Fluid and Electrolyte Management

Question 1

What percentage of a child’s body weight is water, compared to an adult?

Answer 1

WATER

PERCENTAGE BODY WEIGHT

At birth = 80%

Falls gradually with age

In adulthood = 60%

Question 2

What comparments is body water distributed over? What forces affect this?

Answer 2

WATER

COMPARTMENTS OF THE BODY

1. Intravascular
2. Interstitial
3. Intracellular

Affected by pressure and osmotic gradients.

Question 3

How do you work out the fluid requirement for well normal children?

Answer 3

FLUID REQUIREMENT

NORMAL, WELL CHILDREN

First 10 kg 100 ml/kg/ day

Second 10 kg 50 ml/ kg/ day

Subsequent kg 20 ml/kg day

Question 4

What is a normal urine output?

Answer 4

URINE OUTPUT

~ 3 ml/ kg/ hour

Question 5

What are the sources of fluid loss from the body?

Answer 5

FLUID LOSSES

1. Urine ~ 30 ml/ kg/ day or 1-2 ml/ kg/ hr
2. Stool ~ 0 - 10 ml/ kg/ day
3. Insensible losses (sweat, respiration) ~ 10 - 30 ml/ kg/ day - affected by:
   
   • ambient temp/ humidity
   • fever
   • caloric content of feeds
   • skin quality

Question 6

How much fluid much be lost (ml/kg) to cause shock Vs. clinical dehydration and what is the importance of this?

Answer 6

SHOCK = 20 ml/kg lost from intravascular space

CLINICAL DEHYDRATION = at least 25 ml/kg lost before evident (2.5 - 5% dehydration)

i. e. 2.5 ml fluid lost per 100 g body weight
i. e. 25 ml lost for every 1000 g
i. e. 25 ml/ kg

=> SHOCK MAY OCCUR BEFORE CLINICAL SIGNS OF DEHYDRATION!!!

Dehydration may also occur in the absence of shock.

Or both may occur together.

Depends on the rate of fluid loss and rate of fluid shifts.

Question 7

What % dehydration do (a) a child without shock and (b) a child with shock have?

Answer 7

% DEHYDRATION

NO SHOCK: 5% dehydration

SHOCK: = / > 10% dehydration

Question 8

What parameters is pathology from electrolyte changes related to?

Answer 8

ELECTROLYTE DERANGEMENT

Extreme levels

Rapid rates of change

Question 9

What are the clinical signs of dehydration vs. shock?

Answer 9

CLINICAL SIGNS

DEHYDRATION VS. SHOCK

• Clinical appearance:
  
  • unwell Vs. Pale/ lethargic/ mottled
  • Dehydration only
    
    • skin turgor: reduced
    • eyes: sunken
    • fontanelle: depressed
    • mucous membranes: dry (except mouth breathers)
• A + B
  
  • RR: normal / tachypnoea Vs. tachypnoea
• C
  
  • HR: normal/ tachycardia Vs. tachycardia
  • Peripheral pulses: Normal Vs. weak
  • CRT: normal/ mildly prolonged Vs. prolonged
  • extremities: warm Vs. cold
  • BP: normal Vs. low
• D
  
  • GCS: altered responsiveness e.g. irritable, lethargic Vs. decreased
• E
  
  • decreased UO (both)

Question 10

What is the intravascular volume of an infant and of a child? Bearing this in mind, what does e.g. 5% dehydration mean relative to these values?

Answer 10

INTRAVASCULAR VOLUME

Infant = 80 ml/kg

Older child = 70 ml/kg

5% dehydration = loss of 5g fluid per 100g body weight

Extrapolate –> 50 ml in 1000 ml

i.e 50 ml in 1 kg or 50 ml/kg

Question 11

What are the critical clinical questions in the management of fluid and electrolyte management?

Answer 11

FLUID AND ELECTROLYTE Mx

CRITICAL CLINICAL QUESTIONS

1. Shock? –> correct rapidly
2. Dehydration? –> correct over 24 - 48 hrs
3. Acid base abnormality?
4. Electrolyte abnormalities?

Question 12

What is the specific management of shock?

