fluid & electrolytes (dr acharya)

8/12/2019 Fluid & Electrolytes (Dr Acharya)

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Fluid and electrolyte therapy

Dr Ashoka Acharya

Consultant PaediatricsWarwick hospital


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Dehydration

Abnormal fluid losses overcoming renalcompensating mechanisms

Main aim of compensation ismaintaining plasma volume and BP atall cost

Loss of homeostasishypovolaemicshock

Principal causes: diarrhoea and DKA


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Definition

Parenteral or oral fluid therapy

Maintain/restore volume/composition of

body fluids

Takes account of corrective

physiological mechanisms


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Fluid therapy: Goal

Achieve normal intracellular and

extracellular chemical environment

Thereby optimise cell and organfunction


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Factors determining requirements

Maintenance fluid: replaces usual

losses of fluid and electrolytes

Deficit replacement fluid: designed toreplace abnormal losses due to disease

Supplemental fluid: replaces measured

or estimated continuing abnormallosses


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Factors determining requirements

Each component is calculated

separately

Fluid therapy often based on grossestimates. Deficit often overestimated.

Repeated clinical reassessment and

adjustment needed


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Maintenance fluid

Directly related to metabolic rate

endogenous water production

urinary solute excretion,

heat production- 25% lost through

insensible water loss)


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Maintenance therapy

Generally 100ml per 100 calories used

Urine: obligatory loss = 65 ml

Insensible water loss = 35 ml

Sweating =23 ml

pulmonary =12 ml


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Maintenance therapy: increased

requirements Increased activity (30%)

Fever (1C increases by 12%)

Dry environment

Hyperventilation

ELBW- transcutaneous losses 100-200ml/kg/day

Overhead heaters, phototherapy units


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Maintenance fluid-decreased

requirements Comatose

Hypothermia

Highly humidified atmospheres

Humidified ventilator circuits


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Maintenance fluid: increased

renal losses High solute load (DM, Mannitol, high

protein diets)

ADH insufficiency

Central

Nephrogenic Primary

Secondary: sickle cell, obstructive uropathy, chronic

PN, reflux nehropathy, hypokalemia, hypercalcemia,

drugs, psychogenic polydipsia


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Maintenance fluid: decreased

urinary losses SIADH

Renal failure

Replace insensible water loss +urine

output ml/ml with free water


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Maintenance sodium needs

Increased: CF, salt losing nephropathy,

chronic PN, obstructive uropathy,

diuretics, fistulas, diversions, NGdrainage

Decreased: Hepatic failure, cardiac

failure, renal failure, nephrotic syndrome


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Maintenance potassium needs

Increased: Chronic renal disease,

gastric and intestinal drainage, chronic

diuretics, laxative abuse Decreased or nil: Acute renal failure,

adrenal insufficiency, severe metabolic

acidosis


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Normal maintenance

requirements (holiday and segarWt (kg) H20(ml/k

g/dy)Na(mmol/kg/dy)

K(mmol/kg/dy)

Energy(kcal/Kg/dy)

First 10kg

100 2-4 1.5-2.5 100

Second10 kg

50 1-2 0.5-1.5 75

Subsequent kg

20 0.5-1 0.2-0.7 30


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Maintenance fluids: route

Oral or parenteral

Calories: usually as 5% dextrose

TPN


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Deficit Therapy: factors affecting

Oral or parenteral intake

Pathologic body losses

Physiologic body losses

compensatory attempts to modify

volume and composition

Net effect- Deficits from different causes

often similar in magnitude and

composition


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Infant: moderately severe

dehydrationCondition H2O

(ml)Nammol

Kmmol

Clmmol

D and VIsonatremic 100-200 8-10 8-10 8-10Hypernatremic

100-200 2-4 0-4 -2 to 6

Hyponatremic

100-200 10-12 8-10 10-12

Pyloricstenosis

100-200 8-10 10-12 10-12

DKA 100-200 8-10 5-7 6-8

Fasting andthirsting

100-200 5-7 1-2 4-6

Per k bod wei ht


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Deficit therapy

Severity: Magnitude and rapidity

Estimated from recent weight or clinical

features

Type: Relative loss of water and

electrolytes mainly sodium

pathophysiology

therapy

prognosis


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Deficit therapy: Types

Isotonic: sodium 130-150 mmol/l, no

fluid shifts, 80% of cases

Hypotonic: sodium 150 mmol/l, ICF to

ECF, 10% cases


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Deficit Therapy:types and history

