Assess whether the patient is hypovolaemic.

Indicators that a patient may need urgent fluid resuscitation include:

• systolic blood pressure is less than 100 mmHg
• heart rate is more than 90 beats per minute
• capillary refill time is more than 2 seconds or peripheries are cold to touch
• respiratory rate is more than 20 breaths per minute
• National Early Warning Score (NEWS) is 5 or more
• passive leg raising suggests fluid responsiveness[2].

Additional monitoring of urinary sodium may be helpful in patients with high-volume gastrointestinal losses. (Reduced urinary sodium excretion [less than 30 mmol/l] may indicate total body sodium depletion even if plasma sodium levels are normal. Urinary sodium may also indicate the cause of hyponatraemia, and guide the achievement of a negative sodium balance in patients with oedema. However, urinary sodium values may be misleading in the presence of renal impairment or diuretic therapy.)

If patients need IV fluid resuscitation, use crystalloids that contain sodium in the range 130– 154 mmol/l, with a bolus of 500 ml over less than 15 minutes.

If patients need IV fluids for routine maintenance alone, restrict the initial prescription to:

• 25–30 ml/kg/day of water and
• approximately 1 mmol/kg/day of potassium[3], sodium and chloride and
• approximately 50–100 g/day of glucose to limit starvation ketosis. (This quantity will not address patients' nutritional needs; see Nutrition support in adults [NICE clinical guideline 32].)

When prescribing for routine maintenance alone, consider using 25–30 ml/kg/day sodium chloride 0.18% in 4% glucose with 27 mmol/l potassium[3] on day 1 (there are other regimens to achieve this). Prescribing more than 2.5 litres per day increases the risk of hyponatraemia.

Read:

Fluid selection & pH-guided fluid resuscitation - EMCrit Project