Answer 12

SHOCK Mx

• ABCDEFG
• Fluid bolus
  
  • 20 ml/kg
  • 10 ml/kg in raised ICP, trauma, cardiac pt’s
  • 0.9% saline
  • care if using Hartmann’s esp. in renal impairment - contains K+
  • hyper and hyponatraemia do not affect choice of fluid during initial resus
• Electrolyte abnormalities
  
  • correct slowly UNLESS
    
    • dysrhythmia
    • neuro abnormality
• Treat shock 1st before turning attention to hydration status/ Mx of dehydration

Question 13

What is the only clinical available objective measure of total body fluid changes? What measure is used in emergency situations and why?

Answer 13

The only clinically available objective measure of total body fluid changes = WEIGHT

In emergencies, pre-sickness weight often not available.

So have to use clinical signs of dehydration to estimate degree of dehydration.

Question 14

Define 5% and 10% dehydration. What do these values actually represent?

Answer 14

5% DEHYDRATION

= LOSS of 5 ml of fluid per 100g of body WT

= loss of 50 ml of fluid per 1000 g of body WT

= 50 ml/ kg

10% DEHYDRATION

= LOSS of 100 ml/ kg

Question 15

Describe the specific management of dehydration.

Answer 15

DEHYDRATION Mx

• ABDCEFG
• Daily maintenance + Replacement
• over a 24 hour period
• monitor every 3-6 hrs
• use WT as an objective measure - appropriate rate of gain
• crystalloids
• Route
  
  • Oral
    
    • oral rehydration solution is preferable if the gut is functioning
    • use cup and spoon
    • Continue normal feeds in addition to solution esp. if breast fed
  • IV
    
    • if excessive vomiting or damaged gut
    • attempt gradual re-introduction of oral rehydration during IV therapy unless there is bowel damage
    • if tolerated then stop IV completely

Question 16

Describe the composition of the commonly available crystalloid fluids:

1. Sodium Chloride 0.9%
2. Sodium Chloride 0.45% + dextrose 5%
3. Hartmann’s solution
4. Dextrose 5%
5. Dextrose 10%

Answer 16

See image.

Question 17

Describe the fluid management of a 6 kg child who is clinically shocked and 10% dehydrated as a result of gastroenteritis.

Answer 17

6 kg child

• SHOCK
  
  • 20 ml/kg 0.9% saline
  • 20 x 6 = 120 ml
• INFUSION = DEHYDRATION + MAINTENANCE
  
  • DEHYDRATION
    
    • 10% i.e. loss of 100 ml/kg of body weight
    • 100 x 6 = 600 ml
  • MAINTENANCE = 100 ml for the first 10 kg, 50 ml for the 2nd 10 kg, 20 ml/ kg thereafter
    
    • 100 x 6 = 600 ml
  • TOTAL DEHYDRATION REPLACEMENT + MAINTENANCE = 1200 ML
    
    • over 24 hours
    • 1200 / 24 = 50 ml / hr
• Monitoring
  
  • weigh after 4-6 hrs
    
    • losing weight –> increase fluid rate
    • excessive weight gain –> decrease rate
    • satisfactory –> continue
  • tolerating oral fluids then start giving more of maintenance fluid as oral feeds

Question 18

What can excessive fluid administration cause?

Answer 18

EXCESSIVE FLUID ADMINISTRATION

1. Intravascular fluid overload
2. Overhydration
3. Both

Question 19

Describe the relative risk of dehydration and fluid overload in paediatric patients with the following conditions:

1. Nephrotic syndrome
2. Myocardial dysfunction
3. Renal impairment

Answer 19

• Nephrotic syndrome
  
  • low serum albumin
  • fluid leaks out of the intravascular space into the tissues
  • diffuse severe oedema
  • BUT intravascular space MAY be fluid DEPLETED
  • => may need to replace fluid before diuresing to avoid shock
• Myocardial dysfunction
  
  • intravascular compartment overfilled
  • signs of fluid overload
  • BUT on diuretics
  • MAY also be dehydrated due to total body fluid depletion
• Renal impairment
  
  • intravascular AND total body FLUID OVERLOAD
  • giving more fluid –> pulmonary oedema

Treatment of fluid overload can be complex.

Always d/w an expert.

Question 20

What are the normal daily requirements in well, normal children for the following:

1. Water (ml/ kg/ day)
2. Sodium (mmol/ kg/ day)
3. Potassium (mmol/ kg/ day)
4. Energy (kcal/ day)
5. Protein (g/ day)

Answer 20

See image.

