Fluids, Electrolytes and Dehydration by eib63834

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									                          Fluids, Electrolytes and Dehydration

Objectives
 Briefly discuss basic etiologies of dehydration
 Explanation of various states of dehydration
 How to clinically determine states of hydration
 Discussion of treatment
 Understanding the how and why

Vomiting
Overview:
 forceful ejection of gastric contents as opposed to passive reflux
 most common cause is gastroenteritis
 in infants consider gastroesophageal reflux, overfeeding, anatomic obstruction, and
  systemic infection

Evaluation
History:
 assess pattern and severity as well as accompanying dehydration/malnutrition
 if neonatal, consider congenital abnormalities such as duodenal or esophageal atresia,
  Hirschsprung's disease, volvulus, malformation

 in infants, assess how much is being fed
      overfeeding

 relation to position
      reflux

 choking or coughing with feeding
      achalasia, tracheosophageal fistula

Treatment
 oral rehydration vs IV hydration
 consider antiemetics such as Zofran (Ondansetron) >3 y/o 0.15 mg/kg
 >4 y/o 4mg

Diarrhea
 numerous causes of acute and chronic diarrhea
 infectious causes include:
    viruses (rotavirus most common)
    bacteria (Salmonella, Shigella, Campylobacter most common)
    parasites (Giardia and Cryptosporidium most common)
    antibiotic-associated (antibiotic side effect as well as Clostridium difficile)
 Noninfectious

     overfeeding (particularly of fruit juices)
     irritable bowel syndrome
     celiac disease
     milk protein intolerance
     lactose intolerance post infectious diarrhea
     cystic fibrosis
     inflammatory bowel disease

Evaluation
History:
 acute versus chronic
 volume, frequency, character of stools, presence of blood or mucus
 associated symptoms (vomiting, fever, malaise, etc.)
 epidemiologic data (travel, day care, family history)

Exam
 estimate dehydration (Table 1)
 examine for other infectious process or source
 determine if nutritional status is compromised
 neurologic symptoms, mental status changes or seizures, suggest Shigella or Rotavirus

   evaluate state of hydration (Table 1)
   look for site of infection
   abdominal and rectal exam for obstruction or imperforate anus
   radiologic studies as indicated
   if child less than 2 months, consider ultrasonography for pyloric stenosis

Lab tests
 culture indicated for acute bloody diarrhea
 fecal leukocytes and RBCs not sensitive or specific enough to be useful except to
  suggest need for further work- up
 ELISA test is available for Rotavirus (Rotazyme)
 O&P for prolonged diarrhea or as indicated
 studies for chronic disease as appropriate

Treatment
 acute diarrhea with dehydration in the absence of vomiting is treated with large
   amounts of osmotically balanced clear liquids until rehydration is complete
 abundant evidence that early reinstitution of a lactose-free general diet will decrease
   the duration and severity of diarrhea
 foods provided should be the same as those in the child's normal diet with the
   exclusion of:
     high-sugar foods such as apple juice, which may cause an osmotic diarrhea
     milk products with lactose
 avoid the use of antiperistaltic agents in infants and children

 most episodes of diarrhea do not benefit from antimicrobial therapy
 bacterial diarrhea should be treated appropriately after culture results are available

 caution should be used in the treatment of diarrhea caused by Salmonella species
  because this may prolong the carrier state
    however, antibiotics should be used for Salmonella in infants < 3 months old
 diarrhea with vomiting is treated as for vomiting until patient is able to tolerate oral
  feedings

Clinical Assessment
 clinical observation
 clinical signs and symptoms are neither sensitive nor specific

Sodium, Chloride & Water Balance
 2% water loss or increased plasma osmolality stimulates thirst
 osmoreceptor in hypothalamus sense ‘dry or thick’ conditions
 ADH released
 decreased blood volume and BP also stimulates ADH release
 what is the other name for ADH?
    Vasopressin

