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MBBS 3: Pediatrics > Fluids and Electrolytes > Flashcards

Fluids and Electrolytes Flashcards

1
Q

Composition of body fluids?

A

Total Body water is high in a fetus
80 % TBW in premature infants
70-75% TBW in infants
60-65% after 1 year to puberty
60% TBW after puberty in males
50% TBW after puberty in female
Note: During dehydration, TBW decreases and is a smaller percentage of body weight

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2
Q

What are the compartments of total body water expressed as percentage of body weight?

A
  1. intracellular - 30-40%
  2. extracellular - 20-25%
    - interstitial - 15%
    - plasma - 5%
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3
Q

Which compartment increases in edematous states such as heart failure, liver failure, and nephrotic syndrome?

A

interstitial

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4
Q

What are the major differences in electrolyte composition between the intracellular and extracellular fluids?

A
  1. Sodium and chloride are the dominant cation and anion in the ECF
  2. Potassium is the most abundant cation in the ICF, and proteins, organic anions, and phosphate are the most plentiful anions in the ICF
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5
Q

Regulation of Intravascular Volume and Osmolality?

A
  1. Maintenance of osmolalitydepends on control of water balance
  2. Control ofvolume statusdepends on regulation of sodium balance
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6
Q

What regulates the intravascular volume and osmolality?

A

the organ with the most important in the regulation of water balance is the Kidneys where Urinary water losses are regulated by the secretion ofantidiuretic hormone (ADH), which increases in response to an increasing plasma osmolality

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7
Q

How does the kidney regulate sodium balance?

A

The kidney regulates sodium balance by altering the percentage of filtered sodium that is reabsorbed along the nephron
- Therenin-angiotensin systemis an important regulator of renal sodium reabsorption and excretion
- The juxtaglomerular apparatus produces renin in response to decreasedeffectiveintravascular volume
- Renin cleaves angiotensinogen, producing angiotensin I, which angiotensin-converting enzyme converts into angiotensin II
- The actions of angiotensin II include direct stimulation of the proximal tubule to increase sodium reabsorption and stimulation of the adrenal gland to increase aldosterone secretion, which increases sodium reabsorption in the distal nephron
- In contrast, volume expansion stimulates the synthesis ofatrial natriuretic peptide, which increases urinary sodium excretion

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8
Q

What are maintenance fluids?

A
  • Estimates the volume required per kg to maintain hydration in healthy children
  • Accounts for insensible losses (from breathing, through the skin)
  • Allows for excretion of the daily excess solute load (urea, creatinine, electrolytes, etc) in a volume of urine with similar osmolarity to plasma
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9
Q

When to give maintenance fluids?

A

Indicated in children who cannot be fed enterally

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10
Q

Maintenance fluids does not include?

A
  1. Replacement for ongoing losses (diarrhea, vomiting drainage)
  2. Deficit replacement(dehydration)
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11
Q

Calculating maintenance fluid volume per day?

A

first 10kg: x100mls/kg/day
second 10kg: x50mls/kg/day
each additional kg: x20ml/kg/day

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12
Q

Calculating maintenance fluid volume per hour?

A

first 10kg: x4ml/kg/hr
second 10kg: x2ml/kg/hr
each additional kg: 1ml/kg/hr

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13
Q

Composition of maintenance fluids?

A
  1. Electrolytes
    - sodium, potassium, and chloride
  2. Water
  3. Glucose
    - provides 20% of normal caloric needs, prevents starvation ketoacidosis and diminishes the protein degradation that would occur if the patient received no calories
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14
Q

What is acidemia?

A

Blood pH less than 7.35
1. Primarily metabolic (↓HCO3)
2. Primarily respiratory (↑pCO2).
3. Mixed acid-base disorder

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15
Q

Causes of metabolic acidosis?

A
  1. Diarrhea or other GI losses
  2. RTA (older children with poor growth)
  3. Medications/toxin ingestions (e.g salicylates)
  4. Inborn Error of metabolism (young infants with poor feeding, FTT, vomiting, lethargy, or seizures)
  5. Diabetic ketoacidosis or ingestions (Unusual breath odors)
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16
Q

Nonspecific symptoms of acidosis are?

A

hyperventilation and Kussmaul breathing
i.e., deep, rapid respirations

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17
Q

What is an anion gap?

A

Anion Gap = Na+– (Cl–+ HCO3–)
- The normal anion gap is 4 to 11 mEq/L, although variations exist among laboratories
- Elevation occurs secondary to an excess accumulation of acids (endogenous or ingested) or inadequate excretion of acids

18
Q

Clinical Manifestations of Hypernatremia?

A

Na⁺ >135 mEq/L
1. Central nervous system symptoms
- Irritable, restless, weak, and lethargic, high-pitched cry and hyperpnoea
- Seizures and coma (cerebral haemorrhage)
2. Fever
3. Alert patients are very thirsty
Note: the pinched abdominal skin of a dehydrated, hypernatremic infant has a doughy feel

19
Q

Causes of respiratory acidosis?