Question 21

What is severe hypernatraemia associated with?

Answer 21

HYPERNATRAEMIA

SEVERE

• HIGH serum sodium
• brain cells becmome dehydrated
• brain tissue shrinks
• blood vessels assoc. w/ the brain tissue may tear or clot
• BRAIN DAMAGE

Question 22

What does rapid correction of the following cause?

1. HYPERnatraemia
2. HYPOnatraemia

Answer 22

RAPID CORRECTION

• HYPERnatraemia – remember HYPER C*NT
  
  • cerebral oedema
  • CONVULSIONS
• HYPOnatraemia – remember HYPO D***
  
  • DEMYELINATION
  • permanent BRAIN INJURY

Question 23

Describe the degree of sodium loss in the following conditions:

1. Rotavirus Gastroenteritis/ diarrhoea
2. Cholera & enteropathogenic E. Coli diarrhoea
3. Diabetes insipidus
4. Renal tubular dysfunction

Answer 23

SODIUM LOSS

1. Rotavirus Gastroenteritis/ diarrhoea
   
   • 50 mmol/L
2. Cholera & enteropathogenic E. Coli diarrhoea
   
   • 80 mmol/L
3. Diabetes insipidus
   
   • minimal
4. Renal tubular dysfunction
   
   • high

Question 24

Describe the causes of HYPERnatraemia in the DEHYDRATED patient.

Answer 24

HYPERnatraemia in the DEHYDRATED patient

CAUSES

• LOSS (excessive) – WATER e.g.
  
  • Diabetes insipidus
  • Diarrhoea
• INTAKE (excessive) – SODIUM e.g.
  
  • Iatrogenic
  • Poisoning - NAI
• COMBINATION e.g.
  
  • gastroenteritis/ diarrhoea AND
  • excessive sodium in rehydration fluid

Question 25

What do consensus guidelines recommend as the starting fluid for deficit replacement and maintenance for hypernatraemic dehydration? Why?

Answer 25

FLUID OF CHOICE HYPERNATRAEMIC DEHYDRATION 1. 0.9% SALINE 2. 0.9% SALINE + 5% DEXTROSE 0.45% Saline no longer used - hypotonic solution - led to a rapid fall in sodium

Question 26

What can be used as a guide for fluid replacement therapy in children with renal tubular dysfunction, OTHER than serum sodium?

Answer 26

1. Urine sodium 2. Urine osmolality 3. Stool sodium

Question 27

Describe the treatment of HYPERnatraemia.

Answer 27

HYPERNATRAEMIA Mx 1. Treat SHOCK * 20 ml/ kg (or 10 ml/kg in trauma, cardiac pts, raised ICP) * 0.9% saline 2. Treat Dehydration - work out: * replacement * maintenance * total & rate * clinically assess and weigh frequenty 3. Lower SODIUM: * rate NOT \> 0.5 mmol/ hour 4. Electrolytes * check potassium, calcium * monitor frequently * expert advice if not improving 5. GLUCOSE - check

Question 28

What causes hyponatraemia (in principle)?

Answer 28

HYPONATRAEMIA CAUSES 1. LOSS of SODIUM (excessive) 2. REDUCED INTAKE e.g. dehydration 3. DILUTION * excessive water intake * water retention 4. COMBINATION

Question 29

Describe the management of HYPOnatraemia.

Answer 29

HYPONATRAEMIA Mx 1. Seizures * 3% saline 4 ml/kg * over 15 mins * raises Na ~ 3 mmol & usually stops seizures 2. Treat shock 3. Hydration - Calculate dehydration fluid deficit & maintenance * dehyration - start infusion 0.9% saline * excessive water intake/ retention - restrict to 50% normal requirement * clinically assess hydration & weigh frequenly 4. RAISE SODIUM * NOT \> 0.5 mmol/ hour 5. Electrolytes * check others e.g. K+, Ca2+ * monitor frequently * expert advice if not improving 6. GLUCOSE - check

Question 30

Are the following mainly intracellular or extracellular ions? 1. Sodium 2. Potassium

Answer 30

Sodium - extracellular Potassium - intracellular

Question 31

What is the role of intracellular potassium and what can happen when this mechanism fails? What must occur for this mechanism to fail?

