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CDHB

Fluid Management

Fluids

• The body is about 60% water (two-thirds is intracellular, one-third extracellular).
• One-quarter of the extracellular fluid is intravascular and three-quarters is interstitial.
• The main intracellular cation is potassium while the main extracellular cation is sodium.

Normal daily fluid losses (2,500 mL per day)

• Urinary: 1500 mL
• Stool: 300 mL
• Respiratory tract: 200 mL
• Sweat: 500 mL

Normal daily requirements of fluid and electrolytes

• Water: ~2,500 mL
• Sodium: 75 mmol (~1 mmol/kg)
• Potassium: 70 mmol (~1 mmol/kg)

Reasons for increased fluid and electrolyte requirements

• Bleeding
• Vomiting or NG tube drainage: high in chloride, hydrogen and potassium
• Diarrhoea or high output stoma e.g., ileostomy
• Diuresis
• Hyperventilation
• Pyrexia: 200 mL more fluid lost/day for every 1°C increase in body temperature
• Sweating: contains large amounts of sodium

Types of fluids

1. Crystalloids:

   Fluid	Electrolyte Content
   Sodium chloride 0.9%	150 mmol/L Na + Cl
   Sodium chloride 0.9% with 30 mmol/L potassium chloride	150 mmol/L Na + Cl + 30 mmol/L K
   Sodium chloride 0.45%	75 mmol/L Na + Cl
   Glucose 4% sodium chloride 0.18%	30 mmol/L Na + Cl
   Compound sodium lactate	131 mmol/L Na + 112 mmol/L Cl + 5 mmol/L K
   Plasma-Lyte 148™ either with water or glucose 5%	140 mmol/L Na + 98 mmol/L Cl + 5 mmol/L K
   Glucose 4% sodium chloride 0.18% with 30 mmol/L potassium chloride	30 mmol/L Na + Cl + 30 mmol/L K
   Glucose 5%
   Glucose 5% with 20 mmol/L potassium chloride	20 mmol/L K

   Note: Plasma-Lyte™ fluid preparations are not routinely used.

2. Colloid: gelatin succinylated 4%.
3. Blood Products:
   • Red cells.
   • Fresh frozen plasma (FFP).
   • Albumin 4%.

General rules for IV fluids

The elderly and those with renal or cardiac dysfunction have difficulty excreting salt (sodium). It is important to limit the infusion of intravenous fluids, particularly sodium chloride 0.9% in these patients unless they have obvious large losses.

There are no magic formulae for predicting the clinical response to fluid therapy. The effects of any fluid prescription should be reviewed regularly. In patients with major fluid deficits receiving large amounts of fluid, hourly clinical assessment (pulse, BP, JVP, urine output) may be necessary.

Resuscitation fluids

1. Isotonic Crystalloids: use sodium chloride 0.9%.
   • Large volumes required: 1.5 to 3 times the amount of blood lost.
   • Large volumes of sodium chloride 0.9% can cause hyperchloraemic metabolic acidosis, therefore consider changing to compound sodium lactate or Plasma-Lyte 148™.
   • Short half-life (note that only 20% remains in the intravascular space after 2 hours).
2. Colloid: gelatin succinylated 4%.
   • Colloids to be used with caution in septic and anaphylactic/cardiogenic shock but use should be discussed with more senior medical staff in the first instance.
   • Albumin 4% may be used following discussion with senior medical staff.
3. Blood.

   The only fluid available that will carry oxygen! Indicated if the patient is anaemic or haemodynamically unstable as a result of blood loss or in uncontrolled bleeding.

   • Best to use fully typed and cross-matched blood (6 mL EDTA tube; crossmatch takes 30 min if no antibodies found). Group specific uncross-matched blood takes 10 min. Refer to Blood Transfusion Practice.
   • In desperate situations use uncross-matched Group 0 Rh negative blood.
   • Keep blood and patient warm if massive transfusion necessary. If massive transfusion is required, contact the Blood Bank 80310 to activate the Massive Transfusion Protocol.

Maintenance fluids

• IV or subcutaneous fluids if unable to manage with oral or NG fluids.
• Sodium chloride 0.9% or glucose 5%, or glucose 4% and sodium chloride 0.18%, depending on cardiac and renal function and plasma sodium concentration. Avoid IV glucose solutions for patients at risk of refeeding syndrome.
• Daily weighing gives accurate assessment of fluid balance.
• Sodium chloride 0.9% or glucose 5% at 60 to 80 mL/hour. Glucose 4% and sodium chloride 0.18% may also be used. Modifications if:
  • Normal kidney function: use sodium chloride 0.9% 30 mmol/L potassium chloride premix at 60 to 80 mL/hour. No potassium if acute renal failure or potassium >5 mmol/L.
  • Fluid overload: cease all maintenance fluids.
  • Hypernatraemia; sodium >150 mmol/L: give glucose 5% and aim to reduce the sodium level by 8 to 12 mmol/L per 24 hours.
• Prevent or correct any electrolyte imbalance.

Topic Code: 3704