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Fluids And dehydration

Fluids And dehydration. University of Nevada School of Medicine Department of Pediatrics. Objectives. Discuss maintenance fluid in children and why it is needed Discuss dehydration Isotonic, hypotonic, hypertonic Go over some brief examples of each Practice doing fluid calculations.

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Fluids And dehydration

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  1. FluidsAnd dehydration University of Nevada School of Medicine Department of Pediatrics

  2. Objectives • Discuss maintenance fluid in children and why it is needed • Discuss dehydration • Isotonic, hypotonic, hypertonic • Go over some brief examples of each • Practice doing fluid calculations

  3. Things you’ll need to know • Deficit • How much is the deficit • What kind of loss was there • Boluses • Maintenance rate • Ongoing losses • Electrolyte maintenance/imbalance • Isotonic, hypotonic, hypertonic

  4. Maintenance • What determines maintenance? • Urine • Insensible losses • Stool • Respiration • Skin • Intrinsic loss • By-product of metabolism • Kidney function • Anuria/oliguria • What makes kids different? • Higher metabolic rate and evaporative loss

  5. Maintenance cont • How can you estimate maintenance fluids? • Based on metabolic demand • Different formulas • Total body surface area (meter squared) • Requires weight , height and table • Basal metabolic rate • Also requires table, “drier” of the two methods • Holliday-Segar method • Easy but does not account for individual demands

  6. Holliday-Segar Method

  7. Rapid Fire Question • Interns only • What is the maintenance rate, using the Holliday-Segar method, of a child that is 75 kg?

  8. Rapid Fire Question • 115 mL/hr

  9. Insensible losses • Factors affecting insensible losses • Respiratory rate • Age • Pain • Ventilator • Environmental temperature • Phototherapy • Skin defects • Burns • Bullous congenital icthyosiform erythroderma

  10. Respiratory rates HazinskiMF. Anatomic and physiologic differences between children and adults.

  11. Boluses • How do we rehydrate a child who is mildly dehydrated? • Most of the time if they are able to tolerate PO intake, then oral rehydration is recommended • How do we bolus a child who is moderately to severely dehydrated? • Give NS bolus of 20 mL/kg • Can use LR as well, both are isotonic • Speed of infusion depends on state of patient • May repeat if necessary • Frequent reexaminations important

  12. Dehydration/deficit • Causes of dehydration? • Inadequate intake • Sweat/heat • Increased urination • Increased respiratory rate • Vomiting/diarrhea • Blood loss • Fever • Catabolic state • Extra solutes, need extra fluid in order to excrete • Usually, only a one time calculation

  13. Dehydration/deficit cont • What is the most accurate method to determine acute weight loss? • Recent weight change from measured source • Usually difficult to obtain acutely • Otherwise clinical judgment must be made • Expressed as percent body weight

  14. Clinical Signs • What are some signs of dehydration? • Sunken fontanel – babies • Weight loss • Thirst • Decreased skin turgor • Dry mucous membranes • Lack of tears • Decreased urine output • Increased urine specific gravity • Increased heart rate • Decreased blood pressure

  15. Clinical Assessment of Dehydration Pediatr. Rev. 2001;22;380-387

  16. Calculating Deficit • % Dehydration = PIW (kg) – IW (kg) x 100% PIW (kg) PIW = Pre-illness weight IW = Illness weight • Clinically • Take % dehydration x 10 x weight • Example • 10 kg child is 5% dehydrated • 0.05 x 1000mL/kg x 10kg = 500 mL deficit • 50 ml/kg x 10 kg = 500 mL deficit

  17. Rapid Fire Question • Second Years Only • A 13 year old male weighing 45 kilograms is moderately dehydrated. What is his approximate total fluid deficit (TFD)?

