dehydration

1. 73: PEDIATRIC DEHYDRATION
INTRODUCTION
 Less tolerance to fluid/lyte changes b/c of higher metabolic rate in kids versus adults
 Turnover of fluids and solute 3Xs that of adult
 Higher % TBW (75% in neonate, 65% in child, 60% in adult)
APPROACH TO DEHYDRATION: THE FIVE POINT ASSESSMENT...
 What is the volume deficit?
 Estimation by clinical assessment of % dehydration X body weight
 Does an osmolar deficit exist?
 Hyponatremic (hypotonic) dehydration = Na < 130
 Isonatremic (isotonic) dehydration = Na 130 - 150
 Hypernatremic (hypertonic) dehydration = Na > 150
 Does an acid - base deficit exist?
 Loss of bicarbonate in diarrhea ----> normal anion gap metabolic acidosis
 Ketoacidosis (lipolysis- poor oral intake --> increased anion gap met
acidosis
 Lactic acisosis (tissue hypoperfusion) —> increased anion gap met
acidosis
 Respiratory alkalosis as compensation for above
 Does a potassium disturbance exist?
 K+ loss in diarrheal stools
 Typical deficits: isonatremic (8-10 mEq/kg), hypoonatremic (8-10 mEq/kg)
hypernatremic (0-4 mEq/kg)
 Serum K+ not reflective of total bd K+ b/c of shifts (acid/base disturbance)
 High K+: K+ replacement needs to be cautious, watch for renal failure
 What is the renal function?
 Pre-renal versus renal failure: Urine Na, FE Na, urine sediment, etc
MAINTENANCE REQUIREMENTS
 Fluid losses
 50% urine
 50% insensible (2/3 derm, 1/3 resp)
 Fluid requirement
 4:2:1 rule per hour or 100:50:20 rule per 24hr
 4cc/kg/hr for 0 - 10kg: 2cc/kg/hr for 10 - 20kg: 1cc/kg/hr for > 20kg
 100cc/kg/24hr for 0-10: 50cc/kg/24hr for 10-20: 20cc/kg/hr for > 20kg
 Caloric requirement
 Same 4:2:1 rule to determine Kcal/kg/hr or 100:50:20 rule for daily caloric
requirement
 Electrolyte requirements
 Na+ requirement is 3mEq/kg/24hr
 K+ requirement is 3mEq/kg/24hr
 Kidney produces enough bicarbonate therefore not required
 Glucose: 5g glucose per 100ml maintenance fluid enough to prevent
ketosis
 Requirements will increase with fever, ventilation, inc. activity, etc
DEFICITS/DEHYDRATION
 Loss is mainly from ECF

2.  Estimate by: (wt b/f - wt a/f)/wt b/f = % dehydration.
 Rarely have accurate wt b/f :. must estimate clinically
 History
 Intake: what, how much?
 Output: urine, sweat, feces, vomiting? how much?
 Lethargic, activity level
 Physical Examination
 Gen: irritable, restless, lethargic, looks unwell
 Vitals: temp, RR, HR, BP, cap refill, wt
 H/N: mucous mem, eyes sunken, fontanelle, tearing
 Derm: skin turgor
 Clinical Estimation (note that 1cc = 1gm)
 Mild: 0 - 5% X body weight (5% X 10kg = 500cc)
 Moderate: 5 - 10% X body weight (10% X 10kg = 1000cc)
 Severe: 10 - 15% (15% X 10 kg = 1500cc)
History + History + History +
NO physical physical severe physical
findings findings findings
MILD MODERATE SEVERE
% < 5% 6 - 10% > 10%
Appearanc
e
Thirsty, alert,
restless
Thirsty, drowsy,
orthostatic
Lethargic, limp, cold
Vitals Normal radial pulse
and RR,
BP normal
Rapid but strong
radial pulse,
increased RR,
BP normal
Rapid and weak
radial pulse,
increased RR,
BP normal or low
H/N Normal fontanelle
Moist mucous mem
Normal eyes
Tears
Sunken fontanelle
Dry mucous mem
Sunken eyes
Absent tears
Very sunken
fontanelle
Parched mucous
mem
Very sunken eyes
Absent tears
SKIN Cap refill < 2sec
No tenting
Cap refill 3 - 4 sec
Mild tenting
Cap > 5 sec
Marked tenting
GENERAL Normal urine
Loss of 40 - 50 ml/kg
Reduced, dark urine
Loss of 60 - 100
ml/kg
Reduce or no urine
Loss of > 100 ml/kg

