Gastroentritis Fluids and electrolytes
Wajdi Amayreh, MB BS, JB, MRCPCH
NORMAL REQUIREMENTS VOLUME
Blood volume is 80-100 mls/kg
Total body water is 600-800mls/kg
2/3 water is intracellular, the rest is extra cellular
Dehydration is detected after >5% total fluid loss across body compartments
Body homeostasis can regulate fluid within the body to a certain degree
The fluid required is that which maintains the person well hydrated and passing adequate urine output
Fluid requirements are of 4 types
- Replacement of insensible losses
- Replacement of essential urine output
- Extra fluid to maintain modest state
of diuresis
- Replacement of any abnormal losses
Maintenance Fluid Requirements
Body weight Fluid
requirement/day
Fluid
requirement/hr
First 10 kgs 100 ml/kg 4 ml/kg
Second 10 kgs 50 ml/kg 2 ml/kg
Subsequent kgs 20 ml/kg 1 ml/kg
ELECTROLYTES
There is nothing as fixed normal
electrolyte requirement
There are obligatory losses which need
to be replaced
Any excess will be excreted in the urine
Electrolyte contents of Body Fluids
FLUID Na
(mmol/l)
K
(mmol/l)
CL
(mmol/l)
HCO3
(mmol/l)
Plasma 135-141 3.5-5.5 100-105 24-28
Gastric 20-80 5-20 100-150 0
Intestinal 100-140 5-15 90-130 15-65
Diarrhoea 7-96 34-150 17-164 0-75
Sweat <40 6-15 <40 0-10
Normal water, electrolyte, energy and
protein requirements
Body
Weight
Water ml/kg/day
Na mmol/kg/day
K mmol/kg/day
Energy Kcal/day
Protein g/day
1st
10 kg
100 2-4 1.5-2.5 110 3.00
2nd
10kg 50 1-2 0.5-1.5 75 1.50
Sub kg 20 0.5-1 0.2-0.7 30 0.75
Composition of available crystalloid
solutions (isotonic)
Fluid Na+ mmol/l
K+
mmol/l
CL- mmol/l
Energy Kcal/l
Other
Isotonic Crystalloid Fluids
0.9% S 150 0 150 0 0
0.45%S,D2.5% 75 0 75 100 0
0.18%S,D4% 30 0 30 160 0
D5% 0 0 0 200 0
0.18%S,D4%10
mmol KCl/500ml 30 20 50 160 0
Hartmann’s sol 131 5 111 0 Lactate
Gastroenteritis
Infective diarrhoea and vomiting (GE) remain an important cause of morbidity all over the world.
In developing countries GE claims the lives of about 5 million children each year.
The commonest cause of GE is rotavirus infection, nearly 60% of cases in children < 2 years of age.
Adenovirus, calicivirus, corona and astroviruses have been implicated in outbreaks.
Bacterial causes are less common and are suggested by the presence of blood in the stool.
Campylobacter jejuni, the commonest of bacterial infections in developed countries is often associated with severe abdominal pain.
Shigella and some salmonellae produce dysenteric type of infections with blood, puss in the stool, pain and tenesmus.
Shigella may be accompanied by high fever causing a febrile convulsion.
Cholera and enerotoxigenic E coli infections are associated with profuse, rapidly dehydrating diarrhoea.
However, clinical features act as a poor guide to the pathogen.
Conditions which mimic GE
Septicaemia, meningitis Systemic infections
RTIs, OM, hepatitis A,UTI Local infections
Pyloric stenosis,
intussusception,
appendicitis, NEC,
Hirschsprung’s disease
Surgical disorders
DKA Metbolic disorder
H U syndrome Renal disorder
Coeliac disease, Cow’s
milk intolerance, adrenal
insufficiency
Other
Consequences
Dehydration and its complications are the usual
cause of death in GE and its correction is the
fundamental aim of treatment.
Dehydration is detected after >5% total fluid loss
across body compartments.
Body homeostasis can regulate fluid within the
body to a certain degree.
Accurate clinical assessment of dehydration is
important but difficult.
DEHYDRATION
Abnormal loss of body fluids which are more than the body can compensate for
Natural mechanisms of compensation aim at maintaining circulatory volume and BP
Major causes are GI diseases and DKA, other may be renal or CNS causes
Types of dehydration
Depending on the source of fluid losses and quantities of electrolytes lost, dehydration can be divided into 3 types
Isotonic dehydration, equal water and Na losses
Hypotonic dehydration, more Na loss
Hypertonic dehydration, more water loss
Hypertonic dehydration
Hypernatremia; signs of extracellular fluid depletion are less per unit of fluid loss and depression of the fontanelle, reduced tissue elasticity and sunken eyes are less obvious which makes it difficult to recognise this type of dehydration especially in obese infants.