D and V for days, good intake, low salt

Cholera, bacillary dysentery

High fever, poor intake

Infant with NDI, poor water intake

Intake of dilute milk formula

Intake of boiled semiskimmed milk

wrongly prepared ORS


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Assessment of deficit severity

Signs &symptoms

Mild dehydration Moderatedehydration

Severedehydration

Body weightloss(%)

3-5% 6-9% 10%or more

General app,infant

Alert, restless Thirsty, restless/lethargic/irritable

Lethargic/comatoseFloppy,cold,sweaty

Older child- Thirsty, alert,restless

Thirsty, alert,posturalhypotension

Lethargic,cold,sweaty,cyanosed,wrinkle

d skin, musclecramps

Radial pulse Normal Rapid and weak Rapid,thready/impalpable

Respiration Normal Deep Deep and rapid

Anterior fontanel Normal Sunken Very sunken


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Assessment of severity: contd

Systolic BP Normal Normal/orthstatichypotension

Low/unrecordable

Skin elasticity Retractsimmediately

Retracts slowly Retracts veryslowly

Eyes Normal Sunken Grossly sunken

Tears Present Absent/reduced absent

Mucosa Moist Dry Very dry

Urine Normal Reduced and dark Anuria/severeoliguria

CRT Normal +/- 2 sec >3 sec


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Calculation of deficit fluid

Percentage dehydration x wt in kg x 10=

ml of fluid

eg: 7% dehydration of infant weighing10 kgs = 7x10x10=700 ml


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Clinical features

Signs represent depletion of ECF

Plasma: tachycardia, fall of BP, postural

hypotension, cool extremities, increasedCRT, decreased urine

Interstitial fluid: Tenting of skin

Transcellular fluid: dry mouth, sunken eyes,decreased tears, sunken fontanel


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Signs V's type of deficit

Hyponatremic: increased severity of

signs for amount of fluid loss

Hypernatremic: Less signs, irritable,hypertonic, hyperreflexic, warm

extremities, doughy skin


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Lab tests

FBC: Increased Hb, PCV

Serum Na: type of dehydration

serum K: gut loss, acidosis; needs ECG monitoring Serum HCO3: acidosis- D&V, DKA: alkalosis-Pyloric

stenosis, NG drainage

Serum chloride: changes with Na, chloride diarrhea

Urea/creatinine: elevated with decrease in GFR, maybe normal!

Urine: infection screen, specific gravity, electrolytes

stool: culture, electrolytes


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Treatment

Oral therapy: mild to moderatedehydration

Parenteral therapy: severe dehydration

Persistent vomiting

Refusal of oral intake

Abdominal distension

No caregiver to give close attention


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Stages of treatment

Initial therapy: expand ECF volume

Subsequent therapy: replace

deficit/maintenance/ongoing losses

Final therapy: Return to normal

composition/establish oral feeds/correct

potassium deficit


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Commonly available crystalloids:

isotonicFluids Na (mmol/l) K (mmol/l) Cl (mmol/l) Energy(kcal/l)

other

saline0.9% 150 0 150 0 0

saline0.45%dextrose

2.5%

75 0 75 100 0

Saline

0.18%

dextrose

4%,KCl

20mmol/lit

30 20 30 160 0

Dextrose

5%

0 0 0 200 0


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Isotonic crystalloid fluids

Fluid Na K Cl Energy Other

Saline

0.18%

dextrose

4%

30 0 30 160 0

Hartmanns

solution

131 5 111 0 lactate


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Hypertonic crystalloids

Fluid Na K Cl Energy Other

Saline

0.45%dextrose

5%

75 0 75 200 0

Dextrose

10%

0 0 0 400 0

Saline0.18%

dextrose

10%

30 0 30 400 0

Dextrose

20%

0 0 0 800 0


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Colloid fluids

Fluids Na K Ca Duration

of action

comments

Albumin

4.5%

150 1 0 6 Protein buffers

Gelofusine 154


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Initial therapy

Normal saline or Hartmans solution

regardless of type of deficit

20 ml/kg rapid bolus, repeat if needed IV, intraosseous line

Never use hyponatremic fluids

Adequate crystalloid dose better than colloid No potassium till urine output established


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Subsequent therapy

Calculate over 8 hour intervals

Deficit replaced over 24 hours but can

be done over 8 to 12 hours exceptHYPERNATREMIA

Early K+ replacement after urine output

Maximum K+, 40 mmol/l (ITU 80mmol/l)


