Assessing Fluid State - Paediatrics Emergency Management

Emergency Management

Assessing Fluid State

Assessing Vital Signs

·        Rate is always subservient to quality:

o  Thready pulse: eg palpable at neck and groin only

o  Respiration: more important that rate are grunting, flaring, subcostal retraction, use of accessory muscles (in neonate ® bobbing of head)

·        Blood volume:

·        Neonate  90 ml/kg

·        Child         80 ml/kg

·        Adult        70 ml/kg

o  In a trauma situation, guess the weight: (age + 4) * 2

·        Urine output:

o  In nappies: 2 ml/kg/hr

o  Toilet trained: 1 ml/kg/hr

·        Normal fluid requirements in absence of sweating:

·        Nutrition: to maintain weight need 75 calories/kg/day

·        Heat loss:

o   70 kg person: surface to mass ratio is 0.02

o   2 kg person: surface to mass ratio is 0.08 

o   Rate of heat loss is proportional to (body temp – room temp) to the power of 4. Best way to maintain body heat is therefore to heat the room.

Assessing fluid loss

·        Only reliable indicator is pulse.  BP doesn‟t drop till severe dehydration (compared with adult where

·        BP declines proportionately with losses)

·        No physical signs until > 3% loss

·        Most signs of dehydration are those of shock

·        Change in body weight is the most accurate estimate of fluid loss – but is rarely available

·        Dehydration in obese children is often under-estimated

·        Nutrition: to maintain weight need 75 calories/kg/day

·        Heat loss:

o   70 kg person: surface to mass ratio is 0.02

o   2 kg person: surface to mass ratio is 0.08 

o   Rate of heat loss is proportional to (body temp – room temp) to the power of 4. Best way to maintain body heat is therefore to heat the room.

Assessing fluid loss

·        Only reliable indicator is pulse.  BP doesn‟t drop till severe dehydration (compared with adult where

·        BP declines proportionately with losses)

·        No physical signs until > 3% loss

·        Most signs of dehydration are those of shock

·        Change in body weight is the most accurate estimate of fluid loss – but is rarely available

·        Dehydration in obese children is often under-estimated

·        Assessing turgor: pinched edge of skin goes down slowly.  Do centrally on abdomen, chest, thighs

·        Also when severe: rapid, sighing respirations (Kussmaul breathing) 

·        Poor predictors of dehydration: Sunken eyes or anterior fontanelle, dry mucous membranes, absence of sweat or tears

Management of Non-Dehydrated Child

·        If no or infrequent vomiting that is not interfering with fluid intake then 5 – 7 ml/kg/hour of:

o   Breast milk

o   ½ strength formula

o   Fruit juice 1 part in 4 with water

·        After 6 – 12 hours introduce: bananas, rice, potato, parsnips, pumpkin, dry biscuits/toast with vegemite

Management of Mild-Moderate Dehydration

·        Admit or observe in a short stay facility for several hours

·        Don‟t use homemade solutions – use Gastrolyte

·        Orally, of by NG tube if necessary: 

o   Replace calculated losses over 6 hours (don‟t worry about maintenance requirements). Hourly observations and reassess and reweigh after 6 hours

o   Give the remainder of the daily fluid maintenance over the next 18 hours

·        Resume breast feeding as soon as rehydration is complete or sooner if this takes longer than 6-hours

·        If after 4 – 6 hours the child remains dehydrated, then IV

Management of Severe Rehydration

·        WEIGH THE CHILD to assess progress

·        3 stages: 

o   Initial bolus if necessary. 10 - 20 ml/kg of Ringers Lactate or normal saline over 10 – 15 minutes, reassess and repeat if necessary

o   Replacement + maintenance

o   Maintenance only

·        Rehydration of isotonic dehydration:

o   Replacement: Normal saline (or Ringer‟s Lactate or Hartmanns – more physiological)

o   Maintenance: 1/5^th normal saline + 5% Dextrose + 20 mmol/l KCl [Barts] (gives a bit much Cl but the kidneys can sort that)

o  If initially shocked, do not add KCl until urine is passed. If they have ATN following shock (® renal failure) don‟t want to overload K 

·        Timing: 

o  Infuse replacement fluid over 24 hours with the first 24 hours of maintenance using ongoing replacement: ½ normal saline + 2.5% dextrose + 10 mmol KCL (in 500 ml)

o  Monitor electrolytes before, and during, up to 6 hourly

o  Once they are able to tolerate oral fluids, treat as for mild/moderate dehydration

·        Theme and variations:

o  Diarrhoea:

§  Lost Na, HCO₃, Cl and K from GI mucosal cells – replace slowly

§  Resuscitation with bolus of crystalloids, eg Ringer‟s lactate, normal saline

§  Maintenance with: ½ normal saline + 2.5% dextrose + 20 mmol/L KCL

§  If persistent acidosis due to HCO₃ loss or lactic acidosis then add in HCO₃

o  Rehydration of hypernatraemic dehydration (eg serum Na > 150): 

§  Often the result of administering hyper-osmolar fluids (eg sports drinks) with vomiting and diarrhoea ® greater water loss due to water sucked into GI from circulation then vomited/passed 

§  Will be more dehydrated than they appear due to fluid shifts from ICF ® ECF

§  If shocked give 10 ml/kg boluses of normal saline until circulation restored

§  Calculate deficit

§  Calculate ongoing requirements over 48 hours

§  Give both over 48 hours – serum sodium should not fall faster than 0.5 mmol/hr

§  If oral rehydration, replacement is over 24 hours

o  Diabetic ketoacidosis: 

§  If give insulin too fast, serum glucose will drop quickly ® rapid change in ECF osmolality ® cerebral oedema 

§  If giving hypotonic solution then ­cerebral oedema – go slow

o  Rehydration of hyponatraemic dehydration (serum Na < 130):

§  Resulting from gut or renal losses, or excessive hypotonic fluid administration 

§  Appear more dehydrated than they are as fluid shifts into the ICF. Can ® cerebral oedema, seizures, etc 

§  Never give 1/5^th normal saline (except to keep vein open).  Do serial Na measurements

§  If asymptomatic: As for rehydration of isotonic dehydration, over 24 hours. Fluid restrict to 50% of maintenance 

§  If symptomatic (seizures, coma) or if severe (Na < 120) then give 5 – 10 ml/kg or 3% hypertonic saline IV over 60 – 120 minutes in addition to the calculated fluid requirements

·        Notes:

o  Be careful about measuring volume: never hang a bag straight into a child 

o  If lung or brain disease (eg meningitis), SIADH is common Þ may need to fluid restrict (eg to 50% maintenance fluids). Check serum Na regularly 

o  In a term baby, born water logged (ECF > ICF). Can pass 500 ml urine per day (7 ml/kg/hour). Handles water well but not used to passing a NaCl load

o  Enemas for constipation can ® dehydration