Manual calculation – guidance

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Centre for Sustainable Delivery

Manual calculation – maintenance therapy

Suggested maintenance fluid for majority of patients is 0.18% sodium chloride/4% glucose with potassium chloride (40mmol in 1000ml). This will meet the patient requirements of water, sodium, potassium and glucose.

Excessive volumes of this fluid may cause hyponatraemia.

Obtain patients weight in kg.
Maintenance fluid requirement is 30ml/kg/24hr (reduce to 20 ml/kg/24hr in frailty).
Calculate daily glucose and electrolyte requirements - see table below.
'Check input from other sources e.g. nasogastric feed, IV medications etc. If the daily requirements are not being met, then consider additional IV fluid therapy. Remember to subtract any fluid intake from the maintenance fluid requirement calculated in point 2.
Review daily U&Es, additional electrolytes and Hb.

Electrolyte requirements for maintenance

Electrolyte	Requirement
Sodium	1 mmol/kg/24 hrs
Potassium	1 mmol/kg/24hrs (give 40mmol potassium in 1L maintenance fluid)
Glucose	1g/kg/24 hrs to minimise starvation ketosis (1L 0.18%NaCl 4% glucose contains 40g glucose)

EXCEPT:

High potassium (>5mmol/l)

Do not give potassium containing fluids → Give 0.18% sodium chloride/4% glucose (Seek senior advice in renal failure).

Low sodium (<=132 mmol/l)

→ Give Hartmanns or other balanced crystalloid for maintenance. Monitor U+Es regularly and consult senior.

Manual calculation - replacement therapy

Add up all the losses over the previous 24 hours from fluid balance chart and give this volume as Hartmanns, other balanced crystalloid, or 0.9% sodium chloride (for vomiting or nasogastric fluid loss.)

Patients require daily reassessment or more frequent if they have high losses.

Electrolyte and other contents of IV fluids (per litre; unless stated, units in mmol/l)

Fluid	Sodium	Potassium	Chloride	Magnesium	Calcium	Other
0.18% sodium chloride 4% glucose	30		30			40g glucose
Hartmanns	131	5	112		2	28 bicarbonate
0.9% sodium chloride	154		154

Sodium replacement

Hyponatraemia is common: in the absence of large gastrointestinal losses the causes are almost always too much fluid. Also consider SIADH, or chronic diuretic use.

Refer to local hyponatraemia guideline

Potassium replacement

For IV replacement on general adult wards: 20mmol of potassium chloride diluted in 500ml 0.9% sodium chloride and given @100ml/hr.

The maximum rate of potassium administration is 10mmol/hr in a ward setting. Patients receiving this do not require cardiac monitoring.

40mmol of KCl may be given in 500ml 0.9% NaCl at no more than 100ml/h. This must be agreed by a senior doctor due to the risk of tissue damage.

Extravasation of potassium is harmful; ensure the cannula is working well and is checked hourly. Do not use fragile veins or veins in the feet.