  18. Rapid Fire Answer • 2.7 liters or 2700 mL • 60 mL/kg x 45 kg = 2.7 L • Bonus Question • The patient got a 20 mL/kg bolus, what would his deficit be then? • 1.8 liters or 1800 mL

  19. Ongoing Losses • Abnormal losses occurring after the initial deficit is replaced/calculated • Some measurable losses • Vomiting/diarrhea • Urine/polyuria • Non-measurable losses • Also take into effect the loss of electrolytes as well

  20. Rapid Fire Question/Answer • What are some other causes of measurable losses besides urine, vomiting, and diarrhea? • Chest tube • CSF drainage • NG/GT output • Ostomy output

  21. Rapid Fire Question/Answer • Third Years Only • What are some non-measurable losses besides sweat and breathing? • Ileus • Peritonitis • 3rd spacing

  22. Ongoing Losses cont • Most ongoing losses are of GI in nature • ½ NS is usually sufficient for replacement • Measurable losses should be monitored • If consistent, then can be added to maintenance • If sporadic then they can be added up and then replaced every 4-12 hours as needed

  23. Electrolyte Maintenance Requirements • What are the daily requirements for Na and K? • Sodium • 3 meq/100 mL or 30 meq/L • Potassium • 2 meq/100 mL or 20 meq/L

  24. Figuring Out Ions • Example for Na • 20 kg child needs maintenance fluids only • Using the Holliday-Segar method then 30 meq/L needed • Technically speaking that is why ¼ is closest to physiologic • You still need to understand how much Na/K you need in a day • Maintenance fluid is 60 mL/hr x24 hrs = 1440 mL • Na = 1.44 L x 30 meq/L = 43.2 meq/day

  25. Rapid Fire Question • How much sodium would a 12 year old girl, weighing 54 kg, need in a day accounting for maintenance only?

  26. Rapid Fire Answer • 67.7 meq Na per day • Maintenance = 94 mL/hr • 94 mL/hr x 24 hours = 2.256 L • 2.256 L x 30 meq/L = 67.7

  27. Figuring Out Ions cont • Example for K • 20 kg child needs maintenance fluids only • Maintenance fluid is 60 mL/hr x 24 hrs = 1.44 L • Using 20 meq/L x 1.44 L = 28.8 meq/day • Whenever using the Holliday-Segar method then 20 meq/L of KCl is all that is needed for most maintenance calculations • But having that number will help later if you are doing more than just calculating maintenance

  28. Step Wise Fashion for Dehydration • Figure out maintenance • Determine level of dehydration/fluid deficit • Subtract any boluses given • Determine electrolyte needs • 1st in maintenance • 2nd in loss of fluids and added in boluses • 3rd need for balance in hypernatremic/hyponatremic dehydration • Put all of the steps together

  29. Isotonic Dehydration • By definition no need to rebalance Na • Therefore only need to figure out maintenance and loss from dehydration • For the most part D5 ½ NS is usually sufficient

  30. Example • 10 kg child who is 10% dehydrated, got one 20 mL/kg bolus • Boluses have sodium • Also think of the Na that is lost from dehydration • Normal Na concentration in blood is 140 and fluid coefficient is 0.6 • TFD Na = fluid loss (L) x 0.6 x 140 • Remaining deficit = Deficit – Bolus • In 1st 8 hours = (½ Remaining deficit/8) + Maintenance • Next 16 hours = (½ Remaining deficit/16) + Maintenance

  31. Isonatremic Final Answer • Most K is intracellular • Usually acute dehydration, less than 3 days does not affect K concentration • Takes time to move into the serum • Therefore you can assume that K replacement would just consist of maintenance or around 20 meq/L • 960 mL x 2 meq/100 mL = 19.2 meq K • 19.2 meq K / 1.76 L = 10.9 meq/L • D5 1/3 NS with 10 meq KCl @ 90 mL/hr x 8 hrs then 65 mL/hr x 16 hrs

  32. Severe Dehydration with K • After 3 days of dehydration or in severe circumstances then K loss should be determined • Take last example • Example of 10 kg with 10% dehydration • Maintenance K was 19.2 meq K/day • Fluid loss was 1 L • K loss = Intracellular conc x 0.4 (coeff) x TFD • K = 150 x 0.4 x 1 L = 60 meq • Total K = 60 + 19.2 = 80 meq • Conc K = 80 meq / 1.76 L = 45 meq/L • YOU NEVER USE MORE THAN 40 meq/L through an IV

  33. Practice Question • An 8 month old comes to the ER with vomiting and diarrhea for the last 2 days and has the following: • T 102.2, HR 165, BP 60/45, RR 30, Wt 9 kg • Sunken eyes, no tears, lethargy, CR > 5 secs • He is given total boluses of NS of 30 mL/kg • Calculating for dehydration, what would be the approximate FLUID RATES for the next 24 HOURS, for this child?