3. PATHOPHYSIOLOGY
 Isonatremic (Isotonic) Dehydration: 80%
 [Na] between 130 - 150
 Roughly equal losses of Na and water
 NO change in body tonicity or redistribution of fluid between extra and
intravascular spaces
 Hyponatremic (hypotonic) Dehydration: 5%
 [Na+] is < 130 mmol/L
 Sodium loss > water loss
 Most common cause is sodium poor replacement of GI loss
 Child appears relatively more ill than expected b/c water shifts from ECF
to ICF :. there is less intravascular volume and more physical signs
 Na < 120: seizures, coma
 Cerebral edema can lead to seizures
 Hypo-osmolar demyelination syndrome,most commonly seen as
central pontine myelinolysis, can occur. Uncertain whether these are
due to hyponatremia itself or too rapid correction of Na+. Pathophysiology
unknown. Thought to be due to rapid correction in chronic hyponatremia.
Neurological findings include fluctuating LOC, behavioral disturbances,
convulsions progressing to pseudobulbar palsy and quadraparesis.
 Hypernatremic (Hypertonic) Dehydration: 15%
 [Na+] > 150 mmol/L
 Water loss > sodium loss or increased Na+ intake (incorrect formulas)
 Child appears relatively less ill than it is b/c water shifts from ICF to ECF :.
there is more relative intravascularvolume and less physical signs
 Risk: brain hemorrhage, SZ, coma, death
 Do NOT correct rapidly w/ hypotonic solution b/c of brain shifts which can
cause massive brain swelling
 May have alternating LOC b/w lethargy and hyperirritability
 PE: dry, rubbing, doughy skin w/ inc muscle tone (doughy skin b/c
hypertonicity of body fluids in subcutaneous tissues)
 Risk: intracellular dehydration :. water shifts out of the brain cells. This
stress causes production of idiogenic osmols (glycine and taurine) which
prevents ongoing water loss from neurons. If serum Na is lowered too
quickly, these idiogenic osmols will then attract water into brain cells
causing swelling, massive cerebral edema, and intractable seizures.
MUST correct serum Na slowly, and remember that tissue/renal
perfusion is maintained w/ high Na
MANAGEMENTOF SEVERE DEHYDRATION
 Approach is ABCs with emphasis on iv access
 ALL types of severe dehydration require a fluid bolus of 20 cc/kg of 0.9% NaCl or
Ringers
 Theoretical risk of acidosis with normal saline: infusion of NaCl dilutes the extracellular
HC03- creating a “dilutional acidosis”. Ringers lactate has some HCO3 in it.
 Reassess q 5-10 min after bolus and repeat as needed X 2
 Avoid glucose containing solutions for initial resuscitation of severe dehydration
 If hypoglycemic: give 2ml/kg D25W (children) or 4ml/kg DW10 (infants)if hypoglycemic
 Consider colloids (albumin, FFP, synthetics) if renal, cardiac, or pulmonary dz
 Consider differential dx of shock if nonresponsive to 3 boluses (>60 ml/kg): septic, spinal,

