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Fluids, Electrolytes and Dehydration

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Mike Burbridge

on 11 July 2014

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Transcript of Fluids, Electrolytes and Dehydration

Fluids and Electrolytes
What are maintenance fluids?
How does our body loose fluids?
How do we calculate metabolic rate?
What are our daily electrolyte requirements?
What type of fluids do I use?

Dehydration
How do we calculate fluid deficits?
How do we replace fluid deficits?
Ongoing losses.
Examples.
Maintenance Fluids
Fluid used up during basal metabolism
Sensible losses (50%)
urine
stool
Insensible losses (50%)
skin
respiratory tract
Maintenance Fluids
Metabolic rate determines fluid requirements
Holliday-Segar formula (aka 4:2:1 rule)
average DAILY fluid need for hospitalized patient
patients with markedly reduced activity will require less fluids
anuric patients will require only 50% of calculated fluids
does not include increased losses from fever, tachypnea, vomiting, diarrhea
Holliday-Segar Formula
Cumulative formula
Holliday-Segar Formula
5kg baby
15 kg toddler
Daily fluids = 100ml/kg + 50ml/kg
100ml x 10kg = 1000ml
plus, 50ml x 5kg = 250ml
Total 1250ml per day
Hourly fluids = 4ml/kg
4ml x 5kg = 20ml per hour
Daily fluids = 100ml/kg
100ml x 5 kg = 500 ml per day
Hourly Fluids = 4ml/kg + 2ml/kg
4ml x 10kg = 40ml
plus 2ml x 5kg = 10ml
Total = 50ml per hour
25 kg child
Daily fluids = 100ml/kg + 50ml/kg + 20ml/kg
100ml x 10kg = 1000ml
50ml x 10kg = 500ml
20ml x 5kg = 100ml
Total = 1600ml per day
Hourly fluids = 4ml/kg + 2ml/kg + 1ml/kg
4ml x 10kg = 40ml
2ml x 10kg = 20ml
1ml x 5 kg = 5ml
Total = 65ml per hour
Electrolytes
Virtually all electrolyte loss is urinary
Composition of IV Fluids
Fluid Na (mEq/L) K (mEq/L) Cl (mEq/L) HCO3 (mEq/L)
NS 154 154
1/2 NS 77 77
1/4 NS 34 34
LR 130 4 109 28
1/2 NS + 20mEq/l KCl
D5
ALWAYS NORMAL SALINE!
Bolus?
Weight (kg) Calories (=ml) per day Calories (=ml) per hour
0-10 KG 100 per KG 4 per KG
11-20 KG 50 per KG 2 per KG
>20 KG 20 per KG 1 per KG
Dehydration
Determine fluid deficit (% dehydration)
Fluid Deficit
Mild
Moderate
Severe
Mucous membranes
Skin
Tears
Urine output
Pulse
Blood pressure
Cap refill
Fontanelle/eyes
Mental Status
Infant/child 5%
Adol 3%
Infant/child 10%
Adol 6%
Infant/child 15%
Adol 9%
Moist
Dry
Cracked
Normal
Tenting
Clammy
Normal
Reduced
None
Normal
Increased
Max rate
"Less wet"
Oliguria
Anuria
Normal
2-3 sec
>3 sec
Normal
Normal
Decreased
Normal
Depressed
Sunken
Fussy but consolable
Irritable
Lethargic
Weight based (eg. today's weight - office weight prior to illness) = weight loss / pre -illness wt x 100
Clinical estimate
Normal urine Na loss is 30-35 mEq/L
Normal urine K loss is 20-25 mEq/L
Timing of fluid loss
Acute: less than 3 days (mostly extracellular)
Subacute: 3-7 days (both intra and extra cellular)
Chronic: >7 days (mostly intracellular)
Sodium is the Key
Hypotonic (Na <130) Isotonic (Na 130-150) Hypertonic (Na >150)
Na deficit
100mEq/L 80 mEq/l 20mEq/l
Hypotonic
usually
overestimates
degree of dehyrdation. ( oncotic pressure)
Hypertonic
usually
underestimates
degree of dehydration. ( oncotic pressure)
1/2 NS is appropriate for all types
Goal: change Na by 0.5-1 mEq per hour
Special Situations
Diabetic ketoacidosis (DKA)
total body potassium and phosphate deficit

