Crystalloids (ASAN002/7) Flashcards
What are Crystalloids? (1)
Water–based solutions that contain small particles (ions & molecules).
What are the common constituents of Crystalloids? (3)
- Electrolytes
- Glucose or Dextrose
- Buffers
What are common Electrolytes found in Crystalloids? (5)
- Sodium
- Potassium
- Calcium
- Magnesium
- Chloride
What is the main purpose of Electrolytes in Crystalloids? (2)
- to replace or maintain plasma levels
- to correct electrolyte imbalances
What is the purpose of Glucose or Dextrose in Crystalloids? (1)
To provide energy to the patient
What is the purpose of Buffers in Crystalloids? (1)
To correct or maintain the normal acid–base balance of plasma.
What are the main characteristics of Crystalloids? (2)
- The small particles readily pass through membranes and into all body compartments.
- The fluid is rapidly redistributed through the body.
Do Crystalloids stay in the intravascular space?
No
What % of crystalloid fluids given will leave the intravascular space within 30 mins of administration?
75%
IMAGE – Crystalloids passing through membrane
What types of Tonicity can Crystalloid solutions be? (3)
- Isotonic
- Hypotonic
- Hypertonic
What are the two types of fluids that Crystalloids are divided into? (2)
- Replacement fluids
- Maintenance fluids
What is the aim of Replacement fluids? (2)
Replace patient deficits of water & electrolytes.
What are Replacement fluids used to correct? (2)
- Dehydration
- Hypovolaemia
What are the main characteristics of Replacement fluids? (3)
- Similar composition to plasma
- Isotonic
- Can be given rapidly in large volumes without causing electrolyte shifts.
What are the two most common Replacement fluids? (2)
- Hartmann’s (Lactated Ringers Solution)
- 0.9% NaCl (Normal saline)
What is the other name for Hartmann’s? (2)
Lactated Ringers Solution or LRS
What are the main characteristics of Hartmann’s? (6)
- Crystalloid solution
- Isotonic
- Similar concentration of electrolytes as extracellular fluid
- High concentrations of Sodium & Chloride
- Small amounts of Potassium & Calcium
- Lactate as a buffer
Why must a patient’s liver function be adequate if administering Hartmann’s? (1)
Has a negative ion that requires hepatic metabolism
What is 0.9% NaCl commonly called?
Normal Saline
What are the main characteristics of 0.9% NaCl? (4)
- Isotonic
- High concentrations of Sodium & Chloride
- No Potassium
- Can be used with other fluids / medications
Why would a type of fluid be classed as a Maintenance Fluid? (1)
When used to ‘maintain’ fluid balance.
Why are Maintenence fluids used? (2)
To meet patient’s ongoing sensible & insensible fluid losses
When is it appropriate to use Maintenance fluids? (1)
Once hydration has been restored.
How do we determine Maintenance fluid requirements? (2)
Insensible fluid losses
+
Sensible fluid losses
What are the main characteristics of Maintenance fluids? (3)
- Hypotonic
- Lower Sodium & Chloride content
- Lower osmolality
What electrolyte often needs to be added to maintenance fluids to maintain it? (1)
Potassium
What are two common Maintenance fluids? (2)
- 0.45% NaCl + 2.5% Dextrose
- Plasmalyte 56
What is the main characteristic of Hypertonic Crystalloids? (1)
High osmolality
What are Hypertonic Crystalloids often used for? (1)
Rapid volume expansion
What is the main benefit to using Hypertonic Crystalloids? (1)
Small amts can be used to increase the intravascular space, which will increase circulating volume.
How does Hypertonic Saline cause a sudden rapid rise in circulating blood volume? (1)
Causes fluid to move from extravasulcar space into intravascular space.
When is it beneficial to use Hypertonic Saline? (2)
In early tx of hypovolaemic & haemorrhagic shock.
When should Hypertonic Saline be used with caution & why? (2)
- When used in severely dehydrated patients
- It will worsen dehydration.
What type of fluids are recommend to be adminsted with Hypertonic Saline? (1)
Replacement Crystalloids
What is the benefit of administering Replacement Crystalloids and Hypertonic Saline together? (2)
Prolongs desired effect
(↑ circulating volume)
What are the major beneficial haemodynamic effects of Hypertonic Saline? (5)
- ↑ myocardial contractility
- ↑ cardiac output
- ↓ peripheral vasucular resistance
- Precapillary vasodilation
- Minimises risk of cerebral oedema – esp. with head trauma.
Why is it beneficial to administer Hypertonic Saline to a patient with head trauma? (1)
Minimises risk of cerebral oedema
How does giving large amounts of replacement fluids affect Intracranial Pressure? (2)
- During hypovolaemic shock it ↓ below normal due to systemic hypotention.
- If large amts of replacement fluids are given = ↑ IC pressure above normal, which may ↑ cerebral oedema & interfere with cerebral blood flow.
How does Hypertonic Saline protect the brain from Increased Intracranial Pressure? (1)
By helping to keep fluid in intravascular space rather than crossing into brain.
What are the main characteristics of Mannitol? (3)
- Hypertonic crystalloid
- Osmotic diuretic
- It is a high molecular–weight sugar.
How does an Osmotic diuretic work? (2)
Acts in kidneys to remove excess body water from blood & convert to urine.
What is Mannitol mainly used for?
- Prevent & treat oliguria (low urine output) associated with kidney failure
- Reduce ↑ pressure in brain (cerebral oedema) & intraocular pressure in eyes
- Promotes excreation of substances, i.e. aspirin & barbiturates in overdoses.