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Isonatremic dehydration

Deficit plus maintenance plus ongoing lossescalculated

Use 0.45%saline with 2.5% or 5% dextrosefor subsequent therapy

Give 50% in first 8 hours and remaining over16 hours

Subtract boluses from total fluid Assess clinical state regularly and modify if

needed


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Hyponatremic dehydration

Extra Na deficit (mmol/l)=desired Na-

actual Na x 0.6 x Wt kgs

Manage as for isonatremic dehydrationbut replace deficit Na over 12-24 hours

Raise serum Na by 10 mmol/l/day

If Na


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Hypernatremic dehydration:

complications Cerebral haemorrhage, thrombosis,

subdural effusion- permanent handicap,

renal vein thrombosis During treatment- cerebral oedema,

seizures, hypocalcemia

High mortality if Serum Na >160mmol/l


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Hypernatremic dehydration

Always use isonatremic boluses

Slow correction of deficit over 48 to 72 hours

Aim to decrease serum Na by 10 mmol/l/day Use 0.18saline or 0.45% saline with dextrose

for subsequent therapy

Seizures: 3% saline, mannitol,hyperventilation, calcium gluconate


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Supplemental fluids

Consider composition of fluid lost

D&V: 0.45% saline

Cholera:0.9% saline

NG tube aspiration: 0.45 to 0.9% saline

plus potassium

Gut losses: same


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Assessment of response

Appearance, activity

Skin turgor

BP Intake/output chart

U&E, glucose

blood gas CVP monitoring

Eyeballs, tears

CRT

Weight Urine Specific

gravity

Urine output ECG monitoring


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Oral rehydration therapy

Mild to moderate dehydration

Types of ORS: high sodium- 90mmol/l,

low Na- 50 mmol/l

Glucose facilitated sodium absorption,

sucrose less effective, rice based

effective


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ORS

Use 50ml/kg in mild and 100ml/kg inmoderate dehydration.

Give over 4 hours. Allow breast feeds andformula after rehydration. Reassess regularly.Small frequent feeds decrease vomiting.Consider NG tube.

Maintenance with 100ml/kg/day till diarrhoeastops

For on going losses add 10-15ml/kg/hr


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Hyponatremia: sodium depletion

Renal losses: Preterm, ATN, Diuretics,

mineralocorticoid deficiency, RTA

Extra renal loss: D&V, Burns, ascites,pleural effusion,csf drainage, NG

drainage, CF

Nutritional deficits: Inadequate Na inTPN, oral intake


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Hyponatremia: water excess

SIADH

Glucocotricoid deficiency

Hypothyroidism

Excess parenteral fluid

Psychogenic polydipsia

Tap water enema


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Hyponatremia: excess Na and

water

Nephrotic syndrome

Cirrhosis

Cardiac failure

Acute and chronic renal failure


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Hyponatremia: asymptomatic

Water Excess: (urinary Na usually >20

mmol/l) fluid restriction, may be needed

for days Salt deficiency: (urinary Na


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Hypernatremia: sodium excess

Improperly mixed ORS or formula

Accidental or deliberate swap of salt for

sugar in feeds Excess Bicarb during resus

Hypernatremic enemas

Drugs: penicillin, gaviscon


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Hypernatremia: water deficit

Diabetes insipidus

Solute diuresis

D&V

Inadequate breast feeds

Intentional water with holding

Insensible loss in prematures


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Hypernatremia: treatment

Salt poisoning: peritoneal dialysis

Phenobarbitone for seizures

Inotropes for heart failure


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Hypokalemia: causes

Diarrhoea

Alkalosis

Volume depletion Primary hyperaldosteronism,cushing syn,

thyrotoxicosis

Diuretic abuse DKA

Bartters syndrome


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Hypokalemia: consequences

Cardiac: flat T wave and prolonged QTinterval

Orthostatic hypotension, tetany, hypotonia,muscle weakness, death from resp failure

Paralytic ileus, gastric distension

Failure to thrive

Rhabdomyolysis Nephrosclerosis and interstitial fibrosis:

polyuria

alkalosis


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Hypokalemia: treatment

Replacement potassium orally or

parenterally

3 mmol/kg/day in Barttersyn/indomethacin

Up to 10 mmol/kg/day in

RTA/hyperaldosteronism


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Hyperkalemia: causes

Renal failure

Acidosis

Adrenal insufficiency

Cell lysis (trauma, surgery, tumour lysis)

Excessive intake

Sampling error!


