Dehydration and Fluid management Flashcards
Hydration Status Examination
https://almostadoctor.co.uk/encyclopedia/hydration-status
Fluid Management
IV Fluid Prescribing in Adults - https://geekymedics.com/intravenous-iv-fluid-prescribing-adults/
Paeds IV Fluid - https://geekymedics.com/intravenous-iv-fluid-prescribing-in-paediatrics/
Prescribing IV Fluids -https://mindthebleep.com/prescribing-iv-fluids/
Fluid and Electrolytes - https://bnf.nice.org.uk/treatment-summaries/fluids-and-electrolytes/
Fluid and Electrolytes Children - https://bnfc.nice.org.uk/treatment-summaries/fluids-and-electrolytes/
When does dehydration occur?
Fluid output > fluid input
Is dehydration common?
Common presentation in elderly
Why are infants and children at higher risk of developing dehydration?
- Higher metabolic rates
- Inability to communicate thirst or self-hydrate effectively
- Greater water requirements per unit of weight
What questions should you ask in a history?
- Fluid intake - adequate?
- Symptoms suggesting dehydration
- Thirst, dizziness - Recent or ongoing fluid losses
- Vomiting (or NG tube loss), diarrhoea (incl. stoma output), excessive sweating, polyuria, fever, hyperventilation, Increased drain output (eg. biliary or pancreatic drain) - Quantity of fluid loss
- If vomited; how many episodes of vomiting over how long and how much fluid is in each vomitus - Is the patient still eating and drinking? If so how much?
- Is the patient still urinating? If so are they passing the same quantity urine and as often as when they are healthy? Is the urine concentrated or diluted?
- Polyuria may cause dehydration and give a clue to the underlying cause
- Oliguria or anuria could have many causes, one of which is severe dehydration. - Any comorbidities?
- Heart failure, renal failure
How does dehydration present?
Feeling thirsty
Dark-colored, strong-smelling urine
Urinated less frequently
Dizzy / light-headed
Tired
Dry mouth, lips and tongue
Sunken eyes
NICE Assessing Symptoms of Dehydration
- No clinically detectable dehydration
- Clinical dehydration
- Clinical shock
NICE symptoms of clinical dehydration
- Appears unwell or deteriorating
- Altered responsiveness (eg. irritable, lethargic)
- Decreased urine output
- Skin color unchanged
- Warm extremities
NICE symptoms of clinical shock
- Decreased level of consciousness
- Pale or mottle skin
- Cold extremities
What are signs of dehydration?
Dry mucous membranes
Loss of skin turgor
Sunken eyes
Sunken soft spot (fontanelle) on top of head
Few/no tears when crying
Not many wet nappies
Being drowsy or irrtiable
Severe dehydration
- Dehydration tachycardia
- Hypotension
- Delirium
NICE Assessing Signs of Dehydration
- No clinically detectable dehydration
- Clinical dehydration
- Clinical shock
NICE Signs of Clinical Dehydration?
- Sunken eyes
- Dry mucous membranes (except mouth breather)
- Tachycardia
- Tachypnoaea
- Normal peripheral pulses
- Normal CRT
- Reduced skin turgor
- Normal BP
NICE Signs of clinical shock?
- Tachycardia
- Tachypnoea
- Weak peripheral pulses
- Prolonged CRT
- Hypotension (decompensated shock)
What are the red flag signs and sx of dehydration?
Appears unwell or deteriorating
Altered responsiveness
Sunken eyes
Reduced skin turgor
Tachycardia
Tachypnoea
What red flags may be present in hypernatraemic dehydration?
Proportionally more water than sodium is lost from the body:
Jittery movements
Increased muscle tone
Hyperreflexia
Convulsions
Drowsiness or coma.
What findings suggest hypovolemia?
Increased output from wounds and drains
Decreased urine output (<30mls/hr)
A fluid chart showing a negative fluid balance
Weight loss
Other sources of fluid loss (e.g. rectal bleeding, diarrhoea, vomiting)
What findings suggest hypervolemia?
