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