Kphos +/- K acetate
Diarrhea
Bicarb loss in stool
K acetate
Profuse vomiting (pyloric stenosis)
Chloride loss w/metabolic alkalosis
KCl
SIADH
Low Na
without
dehydration
Fluid restriction
How do we replace fluid deficits?
Hippocrates: "Those bodies which have been slowly emaciated should be slowly recruited; and those which have been quickly emaciated should be quickly recruited."
Oral Rehydration Therapy (ORT)
IV Rehydration
Oral Rehydration Therapy
Recommended as FIRST LINE treatment by AAP and WHO for mild to moderate dehydration
Underused in the United States
Contraindications
Cardiovascular instability or shock
Suspected surgical abdomen
Severe hypernatremia
Available solutions:
WHO solution (2% dextrose, 90 mEq/l NaCl, 20 K)
Pedialyte (2.5% dextrose, 45 mEq/L NaCl, 20 K)
Gatorade (6% dextrose, 21 mEq/l NaCl, 2.5 K)
Apple Juice (12% dextrose, 0.4 mEq/l NaCl, 26K)
Oral Rehydration Therapy
Give PO or NG
Can replace entire deficit over 2-4 hours
Start with 1ml/min x 15-20 min then increase to 10-20ml/kg per hour x 4 hours (until deficit replaced)
Then resume regular PO feeds
Replace ongoing losses with 10ml/kg ORS for each diarrheal stool
Example: 5kg infant with 10% dehydration
Deficit: 1% = 10ml/kg
100ml x 5kg = 500ml deficit
WHO solution via NG
Start 60ml/hr x 15 min then increase to 125ml/hr x 4 hrs (total 515ml)
IV Rehydration
Joey, age 4, presents to ED with 3 days of vomiting and diarrhea. He has dry mucous membranes, poor skin turgor. Decreased urine output. Wt. 15kg.
HR 135, RR 16, BP 82/56, Sat 98% on RA
Na 132, K 4.5, Cl 90, CO2 18, BUN 16, Crt 0.4, Gluc 88
Lips dry but not cracked, cap refill 2-3 sec, lying in bed but obeys
1. First thing is to support circulation
give NS 20ml/kg over 30 min
2. Estmimate % dehydration
Moderate dehydration = 10% deficit
3. Replace deficit
4. Don't forget about maintenance fluids
5. Assess for ongoing losses
IV Rehydration
1. Give 300ml NS over 30 min.
(replaced 2% of deficit)
15kg, 10% dehydration
2. Remaining deficit = 8% or 80ml/kg
80ml x 15kg = 1200ml
3. Daily maintenance fluids
100ml x 10kg = 1000ml
+ 50ml x 5 kg = 250ml
Total = 1250ml
Combined Method
give 1/2 deficit + 1/3 maint over first 8 hours
give 1/2 deficit + 2/3 maint over next 16 hours
Sequential Method
replace deficit first at 10ml/kg/hr
give daily maintenance fluid over remaining time in 24 hrs (eg. 24-8=16 hrs)
IV Rehydration
15kg, 8% dehydration
Combined Method
Remaining deficit = 1200ml
Daily Maint = 1250ml
First 8 hours: 1/2 deficit + 1/3 maint
600ml + 417ml = 1017ml/8 hours
D5 1/2 NS + 20KCL @ 127 ml/hr x 8 hrs
Next 16 hours: 1/2 deficit + 2/3 maint
600ml + 833ml = 1433ml/16 hours
D5 1/2 NS + 20 KCl @ 90ml/hr x 16 hrs
Sequential Method
Replace deficit at 10ml/kg/hr
150ml/hr x 8 hours
D5 NS @ 150ml/hr x 8 hr
Give daily maintenance fluids over 16 hours
1250ml/16hrs = 78ml/hr
D5 1/2 NS + 20KCL @ 78ml/hr x 16hr
After 24 hours reassess hydration status and ongoing losses!
Ongoing losses
Measure what you can (stool in diapers)
Estimate what you must (emesis)
Approximate electrolyte losses
Dairrheal loss of bicarb and K+ (30-80mEq/L)
Biliary emesis loss of NaCl (120-140 mEq/L)
Burns loose NaCl as well
Replace ongoing losses ml for ml with appropriate fluid.
Diarrhea: replace stool output every 8 hours 1:1 with 1/2 NS + 40 mEq/L K acetate
Emesis: replace emesis every 8 hours 1:1 with NS + 20mEq/L KCl
This should run "piggy back" to maintenance fluids
Examples
8mo old female presents to the peds floor with 3 days of profuse diarrhea. Mom describes >12 watery stools in past 24 hours. She has not noticed any wet diapers in past 24 hours. Physical exam shows lethargic infant with sunken anterior fontanelle, cap refill5 sec. Wt. 8 kg.
HR 210, RR44, BP 68/40, Sats 94% on RA
Na 136, K 3.4, Cl 104, CO2 13, BUN 16, Crt0.6
15 % dehydration
Deficit: 150ml/kg = 1200ml
Maintenance = 100ml x 8kg = 800ml
First support circulation with NS bolus 20cc/kg, repeat as necesarry until HR and BP return to normal
