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Fluid and electrolyte therapy

Dr Ashoka Acharya

Consultant Paediatrics

Warwick hospital

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Dehydration

Abnormal fluid losses overcoming renal compensating mechanisms

Main aim of compensation is maintaining plasma volume and BP at all cost

Loss of homeostasis –hypovolaemic shock

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 organ function

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Factors determining requirements

Maintenance fluid: replaces usual losses of fluid and electrolytes

Deficit replacement fluid: designed to replace abnormal losses due to disease

Supplemental fluid: replaces measured or estimated continuing abnormal losses

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Factors determining requirements

Each component is calculated separately

Fluid therapy often based on gross estimates. 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 (1°C 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, NG drainage

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 10 kg

100 2-4 1.5-2.5 100

Second 10 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)Na(mmol)

K(mmol)

Cl(mmol)

D and VIsonatremic

100-200 8-10 8-10 8-10Hypernatremic

100-200 2-4 0-4 -2 to –6Hyponatremic

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

100-200 8-10 10-12 10-12DKA 100-200 8-10 5-7 6-8Fasting andthirsting

100-200 5-7 1-2 4-6Per kg body weight

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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 <130mmol/l, ECF to ICF, 10% cases

hypertonic: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,wrinkled skin, musclecramps

Radial pulse Normal Rapid and weak Rapid,thready/impalpable

Respiration Normal Deep Deep and rapid

Anterior fontanel Normal Sunken Very sunken

contd

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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 weighing 10 kgs = 7x10x10=700 ml

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Clinical features

Signs represent depletion of ECF Plasma: tachycardia, fall of BP, postural

hypotension, cool extremities, increased CRT, decreased urine

Interstitial fluid: Tenting of skin Transcellular fluid: dry mouth, sunken eyes,

decreased tears, sunken fontanel

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Signs of dehydration

Mild dehydration: no signs Severe dehydration: Prolonged capillary refill

time,dry mucosa, decreased skin turgor, general appearance are the most sensitive and specific

Acidosis: Kussmaul’s breathing Hypokalemia: weakness, abd dist, ileus,cardiac

arrhythmias hypocalcemia and magnesemia: tetany, muscle

twitching

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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, may

be normal! Urine: infection screen, specific gravity, electrolytes stool: culture, electrolytes

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Treatment

Oral therapy: mild to moderate dehydration

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

Hartmann’s 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

Saline 0.18% 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 <1 <1 3 Gelatine

Haemaccel 145 5 12.5 3 Gelatine

Pentastarch 154 0 0 7 Hydroxyethyl starch

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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 except HYPERNATREMIA

Early K+ replacement after urine output Maximum K+, 40 mmol/l (ITU 80

mmol/l)

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Isonatremic dehydration

Deficit plus maintenance plus ongoing losses calculated

Use 0.45%saline with 2.5% or 5% dextrose for subsequent therapy

Give 50% in first 8 hours and remaining over 16 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 dehydration but replace deficit Na over 12-24 hours

Raise serum Na by 10 mmol/l/day If Na <120mmol/l and seizures give 3%

Nacl 1ml/min max 12ml/Kg

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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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Composition of external losses

Fluid Na (mmol/l) K (mmol/l) Cl (mmol/l) Protein (g/dl)

Gastric 20-80 5-20 100-150

Small bowel 100-140 5-15 90-130

Ileostomy 45-135 3-15 20-115

Diarrhoea 10-90 10-80 10-110

Burns 140 5 110 3-5

Sweat 10-30 3-10 10-35

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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 in moderate dehydration.

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

Maintenance with 100ml/kg/day till diarrhoea stops

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 in TPN, 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 <10 mmol/l, except in renal salt loss) Add salt to diet

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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 QT interval 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 Bartter syn/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 1 mmol/kg iv/specific anti arrhythmic drug

If normal rhythm, give nebulised salbutamol 2.5 to 5 mg. Check K and pH.

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

If still high (6.5 or more) give dextrose infusion 0.5g/kg/hr and iv insulin infusion, 0.05units/kg/hr if pH <7.34

If pH >7.35 give sodium bicarbonate 2.5 mmol/kg iv

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Hypocalcemia

Septicemia, rickets,hypoparathyroidsm, pancreatitis, massive blood transfusion, renal failure

Weakness, tetany, convulsions, hypotension and arrhythmias

Calcium infusion, phosphate binders/dialysis, treatment of cause

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Hypercalcemia

Hyperparathyroidism, Hypervitaminosis D&A, Idiopathic hypercalcemia, malignancy thiazide diuretic abuse,skeletal disorders,immobilisation

Polyuria, polydypsia Volume expansion with saline,

treatment of cause

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Hypomagnesemia

Chronic diarrhoea, sprue, celiac d, prolonged TPN low in Mg, hyperaldosteronism, Gitelman’s syndrome, cisplatin and aminoglycosides

Convulsions, tetany athetoid movements, hyperaccusis

Im or iv magnesium replacement as magnesium sulphate

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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 urine well 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 and

remaining 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. Not drinking ,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 as

0.45% 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 4.8

mmol/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 2nd hour 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 hourly

to 2 hourly Change fluid to 0.18 saline 5% dextrose when blood glucose reaches 16 to

17 mmol/l. Adjust K and insulin infusion rates as needed. Consider an Antibiotic.

When blood gas normal, blood glucose stable, patient drinking, give subcutaneous 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