products

  4. Closely monitor patient response to treatment

  5. Continue to assess underlying aetiology of inadequate cardiac output

  6. Continue further fluid administration if appropriate

  7. Cease fluid administration if:

    1. Patient achieves adequate cardiac output

    2. Patient ceases to be fluid responsive

    3. Source of inadequate cardiac output is identified that requires alternative management

    4. Patient suffers adverse effects of fluid therapy

Fluid Resuscitation

Fluid Resuscitation

Goals of Fluid Resuscitation

  • The only goal of fluid resuscitation is to increase left ventricular cardiac output!

    • ​Increased venous return to the right ventricle leads to increased right ventricular cardiac output, leads to increased venous return to the left ventricle, leads to increased left ventricular stroke volume, leads to increased left ventricular cardiac output​

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Indications for Fluid Resuscitation

  • The ONLY indication for fluid resuscitation is a patient who has inadequate cardiac output AND is fluid responsive

    • Fluid resuscitation is not indicated for a patient who is fluid responsive but does not have inadequate cardiac output

    • Fluid resuscitation is not indicated for a patient who has inadequate cardiac output​ but is not fluid responsive

  • On their own, hypotension or oliguria (or any other individual sign or symptom) ARE NOT indications for fluid resuscitation unless they fit within the context of an assessment that has determined that the patient has inadequate cardiac output

  • Fluid resuscitation is appropriate initial treatment for almost all causes of undifferentiated inadequate cardiac output 

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Fluid Responsiveness

  • Fluid resuscitation should only occur in patients who are fluid responsive

  • Fluid responsiveness refers to the physiologic phenomenon by which increased ventricular filling causes increased ventricular contractility, leading to a larger volume of blood ejected with each contraction

    • This describes a patient who is operating on the steep part of the Starling curve​

    • At a particular point, a further increase in ventricular volume does not increase the ejected volume

  • Fluid Responsiveness Assessment

    • Fluid challenge​

      • Administer 500ml fluid bolus OR perform passive leg raise (500ml auto-bolus)​

        • When performing passive leg raise, ensure patient's head and trunk remains at 90 degrees (parallel to the floor).

        • Do not simply tilt patient head down as abdominal compression of the vena cava will obstruct venous return​

      • Monitor for signs of improved cardiac output

Maintenance Fluid

Maintenance Fluid

Maintenance fluid is indicated for water and electrolyte supplementation in a patient with inadequate enteral intake

Daily Requirements:

  • Water: 20 - 30 ml/kg/day

    • This may be significantly altered by pathology or critical illness​

  • Sodium: 1 - 2 mmol/kg/day

  • Potassium: 1 - 1.5 mmol/kg/day

  • Chloride: 1 mmol/kg/day

 

Prescribing maintenance fluids

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Ward Patients

  • Administer full requirements over 24 hour period

    • Titrate total dose to patient's enteral intake​ (ie. if some intake, reduce total amount)

    • Careful use in patients with heart, liver or renal failure

      • Use smaller volumes and more frequent assessment​

  • Choice of fluid and additives should be individualised to specific patient

  • All patients receiving maintenance fluids require regular fluid assessment

    • Never just 'set and forget'​

  • Example of 24 hour fluid regime in a fasting patient:

    • 1L 0.9% NaCl + 30 mmol KCl​

    • 1L 5% dextrose + 30 mmol KCl

    • +/- 1L 5% dextrose

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Critical Illness

  • Usually require significantly less fluid administration

    • Critical illness and stress response activates fluid retention systems (renin-angiotensin-aldosterone system, ADH, cortisol, etc.)​

    • Patients may receive significant volumes of fluid via medication administration and infusions

    • Often, intermittent assessment and fluid bolus may be more appropriate than continuous fluid infusions​

  • Maintenance fluid should only be commenced in patients with significant ongoing fluid losses AND who are assessed as hypovolaemic

       Authors: Ryan Slack Peer Reviewer: Irma Bilgrami, Date: 02/04/20

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