Oral Rehydration
 there is no role for weak tea, flat soda, Jell-O (gelatin), water, etc
 concept of "gut rest," (stopping oral intake for several hours before refeeding) has been
  found to have several negative effects
 studies have shown that stool production is actually less with rapid re- feeding

 oral rehydration is appropriate in most cases of mild to moderate dehydration
 currently only two fluids meet the recommendations of the World Health Organization
   (WHO) and the American Academy of Pediatrics

 Rehydralyte (Ross) and the WHO-ORS product (oral rehydration solution)
     these are the only two products that contain the 75 to 90 mEq/L of sodium
      recommended for rehydration

 oral rehydration should be accomplished over 4 hours
 the dose for mild dehydration is 50 cc/kg, or 100 cc/kg for moderate dehydration
 if vomiting is occurring, the child may be given frequent small doses of the
   rehydration fluid and then subsequent maintenance fluids by using a teaspoon or a
   small oral syringe to provide a rate of approximately 5 cc/min

other solutions such as:
 weak tea
 dilute or full- strength soft drinks
 Jell-O (gelatin)
 water
 tap water
 apple juice
contraindicated and may lead to hyponatremia

General Principles in Treating Dehydration
 weigh the child
 be sure to add ongoing losses to maintenance + deficit fluids and electrolytes
 if moderately or severely dehydrated, give an initial fluid bolus of 20 ml/kg LR or NS
  over 20 minutes
 repeat bolus if response is inadequate

 if poor response after three fluid boluses, that is, poor perfusion, no urine output,
    abnormal vital signs, may need CVP or PCWP

Intravenous Rehydration
Maintenance requirements for fluids:
   Weight <10 kg:           100 ml/kg/day
   Weight 11 to 20 kg:      1000 ml + 50 ml/kg/day
                                     for every kg over 10 kg
   Weight >20 kg:           1500 ml + 20 ml/kg/day
                                     for every kg over 20 kg
   Adult:                   2000 to 2400 ml/day

 do not add potassium to IV line until urine output established
 diabetic ketoacidosis is an exception, where correction of hyperglycemia and acidosis
  may lead to rapid development of hypokalemia
 increase maintenance fluids by 12% for each Celsius degree of fever

Formulas: Calculating Electrolyte Deficits
 Sodium deficit (mEq total) = (135 [or Desired serum sodium] - Current serum sodium)
  x 0.6 x Weight (kg)
 Potassium deficit (mEq total) = (Desired serum K [mEq/liter] - Measured serum K) x
  0.25 x Weight (kg)
 Chloride deficit (mEq total) = (Desired serum chloride [mEq/liter] - Measured serum
  Cl) x 0.45 x Weight (kg)

Total body water:
    60% of body weight (70%)
 Correction of free water deficit in hypernatremic dehydration:
    free water deficit = 4 ml/kg for every mEq that the serum Na exceeds 145 mEq/L

Replacement of ongoing losses
 NG losses usually replaced with D5 1/2 NS with 20 mEq/L of KCl
 diarrhea usually replaced with D5 1/4 NS with 40 mEq/L of KCl
Clinical Signs Associated With Stages of Dehydration
Table 1
Dehydration (%)         Clinical Observation
    5-6                   -HR 10%-15% above baseline
                         -slightly dry mucous membranes
                         -concentration of urine
                         -poor tear production

    7% - 8%       -Increased severity of above
                       -decreased skin turgor
                       -oliguria
                       -sunken eyeballs
                       -sunken anterior fontanelle

   >9%              -Pronounced severity of above signs
                       -Decreased blood pressure
                       -Delayed capillary refill (>2 sec)
                       -Acidosis (large base deficit)

Hypotonic Dehydration
(Na <125 mEq/l)
 symptomatic earlier than in isotonic or hypertonic dehydration
 lethargy and irritability are common, and vascular collapse can occur early
 therefore use weight loss of 3% = mild, 6% = moderate, and 9% = severe dehydration
 usually results from replacing losses (vomiting and diarrhea) with low-solute fluids,
  such as dilute juice, cola, weak tea