  34. Practice Answer • 100 mL/hr (103) for the first 8 hours then 70 mL/hr for the next 16 hours • Maintenance = 9 x 4 = 36 mL/hr • Severe dehydration = 15% or 150 mL/kg • TFD = 150 mL/kg x 9 kg = 1.35 L • Bolus = 30 mL/kg x 9 kg = 0.270 L • Deficit = 1350 mL – 270 mL = 1080 mL • 1st 8 hrs = 1080/8/2 + 36 mL/hr = 103 • 2nd 16 hrs = 1080/16/2 + 36 mL/hr = 70

  35. Rapid Fire Question/Answers • What are some signs of hypernatremic dehydration? • Doughy skin* • Anorexia • Restlessness • Nausea, vomiting • Lethargy, irritability, eventually, stupor or coma • Twitching, hyper-reflexia, ataxia, or tremor*

  36. Rapid Fire Question • What is the main concern for decreasing the sodium too quickly in a patient with longstanding hypernatremia?

  37. Rapid Fire Answer • Cerebral Edema

  38. Hypernatremic Dehydration • Excess of Na compared to free water • Should replace deficit over 24-48 hours • Goal is to decrease 0.5-1 meq/L/hr in acute, 0.5 in chronic dehydration • Free water = (Measured Na – 145)x(4mL/kg)x(wt) • 4 mL/kg is the amount of water to account for 1 unit increase of sodium • Example • 10 kg child with Na of 160, 10% dehydration, no bolus given • (160-145) x 4 mL/kg x 10 kg = 600 mL

  39. Hypernatremic Final Answer • D5 1/4 NS • Less than 3 days K part • 960 mL x 2 meq/100 mL = 19.2 meq K • 19.2 meq K / 1.66 L = 12 meq/L for 1st 24 hours • 19.2 meq K / 1.26 L = 15 meq/L for 2nd24 hours • Longer than 3 days K part • Solute Fluid Deficit • 0.4L * 150 *0.4 = 24 meq/L • 24 + 19.2 = 43 meq/L • 43/1.66L = 25 meq /L • D5 1/4 NS + 10 (25) meq/L KCl @ 70 mL/hr x 24 hours then D5 ¼ NS + 15 meq/L KCl @ 50 mL for the next 24 hours

  40. Practice Question • A 15 year old child with severe CP comes in after having poor PO and mild vomiting for the last 2 days. Workup shows a severely dehydrated child. Skin is doughy and he has poor pulses. • Na is 160 • Wt is 40 kg • No boluses are given • What is Total Fluid Deficit (TFD), Solute Fluid Deficit (SFD), and Free Water Deficit (FWD)?

  41. Practice Answer • TFD = 40 kg x 90mL/kg = 3600 mL • FWD = (160 – 145) x 40 kg x 4 ml/kg = 2400 mL • SFD = 3600 – 2400 = 1200 mL • Bonus Question • How much sodium in meq would he need in addition to his maintenance sodium? • 1.2 L x 140 x 0.6 = 100 meq

  42. Rapid Fire Question/Answers • What are the signs of hyponatremic dehydration? • Anorexia • Agitation, confusion, headaches, dizziness • Lethargy • Nausea and vomiting • Muscle cramps* • Neurological deficits, seizures*, comas • Poor skin turgor

  43. Rapid Fire Question • What is the main concern for increasing the sodium too quickly in a patient with longstanding hyponatremia?

  44. Rapid Fire Answer • Central pontine myelinolysis

  45. Hyponatremic Dehydration • Need to figure out Na deficit • Na deficit = (135 - Measured Na )x(0.6)x(wt) • 0.6 is the Df (% co-efficient) of Na in ECF • This is in addition to the Na from fluid loss due to dehydration • Example • 10 kg child with Na of 120, 10% dehydration, 20 mL/kg bolus was given • (135-120) x 0.6 x 10 kg = 90 meq Na

  46. Hyponatremic Final Answer • D5 ½ NS with 10 meq KCl @ 70 mL/hr x 24 hrs • Goal is to increase Na by no more than 0.5-1 meq/L/hr • Recheck Na frequently and adjust sodium concentration if necessary

  47. Practice Question • A 15 year old football player comes into the ER after collapsing during football practice. He is moderately dehydrated. • Na is 118 • Wt is 75 kg • No boluses are given in the ER • How much sodium does he need because he is hyponatremic, not accounting for his maintenance or dehydration?

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