4. hypovolemic, hemorrhagic, obstructive, cardiogenic, anaphylactic, other
ISONATREMIC DEHYDRATION
 Phase I (0 - 20min): Bolus 20 cc/kg X 3 prn of normal saline, lactate ringers
 Phase II (0 - 8hrs): Infusion with D5W 0.45% normal saline (D5W ½ NS)
 Add 20 mEq/L KCL after urine output established
 Rate cc/hr = (½ deficit - bolus) + maintenance X 8hrs + ongoing losses
8 hours
 Phase III (8-24hrs): Infusion with D5W 0.45%NS
 Adjust according to urine output if neccessary; monitor lytes
 Rate cc/hr = ½ deficit + maintenance X 16hrs + ongoing losses
16 hours
HYPONATREMIC DEHYDRATION
 Phase I (0-20min): Bolus 20 cc/kg X 3 prn of NS or LR
 Phase II (0-8hrs)
 If not seizing ...
- administer D5W ½ NS with objective to raise serum Na by
no more than 12 mEq/L over 24hrs
- no NaCl bolus necessary
- rate cc/hr = (½ deficit - bolus) + maintenanceX8hrs +
losses 8 hours
 If seizing...
- Na deficit = (desired - current [Na]) X TBW X weight (kg)
- Na deficit = (120 - [Na]) X 0.6 X kg
- replace with 3% saline (0.5 mEq/ml or 513 mEq/L)
- use 120 as desired Na to prevent rapid overcorrection
- proceed with fluids to raise Na by no more than 12 mEq/L
over next 24hrs; monitor lytes
- after 3% saline, use D5W ½ NS
- rate cc/hr = (½ deficit - bolus) + maintenanceX8hrs +
losses 8 hours
 Phase III (8-24hrs)
 DW5 ½ NS
 Rate cc/hr =1/2 deficit + maintenance X 16hrs + ongoing losses
16 hours
HYPERNATREMIC DEHYDRATION
 Phase I: Bolus 20 cc/kg NS X 3 prn
 Phase II/III
 Treat shock and give fluids to replace deficits over 48hrs (vs 24hr)
 Reduce serum Na by no more than 10 mEq/L/24hrs
 Dialysis for SeNa > 210 mEq/L
 Acceptable solutions: D5W0.45%NS or D5W0.2%NS
 NOTE that rate of solution more important than type of solution
 Rate cc/hr = (½ deficit - bolus) + maintenanceX24hrs + ongoing losses
24 hours
SPECIAL SITUATIONS

5.  Acidosis
 Regardless of type of dehydration, pt may b/cm acidotic from lactate
secondary to poor perfusion, ketone production, or bicarbonate loss in
diarrhea
 Most recover spontaneously with rehydration
 Consider HCO3- for pH < 7.0 or HCO3 < 10 (debatable)
 NaHCO3 deficit = 20 - SeHCO3 X 0.6 X kg
 Remember that HCO3 can cause severe K+ shifts and paradoxical CSF
acidemia
 Do not fully correct acidosis
 Potassium
 Remember shifts; ddx is mainly GI vs renal loss
 Always ensure urine output and renal function before replacing K+
 Replace with 20 - 40 mEq Kcl/L
 Maximum is 60 mEq/L in peripheral iv
 Replace potassium gradually over 2 days
ORAL REHYDRATION THERAPY (ORT)
 Contraindications to oral rehydration therapy
 Severe dehyration/shock
 Lethargy
 Acute abdomen
 Intestinal obstruction
 Underlying complicating illness
 Failure of oral rehydration therapy
 Circulatory collapse
 Increasing deficit despite ORT
 Deterioration during ORT
 Intractable vomiting
 Failure to rehydrate in 8hrs
 Technique
 Rehydrate in ED over 4hrs, reassess
 Review contents of pedialyte, WHO solution, gatorade, apple juice, soup,
etc
 D/C home at 4 hours if rehydrated, continue if not
 D/C home or admit at 8 hours
 Give 1/4 of target volume Q1hr X 4
 Target volumes
- mild = 60 ml/kg, moderate = 80 ml/kg
- or: deficit + maintenance + ongoing losses
 Controversy/Discussion
 Why is glucose needed? the absorption of Na occurs by a Na/Glucose
cotransporter which remains functional during diarrhea (even secretory)
 Is there a role for NG placement and rehydration vs oral vs iv rehydration
 Does it make sense to give frequent small volumes/sips to thirsty infant to
try to prevent vomiting?
 Dehydration with “Vomiting after every drink” ....... some goes up, some
goes down. Note studies with administration of drug followed immediately
by ipecac: < 50% of drug is recovered thus at least ½ is going down.

6. APPROACH TO PEDIATRIC DEHYDRAITON
1. Initial Resuscitation
 Emphasis on iv access and bolus administration of 20 cc/kg prn X3
for severe dehydration/shock
2. Determine % Dehydration (volume of deficit)
 Mild: <5%
 Moderate: 6 - 10%
 Severe: > 10%
3. Define Type of Dehydration: osmolar deficit?
 Hyponatremic (hypotonic): Na < 130
 Isonatremic (isotonic): Na 130 - 150
 Hypernatremic (hypertonic): Na > 150
4. Determine Type and Rate of Fluids
 Calculate deficit, maintenance, ongoing losses
5. Final Considerations
 Does an acid - base deficit exist?
 Does a potassium disturbance exist?
 What is the renal function?
MAINTENANCE
4:2:1 RULE =
0 - 10 kg: 4cc/kg/hr
10 - 20 kg: 2cc/kg/hr
> 20 kg: 1cc/kg/hr
100:50:25 RULE =
0 - 10 kg: 100cc/kg/24hr
10 - 20 kg: 50 cc/kg/24hr
> 20 kg: 25 cc/kg/24hr