A
  1. Respiratory
    - airway obstruction
    - lung parenchymal disease
  2. Neuromuscular
    - spinal cord pathology tumors
    - Guillain Barre Syndrome
    - Polio
    - CNS depressants
    - Myasthenia Gravis
20
Q

Complications of hypernatremia?

A

Hypernatremia that has developed very slowly should be corrected slowly to avoid the development of cerebral oedema

21
Q

What is hypernatremia?

A

Na⁺ >135 mEq/L

22
Q

Causes of hypernatremia?

A
  1. Volume losses (diarrhea, vomiting) with low intake water
  2. Diabetes Insipidus (DI)
  3. Insensible losses (↑ambient temp, radiant warmer, respiratory distress, hyperventilation)
  4. Poorly prepared formula
  5. Excessive salt intake (e.g., of table salt, poorly prepared ORS)
  6. unconscious patient
23
Q

Signs and symptoms of hypernatremia?

A
  1. Thirst (if conscious)
  2. Neurologic symptoms (e.g., irritability, lethargy, confusion, seizures)
  3. Signs of hypovolemia
24
Q

What are the signs of hypovolemia?

A
  1. lethargy, dry mucous membranes, ↓skin turgor
  2. ↓ tearing and a sunken fontanel in infants
  3. Tachycardia, orthostatic hypotension, and oliguria
  4. Fever (cause/effect)
25
Q

What is hyponatremia?

A

Na⁺ <135 mEq/L

26
Q

Causes of hyponatremia?

A
  1. Renal losses (e.g diuretics)
  2. Extrarenal losses (vomiting, diarrhea, burns)
  3. Water intoxication (e.g i.v. fluids)
  4. Oedema forming states (e.g CCF)
  5. Renal failure (acute or chronic)
  6. Diabetes Mellitus
  7. Pseudohyponatremia (e.g hyperlipidemia)
  8. Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
  9. Hypervolemic states (heart failure, cirrhosis)
27
Q

Signs and symptoms of hyponatremia?

A
  1. Apathy,
  2. anorexia,
  3. nausea, vomiting,
  4. altered mental status, and seizures.
  5. Musculoskeletal: cramps and weakness
28
Q

Rapid correction of hyponatremia can produce?

A

central pontine myelinolysis
- particularly in the pons; patients with extensive lesions can have flaccid quadriplegia, dysphagia, and dysarthria

29
Q

Function of potassium and its regulation?

A

Functions of Potassium (K+)
- Excitability of nerve and muscle cells and contractility of muscles (smooth, skeletal, cardiac).
Regulation
- Aldosterone regulates renal excretion of potassium

30
Q

What is hyperkalemia?

A

K >5.5 mEq/L

31
Q

Causes of hyperkalemia?

A
  1. Hemolysis
  2. Thrombocytosis, leukocytosis
  3. Acidosis
  4. Tumor lysis syndrome
  5. Renal failure
  6. Potassium sparing diuretics
  7. Acute or chronic renal disorders
  8. Tissue breakdown: Trauma, cytotoxic agents, massive hemolysis, rhabdomyolysis, intense exercise
  9. Transcellular shifts: Metabolic acidosis
32
Q

Clinical manifestations of hyperkalemia?

A
  1. Paresthesias
  2. weakness
  3. tingling
33
Q

ECG changes in hyperkalemia?

A
  1. Peaking of the T waves
  2. Increased P-R interval
  3. Flattening of the P wave
  4. Widening of the QRS complex occur
  5. Ventricular fibrillation and asystole
34
Q

Treatment principles of hyperkalemia?

A
  1. shift potassium intracellularly
  2. cardiac membrane stabilization
  3. remove potassium from the body
35
Q

Treatment of hyperkalemia?

A

shift potassium intracellularly
1. sodium bicarbonate administration IV
2. insulin and glucose IV
3. beta agonist (salbutamol via nebulizer)
cardiac membrane stabilization
4. IV calcium
remove potassium from the body
5. loop diuretic IV or PO
6. sodium polystyrene PO or rectal
7. dialysis

36
Q

Importance of treatment of hyperkalemia?

A

rapidly decrease the risk of life threatening arrythmias

37
Q

What is hypokalemia?

A

K < 3.5 mEq/L

38
Q

Classification of causes of hypokalemia?

A
  1. increased renal losses
  2. increased extrarenal losses
  3. redistribution
  4. prolonged decreased intake of potassium
    NB: GI losses of potassium are exacerbated by accompanying volume depletion and subsequent increased aldosterone effects.
39
Q

Causes of hypokalemia?

A
  1. Transcellular shifts
    - Insulin, alkalemia, β-agonists [salbutamol]
  2. Extrarenal
    e.g. Diarrhea, emesis
  3. Renal loses
    e.g. DKA, Renal tubular acidosis, loop diuretics
40
Q

Clinical manifestations of hypokalemia?

A
  1. Electrocardiographic (ECG) changes
    - Flattened T wave, a depressed ST segment
  2. Weakness and cramps.
  3. Paralysis can cause respiratory failure
41
Q

Treatment of hypokalemia?

A
  1. intravenous (IV) potassium should be used cautiously
  2. Oral potassium is safer in nonurgent situations

MBBS 3: Pediatrics (43 decks)

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