She requires 2 NS boluses (40ml/kg) for BP and HR to normalize.
Combined Method
First 8 hours: 1/2 deficit + 1/3 maint
440ml + 267ml = 707ml / 8 hrs
D5 1/2 NS + 20 Kacetate @ 88ml/hr
remaining deficit = 880ml
Next 16 hours: 1/2 deficit + 2/3 maint
440ml + 533ml = 973ml / 16hr
D5 1/2 NS + 20 Kacetate @ 61ml/hr
Sequential Method
remaining deficit = 11%
Replace deficit: 1% per hour or 10ml/kg/hr
10 ml x 8kg = 80 ml/hr x 11 hrs
D5 NS @ 80ml/hr x 11 hrs
Daily maint over remaining time: 24-11=13 hr
800ml / 13 hr = 62ml/hr
D5 1/2 NS + 20 Kacetate @ 62ml/hr
*Don't forget to reassess for ongoing losses!
Examples
6 yo male presents to ED with vomiting and diarrhea x 3 days. He has only urinated once in past 24 hours. He is weak and tired but cooperative on exam. His eyes are somewhat depressed and his skin is dry. His cap refill is 2-3 sec. Wt. 25kg.
HR 160, RR 20, BP 90/58
Na 160, K 3.8, Cl 106, CO2 10, BUN 68, Crt 1.2
15% dehydration
Deficit: 150mg/kg = 3750ml
Daily Maint: 1600ml
First support circulation with NS bolus 20ml/kg over 30 min.
Sequential Method
Replace deficit: 1 %/hr = 10ml/kg/hr x 13 hours
10ml x 25 kg = 250ml/hr
D5 NS @ 250ml/hr x 13 hrs
Daily Maint fluids: 24hr - 13hr = 11hr
1600ml / 16hr = 145ml/hr
D5 1/2 NS + 20mEq/L @ 145ml/hr x 11hr
*Don't forget to reassess for ongoing losses!
Check Na q 6 hr. Goal is to decrease 0.5-1 mEq/hr.
Examples
6 wk old male presents to the your office with 2 weeks of vomiting. Mom says he can't keep anything down. He is not urinating very much, she can't remember when his last wet diaper was. On exam, he is thin, lips are cracked, anterior fontanelle is markedly sunken, skin is mottled and clammy. wt. 3.2kg
HR 190, RR50, BP 70/36, Sats 94% on RA
In ED, Na 128, K3.0, Cl 72, CO2 38, BUN 40, Crt 0.8
Abd US: pyloris is 4.5mm thick and 22mm long
15% Dehydration
Deficit: 150ml/kg = 480ml
Daily Maint: 320ml
Support circulation with NS bolus of 20ml/kg over 3 min.
Rehydration
Since child has been sick for >3 days, rehydrate slowly over 24 hours.
Total remaining deficit + daily fluids = (480ml - 64ml) + 320ml = 736ml /24 hr = 31ml/hr
D5 1/2 NS + 40 mEq/L KCl @ 31 ml/hr
Don't forget to reassess for ongoing losses!
Examples
15 mo female presents to your clinic with 2 days of vomiting and diarrhea. Mom is giving her 2 oz of pedialyte every hour but she keeps vomiting. She has 6-8 watery stools per day. She has a bad diaper rash. Mom says her wet diapers are not as wet as usual. Last wet diaper was just before they left home. On exam, she is fussy but consolable, her lips are moist, skin is normal, and cap refill is < 2 sec. Wt. 12kg
HR 128, RR 24, BP 82/64, Sats 98% on RA
5% Dehydration
Deficit: 50ml/kg = 600ml
Daily Maint: 1100ml
How are we going to rehydrate this child?
Oral Rehydration Therapy
WHO solution or pedialyte via syringe:
Start with 20ml syringe and give over 20 min in office.
Tell mom to repeat when she gets home and increase as tolerated until she is urinating normally
RTC in 1 day for recheck
If fails office oral rehydration, admit:
Place NG tube for ORT
Give Zofran PO or IV
Start WHO solution @ 60ml/hr x 15 min, then increase to 150 ml/hr x 4 hours. Decrease as needed for vomiting.
Resume regular diet and monitor closely.
Don't forget to reassess for ongoing losses!
Summary
Maintenance fluids are needed to replace normal fluid losses during basal metabolism.
Holliday- Segar formula approximates basal metabolic rate and therefore, daily fluid requirements for average hospitalized child. 100:50:20 or 4:2:1
Usual maintenance fluid on peds is D5 1/2 NS + 20mEq/L KCl
Estimate fluid deficit with current or recent weight or by clinical signs and symptoms.
First, support circulation with NS bolus.
Replace remaining deficit and daily maintenance fluids by preferred method.
Don't forget to assess for ongoing losses!
Fluids, Electrolytes, & Dehydration
Mike Burbridge, DO
Pediatric Hospitalist
VTCSOM

Dr. Dan
Dr. Top
Full transcript