Answer 31

Intracellular potassium is a buffer which maintains the serum value within a narrow range. Outside of this range - cardiac arrhythmias. It is a very large buffer so clinical signs of hypokalaemia will only manifest when there is sig. TOTAL BODY DEPLETION. The reverse is true for hyperkalaemia i.e. sig. total body overload, beyond the ability of the kidney to compensate OR massive breakdown of RBC's.

Question 32

Describe the causes of hypokalaemia.

Answer 32

**_HYPO_**KALAEMIA CAUSES VITAMIN CD * Vascular volume depletion * Infectious: Diarrhoea * Metabolic: aLKalosis (Low K), primary hyperaldosteronism (Na+ retention, K+ excretion) * Drugs: diuretic abuse

Question 33

Describe the causes of HYPERkalaemia.

Answer 33

HYPERkalaemia CAUSES * _EXCESSIVE INTAKE_ + * Vascular: cell lysis (released from RBC), inadequate CO (in the critically ill neonate) * Metabolic: renal failure (MOST COMMON), acidosis, adrenal insuffiency, hypoaldosteronism

Question 34

Describe the management of hypokalaemia.

Answer 34

HYPOKALAEMIA Mx * rarely an emergency * usually the result of losses from diarrhoea ie. total body depletion * Mx 1. Oral (if possible) 2. IV * do NOT exceed 40 mmol/L (i.e. 20 mmol in 500 ml) * unless given centrally w/ cardiac monitoring (pptates arrythmia) * Hypokalaemia due to: * alkalosis * salbutamol * insulin * high intracellular K+ stores * redistribution of K+ into cells * not a true K+ deficiency * =\> treat the underlying cause

Question 35

Describe the emergency management of hyperkalaemia.

Answer 35

HYPERKALAEMIA Mx * dangerous * arrythmias at 7.5 mmol/ L (rarely below) * ensure not spurious result from squeezed sample (lyses blood cells) * MONITOR * ECG, BP * UO * WT * U+Es incl. Ca2+ - often low if hyperkalaemia esp. in sepsis/ renal failure 1. **STOP** * **K+** in * diet * fluids * **drugs** that cause HyperK * ACE inhibitor * angiotensin II blockers * b-blockers 2. **Rpt** urgently ? haemolysis or lab result from a long time ago 3. **ARRHYTHMIA?** * e.g. heart block, ventricular arrythmia * apply continuous ECG monitoring * YES --\> **CALCIUM** 0.1 mmol/ kg IV * has no effect on K+ * Stabilise myocardium IF: * ECG changes * K+ sig. \> ULN or rising * **10% calcium gluconate** 0.5 - 1 ml/kg * max 20 ml * over 5 mins * undiluted * effect w/i mins, lasts ~1 hr * rpt w/i 5-10 mins if necessary * NO --\> 4. **SALBUTAMOL** (2.5 - 10 mg NEB) * shifts K+ into cells * \< 2 yo = 2.5 mg * =/\> 2 yo = 5 mg * rpt 2 hrly * effect w/i 30 mins but max effect at 60-90 mins 5. **Repeat K+** * **Falling --\> CALCIUM RESIONUM** 1g/kg PO/PR **(F\*C\*)** * or ? 250 mg/ kg, max 15 g * 6 hourly * PR - rpt if expelled w/i 30 mins * removes K+ from the body * PO unpalatable - limited use * + consider specific arrhythmia protocol * --\> Dialysis if necessary (needs specialist centre) * **High (Glucose makes you high!)** * pH \> 7.35 * **Glucose** 10% 5 ml/kg/ hr (20% at 2.5 - 5 ml/ kg/ hr if central access) * BEWARE large volumes of fluid in renal failure * AIM blood GLU 10-15 mmol/L * physiological homeostasis will increase insulin production * if _blood sugar \> 15 after 1 HOUR_ --\> * **+/- Insulin** 0.05 units/ kg/ hr IV * 50 units of insulin * in 50 ml 0.9% saline * = 1 unit/ ml * maintain blood glucose 10-15 * adjust infusion rate in steps of 0.05 ml/ kg/ hr * monitor GLU * 15 min after starting/ changing dose * --\> every 30 mins until stable * --\> Calcium resonium * --\> Dialysis if necessary * pH \< 7.34 * **Sodium bicarbonate** 1-2 mmol/kg IV * 1 mmol = 1 ml of 8.4% NaHCO3 * dilute 1:5 in 5% dextrose * over 30 mins * --\> Repeat K+ * --\> Back to the top of STEP 3

Question 36

How does salbutamol work in the management of hyperkalaemia?

