A child with hyponatremia

1

• A child with hyponatremia

Constantinos J. Stefanidis
P. A. Kyriakou Children's Hospital, Athens,
Greece
2
The patient
A 12 month old boy had a surgical repair of
inguinal hernia
Wt 10 kg s.Na 139 mmol/L, K 4.4 mmol/L, Cr
0.5 mg/dl, pH 7.38, HCO3 24 mmol/L, Htc 35
IV fluids during the 1st day after surgery 100
ml/kg 0.22 NaCl in D5 (Na 38 mmol/L) K 20
mmol/L
3
The patient
A 12 month old boy had a surgical repair of
inguinal hernia
Wt 10 kg s.Na 139 mmol/L, K 4.4 mmol/L, Cr
0.5 mg/dl, pH 7.38, HCO3 24 mmol/L, Htc 35
IV fluids during the 1st day after surgery 100
ml/kg 0.22 NaCl in D5 (Na 38 mmol/L) K 20
mmol/L
2nd day after surgery Wt 10.6 kg
s.Na 132 mmol/L K 4.1 mmol/L, Cr 0.4 mg/dl,
Htc 31 Urine Specific gravity 1009, Na
22 mmol/L, K 14 mmol/L
4
What is the problem of this patient?
s.Na 132 mmol/L
Hyponatremia s.Na lt136 mmol/L
5
Na and osmolality
Low Na
ICF
ECF
6
Na and osmolality
Low Na
ICF
ECF
7
Total body water (TBW)
ECF
8
Total body water and hyponatremia
Hyponatremia Water retention Normal Na
stores SIADH
Hyponatremia Water retention Na depletion
9
Clinical diagnosis of TBW changes

• Careful evaluation of the history (diarrhea,
  vomiting, thirst, and polyuria)
• Nursing records (daily weights, intake and
  output)
• Physical examination (Heart rate, BP, neck veins,
  peripheral edema, and ascites)

10
Laboratory diagnosis of TBW changes

• Patients with normal or slightly expanded
  extracellular fluid volume are more likely to
  have
• decreased Hct
• normal serum urea
• Urine Na gt 20 mEq/L

11
Diagnosis?

• Increased renal salt wasting.
• Syndrome of inappropriate secretion of
  antidiuretic hormone (SIADH).
• Inappropriate fluid and sodium fluid
  administration.

12
First patient
A 12 month old boy had a surgical repair of
inguinal hernia
Wt 10 kg s.Na 139 mmol/L, K 4.4 mmol/L, Cr
0.5 mg/dl, pH 7.38, HCO3 24 mmol/L, Htc 35
IV fluids during the 1st day after surgery 100
ml/kg 0.22 NaCl in D5 (Na 38 mmol/L) K 20
mmol/L
2nd day after surgery Wt 10.6 kg
s.Na 132 mmol/L K 4.1 mmol/L, Cr 0.4 mg/dl,
Htc 31 Urine Specific gravity 1009, Na
22 mmol/L, K 14 mmol/L
13
What was the ECF volume status of this patient?

• Increased

• Decreased

14
Diagnosis?

• Increased renal salt wasting?

Urine Specific gravity 1009 (240
mOsm/kg) Volume 1.7 ml/kg/hour Na 22 mmol/L K
14 mmol/L
NO
15
Diagnosis?

• Syndrome of inappropriate secretion of
  antidiuretic hormone (SIADH)?

16
Diagnostic criteria of SIADH

• Decreased extracellular fluid effective
  osmolality (lt 270 mOsm/kg H2O)
• Inappropriate urinary concentration (gt 100
  mOsm/kg H2O)
• Clinical euvolemia
• Elevated urinary sodium concentration, with
  normal salt and water intake
• Absence of adrenal, thyroid, pituitary, or renal
  insufficiency or diuretic use.

17
SIADH in children

• Very rare
• In children with brain and lung problems or in
  oncology patients as a side effect of their
  management

18
Diagnosis?

• Syndrome of inappropriate secretion of
  antidiuretic hormone (SIADH)?

NO
19
Diagnosis?

• Inappropriate fluid and sodium fluid
  administration?

IV fluids during the 1st day after surgery 100
ml/kg 0.25 NaCl in D5 (Na 38 mmol/L) K 20
mmol/L
20
Water requirements

• Based on energy expenditure of the average
  hospitalized patient
• First 10 kg 100 ml/kg/day
• Second 10 kg 50 ml/kg/day
• Weight over 20 kg 20 ml/kg/day

Holliday MA, Segar WE. Pediatrics 1957
21
Maintenance fluid requirements

• These calculations of maintenance fluid
  requirements (insensible and urinary water
  losses) were based on energy expenditure,
• assuming 1 ml of water loss was associated with
  the fixed consumption of 1 kilocalorie.

Holliday MA, Segar WE. Pediatrics 1957
22
Comparison of different methods for calculating
caloric expenditure
Taylor, D et al. Arch Dis Child 200489411
23
Energy expenditure in sick children

• Energy expenditure in healthy children, is
  different in acute disease or following surgery
  and is closer to the basal metabolic rate (5060
  kcal/kg/day).

Briassoulis G, et al. Crit Care Med 2000
Verhoeven JJ, et al. Crit Care Med 1998
Coss-Bu JA, Klish WJ, et al. Am J Clin Nutr 2001
24
Energy expenditure and growth

• Almost half of the caloric intake suggested by
  Holliday and Segar is designated for growth.
• In acute diseases this is not a realistic goal.