Increased urine output
Abdominal distension (ascites) and peripheral oedema
A fluid chart showing a positive fluid balance
Weight gain
What are causes of dehydration?
- Inadequate fluid intake
- Structural malformation (eg. tongue tie, cleft lip and/or palate, micrognathism) - in paediatrics, usually picked up and managed in neonatal period
- Discomfort - eg. oral ulcers, tonsillitis, viral pharyngitis, stomatitis
- Respiratory distress (paeds) - In order to feed and drink, it must be possible to temporarily stop breathing. This is very difficult if already short of breath.
- Neglect (esp paeds) - inadequate feeding - Excessive fluid loss
- Diarrhoea and/or vomiting - commonest cause in children
- Excessive sweating - eg. post exercise, hot weather (heatstroke), pyrexia
- Polyuria - eg. diabetes, diabetes insipidus
- Burns
Excess alcohol
Diruetics use
Bowel obstruction
Sepsis
Bleeding
What are the reasons for fluid prescription?
Resuscitation
Maintenance
Replacement
What are the key considerations with each patient in fluid management?
- Aim - resuscitation, maintenance, or replacement?
- Weight and size of the patient?
- Co-morbidities to consider? Eg. HF, CKD
4 Underlying reason for admission?
- Most recent electrolytes?
How much of total body weight is water?
2/3
How is the water (as part of body weight) distributed?
2/3 - ICF
1/3 - ECF
How is the water in the ECF distributed?
1/5 - intravascular space
4/5 - interstitial
Small proportion - trans cellular space
How is the location of fluids relevant depending on purpose?
General maintenance of hydration - fluid must distribute into all compartments
Resuscitation - fluid must stay in intravascular space
Why do septic patients need large volumes of fluids to maintain the intravascular volume?
- In septic patients, the tight junctions between the capillary endothelial cells break down and vascular permeability increases.
- As a result, increasing hydrostatic pressures and reducing oncotic pressure lead to fluid leaving the vasculature and entering the tissue.
- It is often therefore necessary to give relatively large volumes of IV fluid to maintain the intra-vascular volume, even though the total body water may be high. C
- lose monitoring of the fluid balance will be required.
What are the proportions of fluid gained and lost from various sources?
Where does most of a patient’s fluid input come from?
3/5th of fluid input comes through fluids via the enteric route
Remainder comes from both food and metabolic processes.
When a patient is nil by mouth (NBM), it is important that all sources are replaced via the parenteral route.
What are insensible losses?
Losses from non-urine sources
These rise in unwell patients who may be febrile, tachypnoeic, or having increased bowel output
Need to take this into account when replacing
How may patients start to correct themselves about being unwell?
When patients start to clinically improve, their vascular permeability returns to baseline state.
They therefore often “correct themselves” and urinate out the excess fluid that was previously required to maintain their intravascular volume and tissue perfusion.
In such patent, monitor the electrolytes and allow this correction to occur, as this is normal and is to be expected (rarely will supplementary IV fluids will be warranted in such cases).
How should fluid status be assessed in a fluid depleted patient?
Dry mucous membranes and reduced skin turgor
Decreasing urine output (should target >0.5 ml/kg/hr)
Orthostatic hypotension
In worsening stages:
- Increased capillary refill time
- Tachycardia
Low BP
How should fluid status be assessed in a fluid overloaded patient?
Raised JVP
Peripheral or sacral oedema
Pulmonary oedema
How should fluid status be monitored?
fluid input-output chart
daily weight chart
U&E’s for evidence of dehydration, renal hypo perfusion or electrolyte abnormalities
What do patients need replacing?
Water
Sodium
Potassium
Glucose
What are the daily requirements of elements for patients?
Water: 25-30 mL/kg/day
Na+: 1.0 mmol/kg/day
K+: 1.0 mmol/kg/day
Chloride: 1.0 mmol/kg/day
Glucose: 50-100g/day to limit starvation ketosis
What would the maintenance fluids be for an 80kg patient for 24 hrs?
2 litres of water
80mmol potassium
What are the 5 Rs of prescribing IV Fluids?