Therapy
 calculate total fluid and electrolyte needs according to the maintenance and deficit
  replacement formulas
 do not try to raise serum Na in more than 10 mEq/L increments (that is, if the current
  serum sodium is 125, use 135 as the desired serum Na level in the calculation)

 usually D5 1/2NS or D5 NS is used
 potassium can be added after urine output is established
 give half of the calculated total fluid and electrolyte requirements for the first 24 hours
  over the first 8 hours and the other half over the next 16 hours

 calculate the milliequivalents of Na needed in each liter during the first 24 hours of
  therapy
    mEq of Na per liter of IV fluid = total sodium needed in the first 24 hours divided
     by total volume of fluid needed. (Normal saline = 154 mEq of Na/liter
Isotonic Dehydration
(Na = 130 to 150 mEq/l)
 symptoms are less dramatic than in hypotonic dehydration
 use estimate (loss of weight) 5% = mild, 10% = moderate, 15% = severe dehydration
 calculate total maintenance + deficit replacement fluids and electrolytes for first 24
   hours

Therapy
 similar to treatment for hypotonic dehydration: give half of first 24 hours needs in first
  8 hours, and give the remaining half over the next 16 hours
 usually can use D5 1/4NS or D5 1/2NS
 may add potassium after urine output established
 remember to estimate and replace ongoing losses

Hypertonic Dehydration
(Na = >150meq/l)
 usually occurs as a result of using inappropriately high solute load as replacement
 renal concentrating defect with large free-water losses
 any large insensible losses
 typical symptoms include thick, doughy texture to skin (tenting is uncommon), shrill
  cry, weakness, tachypnea, intense thirst

 shock is a very late manifestation
 if severe dehydration or shock is present, the patient will need an initial fluid bolus of
  20 ml/kg NS over the first 20 to 30 minutes
 replace the free-water deficit slowly over 48 hours
 aim to decrease the serum sodium by about 10 mEq/L/day

 reducing serum sodium more rapidly can have severe repercussions, such as cerebral
  and pulmonary edema
 usual replacement fluid is D5 1/2NS or D5 NS
 if Na >180, may need dialysis

Hyponatremia
Clinical presentation of hyponatremia
 depends on severity and time course of onset
 rapidly developing hyponatremia is more symptomatic
 if plasma Na drops 10 mEq/L over several hours, patients may have nausea, vomiting,
   headache, muscle cramps

 mortality 50% if Na concentration falls to <113 mEq/L rapidly
 may have signs of the underlying illness (such as CHF, Addison's disease)
 if secondary to fluid loss, may have signs of shock including hypotension and
  tachycardia
Hyponatremia:
Clinical Manifestations
 cell unable to depolarize and repolarize
 lethargy
 headache
 confusion
 apprehension
 seizure & coma
 pure losses – sx of hypotension
 dilutional – sx of hypertension, wt. gain

Four Possible Etiologies
 artifactual or spurious
 dilutional
    hypervolemic w/ expansion of total body water
 hypovolemic
    sodium depletion in excess of water depletion
 euvolemic
    sodium & water depletion in equal amounts

       Artifactual or Spurious
lab reporting error secondary to:
 hyperglycemia
     correct sodium (each increase of blood glucose of 100 mg/dl decreases serum
       sodium by 1.7 mEq/L)
 hyperlipidemia


     Dilutional or Hypervolemic Hyponatremia
 caused by defect in water excretion
 clinical situation and underlying disease are key to cause
Diagnosis
 generally will manifest edema from underlying cause


      Hypovolemic Hyponatremia
Causes
 combined water and sodium loss
 GI loss such as vomiting, NG suction, diarrhea
 third-space losses as with burns, surgery
 excessive sweating
 uncontrolled diabetes mellitus
      Euvolemic Hyponatremia
Causes
 SIADH
 may also be caused by water intoxication but usually requires intake of >10 L/day,
  hypothyroidism, stress, adrenal insufficiency with a urine Na >20 mEq/L
 fluid restriction will be diagnostic