Answer 36

HYPERKALAEMIA SALBUTAMOL * stimulates cell wall pumping mechanism * increases cellular uptake of K+ * works within 30 mins * administered via neb * K+ falls by 1 mmol/L with doses of 2.5 - 10 mg

Question 37

How do you monitor a patient with hyperkalaemia?

Answer 37

HYPERKALAEMIA MONITORING * ECG * continuous * Tented T waves, absent P waves (first signs) * BP * Sats * UO * WT * U+E - recheck urgently ? haemolysed sample ? sample repeated a long time ago

Question 38

How does sodium bicarbonate work in the treatment of hyperkalaemia? What other electrolyte must be measured frequently when using sodium bicarbonate as treatment for hyperkalaemia and why?

Answer 38

SODIUM BICARBONATE HYPERKALAEMIA * Promotes intracellular K+ uptake * effect is greater in acidotic pts * in these pt's hyperK+ is the result of K+ moving out of the cells * ALWAYS CHECK CA2+ * Hyperkalaemia often accompanied by HYPOcalcaemia esp. in sepsis/ renal failure * using bicarbonate can cause a crisis by quickly lowering the ionised calcium fraction --\> TACH: * Tetany * Arrythmias * Convulsions * Hypotension

Question 39

What are the only treatments that remove K+ from the body in the management of hyperkalaemia? What is the significance of this?

Answer 39

The ONLY treatments that REMOVE K+ from the body are 1. CALCIUM RESIONIUM (ion exhange resin) 2. DIALYSIS All other Rx's REDISTRIBUTE K+ into cells. This DELAYS rather than TREATS the problem.

Question 40

Discuss some of the causes of hypocalcaemia.

Answer 40

HYPOCALCAEMIA CAUSES VITAMIN CDE * Inflammatory: pancreatitis * Infectious: sepsis * Trauma: rhabdomyolysis * Iatrogenic: citrate infusion e.g. massive blood transfusion * Endocrine: severe rickets, hypoPTH, acute and chronic renal failure

Question 41

Name some of the symptoms of hypocalcaemia.

Answer 41

HYPOCALCAEMIA SYMPTOMS * Neuro: weakness, tetany, convulsions * CVS: hypotension, arrhythmias

Question 42

Discuss the management of hypocalcaemia.

Answer 42

HYPOCALCAEMIA Mx * treat the underlying condition * IV Calcium in emergency followed by central line infusion * Calcium IV is irritant * acute doses often only transient effect as most causes of hypocalcaemia will cause sig. total body depletion * Oral phosphate binders or DIALYSIS * in renal failure * because low ca2+ often accompanied by high phosphate * this prevents the calcium level from rising

Question 43

How does hypercalcaemia usually present?

Answer 43

HYPERCALCAEMIA PRESENTATION LONG-STANDING: * Anorexia * Vomiting * WT loss * Failure to thrive * Malaise

Question 44

What are some of the causes of hypercalcaemia?

Answer 44

HYPERCALCAEMIA CAUSES VITAMIN CDE * Iatrogenic/ Drugs: Thiazide diuretic abuse * Neoplastic: Malignancy * Congenital: skeletal disorders, idiopathic hypercalcaemia of infancy * Endocrine: hyperPTH, hypervitaminosis D or A

Question 45

Describe the management of hypercalcaemia.

Answer 45

HYPERCALCAEMIA Mx * 0.9% Saline (volume expansion) * FUROSEMIDE * specific Rx for condition

Question 46

Describe the pathophysiology of DKA.

Answer 46

DKA PATHOPHYSIOLOGY Relative or Absolute LACK of INSULIN 1. Inability to metabolise GLUCOSE 1. HYPERGLYCAEMIA 2. OSMOTIC DIURESIS 3. UO exceeds the ability of pt to drink 4. DEHYDRATION 2. FAT is used as a source of energy 1. KETONES produced 2. Metabolic ACIDOSIS 3. Hyperventilation to compensate (resp alkalosis) = Kussmaul breathing i.e. deep, sighing respirations 3. COMA - due to a combination of HAD: * HYPEROSMOLARITY * ACIDOSIS * DEHYDRATION

Question 47

Who experiences DKA?