Coss-Bu JA, Klish WJ, et al. Am J Clin Nutr 2001
25
IWL was estimated to high.

• Insensible water loss was estimated at
• 27 ml/kg/day
• Recent data suggest that it is half of this
• 12 ml/kg/day

26
Urine volume was estimated too high

• It was suggested that urinary water losses for
  healthy children amount to 5060 ml/kg/day
• This was based on urine volumes with an
  "acceptable" osmolarity between 150 and 600
  mosm/l H2O.

27
Increased ADH and hyponatremia

• This concept did not take into account the
  influence of antidiuretic hormone (ADH) on urine
  flow rate.
• When ADH is present, the renal solute load is
  effectively excreted in a smaller urine volume
  (approximately 25 ml/kg/day).

28
Water requirements

• The calculations of maintenance fluids by
  Holliday and Segar are overestimating maintenance
  fluids.
• Hyponatremia due to increased water intake
  happens rarely. In almost all cases of
  hyponatremia, the problem lies in an impaired
  ability of the kidneys to excrete free water due
  to the action of antidiuretic hormone

29
Development of hyponatremia
H2O
ADH
30
Neurological complications of acute hyponatraemia
Children are at high risk for developing
hyponatremic encephalopathy at higher serum
sodium concentrations than adults.

• Because their brain-to-skull size ratio is
  higher, which leaves less room for brain
  expansion.

Playfor S. Arch Dis Child 2003
31
Neurologic morbidity and acute hyponatraemia

• gt50 reported cases and 26 deaths, from
  hospital-acquired hyponatremia in children who
  were receiving hypotonic fluids.
• More than half of these cases underwent minor
  surgery.
• Arieff et al, BMJ, 1992
• 16 previously healthy children who died or
  experienced permanent neurologic damage as a
  result of hyponatremic encephalopathy
• Keating et al, Am J Dis Child, 1991
• Tsimaratos M et al, Arch Pediatr, 1994
• Eldredge EA et al, Pediatrics, 1997

32
Electrolyte-free water (EFW)
The solution of 5 dextrose in

• 0.3 NaCl (or N/3, Na 51 mmol/L)

The EFW input of the patient was 660 ml or 66
ml/kg/day
33
Electrolyte-free water (EFW)
Hoorn EW, et al. Pediatrics 2004
34
How we should calculate water requirements?

• Total fluid loss during acutely illness or
  following surgery is usually half of that
  suggested by Holliday and Segar
• (50-60 ml/kg/day).
• Do not infuse hypotonic solutions if the Na is
  lt138 mEq/L unless the patient is having a rapid
  water diuresis and you want to limit the rise in
  Na.
• Hoorn EW, et al. Pediatrics 2004

Do not infuse hypotonic solutions in maintenance
fluids.
Moritz ML, Ayus. JC Pediatrics 2003 D Taylor and
A Durward. BMJ 2004
35
Prediction of s.Na
Edelman IS et al. J Clin Invest 1958
36
Prediction of s.Na
Infusate Na - Na
Change of Na
TBW 1 L
Edelman IS et al. J Clin Invest 1958
Adrogue HJ, Madias NE. Intensive Care Med 1997
37
Total body water
Lean individuals greater percentage of TBW Fat
individuals smaller percentage of TBW Young
children TBW 65-70 Wt
TBW 60 Weight
38
Calculations of TBW from Wt and Ht
For Boys V
(liters) -1.9 0.46Wt (kg) 0.04Ht (cm)
when Ht lt 132.7 cm
V - 22 0.41Wt 0.21Ht
when Ht gt 132.7 cm For Girls
V 0.07 0.51Wt
0.01Ht when Ht lt 110.8 cm
V -10.3 0.25Wt
0.15Ht when Ht gt 110.8 cm
Cheek DB, Mellits D, Elliott D . Am J Dis Child
1966
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Calculations of TBW from Wt and Ht

• Infants 0 to 3 mo (n 71)
• TBW 0.89 x (Wt)0.83
• Children 3 mo to 13 yr (n 167)
• TBW 0.085 x 0.95 if female x (Ht x Wt)0.65
  
• Children gt 13 yr (n 99)
• TBW 0.075 x 0.84 if female x (Ht x
  Wt)0.69

Morgenstern BZ et al, J Am Soc Nephrol 2002
40
Calculations from BI

• Bioelectrical Impedance (BI) is a fast and
  convenient method for measuring total body water
  content (TBW)

41
Prediction of s.Na
42
Prediction of s.Na
43
The effect of urine volume, Na, K.
44
The appropriate volume and Na of infusate
45
Correction of Na 131 mEq/L
Do not harm
Hippocrates (460-377 BC)
46
Recommendations

• 1. Check electrolytes daily in all children with
  IV fluids
• 2. Monitor urine output and urine Na and K
• 3. Hyponatremic (Na lt 136) patients have
  non-physiologic ADH
• - caution with fluid volumes
• - isotonic saline as initial fluid
• 4. The use of maintenance fluids is
  inappropriate for many of todays hospitalized
  children.

47
Messages to take home

• It is important to determine the exact cause of
  hyponatremia in patients with acute cerebral
  disease
• dilutional in SIADH
• negative sodium balance in CSW
• Inappropriate treatment and fluid restriction in
  patients with CSW might sometimes result in fatal
  hyponatremia and hypovolemia.