Hyponatremia: Clinical Lab Data
 decreased Serum Na+ <130meq/L
 decreased Chloride
 decreased Osmolality
 elevated Hematocrit & Plasma Proteins
 urine specific gravity < 1.010
Treatment for Hyponatremia
 treat underlying condition (CHF, Addison's disease, hypothyroidism, SIADH)
 correct a long-standing hyponatremia slowly and a rapidly developing hyponatremia
   more aggressively

Dilutional
 restrict Fluids
 diuretics


Sodium Loss
 replace Sodium & Fluids
 best – PO Solutions
 increased Na+ in diet
 IV Normal Saline


 do not rapidly overcorrect hyponatremia
    may precipitate central pontine myelinolysis

calculate: amount of Na needed to raise the serum Na to 135 mEq/L from 125 mEq/L in
   70 kg person

 sodium deficit (mEq total) = (135 [or Desired serum sodium] - Current serum sodium)
  x 0.6 x Weight (kg)
 amount of Na (mEq) = 135 mEq/L - 125 mEq/l x TBW (in liters)
 TBW = 0.6 x body weight in kg
 10 mEq/L x 42 L = 420 mEq Na deficit

   70 kg – maintenance fluids
   first 10 kg -      1000cc
   second 10 kg -      500cc
   50 kg x 20cc -     1000cc
                     2500cc
In that 2500cc you need to give 420meq Na
420meq         =      168meq
2500 cc               1000cc

SIADH
 may be caused by lung and other cancers, pulmonary (pneumonia, TB, contusion)
 CNS disorders including Guillain- Barre and subarachnoid hemorrhage
 multiple drugs
 isovolemic or hypervolemic without edema
 may not find inciting factor
 have normal GFR

Diagnosis
 have inappropriately hypertonic urine with respect to serum sodium
    urine osmolality should be <130 mOsm/kg if hyponatremic
    kidneys should be conserving sodium and getting rid of free water
 in SIADH, urine osmoles are >130 mOsm/kg)
 UA sodium is >10

Treatment for SIADH
 fluid restriction to 1 liter per day
 if this is unacceptable to patient, demeclocycline 3.25 to 3.75 mg/kg Q6h to
   antagonize the effect of ADH on the kidney may help
 use with caution in those with liver disease (because may cause liver fa ilure), CHF, or
   renal failure

Hypernatremia
Defined
 serum sodium above normal (generally > 145 mEq/L)
Causes
 occurs if hypotonic fluid losses are not adequately replaced
 may occur with hyperalimentation or other hypertonic fluid administration

Hypernatremia:
Clinical Manifestations
 Weakness, Restlessness, Delirium, Coma
 Flushed dry skin
 Intense thirst
 Fever
 Dry mucous membranes
 Decreased Tears
 Hyperactive DTR’s, Irritability, Muscular rigidity, Tremors
 Seizures  Respiratory arrest
Hypernatremia: Clinical Lab Data
 serum Sodium above 145-147 mEq/L
 serum Osmolality > 300mOsm/L
 normal to high Hematocrit
 urine Specific Gravity > 1.030

 urine osmolality less than or equal to that of the serum implies renal fluid losses
        diuretic therapy
        osmotic diuresis
        diabetes insipidus
        acute tubular necrosis
        postobstructive uropathy

Treatment
 hypernatremia with volume depletion should be treated by administration of isotonic
   saline until hemodynamic stability is achieved
 can then correct the remaining water deficit with D5W or hypotonic saline

 hypernatremia with volume excess is treated with diuresis or, if necessary, with
    dialysis
      can then correct the remaining water deficit with D5W or hypotonic saline

 one half the calculated water deficit should be given in the first 24 hours, and the
    remaining deficit is corrected over 1 or 2 days to avoid cerebral edema secondary to
    abrupt change in serum sodium concentration

Jeopardy
 What is the most reliable way to determine if patient is retaining fluid?

 If a patient gains 1 kg, or 2.2 lbs, how much fluid has he retained?

 Can a patient have edema yet be hypovolemic? Explain


 Vomiting - Diarrhea
 Dehydration - determining %
     IV vs po
   Maintenance and deficits
   Hypotonic / Hypertonic
   Hyponatremia – type of hypotonic
   Hypernatremia

								
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