Guidance for Intravenous fluid and electrolyte prescription in adults

Euvolaemic: veins are well filled, extremities are warm, blood pressure and heart rate are normal (depending on other pathology).

Hypovolaemic: patient may have cool peripheries, respiratory rate > 20, systolic bp < 100mmHg, HR>90bpm, postural hypotension, oliguria and confusion. History of fluid loss or low intake. May respond to 45˚ passive leg raise. Does blood pressure go up when patient placed in head down position?

Signs of hypovolaemia can be unreliable in elderly patients.
Consider a urinary catheter in sick patients for output monitoring.

Remember patients can be overloaded/oedematous but still require fluid to expand their intravascular space.

Hypervolaemic: Patient may be oedematous. May have inspiratory crackles, high JVP and history/charts showing fluid overload. 

ALLOW PATIENTS TO DRINK IF AT ALL POSSIBLE

NO:   Drinking adequately.
         Receiving adequate fluid via NG feed or TPN.
         Receiving large volumes of fluid with drugs or drug infusions (or a combination of these).
         Hypervolaemic: may need fluid restriction or gentle diuresis.

YES:  Not drinking, reduced oral intake
         Has lost or is losing fluid.
         Nil by Mouth (unsafe swallow, reduced GI motility, pre/past op) Drowsy

So WHY does my patient need IV fluid?
Commence Accurate Fluid Balance

Maintenance fluid only. Patient does not have excess losses above insensible loss. If no other intake they need approximately 30ml/kg/24hrs. They may only need part of this if receiving other fluid. See Table 1.
Patients who might fast for over 8 hours should be started on IV maintenance fluid.

Replacement of losses, either previous or current. If losses are predicted replace later rather than give extra fluid in anticipation of losses which may not occur. This fluid is in addition to maintenance fluid. Check blood gases and U&E including Chloride.

Resuscitation: The patient is hypovolaemic as a result of dehydration, blood loss or sepsis and requires urgent correction of intravascular depletion to correct the deficit.

(a) Obtain weight *. Estimate if necessary:
      men: weight (kg) = height (cm) - 100
      women: weight (kg) = height (cm) - 105
*use ideal weight to calculate fluid requirements as adipose tissue is inert with aminimal fluid requirement.
Lean body mass plateau’s-
      -80kg for women
      -90kg for men.

Maintenance fluid requirement approximately 30ml/kg/24hrs. (Table 1).
see note in section 4 regarding the elderly.

(b)  Review recent U&Es, other electrolytes and Hb, albumin

(c)  Take into account recent history/events – e.g. fasting, input/output, sepsis,medications, operations, fluid  overload. Check accurate fluid balance charts. Calculate how much loss has to be replaced and work out which type of fluid has been lost: e.g. GI secretions, blood, inflammatory losses. Plan to replace that over 12-48 hours.

Note: urine volume does not need to be replaced unless excessive (diabetes insipidus, recovering renal failure).
Post-op: high urine output may be due to excess fluid; low urine output is common and may be normal due to anti-diuretic hormone release.

Assess fully before giving extra fluid.

MAINTENANCE FLUID
Maintenance IV fluid should be given via volumetric pump.

Always prescribe as ml/hr not ‘x hourly’ bags.
Never give maintenance fluids at more than 100ml/hour.  - Do not "speed up" bags - instead give replacement for losses.
Table 1: Maintenance Fluid Requirement

For frail, elderly patients with renal impairment or cardiac failure and patients who are malnourished or at risk of re-feeding syndrome, consider giving less fluid: 20-25ml/kg/day (NICE guidelines). Consult a senior doctor for fluid advice. Give Pabrinex IV if at risk of re-feeding syndrome.

Preferred maintenance fluids:
0.18%saline/4% Glucose, with or without added potassium KCl 40mmol/L.
Give KCl 40 mmols/L unless K+ >/= 5.0mmol/L.

• Prescribe each 1000ml bag with added potassium (KCl 40mmol) if patient has normal or low potassium. Aim to give about 1mmol/kg/day of K+.
• If the serum potassium is above 5.0mmol/l or rising quickly do not give potassium containing fluids.
• Patients with renal failure - consult senior doctor.

This fluid if given at the correct rate (Table 1) provides all water, Na+ and K+
requirements until the patient can eat and drink or be fed.

Excess volumes of this fluid (or any fluid) may cause hyponatraemia.
If sodium is < 132mmol/L: get senior clinician input.
Use Plasmalyte148 for maintenance. DO NOT use 0.45% saline with 4% Dextrose.
If sodium is < 120mmol/L this is a medical emergency. High concentrations of saline may be required.

REPLACEMENT FLUID
Fluid losses may be due to diarrhoea, vomiting, fistulae, drain output, bile leaks, high stoma output, ileus, blood loss, excessive sweating or excess urine. Inflammatory losses (redistribution) in the tissues are hard to quantify and are common in pancreatitis, sepsis, burns and abdominal emergencies.

It is vital to replace high gastro-intestinal (GI) losses. Patients may otherwise develop severe metabolic derangement with acidosis or alkalosis and hypokalaemia.

Hypochloraemia occurs with upper GI losses. Check blood gases in these patients and request chloride with U&Es.
Urinary and insensible losses are covered by the maintenance part of the prescription. In the recovery phase patients start to pass more urine as they mobilise excess fluid.

Hyponatraemia is common. In the absence of large GI losses, causes are
too much fluid, SIADH or chronic diuretic use. Treatment of hyponatraemia is complex and requires senior input. A sodium of <125mmol/L is dangerous. 0.9% NaCl + KC

Potassium replacement A potassium level in the normal range does not mean that there is no total body potassium deficit. Give K+, if clinically indicated, in maintenance fluid. Potassium-containing fluids must be given via a pump.

Outside of ITU: the potassium content of IV fluids must not exceed 40mmol/L and it must not be given at a rate greater than 10mmol/hour. There may be occasional exceptions to this – refer to the Potassium Chloride IV drug monograph.

In ITU: potassium can be given neat - KCl (2mmol/ml) via a central line at a maximum rate of 10 ml/hr (20mmol/hr). ECG monitoring is recommended. Occasionally it may also be necessary to administer this in a Level 1 HDU area. This must be under the instruction of a senior clinician, given by a central venous catheter and under continuous ECG monitoring.

Estimate replacement fluid/electrolyte requirements (see table 2) by adding up all the losses over the previous 24 hours and give this volume as Plasmalyte 148

Use 0.9% NaCl with KCI for upper GI or bile loss (high NaCl content). Otherwise avoid it as it causes fluid retention.

Diarrhoea may lead to potassium loss.
Normal plasma osmolality is 285-295 mosm/l.

Table 2: Normal volumes of secretions and their electrolyte contents

• Take your time; consult senior clinician if you are unsure.
• Patients on IV fluids need regular blood tests.
• Patients should be allowed food and drink ASAP.

Escalate to senior clinician responsible for patient, Critical Care Outreach and consider Critical Care referral if:

• Persistent hypotension and/or oliguria unresponsive to 2000ml fluid, or concern over cardiac function
• Metabolic acidosis: base deficit -8 or worse, bicarbonate < 18mmol/L, lactate>3mmol/L and not improving in 2 hours

Critical care referral is not always appropriate – consult senior doctor.