Answer 47

DKA 1. First presentation of T1DM 2. Known diabetes - decompensation due to: 1. Illness including Infection 2. Non-compliance w/ treatment

Question 48

What are the typical symptoms of DKA?

Answer 48

DKA SYMPTOMS/ HISTORY * abdominal pain (central) * polyuria + polydipsia / nocturnal enuresis * weight loss * vomiting NB symptoms less specific in \< 5 yo They are also more prone to ketoacidosis.

Question 49

Describe the examination findings in DKA. What additional signs should alert you to the possibility of sepsis causing decompensated diabetes?

Answer 49

DKA Signs * General: smell of ketones * Neuro: drowsy/ reduced consciousness * CVS: signs of dehydration * Resp: Kussmaul respirations (deep, sighing, rapid) * Sepsis: * fever/ hypothermia * hypotension * acidosis: refractory or lactic

Question 50

What differential diagnoses should be considered in DKA?

Answer 50

DKA DIFFERENTIAL DIAGNOSES 1. Salicylate poisoning 2. Uraemia

Question 51

Describe the management of DKA.

Answer 51

DKA MANAGEMENT * A * assess patency * airway opening manoeuvres * adjuncts * consider intubation * B * 100% O2 * C * cardiac monitor ? peaked T-waves, absent p-waves (hyperkalaemia in DKA) * IV access * Bloods: * Baseline incl. U+E, creat, FBC * leucocytosis common in DKA, not necessarily due to infection * gas * GLU * KETONES * +/- BCx * FLUIDS 1. Fluid bolus 10 ml/kg * SHOCK ONLY * SLOWLY * not routine * seek specialist advice if 2nd bolus needed 2. Fluid REPLACEMENT for DEHYDRATION (**_over 48 hrs_**) * do NOT subtract the first 20 ml/kg of boluses * DO subtract any subsequent boluses from replacement volume * BEWARE risk of cerebral oedema with rapid fluid replacement * Calculation * **pH \< 7.1 = SEVERE** DKA * **10%** fluid deficit * **pH \> 7.1 = MILD - MOD** DKA * **5%** fluid deficit 3. MAINTENANCE * 'REDUCED VOLUME' RULES * risk of cerebral oedema * \< 10 kg = 2 ml/ kg/ hr * 10 - 40 kg = 1 ml/ kg/ hr * \> 40 kg = 40 ml/ hr (fixed volume) 4. TOTAL * Hourly rate = (deficit/ 48 hrs) + maintenance per hour * avoid hypoK * avoid rapid changes in serum osmolarity * Inotropes * for hypotensive shock * d/w CATS/ PICU * E * NGT * URINE: dip - sugar, ketones +/- M/C/S * Fever * BCx * CSF * throat swab * CXR * urine M/C/S * G * gas and lab glucose * dip urine for glucose * Insulin * 1-2 hrs AFTER fluids started * soluble insulin infusion * 0.05 - 0.1 units/ kg/ hour * aim glucose near normal levels * avoid hypoglycaemia

Question 52

Describe the major complications of DKA, for which intensive monitoring is required on ICU.

Answer 52

DKA MAJOR COMPLICATIONS 1. NEURO = **CEREBRAL OEDEMA** * most important cause of death & poor neuro outcome * Avoid by: * slow normalisation of osmolarity * pay attention to Na+ and glucose level * rehydrate SLOWLY over 48 hrs * Sx - monitor for: * neuro: headache, irritability, altered GCS * CVS: bradycardia and HTN/ rising BP * Resp: hyperventilation - assoc. w/ worse outcome * Gastro: recurrence of vomiting * Mx * 3% hypertonic saline 3 ml/ kg * 20% mannitol 250-500 mg/ kg 20 mins 2. CVS = **CARDIAC DYSRHYTHMIAS** * **​​**usually 2ndary to electrolyte disturbances * especially K+ 3. RESP = **PULMONARY OEDEMA** * ​​replace fluid carefully * avoid overloading 4. RENAL = **ACUTE RENAL FAILURE** * ​​uncommon - because of high osmotic urine flow