7. DEFICIT
HOW DO YOU ASSESS % DEHYDRATION
MILD MODERATE SEVERE
% < 5% 6 - 10% > 10%
Appearanc
e
Thirsty, alert,
restless
Thirsty, drowsy,
orthostatic
Lethargic, limp, cold
Vitals Normal radial pulse
and RR,
BP normal
Rapid but strong
radial pulse,
increased RR,
BP normal
Rapid and weak
radial pulse,
increased RR,
BP normal or low
H/N Normal fontanelle
Moist mucous mem
Normal eyes
Tears
Sunken fontanelle
Dry mucous mem
Sunken eyes
Absent tears
Very sunken
fontanelle
Parched mucous
mem
Very sunken eyes
Absent tears
SKIN Cap refill < 2sec
No tenting
Cap refill 3 - 4 sec
Mild tenting
Cap > 5 sec
Marked tenting
GENERAL Normal urine
Loss of 40 - 50 ml/kg
Reduced, dark urine
Loss of 60 - 100
ml/kg
Reduce or no urine
Loss of > 100 ml/kg
History + History + History +
NO physical physical severe
findings findings phys
findings
DEFICIT = % DEHYDRATION x BODY WEIGHT (1cc = 1gm)

8. 5% dehydrated X 10 kg = 0.05 X 10000cc = 500cc
10% dehydrated X 10kg = 0.10 X 10000cc = 1000cc
15% dehydrated X 10 kg = 0.15 X 10000cc = 1500cc
CALCULATIONS IN PEDIATRIC DEHYDRATION
CASE 1:
 1yr old (10kg) vomiting and diarrhea X 4 days
 Slightly drowsy, not lethargic, good tone, warm, tacchycardic, strong
pulse, normal BP, dry mucous mem, dry eyes, cap refill 3 sec
 Na = 132, K+ = 3.2, HCO3 = 20
 What fluid and what rate would you use for the first 24hrs? Assume
minimal ongoing losses.
CASE 2:
 1yr old (10kg) vomiting and diarrhea X 4 days
 Lethargic, limp, cold, weak rapid pulse, normal BP, sunken eyes, dry
eyes, parched mucous membranes, cap refill 5 sec, marked tenting of
skin
 Na = 115, K+ = 3.2, HC03 = 20
 What fluid and what rate would you use for the first 24hrs? Minimal
ongoing losses.
 How would your management change if the child seizes?
CASE #3:
 1yr old (10kg) vomiting and diarrhea X 4 days
 Lethargic, limp, cold, weak rapid pulse, normal BP, sunken eyes, dry
eyes, parched mucous membranes, cap refill 5 sec, marked tenting of
skin
 Na = 175, K+ = 3.2, HC03 = 20
 What fluid and what rate would you use for the first 24hrs? Minimal
ongoing losses.
CASE #1: ISONATREMIC
DEHYDRATION
PHASE I (initial resuscitation)

9.  iv access +/- bolus
PHASE II (0 - 8hrs)
 Fluid = D5W 0.45% normal saline (D51/2NS)
 Add 20 mEq/Kcl after urine output, renal function
established
 Deficit (moderate dehydration) = 10% X 10kg = 1000cc
 Rate cc/hr
(½ deficit - bolus) + (maintenanceX8hrs) + ongoing losses
8 hrs
(500 cc - 0) + (40cc/hr X 8hrs) + ongoing losses
8 hrs
500 + 320 + 0 = 102 cc/hr
8 hrs
PHASE III (8 - 24hr)
 Fluid = D5W0.45% normal saline + 20mEq Kcl/L
 Rate cc/hr
(½ deficit) + (maintenance X 16hrs) + ongoing losses
16hrs
(500cc) + (40cc X 16) + 0 = 71 cc/hr
16hrs
CASE #1: ISONATREMIC
DEHYDRATION
 Most common form
 Na between 130 - 150