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Hyperkalemia: consequences

Paresthesias, flaccid paralysis

Tall T waves, increased P-R interval,

wide QRS complex, VF


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Hyperkalemia:management

If cardiac rhythm affected give calcium 1mmol/kg iv/specific anti arrhythmic drug

If normal rhythm, give nebulised salbutamol2.5 to 5 mg. Check K and pH.

If falling K- give calcium resonium 1g/kg po orpr- plan dialysis if needed

If still high (6.5 or more) give dextroseinfusion 0.5g/kg/hr and iv insulin infusion,0.05units/kg/hr if pH 7.35 give sodium bicarbonate 2.5

mmol/kg iv


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Hypercalcemia

Hyperparathyroidism, Hypervitaminosis

D&A, Idiopathic hypercalcemia,

malignancy thiazide diureticabuse,skeletal disorders,immobilisation

Polyuria, polydypsia

Volume expansion with saline,treatment of cause


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Hypermagnesemia

Usually in renal failure, Addison disease,

toxemia of pregnancy, enemas in megacolon

Drowsiness, coma if levels exceed 10 meq/l.Intra ventricular and atrioventricular

conduction defects at 5 meq/l

IV calcium gluconate rapidly reverses effects

on heart and CNS


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Case 1

8 week old infant

Weight 4 kgs, poor wt gain in last 4

weeks, Vomiting from 3 weeks of age, now after

most feeds, forceful, not passing urinewell last 24 hours

Moderate dehydration on examination

Na 130, Cl 94, K 2.6, HCo3 29.8


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Case 1

Maintenance: 100 x 4= 400 ml

On going losses: Ng aspirate volume for volume with normal

saline

Start 0.45% saline dextrose 5% to give 400 ml over 8 hours andremaining 400 ml over 16 hours

Add Kcl 4 mmol/100ml once urine output noted

Monitor weight, urine output, Nasogastric aspirate, blood gas

and electrolytes,ECG.

Once serum K rises to 3.5 decrease Kcl to 2 mmol/100ml Deficit fluid: 10 x10 x4= 400 ml

Once stable, send for surgery


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Case 2

One year old, 10 Kgs with 2 days of

D&V. Given clear fluids at home. No

urine in last 6 hours. Some fever. Notdrinking ,lethargic last 2 hours.

Severe dehydration on examination

Blood: Na 136, K 2.2, Hco3 8, pH7.35


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Case 2

Bolus 20 ml/kg- 0.9%saline, repeat if still shocked

Deficit fluid: 15 x10 x10=1500 ml 400ml bolus = 1100ml

Maintenance fluid: 100 x10= 1000 ml

Give 1050ml in 8 hours and 1050 remaining in 16 hours as0.45% saline 5% dextrose

Add Kcl 40 mmol/l after urine output

Monitor ECG, weight, urine output, electrolytes, continuing

losses for replacement

Once rehydrated offer ORS, milk and review fluids


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Case 3

Four year old weighing 14 Kgs, lethargic,

vomiting, rapid breathing since 12 hours.

Producing urine. Normal stools. Over 2

weeks, since a cold has been drinking a lot,

eating a lot and bed wetting again.

Moderate dehydration

Glucose 30 mmol/l, Na 128 mmol/l, K 4.8mmol/l, HCO3 8 mmol/l, pH 7.28


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Case 3

Start normal saline infusion, 20 ml/kg over 1 hour

Start insulin infusion 0.05u/kg/hr

0.45 saline+Kcl 20mmol/500 ml, 20 ml/kg over 2ndhour

0.45 saline+KCL or Pot phos 30mmol/l over 10 hours

Maintenance fluid for 36 hours:1000+50x4=1200+600=1800ml

Deficit fluid: 10x10x14= 1400 ml

Correct 50% deficit in first 12 hours

Monitor ECG, glucose, U&E, blood gas, weight, urine output, GCS hourlyto 2 hourly

Change fluid to 0.18 saline 5% dextrose when blood glucose reaches 16 to17 mmol/l. Adjust K and insulin infusion rates as needed. Consider an

Antibiotic.

When blood gas normal, blood glucose stable,patient drinking, givesubcutaneous insulin 0.2 to 0.4 units/kg qds and stop iv infusions.

Start regular insulin dose after another 24 hours


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DKA: complication

Cerebral edema: headache, change in

consciousness,unequal dilated pupil,

vomiting,incontinence,delirium,bradycardia

Reduce iv rate, mannitol 1gm/kg iv,

repeat in 2-4 hours

fluid & electrolytes (dr acharya)

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