Fluid prescription Flashcards
When should IV fluids be prescribed?
- Only for patients whose needs cannot be met by oral or enteral routes.
- Where possible oral fluid intake should be maximised and IV fluid only used to supplement the deficit.
- Examples of when IV fluids may be required:
*A patient is nil by mouth (NBM) for medical/surgical reasons (e.g. bowel obstruction, ileus, pre-operatively)
*A patient is vomiting or has severe diarrhoea
*A patient is hypovolaemic as a result of blood loss (blood products will likely be required in addition to IV fluid)
What can IV fluids be categorized into?
- Two major categories depending on constitution: Crystalloids and colloids
- For indication, 5Rs: Resuscitation, Routine maintenance, Replacement, Redistribution, Reassessment
What are crystalloids?
solutions of small molecules in water (e.g. sodium chloride, Hartmann’s, dextrose)
What are colloids?
solutions of larger organic molecules (e.g. albumin, Gelofusine(succinylated (modified fluid) gelatin and sodium chloride))
What fluid is used most often in patients, colloids or crystalloids?
Colloids are used less often than crystalloid solutions as they carry a risk of anaphylaxis and research has shown that crystalloids are superior in initial fluid resuscitation
Commonly used IV fluids and characteristic and use
- Normal saline (sodium chloride 0.9%) (isotonic) (used for resuscitation/maintenance)
- Hartmann’s solution (isotonic) (used for resuscitation/maintenance)
- NaCl 0.18% / Glucose 4% (hypotonic) (used for maintenance)
- 5% dextrose (hypotonic) (used for maintenance)
Findings suggestive of hypervolemia
- Increased respiratory rate (>20 breaths per minute)
- Decreased oxygen saturations
- Bilateral crackles on auscultation
- Hypertension
- Elevated JVP
- Increased urine output
- Abdominal distension (ascites) and peripheral oedema
- A fluid chart showing a positive fluid balance
- Weight gain
Findings suggestive of hypovolaemia (circulation assessment)
- Increased heart rate (>90 bpm)
- Hypotension (systolic BP <100 mmHg)
- Prolonged capillary refill time
- Non-visible JVP
- Decreased GCS may be noted if the patient is significantly volume depleted
- Increased output from wounds and drains
- Cool peripheries
- Prolonged capillary refill time (>2 secs)
- Decreased urine output (<30mls/hr)
- A fluid chart showing a negative fluid balance
- Weight loss
- Other sources of fluid loss (e.g. rectal bleeding, diarrhoea, vomiting)
What needs to be done to decide which fluids to prescribe to a patient?
- The initial assessment involves assessing the patient’s likely fluid and electrolyte needs from their history, clinical examination and available clinical monitoring (e.g. vital signs, fluid balance). Your clinical examination and review of available clinical monitoring should be performed using the ABCDE approach, with a focus on the patient’s fluid status.
- If after your initial assessment you feel there is evidence of hypovolaemia your next step would be to initiate fluid resuscitation as shown in the next section. If however, the patient appears stable and normovolaemic you can skip this step and move straight to calculating maintenance fluids. If you consider the patient to be hypervolaemic, do not administer IV fluids
Things to note in history of a patient when deciding to prescribe fluids
- Fluid intake:
Assess if the patient’s fluid intake been adequate. - Symptoms suggestive of dehydration:
Thirst
Dizziness/syncope - Fluid loss:
Vomiting (or NG tube loss)
Diarrhoea (including stoma output)
Polyuria
Fever
Hyperventilation
Increased drain output (e.g. biliary drain, pancreatic drain) - Co-morbidities:
Heart failure
Renal failure
Resuscitation fluids indication
If the patient has clinical signs suggestive of hypovolemia you need to prescribe some resuscitation fluids in addition to considering the cause of the deficit and appropriate actions to treat it (e.g. patient is septic so antibiotics need to be administered)
How to give resuscitation fluids
1- Initiate fluid bolus: Administer an initial 500 ml bolus of a crystalloid solution (e.g NaCl 0.9%/Hartmann’s solution) over less than 15 minutes
2- Reassess the patient:
2a After administering the initial 500 ml fluid bolus you should reassess the patient using the ABCDE approach, looking for evidence of ongoing hypovolaemia as you did in your initial assessment (if you find yourself unsure about whether any further fluid is required you should seek senior input)
2b If the patient still has clinical evidence of ongoing hypovolaemia give a further 250-500 ml bolus of a crystalloid solution, then reassess as before using the ABCDE approach:
- You can repeat this process if there is ongoing clinical evidence suggestive of the need for fluid resuscitation up until you’ve given a total of 2000 ml of fluid.
- If despite giving 2000ml you reassess and find there is still an ongoing need for fluid resuscitation (i.e. persistent hypovolaemia), you should seek expert help.
- If patients have complex medical comorbidities (e.g. heart failure, renal failure) and/or are elderly then you should apply a more cautious approach to fluid resuscitation (e.g. giving fluid boluses of 250 ml rather than 500 ml and seeking expert help earlier).
- IV Fluids may worsen the situation (e.g. in cardiogenic shock with overloading)
- If the patient appears normovolaemic but has signs of shock you should seek expert help immediately.
Similarly, the very elderly/frail (particularly if they are small) can be prone to overload so consider small boluses in these patients
If unsure if fluid deplete, raising their legs can artificially fluid resuscitate a patient. This may improve their observations & clinical exam findings suggesting fluid bolus will be helpful
Fluids in patient hemodynamically stable
- Daily fluid and electrolyte requirements can be considered.
- You should review the patient as discussed in the initial assessment section, but also review key laboratory results to better understand the patient’s current fluid and electrolyte status:
History
Clinical examination
Clinical monitoring
Laboratory monitoring (e.g. electrolytes/renal function/haemoglobin) - Once you have collected the above information you need to decide if you feel the patient can meet their fluid and/or electrolyte needs orally or enterally
- If the patient is able to meet their fluid and/or electrolyte needs orally/enterally then no further IV fluids should be required
- If the patient is unable to meet their fluid and/or electrolyte needs orally/enterally (e.g. complex fluid issues, electrolyte replacement issues, abnormal fluid distribution issues) the those patients will likely require fluid replacement and/or redistribution. Those patients who do not have any of the above issues but are unable to meet their fluid requirement should receive routine maintenance IV fluids
Daily maintenance fluid requirements
25-30 ml/kg/day of water and
approximately 1 mmol/kg/day each of potassium, sodium and chloride and
approximately 50-100 g/day of glucose to limit starvation ketosis (however note this will not address the patient’s nutritional needs)
Prescribe maintenance fluids for an 80kg male for a 24 hour period
25-30 x 80 kg = 2-2.5L fluid
80 mmol each of Na/K/Cl
50-100g glucose i.e. 1-2L of 5% dextrose/glucose
It is easier to prescribe 1L bags rather than be exact and correct daily based on a fluid review. Thus, of the approximately 3L needed we can give 2x 1 litre of 5% glucose and then one litre of any salt solution (0.9% sodium chloride, Hartmann’s or PlasmaLyte). This can run 8 hourly or 6 hourly to give the patient a break. This overshoots the sodium requirement, but that will practically always occur and will be filtered out.
