IV Fluids Flashcards
2 categories of fluid space
- Intracellular space 2/3
- Extracellular space 1/3
- Intravascular space 20%
- Interstitial space 80%
- Third space
What is third space
- Areas of body that do not normally contain fluid
- Peritoneal cavity (forming ascites)
- Pleural cavity (forming pleural effusions)
- Pericardial cavity (forming percardial effusion)
- Joints (forming joint effusions)
- Also refers to oedema - excessive collection of fluid in interstitial space
Complications of third spacing
Fluid shifting into non-functional third space can come at expense of the intravascular space, causing hypotension and reduced perfusion of tissues
How is fluid balance recorded
All fluid intake and output can be recorded on fluid balance chart
Sources of fluid intake
- Oral fluids
- Nasogastric or PEG feeds
- Intravenous fluids (including IV medications)
- Total parenteral nutrition
Sources fluid output
- Urine output
- Bowel or stoma output (particularly diarrhoea)
- Vomit or stomach aspiration
- Drain output
- Bleeding
- Sweating
What are insensible fluid loss
Refers to fluid output that is difficult to measure such as through respiration, stools, burns and from sweat
Signs of hypovolaemia
- Hypotension (systolic < 100 mmHg)
- Tachycardia (heart rate > 90)
- Capillary refill time > 2 seconds
- Cold peripheries
- Raised respiratory rate
- Dry mucous membranes
- Reduced skin turgor
- Reduced urine output
- Sunken eyes
- Reduced body weight from baseline
- Feeling thirsty
Signs of hypervolaemia
- Peripheral oedema (check the ankles and sacral area)
- Pulmonary oedema (shortness of breath, reduced oxygen saturation, raised respiratory rate and bibasal crackles)
- Raised JVP
- Increased body weight from baseline (regular weights are an important way of monitoring fluid balance)
Do patients with third spacing present with signs of hypo or hypervolaemia
Both as may have low levels in intravascular space but excessive fluid in other areas such as interstitial space or peritoneal cavity
Main indications for IV fluids
- Resuscitation (e.g., sepsis or hypotension)
- Replacement (e.g., vomiting and diarrhoea)
- Maintenance (e.g., nil by mouth due to bowel obstruction)
2 main groups IV fluid
- Crystalloids
- Colloids
What are crystalloids
Water with added salts or glucose, contents redistritbutes through different fluid compartments of body
Examples of crystalloids
- 0.9% sodium chloride (“normal saline”)
- 5% dextrose
- 0.18% sodium chloride in 4% glucose
- Hartmann’s solution
- Plasma-Lyte 148
What does 1L bag of 0.9% saline solution contain
- 1 litre of water
- 154 mmol sodium (note that this is a lot of sodium, and lots of saline can result in hypernatraemia)
- 154 mmol chloride
What does 1L bag 5% dextrose contain
- 1 litre of water
- No electrolytes (note that lots of hypotonic fluid can result in hyponatraemia and oedema)
- 50 g of glucose
What does 1L bag 0.18% sodium chloride contain in 4% dextrose
- 1 litre of water
- 31 mmol sodium
- 31 mmol chloride
- 40 g of glucose
What does 1L bag hartmann solution contain
- 1 litre of water
- 131 mmol sodium
- 111 mmol chloride
- 5 mmol potassium
- 2 mmol calcium
- 29 mmol lactate (helps to buffer the solution – reducing the risk of acidosis)
What does 1L bag of plasma-lyte 148 contain
- 1 litre of water
- 140 mmol sodium
- 98 mmol chloride
- 5 mmol potassium
- 1.5 mmol magnesium
- 27 mmol acetate (helps to buffer the solution – reducing the risk of acidosis)
- 23 mmol gluconate (helps to buffer the solution – reducing the risk of acidosis)
What are colloids
Contain larger molecules that stay in intravascular space
1 example colloid
Human albumin solution
What is tonicity
Refers to osmotic pressure gradient between two fluids across a membrane, which determines whether water molecules will move accross membrane by osmosis
Water moves from area of lower concentration to area of higher concentration
Normal serum osmolarity
275-295mOsmol/kg
3 types of tonicity solutions can be
- Isotonic solutions
- Hypotonic solutions
- Hypertonic solutions
Examples of isotonic solutions
- 0.9% saline
- Hartmanns
- Plasma-lyte
Examples of hypotonic solutions
- 5% dextrose
- 0.18% sodium choride
Examples of hypertonic solutions
3% saline
What fluid should be used for fluid resuscitation
- Isotonic fluid
- 0.9% saline
- Hartmann’s solution
- Plasma-Lyte 148
What should never be given as rapid infusions
Potassium - can induce arrhythmia or cardiac arrest
Infusion should not exceed 10mmol/hour
Approximate requirements for maintanence fluids
- 25-30ml/kg/day water
- 1mmol/kg/day of sodium, potassium and chloride
- 50-100g/day glucose (to prevent ketosis, not to meet nutritional needs)
NICE guideline for fluid maintenence
- Start with 25-30ml/kg/day of 0.18% sodium chloride in 4% glucose with 27mmol/L of added potassium
NICE guidelines for fluid resuscitation
- An initial 500ml fluid bolus over 15 minutes (“stat”) followed by reassessment with ABCDE
- Repeat boluses of 250-500ml of fluid if required, each time with reassessment
- Seek expert help if patient not responding, particularly after 2L fluid
What does daily monitoring when using fluid maintenance involve
- Assessment of fluid status
- Fluid balance chart
- U&E blood test
Maximum time of fluid allowed to prescribe
24 hours
Too much fluid can lead to dilution of
- Sodium (with hypotonic solutions)
- Potassium (if potassium is not included)
- Other electrolytes, e.g., calcium or magnesium
- Haemoglobin and haematocrit (red blood cells in the blood) causing anaemia
- Clotting factors, platelets and fibrinogen causing coagulopathy (clotting problems)
With what conditions should seniours guide
- Elderly or frail patients
- Significant oedema
- Sodium imbalance (hyponatraemia or hypernatraemia)
- Heart failure
- Renal impairment
- Liver impairment