10.  Roughly equal losses of Na and water
 NO change in body tonicity or redistribution of fluid between intra and
extravascular spaces
CASE #2: HYPONATREMIC
DEHYDRATION
PHASE I
 iv access + bolus 20cc/kg NS
PHASE II
 NOT seizing
 Fluid = D5W0.45% normal saline + 20 mEq Kcl/L
 Deficit (severe dehydration) = 15% X 10kg = 1500ml
 Rate =
(½ deficit - bolus) + (maintenanceX8hrs) + ongoing losses
8 hrs
(750cc - 200cc) + (40cc/hrX8hr) + 0 = 108 cc/hr
8hrs
 Seizing
 Fluid = 3% saline bolus
 Followed by D5W0.45%NS + Kcl at same rate as
above
 Na deficit = (desired - current Na) X %TBW X weight
 Na deficit = (120 - 115mEq) X 0.5 X 10kg = 25 mEq
 3% normal saline is 513 mEq/l or 0.5 mEq/ml
 Thus bolus 50 ml
 Rule of thumb: 2.5 ml/kg of 3% NS to increase Na by
5mEq/L
 PHASE III
 Fluid = DW50.45% normal saline + 20 mEq Kcl/L
 Rate =
(½ deficit) + (maintenance X 16hrs) + ongoing losses
16hrs

11. (750cc) + (40cc/hrX16) +0 = 87 cc/hr
16
CASE #2: HYPONATREMIC
DEHYDRATION
 Na < 130
 Sodium loss > water loss + poor sodium replacement
 Cerebral edema: seizures, come
 Hypo-osmolar demylination syndrome
 Most commonly seen as central pontine myelinolysis
 Pathophysiology unknown.
 Thought to be due to rapid correction in chronic hyponatremia.
 Neurological findings include fluctuating LOC, behavioral
disturbances, convulsions progressing to pseudobulbar palsy and
quadraparesis.
 ? Incidence --------> many case reports in literature
CASE #3:HYPERNATREMIC
DEHYDRATION
PHASE I
 Bolus of NS 20cc/kg
PHASE II/III
 Fluid = D5W 0.45% NS or D5W0.2%NS
 Deficit (severe dehydration) = 15% X 10kg = 1500ml
 Rate cc/hr =
(½ deficit - bolus) + (maintenanceX24hrs) + ongoing losses
24hours
(750cc - 200cc) + (1000cc)+ 0 = 65 cc/hr
24 hours

12. CASE #3:HYPERNATREMIC
DEHYDRATION
 Na > 150
 Water loss > Na loss
 Correct slowly over 48 hours
 Risk: seizures, coma, death
 Rapid correction ------> CEREBRAL EDEMA
 Hypernatremia: fluid shifts out of cells
 Idiogenic osmols (glycine, taurine) prevent water loss from cells
 Rapid correction ------> idogenic osmols attract water into cells --->
cerebral edema
SPECIAL CONSIDERATIONS
ACIDOSIS
 Lactic acidosis, ketoacidosis, bicarbonate loss
 Corrects itself with rehydration
 Respiratory compensation
 Forget bicarbonate unless severe pH < 7.0 (?)
REPLACE DEFICIT
OVER 48 HOURS IN
HYPERNATREMIC
DEHYDRATION

13.  HC03 deficit = (20 - measured) X 0.6 X weight
 Remember K+ shifts and paradoxical CSF acidosis (C02 crosses BBB better
than HC03)
POTASSIUM
 Ensure adequate urine output before replacement
 Watch closely with renal failure
 20 - max of 60 mEq Kcl/L in peripheral iv
ORAL REHYDRATION THERAPY
CONTRAINDICATIONS
 Severe dehydration, acute abdomen, intestinal obstruction, underlying relevant
medical illnesses
FAILURE
 Circulatory collapse, Increasing deficit despite ORT, deterioration during ORT,
intractable vomiting, failure to rehydrate in 8hrs
TECHNIQUE
 Rehydrate in ED over 4hrs, reassess and d/c home or continue and reassess at
8hrs
 Solutions: see table
 Target volumes
 mild = 60 ml/kg, moderate = 80 ml/kg
 or: deficit + maintenance + ongoing losses
DISCUSSION
 Why is glucose needed?
 NG vs oral vs iv rehydration?
 “Nothing will stay down”
 IV bolus and discharge home