Resuscitation
Routine maintenance
Replacement
Redistribution
Reassessment
How are IV fluids categorised?
Crystalloids and Colloids
Crystalloids
- Solutions of small molecules in water
- More used in acute settings, theatres, for maintenance fluids
- Neither crystalloid or colloid is better in replenishing volume in resuscitation
- Crystalloids cheaper
Colloids
- High osmotic pressure
- Raise intravascular volume faster than crystalloids (in theory)
- Solutions of larger organic molecules
- Used less than crystalloids as they carry a risk of anaphylaxis
Examples of Crystalloids
0.9% Saline
5% Dextrose
Hartmann’s Solution
Normal Saline tonicity and use
- Sodium Chloride 0.9%
- Isotonic
- Used for resuscitation/maintenance
Hartmann’s Solution - tonicity and use
Isotonic
Used for resuscitation/maintenance
Sodium Chloride 0.18% / Glucose 4% - Tonicity and use
Hypotonic
Used for resuscitation/maintenance
5% Dextrose - tonicity and use
Hypotonic
Used for maintenance
Examples of Colloids
Albumin
Gelofusine
Dextran
Volplex
What are the electrolyte concentrations (in millimoles/litre)?
What is the risk with large volumes of 0.9% saline?
if large volumes are used there is an increased risk of hyperchloraemic metabolic acidosis
When should Hartmann’s solution not be used?
contains potassium and therefore should not be used in patients with hyperkalaemia
How should a dehydrated patient be treated?
Correct the deficit AND the fluids prescribed for maintenance
Reduced urine output management
- Reduced urine output <0.5 ml/ kg/ hr)
- Manage aggressively
- Give fluid challenge
- Then re-check clinical parameters (incl. urine output)
How much is the fluid challenge?
either 250ml or 500ml over 15-30 mins
Depending on pt size and co-morbidities
How should ongoing fluid loss be assessed?
- Are there any third spaces?
- Is there a diuresis?
- Is the patient tachypnoeic or febrile?
- Is the patient passing more stool than usual (high stoma output)?
- Are they losing electrolyte-rich fluid?
What are common scenarios causing electrolyte imbalances? How would these be seen?
- Dehydration - (high urea:creatinine ratio and high PCV)
- Vomiting - (low K+, low Cl–, and alkalosis)
- Diarrhoea - (low K+ and acidosis)
How should patients be monitored?
Regularly assess fluid status
Check what pt is managing orally and amend fluid prescription accordingly
Use clinical assessment, nursing charts (fluid input-output charts ± daily weights) and U&Es to guide this.
How should dehydration be managed in paediatrics?
- Treat reversible causes
How are paediatric patients rehydrated?
- Oral rehydration solution or IV fluids.
- All patients: fluid balance charts to assess fluid input, ongoing losses and urine output.
Oral rehydration solution:
- Small volumes at frequent intervals.
- Regular reassessment to determine effectiveness.
If child clinically dehydrated but able to tolerate enteral fluids (PO/NG):
- 50mL/kg fluid deficit is calculated.
- This is given orally, along with maintenance fluids, over 4 hours as oral rehydration solution.
- For example, a child who weighs 10kg will require 500mL AND maintenance fluid over 4 hours.
When should IV fluids be given in paediatric patients?
- Shock: suspected or confirmed
- A child with red flag symptoms or signs - shows clinical evidence of deterioration despite oral rehydration therapy
- A child persistently vomits the oral rehydration solution, given orally or via a nasogastric tube.
How should a child in shock be managed?
- Give a rapid 20ml/kg bolus 0.9% sodium chloride
- Call for senior help
- Reassess the patient
- (Caution advised in DKA or underlying heart condition when 10mL/kg bolus should be considered)
If inadequate or no response:
- Give another rapid 20ml/kg sodium chloride bolus and consider other causes of shock.
If a third bolus is required, consider input from paediatric intensive care
Once an adequate response to bolus therapy has been achieved (i.e. the patient is no longer clinically in shock) start IV fluid deficit correction
How should a paediatric patient be deficit corrected?
- If there is a recent weight done prior to admission, the fluid deficit can be taken as the weight loss compared to current weight.