In all types there is usually loss of Na and water but the losses vary
The more severe the dehydration is, the more likely hypovolaemia (decreased blood volume and shock) is a problem
Speed of loss is also important, slow losses cause massive dehydration without hypovolaemia, whereas acute severe loss can present with hypovolaemia without apparent significant dehydration
Symptoms and signs of dehydration
Sign/symptoms
Mild <5%
Mod 5-
10%
Sev >10%
Notes
↓ Urine output + + + Watery D, wet nappies
Dry mouth +/- + + Mouth breathers
Sunken ant fontanelle - + + Crying increases pressure
Sunken eyes - + +
↓ Skin turgor - +/- + Beware the thin, diff sites
↓ Eyeball turgor - +/- + Difficult to assess in young
Tachypnoea - +/- + ↑with met acidosis &
pyrexia
Tachycardia - +/- + Fever, shock, irritability
Drowsiness/irritability - +/- +
Infants are at particular risk for dehydration
Greater surface area to wt ratio leading to greater insensible water loss ( 300 ml/m2 per day, equivalent in infants to 15 -17 ml/kg per day).
Inability to gain access to fluids when thirsty.
Higher basal fluid requirements 100-120 ml/kg.
MANAGEMENT Depends on dehydration percentage
ABC
ORS may suffice
IVF may be needed
More than 5% dehydration will usually need IVF
Calculate the maintenance and deficit fluid
Calculate the maintenance and deficit electrolytes
Choose the type of fluid
Give fluids with glucose in children
Replacement within 24 hrs in isotonic or hypotonic dehydration
In hypernatraemic dehydration correction depends on the degree of hypernatraemia
Be aware of too rapid correction; water pouring into cells
In hypernatraemic dehydration, decrease Na by no more than 10 mmol/l/day, electrolytes should be measured at least 4 hourly initially
In very sick patients
- Catheterise the patient
- Replace deficit within 24 hrs
- Replace insensible losses with 0.18 % S 4% dextrose
- Replace urine output ml for ml on an hourly basis with 0.18 or 0.45 S with dextrose according to plasma electrolytes
Antidiarrheal drugs(loperamide, lomotil) and anti emetics
- Are ineffective.
- May prolong the excretion of bacteria in stool.
- Can be associated with side effects.
- Add unnecessarily to cost.
- Focuses attention away from oral dehydration.
Antibiotics are indicated only for specific bacterial or protozoal infections; e.g cholera, shigellosis, giardiasis.
Post GE syndrome
Watery diarrhea following the re introduction of normal diet after an episode of GE.
Temporary lactose intolerance may have developed, which can be confirmed by the presence of non-absorbed sugar in the stools giving a positive Clinitest result. Reintroduce normal diet after 24 hours.
Multiple dietery intolerances may result, implementation of a diet which excludes cow's milk,disaccharides and gluten may be needed.
Other modalities of treatment!
K DISORDERS
As it is mostly intracellular, it acts as a
buffer
Cardiac arrhythmias can occur at levels
outside the normal range
True hypokalaemia is manifest after
significant total body depletion has
occurred whereas Hyperkalaemia
represents a significant overload
Causes of hypo- and hyperkalaemia
Hypokalaemia Hyperkalaemia
Diarrhoea Renal failure
Alkalosis Acidosis
Volume Depletion Adrenal insufficiency
Primary
hyperaldosteronism
Cell lysis
Diuretic abuse Excessive K+ intake
Hypokalaemia
Usually a result of excessive K loss, from
acute diarrhoeal illness
Large amounts are required to return the
plasma level to normal
The oral route is the fastest way of giving K,
IV route may be needed
IV K sol. not more than 80 mmol/l
Look for causes if any
Hyperkalaemia
Dangerous
Rare to get arrhythmias with levels below 7.5 mmol/l
B2 stimulants are the immediate treatment of choice, they stimulate cellular K uptake, K levels decrease by 1mmol/l with the recommended doses
Investigate and treat if there is no immediate threat to life
Other measures, Algorithm, redistribute K, so the problem is just delayed
K is removed by either dialysis or ion exchange resins (ca resonium)
ARRHYTHMIA Calcium
0.1 mmol/kg IV
Nebulised salbutamol
2.5-10 mg
Repeat serum
potassium
Ca resonium
1g/kg PO or PR
Assess PH
NaHCO3 2.5
mmol/kg IV
Dextrose 0.5g/kg/h
and insulin 0.05 u/kg/h
IV
DIALYSIS IF
NECESSARY
Yes
No
Falling
Remains high
>7.35 <7.34
Consider specific
Arrhythmia protocol
Management of hyperkalaemia
Salbutamol dose by age
Age (years) Salbutamol dose (mg)
≤ 2.5 2.5
2.5 -7.5 5
> 7.5 10