- For example, if weight done 2 days ago was 15.5 kg and current weight is 15 kg, the fluid deficit can be taken as 500 ml (500 gram lost)
However, if there are signs of clinical dehydration, and there is no recent weight, the fluid deficit is calculated as:
weight (kg) x % replacement x 10.
- This is given over 48 hours.
- The % replacement (also known as % dehydration) should be assumed to be 10%, if dehydrated.
For example, a child who weighs 12 kg will require 1200 ml (12 x 10 x 10) over 48 hours, or 600 ml each day in addition to their maintenance.
Aim to correct fluid deficit over 48 hours with 0.9% sodium chloride and 5% dextrose
Over how long should a fluid deficit be corrected in paediatric patients?
48 hrs
How should a paediatric patient be monitored?
U+Es and plasma glucose
- Measure before starting deficit correction and regularly over the 48 hour period.
- Electrolyte imbalances and/or hypoglycaemia may require alterations to the type of fluid used.
Significant ongoing losses (eg. through Vomiting + diarrhoea) - documented on the patient’s fluid balance chart and replaced in addition to fluid deficit correction.
How should paediatric patients with hypernatraemic dehydration be managed?
What cautions should be taken?
- Call senior paediatric help
- Replace fluid slowly over 48 hours in order to avoid cerebral oedema.
- Regular monitoring of U+Es should be done to ensure plasma sodium does not fall by a rate greater than 0.5mmol/L/hour.
How should fluids be manned after rehydration in children?
Encourage breastfeeding and other milk feeds
Encourage fluid intake
Discourage fruit juices and carbonated drinks
What children may be at risk of dehydration recurring and how should they be managed?
- < 1 y/o, esp those < 6 months
- Infants who were of low birth weight
- Children who have passed > 5 diarrhoeal stools in the previous 24 hours
- Children who have vomited >2 times in previous 24 hours.
How should maintenance fluid be prescribed in a paediatric patient who is NBM for a surgical procedure / not toelrating enteral fluids?
Over a 24hr period using 0.9% NaCl and 5% Dextrose
100ml/kg for first 10kg bodyweight
50ml/kg for second 10kg bodyweight
20ml/kg for every kg above 20kg bodyweight
For example, a 25kg child would require the following:
- First 10 kg = 1000ml (10 x 100mL)
- Second 10kg = 500ml (10 x 50mL)
- Last 5kg = 100ml (5 x 20mL)
- Total 1600ml over 24 hours (1600/24: rate = 67ml/hr)
Remember to monitor electrolytes to determine if anything such as potassium should be added to the fluids.
What volumes over 24hrs do males and females not usually need?
Over 24 hours, males rarely need more than 2500mL and females rarely need more than 2000mL
What patients should you be cautious with when prescribing fluids?
Obese - When prescribing routine maintenance fluids for obese patients you should adjust the prescription to their ideal body weight. You should use the lower range for volume per kg (e.g. 25 ml/kg rather than 30 ml/kg) as patients rarely need more than 3 litres of fluid per day.
Elderly
Renal impairment or cardiac failure patients
Malnourished patients at risk of refeeding syndrome
Why are electrolyte balanced solution (eg. Hartmann’s and Ringer’s lactate) used over normal saline in post-op fluid management?
Because of understanding of complication re. hypercholeraemic acidosis
Before, many oliguric postoperative patients received enormous quantities of IV fluids.
What fluids are generally not recommended for surgical patients?
5% dextrose and dextrose/saline combinations
What is the general guidance for post-op fluids?
- Fluids given should be documented clearly and easily available
- Assess the patient’s fluid status when they leave theatre
- f a patient is haemodynamically stable and euvolaemic, aim to restart oral fluid intake as soon as possible
- Review patients whose urinary sodium is < 20
- If a patient is oedematous, hypovolaemia if present should be treated first. This should then be followed by a negative balance of sodium and water, monitored using urine Na excretion levels.
- Solutions such as Dextran 70 should be used in caution in patients with sepsis as there is a risk of developing acute renal injury.
